DEPARTMENT OF ORTHOPAEDICS J.J.M .MEDICAL COLLEGE, DAVANGERE SEMINAR TOTAL HIP ARTHROPLASTYMODERATORS: PRESENTED BY:Dr.RAVINATH M.S.,(ORTHO) Dr. ASHOK .J. SAMPAGAR. P.G. In orthopedicsDr.MALLIKARJUNREDDYM.S.,(ORTHO ) DATE: 14-09-2011
INTRODUCTION :• Total hip arthroplasty is an operative procedure in which the diseased and destroyed hip joint is resected and replaced with a new bearing surface.• Patients with arthritis can now look to THA with the object of maintaining stability, while relieving pain, increasing mobility and correcting deformity.• MOST SIGNIFICANT BREAK THROUGH OF THE 20Th CENTURY
HISTORY AND EVOLUTION OF THR• In 1912, Sir Robert Jones used Gold Foil as an inter positional layer, other materials used were muscle, fascia, skin, oil, rubber, celluloid, pig bladder.• In 1923, SMITH-PETERSON introduced the concept of mould arthroplasty• In 1933, PYREX GLASS was chosen as the material for the first mould..• In 1937, Venable and Stuck developed VITTALIUM (an alloy of Cobalt 65%, Chromium 30%, Molybdnium 5%).
• In 1950, JUDET and BROTHERS used acrylic femoral head prosthesis made of methyl methacrylate..• In 1952 AUSTIN MOORE and FRED THOMPSON independently conceived the idea of fixing endoprosthesis.• The 1950, WRIST, RING, Mc. KEE-FARRER and others designed the metal on metal total hip arthroplasty but did not prove satisfactory because friction and metal wear
• In 1960, Late Sir John Charnley has done pioneer work in all aspect of THA, including the concept of low frictional torque arthroplasty, surgical alteration of hip biomechanics, lubrication, materials, design and clear air operating room environment.
• Between 1966-1988,Maurice Muller from Switzerland developed a plastic acetabular cup with a 32 mm diameter chromium- cobaltmolybdenum femoral head.• In 1964,Peter Ring began using metal-to-metal components without cement,• concept of modular prosthesis developed during 1970• cementless prostheses came in to picture by mid 1980
ANATOMY OF HIP JOINT• Head of femur articulates with the acetabulum of pelvis to form hip joint• This is a ball and socket variety of synovial joint.• The range of movements which permits is less than that of shoulder joint, but the strength and stability are much greater.
Head of the femur :• Head of femur forms more than a half of a sphere, and is covered with hyaline cartilage except at the fovea capitis.• directed upwards, medially and slightly forwardsThroughout ROM:• 40% of femoral head is in contact with acetabular articular cartilage.• 10% of femoral head is in contact with labrum.
Acetabulum• It is hemispherical cavity on the lateral aspect of the innominate bone and directed laterally downwards and forwards• Acetabulum is formed by all the components of the hipbone- ilium , ischium, pubis
• Hip joint is unique in having a high degree of both stability as well as mobility• The stability or strength depends upon : – The depth of acetabulum which is increased by the acetabulur labrum. – The strength of the ligaments and the surrounding muscles. – Length and obliquity of the neck of femur which increases the range of movement
Ligaments :They are :• Fibrous capsule• Iliofemoral ligament or ligament of bigelow• Pubo-femoral ligament• Ischio-femoral ligament• Ligamentum teres• Transverse ligament of acetabulum
Neck shaft angle or angle of inclination• It is the angle between the axis of the femoral neck and the long axis of the femoral shaft.• On average, it is 135 degrees in the adults
Anteversion or angle of femoral torsion• Refers to the degree of forward projection of femoral neck from the coronal plane of the femoral shaft.• In an adult, it is about 10-15 degrees
APPLIED BIOMECHANICS• The total hip component must withstand many years of cyclical loading equal to atleast 3 to 5 times the body weight and at time they may be subjected to overloads of as much as 10 to 12 times the body weight• So, the basic knowledge of biomechanics of the THR and hip is necessary to properly perform the procedure, to successfully manage the problems that may arise during and after surgery, to select the components.
• The ratio of the length of the lever arm of the body weight to that of the abductor musculature is about 2.5:1.• So the force of the abductor muscles must approximate 2.5 times the body weight to maintain the pelvis level when standing on the one leg.• The estimated load on the femoral head in the stance phase of gait is atleast 3 (5/6 BW on femoral head )times the body weight.
Forces acting on hip• To describe the forces acting on the hip joint, the body weight may be depicted as a load applied to a lever arm extending from the body’s center of gravity to the center of the femoral head.• The abductor musculature, acting on lever arm extending from the lateral aspect of the greater trochanter to the center of the femoral head.
• Force on hip act in coronal and saggital direction• Coronal- tend to deflect stem medially , saggital(esp in flexed hip)- tend to deflect stem posteriorly• Hence Implanted femoral components must withstand substantial torsional forces even in the early postoperative period
CHARNLEY’S LOW FRICTION ARTHROPLASTYCharnley advocated the shortening of the body weight lever arm by• Deepening the acetabulum and by using small head. Lengthen the abductor lever arm by• Reattaching the osteotomised greater trochanter laterally or• By increasing offset between the head and stem of the femoral component.
Centralisation of head and lengthening of abductor lever arm• Whenever abductor lever arm is increased, it reduces forces on the hip joint. This lowers the friction and frictional torque and hence lessens the chance of wear and loosening of implants.
Valgus and Varus position• A valgus of the head and neck of the femoral component relative to the femoral shaft more than 140 degree decrease the movement of bending and increase proportionally the axial loading of the stem• A mild degree of valgus is usually desirable, but it does shorten the abductor lever arm mechanism and also tend to lengthen the limb,may result in the valgus strain on the knee.• varus position of the head and neck segment of the femoral component must be avoided because it increases risk of loosening,wearing and stem failure.
Stress Transfer to Bone• A major concern with THR is that adaptive bone remodeling arising from stress shielding compromises implant support, produces loosening, and predisposes to fracture of the femur or the implant itself.• Cementless stems generally produce strains in the bone that are more physiological than the strains caused by fully cemented stems• Increasing the modulus of elasticity, the stem length, and the cross-sectional area of the stem increases the stress in the stem, but decreases the stress in the cement and proximal third of the femur.
Stem failure :• Breaks in the area of maximal tensile stress. Depends on design of the stem, direction of the load applied( varus/valgus)• The area of maximal tensile stress is near or at point where a line drawn through the center of the head and neck will intersect one drawn on the lateral edge of the distal half of the stem.• Decreased with the advent of newer stem design with greater cross-sectional dimensions, stronger metals and improved cement techniques.
Head and nec k diameters :• The neck with the smaller head tends to impinge on the edge of the cup during a shorter arc of motion which tends to loosen the components and dislocate the joint.• The deep socket and beveled edges and the greater diameter of the head in comparison to the neck are the features that allow a greater range of motion.
Coefficient of friction and frictional torque :• CE of friction is the measure of the resistance encountered in moving one object over the other.• It depends on the material used, the finish of the surfaces ,temperature and the lubricant. – CE for normal joint- 0.008 to 0.02. – CF of metal on metal - 0.8 – CF of metal on HDPE (High density poly ethylene) - 0.02
• A frictional torque force is produced when the loaded hip moves through an arc of motion. It is product of the frictional force times the length of the lever arm i.e., the distance of given point on the surface of the head moves during arc of motion.
• Frictional force depends on coefficient of friction, applied load and also on the surface area of contact between the head and socket.• FT will increase with large size head.• Theoretically it causes loosening of components.
WEAR :Wear can be defined asthe loss of material fromthe surfaces of theprosthesis as a result ofmotion between thosesurfaces. Material is lost inform of particulate debris. Types : Abrasive-THR Adhesive -THR Fatigue - TKR
The factors that determine wear are :• CF of the substance and finishing surfaces• Boundary lubrication• Applied load• The sliding distance per each cycle• The hardness of the material• The number of cycles of movements The area of greater wear is in the superior aspect of the socket where the body weight is applied to the femoral head.
• Wear is difficult to measures accurately, it may be measured by depth of penetration of the head with in the cup or the volume of debris produced or by a change in the weight of the polyethylene• Newer methods- digitized x-rays and computer assisted wear measurements• higher in younger and more active male patients.• Wear of more than 4 mm may result in neck impingement on the edge of the cup and secondary loosening of the acetabulum.
BIOMECHANICAL CONSIDERATIONS IN THR :• Lengths of the lever arm can are surgically changed to approach r ratio of 1:1 (which reduces the hip total load by 30 % ).• Abductor lever arm can be increased either by increasing the medial offset of the femoral component or lateral / distal reattachment of greater trochanter.• Joint reaction forces are minimal if hip center is placed in anatomical position.• Adjustment of neck length is important as it has effect on both medial offset and vertical offset. Neck length typically ranges from 25 to 50 mm.
• Femoral components must be produced with a fixed neck shaft angle typically about 1350.• Restoration of the neck in coronal plane Increased anteversion – anterior dislocation Increased Retroversion – posterior dislocation• Socket depth and beveled edges and greater diameter of head in comparison of neck allow greater range of motion.
•Neck diameter should approach that to makeneck stronger especially with small femoral heads.•Frictional torque of small head will be lesscompared to larger head.•Increasing stem length and cross sectional areaincreases the stress in the stem.•Any loading of proximal medial neck likely todecrease bony resorption and reduces stresses oncement.•Loose fitted stem – increase stresses in proximalfemur.
INDICATIONS FOR THA :• The primary indication for THA is incapacitating PAIN. Pain in the hip in the presence of destructive process as evidenced by X-ray changes is an indication.• THA is an option for nearly all patients with diseases of the hip that cause chronic discomfort and significant functional impairment.• Patients with limitation of movement, leg length inequality and limp but with little or no pain are not the candidates for THR.
• Arthritis Rheumatoid Juvenile rheumatoid (Still disease) Ankylosing spondylitis• Degenerative joint disease (osteoarthritis, hypertrophic) Primary Secondary Slipped capital femoral epiphysis Congenital dislocation or dysplasia of hip Coxa plana (Legg-Calvé-Perthes disease) Paget disease Traumatic dislocation Fracture, acetabulum Hemophilia
• Osteonecrosis Postfracture or dislocation Idiopathic Slipped capital femoral epiphysis Hemoglobinopathies (sickle cell disease) Renal disease Cortisone induced Alcoholism Caisson disease Lupus Gaucher disease Nonunion, femoral neck and trochanteric fractures with head involvement• Pyogenic arthritis or osteomyelitis Hematogenous Postoperative
• Tuberculosis• Congenital subluxation or dislocation• Hip fusion and pseudarthrosis• Failed reconstruction Osteotomy Cup arthroplasty Femoral head prosthesis Girdlestone procedure Total hip replacement Resurfacing arthroplasty• Bone tumor involving proximal femur or acetabulum• Hereditary disorders (e.g., achondroplasia)
• Most common reasons for total hip replacement: • Osteoarthritis 60 % • Rheumatoid arthritis 7 % • Fractures/dislocations 11 % • Aseptic bone necrosis7 % • Revision 6 % • Other 9%
CONTRAINDICATIONS :Absolutea) Patient with unstable medical illness that wouldsignificantly increase the risk of morbidity andmortality.b) Active infection of the hip joint or anywhere elsein the body.Relative• Any process that is rapidly destroying bone eg.neuropathic joint, generalized progressiveosteopenia.• Insufficiency of abductor musculature.• Progressive neurological disorder.
Hip Replacement Components• Acetabular component - consists of two components – Cup - usually made of titanium – Liner - can be plastic, metal or ceramic • Femoral components Head Neck stem
FEMORAL COMPONENTS :• Neck length and offsets : The ideal femoral reconstruction reproduces the normal center of rotation of femoral head, which can be determined by -Vertical height (vertical offset) -Medial head stem offset ( horizontal offset) -Version of the femoral neck (anterior offset)
• Vertical offset- LT to center of the femoral head. Restoration of this distance is essential in correction of leg length.• Medial head stem offset- distance from the center of the femoral head to a line through the axis of the distal part of stem.• Medial offset if inadequate, shortens the moment arm – limp, increase, bony impingement and dislocation.• Excessive medial offset –increase stress on stem and cement which causes stress fracture or loosening.• Version of the femoral neck : important in achieving stability of the prosthetic joint. The normal femur has 10-15 degree of anteversion.
CLASSIFICATION OF TOTAL HIP FEMORAL COMPONENTS :• Cemented : Charnely,Matche Brown,Muller ,alandruccio ,Aufranc – Turner ,Sarmiento,Harris• Non cemented – Press Fit : Judet ,Lord ,Sivash , Porous Metal : Harris ,Galante,Hydroxyappatite coated• Bipolar--Bateman ,Gilibertz ,Talwalkar• Ceramic –Mittelmeir• Polyacetate -Bombelli Mathes• Custom made• Modular System
• Range of head sizes – 22, 26, 28 & 32 mm.• Incidence of dislocation is higher for smaller head.• Neck diameter : Original charnleys was 12.5 mm but has been reduced to 10.5 mm – reduced neck diameter avoids impingement during flexion and abduction.• Range of stem lengths -120 mm to 170 mm.• The main problem is mechanical loosening and extensive bone loss associated with fragmented cement
Basic principle• Based on the principle-bone ingrowth from the viable host bone into porous metal surfaces of implant.• Indications for cementless components involves 1.primarily active young patients 2.and revisions of failed cemented components.
• Two prerequisites for bone ingrowth1.immediate implant stability at the time of surgery2.and intimate contact between the porous surface and viable host bone• Implants must be designed to fit the endosteal cavity of the proximal femur as closely as possible.• In general, the selection of implant type and size, as well as the surgical technique and instrumentation, must all be more precise than with their cemented counterparts
Current porous stem designs• 1.titanium alloy with a porous surface of commercially pure titanium fiber-mesh or beads• and (2) cobalt-chromium alloy with a sintered beaded surface.• 2 shapes- Cementless total hip stems are of two basic shapes: straight and anatomical• The aim of both types is to provide optimal fit both proximally and distally and thereby achieve axial and rotational stability by virtue of their shape
Types of porous coated stems• Circumferential porous coating-first generation femoral stems• Extensive coated stems• Proximally coated stem – twice the incidence of thigh pain(stem tip abutment on the anterior cortex of femur)• Tapered femoral stems• Stems with hydroxyapetite coatings
NON POROUS CEMENTLESS FEMORAL COMPONENTS• nonorous femoral implants have surface roughening that provide a macrointerlock with bone• No capacity for bone ingrowth but provides lasting implant stability• With the concerns about fatigue strength, ion release and adverse femoral remodeling, these non porous stems came into use over porous stems
Advantages of cementless femoral stem prosthesis• No cement required and problem related to cement to bone and cement implant interface reduced• In young active patients• Decreased incidence of asceptic loosening• Less bone destruction• Circumferential porous coating of proximal stem provide effective barrier to ingress debris particle and thus limit early development of osteolysis of distal stem
ACETABULAR COMPONENTS :• The articulating surface of all acetabular components is made of UHMWPE. Most systems feature a metal shell with an outside diameter of 40 to 75 mm which is mated to a polythene liner.• optimum position for the prosthetic socket which should be inclined 45⁰ or less to maximize stability of the joint.(normal 55⁰)Types :• Cemented acetabular components.• Cementless acetabular components.• Custom made acetabular components
CEMENTED ACETABULAR COMPONENTS• Original sockets- thick walled polyethylene cups. Vertical and horizontal grooves on external surface to increase stability within the cement mantle• wire markers were embedded in plastic to allow better assessment of position on postoperative roentgenograms.• More recent designs have a textured metal back which improves adhesion at the prosthesis cemented interface. A flange at the rim improves pressurization of the cement.• used in elderly patients, tumour reconstruction and the circumstances with less chances of bony ingrowth as in revision THR.
Cementless Acetabular Components• Most cementless acetabular components are porous coated over their entire circumference for bone ingrowth• Fixation of the porous shell with transacetabular screws
• Pegs and spikes driven into prepared recesses in the bone provide some rotational stability but less than that obtained with screws.
• ZTT socket Hemispherical , porous coated cup designed with dome screw holes and transacetabular screws for stability. Six peripheral screw holes provide choice of screw locations for additional stability and also lock in the polyethylene insert.
Two techniques involved1.Initial stability of the metal shell against the acetabular bone using screws, spikes , lugs, or fins2. Stratch fit- underream the acetabular bone bed by 1-2 mm and use the roughness of the outer surface of metal shell to achieve scratch fit• Expansion cup method-Cup diameter is reduced with with a special instrument , cup then implanted and then allowed to return to initial diameter.
polyethylene liner• Most modern modular acetabular components are supplied with a variety of polyethylene liner choices• The polyethylene liner must be fastened securely to the metal shell.• Current mechanisms include plastic flanges and metal wire rings that lock behind elevations or ridges in the metal shell, and peripherally placed screws• in vivo dissociation of polyethylene liners from their metal backings has been reported micromotion between the nonarticulating side of the liner and the interior of the shell may be a source of polyethylene debris generation, or “backside wear.”
Alternative Bearings• Osteolysis secondary to polyethylene particulate debris has emerged as the most notable factor endangering the long-term survivorship of total hip replacements.• alternative bearings have been advocated to diminish this problem• These are- -highly cross linked polyethylene -metal-on-metal -ceramic-on-ceramic -Ceramic on Polyethylene
Highly Cross-Linked Polyethylene• Higher doses of radiation(gamma or electron,10mrad) can produce polyethylene with a more highly cross-linked molecular structure.• This material has shown remarkable wear resistance.• Only short-term data on the performance of highly cross-linked polyethylenes are presently available• Diadvantage -lower fracture toughness and tensile strength
Metal-on-Metal Bearings• Metal-on-metal implants seem to be tolerant of high impact loading, and mechanical failure has not been reported.• wear rates less than 10 mm/y for modern metal- on-metal articulations• But there remains major concern regarding the production of cobalt and chromium metallic debris, and its elimination from the body.• metal-on-metal (MOM) bearings have a ‘suction- fit’ less chance of dislocation (J Bone Joint Surg [Br] 2003;85-B:650-4)
Ceramic-on-Ceramic Bearings• Alumina ceramic has many properties that make it desirable as a bearing surface in hip arthroplasty• high density- surface finish smoother than metal implants• The hydrophilic nature- ceramic promotes lubrication• Ceramic is harder than metal and more resistant to scratching from third-body wear particles.• The linear wear rate of alumina-on-alumina has been shown to be 4000 times less than cobalt-chrome alloy– on–polyethylene.• Ceramic-on-ceramic arthroplasties may be more sensitive to implant malposition than other bearings. (J Bone Joint Surg [Br] 2003;85-B:650-4
EVALATION BEFORE SURGERY• Evaluate whether pain is sufficient to justify surgery.• Assess patient’s general condition (thorough medical examination with laboratory test is must)• Investigate for any ongoing infection• Physical examination of spine, both lower limbs, soft tissue around the hip.• Assess the strength of abductor mechanism• Any fixed flexion deformity assessed.• Limb length• Neurological status
• When both the hip and knee are arthritic usually hip should be operated first because THR alters the knee mechanics.• If bilateral involvement present operate on most painful hip first and after 3 months operate on the other side.
ROENTEGENOGRAPHIC EVAL U ATION• AP view of pelvis with both hips with upper third femur with limbs in 15degrees internal rotation.• Spine, knee x-ray taken Note the following :• Acetabulum : Bone stock, floor, migration, protrusio, osteophytes and cup size.• Femur : Medullary cavity (size & shape). Limb length discrepancy Neck.
Templating• Draw horizontal lines: one joining both IT and other joining both lesser trochanters. Measure the limb length discrepancy as the difference in the length of lesser trochanter .
• Acetabulum :place acetabular template on the film and select a size that closely matches the contour of the pts acetabulam• Medial surface of the cup is at tear drop and inferior limit is at the level of obturator foramen
• Femur : select a size that most precisely matches the contour of proximal canal with 2- 3mm of cement mantle.select a neck length so that the diff in the height of femoral and acetabular centre is equal to LLD
• Mark the level of anticipated neck cut and measure its distance from lesser trochanter. template the femur similarly in lateral view
PREPARATION :• Take an informed consent.• Bath the entire extremity and hip with germicidal solution twice daily after patients is admitted to the hospital.• Shave the extremity, perineal area, hemipelvis to at least 10 cm proximal to the iliac crest and wash with soap as soon before surgery as possible and cover with sterile towels.• Prophylactic antibiotics.
PROPHYLACTIC ANTIBIOTICS• In the operating room 15 to 30 minutes before the skin incision• Profound blood loss, an additional operative dose after 4 hours appears justifiable• 1st generation cephalosporine- cefazolinIRRIGATING THE WOUND Irrigating the wound with a physiological solution during surgery – keeps the tissues moist, – removes debris and blood clots, – dilutes the number of bacteria that may be present.
OPERATION THEATRE :• Asepsis in the operating room is crucial• Body exhaust systems• Laminar flow rooms – vertical laminar flow rooms – horizontal flow systems (easier to install in an operating room with a low ceiling )• High efficiency particulate air (HEPA) filters in laminar flow rooms removing particles 0.3 μm or larger in diameter• Water-repellent gowns and drapes are recommended.• Double gloves also are recommended because much instrumentation is necessary in total hip arthroplasty, and glove puncture is common.• Limiting traffic through the operating room
SURGICAL APPROACHES AND TECHNIQUES• Each approach has relative advantages and drawbacks. Choice of specific approach for THR is largely a matter of personnel preference.• Posterolateral approach with patient in lateral position without greater trochanter osteotomy and dislocating the hip posteriorly is commonly done.
POSTOPERATIVE MANAGEMENT• Hip is positioned in approximately 15 degree abduction and neutral rotation, with the help of a triangular pillow splint.• Light skin traction may be applied for 24 hours. .• Gentle isometric exercise for few minutes each hour when they are awake from first operative day.• One the second postoperative day patient may sit on side of the bed avoiding excessive flexion at hip.• Drains removed 24-48 hours.
• Gait training begun on 2nd postoperative day, non weight bearing with a walker, if cemented-early weight bearing to tolerance is permitted• If cementless-touchdown weight bearing for 6-8 weeks.• Patient can be discharged when patient can walk on even surfaces, get out of bed, climb few steps.• Follow-up at 6 weeks. Roentgenograms are taken, full weight bearing advised
COMPLICATIONS : •Inherent to any major surgical procedure in elderly patients. •Specifically related to the procedure of THR: EARLY LATENerve injury -LooseningHemarthrosis/vascular injury -Component failureThromboembolism -OsteolysisBladder injuries -Heterotrophic ossification INDEPENDENT OF TIME Infection Dislocation Trochanteric non union Femoral fracture Limbs length discrepancy
1. Nerve injuries (0.7 –3.5%)• Sciatic, femoral and peroneal nerves may be injured by direct surgical trauma, traction, pressure from retractors, limb lengthening (> 4cm) or thermal or pressure injury from cement, post operative dislocation.• It is common in revision THR.• Prevention : By taking due care during surgical procedures and postoperative period.• Management : usually recovery occurs within 6 weeks, if not explore the nerve.
2 . Vascular injury : 0.2 % to 3 %• common during revision surgeries.• Femoral, obturator, iliac vessels are at risk. Prevented by• Careful placement of retractors.• Due care during transacetabular screw fixation. Management :• Cautery.• Temporary clamping of iliac vessels• Trans catheter embolisation preceded by arteriography• Alert the abdominal and vascular surgeons
3 . Bladder injuries and urinary tract complications :• Urinary tract infection is the most common complication (7-14 % ), managed with antibiotics.• Rarely bladder injury can occur by intra pelvic escape of cement.• Bladder injuries are jointly managed with urologist
4 . Thromboembolism• Most common serious complication following total hip arthroplasty• It is the most common cause of death occurring within 3 months of surgery and is responsible for more than 50 % of post operative mortality.• In western patients without prophylaxis, the incidence is 40-70 % and fatal pulmonary embolism is noted in 2 % patients.• Most common site is deep veins of calf of operated limb. Diagnosed by duplex doppler ultrasound and pulmonary scan.
Prevention by :• Early mobilization• Active exercises while in bed• External sequential pneumatic compression boots and elastic stockings. Pharmacologic prophylaxis :• Aspirin• Low does heparin, adjusted dose heparin• Dextran• Warfarin Early detection and confirmation and appropriate management with therauptic anticoagulants like thrombolytic enzymes, warfarin
INSTITUITION RELATED RISK FACTORS:• Reduce hospital stay(pre-op and post-op)• Prior pre op assessment as OP• Clean theatre setup• Closed door procedure• Laminar air flow• Body exhaust system• U V light
PROCEDURE PRECAUTIONS• Take / give bath in the morning• Skin preparation Shaving just before in the side room• Providone iodine cleaning before and after shave• Pre op antibiotics ( 1.5 gm Cefuroxime Sodium)30 – 45 MINUTES BEFORE SURGERY• Use incise drape ALWAYS• Use double gloves ALWAYS• Handle tissues with least trauma• Wound irrigation, Good hemostasis
Fit z geralds classification of infection in THR : Acute post operative - within 3 months Delayed –3 to 24 months Late (Haematogenous) – after 2 yearsStage 1• Acute post operative period• Classic fulminant wound infection• Infected deep hematoma• Superficial infection that subsequently extend to deep infectionStage 2• Deep delayed infection• Indolent and become manifest from 6-24 months after surgeryStage 3• Late infection occur 2 year or longer after surgery in a previously asymptamatic patient.
2-stage Reimplantation-1st stage-through debridement and reimplantationwith antibiotic coated cement2nd stagedefinitive reimplantation 3 months later
6 . Fractures :• Fractures of femur, acetabulum, or pubic ramus may occur during and after THR.• Femoral fractures are by far the most common. Management :• Conservative with traction• Additional plate and screws• Plate fixation• Revision arthroplasty with long stem• Custom made prosthesis.
7. Dislocation or subluxation :• Can occur in 3 % Causes :• Excess retroversion or ateversion• Small size head,• Laxity of the soft tissue around the joint.• Insufficient offset. Treatment :Reduction by : Bigelows or Stimsons method
8 . Heterotopic ossification :• Most commonly develops in male patients who have been operated for anklyosing spondylitis• Cause is unknown• Loss of motion is the predominant functional limitation Management :• Prophylaxis: Diphosphates• Low dose NSAIDs, indomethacin 75mg/day x 6 weeks• Radiotherapy
9. Loosening :• Femoral and acetabular loosening are the most serious femoral and acetabular long-term complications.• Most common indications for revision arthroplasty. Cemented femoral loosening :• Loosening of a femoral stem as defined as radiographically demonstrable change in the mechanical integrity of the load carrying cemented femoral component.• Loosening is present if a radiolucent zone more than 2 mm wide is seen. Especially if noted about the entire cement mass and if it is increased progressively in width.
Cementless femoral stem :• Fixation by bone ingrowth is defined as an implant with minimal or no opaque line formation around the stem.• An implant is considered to have a stable fibrous ingrowth when no progressive migration occurs but an extensive radio-opaque line forms around the stem. These lines surround the stem in parallel fashion and are separated from the stem by a radiolucent space upto 1 mm wide.• An unstable implant is defined as one with definitive evidence of either progressive migration within the canal and is atleast partially surrounded by divergent radio-opaque lines that are more widely separated from the stem at its extremities.
Acetabular loosening :• In general it is agreed that the acetabular cup is loose if a radiolucency of 2 mm or more in width is present in all three zones.• “The diagnosis of loosening is accepted in most instances if the radiolucent zone about one or both components is 2mm or more in width and the patient has symptoms on weight bearing and motion that are relieved by rest”.• Solution is the revision THR
Resurfacing Arthroplasty• Surface hip replacement consists of resurfacing the acetabulum with a thin layer of bearing surface, and replacement of only the femoral head (not neck) with a metal ball.• The ideal candidate for a resurfacing hip arthroplasty is a young (<60 years old), active individual, with normal proximal femoral anatomy and bone density who might be anticipated to outlive a conventional hip arthroplasty.
• Contraindications include - proximal femoral osteoporosis, -large cysts in the femoral head ( >1 cm), -large areas of osteonecrosis ( > 50 % head involvement), -severe acetabular dysplasia, -marked abnormality of proximal femoral geometry, -women of childbearing age, -known metal hypersensitivity, -and impaired renal function.
• The procedure is more technically demanding than conventional hip arthroplasty, particularly with reference to exposure of the acetabulum because the femoral head is not resected.• Although the procedure is conservative of bone, a more extensile soft-tissue dissection is required for adequate exposure. Resurfacing of the femoral head alone as a hemiarthroplasty may be valuable in young patients with osteonecrosis.
Minimally Invasive THR• There are two types of minimally invasive THA: the single-incision technique and the two-incision technique.• Almost all THA done in this manner are press- fit using porous-coated femoral and acetabular components because of difficulty cementing through a small incision.• The single-incision technique can be performed as a limited anterior approach as described by Hardinge,
• The two-incision technique employs an incision 1 cm greater than the femoral head diameter, based over the femoral neck anteriorly.• Through this, the hip is dislocated anteriorly and a femoral neck osteotomy performed. Acetabular preparation is performed with the aid of an image intensifier, which is also used to ensure correct positioning of a press-fit acetabular cup.• A separate 4 cm incision is made over the tip of the greater trochanter, and femoral canal preparation and stem insertion are again aided by an image intensifier.
HYBRID HIP REPLACEMENT• The combination of an uncemented socket and a cemented stem is commonly called hybrid hip replacement.• The goal of this combination of implants is to take advantage of the clinical reliability, durability, and ease of use of uncemented sockets and cemented femurs.• The method has produced excellent midterm results and is presently popular in North America
• REFERENCES :• Campbell’s Operative Orthopaedics – Vol.I• Orthopaedics principles and their Application – Turek• Replacement arthroplasty of hip by Harkess.J.W• Fracture in adults-Rockwood and Green.• www.hip replacement. org• Netter’s text book of anatomy.• Internet-JBJS,JOT