The awareness of hindfoot malalignment on non-weight-bearing ankle MRI.

OBJECTIVE: Hindfoot malalignment is a relatively common clinical finding and several studies have suggested that hindfoot valgus can be identified on non-weight-bearing ankle MRI. The aim of this study was to determine the awareness of hindfoot malalignment on ankle MRI amongst consultant musculoskeletal radiologists. MATERIALS AND METHODS: All MRI studies referred by Foot and Ankle Unit Consultants reported by one of 14 consultant musculoskeletal radiologists between March 2016 and August 2019 were retrieved from the Hospital Radiology Information System. These were reviewed independently by a radiology fellow and a consultant radiologist. Tibiocalcaneal angle (TCA) was measured, and extra-articular talocalcaneal (EA-TCI) and calcaneofibular impingement (EA-CFI) were recorded. Radiology reports were then analysed for mention of hindfoot malalignment and the presence of EA-TCI and EA-CFI. RESULTS: The study group comprised 129 patients, 46 males and 83 females with a mean age of 46.8 years (range 8-84 years). Based on review, hindfoot valgus was present in 78-80 cases (60.5-62%), EA-TCI in 30-36 cases (23.2-27.9%) and EA-CFI in 18-21 cases (14-16.3%). By comparison, MRI reports mentioned hindfoot valgus in 18 cases (2 incorrectly), EA-TCI in 8 cases (1 incorrectly) and EA-CFI in 10 cases (1 incorrectly). CONCLUSION: Hindfoot valgus, EA-TCI and EA-CFI were present relatively commonly on review of ankle MRI studies in patients referred from a specialist Foot and Ankle Unit but were commonly under-reported highlighting a relative lack of awareness of hindfoot malalignment on ankle MRI amongst musculoskeletal radiologists, which could impact negatively on patient management.

3D imaging for hindfoot alignment assessment: a comparative study between non-weight-bearing MRI and weight-bearing CT.

PURPOSE: The authors compared measurements of hindfoot alignment on MR imaging with weight-bearing CT (WB-CT) to establish the degree of correlation. Forty-seven feet in 44 patients had weight-bearing CT and MRI studies performed on the same day. MATERIALS AND METHODS: Hindfoot alignment on MRI was assessed by two radiologists who calculated tibiocalcaneal angle (TCA) and calcaneofibular ligament angle (CFLA). On WB-CT, foot ankle offset (FAO), calcaneal offset (CO) and hindfoot angle (HA) were assessed by a senior Foot and Ankle Surgeon using dedicated software. Pearson correlation coefficient was used to evaluate the correlation between these measurements. RESULTS: The study group comprised 27 males and 17 females with a mean age of 45 years (range 13-79 years). A statistically significant positive correlation was identified between TCA on MRI and all measurements of hindfoot alignment on WB-CT (p = 0.001-0.005). The CFLA on MRI only had significant correlation with CO on WB-CT (p = 0.03). A significant negative correlation was observed between both MRI parameters (p < 0.001). CONCLUSION: A highly significant correlation between tibiocalcaneal angle on non-weight-bearing ankle MR imaging and hindfoot alignment measurements on weight-bearing CT was identified.