Frontal plane slab fractures account for the majority of third carpal bone (C3) fractures in performance horses. Treatment is stabilization with an AO cortical screw. Complications are fragment splitting, fragment spinning, and irritation of dorsal soft tissue structures. A novel, headless, cannulated screw with interlocking threads (the Headless Compression Screw Fastener, HCSF) has been developed to resist multidirectional forces. Simulated C3 slab fractures were created in nine paired equine carpi. HCSF or AO cortical screws were loaded in shear to failure. Stiffness, maximum load to failure, and yield load was assessed in linear mixed models. No significant difference was detected in maximum load to failure, stiffness, or yield load. Mode of failure was screw bending in all specimens. The HCSF successfully repaired simulated third carpal bone fractures. The design eliminates counter sinking. There was no significant difference compared to the cortical screws. These results promote clinical application.