Reproducibility and validity of measuring the length of upper extremity flexor muscles of the spastic forearm in acquired brain injury patients

Abstract

ABSTRACT Aim: The aim of this study is to determine the reproducibility and the criterion validity of a new instrument which measures the length of flexor muscles of the spastic forearm in acquired brain injury patients.

Methods: To determine the inter-rater reproducibility four raters measured with this new instrument. After the first measurement by the first rater, a second rater measured the same participant after at least 30 minutes and maximally 24 hours. One of the four raters, this was always the same rater, repeated the measurements within one week to determine the intra-rater reproducibility. The criterion validity was determined by a measurement performed by the regular physiotherapist with a manual goniometer. Statistical analyses were done by evaluating the Intraclass Correlation Coefficients (ICC), Limits of Agreement (LoA), Standard Error of Measurement (SEM) and Smallest Detectable Change (SDC).

Results: ICCs revealed an excellent inter-rater (ICC [2.1]: 0.933) and intra-rater reliability (ICC [3.1]: 0.990). Inter-rater agreement resulted in LoA of -19.3°to 20.4°, SEM of 7.3° and SDC of 20.2°. Intra-rater agreement revealed LoA of -7.5° to 7.5°, SEM of 2.7° and SDC of 7.5°. Criterion validity with the manual goniometer was indicated as good (Spearman rank correlation coefficient, rs: 0.772).

Conclusion: This study confirms an overall good reproducibility and criterion validity of a new instrument in a population in brain injury patients with a spastic wrist. However, a larger sample size is necessary to draw firm conclusions about the reproducibility and validity of this instrument.

Clinical Relevance: Besides the measurements properties, the clinical relevance of this study implies that this new instrument has the potential to be used in clinical practice by only one health care professional to determine the muscle length of the spastic wrist.