Functional and Radiologic Outcomes Following Fifth Metatarsal Fracture Non-Operative Treatment: A Retrospective Chart Review with Application of the RUST Score From 2019-2021

CATEGORY: Midfoot/Forefoot; Sports; Trauma INTRODUCTION/PURPOSE: Fifth metatarsal fractures are a common injury of the foot, however, there remains a lack of consensus regarding the management of Zone I and II fifth metatarsal fractures. The evidence shows varied outcomes between operative management and non-operative interventions. Additionally, there is limited discussion on radiographic outcomes following these fractures, with no established scoring system to assess radiographic healing. The radiographic union scale in tibial (RUST) fractures is an assessment tool designed to standardize radiographic assessment and outcome measures based on cortical bridging. The aim of this study is to assess the functional and radiologic outcomes for patients with base of fifth metatarsal fractures (Zone I-III) utilizing the RUST score as a method for standardized assessment of radiographic healing. METHODS: We performed a secondary retrospective chart review of patients with base of fifth metatarsal fractures treated by six orthopedic surgeons at University of Colorado Orthopaedics from 2018-2021. We collected information on treatment modality and the functional, radiographic, and patient reported outcomes. Patients were included who attended minimum two visits and had x-ray available. The x-rays were read by a fellowship trained foot and ankle surgeon, and were assessed based on presence of displacement, resorption, and overall healing. The RUST scoring system was applied when fracture appeared healed and assessed on the four cortices (anterior, posterior, medial, and lateral) of the 5th metatarsal bone by assigning a score from 1 to 3 based on appearance. The scores were combined for a minimum of 4 (not healed) and a maximum of 12 (completely healed). Differences between outcomes were evaluated using an unpaired t-test and figures are reported with standard error. RESULTS: Out of 196 total patients, 109 were excluded due to shaft fracture or insufficient follow-up, leaving 87 non-operative patients with base of fifth metatarsal fractures available for analysis. Radiographically, the average time to resorption was 37 days and average time to healing was 98 days, which was significantly longer than when patients began weight bearing at 44 days (p<0.001), but not significantly different than return to normal shoe wearing at 75 days (p=0.077). While 96% of patients at visit 4 were weight bearing and wearing normal shoes, only 73% had radiographic healing. The average RUST score at visit 2 was 10.14 (n=21) improving to 10.5 (n=12) by visit 4. To note, only 30% of patients presented for all four visits and the average final follow- up was 106 days after injury. CONCLUSION: Patients treated non-operatively for base of fifth metatarsal fractures have significantly shorter timelines for functional healing compared to evidence of radiographic healing. Overall RUST score at visit 4 supports those patients did not reach full cortical healing as the average score was 10.5 out of 12 possible points. Most patients have signs of resorption on x-ray by their second visit, but many do not continue follow up for complete evidence of healing. This highlights the importance of functional healing in treatment decisions for Zone I and II fractures and overall good prognosis regardless of complete healing radiographically.