A comparison of the Synthes 4.5-mm cannulated screw and the Synthes 4.5-mm standard cortex screw systems in equine bone.

The research article discusses a comparative study between the Synthes 4.5-mm cannulated screw system and the Synthes 4.5-mm standard cortex screw system, both in terms of its application and risk of failure in equine bone.

Research Methods

The researchers conducted several tests to gather detailed data on the performance and efficacy of both screw systems. The methods can be divided into three categories:

• Screw and equipment analysis: In this approach, the team compared maximum insertion torque of cannulated and standard cortex screw systems with the ultimate torsional strengths of the equipment. This showed how much torque the screws can withstand.
• Testing on Equine Cadaver Bones: These tests involved paired equine cadaver third metacarpal and third carpal bones. The aim was to capture data on the performance of both screw systems in real bone tissue scenarios.
• Strength tests: The researchers tested pullout strength and ultimate tensile load of cannulated and standard cortex screws, which reveals how much load the screws can bear before failure. These tests were performed with an axial-torsional, servohydraulic materials testing system and a hand-held torquometer.

Research Findings

The findings from the tests provided interesting insights comparing two screw systems:

• The maximum insertion torque of all cannulated instrumentation was less than the ultimate torsional strength.
• The maximum insertion torques of cannulated taps and screws were higher than for standard taps and screws in the third carpal bone of the horse.
• In terms of pullout strength, cannulated screws were less strong than standard cortex screws at all sites.
• Cannulated screws broke before bone failure in almost all the bone specimens tested.

Conclusions

The study concludes that the risk of a cannulated instrument or screw failure during insertion into bone is theoretically low. However, because of its relatively low pullout strength, the interfragmentary compression achievable with cannulated screws is likely to be less than that with standard cortex screws. Further, the cannulated screw’s relatively low pullout strength suggests it has a higher risk of failure during fracture repair compared to the standard cortex screw.