Screw augmentation in displaced femoral neck fractures. Clinical and histological results using a new composite.

We wanted to assess a new technique for augmentation of parallel screws in internal fixation of displaced femoral neck fractures with a bis-GMA-based composite delivered around the screw head. Twenty-one consecutive patients admitted with displaced femoral neck fractures were operated with internal fixation with two parallel Olmed screws augmented with the composite, and followed for 24 months. The composite was introduced through the lumen of the cannulated screws and deposited in the femoral head around the threaded part of the screws. The procedure of augmenting was technically feasible and operation time was on average 33 min. Eleven patients were re-operated due to healing complications within 24 months. There were five redisplacements, four non-unions and two cases of avascular necrosis. Histological examination of four extracted femoral heads showed fragmentation of the composite into small particles with foreign-body response with giant cells and macrophages along with granulation tissue formation and low grade inflammation. The method of augmentation was technically easy, but the failure rate was high and the fragmentation of the composite with inflammatory response found on histology is noteworthy.