Arthroscopic repair is an effective treatment for dynamic medial ankle instability secondary to posttraumatic and partial injury of the deltoid ligament deep fascicle.

PURPOSE:When the intermediate or collicular fascicle of the medial collateral ligament (MCL) is injured, the diagnosis of posttraumatic medial ankle instability (MAI) is supported. The aim of this study was to describe an arthroscopic all-inside MCL repair after posttraumatic MAI secondary to an isolated injury of the MCL deep fascicle with a knotless suture anchor technique. METHODS:Seven patients (seven men, median age: 23 [19-28] years) with posttraumatic MAI were treated by arthroscopic means after failing nonoperative management. The median follow-up was 34 (13-75) months. The MCL was repaired with an arthroscopic all-inside technique. RESULTS:A tear affecting the deep and intermediate or collicular fascicle of the MCL was observed in all cases. In addition, five patients were diagnosed with an isolated fibular anterior talofibular ligament (ATFL) detachment, and in two patients, both the ATFL and calcaneofibular ligament were involved. All patients reported subjective improvement after the arthroscopic ligament repair. The median American Orthopedic Foot and Ankle Society score increased from 68 (range: 64-70) preoperatively to 100 (range: 90-100) at final follow-up. CONCLUSION:Posttraumatic MAI can be successfully treated by an arthroscopic all-inside repair of the MCL. The presence of an MCL tear affecting the tibiotalar ligament fibres attached to the area of the anterior colliculus should be considered a sign of posttraumatic MAI. This partial deltoid injury at the level of the intermediate or collicular fascicle will conduct to a dynamic MAI. LEVEL OF EVIDENCE:Level IV.