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

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. 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. 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 < 0.001) for these fractures in comparison with those confirmed as Garden I. Patients with a history of previously diagnosed osteoporosis were at a higher risk of secondary displacement as well (RR = 1.3; 95 % CI 1.0-1.5). Non-operative treatment of femoral neck fractures is a treatment option, but only in well-selected cases. The majority of secondary displacements were associated with initial misdiagnosis using the Garden classification. For Garden II, primary surgical treatment is likely a better option, and therefore careful application of the Garden classification in this context is essential.