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DOI:10.2214/AJR.07.3661
AJR 2008; 190:W378
© American Roentgen Ray Society

Reply

Niamh Hambly and Stephen Eustace

Mater Misericordiae University Hospital, Cappagh National Orthopaedic Hospital, Dublin, Ireland



 
WEB—This is a Web exclusive article.

We appreciate the comments made by Dr. Kramer [1] in his letter to the editor regarding the labeling of Figure 3B in our article, "Rotator Cuff Impingement: Correlation Between Findings on MRI and Outcome After Fluoroscopically Guided Subacromial Bursography and Steroid Injection [2]. We welcome the opportunity to reply.

In his letter, Kramer [1] correctly proposes that impingement in Figure 3B most likely relates to hypertrophic inflammatory change in the acromioclavicular joint rather than the structure arising from the inferior surface of the acromion, indicated by an arrow and annotated as an osteophyte. We agree that this structure likely represents bone outgrowth at the enthesis of the coracoacromial ligament. As we indicated in the legend, symptoms in this patient resolved after bursography with targeted steroid injection, negating the need for surgical decompression.

The definition of an osteophyte is an abnormal bone outgrowth developing as a result of abnormally imposed mechanical forces, most common in weight bearing joints. In non-weight-bearing joints, such as the shoulder, damage to the glenoid labrum (secondary to neuropathy or arthropathy) facilitates recurrent impaction, abnormal load, and development of osteophytes at the glenohumeral articular surfaces. Similarly, recurrent impaction at the acromioclavicular joint may lead to damage to shock absorber cartilage and the development of an osteophyte. We agree with Kramer [1] that because osteophytes contain both cortex and central marrow, they should show the same marrow signal as adjacent bone.

Abnormal bone outgrowth may also occur at the site of ligament attachment to bone (the enthesis) because of long-standing traction effect. Traction changes at the enthesis reflect overgrowth of cortical bone and therefore typically manifest signal hypointensity on T1, T2, and fat-suppressed MR images. In his letter, Kramer [1] correctly describes the bone outgrowth labeled in Figure 3B as arising from the enthesis of the coracoacromial ligament. We recognize that many radiologists consider this appearance to represent a pseudospur as opposed to a true osteophyte and that in its most subtle form it may represent ligament attachment alone without bone outgrowth [3]. We also recognize that some authors have attributed this appearance to a slip of the attachment of the deltoid muscle [4].


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  1. Kramer M. Undersurface acromial osteophyte or subacromial enthesophyte? (letter) AJR 2008;190 : W376-W377[Free Full Text]
  2. Hambly N, Fitzpatrick P, MacMahon P, Eustace S. Rotator cuff impingement: correlation between findings on MRI and outcome after fluoroscopically guided subacromial bursography and steroid injection. AJR 2007; 189:1179 -1184[Abstract/Free Full Text]
  3. Stoller DW. Magnetic resonance imaging in orthopaedics and sports medicine, 2nd ed. Philadelphia, PA: Lippincott-Raven,1997 : 624-627
  4. Kaplan PA, Bryans KC, Davick JP, Otte M, Stinson WW, Dussault RG. MR imaging of the normal shoulder: variants and pitfalls. Radiology 1992;184 : 519-524[Abstract/Free Full Text]

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