MCL augmentation using a peroneus longus split tendon autograft satisfactorily restores knee stability with no impairment in foot function and with a low failure rate for concurrent ACL reconstruction.

Purpose: Addressing grade 2 and 3 medial-sided instabilities during anterior cruciate ligament (ACL) reconstruction is crucial to reduce the risk of ACL graft failure. This study introduced a minimally invasive, medial collateral ligament (MCL) augmentation technique using a peroneus longus split tendon autograft, which was fixed to the femoral deep MCL insertion and tibial superficial MCL insertion.

Methods: This prospective, longitudinal, single-centre case series included patients who underwent MCL augmentation concurrent with primary or revision ACL reconstruction due to anteromedial instability. Preoperatively and at 1-year follow-up, clinical examinations, such as rolimeter test of anterior tibial translation and medial instability, knee (International Knee Documentation Committee subjective knee form [IKDC], Lsyholm, Knee Injury and Osteoarthritis Outcome Score [KOOS]) and foot function scores (American Orthopaedic Foot and Ankle Society score [AOFAS]) and complications, were analyzed.

Results: Thirty-one patients with a mean follow-up of 13.5 ± 2.6 months and a mean age of 27.8 ± 9.6 years were included. The side-to-side difference for anterior tibial translation significantly improved from preoperative to 1-year follow-up with an ACL reconstruction failure rate of 6.5%. No patient retained a grade 2 or 3 medial instability on valgus stress testing with 30° flexion. Significant improvements from preoperative to 1-year postoperative follow-up were observed in knee function scores: IKDC (48.9 ± 26.9- 71.3 ± 11.5, p < 0.001) and Lysholm (59.9 ± 28.5-80.5 ± 11.2, p = 0.002) as well as KOOS pain, ADL, sport and QoL, each reaching the respective minimal clinically important difference values. The foot function score AOFAS showed no significant impairment (100 ± 0-99.3 ± 2.5, p = 0.250). Complications included cyclops lesions of ACL reconstruction in three patients.

Conclusion: At 1-year follow-up, MCL augmentation using a peroneus longus split tendon autograft for patients simultaneously undergoing ACL reconstruction satisfactorily restores knee stability, has a low ACL reconstruction failure rate and does not significantly impair foot function.

Level of evidence: Level IV therapeutic study; case series.