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A transducer to measure isometric elbow moments
W D Memberg1, W M Murray, S I Ringleb
1Louis B. Stokes Veterans' Affairs Medical Center, Cleveland, OH, USA. wdm@po.cwru.edu
Objective:
The purpose of this study was to design and implement a transducer to measure accurately the isometric elbow moments produced by individuals with tetraplegia.
Design:
The device needed to be insensitive to off-axis moments and proximal joint motions and be capable of being used over a wide range of elbow and shoulder positions in an outpatient clinic setting.
Background:
Measurement of the smaller isometric moments produced by individuals with tetraplegia is especially sensitive to the errors that can be introduced by inaccurate lever arm determination, off-axis loads, and proximal joint motions. Devices traditionally utilized for quantifying isometric strength are difficult to implement for the spinal cord injured population.
Methods:
The elbow moment transducer consists of two four-bar parallelogram linkages joined by a lockable pivot. Strain gauges mounted on one beam of the parallelogram produce an output proportional to the elbow moment.
Results:
Calibration of the device indicates that it accurately quantifies isometric elbow moments over a range that is appropriate for evaluating elbow extension strength in individuals with tetraplegia.
Conclusions:
A device was developed and implemented that accurately quantifies isometric elbow moments over a range that is appropriate for evaluating elbow extension strength in individuals with tetraplegia.
Relevance:
The ability to quantitatively evaluate elbow strength in persons with tetraplegia is useful for understanding and improving the clinical outcomes of rehabilitative interventions that involve the elbow.