Two or three screws for fixation of femoral neck fractures?

This study compares the stability of 3 cannulated cancellous lag screws with that of 2 cannulated cancellous lag screws for fixation of subcapital femoral neck fractures. Using 10 matched pairs of human cadaveric femurs, subcapital femoral neck osteotomies were created, reduced, and then randomized to 1 of the 2 fixation methods. The constructs were tested with anterior loading to 500 N, incremental axial loading from 100 N to 1000 N, and cyclic loading at 1000 N. The specimens stabilized using 3 screws showed greater resistance to anterior loading, less inferior femoral head displacement, and less superior gapping at the osteotomy site. Although 2 screws may be an acceptable fixation method for this fracture type, the addition of a third screw provides supplemental stability and appears justified.