There is significant controversy related to the classification and assessment of the status of the medial longitudinal arch (MLA). Measurement techniques vary and issues of validity and reliability of these techniques are questioned. No universally agreed measure exists. This problem is compounded in childhood with growth and the presence of abnormal influences on development. This study utilised two measures, the vertical height of the navicular (NH) and the Arch Index ratio (AI), a footprint technique, to explore the development of the MLA in children between the ages of five years and six months and ten years and eleven months. Four specific studies considered various aspects of the MLA.
Study 1 investigated the issues of reliability and validity of the NH and AI measures as well as the influence of age, gender, limb preference, and body weight in 272 "normally" developing children. NH (intra-rater ICC =
.92; inter-rater ICC = .77) and AI (infra-rater ICC = .96; inter-rater ICC = .84) techniques are reliable measures of the MLA. The relationship between the measures of NH and AI was found to be low to moderate (Pearson's r = -0.46) and thus the NH, which is a direct bony measure of the MLA, would appear to be the more appropriate technique. NH may also prove to be a more universal measure for the paediatric population given that there is no significant difference in NH between gender; NH is not affected by body weight; and NH is more discriminating regarding differences relating to age (p <.0001).
The AI should not be discounted in assessment of the MLA as measures for children over eight years were consistent with findings of previous adult studies, however the AI measures were influenced by gender (p = .02).
The difference (p < .0001) between left and right feet for both measures NH (1.94 mm) and AI (.03) is considered
not clinically significant given the small differences obtained in the measurements. Use of a quartile distribution model for classification of the MLA height is recommended for both NH and AI measures.
Study 2 found that weight distribution on limbs in "typical" stance in normally developing children (n = 19) is asymmetrical (p < .0001; mean difference 1.88 kg) and that extremes of variation in weight distribution on limbs influence the measures of NH (p = .001) and AI (p < .0001).
Study 3 found that the weight distribution on limbs in "typical" stance in children with mild to moderate spastic cerebral palsy (n = 31) is asymmetrical (p < .0001; mean difference 2.5 kg). The study also explored the influence of topographical classification, skills/stance preference, presence of leg length inequality, gestational age at birth, and age of attainment of walking age on the NH and AI
measures. Children with hemiplegia did not statistically differ in the measures of NH and AI compared to children with diplegia/quadriplegia. Skills/stance preference of limbs, leg length inequality less than two centimetres, gestational age at birth, and age of attainment of functional walking did not influence the measures of NH and AI in children with mild to moderate spastic CP
Study 4 compared data related to NH and AI of normally developing children with data of children with mild to moderate spastic CP Children aged five years six months to ten years four months with mild to moderate spastic hemiplegia differ significantly in measures of NH (p = .0004) when compared to non-impaired children of the same age. Children with mild to moderate spastic diplegia/quadriplegia statistically differ in both NH (p = .0015) and AI (p = .002) measures when compared to non-impaired children.
This study indicates that children with CP (n = 31)
had NH measures (58%) and AI measures (61%) outside the normal range. The trend for a low arched posture was identified in children with diplegia/quadriplegia and a trend for a high arched posture was identified in the "involved" limb in subjects with hemiplegia.
These studies established baseline data and a profile of the MLA in children. Against this baseline future measurements of children can be compared to establish the normality of the arch or to determine the need for intervention and assessment of intervention outcome. This study has provided new quantitative insight into the status of the MLA in children with CP.