Participants

The experimental protocol was conducted in accordance with the guidelines of our institutional review board, which approved the protocol for this study. All participants provided written informed consent. The informed consent for participants below the age of 20 years was provided by their parents.

This was a cross-sectional study. Between January 2012 and December 2015, a total of 155 patients (169 shoulders) with a mean age of 53 years (range, 15-81 years), with suspected SIS, and without global loss of passive range of motion (≤ 100° of forward flexion, ≤ 10° of external rotation with the arm adducted, and internal rotation of < the L5 level),39 underwent cine-MRI at one of our 2 institutions. Before testing, we excluded patients who experienced pain either at rest or in both active and passive internal and external rotation with the arm in an adducted position to eliminate the influence of pain on restriction of active rotational motion (n = 17). We excluded patients with collagen diseases (n = 4). A single surgeon confirmed that all patients were positive for at least 3 of the following tests: the painful arc sign,19 the Neer impingement test,30 the Hawkins–Kennedy impingement test,14 Jobe’s test,16 or the horizontal impingement test.44 The maneuver for the horizontal impingement test began with the examiner placing the patient’s arm in 90 degrees of shoulder abduction with the elbow flexed to 90 degrees and then rotating the arm internally. The test was considered positive if the patient experienced pain upon passive internal rotation. Thirty-four patients (29 shoulders) who were diagnosed with partial or full-thickness rotator cuff tears using MRI (T2-weighted coronal and sagittal images) were also excluded. None of the patients showed the presence of increased signal intensity or capsule edema around the axillary recess using fat-suppressed T2-weighted MRI, which strongly suggests capsulitis related to glenohumeral joint motion (sensitivity, 85.3−88.2%; specificity, 88.2%).10^,33 In addition, the same shoulder surgeon confirmed that all patients had no symptoms to warrant suspicion of frozen shoulder39 at least 1 month after MRI. Thus, 95 patients (100 shoulders), 62 men and 33 women with a mean age of 51 years (range, 16-81 years), were included in this study (Table I, Fig. 1).

Patient demographic data.

F, female; M, male; D, dominant; ND, nondominant; ER, external rotation; IR, internal rotation; ROM, range of motion; T, thoracic vertebra; B, buttock; UCLA, University of California in Los Angeles.

A flowchart showing the progressive inclusion and exclusion of subjects in this study. MRI, magnetic resonance imaging.