HOLDING POWER OF THREADED EXTERNAL SKELETAL FIXATION PINS IN THE NEARAND FAR CORTICES OF CADAVERIC CANINE TIBIAE

We compared the pin-bone interfaces at the near and far cortical penet ration sites of positive-profile end-threaded external fixation pins i n cadaveric canine tibiae. The holding power of the pins in each corti cal surface was independently measured in 21 pin-bone sections. Scanni ng electron microscopy (SEM) was used to compare subjectively the micr ostructural appearance of the pin-bone interfaces at the near and far cortical penetration sites in eight pin-bone sections. The far cortica l penetration site provided greater holding power than did the near co rtical site. SEM evaluation suggested more bony microfractures and deb ris with less pin-bone interlock in the near cortical penetration site s than in the corresponding far cortical penetration sites. This study showed that after low-speed power insertion of positive-profile end-t hreaded pins in canine cadaveric tibiae, the near cortical penetration site contributes approximately 25% less to the overall holding power of the pin than does the far cortical penetration site. (C) Copyright 1994 by The American College of Veterinary Surgeons