Localization of the centers of intramuscular nerve dense regions of the rotator cuff muscles: A guide for botulinum toxin a injection for spasticity accompanied by shoulder pain

Abstract

SUMMARY: To accurately localize the centers of intramuscular nerve dense regions (CINDRs) of rotator cuff muscles. Twenty adult cadavers were used. The curves on skin connecting the superior angle of scapula with the acromion, and with the inferior angle of scapula were designed as the horizontal (H) and longitudinal (L) reference lines, respectively. One side of the rotator cuff muscles were removed and subjected to Sihler’s staining to show intramuscular nerve dense regions, and the contralateral muscles’ CINDRs were labeled with barium sulfate and scanned by computed tomography (to determine body surface projection points (P)). The intersection of the longitudinal line from point P to line H, and that of the horizontal line from point P to line L, were recorded as PH and PL, respectively. The projection of CINDRs on the anterior body surface across the saggital plane was defined as P' and the line connecting P to P' was recorded as Line PP'. Percentage positions of CINDRs of PH and PL on lines H and L, and the depths on line PP’ were determined under the Syngo system. Two, four, one, and one CINDRs were identified in supraspinatus, infraspinatus, teres minor, and subscapularis muscles, respectively. The positions of PH of these CINDRs on the H-line are as follows: supraspinatus, 25.43 % and 26.59 %; infraspinatus, 53.85 %, 34.63 %, 35.96 % and 58.17 %; teres minor, 74.50 %; and subscapularis, 20.33 %. The PL on the L-line: supraspinatus, 11.09 % and 14.83 %; infraspinatus, 21.59 %, 27.93 %, 48.55 % and 57.52 %; teres minor, 68.28 %; and subscapularis, 52.82 %. The depth on line PP': supraspinatus, 24.83 % and 25.40 %; infraspinatus, 21.55 %, 16.10 %, 10.01 % and 8.14 %; teres minor, 13.27 %; and subscapularis, 22.88 %. The identification of these CINDRs should provide the optimal target position for injecting botulinum toxin A to treat rotator cuff muscles spasticity accompanied by shoulder pain and to improve the efficiency and efficacy of blocking target localization.