Summary

This study revealed that the proximal end of the injured CFL was displaced medially in patients with residual ankle instability, and the talar end of ATFL hangs down in patients with recurrent ankle instability after CLAI surgery.

Abstract

Background

Arthroscopic anterior talofibular ligament (ATFL) repair for chronic lateral ankle instability (CLAI) has been reported to obtain good clinical outcomes. However, residual or recurrence of instability occurs in some patients. Risk factors for instability recurrence are not yet clear, and there are few reports of the lateral ankle ligament injury morphology. This study aimed to characterize the morphology of lateral ligament injuries in CLAI patients with residual or recurrence ankle instability after surgery using 3D model on MRI.

Methods

Twenty-seven ankles with CLAI (mean age: 28.2±15.0 years) and 10 ankles with osteochondral lesion of talus (OLT) without CLAI (mean age: 25.3 ± 13.1 years) who underwent arthroscopic surgery were included. Arthroscopic repair of the ATFL was performed, and if varus instability of ankle remained after ATFL repair, the calcaneofibular ligament (CFL) was repaired additionally. All OLT patients were confirmed no ATFL injury with arthroscopy. The patients divided into 3 groups; normal group including OLT patients, no CFL repaired group who repaired only ATFL (11 ankles), and CFL repaired group who repaired CFL additionally (16 ankles). Furthermore, CLAI patients with a talar tilt angle of 6 degrees or greater on varus stress radiographs at 1 year postoperatively were defined as the recurrence group (11 ankles), and those of less than 6 degrees as the non-recurrence group (15 ankles). Preoperative MRI images of the fibula, talus, calcaneus, ATFL, and CFL were reconstructed in 3D model using free 3D image display software: ITK-SNAP. Each vector in 3 dimensions of the distance between the tip of the fibula and the proximal end of the CFL (dx, dy, and dzCFL: lateral, anterior, and proximal direction were defined as positive) were measured and compared among normal, no CFL repaired, and CFL repaired groups. And, angle of the ATFL to the horizontal plane (ATFL angle: upward pointing of the talus end is positive) were measured and compared between the recurrence and non-recurrence groups.

Results

The mean dxCFLs were -3.17±1.14, -1.12±5.19, and -6.14±2.48 mm in normal, no CFL repaired, and CFL repaired and dxCFL of CFL repaired group was significantly lower than other two groups (P< .01). The mean ATFL angle was -1.2±8.0 degrees in the recurrence group and 8.3±8.4 degrees in the non-recurrence group, which was significantly larger in the recurrence group.

Conclusions

This study revealed that the proximal end of the injured CFL was displaced medially in patients with residual ankle instability, and the talar end of ATFL hangs down in patients with recurrent ankle instability after CLAI surgery. The residual or recurrence ankle instability should be eliminated, because they cause subchondral bone change in the medial gutter leading ankle osteoarthritis. In addition to arthroscopic ATFL repair, CFL repair or ATFL augmentation should be considered in case of CFL injury or talar side loose ATFL.