Biomechanical comparison of femoral fixation devices for anterior cruciate ligament reconstruction using a novel testing method

Abstract

Background: A novel biomechanical test method was implemented to compare the mechanical performance of two femoral fixation anchors (AperFix(r), Cayenne Medical, Scottsdale, AZ, USA or the AppianFx(r), KFx Medical, Carlsbad, CA, USA) that were utilized in anterior cruciate ligament reconstruction.

Methods: Anterior cruciate ligament reconstructions were performed in 20 porcine femurs by using bovine extensor tendon grafts secured with 9 mm femoral anchors (AperFix(r) or AppianFx(r)). 10 specimens were tested for each anchor type. Infrared position sensors determined the repair construct displacements during conditioning (20 cycles at 5-50 N at 0.25 Hz), cyclic loading (1500 cycles at 50-200 N at 1 Hz), and ultimate loading (150 mm/min). Outcomes included tendon elongation, anchor displacement, stiffness, maximum load, yield load, and load at 5mm of anchor displacement. It was hypothesized that there would be no differences in the outcomes of these two devices. Independent measure t-tests compared the performance of the devices (p<0.05).

Findings: The performance of the two anchors was comparable during the cyclic loading. During ultimate loading, a statistically higher yield load (p<0.01) and a load at 5mm of anchor displacement (p<0.01) were demonstrated for the AppianFx(r) as compared to AperFix(r). Maximum load and stiffness were not significantly different.

Interpretation: Given the good clinical track record of the AperFix(r), the comparable, and in some cases superior, the biomechanical data presented here for the AppianFx(r) are encouraging for their clinical implementation. This study also introduced a novel test method that directly tracks the relevant construct displacements during cyclic and ultimate loading tests of the anterior cruciate ligament reconstructions.