Biomedical Engineering Reference
In-Depth Information
Traditional indirect methods of analysing internal foot structure and function,
through measuring external foot parameters, has confounded this issue even further.
To address this concern, Riddiford-Harland et al. [
60
] designed an ultrasonographic
method of measuring plantar fat pad thickness and internal navicular height of young
children's feet (age = 3.8 ± 0.8 years) during both non-weight bearing and weight
bearing activities. This method was then used to investigate whether the flatter foot
structure characteristic of obese primary school-aged children (age = 8.3 ± 1.1 -
years; BMI = 25.2 ± 3.6 kg/m
2
) was due to increased medial midfoot plantar fat
pad thickness or structural lowering of the longitudinal arch [
61
]. Based on their
findings, the authors concluded that obese school-aged children had both signifi-
cantly fatter and flatter feet compared to their lean counterparts. That is, obese
school-aged children had a significantly thicker medial midfoot fat pad relative to
the leaner children during both non-weight-bearing (5.1 and 4.6 mm, respectively)
and weight-bearing (4.7 and 4.3 mm, respectively). The obese children also dis-
played a lowered medial longitudinal arch height, characterised by navicular height,
when compared to their leaner counterparts (23.5 and 24.5 mm, respectively).
Whether these values constitute clinical relevance has yet to be assessed.
In addition to fatter and flatter feet, obese school-aged children tend to have
larger feet and legs relative to non-obese children (Table
1
). For example,
Dowling et al. [
66
] and Riddiford-Harland et al. [
67
] found that relative to their
non-obese counterparts, obese school-aged children had significantly greater heel
breadth, ball of foot breadth, first to third toe breadth, as well as greater circum-
ferences of the calf, ankle, heel-ankle, instep and ball of foot. The obese children
also tended to have a greater dorsal arch height, ball of foot height, 1st toe height,
maximum toe height, outside ball of foot height and calf height (Fig.
3
), but not
plantar arch height, relative to their non-obese counterparts. The length of various
foot regions also differed between the obese compared to non-obese children and
included increased length of the ball of foot and instep. It is still unclear, however,
if these broader, higher and thicker structural features of the foot in obese children
impact upon children's footwear choices [
67
] and what influence these structural
features might have on the functional characteristics of the lower limb. Some
studies have suggested that, with a larger base of support, overweight and obese
children have better static balance than leaner children [
69
]. Other studies, how-
ever, have suggested that stability is reduced in overweight and obese children [
70
]
and that these children are at greater risk of fractures to the foot, ankle, shank and
knee due to increased risk of falling compared to normal-weight and underweight
children [
71
].
4.2.2 Effects of Obesity in Children on Gait and Plantar Pressures
One of the fundamental activities of daily living likely to be affected by changes to
foot structure is walking. Consistent with this notion is that gait characteristics of
obese children appear to differ from their non-obese counterparts. For example,
obese children (age unknown; n = 4, BMI = 20.6 ± 1.6 kg/m
2
) were found to
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