The Journal of Bone and Joint Surgery, Vol 75, Issue 8 1206-1213, Copyright © 1993 by Journal of Bone and Joint Surgery, Inc
Load-bearing capacity of corticocancellous bone grafts in the spine
MD Smith and DD Cody
Case Western Reserve University, Cleveland.
We investigated the relationship between the densities and areas of
commonly used autogenous tricortical bone grafts from the iliac crest and
the fibula and their mechanical load-bearing abilities. Intact
corticocancellous grafts, seven millimeters thick, were obtained during
elective spinal arthrodeses from fifty-six patients: from the anterior part
of the pelvis in twenty-four patients, the posterior part of the pelvis in
twenty-nine patients, and the fibula in three patients. The apparent
densities and cross-sectional areas of the cortical and cancellous bone
were measured with use of a specific computed-tomographic technique before
the specimens were mechanically tested to failure in uniaxial compression.
Specimens from the anterior superior iliac spine were able to bear
significantly higher axial loads (average, 3230 newtons; range, 430 to 8112
newtons) than were those from the posterior superior iliac spine (average,
1458 newtons; range, 350 to 4639 newtons) (p < 0.001). The cancellous
density was the most significant single factor in the prediction of the
load to failure of the grafts from the iliac crest (adjusted r2 = 0.58; p
< 0.0001). When all of the physical variables (the cancellous and
cortical densities and areas) were entered into a multiple-regression
model, the combination of the cortical and cancellous densities and the
cortical area was a good predictor (adjusted r2 = 0.68; p < 0.001) of
the load to failure. The fibular grafts were stronger than those from the
other two sites, but they had the least over-all cross-sectional area and
cancellous bone.(ABSTRACT TRUNCATED AT 250 WORDS)
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