Role of the weight-bearing cone-beam CT in evaluation of flatfoot deformity

Introduction: Till date, weight-bearing radiographs have been the cornerstone for planning surgeries on flatfoot. The technique, however, has limitations due to the superimposition of the bones and the lack of reproducibility. Weight-bearing CT with its unique design overcomes these limitations and enables cross-sectional imaging of the foot to be done in the natural weight-bearing position. In this paper, we report our initial experience in weight-bearing cross-sectional imaging of the foot for assessment of flatfoot deformity. Materials and Methods: Around 19 known cases of flatfoot were scanned on the weight-bearing CT. Each foot was then assessed for the various angles and also for the presence/absence of extra-articular talocalcaneal impingement and subfibular impingement. Other associated abnormalities like secondary osteoarthritic changes, were also noted. Results: The Meary, as well as the calcaneal angles, were abnormal, in all but one separate foot. Forefoot abduction was seen in 7 of the 19 feet. The hind foot valgus angle was greater than 10 degrees in all patients. Extra-articular talocalcaneal impingement was seen in 13 of 19 feet. Secondary osteoarthritic changes were seen in 14 feet. Conclusion: Weight-bearing CT scan is a very useful technique for evaluation of flatfoot and associated complications. It overcomes the limitations of the radiographs by providing multiplanar three-dimensional assessment of the foot in the natural weight-bearing position and at the same time being easily reproducible and consistent for the measurements around the foot. The definite advantage over the conventional cross-sectional scanners is the weight-bearing capability.