A new measurement for posterior tilt predicts reoperation in undisplaced femoral neck fractures

BACKGROUND AND PURPOSE Preoperative posterior tilt in undisplaced (Garden I-II) femoral neck fractures is thought to influence rates of reoperation. However, an exact method for its measurement has not yet been presented. We designed a new measurement for posterior tilt on preoperative lateral radiographs and investigated its association with later reoperation. PATIENTS AND METHODS A consecutive series of 113 patients, > or = 60 years of age with undisplaced (Garden I-II) femoral neck fractures treated with two parallel implants, was assessed regarding patient characteristics, radiographs, and rate of reoperation within the first year. In a subgroup of 50 randomly selected patients, reliability tests for measurement of posterior tilt were performed. RESULTS Intra- and interclass coefficients for the new measurement were > or = 0.94. 23% (26/113) of patients were reoperated and increased posterior tilt was an accurate predictor of failure (p = 0.002). 14/25 of posteriorly tilted fractures > or = 20 degrees were reoperated, as compared to 12/88 of fractures with less tilt (p < 0.001). In multiple logistic regression analysis including sex, age, ASA score, cognitive function, new mobility score, time from admission to operation, surgeon's expertise, postoperative reduction, and implant positioning, a preoperative posterior tilt of > or = 20 degrees was the only significant predictor of reoperation (p < 0.001). INTERPRETATION The new measurement for posterior tilt appears to be reliable and able to predict reoperation in patients with undisplaced (Garden I-II) femoral neck fractures.