Medical Imaging as a Bone Quality Determinant and Strength Indicator of the Femoral Neck - Biomedical Engineering Systems and Technologies - page 195

There exists skepticism concerning the ability of compression tests in predicting
the hip fracture risk, as fractures in the hip region are the effect of complex dynamic
force application, comprising of shear, tension and compression. Based on the forgo-
ing description of the model, it becomes evident that the conducted compression ex-
periments encapture the loading scenario in a realistic manner, as the compressive
strength of the femoral neck exerts a dominant impact on the structural integrity of the
femur. Furthermore, the compression tests were identically performed in all cases
while the only variation between samples was based on the bone mineral density.
A characteristic stress field developing on a femoral neck sample (T-score=-4.47,
σ y =109.448MPa and E=12.6GPa) is demonstrated in figure 6.

Fig. 6. Calculated stress field on a reverse engineered femoral neck sample

4 Discussion

Musculoskeletal models, accurately describing features of the human body are con-
stantly evolving, improving their ability to mimic structural characteristics, functions
or the mobility of the anatomy they are simulating. Medical imaging techniques allow
the customized development of such models based on the individual patient's charac-
teristics. Even though, this approach can provide highly accurate results, it should not
be considered the method of choice when assessing the fracture risk of the femoral
neck due to osteoporosis, mainly due to the reason that simpler methods (i.e. DXA)
can provide similar results as demonstrated in the previous paragraphs.
DXA scans in the hip region, are conventionally performed in the trochanter, the
Ward's triangle and the femoral neck (in an orthogonal area of 6 by 10mm). The
present paper, correlates the BMD obtained from such measurements, to the mechani-
cal strength characteristics of the examined area, as to provide surgeons with a DXA
based risk assessment, concerning fragility fractures.
There exists a consensus throughout literature, that bone density can be considered
as a strong independent predictor of failure strength [42]. By overlaying fatigue stress
value with the experimentally determined fracture strength of the examined speci-
mens, a correlation between T-score and fracture risk can be determined as demon-
strated in figure 7.