Endoscopic flexor hallucis tenolysis combined with ACL reconstruction allows better function and return to high sporting activities

Background: Non-contact anterior cruciate ligament (ACL) injuries frequently involve a medial collapse mechanism characterized by knee valgus and internal tibial rotation. Functional hallux limitus (FHLim), defined as the inability of the hallux to extend dorsally during the propulsive phase of gait due to a tenodesis effect at the retrotalar pulley, is identified as a contributing kinematic factor. This condition induces abrupt foot pronation and synchronized internal rotation of the tibia, potentially increasing strain on the ACL.

Objective: This study aims to evaluate the clinical and biomechanical efficacy of combining endoscopic flexor hallucis longus (FHL) tenolysis with ACL reconstruction to address distal kinematic drivers of knee instability.

Key Points: A cohort of 102 patients underwent combined ACL reconstruction and FHL tenolysis between 2002 and 2019. Evaluation utilized a retrospective functional questionnaire (n=70) and prospective footprint and gait analysis (n=68 short-term; n=23 long-term). The mean Tegner-Lysholm score was 87.16, with over 80% of patients returning to strenuous activity levels. Footprint analysis demonstrated significant gait normalization in 80% of patients at six months postoperatively. These biomechanical improvements remained stable at a median follow-up of 87.6 months, with 87% of the long-term group showing significant changes in plantar pressure distribution. The ACL revision rate was 1%, and no complications were associated with the FHL tenolysis.

Conclusion: FHLim is a prevalent biomechanical factor in non-contact ACL injuries. Integrating FHL tenolysis with ACL reconstruction addresses the lower kinetic chain dysfunction, resulting in normalized gait patterns, high patient satisfaction, and sustainable long-term functional stability.