HOLDING POWER OF DIFFERENT PIN DESIGNS AND PIN INSERTION METHODS IN AVIAN CORTICAL BONE

Objective-To measure pullout strength of four pin types in avian humer i and tibiotarsi bones and to compare slow-speed power and hand insert ion methods. Study Design-Axial pin extraction was measured in vitro i n avian bones. Animal Population-Four cadaver red-tailed hawks and 12 live red-tailed hawks. Methods-The pullout strength of four fixator pi n designs was measured: smooth, negative profile threaded pins engagin g one or two cortices and positive profile threaded pins. Part 1: Pins were placed in humeri and tibiotarsi after soft tissue removal. Part 2: Pins were placed in tibiotarsi in anesthetized hawks using slow-spe ed power or hand insertion. Results-All threaded pins, regardless of p in design, had greater pullout strength than smooth pins in all parts of the study (P < .0001). The cortices of tibiotarsi were thicker than the cortices of humeri (P <.0001). There were few differences in pin pullout strengths between threaded pin types within or between bone gr oups. There were no differences between the pullout strength of pins p laced by slow-speed power or by hand. Conclusions-There is little adva ntage of one threaded pin type over another in avian humeri and tibiot arsi using currently available pin designs. There were few differences in pin pullout strengths between humeri and tibiotarsi bones. It is p ossible that the ease of hand insertion in thin cortices minimizes the potential for wobbling and therefore minimizes the difference between slow-speed drill and hand insertion methods. Clinical Relevance-Threa ded pins have superior bone holding strength in avian cortices and may be beneficial for use with external fixation devices in birds. (C)Cop yright 1998 by The American College of Veterinary Surgeons.