Assessing anterior shoulder instability: Reliability of the humeral head centralization test

In 25 patients with anterior shoulder instability, anterior humeral head translation during active elbow extension is greater than in 25 asymptomatic controls (p < .001), but ultrasound reliability is limited.

• Why it matters: Motor control impairment of rotator cuff muscles may destabilize the glenohumeral joint, yet there is no easily applied, reliable metric for quantifying anterior humeral head translation during active movement.
• What they did: A physical therapist used ultrasound to assess humeral head translation during shoulder external rotation and elbow extension in a case-control design, with blinded test-retest and inter-rater repeats by a radiologist after one week.
• The result: Test-retest agreement was poor for external rotation (ICC2,1 0.32, 95% CI -0.08-0.63) and moderate for elbow extension (ICC2,1 0.66, 95% CI 0.36-0.84), with moderate inter-rater reliability for both movements, so the current test cannot be recommended clinically or for research.

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