Strength of internal fixation for calcaneal fractures

OBJECTIVE: To compare the strength of two types of fixation method for calcaneal fractures. DESIGN: A biomechanical testing examined the stability of 12 fractured calcaneal specimens fixed with two different methods. BACKGROUND: Though anatomic reduction and internal fixation for the treatment of intra-articular fractures of the calcaneus has become popular, biomechanical data on the fixation strength is lacking. METHODS: Twenty fresh frozen specimens of amputated human legs were impacted by a 20 kg weight dropped from a 155 cm height to create calcaneal fractures. Twelve specimens which demonstrated a longitudinal and a transverse primary fracture lines were selected for open reduction and internal fixation. Group 1: a lateral buttress plate and parallel screws placed in the latero-medial direction were used. Group 2: a longitudinal screw was added in addition to the fixation used in group 1. Biomechanical testing was performed by applying a tibial shank load until the internal fixation failed. RESULTS: All mechanical failures of the reconstructed calcaneus occurred through the transverse primary fracture line. The average failure load was 805+/-356 N in group 1 and 2905+/-910 N in group 2 (Wilcoxon p<0.05). CONCLUSIONS: A longitudinal transfixing screw could significantly improve the stability of the transverse primary fracture line in calcaneal fractures.