The spinal root origins and clinical implications of the lower subscapular nerve.

The purpose of this study was to define the spinal root origins of the lower subscapular nerve and the amounts of participating nerve fibers from each spinal root and to discuss the clinical implications. Using a method of separating the nerve fascicles that traces the particular nerve fibers at the intrafascicular level, the spinal root origins of the lower subscapular nerve appeared as two types. The first type comprised 76.9% and was composed of the C5, C6, and C7 roots; the second type comprised 23.1% and was composed of the C6 and C7 roots. The number of nerve fibers was 357.2 +/- 139.7 (mean +/- SD) derived from C5, 1070.4 +/- 390.6 from C6, and 500.0 +/- 285.4 from C7. The nerve fascicles comprising the lower subscapular nerve traveled within the partially common fascicles composed of the axillary nerve. Therefore, injury of the lower subscapular nerve may be accompanied by a lesion of the axillary nerve, which generally consists of C5 and C6 roots composing the posterior cord of the brachial plexus.