16. THE EFFECT OF INTRAMEDULLARY REAMING ON A DIAPHYSEAL BONE DEFECT OF THE TIBIA

Abstract

Purpose: The purpose of this study was to relate the extent of reaming to bone formation occurring around a critical sized defect in the tibia.

Method: Eleven canines were allocated into 2 groups: empty (N=5) or iliac crest autograft (N=6). All tibiae were reamed to 7.0 mm and fixed with a 6.5 mm statically locked intramedullary nail after creation of an 8.0 mm diaphyseal defect. The extent of reaming of the canal was dependent on the cross-sectional area of the tibia as all tibiae were reamed to 7.0 mm. Fluorescent markers were given at different times: calcein green (6 weeks), xylenol orange (9 weeks), and tetracycline (11 and 14 weeks). Animals were sacrificed at 15 weeks and perfused with a barium compound. Radiography, Micro CT, brightfield microscopy and fluorescent microscopy were used for analysis.

Results: Bone and vasculature volume within the defect were reported as a percentage of the total volume of the defect. Linear regression analysis of percent bone volume (dependent variable) and canal area (independent variable) provided a Pearson correlation coefficient of 0.925 (p=0.025) for the empty group and 0.244 (p=0.641) for the autograft group. Linear regression analysis of percent vasculature volume (dependent variable) and canal area (independent variable) provided a Pearson correlation coefficient of 0.784 (p=0.117) for the empty group and −0.146 (p=0.783) for the autograft group. Bone formation at osteotomy sites was defined as the distance from the original osteotomy site to the tip of newly formed bone. Linear regression analysis of bone formation at the osteotomy sites (dependent variable) and canal area (independent variable) provided a Pearson correlation coefficient of 0.132 (p=0.832) for the empty group and −0.937 (p=0.006) for the autograft group. Bone formation rates were reported as the distance between the fluorescent labels. Bone formation rate was less within the endosteum, cortex and periosteum with extensive reaming in empty samples.

Conclusion: Our results suggest that the acute management of tibia fractures with bone defects should involve limited reaming. This does not apply when the defect is autografted. Limited reaming may be defined by the cross-sectional area of the tibia in ratio to that of the reamer.