Abstract
BackgroundWrist movements become impaired with disease progression in various neuromuscular disorders. With the development of new therapies, thorough measurement of muscle strength is crucial to document natural disease progression and to assess treatment efficacy. We developed a new dynamometer enabling wrist flexion and extension torque measurement with high sensitivity. The aims of the present study were to collect norms for healthy children and adults, to compute predictive equations, to assess the reliability of the measurements and to test the feasibility of using the device in patients with a neuromuscular disease.MethodsThe peak isometric torque of wrist flexion and extension was measured with the MyoWrist dynamometer in 345 healthy subjects aged between 5 and 80 years old and in 9 patients with limb girdle muscle dystrophy type 2 C (LGMD2C) aged between 16 and 38 years old.ResultsPredictive equations are proposed for the wrist flexion and extension strength in children and adults. Intra-rater and inter-rater reliability was good with ICCs higher than 0.9 for both wrist flexion and extension. However, retest values were significantly higher by 4% than test results. The dynamometer was applied with no difficulty to patients with LGMD2C and was sensitive enough to detect strength as weak as 0.82 N.m. From our models, we quantified the mean strength of wrist extension in LGMD2C patients to 39 ± 17% of their predicted values.ConclusionsThe MyoWrist dynamometer provides reliable and sensitive measurement of both wrist flexion and extension torques. However, a training session is recommended before starting a study as a small but significant learning effect was observed. Strength deficit can be quantified from predictive equations that were computed from norms of healthy children and adults.
Highlights
Wrist movements become impaired with disease progression in various neuromuscular disorders
Because forearm circumference was significantly correlated with height in adults, even if the Pearson correlation coefficient is smaller than for children, and because neuromuscular disease should impact height less than forearm circumference, we considered height instead of forearm circumference in addition to age and gender as predictive variables of wrist flexion and extension torque in adults
Demonstration of the feasibility of the measurements in healthy or weak children and adults with good reliability guarantees the quality of results for clinical trials
Summary
Wrist movements become impaired with disease progression in various neuromuscular disorders. We developed a new dynamometer enabling wrist flexion and extension torque measurement with high sensitivity. Wrist flexion and extension strength have been previously assessed using different methods: Manual muscle testing (MMT) [3,4,5], hand-held dynamometry (HHD). Advantages and disadvantages of these various methods have previously been discussed [14] None of these methods is reliable and highly sensitive over a large range of strengths as well as being flexible for different upper limb dimensions or deformities (e.g. contractures). We developed a highly sensitive device, called the MyoWrist, designed for the assessment of both wrist flexion and extension torque with the same upper limb positioning in children and adults with the possibility of wrist angle adjustment for subjects with contractures.
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