Abstract
Background Muscle architecture is known to be predictive of muscle function. However, it is unknown whether this relationship is similar in children and adolescents with and without cerebral palsy (CP).
Objective The objective of this study was to determine whether the architecture of the rectus femoris (RF) and vastus lateralis (VL) muscles was predictive of maximum voluntary knee extensor torque in children and adolescents with and without CP and whether these measures were related to activity and participation levels.
Design A case-control design was used.
Methods Eighteen participants with CP (mean age=12.0 years, SD=3.2) at Gross Motor Function Classification System (GMFCS) levels I through IV and 12 age-matched peers with typical development (mean age=12.3 years, SD=3.9) were evaluated. Muscle thickness, fascicle length, and fascicle angle of the RF and VL muscles were measured with 2-dimensional, B-mode ultrasound imaging. The activity and participation measures used for participants with CP were the Pediatric Outcomes Data Collection Instrument (PODCI) and the Activities Scale for Kids, Performance Version (ASKp).
Results When age and GMFCS level were controlled for, VL muscle thickness was the best predictor of knee extensor isometric torque in the group with CP (R2=.85). This prediction was similar to the prediction from VL muscle thickness and age in participants with typical development (R2=.91). Rectus femoris muscle fascicle length was significantly correlated with the Sports and Physical Functioning Scale of the PODCI (ρ=.49), and VL muscle fascicle angle was correlated with the Transfers and Basic Mobility Scale of the PODCI (r=.47) and with ASKp Locomotion subdomain (r=.50).
Limitations A limitation of this study was the small sample size.
Conclusions Ultrasound measures of VL muscle thickness, adjusted for age and GMFCS level, were highly predictive of maximum torque and have the potential to serve as surrogate measures of voluntary strength (force-generating capacity) in children and adolescents with and without CP.
Footnotes
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Dr Moreau, Dr Teefey, and Dr Damiano provided concept/idea/research design. Dr Moreau and Dr Simpson provided writing. Dr Moreau provided data collection. Dr Moreau, Dr Simpson, and Dr Damiano provided data analysis. Dr Moreau provided project management and fund procurement. Dr Teefey and Dr Damiano provided facilities/equipment. Dr Teefey provided institutional liaisons. Dr Simpson and Dr Damiano provided consultation (including review of manuscript before submission).
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The authors thank Chris Stanley for assistance with data collection and processing and Dr Janice Brunstrom-Hernandez and Jennifer Miros, PT, MPT, for their support and assistance with recruitment. They thank GE Healthcare and Tania Gordley, Applications Specialist for GE Healthcare Ultrasound, for their support and technical assistance with this project.
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The study was approved by the Institutional Review Board at Washington University in St Louis, Missouri.
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Portions of this article were presented at the 62nd Annual Meeting of the American Academy for Cerebral Palsy and Developmental Medicine; September 17–20, 2008; Atlanta, Georgia; and the 2009 Combined Sections Meeting of the American Physical Therapy Association; February 9–12, 2009; Las Vegas, Nevada; and published in the proceedings in abstract format.
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Dr Moreau was a postdoctoral fellow in the Movement Science Program at Washington University, St Louis, Missouri, when this study was conducted and was supported by a National Center for Medical Rehabilitation Research/National Institutes of Health grant (T32HD007434-16). This project also was supported by a clinical research grant from the Section on Pediatrics of the American Physical Therapy Association. This research was supported, in part, by the Intramural Research Program of the NIH Clinical Center.
- Received November 13, 2009.
- Accepted June 22, 2010.
- © 2010 American Physical Therapy Association
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