Reliability and validity of ultrasonographic measurements of acromion-greater tuberosity distance in poststroke hemiplegia.

OBJECTIVES: The primary aim of this study was to assess the intrarater reliability of ultrasonographic measurements of acromion-greater tuberosity (AGT) distance in patients with stroke using portable ultrasound. A secondary aim was to determine the discriminant validity of the ultrasonographic technique by comparison of AGT distance measurements of stroke-affected and unaffected shoulders. DESIGN: Test-retest design. SETTING: Two local National Health Service hospitals in the South West of England. PARTICIPANTS: Patients with first-time stroke (N=26; 16 men, 10 women; mean age ± SD, 71±10y) with 1-sided weakness who gave informed consent were recruited. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Portable diagnostic ultrasound was used to record measurements on day 1 and again within a fortnight. Bedside measurements were undertaken by a single physical therapist with patients seated upright in a standard hospital chair. Intraclass correlation coefficients (ICCs) and standard errors of measurement were used to assess reliability. Minimum detectable change (MDC90) scores were used to estimate the magnitude of change that is likely to exceed measurement error. Repeated-measures analysis of variance (ANOVA) was used to assess discriminant validity. RESULTS: Mean ± SD AGT distances on the stroke-affected side and unaffected side were 2.3±0.6cm and 1.9±0.3cm, respectively. ICC for within-day reliability was .98 for the affected shoulder and .95 for the unaffected shoulder. Corresponding values for between-day reliability were .94 and .76. The standard error of measurement for both affected and unaffected shoulders was less than 0.2cm. Within-day MDC90 for the affected shoulder and the unaffected shoulder was ±0.2cm and ±0.1cm, respectively. Repeated-measures ANOVA showed a significant difference between mean AGT distance for the affected and unaffected shoulders. CONCLUSIONS: Ultrasonographic measurement of AGT distance demonstrates both intrarater reliability and discriminant validity and has the potential to assess shoulder subluxation in patients with stroke. Research into interrater reliability and concurrent validity of ultrasonographic measurements of AGT distance in patients with stroke is required.