Acromiohumeral interval (AHI) is a useful and reliable measurement on AP shoulder radiographs and when narrowed is indicative of rotator cuff tear or tendinopathy.
Measurements of the AHI in the following intervals are suggestive of pathology 1-2:
- >12 mm: shoulder dislocation; inferior subluxation (e.g. from joint effusion)
- 9-10 mm (range 8-12mm): normal
- 6-7 mm: thinning of supraspinatus tendon
- <6 mm: supraspinatus tear
The shortest distance is measured.
- true AP shoulder radiograph
- measure from the cortical bone at the inferior aspect of the acromion to the humeral head 3
- can also be performed on coronal and sagittal oblique T1 MR images
- inferior aspect of the acromion (marked by black line directly above the humeral head) directly inferiorly to the centre of the subchondral cortex of the humeral head 3
- 1. Gruber G, Bernhardt GA, Clar H et-al. Measurement of the acromiohumeral interval on standardized anteroposterior radiographs: a prospective study of observer variability. J Shoulder Elbow Surg. 2010;19 (1): 10-3. doi:10.1016/j.jse.2009.04.010 - Pubmed citation
- 2. Davies AM. Imaging of the Shoulder: Techniques and Applications (Medical Radiology / Diagnostic Imaging). Springer. ISBN:B0014DAE8A. Read it at Google Books - Find it at Amazon
- 3. Saupe N, Pfirrmann CW, Schmid MR et-al. Association between rotator cuff abnormalities and reduced acromiohumeral distance. AJR Am J Roentgenol. 2006;187 (2): 376-82. doi:10.2214/AJR.05.0435 - Pubmed citation