Summary

Ultrasonographic measurements of subacromial structures in patients with subacromial pain demonstrate fair to good interrater reliability when performed by novice sonographers.

Abstract

Background

Ultrasonographic measurements of the subacromial structures are reliable in the hands of experienced sonographers, but it is unknown if inexperienced sonographers can achieve a satisfactory level of reliability.

Purpose

To investigate if standardized subacromial ultrasonographic measurements are reliable in the hands of novice sonographers.

Methods

Two novice sonographers, a medical student with no prior ultrasonographic experience and a junior orthopedic resident with limited shoulder ultrasonographic experience, completed a training phase with an experienced sonographer. The two novice sonographers subsequently performed standardized ultrasonographic measurements on patients, diagnosed with subacromial pain, recruited consecutively from an orthopedic outpatient clinic. The measurements were: supraspinatus tendon thickness, subacromial bursa thickness, acromio-humeral distance and an assessment of dynamic impingement (visual impingement of the supraspinatus tendon and the subacromial bursa between the humeral head and the anterolateral aspect of acromion). Intraclass correlation coefficients (ICC(2,1)), standard error of measurement (SEM), minimal detectable change (MDC), 95% Limits of Agreement (LOA) and Cohen’s unweighted kappa were used to evaluate reliability and agreement.

Results

Twenty-eight patients (mean age: 52 years; mean BMI: 27,5) were included (28 symptomatic and 20 asymptomatic shoulders). ICC-values of supraspinatus tendon thickness ranged from 0.73 to 0.77 (SEM 0.4–0.5 mm; MDC 1.2-1.4 mm). Subacromial bursa thickness ICC ranged from 0.41 to 0.88 (SEM 0.2–0.4 mm; MDC 0.4-1.0 mm) and acromio-humeral distance ICC ranged from 0.68 to 0.72 (SEM 0.9 mm; MDC 2.5-2.6 mm). Kappa of mechanical impingement in symptomatic shoulders was 0.29 and was driven by a discrepancy of positive findings between the raters (43% vs 18%).

Conclusion

Novice sonographers achieved good reliability for ultrasonographic measurements of supraspinatus tendon thickness and acromio-humeral distance. The reliability of subacromial bursa thickness ranged from fair to good, while the evaluation of mechanical impingement only resulted in fair reliability.