Comparative biomechanical analysis of equine accessory carpal bone fracture repair: Cortical screws in lag fashion versus X-plate technique.
Authors: Gernhardt Jennifer, Reuter Thomas, Mählmann Kathrin, Schulze Nicole, Lischer Christoph J
Journal: Veterinary surgery : VS
Summary
# Editorial Summary: Accessory Carpal Bone Fracture Fixation Vertical plane fractures of the accessory carpal bone present a challenging surgical problem in equine practice, with limited evidence comparing fixation approaches. Gernhardt and colleagues conducted a biomechanical cadaveric study comparing two surgical techniques: traditional two-screw lag fixation versus a hybrid approach combining a single lag screw with lateral plate augmentation, testing ten specimens per group to failure under axial compression loading. Both methods demonstrated equivalent load-to-failure capacity (cortical screws: 6.82 kN; X-plate hybrid: 8.02 kN; p=0.7558), though neither approached the strength of intact bone (11.26 kN). Critically, failure analysis revealed that two-screw constructs experienced significantly greater fracture gap displacement and implant bending, indicating less stable fracture reduction despite equal maximum load tolerance. For practitioners, the lateral X-plate technique offers comparable biomechanical performance with reduced operative complexity and less screw protrusion risk, making it a practical alternative that may improve intraoperative feasibility without sacrificing stability—though long-term clinical outcomes and functional recovery remain to be established.
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Practical Takeaways
- •For vertical plane accessory carpal bone fractures, a lateral X-plate with single cortical screw offers equivalent stability to two cortical screws with simpler application and fewer technical demands
- •Both repair techniques achieve similar functional strength (~60% of native bone), so surgical choice can be based on ease of application and surgeon familiarity rather than biomechanical superiority
- •Careful screw placement is critical as cortical screw protrusion occurred in 20% of cases—consider X-plate technique to reduce this complication risk
Key Findings
- •Native accessory carpal bone withstood mean maximum load of 11.26 kN; cortical screw group achieved 6.82 kN and X-plate group 8.02 kN with no significant difference (p=0.7558)
- •X-plate constructs showed smaller fracture gap size and less implant bending compared to cortical screw-only fixation (p=0.0039 and p=1.074e-7 respectively)
- •Neither surgical technique restored native bone strength, with both achieving approximately 60% of original strength
- •Cortical screw protrusion complications occurred in 2 specimens per group, requiring exclusion from analysis