Medial collateral ligament section during unicompartmental knee arthroplasty managed by direct repair and fascia lata augmentation autograft: a case report and surgical technique.

Background: The medial collateral ligament (MCL) is crucial for ensuring implant stability after unicompartmental knee arthroplasty (UKA). Intraoperative MCL lesions can cause valgus instability, affecting function and implant longevity, and thereby negatively impacting the patient's outcome. Every surgeon who performs UKA may encounter this complication in their daily practice. In this context, this case report presents a rescue technique. The existing literature does not specify a protocol for managing this complication. This article presents the first instance of accidental midsubstance section of the MCL during medial UKA, managed through primary suture and augmentation repair with a fascia lata (FL) autograft. The procedure was subsequently replicated step by step on an anatomical specimen.

Case description: A 54-year-old woman, previously successfully treated with right medial UKA, was referred to our clinic following an unsuccessful attempt at conservative treatment for osteoarthritis in the left knee. Scheduled for a left medial UKA, an inadvertent midsubstance transection of the deep part of the MCL was encountered during the procedure, resulting in valgus instability. The MCL was promptly repaired and reinforced using an ipsilateral FL augmentation autograft. Subsequent UKA surgery was successfully completed. Follow-up at one year revealed favorable post-operative outcomes, with symmetrical stability on stress radiographs and no indications of early loosening.

Conclusions: To our knowledge, this article represents the first documentation of the direct management for this rare yet severe complication. This case report could therefore inspire any surgeon facing this complication. The technique, grounded in biomechanical principles, ensures direct medial stability whilst allowing uninterrupted continuation of the initial procedure. Characterized by simplicity and reproducibility, the approach demonstrates favorable short-term outcomes. Because the results should be interpreted considering the limited impact of a case report, further prospective studies are essential to substantiate and strengthen these findings.