Cranial translation of the humeral head on radiographs in rotator cuff tear patients: the modified active abduction view.

Cranial translation of the humeral head is related to massive rotator cuff tears; however, it may be unapparent in early-stage tears. The goal of this study was to investigate whether active abduction leads to increased active cranial humeral translation in early-stage tears. We assessed 20 consecutive patients (9 full-thickness supraspinatus tears, 11 posterosuperior tears) using the newly introduced modified active abduction view: acromiohumeral (AH) distance was measured on radiographs acquired during rest and active isometric abduction and adduction tasks with the arm alongside the body. Rest AH was 7.5 mm (SD = 1.53); during abduction and adduction, it decreased to 2.1 mm (95 % CI 1.28-3.01, p < 0.001) and 1.1 mm (95 % CI 0.46-1.65, p = 0.001), respectively. Cranial translation during abduction was more severe in shoulders with posterosuperior cuff tears (∆AH = 3 mm, SD = 1.5) compared to supraspinatus tears (∆AH = 1 mm, SD = 1.6), with a mean difference of 2 mm (95 % CI 0.64-3.58, p = 0.007). Both active isometric abduction and adduction leads to active cranial translation in cuff tear patients. Cranial translation is largest during active abduction. Furthermore, there is significant more cranial translation in posterosuperior cuff tear patients compared to supraspinatus cuff tear patients. Possibly, radiographs combined with active tasks offer new possibilities in diagnosing early-stage rotator cuff tears.