Effects of degrees of reaming on healing of segmental fractures in rats.

OBJECTIVE: To assess the effects of graded intramedullary reaming and nailing on the healing pattern of segmental diaphyseal fractures using male Wistar rats. STUDY
DESIGN: In male Wistar rats we produced two standardized, partial osteotomies with an eight-millimeter intermediary fragment in the femoral diaphysis. The osteotomies were subsequently manually broken. In Group A, intramedullary reaming was performed to 1.6 millimeters, and the fracture was stabilized with a 1.6-millimeter steel pin. In Group B, the femoral canal was reamed to 2.0 millimeters, and a hollow steel tube of 2.0 millimeters was installed. The rats were allowed free movement. After four, eight, and twelve weeks, eight rats in each group were sacrificed and callus formation, biomechanical properties, and bone blood flow were evaluated.
RESULTS: The callus area was relatively constant with time in Group B, whereas a reduction was observed in Group A at twelve weeks. The biomechanical properties increased throughout the experimental period in both groups, and no significant differences between the groups were detected in bending moment, bending rigidity, or fracture energy. Total bone blood flow was substantially increased at four weeks in both groups and decreased throughout the experimental period. In addition, blood flow of the segmental fractured area was substantially increased after four weeks and decreased gradually thereafter. The increases in blood flow tended to be largest in the moderately reamed group.
CONCLUSION: This study indicates that the degree of reaming does not significantly affect the healing pattern measured as restoration of mechanical characteristics.