Effect of Fixation Pin Insertion on the Bone‐Pin Interface

Abstract

Smooth and partially threaded 3.12 mm (W inch) trochar-tipped Steinmann pins were inserted transversely through both diaphyseal cortices of eight mature canine tibias using five methods. Angular velocity (revolutions per minute) during insertion and temperature elevation due to friction during penetration of the second cortex were recorded. The force required for extraction of the pins from the bone and the histologic appearance of the bone-pin interface were determined for one-half of the pins 2 days after insertion and for one-half of the pins 56 days after insertion. The increase in temperature was similar for all methods of insertion except high speed power, which was significantly greater (p < 0.05). The force required for axial pin extraction was similar for pins inserted by hand chuck, predrllled, and low speed power methods after both 2 and 56 days. Pins inserted by high speed power and hand drill required force similar to the others for extraction after 2 days but significantly less force (p < 0.05) for extraction after 56 days. The partially threaded pins required significantly greater force (p < 0.01) extraction after both 2 and 56 days. Hlstologic examination revealed increased mechanical bone damage surrounding hand chuck inserted pins, increased bone necrosis surrounding high speed power inserted pins, and increased inflammatory changes surrounding hand drill inserted pins.

Postoperative complications associated with external skeletal fixators in cats

“…Inappropriate technique can lead to excessive heat generation resulting in thermal osteonecrosis and premature pin loosening. 21,37 Animal studies have shown that bone undergoes significant resorption when heated to 50°C for 60 seconds or longer, 38 and pin insertion with a high speed drilling results in significantly higher bone temperatures. It is therefore recommended that pins are placed at a slow speed (150rpm or less), as high speed placement reduces long term pin extraction forces when compared with low speed placement.…”

“…It is therefore recommended that pins are placed at a slow speed (150rpm or less), as high speed placement reduces long term pin extraction forces when compared with low speed placement. 2,21,36,37 A further technique factor is the forward drilling force, which can affect maximal cortical bone temperatures when drilling. 39 Again, this type of information was not available in a retrospective study.…”

Management of femoral fractures in dogs with unilateral semicircular external skeletal fixator-intramedullary pin tie-in configurations

“…Although IM pin resists bending equally well in all directions due to the proximity of the neutral axis, resistance to disruptive forces of shearing, torsion and compression is inadequate if used alone (5,11,18). When used together, ESF and IM pin are more resistant against these forces.…”

Treatment of Orthopaedic Problems with Manuflex® Disposable External Fixator in 15 Dogs and 7 Cats

“…This was preferred, because previous studies show that high speed drills (or with low speed and excessive pressure) may cause thermal necrosis in the bones and because of the holes excessive enlargement for the pins resulting in premature loosening [18] . Soft tissue swelling is frequently seen between connecting bar and skin, postoperatively.…”