Motor points for the neuromuscular blockade of the subscapularis muscle.

Abstract

To locate the motor points of the subscapularis muscle in relation to palpable anatomic landmarks and hence suggest a technique for botulinum toxin injection into subscapularis applicable to patients of all ages. Anatomic dissection of the innervation of 20 subscapular muscles. University dissecting room. Ten formalin-preserved cadavers. Not applicable. The location of motor points in relation to anatomic landmarks. The median number of motor points for the subscapularis was 5 (range, 3-6). All motor point measurements were related to surface points and converted into proportional values along reference lines. Motor points from the 20 dissections showed clustering in a band. A line of best fit was calculated (y=1.48x-0.743). We describe an injection technique that would deliver botulinum toxin close to the motor points of the subscapularis, a surrogate marker of the motor endplate zones. By using proportional distances, this technique is applicable to an adult and pediatric population. This should lead to an increased efficacy and decreased side-effect profile in clinical practice, although clinical trials will need to confirm this.