Biomechanical Evaluation of Bioabsorbable versus Metallic Screws for Posterior Cruciate Ligament Inlay Graft Fixation

Abstract

Background Although a tibial inlay technique for posterior cruciate ligament reconstruction is advantageous, metallic screw fixation of the bone block is required. This may pose problems for future surgery (eg, osteotomies, total knee replacement). Hypothesis There is no significant difference in the biomechanical integrity of bone block fixation using stainless steel versus bioabsorbable screw fixation of the tibial inlay graft in posterior cruciate ligament reconstruction. Study Design Controlled laboratory study. Methods Fourteen human cadaveric knees were randomized to receive either stainless steel or bioabsorbable screw fixation of a bone—patellar tendon—bone graft. Cyclic tensile testing of each construct was performed, followed by a load-to-failure test. Digital video digitization was used to optically determine tendon graft deformation. Results Cyclic creep deformation showed no significant difference between the 2 groups ( P = .8). The failure load (stainless steel, 461 ± 231 N; bioabsorbable, 638 ± 492 N; P = .7) and linear stiffness (stainless steel, 116 ± 22 N/mm, bioabsorbable, 106 ± 44 N/mm; P = .6) also showed no significant difference between the 2 groups. Optically measured graft deformation was not significant for distal ( P = .7) and midsubstance ( P = .8) regions, while proximal deformation was significantly higher for bioabsorbable fixation ( P = .02). All samples failed at the tibial insertion site with the tibial bone block fracturing at the screws. Conclusion Bioabsorbable screw fixation using a tibial inlay technique does not compromise the strength and stiffness characteristics afforded by metallic fixation. From a biomechanical perspective, bioabsorbable screws are a viable alternative to metal in the context of tibial inlay reconstruction. Clinical Relevance Use of bioabsorbable fixation can potentially eliminate future hardware problems after posterior cruciate ligament reconstruction using a tibial inlay technique.