Proximal, Distal, and Combined Fixation Within the Tibial Tunnel in Transtibial Posterior Cruciate Ligament Reconstruction: A Time-Zero Biomechanical Study In Vitro.

Abstract

To compare the time-zero biomechanical properties of 3 graft fixation techniques (proximal, distal, and combined fixation) within the tibial tunnel in transtibial posterior cruciate ligament (PCL) reconstruction. Porcine tibias and bovine extensor tendons were used to simulate a transtibial PCL reconstruction in vitro. Load-to-failure testing was carried out in 3 groups: distal fixation alone (group I, n = 10), proximal fixation alone (group II, n = 10), and combined fixation (group III, n = 10). The load-elongation curve, tensile stiffness (in newtons per millimeter), ultimate load (in newtons), yield load (in newtons), energy absorbed to failure (in joules), and failure mode were recorded. All graft-tibia complexes failed because the grafts slipped past the interference screws. The tensile stiffness, yield load, and energy absorption in group I were significantly lower than those in group II and group III (tensile stiffness, 19.25 ± 9.68 N/mm in group I vs 34.92 ± 16.48 N/mm in group II [P = .016] and 32.31 ± 13.79 N/mm in group III [P = .041]; yield load, 265.36 ± 144.52 N in group I vs 398.23 ± 57.04 N in group II [P = .006] and 424.94 ± 74.00 N in group III [P = .001]; and energy absorption, 5.16 ± 2.35 J in group I vs 19.95 ± 3.48 J in group II [P < .001] and 21.09 ± 4.29 J in group III [P < .001]). No statistically significant differences in biomechanical properties were found between group II and group III (P > .05). Compared with distal fixation in transtibial PCL reconstruction, proximal fixation and combined fixation showed superior time-zero biomechanical properties. Proximal fixation and combined fixation produced superior biomechanical properties to distal fixation in transtibial PCL reconstruction.