Minimally Invasive Arthrodesis of the Equine Proximal Interphalangeal Joint: A Biomechanical Comparison of Three 5.5-mm Cortical Screws Inserted in Lag Fashion and Two 7.0-mm Headless Cannulated Dual-Pitch Compression Screws.

This study investigated the structural differences between two less invasive surgical techniques used in the fusion of the horse’s proximal interphalangeal joint, evaluating their respective mechanical properties through non-destructive and compression testing until the point of failure.

Methods

• The study involved six pairs of cadaveric adult horse forelimbs. Each limb from each pair was randomly assigned one of two treatment methods, while its counterpart underwent the remaining procedure.
• Three 5.5-mm cortical screws (known as AO-3TLS), and two 7.0-mm headless cannulated multi-use compression screws (MUC-2TS), both transarticular, were used for the arthrodesis.
• The dynamic test was performed through alternating non-destructive compression tests at a displacement rate of 5 mm/min up to a load of 5,000 N. There were also sinusoidal compressive cyclic tests carried out at 6 Hz, making use of a 3,600-N amplitude lasting 8,550 cycles.
• The study measured construct stiffness and maximum sagittal plane rotation around the PIP joint markers during the dynamic test.
• After reaching 136,800 cycles in the dynamic test, a compressive test until failure was performed on each construct. The load, displacement, and rotation of each were analysed.

Results

• Following the dynamic non-destructive tests and the compression loading test until failure, the biomechanical properties of both the AO-3TLS and MUC-2TS treatments showed no statistical differences.

Conclusion

• This experiment concluded that the MUC-2TS treatment demonstrated equivalent biomechanical properties to the AO-3TLS treatment for PIP joint fusion, suggesting both techniques can be employed with similar expected outcomes regarding joint stability and post-operative healing.