EVALUATION OF CORTICAL BONE DAMAGE AND AXIAL HOLDING POWER OF NONTHREADED AND ENHANCED THREADED PINS PLACED WITH AND WITHOUT DRILLING OF A PILOT HOLE IN FEMURS FROM CANINE CADAVERS

Objective-To evaluate the in vitro axial extraction forces necessary t o remove pins and to evaluate mechanical trauma resulting from pin ins ertion, using various types of pins and insertion techniques. Design-P rospective, controlled study. Subjects-Femurs of cadavers of dogs. Pro cedure-Pins were inserted as follows, 1 non-threaded pin without drill ing of a pilot hole, 1 enhanced threaded pin with drilling of a pilot hole, and 1 enhanced threaded pin without drilling of a pilot hole. Af ter pin insertion, mechanical damage and proper pin insertion was dete rmined by means of radiography. Axial extraction forces were determine d for all pins, using a universal testing machine, Mechanical damage w as evaluated in 12 additional femurs. After pin insertion, all pins we re removed from the bane by use of a low-speed power drill, Samples we re sectioned, processed, and evaluated by use of dissecting and scanni ng electron microscopy. Results-Using radiography,a significant differ ence was detected in the number of periosteal trans-cortex fractures b etween the enhanced threaded and nonthreaded pins, Axial extraction fo rce was not significantly different between the enhanced threaded pins , regardless of insertion technique; however, the axial extraction for ce was significantly greater for enhanced threaded pins, compared with that for nonthreaded pins. Microfractures only were detected on the p eriosteum of the trans-cortex of enhanced threaded pins by use of scan ning electron microscopy, Clinical implications-We cannot recommend a particular insertion technique to decrease mechanical trauma to the bo ne and to increase axial extraction force needed for removal of enhanc ed threaded pins from the femur of dogs.