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Mehbratu A1, Jain M1, Waite M1, Meilleur K2, Donkervoort S3, Leach M3, Foley AR3, Bonnemann C3
1National Institutes of Health, Clinical Research Center/Rehab Med Dept, Bethesda, United States, 2National Institute of Nursing Research, Neuromuscular Symptoms Unit, Bethesda, United States, 3National Institute of Neurological Disorders and Stroke, Neurogenetics Branch, Bethesda, United States
Background: COL6-related dystrophies (COL6-RDs) and LAMA2 related dystrophies (LAMA2-RDs) are both subtypes of congenital muscular dystrophies (CMDs) and involve disruptions in collagen type VI and laminin α2, respectively. Children affected with either COL6-RD or LAMA2-RD present with hypotonia, muscle weakness and joint contractures, but they demonstrate differing patterns of muscle weakness and progression of joint contractures related to the underlying pathophysiology of these two CMD subtypes.
Purpose: The purpose of this study was to understand the manner in which elbow and knee strength relate to joint contractures and how these contractures impact functional activities. We hypothesized that weak triceps muscles in comparison to biceps increase the risk of developing elbow flexion contractures, while weak quadriceps muscles in comparison to hamstrings increase the risk of developing knee flexion contractures. In addition, we hypothesized that the development of progressive elbow and knee contractures compromises functional abilities.
Methods: 100 individuals with COL6-RD (n=68) and LAMA2-RD (n=32) were seen in the physical therapy clinic at NIH between 2010 and 2018 as part of a natural history study. Patients ranged in age from 5-16 years of age, and 55 patients (55%) were female. Thirty-seven (54%) children with COL6-RD and 9 (28%) children with LAMA2-RD were ambulant. Assessments of strength, range of motion and functional abilities were completed by a pediatric physical therapist. Strength was recorded as newtons of force, using a handheld dynamometer; range of motion (ROM) was measured using a 2 arm goniometer; and functional ability was measured using the Motor Function Measure 32 (MFM32). Descriptive statistics and correlational analysis (Pearson) were completed using SPSS v25.
Results: Dominant extremity scores only are reported. Moderate correlations were identified between upper extremity function and: 1. elbow flexors, 2. elbow extensors and 3. elbow range of motion (r=0.506, r=0.491, r= 0.467; all p 0.01). There was a small inverse correlation between range of motion and elbow strength ratio (r= -0.216, p 0.05). For the lower extremity, strong correlations were observed between lower extremity function and 1. knee flexors, 2. knee extensors and 3. knee range of motion (r=0.737, r=0.699, r= 0.636; all p 0.01). There was a small inverse correlation between range of motion and knee strength ratio (r= -0.239, p 0.05).
Conclusion(s): The ratio of antagonist/agonist muscle strength did not appear to impact function or range of motion in either the upper or lower extremities. Despite the lack of strong correlations between strength and range of motion in the upper extremity, children with COL6-RD or LAMA2-RD in our cohort were still successful in functional tasks, suggesting the use of compensatory strategies. Due to the biomechanical disadvantages in the lower extremities, ambulatory and upright functional tasks were adversely impacted.
Implications: In children with COL6-RD and LAMA2-RD range of motion and function are not significantly affected by musculoskeletal factors. Rather, these types of deficits are likely resulting from their underlying pathophysiological condition.
Keywords: Pediatrics, Contractures, Functional abilites
Funding acknowledgements: This study was funded thru the NIH intramural program.
Purpose: The purpose of this study was to understand the manner in which elbow and knee strength relate to joint contractures and how these contractures impact functional activities. We hypothesized that weak triceps muscles in comparison to biceps increase the risk of developing elbow flexion contractures, while weak quadriceps muscles in comparison to hamstrings increase the risk of developing knee flexion contractures. In addition, we hypothesized that the development of progressive elbow and knee contractures compromises functional abilities.
Methods: 100 individuals with COL6-RD (n=68) and LAMA2-RD (n=32) were seen in the physical therapy clinic at NIH between 2010 and 2018 as part of a natural history study. Patients ranged in age from 5-16 years of age, and 55 patients (55%) were female. Thirty-seven (54%) children with COL6-RD and 9 (28%) children with LAMA2-RD were ambulant. Assessments of strength, range of motion and functional abilities were completed by a pediatric physical therapist. Strength was recorded as newtons of force, using a handheld dynamometer; range of motion (ROM) was measured using a 2 arm goniometer; and functional ability was measured using the Motor Function Measure 32 (MFM32). Descriptive statistics and correlational analysis (Pearson) were completed using SPSS v25.
Results: Dominant extremity scores only are reported. Moderate correlations were identified between upper extremity function and: 1. elbow flexors, 2. elbow extensors and 3. elbow range of motion (r=0.506, r=0.491, r= 0.467; all p 0.01). There was a small inverse correlation between range of motion and elbow strength ratio (r= -0.216, p 0.05). For the lower extremity, strong correlations were observed between lower extremity function and 1. knee flexors, 2. knee extensors and 3. knee range of motion (r=0.737, r=0.699, r= 0.636; all p 0.01). There was a small inverse correlation between range of motion and knee strength ratio (r= -0.239, p 0.05).
Conclusion(s): The ratio of antagonist/agonist muscle strength did not appear to impact function or range of motion in either the upper or lower extremities. Despite the lack of strong correlations between strength and range of motion in the upper extremity, children with COL6-RD or LAMA2-RD in our cohort were still successful in functional tasks, suggesting the use of compensatory strategies. Due to the biomechanical disadvantages in the lower extremities, ambulatory and upright functional tasks were adversely impacted.
Implications: In children with COL6-RD and LAMA2-RD range of motion and function are not significantly affected by musculoskeletal factors. Rather, these types of deficits are likely resulting from their underlying pathophysiological condition.
Keywords: Pediatrics, Contractures, Functional abilites
Funding acknowledgements: This study was funded thru the NIH intramural program.
Topic: Paediatrics; Outcome measurement; Neurology
Ethics approval required: Yes
Institution: National Institutes of Health
Ethics committee: Institutional Review Board
Ethics number: 12-N-0095
All authors, affiliations and abstracts have been published as submitted.
