5 Suprascapular Nerve Block
The upper trunk is formed by the roots of C5/C6. The suprascapular nerve branches from the brachial plexus in the region of the upper trunk (Fig. 5.1 and Fig. 5.2). It continues along the lateral border of the brachial plexus in the supraclavicular fossa as far as the scapular notch. After passing through the notch, which is bordered by the sometimes calcified superior transverse scapular ligament, it reaches the supraspinous fossa (Fig. 5.3).
The supraspinous fossa is shaped like a tub. On the floor of this “tub,” the nerve runs laterally and then passes along the posterior branch of the neck of the scapula to reach the infraspinous fossa and shoulder. It divides into a motor branch to the supraspinatus and infraspinatus muscles and gives off a sensory branch to the shoulder (Fig. 5.4, Fig. 5.5, Fig. 5.6).
5.2 Meier Approach
Meier et al (2002) were able to show from anatomical studies that dye, when injected on the floor of the supraspinous fossa, drains out through the notch and thus definitely reaches the suprascapular nerve (Fig. 5.7). Dangoisse et al (1994) and Feigl et al (2007) also arrived at similar results.
The patient is in sitting position with the head bent slightly forward. A line is drawn from the medial end of the spine of the scapula to the lateral posterior border of the acromion. Half way along this line, the injection site is established 2 cm medial and 2 cm cranial from this point (Fig. 5.8 and Fig. 5.9).
A 6-cm needle is advanced in a lateral direction on the floor of the supraspinous fossa at an angle of 75° to the skin surface. The needle should be directed roughly toward the head of the humerus (Fig. 5.10). For a continuous technique, the catheter is advanced 2 to 3 cm ahead (Fig. 5.11 and Fig. 5.12).
Needle: 6 cm
Continuous technique: pencil-point needle (catheter-through-needle technique)
Tips and Tricks
The block can be performed with or without a nerve stimulator. The presence of a motor response at 0.5 mA and 0.1 ms shows that the needle is in the correct position. If no nerve stimulator is used, bone contact is found and the needle is then withdrawn somewhat.
A catheter can be advanced without difficulty using a pencil-point needle with lateral opening that should be facing laterally.
The block technique takes advantage of the fact that the blade of the scapula forms a “tub” with the spine of the scapula that can be filled with local anesthetic. Local anesthetic thus reaches the suprascapular nerve through the scapular notch. There is practically no danger of causing pneumothorax (Büttner and Meier 2006).
An ultrasound-guided block is possible and easy to perform (Chan and Peng 2011).