Factors predicting secondary displacement after non-operative treatment of undisplaced femoral neck fractures

Introduction We quantified the risk and the time of occurrence of secondary fracture displacement in non-operatively treated femoral neck fractures in our clinic, as well as investigated potential predicting patient- and fracture-related factors. Methods The records of 593 patients with femoral neck fractures from January 2000 to December 2009 were reviewed. Sixty-one patients [mean age 83.0 years (SD 9.9)] with undisplaced femoral neck fractures initially received non-operative treatment. The occurrence and the time of secondary fracture displacement were documented, as well as demographics and radiological parameters. Radiographs were evaluated independently by two surgeons. Multivariable regression and Kaplan–Meier survival analyses were used. Results Thirty-four (55.7 %) fractures showed secondary displacement occurring within the first 12 weeks after initiation of non-operative treatment. Twenty (38 %) fractures originally classified as Garden I were found to be Garden II. The risk of secondary displacement was three times higher (RR = 2.8; 95 % CI 1.7–4.8, p