Stress fractures of the lateral metatarsal bones in metatarsus adductus foot deformity: a previously unrecognized association

Objective. To document a distinctive pattern of stress fractures in the lat eral metatarsal bones of patients with metatarsus adductus foot deformity. Design and patients. Conventional radiographs and available medical records were reviewed in 11 patients (6 women, 5 men; ages 25-61 years) with stres s fractures of the lateral (fourth or fifth) metatarsal bones and metatarsu s adductus. Evaluation included the number and location of fracture(s), for efoot adduction angle, and qualitative assessment of bone mineral density. Conditions that might predispose patients to metatarsal fractures, includin g direct trauma, osteoporosis, and neuropathic osteoarthropathy were also r ecorded. Results. A total of 22 stress fractures were demonstrated, 17 of which invo lved the lateral metatarsals. A solitary fracture war present in six patien ts, while multiple fractures were evident in five patients. The sites of in volvement were the fifth metatarsal (n=10), fourth metatarsal (n=7), third metatarsal(n=3), second metatarsal (n=1), and first metatarsal (n=1) bones. The locations of the stress fractures were in the proximal one-third of th e metatarsal bones in 19 instances (86%) and in the middle one-third in thr ee instances (14%). Forefoot adduction angle measured between 21 degrees an d 37 degrees (normal range 8 degrees-14 degrees). Conclusion. Patients with metatarsus adductus may be at increased risk for stress fractures involving the lateral metatarsal bones, likely owing to th e presence of altered biomechanics that place greater loads across the late ral aspect of the foot.