Hybrid fixation improves structural properties of a free tendon anterior cruciate ligament reconstruction

This study sought to characterize the structural properties of a combined bioabsorbable interference screw and closed loop and button fixation technique (Hybrid) for femoral fixation of a free tendon graft versus a bioabsorbable interference screw or closed loop and button suspension fixation method alone.

Eighteen porcine femora and quadrupled cadaveric flexor tendons were treated in 3 experimental fixation study groups: (1) closed loop and button suspension (CLBS), (2) bioabsorbable interference screw (BIF), and (3) closed loop and button suspension with supplemental biodegradable interference screw (Hybrid). An Instron testing machine (Instron, Canton, MA) was used to quantify each group's structural properties with cyclic loading and tensile load-to-failure. A video digitizing system measured graft deformation during load-to-failure.

The Hybrid fixation group had significantly greater structural properties compared with the CLBS or BIF group. Ultimate loads (mean [SEM] in Newtons) were 1184 (88) N, 813 (83) N, and 561 (62) N for the Hybrid fixation group, CLBS group, and BIF group, respectively. Quasi-steady state cyclic stiffness (mean [SEM] in Newtons per millimeter) was also greatest for the Hybrid fixation group at 165 (11) N/mm, compared with CLBS (122 [8] N/mm), and BIF (95 [9] N/mm).

Femoral free tendon hybrid fixation provides superior structural properties under tensile and cyclic displacement conditions while preserving the working length of the native anterior cruciate ligament.

Hybrid femoral fixation may minimize postoperative laxity for free tendon anterior cruciate ligament reconstruction.