PSI - Issue 42

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N.S. Hennicke et al. / Procedia Structural Integrity 42 (2022) 404–411 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 1. Schematic illustration of model construction

2.1 Implementation of Osteoporosis and Aging The world health organisation defines osteoporosis by the measured bone mineral density (BMD) of a patient. For the diagnosis the BMD is compared to the average bone density of a young healthy person. The resulting standard deviation delivers the so called T-score, which is a measure for the severity level of the disease (see Table 1) (Leslie and Morin, 2020).

Table 1. Diagnosis and severity levels of osteoporosis (Compston et al., 2019)

Diagnosis

Normal

Osteopenia

Osteoporosis

T-score

Higher than -1

-1 to -2.5

Lower than -2.5

To assess the fracture risk due to advanced age on the other hand, the so called Z-score is determined by comparing the BMD of the patient to the average of a healthy person in the same age group. The BMD values for the modelled femurs were determined from the QCT scans from which the models were created and used to determine the original T-score and Z-score of the two donors of femur 1L and 3L (see Table 2). Osteoporosis and aging cause a change in the amount of bone density. However, while the overall bone density is reduced the load distribution and therefore also the density distribution within the bone remain unchanged (Homminga et al., 2001). Therefore, the density was evenly reduced within the whole femur in the heterogeneous models.

Table 2. Data of the original femurs

Femur

Age [years]

BMD [g/cm²] Z-score

T-score

1L 3L

81 77

0.758 0.619

-0.553

-1.97 -2.93

-1.97