Pectoral nerves I block is associated with a significant motor blockade with no dermatomal sensory changes: a prospective volunteer randomized-controlled double-blind study.

Purpose: The pectoral nerves (PECS) I block, first described in 2011 for surgery involving the pectoralis muscle, has principally been used for breast cancer surgery. No formal evaluation of its differential motor- and sensory-blocking abilities has been reported. We hypothesize that the PECS I block will produce a motor block of the pectoralis muscles with diminished upper limb adduction strength as measured with a handheld dynamometer.