Dept. of Orthopaedics, University of Utah School of Medicine
Friday All day, Plaza Level
Gray levels (GLs) in circularly polarized light (CPL) images reflect predominant collagen fiber orientation (CFO) (Skedros et al., 2011 J. Anatomy). CFO-Het, measured as the full-width at half-maximum (FWHM) of a GL/CFO profile, has been shown to corroborate the bending load history in the chimpanzee proximal femoral shaft (Keenan et al., 2011 AAPA). Based on this previous chimpanzee study, greater CFO-Het in compression “cortices” was also expected in the human femur. Twenty-four sections from 12 adult human proximal femoral shafts were embedded in methacrylate, ultramilled, and imaged in CPL. FWHM was measured from CFO profiles (larger FWHM = greater CFO-Het). Statistical analysis was based on the: 1) left peak (LP), 2) right peak (RP), and 3) average of both peaks (AvgP) of the CFO profile of each image. Results show highest CFO-Het in the medial “compression” cortex when considering the LP (p<0.05), but is unexpectedly highest in the lateral “tension” cortex when considering the RP and AvgP (p<0.05). Although CFO-Het correlates moderately with CFO for the RP and LP (RP: r=0.5, p<0.001, LP: r= -0.6, p<0.001), there is no correlation with AvgP data (r= -0.1). While CFO-Het clearly corroborates CFO-based load history data in chimpanzee femora (greater CFO-Het in “compression” cortices), CFO-Het does not clearly reflect this load history in human proximal femora. This may reflect difficulties in quantifying CFO-Het based on the presence of two CFO peaks in human femora (chimpanzees = one peak). Consequently, CFO-Het does not appear useful for predicting a history of bending in these bones.