Interscalene Block
The targets of anesthesia for this block are the roots and proximal trunks of the brachial plexus where they are sandwiched between the anterior and middle scalene muscles at the level of the sixth cervical vertebra (C6).
The trunks are contained within the interscalene fascial sheath at this level. This block is indicated mostly for surgical anesthesia to the shoulder, upper arm, and forearm, but is often insufficient for the hand. A continuous block via interscalene catheter provides excellent analgesia after shoulder arthroplasty.
The targets of anesthesia for this block are the roots and proximal trunks of the brachial plexus where they are sandwiched between the anterior and middle scalene muscles at the level of the sixth cervical vertebra (C6).
The trunks are contained within the interscalene fascial sheath at this level. This block is indicated mostly for surgical anesthesia to the shoulder, upper arm, and forearm, but is often insufficient for the hand. A continuous block via interscalene catheter provides excellent analgesia after shoulder arthroplasty.
Clinical Anatomy
From the intervertebral foramina, the 5 roots of the brachial plexus exit above the transverse processes of the corresponding cervical vertebrae and traverse through the interscalene groove before entering the floor of the posterior triangle of the neck.
The scalenus anterior and medius muscles lie immediately anterior and posterior to the plexus in the interscalene region and then insert onto the first rib.
The upper, middle and lower trunks are enclosed within the interscalene fascial sheath as they emerge between the scalene muscles.
At the level of the interscalene groove, the plexus is located cephaloposterior to the subclavian artery until it reaches the midpoint of the clavicle where the subclavian artery and vein are separated by the insertion of the anterior scalene.
The phrenic nerve normally descends anterior to the scalenus anterior muscle; it crosses the muscle from lateral to medial as it descends and passes under the clavicle.
From the intervertebral foramina, the 5 roots of the brachial plexus exit above the transverse processes of the corresponding cervical vertebrae and traverse through the interscalene groove before entering the floor of the posterior triangle of the neck.
The scalenus anterior and medius muscles lie immediately anterior and posterior to the plexus in the interscalene region and then insert onto the first rib.
The upper, middle and lower trunks are enclosed within the interscalene fascial sheath as they emerge between the scalene muscles.
At the level of the interscalene groove, the plexus is located cephaloposterior to the subclavian artery until it reaches the midpoint of the clavicle where the subclavian artery and vein are separated by the insertion of the anterior scalene.
The phrenic nerve normally descends anterior to the scalenus anterior muscle; it crosses the muscle from lateral to medial as it descends and passes under the clavicle.
Surface Anatomy
The main surface landmark (sternocleidomastoid muscle) used for this block can be accentuated by asking the patient to reach for the ipsilateral knee and by rotating the head approximately 45º to the non-operative side. The head should also be slightly elevated, and the patient should be instructed to take a deep breath (contraction of the scalenus muscles accentuates the interscalene groove).
The interscalene groove lies immediately behind the lateral border of the clavicular head of the sternocleidomastoid muscle at the level of the cricoid cartilage (C6) and is located approximately 1 cm above the separation of the sternal and clavicular heads of the sternocleidomastoid muscle.
The main surface landmark (sternocleidomastoid muscle) used for this block can be accentuated by asking the patient to reach for the ipsilateral knee and by rotating the head approximately 45º to the non-operative side. The head should also be slightly elevated, and the patient should be instructed to take a deep breath (contraction of the scalenus muscles accentuates the interscalene groove).
The interscalene groove lies immediately behind the lateral border of the clavicular head of the sternocleidomastoid muscle at the level of the cricoid cartilage (C6) and is located approximately 1 cm above the separation of the sternal and clavicular heads of the sternocleidomastoid muscle.
