A Biomechanical Assessment of Biceps Femoris Repair Techniques

Background: Knee injuries encountered in clinical practice can involve avulsions of the biceps femoris from the fibula and proximal tibia. Advances in tendon repair methods now allow for repairs with increased surface areas using modern suture anchor techniques. Despite descriptions of repair techniques, there are no biomechanical studies on the biceps femoris for comparison. Purpose/Hypothesis: The objective of this controlled laboratory study was to determine the failure load of the native biceps femoris distal insertion and to evaluate modern repair techniques. Our hypothesis was 2-fold: (1) Suture repairs to the tibia and fibula would perform better on tensile testing than repairs to the fibula alone, and (2) complex bridge repairs, similar to those frequently used in rotator cuff surgery, would perform better on tensile testing than simple repairs. Study Design: Controlled laboratory study. Methods: A total of 40 paired, fresh-frozen cadaveric specimens were dissected, identifying the biceps femoris and its insertion on the proximal tibia and fibula. The native biceps femoris footprint was left intact in 8 specimens and tested to failure on a uniaxial materials testing machine evaluating tensile properties, while in the other 32 specimens, the biceps femoris insertion was dissected using a No. 15 scalpel blade, underwent repair, and was then tested to failure on a uniaxial materials testing machine evaluating tensile properties. Four repair constructs were evaluated, with 8 specimens allocated for each: construct 1 involved a simple repair (ie, passing suture through tissue in a running Krackow fashion and tying at the anchor site) to the fibula with 2 suture anchors, construct 2 involved a simple repair to the fibula and tibia with 3 suture anchors, construct 3 was a fibular repair with a tibial suture bridge involving the fibula and tibia and 3 suture anchors, construct 4 involved a transosseous repair through the fibula and 1 suture anchor on the tibia. Analysis of variance was used to evaluate for significance of the mean failure load and stiffness between groups. Results: The mean (±95% CI) failure loads were the following: native biceps femoris, 1280 ± 247.0 N; simple fibular repair, 173 ± 84.6 N; simple fibular and tibial repair, 176 ± 48.1 N; fibular repair with tibial suture bridge, 191 ± 78.5 N; and transosseous repair, 327 ± 66.3 N. The mean stiffness values were the following: native, 46 ± 13.0 N/mm; simple fibular repair, 16 ± 5.1 N/mm; s