Association of suprascapular neuropathy with rotator cuff tendon tears and fatty degeneration.
BACKGROUND
The mutual influence of suprascapular neuropathy (SSN) and rotator cuff tendon tears on muscle pathology is unclear. Debate continues as to how retracted cuff tears can lead to SSN and whether SSN or tendon retraction causes muscle fatty degeneration.


METHODS
A cohort of 87 patients suspected of having SSN was identified from a prospectively collected registry. All underwent electromyography/nerve conduction velocity study (EMG/NCV) and magnetic resonance imaging (MRI) of their shoulders. EMG/NCVs were performed and interpreted by electrodiagnosticians, and MRI cuff tendon quality and muscle fatty degeneration were interpreted by two surgeons.


RESULTS
Out of 87 patients, 32 patients had SSN on EMG/NCV, and 55 patients had normal suprascapular nerve. MRI showed that 59 of 87 supraspinatus had no fatty degeneration or mild fatty streaks (Goutallier grades 0 and 1), and 28 patients had significant fatty degeneration (grades 2-4); infraspinatus fatty degeneration was similar. Review of supraspinatus tendon showed 41 patients with intact tendons or partial tears, and 46 with full tears. Infraspinatus tendons pathology was similar. Tendon pathology and fatty degeneration were related (P-value<.001), with more severe tendon pathology leading to higher degree of fatty degeneration. Infraspinatus tendon tears were associated with SSN (P = .01), but SSN was not related to fatty degeneration of either supraspinatus or infraspinatus (P-values .65, .54).


CONCLUSIONS
The exact association and etiology of SSN in patients with rotator cuff pathology remain unclear. SSN is correlated to tendon tear size, but it does not have significant influence on fatty degeneration of either supraspinatus or infraspinatus.
Department of Orthopaedic Surgery and Rehabilitation Medicine, University of Chicago Medical Center, Chicago, IL, USA.
Lewis L
LL
Shi
Blue Ridge Bone and Joint Clinic, Asheville, NC, USA.
Robert E
RE
Boykin
Division of Shoulder Surgery and Sports Medicine, University of Pittsburgh UPMC, Center for Sports Medicine, Pittsburgh, PA, USA.
Albert
A
Lin
Harvard Shoulder Service, Massachusetts General Hospital, Boston, MA, USA. Electronic address: jwarner@partners.org.
Jon J P
JJ
Warner
D000273:Adipose Tissue / Q000473:pathology*; D000293:Adolescent; D000328:Adult; D000368:Aged; D003240:Connective Tissue Diseases / Q000175:diagnosis / Q000209:etiology*; D004576:Electromyography; D005260:Female; D006801:Humans; D022125:Lacerations / Q000150:complications*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009431:Neural Conduction; D010523:Peripheral Nervous System Diseases / Q000175:diagnosis / Q000209:etiology*; D017006:Rotator Cuff / Q000294:innervation / Q000473:pathology / Q000601:surgery; D000070636:Rotator Cuff Injuries; D055815:Young Adult
Suprascapular nerve; electromyography; fatty degeneration; nerve conduction velocity; rotator cuff tear