Objective: The purpose of this study was to compare the mechanical stability of cannulated conical variable pitch headless (CH) screws to partially threaded 4.0 cannulated (4.0 C) screws for fixation of talar neck fractures. Methods: A controlled talar neck fracture was produced in 24 sawbone tali. The fractures were stabilized with CH screws in 12 tali and with 4.0 C screws in 12 tali. A Mechanical Testing System machine was used to apply a dorsally-directed shear force to the talar head with the talus body fixed to simulate walking and the clinical mode of failure of talar neck fracture fixation. Stiffness of the fixation devices was calculated for each specimen and the groups statistically compared. The results were confirmed in 10 cadaveric bone specimen. Results: The fixation of talar neck fractures by the CH screws was significantly stiffer than the 4-0 C screw (mean 635 N and 335 N, respectively, P < 0.05). Conclusions: The results of this study support the clinical use of the cannulated conical headless variable pitch screw for talar neck fracture fixation. The improved fixation of this device is likely to decrease the incidence of fixation failure and poor clinical results due to malunion, nonunion,and stiffness. The CH can be placed using the same surgical exposure and ease of a 4.0 C screw,while eliminating the problem of screw head prominence.
DeCoster, Thomas; Keikhosrow Firoozbaksh; Deana Mercer; Selina Silva; Jennifer Fitzpatrick; and Dylan Watson. "Stability of Talar Neck Fracture Fixation: A Biomechanical Comparison of 4.0 Cannulated Headed Screws and Conical Headless Screws." (2009). http://digitalrepository.unm.edu/ume-research-papers/91