Dynamic acromiohumeral impingement at the painful arc: dynamic digital radiography and multi-position CT with CT-derived 3D pose-based visualization: a case report

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Abstract Background Dynamic shoulder pain limited to a narrow range of abduction may not be adequately explained by static imaging alone. This case report described an angle-specific painful arc evaluated with dynamic digital radiography and multi-position computed tomography with CT-derived three-dimensional pose-based visualization. Case presentation A 32-year-old right-hand-dominant male patient presented with severe right shoulder pain 1 week after an overhead reaching injury. Active abduction was limited to 85 degrees, with maximal pain near 90 degrees and a QuickDASH score of 79.54. Dynamic digital radiography demonstrated narrowing of the acromiohumeral interval at the painful arc. Multi-position CT at 0 degrees, approximately 40 degrees, and approximately 80 degrees supported patient-specific three-dimensional pose-based visualization. For the same contralateral shoulder, the acromiohumeral distance was measured once at each position by one operator, yielding approximate estimates of 7.9, 3.7, and 5.3 mm, respectively. These position-specific values were descriptive and were not affected-side baseline and follow-up measurements. Standard shoulder MRI showed acromioclavicular joint marrow edema. At T1 immediately following one manual therapy session, clinical measures improved, but no imaging was obtained. Apart from this session, no medication, home exercise program, additional rehabilitation, injection, or activity restriction was introduced before the 1-week follow-up. At T2, pain had resolved, active abduction was 180 degrees, provocative tests were negative, and QuickDASH was 0. Repeat imaging was obtained at T2; however, the available data did not support a quantitative affected-side longitudinal comparison. No repeatability or minimal detectable change data were available. The clinical course and imaging observations were temporally associated but cannot establish treatment efficacy or exclude natural recovery. Conclusions This case illustrated that dynamic digital radiography may help identify motion-dependent acromiohumeral narrowing. Pose-specific CT-derived visualization may depict angle-specific spatial relationships and provide exploratory clearance estimates. These uncontrolled, case-specific observations do not establish treatment efficacy, affected-side interval change, or a normative side-to-side threshold.