The effect of an ossicle of the lateral malleolus on ligament reconstruction of chronic lateral ankle instability.

BACKGROUND

Ossicles at the tip of the lateral malleolus are frequently found in patients with chronic lateral ankle instability (CLAI). However, the relationship between the presence or the size of an ossicle and the outcome of ligament reconstruction is poorly understood. Therefore, this study aimed to evaluate the effect of an ossicle at the tip of the lateral malleolus on ligament reconstruction in CLAI.

MATERIALS AND METHODS

Seventy-four ankles with chronic lateral instability that received lateral ligament reconstruction using a modified Broström technique between January 2001 and March 2007 were included. The mean followup was 47 (range, 25 to 89) months. Ankles were divided into 2 groups: the ossicle group (26 ankles, 35.1%) and the non-ossicle group (48 ankles, 64.9%). Then, depending on the size, the ossicle group was subdivided into small (less than 10 mm, 14 ankles) and large ossicles (greater than 10 mm, 12 ankles). Pre- and postoperative Karlsson-Peterson ankle scores and findings on stress radiographs were compared between the groups.

RESULTS

Both the ossicle and non-ossicle groups improved significantly on stress radiographs without difference between the groups. Karlsson-Peterson ankle scores showed functional improvement in each group, however, the mean score at last followup was significantly lower in the ossicle group (p=0.01). The prevalence of an osteochondral lesion of the talus was significantly higher in the ossicle group (p=0.046). In ankles with large ossicles, varus stability was achieved but anterior displacement of the talus was not improved after ligament reconstruction.

CONCLUSION

The surgeon should be aware of the inferior functional outcome in ankles with ossicles. Also, when the ossicle is large, excision and modified Broström technique may not be suitable to achieve mechanical anteroposterior stability. Therefore, fusing the ossicle to the fibular tip or using other methods of ligament reconstruction can be considered when performing ligament reconstruction in CLAI with associated large ossicles.