The Influence of Metatarsus Adductus Angle on Fifth Metatarsal Jones Fractures

CATEGORY: Trauma; Midfoot/Forefoot INTRODUCTION/PURPOSE: Previous studies have reported increasing metatarsus adductus angle (MAA) to be associated with delayed union and refracture following intramedullary screw fixation of fifth metatarsal Jones fractures. The purpose of this study was to determine the influence of MAA on postoperative course following intramedullary screw fixation of Jones fractures. We also sought to identify associations between elevated MAA and both fracture and patient characteristics. METHODS: We performed a retrospective review of all Jones fractures treated with primary intramedullary screw fixation by 4 foot and ankle fellowship-trained orthopaedic surgeons at a single institution from 1995 through 2015. Exclusion criteria included concomitant foot/ankle procedures and revision surgery. Charts were reviewed for patient and injury characteristics, implant, and postoperative course. Radiographs were examined for fracture classification, radiographic union, and MAA. MAA calculations were performed on standard weight-bearing digital radiographs using the traditional method, with the 5th metarso-cuboid joint as a reference. Based on severity of MAA, comparative and correlation analyses were performed. Primary outcomes were the number of surgical failures (defined as delayed union, nonunion, or refracture) and time to radiographic union, weight bearing, and pain resolution. Data was analysed using independent T test, one-way ANOVA, chi-square, and correlation analyses with significance defined as p<0.05. RESULTS: 59 feet in 58 patients were identified with a mean age of 30 years and average follow-up of 9.6 months. The pooled union rate was 96.6%. The mean MAA was 20.9 (SD 6.7). Eleven feet had MAA<15, 18 mild (MAA 15-20), 12 moderate (MAA 20- 25), 18 severe (MAA>25), and 1 unknown. 11 patients had failures (18.6%), which consisted of 7 delayed unions (11.9%), 2 delayed unions (3.4%), and 3 refractures (5.1%). Compared to the uncomplicated unions, there was no significant difference in mean MAA (24.3 vs. 20.1, p=0.16). Three of the 4 non-union or refracture patients had MAA>25. MAA was correlated with time to weight bearing (r=0.365, p=0.005), weight (r=0.503, p<0.001), BMI (r=0.280, p=0.03), and approached significance with age (r=0.230, p=0.082). No significant correlation was found with time to radiographic union. CONCLUSION: To our knowledge, this is the largest series investigating MAA in fifth metatarsal Jones fracture patients treated with intramedullary screw fixation. Our mean MAA is consistent with previous reports. We found an association between increased MAA and postoperative recovery time, given increased time to initiate weight bearing. We did not find significant associations with prolonged radiographic healing, age, nor failure. The prolonged time to weight bearing may reflect surgeon preference in patients with higher MAA. These results suggest that reported associations with MAA may not be as strong as previously thought.