T. Nakamura et al., Cortical revascularization after reamed and unreamed intramedullary nailing in the rabbit femur: A microangiographic histometric analysis, J TRAUMA, 47(4), 1999, pp. 744-751
Background: Intramedullary nailing leads to a reduction in cortical bone bl
ood flow, The relative effect of reamed versus unreamed nailing on the degr
ee of avascularity and on revascularization of the cortex remains controver
sial, We compared the effects of reamed versus unreamed intramedullary nail
ing on cortical revascularization and the time course for its recovery in t
he unfractured rabbit femur.
Methods: A total of 56 New Zealand white rabbits were used as experimental
animals. Reamed nailings with Kirschner wire (diameter, 3 mm) were performe
d in the right femora (group R, n = 49), and unreamed nailings with Kirschn
er wire (diameter, 2 mm) were performed in the left femora (group UR, n = 4
9) of the same animals after a standard surgical procedure. Microangiograph
y that used Indian ink was performed for each killed animal at one of seven
postoperative time periods: 2 hours, 3 days, and 1, 2, 3, 4, and 5 weeks a
fter surgery. The right femora and the left femora of seven rabbits were us
ed as the postoperative day 0 controls of group R and those of group UR, re
spectively. We evaluated the vascularization ratio (VR) in cross-sections a
ccording to the following formula: VR = the number of enhanced vessels with
Indian ink/total cortical vessels, Each cross-section was divided into an
inner and outer half, which were in turn divided into quarters, so that the
entire cross-sectional are is represented by eight regions. The VR was cal
culated for each regions and then comparison was made between group R and g
roup UR at various time periods and areas,
Results: No statistically significant differences were observed in VR at an
y time period between group R and group UR in total cortical area and total
periosteal side. However, on the total medullary side, the VR of group UR
was significantly higher than that of group R at postoperative day 3 (p = 0
.04). Statistically significant differences were observed between the VR on
the periosteal side and that on the medullary side in both groups at all t
ime periods aside from the 5-week period (p < 0.05), Revascularization of t
he cortex occurred 4 weeks after intramedullary nailing in both group R and
group UR,
Conclusion: The periosteal circulation was maintained better than the medul
lary circulation, irrespective of whether the canal was reamed or not, The
present study failed to detect any statistically significant differences in
cortical revascularization between reamed nailing and unreamed nailing. Th
us, we concluded that reamed and unreamed nailing are not differentially ad
vantageous in the unfractured rabbit femur, in terms of impairment of corti
cal blood supply.