An in vitro biomechanical comparison of a prototype intramedullary pin-plate with a dynamic compression plate for equine metacarpophalangeal arthrodesis.

This research article compares the biomechanical properties of two different orthopedic implants used for fusing metacarpophalangeal (MCP) joints in horses – the prototype intramedullary pin-plate (IMPP) and the dynamic compression plate (DCP) system. The IMPP implant was found to be superior in resisting biomechanical forces associated with joint failure in horses with a disrupted suspensory apparatus.

Objective and Methodology

• The main objective of the study was to compare the biomechanical properties of a prototype intramedullary pin-plate (IMPP) implant designed specifically for equine metacarpophalangeal (MCP) arthrodesis with a dynamic compression plate (DCP) system.
• In the in vitro experiment, paired cadaveric equine forelimbs were tested under various conditions. Equine forelimbs were prepared by severing the distal sesamoidean ligaments to mimic a disrupted suspensory apparatus. Then, for each pair, the MCP joint was stabilized with the IMPP in one limb and a DCP in the other.
• Three types of tests were conducted: Axial compression in a single cycle to failure, torsion in a single cycle to failure, and fatigue testing in axial compression. Each type of test was performed on seven matching limb pairs.
• The mean test variable values for each method were compared using a paired t-test within each group. The level of statistical significance was set at P<.05.

Results and Conclusions

• The results showed that the IMPP significantly outperformed the DCP system in terms of mean yield load, yield stiffness, and failure load in both axial compression and torsional loading tests. Furthermore, the IMPP was found to withstand more cycles to failure in axial compression compared to the DCP system.
• These results indicate that the IMPP was superior to the DCP system in resisting biomechanical forces that are most likely to cause failure of MCP joint arthrodesis, effectively meaning that the IMPP could provide greater stability and durability in cases of horse MCP joint injuries.
• Given these results, the researchers concluded that the IMPP implant should be considered for MCP joint arthrodesis in horses with traumatic disruption of the suspensory apparatus. They also suggested that the specific design of the IMPP implant may facilitate equine MCP arthrodesis and help avoid convalescent complications related to cyclical fatigue in the joint.