Risk factors for second hip fracture in elderly patients: an age, sex, and fracture type matched case-control study.

Purpose Prevention of second hip fracture is mandatory for orthopedic surgeons. We aimed to clarify the incidence and duration of second hip fracture, to compare survival rate and walking ability of patients with a second hip fracture to that of patients with a unilateral fracture, and to identify risk factors for second hip fracture using matched case-control methods. Methods This retrospective study conducted in a single tertiary emergency center comprised 119 patients with second hip fractures who underwent bilateral operations at our institution from 2007 to 2017 (second hip fracture group [Group A]). The control group (Group B) comprised 357 patients matched to Group A for age, sex, and fracture type. Results The incidence of second hip fracture was 7.6%, and the average interval from initial fracture to second hip fracture was 22.8 months. Significantly more patients in Group A had decreased postoperative walking ability. Five-year survival rates from initial fracture were 65.0% in Group A and 50.6% in Group B (P = 0.346). Dementia and heart disease were identified as independent risk factors (dementia: HR 2.08, 95% CI 1.27-3.41, P = 0.004; heart disease: HR 1.27, 95% CI1.11-3.22, P = 0.019). Valvular disease was also revealed to be a risk factor for heart disease (P = 0.0272). Conclusions The incidence of second hip fracture was not low. Although survival rates did not differ between the patients with or without second hip fracture, walking ability of patients with second hip fracture worsened. Dementia and cardiac disease could be risk factors for second hip fracture in elderly patients, and valvular disease might be associated with second hip fracture in patients with heart disease.