Risk factors and early onset predictors of contralateral hip fractures following initial treatment of the other hip fracture

BACKGROUND: This study aims to investigate the risk factors and onset timing of second contralateral hip fractures (SHFx) following initial femoral fractures, with a particular focus on early events occurring within one year. METHODS: This retrospective study utilized a nationwide hospital claims database (Medical Data Vision, MDV) covering over 30% of all Diagnosis Procedure Combination (DPC) hospitals in Japan. MDV data combining patients who had visited a healthcare facility for osteoporosis with fractures (International Classification of Diseases, 10th Revision [ICD-10] code M80) or femoral fractures (ICD-10 code S72) were used. Patients aged 40 years and older who underwent bipolar hip arthroplasty or open reduction and internal fixation between April 2008 and September 2024 were included (n = 370,227). Clinical and demographic data were collected, including comorbidities and medications related to QFracture, FRAX, and fall risk. RESULTS: The incidence of early second contralateral hip fractures (eSHFx) was 2.7% (n = 10,136). Multivariate logistic regression identified female, age (70-79, 80-89, ≥ 90 years), Bone Mass Index (BMI) < 18.5 kg/m2, Charlson Comorbidity Index (CCI) = 1 point, dementia, delirium, fracture history, steroid use, and sleeping pill use as significant risk factors for eSHFx. Among patients who developed SHFx, male, age ≥ 90 years, BMI < 18.5 kg/m2, CCI (1, ≥ 3 points), dementia, delirium, steroid use, and sleeping pill use were significantly associated with early rather than late onset. Fall-related factors were risk factors for eSHFx and factors that predisposed to eSHFx. Female was a risk factor for eSHFx, but the timing of SHFx was late. CONCLUSION: This study identified risk factors for eSHFx and factors influencing their timing. It is crucial to determine the optimal timing and method of intervention for each patient to select the most appropriate therapy.