The supinator muscle: anatomical bases for deep branch of the radial nerve entrapment.
OBJECTIVE
Our goals were to carry out an anatomical description of the internal architecture of the supinator muscle in order to describe potentially compressive structures for the deep branch of the radial nerve (DBRN) and to establish reference landmarks for the surgical treatment of radial tunnel syndrome.


METHODS
Thirty upper limbs were dissected. The pennation angle of proximal and distal arcades of the supinator to the radial shaft axis was measured. Possible compressive structures of both superficial and deep heads of supinator were recorded. Proximal and distal arcades of the superficial layer of the supinator were classified according to their fiber content as tendinous, musculo-tendinous, muscular or membranous. The distances of superficial layer of the supinator muscle to the humeroradial joint line and lateral epicondyle were measured.


RESULTS
Pennation angle was 33.6° (±4.2°) for the superficial layer and 50.2° (±6.6°) for the deep layer. The difference was statistically significant (p < 0.0001). The proximal arcade was purely tendinous in 20 cases (66.7 %). The distal arcade was mainly tendinous or musculo-tendinous (70 %). The average distance between the lateral epicondyle and the proximal arcade was 41.6 mm. We did not find any other potentially compressive structure within DBRN course between both layers.


CONCLUSIONS
Our anatomical results about pennation angle could be used as a basis for a thorough functional study about the supinator. Both proximal and distal arcades appeared as the two zones ables to compress the DBRN. Their localization should help the surgeon for the DBRN neurolysis.
Institute of Anatomy, Faculty of Medicine, University of Lille-Nord de France, Place de Verdun, 59045, Lille Cedex, France. charles.berton@gmail.com
Charles
C
Berton
Guillaume
G
Wavreille
Frédéric
F
Lecomte
Bruno
B
Miletic
Hee-Jin
HJ
Kim
Christian
C
Fontaine
D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000033:anatomy & histology*; D009408:Nerve Compression Syndromes / Q000209:etiology* / Q000601:surgery; D011826:Radial Nerve / Q000033:anatomy & histology*; D020425:Radial Neuropathy / Q000209:etiology* / Q000601:surgery; D034941:Upper Extremity / Q000294:innervation*