Suprascapular neuropathy in massive rotator cuff tears with severe fatty degeneration in the infraspinatus muscle.
OBJECTIVE
Our aim was to describe the atypical pattern of increased fatty degeneration in the infraspinatus muscle compared with the supraspinatus in patients with a massive rotator cuff tear. We also wished to describe the nerve conduction and electromyography findings in these patients.


METHODS
A cohort of patients undergoing surgery for a massive rotator cuff tear was identified and their clinical records obtained. Their MRI images were reviewed to ascertain the degree of retraction of the torn infraspinatus and supraspinatus muscles, and the degree of fatty degeneration in both muscles was recorded. Nerve conduction studies were also performed in those patients who showed more degeneration in the infraspinatus than in the supraspinatus.


RESULTS
Out of a total of 396 patients who underwent surgery for a massive rotator cuff tear between 2006 and 2015, 35 who had more severe fatty degeneration in the infraspinatus than in the supraspinatus were identified. There were 13 men and 22 women. Their mean age was 67.2 years (56 to 81). A total of 20 (57%) had grade 4 fatty degeneration as classified by Fuchs et al, in the infraspinatus. Patte grade 3 muscle retraction was seen in 25 patients (71%). In all, eight patients (23%) had abnormal nerve conduction studies. The mean retraction of the infraspinatus was 3.6 cm (2.1 to 4.8) in patients with more severe fatty degeneration in the infraspinatus, versus 3.0 cm (1.7 to 5.5) in those with more severe degeneration in the supraspinatus (p = 0.003). The retraction ratios were 0.98 (0.61 to 1.57) and 0.77 (0.38 to 1.92), respectively (p < 0.001).


CONCLUSIONS
Fatty degeneration affecting the infraspinatus more than the supraspinatus may be, in the context of a massive rotator cuff tear, due to entrapment of the suprascapular nerve at the spinoglenoid notch. Cite this article: Bone Joint J 2016;98-B:1505-9.
Seoul National University College of Medicine , Seoul National University Bundang Hospital, 300 Gumi-dong, Bundang-gu, Seongnam-si, Gyoenggi-do, South Korea.
B Y
BY
Kong
Seoul National University College of Medicine, Seoul National University Hospital, 28 Yeongeon-dong, Jongno-gu, Seoul, 110-744, South Korea.
S H
SH
Kim
Seoul National University College of Medicine, Seoul National University Hospital, 28 Yeongeon-dong, Jongno-gu, Seoul, 110-744, South Korea.
D H
DH
Kim
Seoul National University College of Medicine , Seoul National University Bundang Hospital, 300 Gumi-dong, Bundang-gu, Seongnam-si, Gyoenggi-do, South Korea.
H Y
HY
Joung
Seoul National University College of Medicine, Seoul National University Hospital, 28 Yeongeon-dong, Jongno-gu, Seoul, 110-744, South Korea.
Y H
YH
Jang
Seoul National University College of Medicine , Seoul National University Bundang Hospital, 300 Gumi-dong, Bundang-gu, Seongnam-si, Gyoenggi-do, South Korea.
J H
JH
Oh
D000273:Adipose Tissue / Q000000981:diagnostic imaging / Q000473:pathology; D000368:Aged; D001284:Atrophy / Q000000981:diagnostic imaging / Q000209:etiology; D004576:Electromyography / Q000379:methods; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000473:pathology*; D009408:Nerve Compression Syndromes / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology; D009431:Neural Conduction / Q000502:physiology; D010523:Peripheral Nervous System Diseases / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology; D012189:Retrospective Studies; D000070636:Rotator Cuff Injuries / Q000150:complications* / Q000000981:diagnostic imaging / Q000601:surgery*
Electromyography/nerve conduction study; Infraspinatus fatty degeneration; Massive rotator cuff tear; Retraction; Spinoglenoid notch; Suprascapular neuropathy