Ultrasound assessment of the inferior glenohumeral capsule in normal shoulders-a study of measurement variables and reliability

Objectives: To establish the reliability of a standardised ultrasound protocol to measure normal inferior gleno-humeral capsule (IGHC) thickness and to investigate the effects of age, sex, hand dominance and angles of abduction on the thickness.Methods: IGHC images were obtained at 60o, 90o and 180o abduction angles of 151 asymptomatic shoulders in supine position. Following the proposed guidelines, three sonographers blindly measured the IGHC thick-nesses for intra-and interrater reliability assessments.Results: The intrarater reliability was excellent (intraclass correlation coefficient value = 0.95; 95% CI = 0.92-0.97). The interrater reliability was moderate (intraclass corre-lation coefficient value = 0.74; 95% CI = 0.60-0.83). The mean IGHC thickness values in mm +/- SD at 60o, 90o and 180o abduction angles for males were 3.3 +/- 0.93, 3.0 +/- 0.80 and 2.6 +/- 0.55 and those for females were 2.7 +/- 0.86, 2.4 +/- 0.7 and 2.0 +/- 0.56 respectively. Although males had thicker IGHC, the rate at which the thickness reduced with increased abduction was same in both males and females. Age and hand dominance had no effect. Conclusion: The normal IGHC thickness varies with sex and the abduction angle of the arm at which it is meas-ured. A large variation of IGHC thickness exists in the normal population.Advances in knowledge: The results of this study discourage the use of a single value of IGHC thickness and emphasise the importance of comparing the thick-ness of the symptomatic side to that of the asympto-matic side of the same subject at the same abduction level. The guidelines provided in this study can be used in clinical practice and in future research studies.