Argos SpineNews 3


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Pour le compte d'une association internationale, prise en charge d'un journal, rédaction d'articles de vulgarisation scientifique, interviews, reportages photos dans les domaine de la chirurgie rachidienne et de la biomécanique.

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Argos SpineNews 3

  1. 1. October 2000 News from the world of Spinal surgery and biomechanics Focus on : Discover the world of nanotechnologies A new bipedicular implant Etienne-Jules Marey : the eye of biomechanic New trends in computer-assisted surgery Interview of Pr François Lavaste - Part 1 ENSAM Biomechanics Laboratory ENSAM Biomechanics Laboratory T H E O F F I C I A L A R G O S P U B L I C A T I O N
  2. 2. communication Interview of Professor François Lavaste - LBM Paris - Part 1 events Inaugural meeting of ARGOS Argentina Expo-Intermedica 7th seminar of spinal biomechanics, Poros Greece internet Web review science Discover the fantastic world of nanotechnologies evaluation : A new bipedicular implant technologies New trends in computer-assisted surgery history Etienne-Jules Marey : the eye of Biomechanics focus on The center for medical robotics and computer assisted surgery at UPMC Shadyside and Carnegie Mellon University Pittsburg USA clinical cases Degenerative spondylolisthesis associated with lumbar stenosis Lumbar canal stenosis and instability technologies Nobel Prize Winner, Pr Georges Charpak contribution to medicine 44 39 38 32 30 28 22 20 16 15 15 14 8 TTaabbllee ooff ccoonntteennttss October 2000 News from the world of Spinal surgery and biomechanics
  3. 3. For more information, see next page and get in touch with your local distributor. Centre Hospitalier de l’Université de Montréal 1560 Sherbrooke Est Str. Montreal (Qc) CANADA H2L 4M1 Phone (514) 281-6000 #8720 Laboratoire d’imagerie, de vision et d’intelligence artificielle (LIVIA) École de technologie supérieure 1100 Notre-dame West Str Montreal (Qc) CANADA H3C 1K3 Phone (514) 396-8800 #7675 Biomechanics - biomaterials research group École Polytechnique CP 6079 Succ. Centre-ville Montreal (Quebec) CANADA H3C 3A7 Phone (514) 3940-4711 #4198 Industrial collaborations : GERMANY : Telos CANADA : Arthrolab, BiOp, Orthomedic, Zimmer FRANCE : ARGOS, Eurosurgical, Ceraver USA : Sofamor Danek, Proctor and Gamble Funding : NSERC, FCAR, FREOM, FCI, FRSQ University collaborations : Biomechanics laboratory of ENSAM (Paris FRANCE) LIS3D & Hôpital St-Justine (CANADA), University of Bochum (GERMANY) Medical Imaging 2D/3D digital imaging processing, 3D models and reconstructions, low radiation multiplanar imagery Clinical studies Diagnostics, evaluation of prostheses and orthoses Medical Imaging 2D/3D digital imaging processing, 3D models and reconstructions, low radiation multiplanar imagery Clinical studies Diagnostics, evaluation of prostheses and orthoses Biomechanics Study and modeling of joint function, pathology, prosthetic replacement Biomechanics Study and modeling of joint function, pathology, prosthetic replacement The Montreal Imaging and Orthopaedics Research Laboratory Research center of CHUM Montreal Canada Circle4onReadingServiceCard
  4. 4. ( )EDITORIAL STAF Editor in chief Alexandre Templier, PhD Production/Art director Karim Boukarabila Board of editors the ARGOS committee Writer/Translator Patrick Bertranou, MD Blake W. Rodgers, MD Carl Stéphane Parent Philippe Strauss Alexandre Templier Assistant publisher Carl Stéphane Parent ARGOS COMITTEES Communication Committee : Patrick Bertranou, MD Philippe Bedat, MD Henri Costa, MD Pierre Kehr, MD Charles-Marc Laager, PhD Pierre Soete, MD Training Committee : Jean-Paul Steib, MD Jean-Paul Forthomme, MD Franck Gosset, MD François Lavaste, PhD Richard Terracher, MD Jean-Marc Vital, MD Evaluation Committee : Wafa Skalli, PhD Jacques De Guise, PhD Michel Dutoit, MD Alain Graftiaux, MD Henry Judet, MD Christian Mazel, MD Tony Martin, MD EDITORIAL HEADQUARTERS ARGOS 64, rue Tiquetonne 75002 Paris FRANCE Phone (33) 3 21 21 59 64 Fax (33) 3 21 21 59 70 ARGOS SpineNews circulation: over 7000 biannual issues by direct mailing to surgeons and spine professionals around the world. Advertising sales: Please contact Alexandre Templier at Fax +33 (0) 1 42 33 06 62 EEddiittoorriiaall October 2000 - N°2 ARGOS SpineNews 7 ARGOS Members and Friends, The first issue of ARGOS SpineNews attempted to respond to a growing need for communication within the international community of spinal surgeons, engineers, researchers, and business people. We hope to produce an orthopaedic journal for those working in spine-related technologies, as well as a reader-friendly research newsletter. The ARGOS Committees and we would like to thank you all for being so enthusiastic about this Journal. Now the train is on its way, and we will attempt to make the trip as pleasant as possible. If you have any requests or suggestions to improve this journal, please send it to our editorial headquarters. We will do our best to make this journal Yours. Before you start on this issue however, let us remind you that the 5th ARGOS International Symposium in Paris on January 26, 20001, will accept only 250 registrations. If you have ever attended this event you know that it has to keep its original size to preserve what makes it special, so please, don’t forget to register as soon as possible. If you have never attended, you definitely have to go! Open-minded collegial discussions of topics at the forefront of clinical practice and laboratory research in a friendly atmosphere are not so frequent these days… So come and join us as we expand the Spine Network! Warmest regards. Alexandre TEMPLIER ARGOS General Manager Editor in Chief Christian MAZEL ARGOS President
  5. 5. In line with our objective to encourage dialogue, especially between surgeons and bioenginners, we propose, in this issue, the first part of an interview that François Lavaste very kindly granted us. Can you imagine anyone better informed than the director of the LBM himself to help us to more clearly understand biomechanics and the work conducted in the laboratory that he directs? Meeting with a fascinating and fascinated man. Pr François Lavaste, can you give us a definition of biomechanics? Biomechanics is the application of the laws of mechanics to the study of the movement of the human body. The human body is considered to be a material system in the broadest sense of the term. A system which contains solids, deformable bodies, and fluids. In contrast to the mechanics of mate- rial systems, we do not work on inert components since the components in biomechanics are living and their cha- racteristics evolve over time. Let’s take the example of bone tissue: it ages and presents phases of remodelling as a function of the stimuli to which it is submitted. Furthermore, in biomecha- nics, the same component can present very different mechanical characteris- tics from one individual to another. Biomechanics includes structural mechanics when studying the skeleton, fluid mechanics when looking at the circulation of blood and other body fluids and thermodynamics when investigating the process of energy transformation from inspired oxygen through the metabolic pathways to exhaled carbon dioxide. Thus we study all aspects of the circu- lation, mechanical control by muscles, and the physiology of movement. Regulation systems and psychological aspects are not taken into account. Do you think that the science of biomechanics can be dated to a specific discovery? 8 ARGOS SpineNews N°2-October 2000 Interview of Pr. François Lava communication What is Biomechanics ?
  6. 6. communication What is Biomechanics ? I don’t think so. The first wooden splints date to antiquity. The use of mechanical structures to stabilize a fracture constituted an early applica- tion of the principles of biomechanics. These practical procedures were then gradually enriched by basic science to finally constitute the discipline now known as biomechanics. Middle age wooden external prosthesis Who were the main people who contributed to the development of biomechanics? The people that I know are mostly Europeans. Pauwels always seems to be quoted as the first example of a biome- chanician, but we should also mention one of his students, Maquet. Pauwels was both a surgeon and an engineer. He started to apply the laws of mechanics to his surgical practice in the 1930s. Was he already aware of the interactions between biomecha- nics and surgery? Pauwels had a very mechanical view of the human skeleton and the body’s physiologic mechanics. His surgical preparation was always based on mechanics. You also mentioned one of his students? Yes, Maquet applied Pauwels’ concepts to the study of lower extremity move- ment. He can be considered to have been trained by Pauwels. These two pioneers cemented the relationship of biomechanics and orthopaedics. At the end of the 19th century, many scien- tists, such as Marey, were interested in kinematics, the study of movement. Their research was based on the crea- tion of specific devices that were able to mimic the movements of the upper limbs and other body parts. These machines were reminiscent of those developed by Georges Demeny (one of the inventors of cinema). Marey, for example, used this type of appara- tus, i.e. a photographic chamber contai- ning mobile systems and shutters to obtain images every one-tenth of a second, to study the movements of a bird’s wings. Braun and Fischer exa- mined human gait for milittary purpose by trying to optimize the gait of Prussian soldiers carrying a load. And more recently? I think there was a real revolution after these early steps. These first people essentially sowed the seeds of biome- chanics. The progressive development of conventional radiography, CT and MRI certainly contributed to the deve- lopment of biomechanics. Computers, by allowing digital simulation greatly enhanced these measurement modali- ties and gave rise to biomechanics as we know today. Does this mean that technical progress led to progress in the field of biomechanics? Yes. If we look at electronic orthotic systems, for example, we realise that they allowed the quantitative analysis of gait. Marey only performed a quali- tative analysis of gait. When we look at Marey’s images we clearly see the concepts, but when we use electronic orthotics, we are able better describe and quantify the movement. Apart from bioenginners, have specialists from other disciplines contributed to this developing science? Clinical correlation of biomechanical theory has been absolutely vital. For example, orthopaedic surgeons have made major contributions to the field of articular biomechanics. We must not forget that Maquet and Pauwels were orthopaedic surgeons. Vascular surgeons also helped bioen- ginners to understand circulatory phe- nomena and create models. Physiologists, scientists specializing in the analysis and control of movement, tended to work with physiatrists, func- tional rehabilitation specialists. Can we conclude that there has always been a link between bio- mechanics and clinical practice? Yes, although this link varies according to the discipline. I think it is very close in orthopaedics, but not quite as close in the physiology. October 2000 - N°2 ARGOS SpineNews 9 ste : what is biomechanics? PART
  7. 7. communication What is Biomechanics ? What is the reason for this difference? Orthopaedic surgeons are, by nature, closer to bioenginners, as they treat problems “with their hands”. Their sur- gical procedures are very mechanical: they drill, screw, and ream. They work like a mechanic on a machine, but ins- tead of working on an inert part, they operate on the human body. Drilling a hole in the wall to make a shelf and drilling a hole in the tibia to insert a plate are very concrete procedures. This is not very different from a mecha- nic’s work in the industrial context. Orthopaedic surgeons have very concrete and pragmatic mentalities. A history of Biomechanics in France How long have you been director of the LBM? I helped found the LBM and have been the director since it was first crea- ted. I was director of the ENSAM materials resistance laboratory in 1969, and then I was director of the structu- ral mechanics laboratory, where I star- ted to work on biomechanics. The LBM was formed in 1979. Our first biomechanical work dates back to 1972, at the request of Raymond Roy- Camille (inventor of the pedicular screw). One of his students, Gérard Saillant, who is now head of the Department of Orthopaedics and Dean at La Pitié-Salpêtrière, came to see me. He wanted to know whether I could conduct mechanical trials on the ver- tebrae in order to identify the most resistant region. In 1972, we therefore studied the behaviour of vertebrae sub- mitted to mechanical loads inducing rupture and found that the pedicle was the region most resistant to rupture. Raymond Roy-Camille then asked us to study pedicular screw pull-out forces. Simultaneously until 1980, we conducted experimental studies with Gérard Saillant at the Fer à Moulin experimental surgery unit (the Pitié- Salpêtrière dissection unit where orthopaedic and other surgeons are able to dissect bodies donated to science). In 1976, we published an article on disk and nucleus pulposus implants. In a way, this represented the birth of biomechanics in France. At the time, the teams led by Joannès Dimnet were working on analysis of movement in collaboration with Lyon hospital departments. I think that Dimnet had started several years pre- viously in the field of movement ana- lysis and then became interested in the vertebral column. In fact, the two of us followed fairly parallel courses. We trained in the same institution, which explains why we had many points in common and approached problems from the same perspective. Joannès Dimnet was probably one of the first people to have conducted biomecha- nical studies in France. How did LBM start to grow? The development of the LBM occur- red in parallel with a postgraduate trai- ning program, corresponding to a Diplôme d’Études Approfondies (DEA) (Postgraduate Diploma) in Biomechanics, accredited by university authorities in 1985. It was an option of one of the specialties of the DEA in Biological and Medical Engineering of the Ile-de-France region. We entered this training program in 1987, to set up the biomechanics option and the LBM really started to take off at this time. As I already mentioned, it started to take shape in 1979, but really developed in 1985. We took another big step forward 10 ARGOS SpineNews N°2-October 2000 The 2TM experimental apparatus (2micrometric heads) allows experimental study of the behavior of healthy, damaged and reconstructed vertebral segments.
  8. 8. communication What is Biomechanics ? when Wafa Skalli joined us. We would not be as large as we are today if it wasn’t for her. She wrote a PhD thesis on finite element modelling of the ver- tebral column. This was one of the first virtual representations of the vertebral column and quite rare in 1983. She then joined our laboratory in 1988 and greatly contributed to the growth of digital simulation. ▲ Finite element model of a L3-L4 segment instrumented with a disc prosthesis ▼ 3D FEA modeling of a knee prosthesis Was this the beginning of a new generation of bioenginneers? Yes absolutely. The development of digital simulation allowed us to improve our relations with surgeons, since it propelled our work beyond the limits of strictly experimental research. Clinicians work experimentally with their hands and we were able to contri- bute the digital elements of simulation. Virtual representation of the human body was an innovation at that time. Could you explain how you became interested in biomecha- nics with your background of conventional mechanics? My basic training is in mechanical engineering. I was trained at ENS (École Normale Supérieure) in Cachan. I subsequently acquired tea- ching and research experience as director of the materials resistance ana- lysis laboratory. I then became director of the structural mechanics laboratory (a structure is a system of mechanical components). Raymond Roy-Camille’s request was very much in line with our work of mechanical characterization of materials. There is not a major diffe- rence between characterizing rupture of a vertebra and characterizing a beam in civil engineering, apart from the nature of the material. Changing from structural mechanics to osteoarti- cular mechanics therefore does not really constitute a change of scientific direction, but represents a continuous process. We subsequently developed much more specialized activities, more closely related to the human body. This specialization on the vertebral column developed very gradually, but in the beginning, it was not a change of direc- tion, but simply a natural evolution. We also used the same approaches to ana- lyse these problems. We now have machines which are very specific, but, in 1972, we broke our first vertebra with devices designed to break metal- lic structures, because we did not have any material specifically adapted to the human body. Have you ever suffered from prejudice on the part of surgeons? No, I have encountered more prejudice from mechanical engineers. In the beginning, when we were working on anatomic specimens, it induced more than a scientific curiosity among my col- leagues. Some of our colleagues had a very negative view of our activities, as it was based on dissection of cadavers. We also developed models using human tis- sues in order to conduct mechanical experiments. We had to crush these ver- tebrae. The negative perception of our work almost led to suspension of our research. Nobody could criticise wor- king with a concrete or metal test tube, as they are inert parts, but handling a component of the human body in a school of engineering was abnormal! Do you think that these reactions were culturally based? Yes, absolutely. It was perfectly accep- table to examine cadavers in a dissec- ting room, but there was something strange about studying components of the human body on mechanical test machines. There was something not quite right. All of a sudden we were using machines designed to study inert materials in order to test components of the human body. This seemed very bizarre and unhealthy. Experimental in-vitro study of the human pelvis submitted to static lateral loads. October 2000 - N°2 ARGOS SpineNews 11 LBM-ENSAM-PSA-Renault) LBM-ENSAM-CEDIOR
  9. 9. communication What is Biomechanics ? Is this research now fully accepted? Yes, but we founded a laboratory spe- cifically devoted to this field and we now work in a site dedicated to this activity. We resolved the problem by creating the biomechanics laboratory. Our work was difficult to accept while we were installed in a conventional mechanics laboratory, but now this work is recognized as scientific research, as it is a CNRS laboratory (Centre National pour la Recherche Scientifique) [French National Centre for Scientific Research] and the contro- versy has been resolved. This was never a problem in North America. This laboratory therefore developed continuously and I gradually moved from the field of mechanics of struc- tures to mechanics of the human body. All of the specificities of the human body were gradually introduced, lea- ding to the development of our various subspecialities. You mentioned the United States. How does the LBM compare with its American counterparts? The field of biomechanics developed almost simultaneously, but Europe pro- bably had a head start, because I don’t think that Pauwels had an American homologue. In fact, the first American studies were conducted in the 1960s, and then rapidly developed between 1970 and 1980, while the rapid growth of biomechanics in Europe occurred between 1980 and 1990. Didn’t it occur somewhat later? Let’s say that this discipline developed during these years and was gradually recognized as a science. In France, the Société de Biomécanique was founded in the 1970s (François Lavaste was pre- sident of this association), but this society was founded by physiologists and not mechanical engineers, who joined the society a little later. The Société de Biomécanique played a real federating role in the history of this discipline, at least in France, and helped to constitute it as a scientific entity. Its annual congress is now attended by about 200 people, which has helped to forge the identity of its various members. Within this Society we know that we are all bioengineers: fluid bioengineers, osteoarticular bioengineers and physiology of move- ment specialists. Study of the mechanical behavior of a human knee. Was this the birth of a network between the various specialties? A real network was developed, in which each person found his or her place. As President of this society, one of my concerns was to recognize the activities of each of the members. We therefore established a file in which each member indicated his or her fields of interest. We found that one scientist tended to work in the field of muscles, while another worked in the vascular field and another worked in the field of sport and movement. This gave us a clearer vision of biomecha- nics in France. You mentioned that the LBM was created to meet the needs of orthopaedic surgeons. Did its creation coincide with the growth of biomechanics? The creation of the LBM actually coin- cided with progress in orthopaedic sur- gery. Orthopaedic surgeons went loo- king for mechanical engineers because they felt that they had something to offer them. To clearly understand this progress, it must be remembered that, before this time, surgeons designed orthopaedic products purely intuitively. They tried to communicate their ideas to a manufacturer who then developed an industrial product, but the whole process was based on intuition! Wasn’t this an empirical approach? Yes, very much so, and the result could only be assessed after the implant had been installed in the patient. When the clinician worked in collaboration with the mechanical engineer, he was able to add objective elements to his intuition. The birth of biomechanics therefore reflected this process and this really corresponds to the work of Pauwels. He replaced the purely intuitive process by an objective rational approach based on his knowledge of engineering. This led other surgeons to recognize the impor- tance of working with mechanical engi- neers in order to design their products. Raymond Roy-Camille, who intuitively thought of stabilizing the vertebral column by fixation of the pedicles, deci- ded to collaborate with mechanical engineers. He wanted to make sure that his idea was well founded, which is why he asked us to verify that the pedicles were the most resistant part of the ver- tebra. Then, when he asked us to study screw pull-out, he wanted to know whether it would be better to anchor the screws in the cortex of the pedicles and whether this was the site of best purchase. This was an opportunity for mechanical engineers to observe enor- mous differences and variations from one tissue to another. In some verte- brae, the screws could be pulled out by hand as the tissue was completely degenerated, while in other vertebrae, forces of the order of 200 N had to be applied. 12 ARGOS SpineNews N°2-October 2000
  10. 10. communication What is Biomechanics ? Brief review of the history of the LBM. 1964 Pr Raymond Roy-Camille invented and used the first pedicular screw in surgery and established his relationship with the LBM. 1972 First biomechanical studies in collaboration with Pr Raymond Roy-Camille and Dr Gérard Saillant on the mechanical behaviour of lumbar vertebrae. 1985 The LBM participates in the DEA (specia- list diploma) on Biological and Medical Engineering for the Ile-de-France region. Together with the orthopaedics department of La Pitié-Salpêtrière hospital, LBM is responsible for the biomechanics option of this DEA. The ENSAM (École Nationale Supérieure d’Arts & Métiers) is accredited to deli- ver this DEA in coordination with the Universities of Paris XII and Paris XIII. 1988 Important growth of the LBM from this date on, with a rapid increase in the number of PhD.s (six to eight new PhD.s per year) and extension of industrial partnerships. The LBM is transferred to new premises. Close scientific cooperation develo- ped between Dr J. Dubousset (St Vincent de Paul Hospital), Dr G. Duval-Beaupère (INSERM unit 215) and the LBM. 1992 Setting up of international cooperation in the field of spinal biomechanics with the University of Vermont in Burlington, USA (Pr Ian Stokes) and the Ecole Polytechnique in Montréal, Canada (Pr J. Dansereau, Pr J. De Guise, Pr H. Labelle). 1993 The Board of Directors of the Société de Biomécanique appoints the director of the LBM as President of the Société de Biomécanique for a per- iod of two years, thereby acknowledging the scienti- fic work accomplished by the LBM in the field of biomechanics. 1996 The LBM is recognized by the CNRS as an EP 122 applicant team. In the context of spinal bio- mechanics research, and particularly the biomecha- nics of scoliosis, Professor Jean Dubousset joined the LBM team, thereby reinforcing the develop- ment of in vivo research. Did this meeting give you a broader vision of biomechanics? It showed us that biomechanics was not exclusively limi- ted to questions of resistance of materials, but that other parameters were also involved, especially the variability of mechanical characteristics, related to age and tissue degeneration. Parameters that we were not used to taking into account in our classical mechanical calcula- tions Were the two disciplines enriched by this exchange? They both obtained an enormous and even fascinating enrichment. By incorporating alloys, and by slightly modi- fying them, we can alter the mechanical characteristics of steel, but not to the same extent as those of bone tissue. It was at this point that we realised that biomechanics was not exactly the same thing as mechanics, as all of the parame- ters are radically transformed by the fact that we are dea- ling with living matter and not inert matter. ■ CS. Parent [The second part of this interview will be published in the next issue of ARGOS SpineNews] Contact information If you would like additional information or if you would like to visit the LBM-ENSAM laboratory, please call: +33 (0) 1 44 24 63 24, or explore our website: or contact: Pr François Lavate - Pr Wafa Skalli - Research office: Laboratoire de biomécanique École Nationale Supérieure d’Arts & Métiers 151, boulevard de l’hôpital 75013 Paris FRANCE Phone: +33 (0) 1 44 24 63 64 Fax: +33 (0) 1 44 24 63 66 Secretary: Vanessa Valminos October 2000 - N°2 ARGOS SpineNews 13
  11. 11. The first meeting of the Argentinean ARGOS association was held in Buenos Aires on August 10-12, 2000. JEAN-PIERRE FARCY, MD of New York University’s Hospital for Joint Disease and Maimonides Medical Center was the guest speaker. Dr. Farcy is an internationally recogni- zed expert on the treatment of pedia- tric and adult deformity. The conference’s first day was devoted to lumbar osteotomy for the correction of post-fusion flatback deformity. The highlight of the day was a live surgical demonstration by Dr Farcy and Dr Carlos Solá from the Hospital Italiano. This was followed by a lively group discussion of the indications for, techniques of, and complications asso- ciated with these difficult procedures. The second day was devoted to clinical case presentations. Diverse opinions were discussed in a spirit of open-min- ded collegiality. As is common at scien- tific conferences, a general consensus was obtained but unanimity of opinion was impossible to find. The international ARGOS framework has provided an invaluable template for the growth of this fledgling research group. We understand that Belgium has also formed a national ARGOS chapter and that discussions are pro- gressing toward an American organi- zation as well. The long-overdue goal of a worldwide community of surgeons and researchers - enriched by local experience but not bound by regional prejudice - is becoming an exciting rea- lity. Lastly, we would like to convey our appreciation to Euromed for their generous support of our inaugural scientific meeting. Left to right : Mr C. Carballo, Pr JP. Farcy, Mr H. Segura 14 ARGOS SpineNews N°2-October 2000 Inaugural meeting of Argos - Argentina communication Events
  12. 12. communication Events A major event for all health care professionals was held March 14-17 at the Parc des Expositions de Paris Nord. THIS YEAR, the Hôpital expo and Intermedica trade shows merged to form a single show and another four exhibitions were added to this event: the salon du laboratoire-Bioexpo (the most important French life sciences trade show), Stramed (the biomedical industry subcontractors trade show) and Hyprotex (textile hygiene and processing). These six shows now constitute the largest health care trade show in France. More than 1.000 exhibitors presented a panorama of their products and most recent equipment at this show, ranging from ancillary instruments to complete operating rooms. Entire synthetic spines were even available. The larger companies invested impressive resources in this show, extending over an area of 70.000 m2 . Each stand rival- led the others to catch the visitor’s eye. After visiting a waterfall, a theatre stage, and a sportsman in the middle of a training session, the visitor could stop and watch an amazing presentation of the latest developments in robotics, supported by video interviews with surgeons. A large number of visitors were interested in textile processing systems and restoration devices. A sec- tion was devoted to emergency and trauma medicine, allowing the visitor to examine this equipment in detail. New technologies were strongly repre- sented. Many companies presented their products in medical imaging and telemedicine augmented by the limit- less possibilities offered by computers. Another area of the show was devoted to the Internet. A Quebec delegation also attended the show. The Association Quebecois des Fabricants de Matériel Médical (AQFIM - Quebec Association of Medical Equipment Manufacturers) came to France to present its members’ latest inventions. Thanks to new tech- nologies, we were able to participate in a paediatric cardiology examination live from Quebec. Mr Jacques De Guise, associate Pr of the depart- ment of surgery at the faculty of medi- cine of the university of Montreal and Pr in the department of automated pro- duction engineering in the Laboratoire d’Imagerie, de Vision et d’Intelligence Artificielle (LIVIA - Imaging, Vision and Artificial Intelligence Laboratory) and Mr L’Hocine Yahia, full Professor, director of the biomechanics and bio- materials research group, mechanical engineering department of the école polytechnique of Montréal presented the work of the Laboratoire de recherche en Imagerie et Orthopédie (LIO - Imaging and Orthopaedics Research Laboratory). ■ CS. Parent October 2000 - N°2 ARGOS SpineNews 15 Expo-Intermedica THE PURPOSE OF THIS SEMINAR was to pre- sent new surgical procedures for the treatment of spinal diseases, an overview of minimal invasive tech- niques in spinal surgery, and current theories in bio- mechanics. Scientists from “Maurice E. Müller” Institute for Biomechanics at the University of Bern, Switzerland, and from the Biomechanics Laboratory of ENSAM (Ecole Nationale Supérieure des Arts & Métiers) in Paris, France, were present among surgeons from different countries. Pr Sapkas, who organised this congress in conjunction with the scientific committee (P. Efstasthiou, N. Zervakis, M. Kasseta, K. Kateros, G. Kountis, A. Badekas, N. Bitouni, P. Boscainos, E. Stilianessi, G. Tzagarakis, and V. Tzortzakis) gave all those in attendance the warmest welcome in the library of the little port of Poros, located at 50 mn from Athens by boat. This seminar, which began on Friday June 9th in the afternoon, and ended on Sunday, June 11th at Noon, was a perfect blend of high level scientific exchanges, and conviviality. More information on this seminar can be obtained from Pr George Sapkas ( ■ 7 TH seminar of spinal biomechanics, Poros Greece
  13. 13. This is the website of a famous American Association: the AAOS (American Academy of Orthopedic Surgeons). Unlike the Video Medical Journal website, the colored interface of the homepage encourages draws the visi- tor into the site. A great deal of infor- mation is available (ranging from publi- cations to CD-ROMs to videos). Nothing has been overlooked. One heading is devoted entirely to patient commentary. Unfortunately, most of the site is exclusively reserved for members of the Academy. The shear volume of information may be overw- helming to inexperienced netsurfers, however. The internet is not just a passing craze, it is everywhere. Today, no company or association can afford to ignore this media. Convinced of the importance of Internet, our American partner, Ortholink, has taken up the challenge and developed a simple and effective website. The first advantage of this site is that the designers have wisely avoided submerging the visitor under tons of superfluous information. The easy-to- read home page further facilitates the use of this site. In contrast to the aus- terity of so many other websites, the modern design gives it an attractive appearance and even inexperienced netsurfers can easily find their way around with, as bookmarks present at the top and bottom of each page guide the novice. No matter how attractive the site, it only has any real value when it pro- vides services not available with conventional media. The products mar- keted by Ortholink are described in detail. If you are interested in one of these products and wish to purchase it, remember that the on-line order form is protected by a security payment sys- tem. We obviously could not devote an article to the Laboratoire de BioMécanique without presenting its website, which is much more than a simple eMail address and provides a wealth of information. It is not desi- gned to present scientific information for the general public, but it is never- theless accessible to non-specialists. The general presentation is a relevant introduction to the world of biome- chanics, all to brief, unfortunately. However, the four research groups composing the laboratory present their work in much more detail. You can read about the various studies, espe- cially those devoted to the spine. Don’t skip the other research groups, because their work is sometimes presented through animated sequences. The publications and communications hea- 16 ARGOS SpineNews N°2-October 2000 Web review Orthopedic surgery appears on the internet in a variety of contexts ranging from academic institutional websites and websites for commercial ventures to personal webpages for individual surgeons. Educational material and product information is now avalaible around the clock. internet Web review
  14. 14. internet Web review ding are particularly interesting. About thirty doctoral theses are summarized by abstracts, sometimes accompanied by surprising illustrations. Finally, the bilingual interface (French- English) is clear and practical. If you missed the exhibition entitled Étienne Jules Marey: le mouvement des lumières, organized by the Fondation Electricité de France from 13 January to 19 March 2000, then this site admirably attempts to summarize the exhibition and provide even more information about this extraordinary man. You will discover or rediscover the range of Marey’s inventions, each one more fascinating than the next, from the cardiograph to the aeroplane as well as biomechanical processes. Two types of tours are available: the on- line exhibition and/or a thematic visit. We heartily recommend both of these visits, as they are very complementary. As you will see, the general presenta- tion of the site is very attractive and well adapted to the subject treated. There is only one drawback: there are only a few video illustration (of all things !), which are time-consuming to download. General public television is already available by Internet, but Progress-TV has recently launched the first French- speaking channel entirely devoted to medicine. Some sites already present medical information for the general public, but medecine-tv is more parti- cularly designed for health care pro- fessionals. You rapidly reach an attractive home- page, which is clear and easy to use. A large number of headings are presen- ted. We must congratulate the desi- gners, who have succeeded in combi- ning a user-friendly presentation with a large volume of information. Take a look at the magazines with inter- views, or the various subjects devoted to surgery, etc. This last heading is par- ticularly interesting. The main advan- tage of this site is to exploit the various possibilities available by Internet, pro- viding on-line films devoted to the various medical specialties. A film about fifteen minutes long is devoted to spondylolisthesis. This film format is obviously not up to current standards and the quality of the images largely depends on your modem and phone cable. You must also have installed Real Player® software (free and easily down- loaded). This interesting initiative nevertheless deserves your attention. If you are looking for a video document and don’t know how to obtain it, consult the British Video Medical Journal website. This site combines the two extensive video libraries of the British Orthopaedic Association and the American Academy of Orthopedic Surgeons. Almost 200 videos on sub- jects as varied as the knee, the hands and the spine, are available. It is true that the interface is fairly aus- tere and downloads are sometimes a bit slow, but you will be able to easily find your way around this very accessible site. However, if you happen to find the object of your desires, you cannot order it on-line. Instead you will need to print an order form, fill it in and return it. ■ CS. Parent … And don’t forget to consult the ARGOS website: October 2000 - N°2 ARGOS SpineNews 17
  15. 15. 5TH Internationa Argos sym FRIDAY JANUARY 26TH 2001, PARIS - MAISON DES AR A spineObviously, we could not keep from alluding to Stanley Kubrick’s film. The beginning of the 3rd millenium is the start of a new Odyssey for vertebral column surgeons. New technologies are playing a greater role in daily surgical prac- tice. It seems only logical to dedicate this year’s ARGOS symposium to this evolving interface. The hardest part of designing the program was deciding what to discuss and what to leave out. Thus, instead of discussing proven techniques such as video-assisted surgery, we have chosen to concentrate on more eminently emerging - and perhaps not-yet-proven - techno- logies. The morning session will be devoted to imaging developments. We will be joined by engineers from General Electric, Professor Christopher Ullrich (neuroradiologist at the Medical University of South Carolina and President of the Cervical Spine Research Argos Secretary : Marjorie SALÉ - Phone +33 (0) 3 21 21 59 64 - Fax +33
  16. 16. l mposium RTS & MÉTIERS - 9BIS AV. D’IENA PARIS XVI odysseySociety), Professor Jacques De Guise (from Montreal’s Imaging and Orthopaedics Research Laboratory), and Professor Jean-Claude Dosch of Strasbourg. Afterwards, we will discuss progress in intraoperative navigation systems. While these devices are intellectually enticing, they have not yet proven their worth in daily surgery. The Medtronic and Aesculap companies will present their different processes. In addition, they have agreed to allow two members of ARGOS use of their navigation systems in the operating room. These experi- menters will tell us about their experience as novices with these ultra sophisticated systems. We will have the opportunity to see the poten- tial, and potential limitations, of these technolo- gies by viewing a live surgery from the opera- ting theater at the IMM. In the afternoon session, we will examine the legal pitfalls for insuring data security that are incumbent in this technology. Cegetel, the company who designed and oversees the French health care computer network, will share their experiences with us. The day will conclude with an investigation of the rapidly multiplying Internet sites created by orthopaedic surgeons. Professor Jean-Pierre Farcy will discuss the possibilities and restrictions on these sites and Mme. Isabelle Lucas Balloup, attorney “à la cour de Paris” will temper our enthusiasm by reviewing the many European statutes governing this new realm of discourse. Sadly, we realize that the day will be too short to examine fully all aspects of this technological and surgical revolution. We hope instead to illu- minate this new world, spark a collegial debate about its evolving role, and begin a dialogue on the very future of medicine. The Argos Board: Christian Mazel MD, Pierre Kehr MD, Jean-Paul Steib MD, Alain Graftiaux MD, Frank Gosset MD. (0) 3 21 21 59 70 -
  17. 17. Iron atoms in a copper matrix. Many Arts et Métiers engineers and future engineers accepted this invitation to participate in a conference- debate on nanotechnologies at the Ecole Nationale Supérieure d’Arts et Métiers in Paris, on Wednesday 15 March 2000. André MASSON, Former President of Angénieux SA and Founding President of the nanotechnology club, presented a convincing paper on this infinitely small universe with the participation of Jean FOURMENTIN-GUILBERT, President of the FOURMENTIN-GUILBERT scientific foundation for the growth of biology. NA N O T E C H N O L O G I E S concern the materials, methods and processes used to observe and manufacture products or structures whose dimensions or acceptable ranges are of the order of nanometres (10-9 m), in other words a size comparable to that of the basic components of matter (atoms and molecules). They cover the range of dimensions from 0.1 to 100 nanometres. Take a millimetre (10-3 m), divide it by 1000 and you obtain a micron (10-6 m); divide a micron by 1000 and you obtain a nanometre. Nanotechnologies have given birth to nanosciences: these “new frontiers of the technologically possible”. For example, they are designed to displace, manipulate and even assemble atoms. We often use these technologies in eve- ryday life, often without being aware of it. For example, to ensure correct rea- ding of a compact disc, the drive shaft must be stable to within 20 to 30 nano- metres. General public printers are fit- ted with inkjet print heads, which were developed by means of processes with a similar degree of precision. The prospects for the future are very attractive, as these disciplines are going to become an integral part of computers, medicine, biology, surgery, etc. Ultraprecision machining will allow even greater miniaturization and compactness, thereby increasing the functional capacity of products. One possible application would be implan- table drug delivery systems. It would even be possible to introduce transducers and detectors inside an artery! However, the complexity and volumes that can be achieved at the pre- sent time are still very insuf- ficient. Other potential applications are also very interesting. If scientists could manipulate atoms one by one, it would be possible to eliminate all impurities from matter and create more resistant products. For example, glass has been made from silica, but without involving a fusion step. This experience showed that the physical properties of the glass obtained were radically altered. Even more astounding discoveries can be expected with very light materials, but just as resistant as diamonds. André Masson and Jean Fourmentin- Guilbert emphasized the importance of nanotechnologies in tomorrow’s world. They announced that the President of the United States, Bill Clinton, has pro- posed that the budget of 200 million dollars already devoted to these tech- nologies be doubled. In Japan, a sum of 500 million dollars is devoted to this research! ■ CS. Parent A synthetic self-assembling spherical complex. Cover caption “Tetramethyladamantane” (green) is encapsulated by two molecules of a self-complementary synthetic receptor. An array of weak intermolecular forces are balan- ced to produce the assembly in solution. (Red spheres, oxygen atoms, blue spheres, nitrogen atoms.) 20 ARGOS SpineNews N°2-October 2000 Discover the fantastic world of nanotechnologies and its expected growth at the beginning of this new millenium science Nanotechnologies A “Buckyball”
  18. 18. Considerable progress has been made in the field of spinal surgery in recent years, and instrumentation as well as the basic principles of correction have been enriched by new ideas (6). Despite this extraordinary progress, the modes of vertebral fixation remain limited to pedicular screws, and laminar or pedicular hooks (8), or sublaminar wires or cables. Each type of implant has its own supporters and detractors and each one has its respective advantages and disadvantages. ALL OF THE CURRENTLY avai- lable implants are unilateral and only fix the left or right part of the spine. The Raymond Roy-Camille pedicular screw is now 35 years old (11) and is very technically demanding to insert. Although it ensures solid fixa- tion of the posterior and anterior parts of the vertebra, there is always a risk of pedicular perforation, especially in the thoracic spine (4). Laminar hooks require opening of the vertebral canal; they have an upward or downward direction of fixation, requiring a dis- traction or compression force, which can be neutralized by a posterior lami- nar (12) or pediculo-transverse clamp. Wires require repeated opening of the canal with simple, but not very solid fixation and do not allows distraction or compression efforts. These various aspects led to the idea of development of a new form of fixation, which is easy-to-insert without ope- ning the canal, solid with bilateral anchoring and without prestressing during insertion, and allows distrac- tion-compression and anteroposterior traction or pushing forces. Material: Since the costover- tebral space is a virtual space and is frequently used to insert transverse process hooks and to per- form pediculo-trans- verse clamps, it should be suitable for use in this set- ting (fig. 1). After removal of the tip of the transverse pro- cess, the pedicle can be reached by passing between the rib and the ver- tebra. Two bifid plate hooks are placed in contact with the lateral surfaces of the pedicles, while the body of the hooks rests on the base of the trans- verse process. A transverse com- pression link connects the two implants and encircles the posterior laminar arch. This consti- tutes a lateral clamp, which grasps the vertebra by its two pedicles (fig. 2a,2b,2c). The body of the hook is at an angle of 90° to the axis of the plate in order to receive a rod from each side. The bipedicular implant (BPI) there- fore constitutes a new method of fixa- tion, with novel anatomic relations and lateral purchase. The safety and relia- bility of this bipedicular vertebral fixa- tion had to be evaluated. 22 ARGOS SpineNews N°2-October 2000 evaluation A new bipedicular implant fig. 1 Costo-vertebral space = safety zone fig. 2a A new bipedicular implant Analysis of a new spinal fixation device Jean-Paul STEIB, MD,* Emeric GALLARD, MSc Eng,** Laurent BALABAUD, MD* ■ fig. 2c fig. 2b * Hôpitaux Universitaires de Strasbourg - ** ENSAM Biomechanics Laboratory
  19. 19. evaluation A new bipedicular implant Methods: A biomechanical evaluation was necessary to validate this new fixation (3, 9). Studies are currently underway on fresh cadavers in the ENSAM Laboratoire de Biomécanique (LBM) [Biomechanics Laboratory] in Paris (7). These studies are designed to assess solidity and stability (1, 10, 14). Solidity tests initially consist of eva- luating the resistance of the pedicles to bilateral com- pression forces (fig. 3). This pedicular resistance is fun- damental to assess the safety of the implant, as excessive fragility could threaten the spinal cord. The posterior and lateral pull-out forces (2, 5) of the bipedicular implant fixed onto an isolated vertebra are then evaluated (fig. 4). Stability studies are designed to evaluate the mobility of the instrumented thoracic spine using two CD instru- ments, one using standard pedicular hooks, and the other the bipedicular implant (fig. 5). In both types of fixation, T11 is fixed onto a platform and T3 is subjected to various loading modes: flexion-exten- sion, lateral inclination and axial rotation. Displacements of the T3, T6, T7 and T8 vertebrae are measured for each loading and the curves corresponding to the two types of fixation are compared. October 2000 - N°2 ARGOS SpineNews 23 fig. 3 Compression strength References 1. Abumi K, Panjabi MM, Duranceau J Biomechanical evaluation of spinal fixation devices: III. Stability provided by six spinal fixation devices and interbody bone graft. Spine 1989; 14 (11): 1249- 1255. 2. Berlemann U, Cripton P, Rincon L, Lippuner K, Schlapfer F - Pull-out strength of pedicle hooks with fixation screws: influence of screws length and angulation. Eur. Spine J. 1996; 5:71-73 3. Diop A, Skalli W, Lavaste F - Tests et épreuves biomécaniques incontournables pour le développe- ment d’une nouvelle instrumentation rachidienne. In: Pous, Les instrumentations rachidiennes. Cahiers d’enseignement de la SOFCOT, 1997: 31-40 4. Doursounian L, Henry P - Vissage pédiculaire. In: Pous, Les instrumentations rachidiennes. Cahiers d’enseignement de la SOFCOT, 1997: 31-40 5. Gayet LE, Muller A, Pries P, Duport G, Bertheau D, Lafarie MC - Etude de la résistance à la traction de l’arc vertébral postérieur thoracique. Rachis 1998 ; 10(1): 19-26 6. Karger G, Steib J.-P, Roussouly P, Chopin D, Roy C, Dimnet J, Mazel Ch, Marnay T, Dimeglio A Les “nouveaux” systèmes d’instrumentation rachi- dienne postérieure. In: Pous, Les instrumentations rachidiennes. Cahiers d’enseignement de la SOF- COT, 1997: 121-128 7. Lavaste F - Biomécanique et ostéosynthèse du rachis. Cahiers d’enseignement de la SOFCOT. Conférences d’enseignement 1997: 121-145 8. Milon E - Crochets pédiculaires, laminaires et transversaires. Du Harrington au Cotrel-Dubousset. In: Pous, Les instrumentations rachidiennes. Cahiers d’enseignement de la SOFCOT, 1997: 53-57 9. Panjabi MM - Biomechanical evaluation of spi- nal fixation devices: I. A conceptual framework. Spine 1988; 13 (10): 1129-1134. fig. 4 Pull-out strength lateral pull-out force posterior pull-out force F F
  20. 20. evaluation A new bipedicular implant Traditional CD construct BPI construct figure 5 Discussion: This implant allows pedicular anchoring without opening the canal and without destabilizing the spine. Sacrifice of the tip of the transverse process appears to have negli- gible consequences. This device can be safely implanted (13) in an avascular space devoid of any nervous struc- tures. Unlike pedicule screws, this technique is not asso- ciated with a difficult learning curve and the possibility of accidental and unidentified perforation of the vertebral canal with its potentially serious consequences. The BPI is not incompatible with laminectomy if the pedicles are preserved and are in a good condition. There is no spe- cific direction of use (neutral implant), in contrast with the currently available hooks. Its action and excellent purchase are very useful for correction of deformities by rod rotation or in situ contouring. Spatial manipulation of the vertebrae should be facilitated, especially in the horizontal plane, which should primarily allow effective correction of rotation. 24 ARGOS SpineNews N°2-October 2000 References 10. Panjabi MM, Abumi K, Duranceau J, Crisco JJ Biomechanical evaluation of spinal fixation devices: II. Stability provided by eight internal fixation devices. Spine 1988; 13 (10): 1135-1140. 11. Roy-Camille R, Garcon P, Begue Th Techniques chirurgicales. Etude biomécanique de l’ancrage des vis pédiculaires dorsales et lombaires. 7èmes journées de la Pitié-Salpétrières 1990: 29-35 12. Tencer AF, Self J, Allen BL, Drummond D Design and evaluation of a posterior laminar clamp spinal fixation system. Spine 1991; 16(8): 910-918 13. Thanapipatsiri S, Chan DPK - Safety of thora- cic transverse process fixation: an anatomical study. J. Spinal Dis. 1996 ; 9 (4):294-298 14. Wilke HJ, Wenger K, Claes L - Testing criteria for spinal implants: recommendations for the stan- dardization of in vitro stability testing of spinal implants. Eur. Spine J. 1998; 7:148-154 T11 T7 T3 Z X Y Z X Y T11 T7 T3 fixation of T11 Application of loads in the three planes on T3 Measurement of the relative 3D motions between T6 and T8 Standard hooks Standard hooks Standard hooks bipedicular implant bipedicular implant Standard hooks Standard hooks Cross link Cross link Conclusion: This new type of implant needs to be tested in in vivo clinical situations, but the preliminary results are promising and suggest a multitude of applications, not only for fixation and correction of vertebral deformities, but also for fixation of the traumatic, tumoral or degenerative spine. Improvements will be made depending on the results of ongoing trials. ■
  21. 21. The year 2000 is the year of new technologies. The Internet is developing at an exponential rate, and new technologies, only recently embryonic, are emerging nearly full-grown. SURGICAL navigation or “stereo- taxis”, first developed in the 1980s, in the field of neurosurgery, has now been extended to other specialties, especially orthopaedic surgery. Since the end of the 1980s, pedicular align- ment systems for spinal surgery have been developed according to various principles, but always with the same objective: spatial guidance of a high- risk surgical procedure, using medical imaging and 3D locali- zation systems, in order to avoid damage to particularly fragile struc- tures such as nerve roots or dura mater. Then, in the 1990s, navigation systems were developed in the field of knee surgery and the objective, in this context, was to improve the positioning of femoral and tibial implants during total knee arthroplasties. Other stereo- tactic applications in orthopaedic sur- gery, such as knee ligament recons- truction, or insertion of acetabular implants, were also developed. Several research centers all over the world are currently working in the field of com- puter-assisted orthopaedic surgery, including the Laboratoire d’Imagerie et Orthopédie (LIO) [Imaging and Orthopaedics Research Laboratory] in Montréal (Quebec), the TIM-C labo- ratory of Joseph Fourier University in Grenoble (France), and the UPMC Shadyside Hospital Center for Orthopedic Research in P i t t s b u r g h , Pennsylvania (USA). Although these technolo- gies, grouped under the generic term of “surgical navigation”, are very useful for orthopaedic surgeons wishing to ensure a spatially safe and reliable procedure, they do not provide any information for the choice of procedure, and do not allow retros- pective evaluation of the efficacy of the procedure chosen. In addition, they are purely intraoperative technologies and have offered little advantage to the pre- and postoperative phases of patient care. In spinal surgery and knee surgery, medical images (x-rays, MRI, CT, etc.) are most of time used as qualitative sources of information, and very few tools provide surgeons and radiologists with rapid, reproducible and precise measurements of morphological and functional parameters. These measu- rements would have a three-fold value: to provide surgeons with quantitative objectives that can be used during the operation (with or without surgical navigation), to verify the imme- diate postopera- tive result obtained in terms of the desired adjustments and to follow the course of morphological and functional parameters over time in relation to the clinical results obtained. Noninvasive measuring modules, based on analysis of standard medical imaging and/or direct measurements, linked to a clinical database, would provide orthopaedic surgeons with a global quantitative vision of their patient’s morphology, posture and joint mobility. This information, accessible to a given surgeon for all of his patients, would enable the surgeon to gain maximum benefit from his everyday experience, and beyond that, to share this experience with his peers on the basis of objective measurements. The locomotor apparatus is particularly suitable for this type of approach, as it is submitted to considerable cyclical mechanical loads related to the 26 ARGOS SpineNews N°2-October 2000 New trends in computer technologies Computer-assisted surgery
  22. 22. communication Computer-assisted surgery patient’s morphology and posture. The range and type of joint movements are also very important factors in bio- mechanical load distribution, and consequently in the patient’s postoperative outcome. Measurement of the postural and kinematics parameters of the locomotor apparatus therefore has an important place in the choice of operative strategy and analysis of the postoperative course in orthopaedic surgery, but many sources of infor- mation, such as conventional radiography, are currently not used to their full advantage. ■ A. Templier From leonardo Da Vinci sketches to 3D medical imaging. October 2000 - N°2 ARGOS SpineNews 27 assisted surgery Surgiview® : first surgeons, then tools… THE SURGIVIEW® company was created in April 2000 in order to develop a full range of computer- assisted diagnostic, surgical and follow-up tools. Combining the needs and skills of orthopaedic spe- cialists, orthopaedic surgeons, and also biomechanical and medical imaging scientists and industrial partners, SurgiView® , in the context of an Eureka project (∑ 2288 Medac), intends to provide surgeons, over the next two years, with a complete range of software pro- ducts and equipment designed for preoperative and postoperative assessment and navigation in ortho- paedic surgery. The current official partners of this project are: - Laboratoire de Biomécanique de l’Ecole Nationale Supérieure d’Arts & Métiers, Paris (France) - Laboratoire d’Imagerie et d’Orthopédie, Montréal (Quebec) - Association ARGOS (international Association of Research Groups for spinal OsteoSynthesis), Paris (France) - Zebris, Tübingen (Germany) - IVS, Chemnitz (Germany) - The Eurosurgical and Tornier companies. The first module proposed by SurgiView® , composed of SpineView® 1.0 software and the clinical database, is currently under investigation in French clinical cen- ters participating in the project: - Institut Mutualiste Montsouris – Paris (Dr Mazel), - Hôpital Hôtel Dieu – Nantes (Prof. Passuti, Dr Delecrin), - Hôpital Pitié – Paris (Prof. Saillant, Prof. Lazennec), - Hôpital Beaujon – Paris (Prof. Guigui), - Hôpital Tripode – Bordeaux (Prof. Vital). A progress report of these studies will be presented regularly in your ARGOS SpineNews journal. Computer-assisted imaging of coronary arterial flow.
  23. 23. “The hope of reaching the truth is sufficient for those who pursue science through all their efforts: the contemplation of the laws of nature has provided great and noble enjoyment to those who have discovered them”. Etienne-Jules Marey (1830-1904) WHAT DO biomechanics, bird- watching and a good film have in common? Nothing at first sight, but let us look more closely at the work of Etienne-Jules Marey. Born in Beaune (France) in 1830 (where a museum is devoted to his life and work), this Burgundian, from a humble background, remains one of the major figures of 19th century science. He was simultaneously a doc- tor, physiologist, clinical pathologist, professor at the College de France and a member of the French Academy of Medicine. He was also responsible for a multitude of discoveries with appli- cations from medicine and physiology to aviation, cinema and photography. The majority of his career was devoted to the development of graphic methods to record physiological activity. He conducted some remarkable studies on blood circulation and cardiac mecha- nics, but his insatiable curiosity also led him to investigate many other areas of locomotion from analysis of the flight of birds to a detailed description of human gait. This movement-fascinated scientist was largely forgotten after his death but his legacy studies, drawings, graphs, photography, and films (the first films in the history of cinema) have recently begun to receive their long- overdue attention as scientific disco- veries and magnificent works of art. At the end of the last century, this French physician-physiologist was the first to analyse movement in detail as well as measure it and rigorously reproduce it. “This approach constitutes one of the foundations of modern orthopaedics” according to another important figure of biomechanics, Johannes Dimnet, former director of the Laboratoire de Biomécanique du Mouvement (Biomechanics of Movement Laboratory) at Claude Bernard University in Lyon (France). Photography played an essential role in Marey’s research. Using this process, he developed chronophotography in 1892. With this process, biomechanics took a giant step forward. His invention “the photograph gun” was able to break down any movement into its components by successive views taken at regular intervals over time. “The photograph gun” By taking series of twelve images per second, Marey was able to describe, for the first time, the sequence of visible movements of a walking man, but his process was unable to cross the barrier of the skin to observe joint movements. Many photographs were taken with an almost cubical box with sides measu- ring about thirty centimetres. Although developed in 1890, they already dis- played all of the principles of the camera, as subsequently defined by the Lumière brothers. It included an impression frame and a spring motor. He also used celluloid films, which stopped intermittently in front of the focal point of the lens. “The cubical box” In 1961, the French Cinémathèque acquired about 400 letters written by Etienne-Jules Marey between 1881 and 1894 to his assistant Georges 30 ARGOS SpineNews N°2-October 2000 Etienne-Jules Marey The eye of Biomechanics history Etienne-Jules Marey
  24. 24. history Etienne-Jules Marey Demeny (now recognized as the real inventor of cinema). This very valuable correspondence is stored in the Film Library, and has been indexes with a number of letters found in other archives. This collection also includes about sixty unpublished letters from the period 1877-1904. In particular, this documentation provides a precise description of the scientific programme developed by Marey and Demeny at the Parc des Princes physiology station. It was in this now mythical place that the two scientists worked to develop their various chronophotographic devices. A window into the scientific world at the end of the 19th century, this collection also reveals the private side of Marey, especially the Neopolitan holidays he so enjoyed. EJ. Marey working in his garden As a pure scientist, Marey refused to market his process, which was rapidly taken up by his contemporaries… Louis Lumière improved this appara- tus, then patented the process in 1895. ■ October 2000 - N°2 ARGOS SpineNews 31 THE PURPOSE of The International Society for the Study of the Lumbar Spine, a non-profit organization founded in 1974, is to bring together those individuals throughout the world, who, by their contributions and acti- vities both in the area of research and clinical study, have, or are indicating interest in the lumbar spine in health and in disease. Its further purpose is to serve as a forum for the exchange of information of both an investigative and clinical nature which relates to low back pain and disability. The International Society for the Study of the Lumbar Spine has established a Research Fellowship to promote and extend research activities into the cause and cure of low back pain. The fellowship is awarded annually based upon the merits of the applicant, as judged by the Fellowship Committee of the Society. Currently, a stipend of $15,000.00 US. will be granted to the recipient. A prospective applicant should have completed formal training in a medical or allied specialty and should be involved in an investigation of a specific pro- blem which would be furthered by travel to a location other than his own. An applicant should be sponsored by a member, or must be a member of The International Society for the Study of the Lumbar Spine. The competition is open to all qualified investigators who may apply singly or as representative of a group. Application is to be made by a letter to a Committee, specifying the details of the topic to be pursued, the location to which the fellow would travel to further his study, and the expectations ari- sing from the venture. Along with the letter of application, a prospective fel- low should provide a Curriculum Vitae for each proposed investigator and a statement of sponsorship of the applicant from a member of the Society, as well as a letter from the Institution the applicant intends to visit confirming their acceptance of your visit. Also please include the Curriculum Vitae of the researcher you will visit. Four copies of each should be submitted. Applications for the 2001 competition must be received by March 1, 2001. The Committee will announce its selection shortly after this date. The reci- pient of this award should be prepared to present a report of his efforts to the 2002 annual meeting in Cleveland, OH, USA, May 14-18th. ■ Applications should be submitted to The International Society for the Study of the Lumbar Spine Sunnybrook and Women’s College Hospital Science Center - 2075 Bayview Avenue, Room MG 323, Toronto, Canada, M4N 3M5 Phone 416-480-4833 - Fax 416-480-6055 eMail: Fencing motion analysis
  25. 25. Closing the loop in surgical practice: ssing computer assisted surgical tools to enable continuous process improvement in healthcare The Centers for Medical Robotics and Computer Assisted Surgery (MRCAS) establish a collaboration between the sister labs at UPMC Shadyside Hospital and Carnegie Mellon University’s Robotics Institute. The MRCAS program is helping to take orthopaedics and other surgical sub- specialties into the 21st century. This unique program combines robotics, engineering and computer science to assist physicians in the planning, simu- lation and performance of surgery as well as in measurements of postopera- tive outcomes. The goal of the Centers is to foster the application of these enabling technologies within all areas of medicine and surgery with the initial primary focus in orthopaedics. The success of the program is founded on the tight integration in three main areas: (I) clinical programs; (II) research and development into the “surgical toolbox of the future” and the next generation of more accurate and less invasive computer-based surgical tools; and (III) developing metrics and measuring patient outcomes through a Total Joint Registry. The MRCAS program relies on institu- tional and regional strengths in existing clinical programs and expertise in the areas of computer science, robotics and healthcare and provides the focus of activity that integrates high quality cli- nical practice and the research and development of new innovative tech- nologies. These tools have the potential to help our patients by making proce- dures less invasive and more accurate and also by directly relating patient out- comes to measurements of surgical technique - in essence “closing the loop” in surgical practice. This com- prehensive approach will improve patient outcomes in a cost-effective manner by enabling continuous process improvement, immediately and in the future. What is Medical Robotics and Computer Assisted Surgery? Medical robotics and computer assisted surgical technologies span the broad areas of science and engineering to create intelligent tools that can be applied to clinical practice. Robotic technologies, navigation systems and computer assisted tools can improve existing clinical procedures as well as provide innovative new approaches to clinical problems. A new breed of computer-based devices presents sur- 32 ARGOS SpineNews N°2-October 2000 The center for medical robotics and computer assisted surgery at UPMC Shadyside and Carnegie Mellon University A. DiGioia, B. Jaramaz, T. Levison, J. Moody, C. Nikou, R. LaBarca, P. Muir & F. Picard ■ focus on The Robotics Institute fig. 1 - Hip replacement surgery using HipNav: Optical localizer tracks the position of bones and tool. Information is displayed on the TV monitor.
  26. 26. focus on The Robotics Institute geons with robust, clinically practical tools that can do much to augment the physician’s skill while reducing the expense of healthcare. Moreover, these tools can be used to directly relate mea- surable surgical practice to patients’ outcomes enabling continuous process improvement in healthcare-reducing costs by ensuring quality. In addition to the ongoing work within the Robotics Institute and UPMC Shadyside, MRCAS draws upon addi- tional personnel and resources from departments within Carnegie Mellon University such as Civil Engineering, Biomedical Engineering, and Computer Science. MRCAS has three primary goals: 1- perform application-oriented research aimed at addressing real life clinical needs. 2 - promote collaboration between physicians and researchers. 3 - raise the awareness and support for robotics and computer assisted techniques within medicine through an active educational program. Some of the technology already exists to address these clinical needs; howe- ver, the integration of the constitutive parts is often lacking. The program brings together the diverse areas that are necessary to address these pro- blems. One example and direct result of the interdisciplinary collaboration fostered by MRCAS is the unique image guided surgical navigation system called Hip Nav (for Hip Navigation System) that has been developed to accurately mea- sure and guide alignment of implants during total hip replacement surgery. HipNav has three components. The first component is a preoperative plan- ner and simulator in which the surgeon can pick the appropriate implant size and optimal position of the femoral and acetabular components given the patient’s specific anatomy. The second component is a range of motion simu- lator that displays and animates the range of motion of the hip and impin- gement conditions for any position of the patient’s leg. The range of motion simulator permits the surgeon to opti- mize the position of the implants in order to reduce the chance of impin- gement and dislocation for any indivi- dual patient. (fig. 2) fig. 2 - Surgical planner and Range of motion simulator for total hip replacement: Limits of leg motion are interactively animated for selec- ted implants and leg motion paths. The third component is an intraopera- tive navigational system then allows the surgeon to measure and accurately place the implant in this “ideal” posi- tion. The expectation is that proper implant alignment will not only reduce the risk of dislocation, but will improve overall hip mechanics and reduce the chance of longer term problems like the generation of wear debris due to impingement. In addition, these tech- nologies will permit the development of minimally invasive surgical tech- niques, which will improve the short and long-term outcomes of our patients (fig. 1). In April of 1997, we began a clinical trial using HipNav. The clinical infor- mation that we are collecting has been very enlightening and provided mea- surements which surgeons never had available before. One of the most important contributions of HipNav and other computer-assisted technolo- gies is providing surgeons and clinical researchers with an accurate intraope- rative measurement tool. For instance, with HipNav we can for the first time intraoperatively track (in real time) the movement of the patient’s bony ana- tomy during all phases of surgery. Furthermore, we can measure the final position of the implants. These measu- rements will permit us to directly relate surgical technique to patient out- comes. HipNav technology has also enabled the development of less inva- sive surgical techniques while impro- ving accuracy. Our program is at the forefront of seve- ral other areas of active research and development that we expect to directly impact surgical practice in the near future. We have developed, demonstra- ted and hope to soon clinically use an image overlay system which permits the display of medical images on the patient during surgery that in essence gives the surgeon “x-ray vision” (fig. 3a, 3b). fig. 3a: Image overlay visualization system- giving the surgeon “X-ray vision” fig. 3b - Image overlay system displays medical images and preoperative plans overlaid on the patient. In this case, the surgeon can “see through” the patient permitting display of a pelvic CT and planned acetabular implant orientation. We have also extended the enabling techniques used in HipNav to surgical navigation around the knee. KneeNav October 2000 - N°2 ARGOS SpineNews 33
  27. 27. focus on The Robotics Institute will be used clinically in the coming months to assist surgeons in perfor- ming total knee replacement (TKR) and anterior cruciate ligament recons- tructions (ACL). We began a collaborative program with Dr Freddie Fu (Chairman of the Orthopaedic Department at the University of Pittsburgh) to develop an ACL/PCL surgical navigation module for KneeNav. A randomized study on sawbones was already performed to compare the accuracy of KneeNav with a traditional arthroscopic technique. KneeNav system improved reliability and repeatability of ACL reconstruc- tion. Surgical error was significantly less important using the computer assisted system. About four computer- assisted procedures were sufficient for experienced surgeons involved in the experiment to become proficient with the technique. This computer-assisted ACL navigation system has the poten- tial to reduce surgical error and varia- tion from optimal graft alignment. Subsequent studies will focus on improved models and clinical use as a measurement tool first and then as a complete navigation system. fig. 4 - Sagittal cut plane of the virtual ACL. In parallel, a KneeNav-TKR system being developed at UPMC Shadyside Hospital. During alignment of the cut- ting jigs the surgeon views a video monitor that displayed the current position of the traditional guides rela- tive to the femur and tibia. The sur- geon slides a pre-calibrated “plate- probe” tracker, into the usual saw slot of the mechanical guides. A video monitor provides intra-operative mea- surements of alignment and guidance information. Specific user interfaces represent predefined mechanical axes, which are the surgical frame of refe- rence and serve for cutting guide orientations. The surgeons are then able to measure their surgical practice, and also ideally orient the cutting guides relative to the mechanical axes. Bone cuts are done in the usual manner using an oscillating saw, and the surgeon can then check the cutting plane using the same plate-probe. The implants are then secured, and the surgeon verifies soft tissue balancing and alignment using specific interfaces simultaneously displaying relative bone movement. First experiments proved feasibility, repeatability and reliability of this computer-assisted knee system. An IRB (Institutional Review Board) approval has been granted and will allow us to assess the system in clinical trial. Several studies are already scheduled to use KneeNav as a measurement tool or compare it to other current commercial product (as Orthopilot system). fig. 5 - KneeNav-TKR. The TV monitor dis- plays simultaneously bones, mechanical axes overlaid and cut orientation. We are also developing robotic mani- pulators and microelectromechanical systems (MEMS) which will embody the next generation of surgical tools and measurement devices. These tools will eventually permit more accurate and less invasive surgical procedures all to the benefit of our patients. Measuring Patient Outcomes: The Total Joint Registry Improvements in current medical procedures require the evaluation of clinical results and patient outcomes. The costs of new technologies must be weighed against the benefits, potential savings and improved clinical outcomes, especially in today’s healthcare environment. The Total Joint Registry has developed a database to evaluate clinical and patient-perceived outcomes following total joint replacement surgery. The Total Joint Registry includes a general clinical database to facilitate the evaluation of joint reconstruction procedures. Candidates for the Registry include any patients under- going total hip or total knee replace- ment surgery. Patients are evaluated preoperatively, as well as postoperati- vely at 3 months, 6 months, 1 year and annually thereafter. The information is collected prospectively and by an inde- pendent observer and includes the Harris Hip Score or Knee Society Score, the SF-36 Health Status Survey, and a Hip/Knee Outcomes Data Collection Instrument. In addition to these clinical and patient reported outcome measures, the Registry data can be used to track real costs (as oppo- sed to hospital charges) of total joint replacement surgery, as well as costs associated with the treatment of com- plications and required revision sur- gery. The Total Joint Registry will provide a pool of data for comparison and deter- mination of clinical outcomes from sur- geons’ and patients’ perspectives. This outcomes information can also be used to develop a mechanism to evaluate new surgical interventions and tech- nologies in total hip and total knee arthroplasty, in terms of patient out- comes, surgical outcomes and cost effectiveness. The goal of the Total Joint Registry and our clinical out- comes project is to develop a resource 34 ARGOS SpineNews N°2-October 2000
  28. 28. focus on The Robotics Institute upon which surgeons can draw to assist them in the clinical decision making process. This will promote increased accuracy and efficiency in orthopaedic practice improving patient outcomes through continuous process improve- ment ensuring quality patient care. To date, the Total Joint Registry has enrolled over 330 patients. In addition, the Registry will be open to all patients from interested orthopaedic surgeons in the Pittsburgh area, thus increasing the pool of patient information avai- lable for clinical research studies. Ultimately, this standardized outcomes database will permit comparison of patient outcomes from multiple sur- geons and medical centers. A New Industrial Base We are entering an era of increased potential for the commercialization of computer assisted surgical tools and related technologies. If we are to realize the potential for improving patients’ outcomes, the commercialization of these emerging technologies will be an important step towards making these tools available to a broader surgical audience and in turn help more patients. This step will be important to the longer term sustainability of the entire area of computer integrated surgery and holds the potential to establish Western Pennsylvania as a worldwide leader not only in research and development, but also in transferring technology to the commercial sector resulting in a new industrial base for Pittsburgh and Western Pennsylvania. Towards these ends, CASurgica, Inc. was recently established as the commercial limb of the MRCAS program with the goal to commercialize the next generation of Computer Assisted Surgical tools and technologies. The Impact on Healthcare Delivery in Pittsburgh and the Nation Our program is positioned to establish an example for the country on how continuous process improvement and computer assisted tools could result in high quality, cost-effective healthcare provided in a patient friendly environ- ment. In addition, our program has the opportunity to be both a regional and global authoritative body concerning clinical care and research in these areas. Clinical and basic science research funding would be increased because of the focus on solving real cli- nical problems. Finally, the opportuni- ties in technology transfer and partne- ring with commercial entities would lead to establishment of a new indus- trial base for Pittsburgh and Western Pennsylvania. Our team effort, through the existing interdisciplinary MRCAS clinical and research programs and educational activities is uniquely positioned to achieve all of these goals making the Pittsburgh region an international lea- der in the areas of medical robotics, surgical navigation and computer assis- ted surgical technologies and a clinical center of excellence that will be known locally, nationally and internationally. Contact Information: Upcoming MRCAS Related Educational Activities Educational activities play a significant role in raising awareness of computer assisted surgical technologies, and exchanging information about the state of the art, current research and deve- lopment. The fourth annual North American Program on Computer Assisted Orthopaedic Surgery (CAOS/USA 2000), will be held from June 15 to 17, October 2000 - N°2 ARGOS SpineNews 35 Contact information If you would like additional information or if you would like to visit our MRCAS pro- gram, please call: (412) 623-2673 or explore our web sites at or contact: Dr Anthony M. DiGioia Research Office: Centers for Medical Robotics & Computer Assisted Surgery UPMC Shadyside 5200 Centre Avenue, Suite 309, Pittsburgh, PA 15232 Phone (412) 623-2673 Fax (412) 623-1108 MRCAS Team Members at Carnegie Mellon University and UPMC Shadyside: Laura Cassenti Karen Cwynar Anthony M. DiGioia III, MD Kaigham Gabriel, PhD Branislav Jaramaz, PhD Takeo Kanade, PhD Richard LaBarca, MS Timothy J. Levison, MS Yanxi Liu, PhD James Moody, MS Patrick Muir, PhD Constantinos Nikou, MS Frederic Picard, MD Cameron Riviere, PhD
  29. 29. focus on The Robotics Institute 2000 in Pittsburgh. Dr DiGioia will chair CAOS/USA 2000. The Program will emphasize state of the art techno- logies and perspectives on the rapidly evolving field of computer assisted orthopaedic surgery. The conference is designed for practicing orthopaedic surgeons and will educate participants on computer assisted and image gui- ded surgical techniques and robotic assistive devices. CAOS/USA will also present the most current views on the impact of computer assisted surgical techniques on the clinical and surgical routine in several orthopaedic subspe- cialties and promote a new partnership between surgeons, technologists, and industry as a critical foundation for the successful integration of these tech- niques into routine clinical practice. Dr DiGioia will also co-chair the third international Medical Imaging, Computing, and Computer Assisted Intervention (MICCAI) conference on medical robotics, imaging and compu- ter assisted in Pittsburgh, October 11- 14, 2000. Topics to be addressed at the event include clinical applications of computer technologies and systems, computer-assisted intervention sys- tems and robotics, as well as medical imaging and computing for multiple surgical and medical subspecialties. For information on the CAOS/USA 2000 event visit and for MICCAI 2000 visit For additional information on CAOS/USA 2000 and MICCAI 2000, you can also contact: Preferred Meeting Management, Inc. 2320 6th Avenue, San Diego CA 92101-1643, USA Phone (619) 232-9499, Fax (619) 232-0799 Establishment of the International Society for Computer Assisted Orthopaedic Surgery (CAOS-International) The area of computer assisted ortho- paedic surgery has become so active worldwide that it was time for a for- mation of a society that will enable exchange of ideas and contacts and serve to facilitate future collabora- tions. Dr Anthony DiGioia and the MRCAS program in conjunction with Dr Lutz Nolte from the University of Bern-M.E. M¸ller Institute were ins- trumental in establishing the first ever International Society for Computer Assisted Orthopaedic Surgery (CAOS- International). The Society will have headquarters in Bern, Switzerland and the North American office will be hou- sed at UPMC Shadyside Hospital. Dr DiGioia is a founding member and was elected as the Inaugural First Vice- President of the Society. Dr Branislav Jaramaz, also from the MRCAS pro- gram, will serve as Treasurer. The First CAOS-International Conference will be held in Davos in 2001. The 2002 meeting will be in North America and hosted by Dr DiGioia. The purpose of this non-profit organi- zation is to bring together those indi- viduals throughout the world, who, by their contributions and activities in the areas of research, clinical study, and cli- nical use, have or are interested in computer assisted orthopaedic sur- gery. Its further purpose will be to serve as a forum for the exchange of information of both an investigative and clinical nature which relates to preoperative planning, intraoperative execution, postoperative follow up and clinical outcomes by means of compu- ter assistance. The Society also aims to promote a new partnership between orthopaedic surgeons and technolo- gists as a necessary basis for the suc- cessful integration of computer assisted surgical tools and techniques into the daily clinical routine. For information on the CAOS- International/USA 2000 event visit American Academy of Orthopaedic Surgery Establishes a Special Interest Group on Robotics and Computer Assisted Orthopaedic Surgery (RCAOS) The American Academy of Orthopaedic Surgeons (AAOS) has recognized the potential impact of computer assisted surgical tools and related innovations on surgical prac- tice. An AAOS sponsored Robotics and Computer Assisted Orthopaedic Surgery/Special Interest Group (RCAOS/SIG) has been established by Dr DiGioia in 2000. RCAOS will sup- port the exchange of information in state-of-the-art techniques and pers- pectives in this rapidly evolving field including the areas of robotics, surgical simulators and planners, intra-opera- tive navigational systems and hybrid reality. The first RCAOS/SIG Meeting was held during the recent 2000 AAOS Conference and attended by an enthu- siastic group. RCAOS/SIG is open to all orthopaedic surgeons and will assist participants to more effectively understand and relate robotics, image guided and computer assisted surgical systems to clinical orthopaedic practice; demonstrate cur- rent clinical applications using RCAOS technologies; obtain an international perspective on the current state-of-the- art as well as future developments planned for computer assisted surgery systems; and identify the clinical and technical issues and trends in robotics and computer assisted surgery. ■ Dr Anthony DiGioia 36 ARGOS SpineNews N°2-October 2000
  30. 30. An 89-year-old woman presented with intractable low back pain and weakness in the L5 innervated musculature. She also complained of neurogenic claudi- cation after ambulating for 50 meters. Lateral radiographs revealed multile- vel disk degeneration at L2-L3, L3-L4, and L5-S1. There was a degenerative spondylolisthesis at L4-L5 but normal alignment on the AP view. Lateral myelography revealed a com- plete block at L5 and multilevel central and foraminal stenosis was confirmed by CT scan. In light of the patient’s age, we attempted to perform as mini- mal of a surgical procedure as possible. The procedure consisted of a decom- pressive laminectomy from L2-L5 aug- mented by fusion of the unstable seg- ment (L4-L5) with Twinflex instrumentation. ■ Christian Mazel, MD Head of the Orthopaedic and Spinal Surgery department Institut Mutualiste Montsouris 42, boulevard Jourdan 75014 Paris FRANCE Phone +33 1 56 61 62 63 Fax +33 1 56 61 63 37 38 ARGOS SpineNews N°2-October 2000 Degenerative spondylolisthesis associated with lumbar stenosis By Dr Christian MAZEL (IMM Choisy - PARIS) ■ clinical cases AP/lateral preoperative x-ray AP/ lateral postoperative x-ray AP/lateral preoperative myelography CT scan
  31. 31. clinical cases A 56-year-old woman presented with a six-month history of left-sided sciatica, neurogenic claudication, and a foot drop. She also noted shooting pains with any sudden change of position, which were interpreted as evidence of dynamic instability. Radiographic examination revealed severe disk degeneration at L5-S1, early degeneration at L3-L4 with slight anterolisthesis, and severe stenosis of the left L5-S1 foramen. EMG confir- med compression of the left L5 nerve root and dynamic radiographs showed instability at L3- L4, and L4-L5. On October 18, 1995, wide left L5-S1 laminotomies were performed for decompression. Fusion from L3 to the sacrum was performed using Twinflex instrumentation. Three months postoperatively the patient was able to walk for an hour without pain, and at 12 months’ follo- wup, the fusion had consolidated, although the lumbar lordosis had not been completely restored. The patient was quite satisfied with her outcome despite some mild persistent bilateral sacroiliac discomfort. ■ Philippe Bedat, MD Cabinet médical 36, avenue Théodore Weber 1208 Genève SWITZERLAND Phone +41 22 736 0902 Fax +41 22 736 0494 October 2000 - N°2 ARGOS SpineNews 39 Lumbar canal stenosis and instability By Dr Philippe BEDAT (Genève SWITZERLAND) ■ Post-operative X-rays Preoperative functional saccoradiculography
  32. 32. technologies New X-ray detector Millions of x-rays are performed each year. For instance, the treatment of a child with scoliosis requires as many as four x-rays per year. However, radiography is not a harmless procedure, as it must be remembered that considerable doses of irradiation are absorbed by the human body. CONSEQUENTLY, since the beginning of the 1980s, some efforts have been devoted to designing systems based on digital amplifiers and laser images in which conventional films are replaced by photosensitive cassettes. These devices reduce the irradiation dose by twenty per cent. The government agencies have also stressed the importance of medical radiation exposure, with recent EUR- ATOM recommendations from ICPR and the european community. The work conducted by Georges Charpak (Nobel Prize for Physics in 1992) on the proportional multiwire chamber has led in the early nineties to a low dose prototype which was clinically tested at Hopital St Vincent de Paul, Paris, on children and teenagers. The study showed unambiguously the capa- city of the prototype to provide good quality radiographic images at a patient dose reduced by up to 20 times. The original feature of this apparatus is its detector, a proportional multiwire chamber, designed and developed by Charpak for nuclear physics experi- ments at CERN, for which he was awarded the Nobel Prize for Physics in 1992. The device is based on the detec- tion of X rays in a gaz, here xenon and CO2, conversion into electrons and subsequent amplification. Its major dif- ference with other X ray detectors is its sensitivity to individual X photons, making it a great detector for low dose exposures. The detector is linear, and is scanned together with the X ray tube along the region of interest. To reduce all radiations due to scatter, two linear collimators ensure a flat fan beam that is perfectly adjusted to the linear detector dimensions. That method allows a total suppression of scatter, as only the slice of the body that is expo- sed at a given time receives radiation. In the prototype tested in 96, each pixel of the detector was made of a 5 cm long wire connected to an amplifier, discriminator and counter. The wire pitch was 1,2 mm, resulting in a reso- lution of about 0,6mm after signal pro- cessing. The digital data are then accu- mulated and displayed on a personal computer for clinical analysis. All fea- tures of a digital system, such as auto- matic density measurements, distance measurements and digital zoom are available with such a system. The detector is a true digital one, where there is no need for digitization or laser scanning. Data from the detector can also be easily integrated into conven- tional digital radiology systems (repro- duction, transmission, filing, etc.). Biospace, the company created by Charpak to derive biomedical imaging systems from innovative detector tech- nologies, is currently developing a new system for low dose radiology. Using a new patented technology based on micropattern detectors, the new system will have the low dose fea- tures of the first protoype together with a higher resolution and scanning speed. The product in development is a two heads instrument, in which two simultaneous, perpendicular (front and side) X ray radiographs are taken. For spine examinations, the pratician will have the possibility to analyze these two planar views as well as a tridimen- sional reconstruction of the spine, a feature currently developed by the Laboratoire de Biomécanique of ENSAM, Paris in collaboration with Biospace. First results with the new detector technology showed unprece- dented high morphometric precision in the 3D reconstruction of vertebrae. Besides being a low dose radiology equipment, the new development could be a good alternative to highly irradia- ting CT scan exams for spine exams. ■ 44 ARGOS SpineNews N°2-October 2000 Nobel Prize Winner, Pr Georges Charpak contribution to medicine A new X-ray detector from nuclear physics
  33. 33. communication What is Biomechanics ? Thank you for your contribution ! We will see you next year… 46 ARGOS SpineNews N°2-October 2000
  35. 35. 48 ARGOS SpineNews N°2-October 2000 OOrrggaanniizzaattiioonn cchhaarrtt Christian Mazel, MD President Jean-Paul Forthomme, MD Vice President Alexandre Templier, Msc, PhD General manager Pierre Kehr, MD Executive secretary Alain Graftiaux, MD Treasurer Communication committee Training committee Evaluation committee Wafa Skalli, PhD President of the committee Jacques De Guise, PhD Michel Dutoit, MD Alain Graftiaux, MD Christian Mazel, MD Juan Antonio Martin, MD Henry Judet, MD Philippe Bedat, MD Pierre Kehr, MD Charles-Marc Laager, PhD Jean-Paul Forthomme, MD Henri Costa, MD Jean-Paul Steib, MD President of the committee Jean-Paul Forthomme, MD Franck Gosset, MD François Lavaste, PhD Richard Terracher, MD Jean-Marc Vital, MD