AN ALGORITHM FOR ASSESSMENT OF FRACTURE DISPLACEMENT AND PIN POSITIONS IN FEMORAL-NECK FRACTURES

A method for determination of both the displacement of the femoral hea d and the position of the fixation device in fixed femoral neck fractu res is described. In routine AP and lateral radiographs of the hip, me asurements are made of femoral neck-shaft angle, the diameter of the f emoral head and neck, the distances from the center of the femoral hea d to the femoral neck axis and the distances from the femoral neck axi s to the fixating screws. From these values the position of the femora l head and the fixating screws are determined by geometric calculation s. A computer program in Q-BASIC was devised to perform the calculatio ns and to produce graphic displays of cross-sections of the femoral he ad and neck, with the displacement of the head and the screw positions indicated. The accuracy of the method was evaluated by a new method u sing axial radiographs of hip specimens, which were compared with the computer-plotted graphs of the femoral head and neck. The mean error o f the method was found to be +/- 5% of the femoral head diameter, simi lar to 2.5 mm.