CORTICAL BONE BLOOD-FLOW IN REAMED AND UNREAMED LOCKED INTRAMEDULLAR NAILING - A FRACTURED TIBIA MODEL IN SHEEP

We compared the effects of reamed versus unreamed locked intramedullar y nailing on cortical bone blood flow in a fractured sheep tibia model . A standardized spiral fracture was created by three-point bending wi th torsion, and each tibia was stabilized by insertion of a locked int ramedullary nail. Eleven animals were randomized into two groups: one that had reaming before nail insertion and one that did not. Blood flo w was measured in real time using laser Doppler flowmetry. Cortical bo ne perfusion measurements were made at three locations (proximal diaph ysis, fracture site, distal diaphysis) and at eight time intervals (pr efracture, postfracture, postreaming, postnail insertion, postlocking, and at 6-, and 12-week follow-up). All animals were killed at 12 week s postoperatively. After reamed nail insertion, cortical bone perfusio n was significantly decreased (p < 0.0009). After unreamed nail insert ion, perfusion was decreased less (p < 0.003). Insertion of locking sc rews did not affect blood flow. Cortical bone perfusion was greater in the unreamed group at completion of the procedure (p < 0.011), at 2-w eek follow-up (p < 0.006) and at 6-week follow-up (p < 0.027). The fin dings suggest that cortical revascularization had occurred by 6 weeks in the unreamed group but not until 12 weeks in the reamed group. The study demonstrates that cortical circulation is spared to a greater de gree by unreamed nailing. This may be advantageous in severe open tibi al fractures where blood supply is already significantly compromised.