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.