Purpose: Semitendinosus and gracilis muscles whose tendons are used in surgical reconstruction of the anterior cruciate ligament maintain their contractile ability, but the peak torque angle of hamstring muscles shifted to a shallow angle postoperatively. The goal was to quantify the influence of the myofascial structures on instantaneous moment arms of knee muscles to attempt explaining the above-mentioned post-surgical observations.
Methods: Hamstring harvesting procedures were performed by a senior orthopaedic surgeon on seven lower limbs from fresh-frozen specimens. Femoro-tibial kinematics and tendons excursion were simultaneously recorded at each step of the surgery.
Results: No significant difference was demonstrated for instantaneous moment arm of gracilis during anterior cruciate ligament surgery (84% of the maximum intact values; P ≥ 0.05). The first significant semitendinosus moment arm decrease was observed after tendon harvesting (61% of the maximum intact values; p ≤ 0.005). After hamstring harvesting, the maximum and minimum moment arm (both gracilis and semi tendinosus) shifted to a shallow angle and 90°, respectively.
Conclusion: Moment arm modifications by paratenons and the loose connective tissue release are essential to understand the peak torque obtained to a shallow angle.
Level of evidence: Basic science study, biomechanics.
Keywords: Areolar connective tissue; Epimuscular force transmission; Fascia; Hamstring harvesting; Myofascial force transmission; Paratenon.
© 2021. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.