Occupancy of the Suprascapular Notch by the Suprascapular Nerve: An Anatomic Study

The purpose of the study was to evaluate the dimensions of the suprascapular nerve and the suprascapular notch in freshfrozen cadaveric shoulders and to calculate the occupancy ratio of the notch, i.e. the space occupied by the suprascapular nerve and the superior transverse scapular ligament (STSL). The suprascapular nerve and the suprascapular notch were dissected, and the following parameters were included in the study: presence and shaper of the notch, dimensions of the lower border of the superior transverse scapular ligament and dimensions of the notch and the dimensions of the suprascapular nerve in two directions perpendicular to each other. All measurements were performed using a digital Vernier caliper. The cross-sectional area of the suprascapular nerve was assumed to be elliptical; the area of a U-shaped notch was assumed to be semi-elliptical and the area of the triangular-shaped notch were calculated accordingly. The area of the between the various notch types and the cross-sectional area of the suprascapular nerve in the various notch types were statistically compared. The reliability of continuous measurements was analyzed using intraclass correlation coefficients (ICCs). The suprascapular notch was present in all cases. A U-shaped notch was the most common type (22, 69%) followed by a triangular-shaped notch (10, 31%). The interobserver reliability of the suprascapular nerve and notch dimensions was excellent (ICC = 0.92 and 0.96 respectively). The cross-sectional area of the suprascapular nerve was 5.982.34 mm2 with no difference between the two body sides. The cross-sectional area of the U-shaped suprascapular notch was significantly larger than that of the V-shaped notch (19.98 5.34 mm2 versus 13.777.34 mm2, p=0.02). Correspondingly, the occupancy of the suprascapular notch by the suprascapular nerve was higher in V-shaped rather than U-shaped notches (37.199.34% versus 49.417.32%, p=0.03).