AnIn VitroBiomechanical Comparison of a Prototype Intramedullary Pin‐Plate with a Dynamic Compression Plate for Equine Metacarpophalangeal Arthrodesis

Abstract

To compare the biomechanical properties of a prototype intramedullary pin-plate (IMPP) implant specifically designed for equine metacarpophalangeal (MCP) arthrodesis with a dynamic compression plate (DCP) system. In vitro biomechanical testing of paired cadaveric equine forelimbs with a simulated traumatic disruption of the suspensory apparatus, stabilized by one of two methods for MCP arthrodesis. Twenty-one pairs of adult equine cadaveric forelimbs. Each forelimb had the distal sesamoidean ligaments severed to create a disrupted suspensory apparatus. For each forelimb pair, the MCP joint was stabilized with the IMPP in one limb, and a DCP in the other limb. Seven matching limb pairs were tested in axial compression in a single cycle to failure, 7 matching limb pairs were tested in torsion in a single cycle to failure, and 7 matching limb pairs were fatigued tested in axial compression. Mean test variable values for each method were compared using a paired t-test within each group. Significance was set at P<.05. The mean yield load, yield stiffness, and failure load (axial compression, torsional loading) was significantly greater for the IMPP compared with the DCP system. Mean cycles to failure for axial compression was significantly greater for the IMPP compared with the DCP system. Significance in all tests was P<.0001. The IMPP was superior to the DCP system in resisting the biomechanical forces most likely to cause failure of MCP joint arthrodesis. The IMPP implant should be considered for MCP arthrodesis in horses with traumatic disruption of the suspensory apparatus. The specific design of the IMPP implant may facilitate equine MCP arthrodesis and avoid convalescent complications related to cyclic fatigue.