Gross motor function in children with Achondroplasia and the effect of lower limb musculoskeletal impairments

Abstract

Background and Objectives: Achondroplasia is the most common form of short-limbed dwarfism. Children with achondroplasia experience significant gross motor delays, proposed to be related to several lower limb impairments, summarised by the acronym 'TRAVELS': (i) Trident pelvis, (ii) Rhizomelic shortening of femur, (iii) Acetabular angle reduction, (iv) Varus knee, (v) Expanded metaphyses, (vi) Long fibula and (vii) Short toes. Although previous literature has referred to the potential impact of some TRAVELS impairments on gross motor function, no research has formally evaluated the relationship between these factors. The aim of this study was to determine how TRAVELS musculoskeletal impairments relate to gross motor limitations and participation restrictions in children with achondroplasia. Study Design: Population-based, cross-sectional cohort. Methods: All children in a state-wide achondroplasia service aged 4 to 12 years were eligible (n=16) and 88% were recruited (n=14, 10 male, mean = 6 years 9 months, sd = 2 years 7 months). Children were assessed for (1) the four most common musculoskeletal impairments, i.e. i. thigh length, ii. foot length, iii. toe lengths and iv. tibia-fibula length ratio; (2) posture and motor ability using the Timed Up and Go (TUG), Timed Up and Down Stairs (TUDS), Forward Reach Test (FRT)); and (3) participation using the Mobility subset of the Functional Independence Measure for Children (Wee-FIM-IIT). Pearson s correlations were performed to examine if associations were present between musculoskeletal impairments and motor function or participation. In addition, multiple regression analyses were conducted for the four dependent variables of FRT, TUG, TUDS and WeeFIM-IIT to examine (i) the contribution of each musculoskeletal impairment, and (ii) the interrelationships between FRT, TUG, TUDS TM and WeeFIM-II. Results: All children (100%) demonstrated lower limb musculoskeletal impairments, as well as motor limitations and participation restrictions. Severity of limb shortening was moderately to strongly associated with severity of motor limitations on the TUG (all r>0.65, p<0.05) and TUDS (all r>-0.56, p<0.05) and participation restrictions on the Wee-FIM-II™ Mobility Subscale (all r>0.68, p<0.01). Shorter foot and second and third toe lengths were associated with shorter FRT distance (all r>0.57, p<0.05). There were no relationships with fibula-tibia length ratio. Greater participation restrictions (WeeFIM-II™ Functional Mobility) were associated with greater motor impairments on all measures (TUG, TUDS and FRT; all r>0.70, p<0.01).L6213533322018-03-27 <br />