Normalized hand-behind-back for the measurement of shoulder internal rotation

BACKGROUND: The hand-behind-back (HBB) is a method for measuring the range of shoulder internal rotation; here, the highest vertebral level reached by the thumb is recorded. Alternatively, other specific landmarks may be used to measure its distance with the thumb. When the records of distance are adopted, it becomes difficult to compare individuals of different physiques, that is, comparing adults and children. In this study, we proposed a modified HBB method that attempts to normalize body size disparity and examined its reliability. METHODS: Three raters measured the modified HBB in 60 healthy subjects. A test-retest design was used, wherein each rater measured one trial, for a total of three trials each subject. The subject's thumb was actively and passively ascended along the spinal column as high as possible; subsequently, the distance between the C7 spinous process and tip of the thumb (C7-thumb) was measured with a tape. The HBB ratio (HBBR) was used as the parameter of shoulder internal rotation. It was defined as the ratio between the C7-thumb and the distance between the C7 spinous process and midpoint of the line connecting the posterior superior iliac spines (C7-posterior superior iliac spine). RESULTS: Intraclass correlation coefficients (model 2.1) ranged from 0.73 to 0.89, indicating that the reliability of the active and passive HBBR had moderate or good and good reliability, respectively. Bland-Altman analysis revealed that the values of minimal detectable changes were 0.053 and 0.036 for the active and passive measurements, respectively. CONCLUSION: The proposed method was confirmed to have sufficient reliability for clinical use. The HBBR may be used as a parameter of the shoulder internal rotation, which enables the comparison between individuals of different physiques.