In vivo degradation characteristics of bioabsorbable cross-pins in anterior cruciate ligament reconstruction

Abstract

BackgroundWe evaluated degradation of bioabsorbable femoral cross-pins following anterior cruciate ligament (ACL) reconstruction. MethodsFour patients underwent ACL reconstruction using hamstring autograft with femoral fixation provided by a polylactic acid/polyglycolic acid copolymer (LactoSorb L15) cross-pin. Serial computed tomography (CT) scans were performed of the reconstructed knees at approximately 6weeks, 4months, 1year and 2years, postoperatively. A radiologist evaluated the scans for density of pins and surrounding bone and pin morphology. ResultsThe cross-pins demonstrated a relative reduction in density of 7.7%, 49.1%, and 75.0% at 4months, 1year and 2years, respectively. Bone density values adjacent to the pin decreased by an mean of 8.6% between 6weeks and 4months. At one year an additional 14.2% reduction in bone density was seen but at 2years the relative reduction in bone density had decreased to 7.4%. Evaluation of pin morphology revealed that minimal change had occurred after 6weeks. At 4months all of the pins were showing some morphologic changes on the surface, but none had fractured. After 1year, two of the pins had fractured. By 2years all of the pins had fractured. None of the pins had completely reabsorbed at 2years postoperatively. ConclusionsLactoSorb L15 cross-pins for femoral fixation in ACL reconstruction remain largely unchanged 4months postoperatively, suggesting that this device maintains the necessary structural integrity to allow early integration of soft tissue grafts within bone tunnels. Level of evidenceIV, case series.