Several flat tendon graft types are viable options for flat superficial medial collateral ligament reconstructions-A biomechanical analysis.

Purpose: Flat superficial medial collateral ligament (sMCL) reconstruction helps restore knee kinematics in medial instability, but recommendations on grafts that best mimic the sMCL's biomechanical properties are missing. This study aimed to compare the biomechanical properties of flat grafts to the native sMCL, hypothesizing that (1) flat grafts exhibit unique biomechanical properties and (2) graft configuration affects their biomechanical properties.

Study design: Controlled laboratory study.

Methods: The sMCL, semitendinosus, gracilis, quadriceps tendons and iliotibial band (ITB) were harvested from 20 fresh-frozen human cadaveric knees. Flat grafts were prepared, providing single- and double-strand grafts. The following groups (n = 10 each) were defined: (1) native sMCL, (2) single-strand semitendinosus tendon (SemiT single), (3) double-strand semitendinosus tendon (SemiT double), (4) single-strand gracilis tendon (Gracilis single), (5) double-strand gracilis tendon (Gracilis double), (6) single-strand ITB (ITB single), (7) double-strand ITB (ITB double) and (8) superficial layer of the quadriceps tendon (Quad). Using a universal uniaxial testing machine, the grafts were preconditioned (10 cycles, 10-50 N) and subsequently loaded to failure (LTF) (20 mm/min). Biomechanical properties of the grafts were compared using a one-way analysis of variance with post hoc correction (p < 0.05).

Results: Double-strand configuration of the hamstring tendons and the ITB resulted in a significant increase in stiffness, LTF and yield load (p < 0.05) and a significant decrease in tensile stress and ultimate strain (p < 0.05) compared to single-strand grafts. Single-strand SemiT and Quad, as well as double-strand Gracilis and ITB grafts, demonstrated comparable biomechanical properties to the native sMCL (n.s.). In contrast, double-strand SemiT tendon grafts exhibited significantly greater stiffness, LTF and yield load compared to the native sMCL (p < 0.01). Conversely, single-strand graft configuration of Gracilis and ITB resulted in significantly lower stiffness, LTF and yield load (p < 0.01) and higher tensile stress and ultimate strain (p < 0.001) compared to the native sMCL.

Conclusion: The graft type and configuration of the grafts significantly affects the biomechanical properties of flat sMCL grafts. Single-strand SemiT and Quad, and double-strand Gracilis and ITB grafts, mimic the biomechanical properties of the native sMCL, representing viable options for flat sMCL reconstructions. In contrast, double-strand SemiT grafts exceeded these properties, while single-strand Gracilis and ITB grafts demonstrate decreased biomechanical properties, possibly resulting in increased risk of medial overconstraint or residual laxity.

Level of evidence: There is no level of evidence as this study was an experimental laboratory study.