Success of Cannulated Screw Fixation of Subcapital Neck of Femur Fractures

In this study we retrospectively reviewed 251 patients who had internal fixation for neck of femur fracture using cannulated screws. Twenty were lost to follow-up or died soon after surgery. The fracture was displaced in 114 (49.9%) and undisplaced in 117 (50.6%) patients. There were 65 males and 171 females with an average age of 75.7 years. Average follow-up was 12 months. Of the 117 patients with undisplaced fractures 75 (64.1%) healed uneventfully. Further surgery was performed in 21 (17.9%) patients. In the 114 patients with displaced fractures, satisfactory reduction was achieved in 74 patients and of these 54 had good screw placement. Fifty-one (44.7%) patients healed uneventfully. Twenty-two (20%) of the 114 displaced fracture patients required further surgery. Forty (35%) had an unsatisfactory reduction and, of these, 26 (65%) had poor screw placement. Re-operation rates were 17.9% and 20% respectively. The rate of AVN was similar in both fracture types (10.3%-11%), but the rate of non-union was four times higher (2.6%-11.5%) in displaced subcapital fractures. The most important factors within the control of the surgeon that influence the rate of healing are adequate reduction and correct placement of the screws. In this series the reduction was unsatisfactory in 40 (35%) cases of the displaced NOF fractures, and the screws were incorrectly positioned in 46 (40.4%) of the 114 displaced fractures compared with 11 (9.4%) of the 117 undisplaced fractures. This highlights the importance of adequate reduction to enable correct screw placement in displaced fractures.