Three-dimensional analyses to predict surgical outcomes in non-displaced or valgus impaction fractures of the femoral neck: A multicenter retrospective study

The aim of our study was to (1) report our surgical outcomes of internal fixation in patients with non-displaced or valgus impaction fractures of the femoral neck, (2) introduce our new three-dimensional assessment method using a combination of X-ray and CT imaging, and (3) determine which radiologic measurements significantly predicted fixation failure. We hypothesized that high posterior tilt angle and retroversion angle are related to high incidence of non-union and osteonecrosis. From January 2009 to December 2016, 64 elderly patients in two institutions with non-displaced or valgus impaction fractures of the femoral neck who had internal fixation using multiple parallel cannulated screws were enrolled. To determine the independent predictors of non-union, osteonecrosis, and re-operation, various clinical variables and radiologic variables, including the valgus angle on coronal CT images, the posterior tilt angle on Lorenz images, and the retroversion angle on axial CT images, were analyzed. Non-union was identified in nine of the 64 patients (14.1%) and nine of the 55 patients (16.4%) who achieved bony union had femoral head osteonecrosis with subsequent segmental collapse. The multiple logistic regression model showed that a low bone mineral density of the femur, a higher posterior tilt angle on Lorenz image, and a higher retroversion angle on axial CT images were independent predictors of non-union and re-operation. Primary hip arthroplasty should be considered when a posterior tilt angle of more than 9 degrees on Lorenz images or a retroversion angle of more than 13 degrees on axial CT images is identified in patients with osteoporotic valgus impaction fractures. III, Retrospective comparative study.