2. DEFINITION
• implants that are degraded in a biological enviornment
and their breakdown products are incorporated into
normal cellular physiological and biochemical processes.
3. HISTORY
• Low molecular weight Polyglycolic acid was synthesized by
Bischoff and Walden in 1893
• Use of PGA (POLY GLYCOLIC ACID) as reinforcing pins,
screws, and plates for bone surgery was first suggested by
Schmitt and Polistinain 1969.
4. Shortcomings of metallic implants
• Inherent problems existing with the use of these metallic
devices like ‘Stress shielding phenomenon’, pain, local
irritation.
• Retained metallic implants are always at the risk of
endogenous infection.
• Release of metallic ions from these implants has been
documented.
• Because of these reasons there is need for a second surgery
for implant removal after the bone has healed.
5. Biodegradable materials
1. Polylactic Acid
• slower resorption
• Poly-L-lactic acid (PLLA) has been used more extensively
because it retains its initial strength longer than Poly-D-lactic
acid (PDLA).
2. Polyglycolic Acid
• quick resorption( as fast as 5 months)
• loses strength quickly
7. Advantages of these implants
• Limits stress shielding of the bone , so limits osteopenia.
• Eliminates the need of hardware removal so it also makes
the revision surgery less complicated.
• Radioluscent properties facilitate intra or post operative
evaluation by radiography and even MRI .
• Useful in pediatric fracture fixation with physeal injuries.
8. INDICATIONS
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
9. KNEE
• ACL reconstruction in the form of interference screws and
transfixation screws.
• Osteochondral fractures can be well fixed by using arthroscopic
techniques and biodegradable pins.
• Osteochondritis dissecans
• Meniscal tacks and biodegradable suture anchors have opened
new avenues for soft tissue reconstruction in complex knee
injuries.
10. SHOULDER
• Used in 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.
• In a study of arthroscopic Bankart reconstruction (sumuni et all)
using either PGA polymer or PLA polymer implants the overall
clinical results were comparable at two year follow up.
• Eliminates the need of passing sutures through bone tunnels.
11. SPINE
• Coe and Vaccaro published the first clinical series using
bioresorbable implants as interbody spacers in lumbar interbody
fusion.
• Bioabsorbable anterior cervical plates have been used and
studied as alternatives to metal plates when a graft containment
device is required. Ames at al found that bioabsorbable plates
provided better stability than resorbable mesh.
12. FOOT AND ANKLE
• The first series of fixation of ankle fractures with absorbable
implants was reported by Rokkanen et al in 1985.
• Currently, used in medial malleolar fractures , ankle fractures
and osteochondral fractures of talus.
• Also used in osteotomies of hallux valgus, syndesmotic
disruptions and Lisfranc’s dislocations.
13. 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.
• Femoral canal occlusion for cement restriction.
• Drug delivery
• rupture of ulnar collateral ligament.
• Bioabsorbable implants are also variously used in
14.
15.
16. Degradation and Elimination
• The degradation of these polymers occurs
1.Mainly by hydrolysis
2.And to lesser extent through non specific enzymatic action.
17. Factors affecting the biomechanical
properties
1. Chemical composition
2. Manufacturing Processes
3. Physical dimentions mostly the thickness
4. Enviornmental factors like temperature,Ph,blood
flow,oxidation or air exposure and local enzymatic action.
5. Time
18. COMPLICATIONS
• Infections
• Osteolysis mailnly by Polyglycolic acid.
• Synovitis
• Hypertrophic fibrous encapsulation
• Premature loosening and breakage.
• Similar to metallic suture anchors, superficial insertion
leading to cartilage wear on the opposing articular surface
and deep insertions causing suture fraying and failure.
19. • If they fail and become intraarticular they may be difficult
to find on routine X-rays.
20. DRAWBACKS
1. 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 difficult.
2. Cast support and use of cruthces for lower extremity fractures
has been recommended, which limits their further use.
3. Bioabsorbable Implants have excessively low elastic moduli
resulting in backing out of screws.
4. The price is much higher than its steel counterpart.
