Insertional characteristics of three types of transfixation pin taps in third metacarpal bones from equine cadavers.

The study investigates how three different tools for inserting transfixation pins into horse metacarpal bones affect heat generation and bone damage. The research finds that a revised tapered tap causes less heat and microdamage than the other two tools. Hand tapping is recommended over power tapping due to the less damage, despite the higher temperature.

Methodology

• The researchers utilized 18 pairs (36 total) of third metacarpal bones taken from euthanized horses that had no known metacarpal disease.
• In each bone, an investigator drilled three holes, each meant for a specific type of 6.3-mm transfixation pin: a cylindrical transfixation pin, a tapered pin using a prototype tapered tap, and a tapered pin using a revised tapered tap.
• One bone from each pair was tapped manually while the other was drilled using an electric drill.
• The heat generated by the drill bits, reamers, and taps were measured and compared among the tap groups and tapping methods (hand tapping vs power tapping).
• The researchers assessed the macrodamage (in all bone pairs) and microdamage (in 6 bone pairs).

Results

• The revised tapered tap resulted in less heat generation and less total thread microdamage, compared to the prototype tapered and cylindrical taps.
• Power tapping created less bone damage but higher temperatures than hand tapping for all bone groups.

Conclusions

• The revised tap design for tapered pin insertion was superior to the prototype tap design and resulted in similar or less bone damage as compared to cylindrical pin insertion in equine third metacarpal bone specimens.
• The study recommends careful hand tapping for tapered pin insertion rather than power tapping, as the latter generated more heat.
• It is anticipated that the revised tapered tap would outperform the cylindrical pin tap in terms of thermal and mechanical microdamage and, therefore, should be used for the insertion of tapered transfixation pins.