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Vet Comp Orthop Traumatol 1995; 08(01): 25-36
DOI: 10.1055/s-0038-1632422
Original Research
Schattauer GmbH

Studies on the External Fixator Pin-Bone Interface: The Effect of Pin Design and Pin Cooling in an In Vivo Sheep Tibia Model

J. F. Zaruby
1   From the Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada
,
M. B. Hurtig
1   From the Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada
,
J. B. Finlay
2   The Orthopaedic Research Laboratory, University Hospital, University of Western Ontario, London, Ontario
,
A. E. Valliant
1   From the Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada
› Author Affiliations
Further Information

Publication History

Received for publication 19 August 1994

Publication Date:
09 February 2018 (online)

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Summary

The purpose of this study was to examine the effect of pin design and drill/pin cooling on the biological response of bone in the near (entry) and far (exit) cortices of mature intact sheep tibiae. Two pins with markedly different characteristics were used; the AO Schanz screw, a traditional pyramidal tipped design, and the fluted, tapered end Howmedica Apex pin. Our hypothesis was that cooling of hardware would reduce thermal necrosis of bone at the pin-bone interface (PBI). When the effect of pin design was controlled for, the cooled pins resulted in better pin bone interfaces at the near cortex but not the far cortex. It is possible that the drill bits and pins warmed significantly after traversing the more vascular bone marrow space, thus the cooling effect was lost before drilling the far cortex. Secondly, the Howmedica Apex pin resulted in more bone at the pin bone interface than the AO Schanz pin indicating that the former’s more advanced design follows the pilot hole and creates threads more accurately, resulting in a better pin-bone fit and less mechanical damage.

The purpose of this study was to examine the effects of pin design and drill/pin cooling on the remodelling response of cortical bone at the pin-bone interface in an in vivo sheep tibia model. No significant differences were found between pin designs or between pins that were implanted at 4° C and those that were inserted at 20° C. More bone was retained at the near cortex pin-bone interface (PBI) than the far cortex PBI when the pins were cooled, but the opposite was true when the pins were not cooled.

Keywords

External fixai or pin-bone interface - thermal damage - bone remodelling
 

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