CT scan assessment of the dimensions and morphological variations of the peroneal tubercle.

Purpose: The hypertrophied peroneal tubercle may result in lateral ankle pain with peroneal tendon tenosynovitis and rupture. The aim of this study was to evaluate different configurations and dimensions of the normal peroneal tubercle using two-dimensional CT scan.

Methods: Totally, 100 normal CT scans of cases older than 18 years of age were assessed to determine the shape of the peroneal tubercle. Moreover, height, length and width of different configurations of the normal peroneal tubercle were measured in axial and coronal sections of the ankle CT scans.

Results: Four different configurations based on the axial cut of the calcaneus were found; single-convex (59%), double-convex (24%), plateau (9%), and convex-concave (8%) without statistically significant difference between genders (p-value: 0.526). Totally, mean of height, length and width were 4.42 ± 1.38 mm, 28.88 ± 6.58 mm and 17.17 ± 3.85 mm, respectively. Although mean of the height in the single-convex and the double-convex types were 4.5 ± 1.4 mm and 5.0 ± 1.4 mm, respectively, the highest peroneal tubercle in the single-convex and the double-convex group were 10.2 mm and 8.5 mm, respectively.

Conclusions: In cases with lateral ankle pain and suspicious to hypertrophied peroneal tubercle, two-dimensional CT scan can be an available practical modality to identify the pathological type of the peroneal tubercle based on the presented classification and normal values. As previously reported in the literature, considering cut-off point of 5 mm could result in overdiagnosis of the hypertrophied peroneal tubercle, especially in single-convex type; however, clinical correlation is always paramount.

Level Of Evidence: Level IV.