Equine ulnar fracture repair with locking compression plates can be associated with inadvertent penetration of the lateral cortex of the radius.

This research study investigates the risks associated with using locking head screws in the repair of equine ulnar fractures. The research shows that this approach can lead to unintentional damage to the lateral cortex of the radius.

Experimental Setup

• The researchers carried out a controlled laboratory study using cadaveric equine forelimbs. They performed a specific surgical technique, transverse ulnar osteotomy, and then used a locking compression plate for osteosynthesis, a procedure to facilitate healing by bringing fractured bone ends together.
• The locking compression plate was attached to the caudal aspect, or rearward-facing side, of each ulna, a bone in the equine forelimb. These plates were of a narrow 10-13 hole 4.5/5.0 variety.
• The researchers then inserted screws into the distal holes of the plate. In one group of limbs (group 1), they used 4.5mm cortex screws. In a contralateral group (group 2), they used 5.0mm Locking Head Screws (LHS).
• Cortex screws were inserted at an angle deemed appropriate by the surgeon while LHS were inserted perpendicular to the plate.

Findings

• The team used radiography and CT imaging to assess the positioning of the implant, and then they dissected the limbs to physically inspect for any injuries to the lateral cortex of the radius – the bone in the forelimb of the horse located opposite to the ulna.
• In the first group, where the cortex screws were used, no injuries occurred to the lateral cortex of the radius. However, in the second group, where LHS were used, the researchers noted significant damage. In four limbs, and in six out of the twenty-four LHS used, they observed injuries to the lateral cortex of the radius due to the penetration by LHS.
• The angle at which the cortex screws were inserted was recorded to be 17.6° from the sagittal plane in a rear-to-front (cauodlateral-craniomedial) direction.

Conclusions

• From this study, the authors concluded that the use of locking head screws in the distal part of a locking compression plate applied to the rear aspect of the ulna is associated with a risk of injuring the lateral cortex of the radius.
• Thus, given these findings, appropriate measures need to be taken when carrying out such procedures to ensure the safety of the animal’s radius and overall long-term healing and well-being.