An ex vivo comparison of mono-versus polyaxial locking compression plates for metacarpophalangeal joint arthrodesis in the horse.

Objective: The aim of the study was to determine if a novel arthrodesis technique for the equine metacarpophalangeal (MCP) joint using a human non-contact bridging (NCB), polyaxial locking compression plate system has biomechanical and potential clinical advantages versus a traditional 5.5 mm stainless steel locking compression plate (LCP) under biomechanical testing.

Study design: An ex vivo biomechanical equine cadaver study.

Sample population: A total of 11 MCP joints collected from adult Thoroughbred horses euthanized unrelated to musculoskeletal disease.

Methods: Each pair of MCP joints were randomly implanted with either an A LCP or NCB plate. Each construct was tested in cyclic loading followed by single cycle to failure in axial compression. Displacement at a target load of 1 kN over 3600 cycles at 1 Hz was recorded prior to single cycle to failure testing.

Results: In cyclic testing, overall displacement recorded in constructs with the NCB plates was less than that of the LCP constructs with a mean (least square mean - LSM) difference of 0.33 mm (p = .03). There was no difference between groups in single cycle testing for yield point (p = .55) and maximum load at failure (p = .95).

Conclusion: While a significant difference was found between constructs during cyclic testing, LCP versus NCB constructs conferred no difference in stability in single cycle to failure testing.

Clinical significance: The increased stability of the NCB plate in cyclic loading, comparable failure strength to the LCP and versatility of polyaxial screws support further investigation for possible clinical use of the NCB plate for equine fetlock arthrodesis.