Origin:
Anterior tubercles of the transverse processes of C3-C6 cervical vertebrae
Insertion:
Inner border of the first rib and upper surface of the rib in front of the subclavian groove
Nerve supply:
Anterior branches of the cervical nerves C5-C7
Blood supply:
Inferior thyroid artery (ascending cervical branch)
Function:
Neck flexion
Side flexion with unilateral contraction
Origin:
Posterior tubercles of the C3-7 cervical transverse processes
Insertion:
Upper surface of the 1st rib, between the scalene tubercle and the subclavian groove
Nerve supply:
Anterior rami of cervical spinal nerves C3 – C7
Blood supply:
Ascending cervical artery
Function:
Neck flexion
Side flexion and rotation with unilateral contraction
Accessory muscle of inspiration
Approach:
oPosition: supine with head at 30 degrees and head facing contralateral side
oIdentify and palpate interscalene groove
oInferior point of groove is just posterior to the subclavian artery pulse
oSubclavian pulse: palpate and the plane is just medial to the midpoint of the clavicle
oLocal skin anaesthetic injection
oAdvance needle directed just above and posterior to subclavian pulse and caudally directed at a flat needle angle with the skin
oAwait arm paresthesia or an action evoked muscle contraction in the arm
oAspirate to exclude vascular penetration
oNerve stimulation testing: stimulation evoke potential < 0.5mA, inject local 1 mL of local and confirmation of fading motor activity complete injection 0f 30-40 mL
