The Role of Cavovarus Deformity in the Pathogenesis of Peroneal Tendon Tears

CATEGORY: Other; Sports INTRODUCTION/PURPOSE: While it is a commonly accepted principle peroneal tendon (PT) tears are associated with cavovarus deformity, this is the first study that both quantifies deformity in patients with surgically proven tears using sophisticated and reproducible methods to compare radiographic measurements to a matched control group. Understanding of the anatomy and mechanism of injury affecting the PTs has led to greater recognition of PT tears as an important cause of lateral sided foot and ankle pain. The literature reports a presumed correlation between the cavus foot and PT tears. Little data exist quantifying the correlation between PT tears and the alignment of the foot. We hypothesize the cavovarus foot applies stress over the lateral border of the foot leading to degenerative changes in PTs. METHODS: A cohort of 252 consecutive patients operatively treated for peroneal tendon tears (PT) were compared to an age- and sex- matched control (C) group of 104 outpatients treated for isolated forefoot problems. Calcaneal pitch, calcaneal - first metatarsal, talometatarsal, and talocalcaneal angles were compared on standing lateral radiographs. Talometatarsal and talocalcaneal angles, and talonavicular coverage, were compared on standing anteroposterior radiographs. Published radiographic criteria were used to determine cavovarus. ANOVA analysis detected statistically significant differences between patients and controls and a subsequent Tukey-Kramer test compared the control group with each type of PT tear. An a prioripower analysis was performed to calculate the minimum sample size in each cohort to detect a 90% effect size for a significance level of p<0.05. RESULTS: Radiographic cavovarus was found in 9.4% (74/252) of PT group, and 6.7% (7/104) in controls. On lateral radiographs a significant greater calcaneal pitch (p=0.0001), and significant smaller calcaneal-first metatarsal angle (p=0.0084) was noted with PT tears (p=0.0001). On anteroposterior radiographs a significant smaller talometatarsal angle (p=0.0001) and talonavicular coverage (p=0.0001) were noted in PT tears. AP talocalcaneal and lateral talometatarsal and talocalcaneal angles were not correlated with PT tears. Patients treated for PT tears, isolated peroneus brevis tears (PB) accounted for 67.9% (171/252), isolated peroneus longus (PL) tendon tears were 7.5% (19/252), PB and PL tears accounted for 17.5% (44/252). A smaller talometatarsal angle on the AP was associated with PL (0.0098) and combined PB and PL tears (<0.0001) but not PB tears alone (0.1162). CONCLUSION: The correlation between cavovarus and peroneal pathology in the literature is highly anecdotal. Few studies report objective measures. This is the first study to our knowledge comparing nature and severity of cavovarus according to location of peroneal tear. This study proves and quantifies objective measures of cavovarus that correlate with peroneal tendon tears, when compared to a cohort of matched controls.