Biomechanical evaluation of superficial transfer of the biceps femoris tendon

Abstract

The biomechanics of the biceps femoris tendon transfer were determined from four fresh, frozen extremities. All transfers involved the proximal and anterior advance ment of a selected portion of the tendon to a position superficial to the lateral collateral ligament. The rota tional torque and flexion force were measured before and after the transfer with the knee positioned at 10°, 20°, 30°, and 45° of flexion, in neutral and 5° internal rotation. Although more specimens need to be tested for statistical confirmation, the transfer of the superficial portion of the biceps tendon resulted in average de creases of 2% and 15% in the rotational and flexion capacity of the biceps, respectively. Biomechanically, the functional lever arm of the transferred tendon about the longitudinal (internal-external rotation) axis was es sentially unchanged, while the functional lever arm about the sagittal (flexion-extension) axis was de creased slightly. The total transfer of the biceps tendon resulted in an increase of 28% in the rotational capacity, while the flexion capability was decreased an average of 75%. In addition, the total transfer resulted in the biceps becoming an extensor at 10° and 20° of flexion, which could actually worsen the instability. Thus, fol lowing the total transfer, the functional level arm about the sagittal axis was decreased, while the functional lever arm about the longitudinal axis was increased. In summary, neither the partial nor the total transfer of the biceps femoris tendon superficial and anterior to the fibular collateral ligament appeared to be a biome chanically effective ancillary for the treatment of anter olateral rotatory instability.