Role of metatarsus primus elevatus in the pathogenesis of hallux rigidus.

Metatarsus primus elevatus has been suggested as a primary causative factor in the pathogenesis of hallux rigidus. The purpose of this investigation was to define the role of elevation of the first ray in the pathogenesis of hallux rigidus by comparing patients with known hallux rigidus with a control population. We reviewed 264 lateral weightbearing radiographs from 81 patients with hallux rigidus, 50 asymptomatic volunteers, and 64 patients diagnosed with isolated Morton's neuroma. Results revealed that the mean values for elevation of the first ray in patients with mild or moderate hallux rigidus were nearly identical to those in the control group. Patients with advanced radiographic hallux rigidus had a slightly higher mean value for metatarsus primus elevatus. An average of nearly 8 mm of metatarsus primus elevatus is a normal finding in patients with hallux rigidus as well as in normal subjects. This investigation did not address the clinical outcome or biomechanical effects of a plantarflexion osteotomy of the first ray. However, on the basis of the finding that first ray elevation is normal, it seems unlikely that a plantarflexion osteotomy would have a role in the treatment of hallux rigidus.