Foot and ankle fractures in elderly white women. Incidence and risk factors

Although foot and ankle fractures are among the most common nonspinal fractures occurring in older women, little is known about their epidemiology. This study was designed to determine the incidence of and risk factors for foot and ankle fractures in a cohort of 9704 elderly, nonblack women enrolled in the multicenter Study of Osteoporotic Fractures.

At their first clinic visit, between 1986 and 1988, the women provided information regarding lifestyle, subjective health, and function. Bone mineral density was measured in the proximal and distal parts of the radius and in the calcaneus. The women were followed for a mean of 10.2 years, during which time 301 of them had a foot fracture and 291 had an ankle fracture. The fractures were classified with use of a modification of the Orthopaedic Trauma Association's guidelines.

The incidence of foot fractures was 3.1 per 1000 woman-years, and the incidence of ankle fractures was 3.0 per 1000 woman-years. The most common ankle fracture was an isolated fibular fracture (prevalence, 57.6%), and the most common foot fracture was a fracture of the fifth metatarsal (56.9%). Women who sustained an ankle fracture had been slightly younger at the time of study enrollment than the women who did not sustain such a fracture (71.0 compared with 71.7 years), they had a higher body mass index (27.6 compared with 26.5), and they were more likely to have fallen within the twelve months prior to filling out the original questionnaire (38.1% compared with 29.7%). The appendicular bone mineral density was not significantly different between these two groups of subjects. Women who sustained a foot fracture had a lower bone mineral density in the distal part of the radius (0.345 g/cm (2) compared with 0.363 g/cm (2) ) and a lower calcaneal bone mineral density (0.394 g/cm (2) compared with 0.404 g/cm (2) ) than the women without a foot fracture, they were less likely to be physically active (62.3% compared with 67.8%), and they were more likely to have had a previous fracture after the age of fifty (45.5% compared with 36.8%) and to be using either long or short-acting benzodiazepines.

Overall, foot fractures appeared to be typical osteoporotic fractures, whereas ankle fractures occurred in younger women with a relatively high body mass index.