Biomedical Engineering Reference
In-Depth Information
4.4.1 Effects of Obesity in Older Adults on Foot Structure
Anthropometric data on the feet of older adults is not easily found. One of the few
studies that have reported foot anthropometrics for the elderly found that although
foot length matched well with the size of commercially-available footwear, more
than two-thirds of the measured feet were considerably wider than the footwear
[
124
]. In a comprehensive study involving three-dimensional scanning of the feet
of 158 men and 154 women aged between 60 and 90 years, the older men had
significantly larger absolute foot dimensions than the older women for all 17
measured foot dimensions, with the exception of first toe and heel bone angles
[
125
]. When normalised to foot length, however, older men and women's feet
differ significantly, mainly in the toe region where men have greater first and fifth
toe heights and a greater fifth toe angle, and women have a greater first toe angle.
Similar to the feet of children, adolescents and younger adults as described above,
the obese older foot is structurally characterised by larger and broader foot
dimensions relative to their leaner counterparts (Mickle and Steele, unpublished;
Table
2
). The larger feet of older obese individuals may result in difficulty when
donning regular shoes. Alternatively, older obese individuals might be forced to
squeeze their feet into shoes that are too small or wear unstructured, 'sloppy'
footwear, which is not safe for older people because of the heightened risk of
falling. Like their younger counterparts, older obese individuals have also been
shown to have flatter feet relative to non-obese older individuals [
126
-
128
] (Mickle
and Steele, unpublished). In addition to reasons described for adults, the higher
prevalence of flat feet is of concern given planus foot morphology during relaxed
standing (flat feet) has been associated with frequent knee pain and medial tibio-
femoral cartilage damage in a cohort of 1,903 older individuals (56 % women;
age = 65.0 ± 9 years; BMI = 28.7 ± 5.7 kg/m
2
;[
129
] ). In this cohort, feet with
the most planus morphology had 1.3 times (95 % CI 1.1-1.6) the odds of reporting
frequent ipsilateral knee pain, and 1.4 times (95 % CI 1.1-1.8) the odds of medial
tibiofemoral cartilage damage compared to all other foot types [
129
]. Whether the
flatter feet in older individuals are associated with changes to the osseous structures
or the plantar fat pad has not been definitively established. Research from
our laboratory has found that older obese participants (n = 103; age = 71.4 ±
6.8 years; BMI [ 33.8 ± 4.1 kg/m
2
) have greater soft tissue thickness across the
plantar surface of their feet compared to the overweight (n = 128;
age = 71.4 ± 6.2 years, BMI = 27.5 ± 1.4 kg/m
2
) group who, in turn, had thicker
soft tissue thickness under the heel and lateral forefoot than the non-overweight
older adults (n = 81; age = 72.2 ± 7.1 years; BMI = 22.8 ± 1.6 kg/m
2
). In
contrast to these results, Ozdemi et al. [
115
] reported that obese adults with heel
pain had significantly less tissue thickness at the heel compared to average weight
adults with heel pain. However, the latter authors used a BMI of 27 as the obesity
classification cut-point, instead of a BMI of 30, which is the cut-point for adults
recommended by the World Health Organisation.
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