Reliability of coracohumeral distance and subcoracoid tendons in subacromial pain syndrome

This study investigated the intra-rater reliability of a novice ultrasound (US) examiner and the inter-rater reliability of two examiners (novice, expert) in the measures of coracohumeral distance at rest (CHD) and at 60 & DEG; of elevation without (CHD60) or with weights (CHD60w), tendon thickness of the long head of the biceps (LHB) and subscapularis (SCP). Twenty-one patients with subacromial pain syndrome (SAPS) and 20 asymptomatic participants were included. Intra and inter-rater reliability were tested with intraclass-correlation-coefficient (ICC), differences between raters were analyzed with Bland-Altman plots. Intra-rater reliability for CHD, CHD60 and CHD60w was excellent (ICC = 0.97-0.98) in asymptomatic participants, and good-to-excellent (0.88-0.93) in SAPS, while intra-rater reliability for LHB and SCP was good-to-excellent in asymptomatic participants (0.88-0.97) and in SAPS (0.90-0.92). Inter-rater reliability for CHD, CHD60 and CHD60w was moderate-to-good (0.70-0.90) in asymptomatic participants and good (0.85-0.87) in SAPS, in contrast inter-rater reliability for LHB and SCP was poor in asymptomatic participants (0.10-0.46) and poor-to-moderate (0.49-0.61) in SAPS. Bland-Altman plots revealed systematic and/or proportional bias for tendons' thickness. A novice showed good-to-excellent intra-rater reliability in all US measures, whereas in comparison to an expert a novice can measure reliably CHD, CHD60 and CHD60w, but not LHB and SCP, where more training is recommended.

Automated summary

This study examined the reliability of a novice ultrasound examiner and the agreement between two examiners (novice, expert) in measuring coracohumeral distance, tendon thickness of the long head of the biceps, and subscapularis. The results showed that the novice examiner had excellent intra-rater reliability in all measures, but had poorer inter-rater reliability compared to the expert examiner. The findings suggest that more training is needed for the novice in measuring tendon thickness.