Comparative biomechanical analysis of equine accessory carpal bone fracture repair: Cortical screws in lag fashion versus X-plate technique

Objective To compare the feasibility and biomechanical stability of two surgical techniques for fixation of vertical plane fractures of the accessory carpal bone (ACB). Study design Randomized experimental ex vivo study. Sample population Eight equine accessory carpal bones were included in a control group. A total of 20 equine cadaveric forelimbs were randomly assigned into two groups (n = 10 per group). Methods Vertical plane fractures were created palmar to the extensor sulcus using an oscillating saw. In Group 1 (CS), fractures were stabilized with two 4.5 mm cortical screws in lag fashion. In Group 2 (XP), fixation included one 4.5 mm cortical screw in lag fashion and a laterally applied angular stable X-plate with four 2.7 mm locking screws. Control ACBs were excised and tested under axial compression using a four-column testing machine. Postoperative specimens in Groups CS and XP were tested under the same conditions. The failure mode was assessed radiographically. Results The mean maximum strength of native bone was 11.26 (±2.14) kN. Two constructs per group were excluded due to cortical screw protrusion. No difference in failure load was observed (CS: 6.82 ±2.34 kN; XP: 8.02 ±1.10 kN; p = .7558). Failure mode analysis revealed a greater fracture gap size (p = .0039) and implant bending in CS specimens (p = 1.074e-7). Conclusion Both techniques were feasible, though neither restored native bone strength. Clinical significance A lateral X-plate with a single cortical screw demonstrated equivalent biomechanical performance to two cortical screws and was technically less demanding, offering a simpler fixation option for ACB fractures.