Background: Spinal cord injury (SCI) is arguably one of the most devastating medical conditions and can lead to life changing consequences in all facets of function and existence.1 Physiotherapists routinely conduct muscle strength tests of their patients as part of the objective examination. Following SCI, the determination of muscle strength is important for a number of reasons including neurological classification of injury, therapeutic planning and outcome evaluation.2
A number of methods are available for assessing muscle strength; manual muscle testing (MMT), commonly using an ordinal scale developed by the Medical Research Council, isokinetic dynamometry (ID) via large scale computerized testing device and hand held dynamometry (HHD), which are smaller, portable testing devices.
Clinically it is important to understand the clinimetrics of the method being used to assess an individual's muscle strength so that physiotherapists can be guided towards using the most reliable, valid, responsive and interpretable method for adults with SCI.
Objectives: The objective of this systematic review was to examine the best available evidence on the clinimetrics of three main methods of assessing muscle strength in adults with SCI; MMT, ID and HHD. The clinimetric domains included were reliability, validity, responsiveness and interpretability. A further objective was to determine whether it is appropriate for HHD to become the standard tool for measuring muscle strength for adults with SCI.
Inclusion criteria: Types of participants
Adult population (15 years and older) with SCI regardless of the cause, time since injury, gender or ethnicity.
Focus of review
All studies which evaluated MMT, ID and HHD in all of their variations administered by any health professional.
Types of studies
All quantitative clinimetric studies regardless of design were sought. Studies which reported on the clinimetrics of MMT, ID and/or HHD, as well as those that used some form of comparison between the methods were considered.
Types of outcomes
The objective outcomes were measured in terms of the clinimetric domains of reliability, validity, responsiveness and interpretability for MMT, ID and HHD.
Search strategy: The search sought to identify any relevant published or unpublished studies via a three step search strategy.
Methodological quality: Two independent reviewers assessed the methodological quality of the studies using the quality evaluation tool consensus-based standards for the selection of health status instruments (COSMIN).
Data collection: An original data extraction form was developed to extract quantitative data from the included studies.
Data synthesis: It was not appropriate to conduct a meta-analysis due to the heterogeneity of the included studies. Therefore, the results are presented in narrative text including raw data as presented in the included studies as well as the contextual data.
Results: Eleven studies met the inclusion criteria of this systematic review. The results demonstrated that MMT showed varying inter-tester reliability over 10 muscle groups tested, ID demonstrated good reliability for the shoulder but not the elbow, HHD showed good reliability and validity for the upper limb and trunk, as well as good results for responsiveness and interpretability. Positive correlations were seen between MMT, ID and HHD particularly at the lower MMT grades. However, change in muscle strength scores seen on ID and HHD testing were not always correlated with changes in MMT grade. Significant overlapping of scores was seen between MMT and HHD particularly for grades 4 and 5 with MMT unable to detect subtle changes in muscle strength compared with dynamometry.
Conclusions: In conclusion, when considering the clinimetrics of the three methods for assessing muscle strength in adults with SCI there is support in the literature to recommend the wider application of HHD compared with MMT and ID.