Determining the degree of cortical bone asymmetry in bilateral, nonpathological, human femur pairs

Abstract

When testing the effects of a femoral component on cortical bone following total hip arthroplasty, the patient's implanted femur is often compared with his/her contralateral nonimplanted femur, with differences attributed to the femoral component. However, if normal anatomical differences exist between bilateral femurs, they need to be quantified in order to validate whether the differences between implanted and nonimplanted bilateral femurs are due to the implant or possibility due to intrinsic differences before implantation. This study quantified the geometric properties of cortical bone shape between seven pairs of bilateral, cadaveric, human femurs. The null hypothesis tested stated that the bilateral femurs would not be significantly different in cortical bone geometry. Digitized images of cortical bone cross-sections taken at percent biomechanical lengths (levels 1-8) were used to calculate bone geometry measurements. The paired t-test showed that the only significant difference was in the location of principal axes at the most proximal location, level 1 (p = 0.015). All other measurements and levels were not significant with percent differences less than 6.6%. In conclusion, the data supports attributing cortical bone shape differences between implanted and contralateral nonimplanted femurs in levels 2-8 to the presence of the implant when the significant differences are greater than 6.6%.

Are the Left and Right Proximal Femurs Symmetric?

“…The investigators who have examined symmetry have studied bone properties and cortex thickness [28,32,36,40], with few studying dimensions [3,28]. The clinical impact of asymmetry is subtle, as the assumption of symmetry is pervasive.…”

“…Studies of ethnic variations of morphologic features of the femur showed differences in femoral head diameters, femoral offset, and shaft diameters between European and Asian populations [18,43]. Research on bilateral femoral asymmetry has focused on properties such as bone mineral density, mechanical strength, cortex thickness, torsion angles, limb lengths, or the distal femur [8,26,28,32,36,40]. The studies that have researched asymmetry between Each author certifies that he or she has no commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article.…”

Influence of Acetabular and Femoral Version on Fractures of the Femoral Neck

“…Previous studies have suggested the contralateral limb sustains a similar fracture in 80% of patients, supporting the idea that the geometry on the opposite limb is likely to be similar with respect to femoral version, acetabular version and femoral neck length. There is cadaveric evidence that bilateral femurs do not have different cortical bone geometry [25]. It may be possible to obtain CT scans of patients who have had scans for other reasons and then experienced a hip fracture.…”

“…There is cadaveric evidence that bilateral femurs are symmetric and do not have different cortical bone geometry [25]. For the purpose of this study, we therefore assumed the anatomic alignment of the contralateral hip was the same as the fractured hip.…”

Effectiveness of resonance frequency in predicting orthopedic implant strength and stability in an in vitro osseointegration model

“…The completed fixture was 45 mm in height by 30 mm in width with a 4 mm hole centrally located for implant attachment. An ABS model was selected as the testing material because it excludes the inherent variability of human cadaveric bone [62][63][64]. In addition to variability between bone specimens, dehydrated bone will exhibit a higher modulus of elasticity caused by the diffusion of water into vacant spaces and stiffening of collagen fibers [65].…”