Background: Instability of the first ray has been proposed by Morton and others to be a major cause of several foot disorders, including hallux valgus, transfer metatarsalgia, lesser metatarsal stress fractures, and second metatarsophalangeal diseases. However, there are few studies to support these theories. In this study, we have used a simple device to measure first ray elevation and translation in a consecutive series of foot and ankle patients. We propose that mobility of the first ray will be increased in patients with hallux valgus, metatarsalgia, hallux rigidus, lesser metatarsal stress fractures, posterior tibial tendinitis, and interdigital neuromas.
Methods: Measurements of first ray translation and elevation were made in 345 feet in 315 patients. One or more pathologic diagnoses were recorded for each foot, and data was analyzed by a statistician.
Results: First ray mobility was increased in females compared to males. Patients with hallux valgus and metatarsalgia had greater mobility than other patients. Those feet with low arches showed greater mobility than those with high arches. Patients with hallux rigidus showed decreased mobility. We failed to find any differences for patients with stress fractures, posterior tibial tendinitis, or neuromas, but some of these groups may have had insufficient power.
Conclusion: First ray translation and elevation are two different measures of medial column instability. Although they are distinct measures, they closely paralleled each other in this series. An association was found between increased first metatarsal elevation and several foot disorders. Although such an association does not prove causation, and it is likely other factors may play a role in many patients, this data does link instability of the first ray to some diseases. The decreased mobility seen in patients with hallux rigidus may offer new insights into the etiology of that disorder.