Risk factors for second hip fractures among elderly patients

Hip fractures following falls by the elderly, which increase with age, are increasing in number annually. The incidence of refracture (second hip fractures) has been reported to be 5%-10% in Japan and is expected to increase with the aging of the population in the future. Therefore, through a retrospective cohort study, we attempted to clarify the risk factors associated with second hip fractures. A total of 400 patients were consecutively treated for hip fracture at a single orthopedic hospital between January 2001 and December 2007. We excluded 16 subjects: 11 patients who died within a year after a hip fracture and 5 who were < 50 years of age. The remaining 384 patients, consisting of 64 men and 320 women, were chosen as the study subjects. The mean age of the subjects at the time of the initial fracture was 83.1 +/- 9.0 years (range 51-102 years). Age, sex, interval between the two fractures, body mass index (BMI), length of bed-rest periods and of rehabilitation periods, living place after an initial fracture, and complicating diseases were determined from medical records. Furthermore, effectors of second hip fractures were extracted using the Cox proportional hazard model. In all, 384 patients were observed for 1140.0 person-years (mean: 3.0 +/- 1.4 years per patient) following the initial hip fracture. During the observation period, 49 second hip fractures were identified, giving an overall incidence of 0.043 per person-year. The second fracture occurred within 3 years in 85.7% (42 patients). Dementia and respiratory disease were recognized as being significantly related to refracture. Using a Cox proportional hazard model, dementia showed a significant influence, with the hazard ratio (HR) 1.87 [95% confidence interval (CI) 1.02-3.41; P = 0.042]. Respiratory diseases also were associated with second hip fracture (HR 4.41, 95% CI 2.33-8.34; P < 0.001). In this study, 85.7% of refractures occurred within 3 years of the first fracture, with dementia and respiratory disease being the complicating factors that influenced refracture.