Background: In the past, patients admitted for hip fractures had often sustained a contralateral hip fracture. The incidence of bilateral hip fractures has been reported to be 5%-10%, and in the future the number of bilateral hip fractures is expected to increase with the increase of unilateral hip fractures. We believe that bilateral hip fractures can be efficiently prevented if a fracture on the other side could be predicted after unilateral hip fracture. Therefore, this retrospective study of 835 patients with hip fractures investigated the incidence, prognosis, and risk factors of bilateral hip fractures.
Methods: We examined 835 hip fractures retrospectively in Japan. Among them, we found 94 patients with bilateral noncontemporary hip fractures. We investigated age, sex, interval between the two fractures, type of fractures, cause, physical functioning, and complications. Differences between the unilateral fracture and bilateral fractures groups were analyzed statistically for age, sex, and complications using Student's t test and the chi-square test.
Results: In this study, the mean interval between two fractures was 4.28 years, and the second hip fracture occurred within 5 years in more than 70% of patients. The type of hip fracture was the same in 72.2% of bilateral hip fractures. No difference in age and sex was found between the unilateral and the bilateral groups. However, concerning complications, 22.1% of patients in the unilateral group and 34.8% in the bilateral group had dementia, the difference being significant.
Conclusions: These results revealed that the second hip fracture occurred within 5 years of the first in more than 70% of bilateral hip fracture patients and that dementia is a risk factor of bilateral hip fractures.