Biomechanical comparison of the Herbert and AO cortical bone screws for compression of an equine third carpal bone dorsal plane slab osteotomy.

The research article investigates the feasibility of applying 4.5-mm Herbert cannulated bone screws using fluoroscopic direction and compares the mechanical strength of these screws to 4.5-mm AO cortical bone screws, in fixation of a type of horse carpal bone surgery.

Objective of the Study

In the study, the authors aimed to ascertain the practicality of inserting 4.5-mm Herbert cannulated bone screws using fluoroscopic guidance. They also sought to make a mechanical comparison of the bone screws with 4.5-mm AO cortical bone screws in the context of repairing fractures in a specific region (dorsal plane slab) of equine cadaveric third carpal bones.

Methodology

• Eight equine cadavers were enrolled in the study.
• Dual-energy X-ray absorptiometry was used to confirm equivalent bone mineral composition and density of corresponding third carpal bones.
• A standard 10-mm third carpal bone slab operation was performed using either Herbert screw or AO screw tools under fluoroscopic guidance.
• The specimens were loaded in shear until they broke, utilizing a materials testing apparatus.

Results

• Both Herbert and AO screw tools facilitated accurate reconstruction of the operation site, although difficulties were encountered while setting the Herbert screws’ proximal self-tapping threads.
• There were no significant disparities in terms of maximal load to failure, stiffness, or the mode of the failure of structures created with both types of screws.

Conclusions and Implications

• The findings suggest that using 4.5-mm Herbert screws for repairing the third carpal bone radial facet, dorsal plane lab fractures may yield mechanically comparable results to a repair using 4.5-mm AO screws.
• The density of the equine’s dorsal third carpal bone may hinder the placement of Herbert screw’s proximal self-tapping threads without potentially applying excessive torque to the screw itself.
• The results imply that accurate reconstruction and stabilization are crucial for the horse’s return to athletic function.