Comparison of plate and screw fixation and screw fixation alone in a comminuted talar neck fracture model

BACKGROUND: Talar neck fracture fixation has been studied in noncomminuted fracture models, but no large clinical series of comminuted fracture patterns have been published and no biomechanical studies have compared plate fixation with screw fixation in comminuted talar neck fractures. METHODS: Nine matched pairs of fresh frozen talar specimens were stripped of soft tissue and mounted in a cylindrical jig. The talar neck was fractured using a dorsally directed shear force at a rate of 200 mm/min, and dorsal comminution was simulated by removing a 2-mm section of bone from the distal fracture fragment. One specimen from each pair was fixed with either two solid 4.0-mm partially threaded cancellous screws posterior-to-anterior just lateral to the posterior process of the talus or with a four-hole 2.0-mm minifragment plate contoured to the lateral surface of the talar neck and secured with 2.7-mm screws. A 2.7-mm fully threaded cortical screw was placed medially using a lag technique. The specimens were then loaded to failure with a dorsally directed force at a rate of 200 mm/min. Failure was defined as the load producing 2 mm of displacement. A Student's t-test analysis was used with significance set at p < or = 0.05. RESULTS: Posterior-to-anterior screw fixation had a statistically significant higher load to failure than plate fixation (p < 0.05). Mean load to failure for the screw group was 120.7 +/- 68.5 N and 89.7 +/- 46.6 N for the plating group. CONCLUSIONS: Plate fixation may offer substantial advantages in the ability to control the anatomic alignment of comminuted talar neck fractures, but it does not provide any biomechanical advantage compared with axial screw fixation. Further, the fixation strength of both methods was an order of magnitude lower than those found in previous studies of noncomminuted fractures.