Foot–Ankle–Knee Model for Foot Orthosis - Computational Biomechanics of the Musculoskeletal System - page 147

of the K-Scan sensor and the buckling phenomenon of the sensor edge during testing. The differ-
ence in pattern may also be attributed to the inconformity in knee geometries between the modeled
subject and the cadaveric specimen. The peak plantar pressure patterns were comparable between
FE predictions and F-Scan results when using a flat insole. The F-Scan measurement of peak plantar
pressure during mid-stance was 0.11 MPa (Figure 12.3c). The FE-predicted peak plantar pressure
was 0.15 MPa (Figure 12.3d). The contact area predicted by the FE model was approximately 68 cm 2
for a 0-degree wedge, compared with 70 cm 2 from F-Scan measurements. The difference between
the plantar pressure data obtained from the F-Scan measurement and FE prediction was mainly due
to differences in resolution.
The validated FE model was used to predict the strain, pressure, and shear stress in the tibio-
femoral joint during mid-stance. The instant when the lowest GRF value appears was chosen as
the cut-off point for mid-stance input data processing, at approximately 45% to 55% of the stance
phase, close to heel rise. Figure 12.4 illustrates the minimum (compressive) principal strain distri-
bution patterns in the femoral cartilage and menisci with 0-, 5-, and 10-degree laterally wedged
orthoses during mid-stance. The peak minimum principal strain on the femoral cartilage and
menisci among the three wedges were all predicted to occur in the medial side. The peak mini-
mum principal strain at the medial femoral cartilage region decreased by approximately 1.3% using
a 5-degree orthosis, and 10.8% using a 10-degree orthosis, compared with the 0-degree wedge
model. Meanwhile, in comparison with the 0-degree wedge, the peak minimum principal strain at
the medial meniscus decreased by approximately 7.7% using a 5-degree orthosis, and 25% using a
10-degree orthosis.

- 0.000
- 0.012
- 0.024
- 0.036
- 0.048
- 0.060
- 0.072
- 0.084
- 0.096
- 0.108
- 0.120
- 0.132
- 0.145
- 0.231

- 0.001

- 0.007
- 0.014
- 0.020
- 0.027
- 0.033
- 0.040
- 0.046
- 0.052
- 0.059
- 0.065
- 0.072
- 0.078
- 0.104

Peak 23.1%

Peak 10.4%

(a) (b)

- 0.001
- 0.007
- 0.014
- 0.020
- 0.027
- 0.033
- 0.040
- 0.046
- 0.052
- 0.059
- 0.065
- 0.072
- 0.078
- 0.096

- 0.000
- 0.012
- 0.024
- 0.036
- 0.048
- 0.060
- 0.072
- 0.084
- 0.096
- 0.108
- 0.120
- 0.132
- 0.145
- 0.228

Peak 22.8%

Peak 9.6%

(c) (d)

- 0.000
- 0.012
- 0.024
- 0.036
- 0.048
- 0.060
- 0.072
- 0.084
- 0.096
- 0.108
- 0.120
- 0.132
- 0.145
- 0.206

- 0.001
- 0.007
- 0.014
- 0.020
- 0.027
- 0.033
- 0.039
- 0.046
- 0.052
- 0.059
- 0.065
- 0.072
- 0.078

Peak 20.6%

Peak 7.8%

(e) (f)

FIgure 12.4 (See color insert.) Minimum (compressive) principal strain in the femur cartilage with (a) 0-,
(c) 5-, and (e) 10-degree laterally wedged orthosis and minimum principal strain in the meniscus with (b) 0-,
(d) 5-, and (f) 10-degree laterally wedged orthosis.