The Journal of Bone and Joint Surgery

Image Quiz

Pain in the Lateral Malleolus Fifty-two Months Following Open Reduction and Internal Fixation of an Ankle Fracture¹ (continued)

Discussion

Local inflammatory and osteolytic foreign-body reactions to bioabsorbable implants made of polyglycolic acid have been well documented in the literature^2-5. Rapid degradation of the polyglycolic acid polymer causes these adverse reactions to occur within two to four months after implantation, when the disintegration of the polymer has reached its final phase^6,7.

Polylactic acid is another synthetic biodegradable polymer used in fracture-fixation implants. In contrast to polyglycolic acid, the degradation time of the stereo-isomeric form of polylactic acid that is used most commonly, poly-L-lactic acid, is several years. Consequently, the possible foreign-body reactions to devices made of poly-L-lactic acid can be expected to emerge much later than the reactions to devices made of polyglycolic acid. Because implants made of poly-L-lactic acid have been used clinically on a widespread basis for less than ten years, knowledge of the long-term biocompatibility of this polymer in human tissues is limited. In this case, a local inflammatory reaction to a poly-L-lactic acid screw occurred more than four years after its use in the fixation of an ankle fracture.

It has been suggested that poly-L-lactic acid has adverse immunological complement-activating potential⁸, but the data on this issue are controversial⁹. The fact that the late foreign-body reaction in the present report occurred only on the lateral side of the ankle suggests that the response represented a local overload of polymeric debris rather than an immunologically mediated sensitivity to the polymer.

The clinical use of poly-L-lactic acid implants has increased, not only in fracture fixation but also in new applications such as operative treatment of instability of the shoulder¹⁰, arrow repair of meniscal lesions¹¹, and reconstruction of the anterior cruciate ligament with use of interference screws¹². Orthopaedic surgeons should be aware of the possibility of late foreign-body reactions to bioabsorbable implants that have a long degradation time.

References:

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