Fixation of calcaneal avulsion fractures using screws with and without suture anchors: a biomechanical investigation.

BACKGROUND: Lag screw fixation commonly is used to treat avulsion fractures of the posterior calcaneal tuberosity, but this method may not offer reliable fixation. This study compared the strength to failure of lag screws compared to lag screw fixation augmented with suture anchors in these fractures.

METHODS: The calcanei and Achilles tendons of 12 fresh lower extremity cadaver matched pairs were dissected and removed. An oblique osteotomy was created in the calcaneus, and two 4.0-mm lag screws were placed nearly perpendicular to the plane of the fracture in the dorsal aspect of the calcaneus with 30 degrees of divergence between them. In the contralateral specimen, the same procedure was done, but with two suture anchors placed 1.5 to 2 mm distal to the osteotomy. A zigzag suture technique through the Achilles tendon was used. The specimens were mounted and placed in a load frame for monotonic loading to failure. A paired Student t-test and a Pearson correlation were used to analyze the data (p <or= 0.05).

RESULTS: The specimens treated with lag screws alone failed at 251.3 (range 66 to 459) N whereas specimens repaired with lag screws and suture anchors failed at 441.6 (range 274 to 661; p = 0.01 N).

CONCLUSIONS: Suture anchor augmentation significantly improved the strength of screw fixation of the calcaneal posterior tuberosity avulsion fractures.

CLINICAL RELEVANCE: The use of suture anchor augmentation as described may improve the reliability of fixation in avulsion fractures of the posterior calcaneal tuberosity.