Peroneal tendon abnormalities in subjects with an enlarged peroneal tubercle

To examine the association between inframalleolar peroneal tendon abnormalities and an enlarged peroneal tubercle.

Two independent readers evaluated consecutive ankle MR imaging studies to classify inframalleolar peroneal tendon findings as normal, tenosynovitis, partial tear or complete tear. The size and morphology of the peroneal tubercle was also recorded. We performed statistical analyses for inter-observer agreement and to assess differences in peroneal tubercle size between groups with and without peroneal tendon abnormalities.

The study group comprised 121 subjects (mean age, 45.5 years) of whom 28% (34 out of 121) had lateral ankle symptoms. The peroneal tubercle was absent in 56% of subjects (68 out of 121). In subjects with a peroneal tubercle (>0 mm), the mean size was 3.5 mm (37% triangular and 7% plateau-shaped). Male subjects had significantly larger mean peroneal tubercle size than female subjects (2.1 ± 2.5 vs 1.2 ± 1.9 mm, P = 0.04). Overall, 26% (32 out of 121) of subjects had some peroneal tendon abnormality: 17% (20 out of 121) had tenosynovitis and 17 % (20 out of 121) had partial thickness tears. The peroneal tubercle size was significantly larger in subjects with peroneal tendon partial tears (P = 0.036), tenosynovitis (P < 0.001), and when both abnormalities were present (P = 0.007). ROC statistic showed 73% sensitivity and 74% specificity for detection of partial tears for peroneal tubercle size ≥4.3 mm.

Our study shows a significantly larger peroneal tubercle in subjects with inframalleolar peroneal tendon abnormalities. A cut-off of 4.3 mm showed good sensitivity and specificity for the presence of partial tears of the peroneal tendon.