Assessing posterior shoulder contracture: the reliability and validity of measuring glenohumeral joint horizontal adduction.

CONTEXT Increased contracture of the dominant posterior shoulder in throwing athletes has been associated with the development of altered shoulder rotational motion as well as several shoulder conditions. Clinicians must be able to accurately and reliably measure posterior shoulder contractures during the evaluation of such athletes in order to provide appropriate treatment. OBJECTIVE To evaluate the reliability and validity of assessing posterior shoulder contracture by measuring supine glenohumeral (GH) horizontal adduction. DESIGN Descriptive with repeated measures. SETTING The biomechanics laboratory at Illinois State University (Normal, IL) and the athletic training room in Surprise, AZ. PATIENTS OR OTHER PARTICIPANTS Twenty-four shoulders were tested in 12 subjects (age = 21.9 +/- 4.3 years, height = 175.0 +/- 10.0 cm, mass = 82.4 +/- 19.1 kg) for determination of reliability, and 46 shoulders were tested in 23 professional baseball pitchers (age = 21.25 +/- 1.66 years, height = 190.0 +/- 5.0 cm, mass = 88.45 +/- 6.99 kg) for determination of validity. MAIN OUTCOME MEASURE(S) We examined intratester and intertester reliability over 3 testing sessions by having 2 examiners measure GH horizontal adduction with the subject in a supine position with the scapula stabilized. To determine the validity and clinical usefulness of this measurement, we examined the relationship between GH horizontal adduction motion and internal shoulder rotational motion among a group of baseball pitchers. RESULTS Intraclass correlation coefficients were high for intratester (0.93, SEM = 1.64 degrees ) and intertester (0.91, SEM = 1.71 degrees ) measurements. This measurement was also shown to have a moderate to good relationship with lost internal shoulder rotational motion ( r = .72, P = .001) of the dominant arm among the baseball pitchers. CONCLUSIONS Based on the results of this study, we found that measuring GH horizontal adduction with the subject supine and the scapula stabilized is a reliable and valid technique for assessing posterior shoulder contracture.