Sonia Lee MD, Presenter: Nothing to Disclose

Robert Lucas, Abstract Co-Author: Nothing to Disclose

Drew Lansdown, Abstract Co-Author: Nothing to Disclose

Lorenzo Nardo MD, Abstract Co-Author: Nothing to Disclose

Thomas M. Link MD, PhD, Abstract Co-Author: Research funded, General Electric Company Research funded, InSightec Ltd

Lynne S. Steinbach MD, Abstract Co-Author: Nothing to Disclose

C. Benjamin Ma MD, Abstract Co-Author: Nothing to Disclose

Roland Krug PhD, Abstract Co-Author: Nothing to Disclose

To assess traction suprascapular neuropathy in rotator cuff muscles by comparing fatty infiltration in muscles supplied by suprascapular nerve to that of axillary nerve in subjects with and without severe retraction.

After IRB approval, nine consecutive patients with retraction to the glenoid (severe retraction, SR) and nine age and rotator cuff tendon tear sized matched control subjects with less retraction (LR) were included. All subjects underwent routine clinical 3 Tesla non-contrast shoulder MR exam with additional chemical shift 6 point dixon IDEAL sequence for fat quantification. Rotator cuff muscles fat fractions were calculated by averaging the manually drawn region of interest on four consecutive sagittal fat fraction maps in each rotator cuff muscle at the scapular Y-view following previously published protocol. The average age, rotator cuff tendon tear size, degree of retraction and rotator cuff muscle fat fraction of SR were compared to LR using student t-test.

No significant difference was present in age or over all rotator cuff tear size between the two groups, SR and LR (65.1 vs. 67.4 years, P 0.27 and 4.9 vs. 4.9 cm, P 0.52). Average tendon retraction in SR and LR were 5.1 cm and 3.0 cm (P < 0.001). All patients had full thickness full width tear of supraspinatus tendon. SR group had larger infraspinatus tear (P 0.05), and smaller subscapularis tear size(P 0.07) compare to LR. SR showed increased muscle fat in not only supraspinatus (22.2 vs. 12.8 %, P 0.03* ), but also in infraspinatus (22.3 vs. 13.0 %, P 0.05) and subscapularis (19.9 vs. 12.3 %, P 0.08) to a similar degree despite less subscapularis tendon involvement. Teres minor fat fraction did not increase with rotator cuff tendon retraction (SR vs. LR, 6.3 vs. 8.6 %, P 0.84).

Significant elevation in fatty infiltration was seen in those with severe retraction in all rotator cuff except for teres minor supplied by axillary nerve. These results support supraspinatus neuropathy as significant contributor of muscle fatty infiltration.

Rotator cuff fatty infiltration, an indicator of poor post-surgical outcome, is not only affected by tendon tear but also significantly affected by neuropathy. MR fat quantification provides reliable and accurate assessment to study the association and possible causation of muscle infiltration, tendon pathology and nerve involvement. 

Lee, S, Lucas, R, Lansdown, D, Nardo, L, Link, T, Steinbach, L, Ma, C, Krug, R, Fatty Infiltration and Traction Suprascapular Neuropathy: Evaluation of Rotator Cuff Muscles with Differing Nerve Supply with MR Chemical Shift Fat Quantification.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14017021.html