Delay of 2 or 6 Weeks Adversely Affects the Functional Outcome of Augmented Primary Repair of the Porcine Anterior Cruciate Ligament

Abstract

Background Enhanced primary anterior cruciate ligament repair, in which suture repair is performed in conjunction with a collagen-platelet composite to stimulate healing, is a potential new treatment option for anterior cruciate ligament injuries. Previous studies have evaluated this approach at the time of anterior cruciate ligament disruption. Hypothesis Delaying surgery by 2 or 6 weeks would have a significant effect on the functional outcome of the repair. Study Design Controlled laboratory study. Methods Sixteen female Yorkshire pigs underwent staged, bilateral surgical anterior cruciate ligament transections. Anterior cruciate ligament transection was initially performed on 1 knee and the knee closed. Two or 6 weeks later, enhanced primary repair was performed in that knee while the contralateral knee had an anterior cruciate ligament transection and immediate repair. Biomechanical parameters were measured after 15 weeks in vivo to determine the effect of delay time relative to immediate repair on the healing response. Results Yield load of the repairs at 15 weeks was decreased by 40% and 60% in the groups where repair was delayed for 2 and 6 weeks, respectively ( P = .01). Maximum load showed similar results (55% and 60% decrease in the 2- and 6-week delay groups, respectively; P = .011). Linear stiffness also was adversely affected by delay (50% decrease compared with immediate repair after either a 2- or 6-week delay, P = .011). Anterior-posterior laxity after 15 weeks of healing was 40% higher in knees repaired after a 2-week delay and 10% higher in those repaired after a 6-week delay ( P = .012) when tested at 30° of flexion, but was not significantly affected by delay when tested at 60° or 90° ( P = .21). Conclusion A delay between anterior cruciate ligament injury and enhanced primary repair has a significant negative effect on the functional performance of the repair. Clinical Relevance As future investigations assess new techniques of anterior cruciate ligament repair, the timing of the repair should be considered in the design and the interpretation of experimental studies.