The foot has a wide range of normal motion, including flexion, extension, inversion, and eversion. In addition, supination and pronation are part of the normal range of foot motion. The foot contains two arches: a longitudinal arch (midfoot) and a transverse arch (forefoot). Weight is normally distributed equally on the forefoot and the heel. Weight is not equally distributed on the metatarsal heads because the first bears twice as much weight as the remaining four. The maximum weight applied to the foot occurs during the push-off phase of walking and running.
The foot contains 28 bones and 57 articulations (Figs. 23–1 and 23–2). Conceptually, the foot can be divided into three regions: the hindfoot (talus and calcaneus), the midfoot (navicular, cuneiforms, and cuboid), and the forefoot (metatarsals and phalanges).
The foot is divided into a hindfoot, a midfoot, and a forefoot. Chopart joint separates the hindfoot from the midfoot, and Lisfranc joint separates the midfoot from the forefoot.
A. Medial. B. Lateral views of the foot.
Foot fractures are common and account for 10% of all fractures. They are generally the result of one of three basic mechanisms of injury—direct trauma, indirect trauma, and overuse.
The Ottawa foot rules recommend a radiographic series of the foot if there is bony tenderness at the base of the fifth metatarsal or over the tarsal navicular and if the patient is unable to take four steps both immediately and in the emergency department (ED).1 These rules apply to just the midfoot. Routine radiographs of the foot include the anteroposterior (AP), oblique, and lateral views (Fig. 23–3). These radiographs can be difficult to interpret because bones overlap in all projections. The AP radiograph is used to best assess the medial two tarsometatarsal joints, whereas the oblique image provides the best view of the lateral three tarsometatarsal joints.2 This alignment is important and will be altered in patients with Lisfranc fracture–dislocations. The lateral radiograph is best for detecting calcaneus fractures. Advanced imaging will be required with certain injuries and conditions. There is conflicting evidence of the overall effectiveness of bedside ultrasonography in the evaluation of potential foot and ankle fractures.3,4
Normal radiographs of the foot. A. Anteroposterior (AP). B. Oblique. C. Lateral images.
The radiologic diagnosis of foot fractures is frequently complicated by the secondary ossification centers and sesamoids (Fig. 23–4). Commonly seen sesamoids include the os trigonum, os tibiale externum, os peroneum, and os vesalianum. Sesamoids can be distinguished from fractures by their smooth sclerotic bony margins.