Reliability of a new device used to measure shoulder subluxation

The purposes of the study were to determine the reliability of a new device used to quantify shoulder subluxation and to estimate its standard error of measurement. The device is an L-shaped thermoplastic jig with a metric tape measure embedded in it. A sliding beak-like marker, which can be anchored with a thumbscrew, is used to identify landmarks and to measure the amount of subluxation. Eight male and two female hemiplegic subjects, 40 to 80 years old, consented to be measured for subluxation. Three standardized subluxation measurements were taken by one investigator to determine the reliability with a single rater. One measurement was taken by a second investigator and compared with the first measurement obtained by the first investigator to determine the reliability using more than one rater. Both investigators were experienced physical therapists. Each measurement was read by the other investigator, who disassembled the jig and cleaned the marks from the patient between measurements. For both analyses, an analysis of variance for repeated measures reflected no differences between measurements attributable to raters. The unbiased intraclass correlation coefficent for a single measurement by a single rater was .89 (p < .01) and for more than one rater was .74 (p < .01). The standard error of measurement was ± 0.77 mm for a single rater and ± 1.20 mm for more than one rater. We recommend the jig as a tool to measure shoulder subluxation in patients.