The document discusses the evolution and development of biodegradable materials and implants in orthopedic surgery, highlighting their advantages over traditional metal implants, such as reduced trauma and improved biocompatibility. It covers the history, materials, properties, and applications of biodegradable polymers, as well as their mechanical properties, degradation processes, and clinical uses. The document also addresses potential disadvantages, including inflammatory responses and varying degradation rates, and emphasizes the ongoing research aimed at improving these devices for better patient outcomes.

1. Moderators
Dr .M.Nagendra Babu
( Professor)
Dr.K.RamKumar Reddy
(Asso.Professor)
Dr.T.Koner Rao
(Asst.Professor)
Dr.Jaisingh Rathod
(Asst.Professor)
Presented
by
Dr. B.Kiran
BIODEGRADABLE MATERIALS
& IMPLANTS

2. INTRODUCTION
Orthopaedic surgery has evolved in the last 2 centuries from
surgeons using amputation saws on mangled limbs, to
modified forms of external splintages and tractions, to
sophisticated internal fixation implants and devices that have
allowed early mobilization and pain free locomotion.
Most of the focus in modern orthopaedic implant
development is on developing devices that are stronger,
more acceptable to the body, cheaper and durable.

3. In the past few decades a lot of research has been done
and significant improvement has been seen in the
development of bioabsorbable osteosynthetic devices.
Biodegradable implants have allowed a paradigm shift
away from bionic (mechanical replacement) engineering
and toward true biologic solutions to reconstructive
problems

4. Further disadvantages to having metal plates, pins, mesh
or other metallic implants inside the body include:
• Accumulation of metals in tissues
• Hypersensitivity to titanium
• Growth restriction
• Pain
• Corrosion
• Implant migration
• Imaging and radiotherapy interference

5. Definition
 Biodegradable refers to a biologically assisted
degradation process.
 Within orthopaedics, terms such as
bioabsorbable and resorbable refer to the use of
biodegradable materials.

6. History
Low molecular weight Polyglycolic acid was synthesized by
Bischoff and Walden in 1893.
The first synthetic absorbable suture was developed from
Polyglycolic acid (PGA) by American Cyanamid Co. in 1962.
The 90:10 copolymer of glycolide and lactide -polygalactin - has
been applied as the competitive suture 'Vicryl' since 1975.
Since then sutures of polyglycolide and polylactide have been
used for many years and no carcinogenic, teratogenic, toxic, or
allergic side effects have been observed.
The only adverse reaction reported has been a mild non specific
inflammation.

7. Use of PGA as reinforcing pins, screws, and plates for bone surgery
was first suggested by Schmitt and Polistina in 1969.
Since then there has been a lot of development in manufacturing
biodegradable implants with properties appropriate for
osteosynthesis.

8. Materials
 All products are chemically based on lactic or glycolic acid
 Many are combinations of the two
 Polydioxanone (PDS)
 1991 – Too flexible
 Polyhydroxybutyrate (PHB)
 Polycaprolactone (PCL)
 Polyglycolic acid (PGA)
 1991 – Undesirable tissue reaction
 Polylactic acid (PLA) – 1994.
 Polylevolactic acid (PLLA)
 Poly-D-Lactic acid (PDLA)
 Currently, PGA, PDS, polylevolactic acid(PLLA), and racemic poly(D,
L)-lactic acid (PDLLA) are the primary alpha polyesters used for
bioabsorbable implants

9. What makes a good material?
 Mechanical properties match the application,
remaining sufficiently strong until the
surrounding tissue has healed
 No inflammatory, toxic, or carcinogenic
response
 Metabolized after fulfilling purpose, leaves
no trace
 Consistently reproducible
 Demonstrates acceptable shelf life
 Easily sterilized

10. PGA
 Semi-crystalline structure
 Stronger acid than PLA
 More hydrophilic and thus more susceptible to
hydrolysis than PLA
 Complete strength loss by 1 month
 Fully degrades in 3 months

11. Biocompatibility of PGA
 Although highly crystalline, becomes absorbed
very quickly
 Broken down into glycine and glycolic acid
 Glycine enters TCA cycle
 Glycolic acid can accumulate and lower local pH
 PGA is degraded by hydrolysis primarily to
pyruvic acid and is excreted as carbon dioxide
and water.

12. PLA
 Semi-crystalline structure
 Two stereo isomers – L and D lactide
 Presence of methyl groups makes it more
hydrophobic than PGA
 Complete mass loss in 5-6 years
 PLLA – most commonly used in orthopaedic
fixation
 Hydrophobic, thus resistant to hydrolysis

13. Biocompatibility of PLA
 Excellent biocompatibility and slow degradation
 No inflammatory cell infiltrates have been
reported
 Foreign body reaction limited to peri-implant
 Broken down into lactic acid and enters TCA
cycle.
 PDLLA is similarly
hydrolyzed via the TCA cycle to CO2 and water
and excreted by respiration.

14. The Reality
 Most absorbable fixation is a composite of PGA,
PLLA, PDLLA
 Attain the benefits of each material while
limiting the disadvantages
 Specific composition depends on manufacturer
as well as application

15. Structure, strength and properties
Polyglycolic acid (PGA) is a hard, tough, crystalline polymer with an average
molecular weight of 20,000 to 145,000 and a melting point of 224-230°C.
Polylactic acid (PLA) on the other hand is a polymer with initial molecular weights
of 180,000 to 530,000 and a melting point of about 174°C.
In orthopaedic implants poly-L-lactic acid (PLLA) has been used more extensively
because it retains its initial strength longer than poly-D-lactic acid (PDLA).
PGA belongs to the category of fast degrading polymers, and intraosseously
implanted PGA screws have been shown to completely disappear within 6
months.
PLLA on the other hand has a very long degradation time and has been shown to
persist in tissues for as long as 5 years post implantation.

16. For Orthopaedic usage, the main hindrance to development of
bioabsorbable implants is obtaining sufficient initial strength and
retaining this strength in the bone.
With the use of self reinforcing (SR) technique the material was
sintered together at high temperature and pressure, resulting in
initial strengths 5 to 10 times higher than those implants
manufactured with melt moulding technique.
Though initial strengths of SR-PLLA screws are lower than SR-PGA,
retention in the former is longer than the latter.
Now a- days, bio­
absorbable implants show no difference in the
stiffness, linear load & failure mode when compared with metallic
devices.

17. FACTORS AFFECTING THE BIOMECHANICAL PROPERTIES OF
BIOABSORBABLE POLYMERS:
Chemical Composition
Molecular weight
Viscosity
Molar ratio of copolymers
Sequence of chains
Crystallinity
Manufacturing Processes
Machining
Extrusion
Melt molding
Compression molding
Injection molding
Fiber reinforcement
Sterilization

18. Physical Dimensions
Diameter
Mechanical designs
Environmental
Temperature
pH
Blood flow
Rate of removal of degraded polymer
Oxidation/air exposure
Enzymatic action
Time
Viscoelasticity
Rate of degradation

19. Physical Properties
 Molecular weight
 Effects mechanical properties and degradation
 High M.wt = slower degradation
 Intrinsic viscosity
 Measure of resistance to flow
 High M.wt = high viscosity
 Crystallinity
 Crystaline, semi-crystaline, amorphous
 More crystalline = more strength
 More amorphous = faster absorption

20. • Porosity – low porous – enhances auto catalysis
• Glass transition temperature - the temperature at which
the
compound becomes as hard as glass.
 Temp below- polymer is stiff and hard
 Temp above -soft and rubbery
 Polymers used clinically have GTT above body temp.
Physical Properties

21. Mechanical Properties
 Ductility
 Amount of plastic strain the polymer will
withstand without fracturing
 Elastic modulus
 Stiffness of the polymer
 Depends primarily on the crystallinity

22. Degradation:
Crystalline polymers have a regular internal structure and because of
the orderly arrangement are slow to degrade.
Amorphous polymers have a random structure and are completely
and more easily degraded.
Semi-crystalline polymers have crystalline and amorphous (random
structure) regions.
Hydrolysis begins at the amorphous area leaving the more slowly
degrading crystalline debris.
Some earlier biodegradable implants have had problems with
degradation time and tissue reactions .

23. One commonly used material, Polyglycolide (PGA), is
hydrophilic and degrades very quickly, losing virtually all
strength within one month and all mass within 6-12 months.
Adverse reactions can occur if the rate of degradation exceeds
the limit of tissue tolerance
incidence of adverse tissue reactions to implants made of PGA -
2.0 to 46.7%.
So PGA in isolation is rarely used these days in the manufacture
of bioabsorbable implants

24. Poly L Lactic Acid (PLLA), has a much slower rate of absorption.
This homopolymer of L lactide is highly crystalline due to the
ordered pattern of the polymer chains and has been documented
to take >5 yrs to absorb.
The newer generation of implants remain predominantly
amorphous after manufacturing due to controlled production
processes of copolymers.
D Lactide when copolymerized with L Lactide increases the
amorphous nature of these implants. This increases the
bioabsorbability of these devices.
The ideal material is perhaps one that has a "medium"
degradation time of around 2 years.

25. Degradation
 Affected by many factors
 Implant size
 Material type
 Molecular weight
 Material phase (crystalline Vs amorphous)
 Presence of additives / impurities
 Implantation site (vascularity)
 Age and health status

26. Degradation
 Begins on contact with tissues
 Phase I
 Hydrolysis
 water penetrates the biodegradable device,
initially cutting the chemical bonds and converting
the long polymer chains into shorter and shorter
fragments

27. Degradation
 Phase II
 Metabolism
 The fragments are degraded into natural
monomeric acids found in the body, such as lactic
acid.
 “TCA cycle”-These acids enter the Kreb’s (citric
acid) cycle and are metabolised into CO2 and
water which are then exhaled and excreted in
phase three.

28. Biodegradable implants have many advantages over metal
implants, specifically for:
• Patients
 No additional surgery required for implant removal
 No permanent implant in the body
 Safe and biocompatible material, no risk of metal
allergic
reactions
 Reduced trauma
 No long-term implant palpability
No implant temperature sensitivity
Advantages:

29. • Clinicians
 Compatible with Magnetic Resonance Imaging (MRI) for
postoperative diagnosis
 Reduced radiographic scatter/obstruction
 Minimised risk of obstruction during any follow-up surgery
 Increased patient satisfaction
• Additional benefits
 Predictable degradation to provide progressive bone
loading, preventing stress shielding to aid better bone healing
 Reduced total cost - no removal operation
 Provided sterile reducing risk of cross infection
 No growth disturbances in children
 Allows micro-movement to aid fracture healing
Advantages:

30. Disadvantages:
Primarily the inadequate stiffness of the device and weakness
compared to metal implant can pose implantation difficulties like
screw breakage during insertion and also make early mobilization
precarious.
The other potential disadvantages are an inflammatory response
described with bioabsorbable implants, rapid loss of initial implant
strength and higher refracture rates.
Bostman et al reported an 11% incidence of foreign body reaction
to PGA screws in malleolar fractures.

31. INDICATIONS FOR ABSORBABLE FIXATION
DEVICES
Metatarsal osteotomies (hallux valgus)
Metacarpal and metatarsal fusions
Malleolar fractures
Osteochondritis dissecans
Fractures of the radius and olecranon
Epiphyseal fractures
Ruptures of the ulnar collateral ligament of the thumb
Arthroscopic fixation of meniscus lesions
Femoral canal occlusion for cement restriction
Drug delivery
Cell transplantation (e.g., Dermagraft)
Nerve reconstruction (e.g., Neurotube)
Adhesion prevention

32. Indications
 Pins or rods
 Osteotomies or fractures of mets that are
inherently stable
 Digital arthrodesis
 Transarticular fixation
 Medial column fusion
 Trauma
 Intraarticular calcaneal fractures
 Ankle fractures
 Physeal injuries in children

33. Indications
 Screws
 Displaced malleolar fractures
 Forefoot osteotomies providing both compression
and stability
 Midfoot and rearfoot fusions

34. Bionx
L1 Fully threaded smart screw. L2 Cannulated L3 SmartPin R1 Partial R2

35. Bionx
L. Pin insertion kit R. Smart screw insertion set

36. Contraindications
 Osteoporosis
 Comminution of fractures
 Sensitivity to absorbable materials
 Presence of infection

37. Adverse Reactions
 Seen most frequently with PGA implants
 Foreign body reaction
 Severe synovitis
 granuloma
 Formation of:
 Aseptic inflammation
 Sterile sinus tract
 Sterile abscess

38. Adverse Reactions
 Bone resorption
 Osteolytic lesions with cystic extensions of
implant tracks
 Osteoarthritis

39. Clinical Presentation of Foreign Body
Reaction
 Usually seen 50-113 days post implantation
 PGA – avg 11 weeks
 PLA – avg 4 years
 Painful, red, fluctuant swelling
 Suddenly appearing in otherwise normally healed
incision
 Suspected with persistent swelling, erythema and
increasing pain
 Sinus discharge of polymeric debris
 Extensive skin slough

40. Adverse Reaction
 Cultures are usually negative
 Wound drainage may persist 5 weeks – 4 months
 Acute reaction usually subsides after 4 months
and can be replaced by osteoarthritis that may
lead to fusions
 Radiographically see osteolysis along pin tract.
 Recommended that PGA implants not be used
near joint spaces due to FBR with intraarticular
dissemination of polymeric debris

41. Allofix Cortical Pins and Screws
 First used in 1994
 Allograft
 Devitalized, freeze dried cortical pins and screws
 Average time of graft incorporation is 4 months

42. Allofix
 Unique benefits
 Provides osteoconduction giving creeping
substitution
 Better biocompatibility
 Decreased sterile abscess formation, osteolysis,
bone resorption

43. Allofix
 Disadvantages
 Concern for transmitted pathogens such as HIV,
Hep B & C
 Possible host rejection
 Specific insertional instrumentation

44. Current uses:
Biodegradable implants are available for stabilization of
fractures, osteotomies, bone grafts and fusions
particularly in cancellous bones, as well as for
reattachment of ligaments, tendons, meniscal tears and
other soft tissue structures.
Knee: Arthroscopic surgery is used extensively for ACL
reconstruction in the form of interference screws and
transfixation screws.
Osteochondral fractures can be well fixed by using
arthroscopic techniques and biodegradable pins.

45. Shoulder:
Repair and reconstruction of many intra-articular and extra-articular
abnormalities in the shoulder, including rotator cuff tears, shoulder
instability, and biceps lesions that require labrum repair or biceps
tendon tenodesis.
Spine:
Bioresorbable implants have significant potential for use in spine
surgery.
Coe and Vaccaro published the first clinical series using
bioresorbable implants as interbody spacers in lumbar interbody
fusion.
The clinical and radiographic results of their study allowed them to
recommend the use of bioresorbable devices structural interbody
support in the TLIF procedure.

46. Paediatric Orthopaedics:
The applications have been widely varied, and the results very
successful.
Bostman et al showed that self reinforced absorbable rods were
suitable for fixation of physeal fractures in children.
In 1991, Hope et al had compared the self reinforced absorbable rods
with metallic fixation of elbow fractures in children.
Partio et al found SR-PLLA screws firm enough for fixation of
subtalar extra articular arthrodesis in children.
Bioabsorbable fixation technique for pediatric olecranon fractures
has been described, with the advantage of avoiding reoperation to
remove hardware

47. Hand:
mini-plating systems are available for fixation of fractures,
osteotomies and arthrodesis in the wrist and hand.
Miscellaneous:
There are bioabsorbable implants now available for use in humeral
condyle, distal radius and ulna, radial head and other metaphyseal
areas.
Bioabsorbable meshes are available for acetabular reconstructions.
Bioabsorbable implants are also variously used in
craniomaxillofacial surgery and dental surgery.

48. Future:
Bioabsorbable implant research is an evolving science.
Resorbable plates can be covalently linked with compounds such as IL-2, and
BMP-2 and represents a novel protein delivery technique.
BMP-2 covalently linked to resorbable plates has been used to facilitate bone
healing.
Covalent linking of compounds to plates represents a novel method for delivering
concentrated levels of growth factors to a specific site and potentially extending
their half-life.
An area for future development would have to focus on developing implants that
degrade at the "medium term".
Since the screw that persists in its track for 5 years or more does not offer the
advantage of bioresorbability, newer molecules may have to be studied.

49. Thank you…