The influence of a tension band fixation as an adjunct for arthrodesis of the metacarpophalangeal joint in the horse

Abstract

Objectives: To determine the influence of a stainless-steel cable (SSC) tension band fixation as an adjunct to a locking compression plate (LCP) for arthrodesis of the equine metacarpophalangeal (MCP) joint. Study design: Experimental. An ex vivo biomechanical paired equine cadaver limb study. Sample population: Five MCP joint pairs were collected from adult Thoroughbred horses, euthanized for reasons unrelated to orthopedic disease. Methods: Each pair of MCP joints were randomly implanted with either a dorsally placed 5.5 mm LCP and a palmarly placed 2.0 mm SSC or a dorsally placed 5.5 mm LCP alone. 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, displacement was not significantly different between the first and last 5% of testing cycles regardless of construct. Maximum displacement of each construct during cyclic testing was <1.1 mm. In single cycle testing, the observed yield point did not reveal any difference between LCP and LCP-SSC (p =.440). The maximum load at failure was significantly higher in LCP-SSC compared to constructs with the LCP alone (p =.046). Conclusion: The addition of the SSC to the LCP did not statistically affect construct displacement during cyclic loading or construct yield load during subsequent single cycle to failure. Clinical significance: This study provided much needed information regarding the necessity of a tension band SSC application in the arthrodesis of the MCP/MTP joint in horses.