Finite Element Analysis of the Wrist Joint Affected by Rheumatoid Arthritis - Computational Biomechanics of the Wrist Joint - page 52

Fig. 5.11 Equivalent von Mises (EQV) stress plot for the healthy and RA model

models was e = 0.02 and 0.06 %, respectively. The cancellous bone for the healthy
and RA model have relatively higher strain value, e = 0.17 and 0.15 %, respec-
tively. All values from our study were found to be below the failure criteria as
mentioned by the previous researchers.

5.3.2 The Biomechanical Effect of Symptoms
and Pathophysiological Characteristics

The worsened mechanical properties of the associated tissues and physiological
functions of the wrist affected by RA [ 2 ] were simulated. Discussion on the effect
of the pathophysiology will be presented separately. As one of the characteristics,
the osteoporotic RA bones analysed here were found to have 20 % lower stress in
comparison with the healthy bones (Fig. 5.12 ). This condition was significantly
mimicking the condition where the rheumatic patients tend to underutilise their
hands. As the condition progresses, there is high tendency to be affected by bone
atrophy as a result of slow generation of the bone cells [ 34 ].
Soft tissues are destructed at the early stage of the RA mechanism [ 7 ]. This
study has significantly evident the effect of this situation towards biomechanical
behaviour of the joint. The absence of the articular cartilage resulted in unphys-
iological changes to the contact pressures within bones and compressive stress
within the cartilages layers, which were addressed in this study and further sup-
ported by work done by Carrigan et al. [ 19 ]. Ten times higher contact pressure in