Anchor Repair of Biceps Femoris Repair Is Similar to Knotless Tunnel Repair in Laboratory Conditions

Avulsions of the biceps femoris and fibular collateral ligament (FCL) from the fibula often present as a knee ligament injury for treatment. Recent advances in suture anchors allow for knotless tension and retension of repair constructs in contrast to using transosseous sutures alone. The tensionable suture anchors may eliminate creep and improve the biomechanical performance of repairs at time point zero.

The aim of this study is to compare the biomechanics of 2 repair constructs for biceps femoris repair. It was hypothesized that both repair constructs would effectively restore knee stability in a distal biceps femoris/FCL injury pattern, and that the modern knotless suture anchor would produce a biceps femoris repair that would fail at a higher load and exhibit greater stiffness during tensile testing.

Controlled laboratory study.

Sixteen match-paired, fresh-frozen cadaveric knees (74 ± 7.5 years) were tested by external rotation (at 5 N·m) and varus (at 10 N·m) on a 6 degrees of freedom robotic system in 3 conditions: uninjured state, avulsed FCL and biceps femoris, and 1 of the 2 repair options, repair with knotless suture anchors or transosseous sutures alone. After robotic testing, repairs underwent tensile testing to failure on a uniaxial tensile testing machine to determine the failure load and stiffness of each repair construct. The mean degrees for external and varus rotation, failure load, and stiffness values were calculated for each group and compared using paired t tests between the 3 conditions and 2-sample independent t tests between the 2 repair groups.

Robotic testing of both repairs showed significant reductions (P < .05) compared with the sectioned state in varus rotations at 0° and 30° and external rotations at 0° of knee flexion. The repair with suture anchors significantly reduced laxity in varus rotation at 60° of knee flexion (P = .02), whereas the suture alone repair did not (P = .09). Tensile testing revealed mean failure loads for the knotted suture repair of 317 N (range, 193-450 N) and for the knotted anchor repair of 447 N (range, 239-818 N), showing no statistically significant difference (P = .12). The mean stiffness for the knotted suture repair was 9.45 N/mm (range, 4.6-12.8 N/mm). The anchor repair was 9.16 N/mm (range, 3.6-15.3 N/mm), showing no statistically significant difference (P = .87). The sectioned state was significantly different from the intact state at all flexion angles for all conditions tested (P < .05).

Our study demonstrated that a transosseous biceps femoris repair with knotless suture anchors performed similarly to a transosseous biceps femoris repair with suture alone in robotic varus and external rotation testing. With tensile testing, a higher failure load was observed in each matched pair with suture anchor repair. However, no statistically significant differences were found between the restoration of knee kinematics, mean failure loads, and stiffness in these 2 repair constructs.

Understanding the biomechanical and tensile performance of the biceps femoris aids clinicians with pre- and intraoperative decisions.