Development of a Portable Upper Limb Muscle Dynamometer for Assessment of Neuromuscular Injury Patients

Abstract

IntroductionPatient recovery from neuromuscular injuries that cause upper limb dysfunction is commonly assessed via manual methods. Manual muscle testing is subjective, time consuming and requires extensive training. Existing dynamometers are more objective, but they are prohibitively expensive and impractically large, making them inaccessible to most clinics and patients with disabilities. Our aim is to develop a table-top upper limb muscle dynamometer that provides standard positioning, ease of use and portability while giving clinicians consistent and reliable quantitative data on a patient’s isotonic and isometric muscle power and strength, respectively.MethodsThe device consists of a lever arm, a brushless DC motor, a load sensor and an ergonomic cuff. It outputs analog data via standard BNC connectors. The device can be intuitively controlled by the operator to test various upper limb joints and motions. Isometric measurement repeatability was assessed by recording the maximal voluntary contractions of 18 healthy participants over three trials.ResultsThe repeatability across 3 trials was 2.70±2.27 Nm (95th percentile: 6.74 Nm) for elbow flexion, and 2.83±2.13 Nm (95th percentile: 5.65 Nm) for elbow extension.ConclusionsThe dynamometer demonstrates a marked improvement in repeatability relative to manual muscle testing. Its small footprint and low cost can make it an easily accessible, standardized testing tool that requires little training to use. Future research and development will focus on using field-oriented control to measure isotonic muscle power in addition to isometric strength.