Upper limb function in Achondroplasia and its relationship with upper limb musculoskeletal impairments

Abstract

Background and Objectives: Achondroplasia, or short-limbed dwarfism, is the most common form of skeletal dysplasia. Previous research shows that all young children with Achondroplasia have developmental delays and some have permanent difficulties with upper limb tasks. However, no study has investigated the specific cause of this, in particular the relationship between upper limb musculoskeletal impairments and fine motor performance has not been formally examined. The aim of this study was to examine the relationship between upper limb musculoskeletal impairments with upper limb performance in fine motor and self-care tasks in children with achondroplasia. Study Design: Population-based, cross-sectional study. Methods: All children in a state-wide achondroplasia service aged 4-12 years were eligible (n=16) and 88% were recruited (n=14, 10 male, mean=6 years 9 months, sd=2 years 7 months). Children participated in musculoskeletal assessment of (1) the four most common upper limb impairments in Achon-droplasia, i.e. humerus length, metacarpal lengths, finger lengths and elbow range, as well as (2) humerus-trunk length ratio. They also participated in upper limb functional assessment of (1) Fine Motor Precision and Manual Dexterity subsets of the Bruininks-Oseretsky Test of Motor Proficiency™ - Version 2 (BOT-2) and (2) the Self-Care subset of the Functional Independence Measure for Children (WeeFIM™). Pearson Correlation Coefficients were used to examine relationships between musculoskeletal impairments and upper limb function. Multiple regression analyses were used to determine which musculoskeletal variables could best explain the variance in upper limb function. Age was tested as a covariate. Results: All children (100%) demonstrated all four upper limb impairments as well as atypical humerus-trunk length ratios. All children also showed fine motor function limitations and self-care participation restrictions. When considering relationships between measures, the strongest predictor of lower Fine Motor Precision was shorter humeral length (Adj R2=0.47). The strongest predictor of lower Manual Dexterity was a larger humerus-trunk ratio (Adj R2=0.57). An atypical humerus-trunk ratio was also the strongest predictor of poorer Self-Care performance (Adj R2=0.54). The strongest multiple regression model predicting all three motor outcomes (Fine Motor Precision, Manual Dexterity and Self-care) was the combination of short humeral length and atypical humerus-trunk ratio (Adj R2=0.65). Conclusions: In this population-based cohort of children with achondroplasia, all displayed fine motor limitations and self-care restrictions that were strongly predicted by the degree of upper limb shortening and the relationship between limb shortening and trunk growth. This is important information for clinicians and families.L6213533872018-03-27 <br />