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Lower extremity selective voluntary motor control in patients with spastic cerebral palsy: evidence of increased distal motor impairnment


1. UCLA/Orthopaedic Hospital Center for Cerebral Palsy, University of California, Los Angeles, CA, USA;
2. Tarjan Center, University of California, Los Angeles, CA, USA;
3. Pediatrics, University of California, Los Angeles, CA, USA

Background/Objectives: Individuals with spastic cerebral palsy (CP) have multiple impairments contributing to motor deficits. Selective voluntary motor control (SVMC), the isolation of joint movement upon request, is an important factor that is often overlooked. Although increased involvement of distal joints has been described for other impairments, SVMC has not been systematically studied. The purpose of this study was to analyze the distribution of SVMC scores among lower extremity (LE) joints in patients with spastic CP.

Design: Cross-sectional

Participants and Setting: Forty-seven individuals (22male, 25 female) ages 4-23 years with spastic diplegic, hemiplegic and quadriplegic CP and GMFCS levels I (n=9), II (n=9), III (n=20) and IV (n=9) participated in this study at a university outpatient clinic. Participants who had LE muscle transfers or joint fusions were excluded.

Materials/Methods: Using a recently validated tool, Selective Control Assessment of the Lower Extremity (SCALE), SVMC of the hip, knee, ankle, subtalar joint and toes was evaluated by one of three testers. High interrater reliability was established (intraclass correlation coefficients range: 0.88-0.91). A score of Unable (0), Impaired (1) or Normal (2) was given for each joint. Pairwise comparisons were made among joints using the Friedman rank test with an overall test for trend (Page). Additionally, frequencies for all joint pair combinations within each LE were cross-tabulated. When the proximal joint score was equal to or greater than the distal one, we called this proximal to distal concordance (PDC). Percent PDC was calculated for all pairs.

Results: A significant decrease in scores from the hip to the toes was found bilaterally using the test for trend (p<0001). Statistically significant differences (p<.05) were found between all joint pairs except for toes vs. subtalar, toes vs. ankle and right ankle vs. subtalar joints. Percent PDC ranged from 81-100% for all joint pair combinations. Excluding comparisons between toes and subtalar joints, proximal scores were equal to or greater than distal ones 94-100% of the time.

Conclusions/Significance: Increasing SVMC impairment from proximal to distal joints was confirmed and agrees with increased distal involvement reported for strength and muscle activation patterns. Increased distal LE SVMC has implications for treatment planning and research. Good SVMC at distal joints implies good control of the entire LE. In contrast, high proximal scores or low distal scores do not predict control at other joints. Damage within the periventricular area is associated with spastic CP and corticospinal tracts responsible for SVMC are vulnerable to injury in this region. Tracts associated with distal LE musculature are closet to the ventricles and therefore are most vulnerable. Increased distal SVMC impairment is supported by this anatomical arrangement, but requires further investigation.

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