Radiographic Assessment of First Tarsometatarsal Joint Shape and Orientation

Abstract

Background: Hypermobility within the first tarsometatarsal (TMT) joint is a predisposing factor for hallux valgus. The purpose of this study was to assess whether the shape and angulation of the first TMT joint are affected by the positioning of the foot in radiographs. Methods: Ten adult above-knee fresh-frozen cadaveric specimens were placed into a radiolucent apparatus that allowed controlled angulation of each foot at 0, 5, 10, 15, and 20 degrees in dorsiflexion, plantarflexion, inversion, and eversion. For each specimen, the first TMT joint angle (1TMTJA), shape of the distal articular surface of the medial cuneiform (flat or curved), and image quality of the first TMT joint were measured. Results: The mean value for 1TMTJA was 22.9 degrees (95% confidence interval [CI] 21.9-24). Individual anatomical variations of the specimens as well as the different angulations due to foot positioning significantly influenced the 1TMTJA (both P