Effect of Cortical Screw Diameter on Reduction and Stabilization of Type III Distal Phalanx Fractures: An Equine Cadaveric Study.

This research compares the efficacy of using 4.5mm and 5.5mm cortical screws in the reduction and stabilization of Type III fractures of the distal phalanx in horses, showing the larger 5.5mm screws to be more effective.

Study Methodology

• The researchers carried out an experimental study on 24 hooves from 12 adult horses. For each pair, one hoof was left intact to serve as a control.
• Known as type III fractures, they created fractures in pairs of distal phalanges after distal interphalangeal joint disarticulation.
• These fractures were reduced using either 4.5mm or 5.5mm cortical screws placed in a specific configuration known as lag fashion.
• The changes were traced using radiographs before and after, in order to determine the level of reduction achieved by each screw placement.

Data Measurement and Assessment

• The study measured the fracture gaps, i.e. the space between the broken bone fragments, before and after the screw placement, and compared these measures using paired t-tests.
• They further tested the effect of increased loading on the fracture gaps in phalanges reduced with either size of cortical screws. The loading weights used ranged from 0 to 1335 kg.
• The impact of these loads was also monitored from fluoroscopic images and analyzed using a statistical method called 2-way ANOVA.
• All results were considered significant at a probability cut-off point of P<0.05.

Results and Conclusions

• The researchers successfully created Type III distal phalanx fractures on the test hooves.
• The larger 5.5mm cortical screws, outperformed the smaller 4.5mm screws in reducing the fracture gaps.
• Additionally, the 5.5mm screws were observed to be more effective at limiting the expansion of fracture gaps located 3 cm distal to the articular surface (the joint surface).
• The study found that compressive loading closed the fracture gaps at the joint surface in both the control group and the ones treated with either size of screws. This attribute is beneficial, as it aids in the fracture healing process.
• Conclusively, the larger 5.5mm screws were determined to be more effective at reducing type III distal phalanx fractures and restricting distal fracture gap expansion under load.