**2. Regional anesthesia for shoulder and clavicle surgery**

Since shoulder surgeries produce severe postoperative pain, regional anesthesia techniques could effectively control pain at rest and in motion, reduce muscle spasm and facilitate early discharge [1].

#### **2.1 Shoulder innervation**

#### *2.1.1 The brachial plexus (BP)*

The BP is formed by the fusion of the ventral ramus of the spinal nerves C5, C6, C7, C8, and T1, with the variable contribution of C4 (15-62% of cases) and T2 (16- 73% of cases). The roots emerge in the groove between the anterior scalenus and middle scalenus muscles [2]. Shoulder and proximal arm innervation are provided by branches of the BP: suprascapular nerve (SSN) (from posterior division of UT), axillary and subscapular nerves (from posterior cord), lateral pectoral nerve, and medial brachial cutaneous nerve (MBCN)) (from lateral cord), and the intercostobrachial nerve (ICBN) (originating directly from proximal intercostal nerves). SSN may be spared by an infraclavicular approach (**Figure 1**) [3, 4].

#### *2.1.2 Articular branches to the shoulder*

The most frequently identified innervation pattern comprises three nerve bridges consisting of articular branches from suprascapular, axillary, and lateral pectoral nerves, connecting trigger points (**Figures 2** and **3**) [5–7].

#### *2.1.3 Nerves and articular branches*

#### *2.1.3.1 Suprascapular nerve*

Articular branches classified in relation to the spinoglenoid notch:


*Regional Anesthesia for Shoulder and Clavicle Surgery DOI: http://dx.doi.org/10.5772/intechopen.101939*

#### **Figure 1.**

*Brachial plexus. Roots – Start in the spinal cord. Arise from anterior rami C5-T1. Landmark: Pass inferolateral between the anterior and middle scalene muscles. Trunks –the roots merge: Superior/upper (C5/C6); middle (C7); inferior/lower (C8/T1). Landmark – Usually found between scalene muscles and 1st rib. Divisions –the trunks split each one into 3 anterior divisions and posterior divisions. Landmark – Divide around the 1st rib and pass under the clavicle. Cords: 3 cords – Termed according to relation to the axillary artery. Posterior (made up of all 3 trunks posterior divisions - contains all C5-T1 fibers). Lateral (anterior divisions of superior and middle trunks – Contains C5-C7). Medial (anterior division of inferior trunk – Contains C8-T1). Landmark – Runs alongside the axillary artery lateral to the clavicle [2]. The roots C5, C6, C7, and C8 pass behind the vertebral artery and settle in the respective groove of the transverse process, they are directed laterally and inferiorly towards the first rib, where they merge to form trunks. The ventral branch of T1 passes over the first rib and travels higher and laterally to join C8 at the level of the groove that the plexus produces over the first rib. The anterior ramus of spinal nerve C5 contributes to the PN; the anterior ramus of spinal nerve T1 branches to become the first intercostal nerve. These nerves are not considered part of the BP.*

#### *2.1.3.2 Axillary nerve (AN)*

One or two articular branches of the main trunk travel with the anterior humeral circumflex artery between the tendons of the subscapular and latissimus dorsi muscles branching into medial branch to scapular aspect of the anteroinferior capsule and portions of the axillary recess; lateral branch to humeral portion of the anterior capsule [6]. The posterior division (after leaving the quadrangular space) gives a branch for the teres minor muscle, from which emerge 1 to 4 articular branches, to innervate the posteroinferior capsule. The branch innervating the deltoid muscle gives small multiple articular branches towards the lateral aspect of the humeral head the posterior and lateral supra-lying fascia of the shoulder capsule [6, 9, 10].

#### *2.1.3.3 Lateral pectoral nerve (LPN)*

The LPN arises from two branches of the anterior divisions of the upper and middle trunks (33.8% of cases), or as a single root of the lateral cord (23.4%). It

#### **Figure 2.**

*Distribution of shoulder articular branches. Courtesy of MF Rojas.*

#### **Figure 3.** *Shoulder structures and their related innervation.*

receives fibers from C5 to C7. Cross the superomedial side of the coracoid process and sends small branches to the coracoclavicular and coracoacromial ligaments, anterior acromioclavicular joint, subacromial bursa and anterosuperior portion of the glenohumeral capsule. It gives branches to the periosteum of the clavicle. Therefore, its blockade produces analgesia for distal clavicle surgery [6, 11]. The muscular branch originates from the articular branch of the LPN and innervates the deltoid muscle and skin over the subacromial region (**Figure 4**) [7, 11].

**Figure 4.** *Lateral pectoral nerve.*

#### *2.1.3.4 Inferior subscapular nerve*

A glenohumeral articular branch anastomosis with branches of the AN to innervate the long head of the biceps tendon (LHBT) and anterior capsule. The superior subscapular nerve gives 1 or 2 articular branches to innervate the anterosuperior quadrant of the glenohumeral joint [12]. Receives fibers for C5-C6.

The *SSN* is (individually) the largest contributor to global shoulder innervation: posterior glenohumeral capsule, subacromial bursa, coracoacromial and acromioclavicular ligaments. The *AN* innervates portions involving the inferior portion of the anterior and posterior glenohumeral capsule. The anterior face has a more complex innervation pattern: the medial portion is mainly innervated by muscular branches of the inferior subscapular nerve; the lateral face of the capsule is supplied by articular branches originating directly from the AN; the lateral pectoral nerve innervates the anterosuperior quadrant of the shoulder, including the anterior edge of the subacromial bursa, coracoacromial ligament, and glenohumeral capsule. Therefore, nerves other than suprascapular participate in the innervation of most of the joint. See **Figures 1**–**3**.

Mechanoreceptors are more concentrated in the medial and lateral insertions of the anterior capsule. Nociceptors are identified primarily in the upper quadrant of the shoulder, including the subacromial bursa (SAB), glenohumeral ligaments (GHL), coracoacromial (CAL), coracoclavicular ligaments (CCL), the proximal portion of the LHBT, and the transverse humeral ligament (THL). The SAB is the area of densest and tripolar nociceptive innervation. These three nociceptive poles may correspond to the location of the lateral/medial subacromial branches of the SSN (i.e., lateral and middle poles) and the articular branch of the lateral pectoral nerve LPN (anterior pole); Thin articular branches of the AN may also participate in the innervation of the lateral pole of SAB [6].

#### **2.2 Clavicle innervation**

The most painful structures in clavicle surgery include the skin over the incision area and the highly innervated periosteum. The supraclavicular nerve originates

#### **Figure 5.**

as a single trunk from the anterior ramus of cervical nerves C3-C4. It divides into medial (suprasternal), intermediate (supraclavicular), and lateral (supra-acromial) branches. The medial branch supplements the skin over the anterior aspect of the thorax, as far below as the second rib, and the sternoclavicular joint. The intermediate branch pierces the deep cervical fascia just above the clavicle and runs over the pectoralis major and deltoid muscle; supply cutaneous innervation to the skin above

#### *Regional Anesthesia for Shoulder and Clavicle Surgery DOI: http://dx.doi.org/10.5772/intechopen.101939*

these muscles, as far below as the second rib. The lateral branch pierces the deep cervical fascia just above the clavicle, passes over the acromial process, to innervate skin of the upper and posterior shoulder regions (**Figure 5**) [13, 14].

Innervation of the clavicle itself is less well described. Different authors attribute contributions from SSN, long thoracic, nerve for the subclavian muscle, and LPN [15].

#### *2.2.1 Fascias related to the clavicle*

#### *2.2.1.1 Clavipectoral fascia*

Situated posterior to the clavicular part of the pectoralis major muscle. It extends from the clavicle, costochondral joints, and coracoid process. It converges in the axilla and acts as a protective structure over the neurovascular package. The clavicular fascia splits to enclose the subclavius muscle before attaching to the clavicle, the posterior layer fuses with the deep cervical fascia which connects the omohyoid muscle to the clavicle. Medially, it is attached to the first rib before coming together with the fascia over the first two intercostal spaces. Laterally, it is attached to the coracoid process before blending with the coracoclavicular ligament. The fascia often thickens to form the costocoracoid ligament, between the first rib and coracoid process. Inferiorly, the fascia becomes thin, splits around pectoralis minor, and descends to blend with the axillary fascia and laterally with the fascia over the short head of the biceps. It is pierced by CALL [cephalic vein, artery (thoracoacromial), lateral pectoral nerve, lymphatics]. The clavipectoral fascia surrounds the clavicle, and the nerve endings of the clavicle penetrate this fascia (**Figure 6**) [16].

## **3. Peripheral nerve block for shoulder surgery**

Interscalene or supraclavicular block of the BP are considered the standard technique for anesthesia and analgesia in this type of surgery. The most common adverse effect is HDP due to ipsilateral PN block in 100% of patients and a 27% decrease in forced vital capacity and forced expiratory volume at the first second [17]. At the level of the cricoid cartilage (C6 transverse process (TP)) the PN is 0.18 cm prior to the BP, but it diverges at a rate of 3 mm for each centimeter below the cricoid cartilage.

USG has allowed to decrease the anesthetic minimum volume required in 50% of patients (5-7 mL vs. 30-40 mL) using ropivacaine 0.75% or bupivacaine 0.5%, and a decrease of 50% in the incidence of paralysis of the diaphragm when the injection is performed laterally to the C5-C6 roots. If the concentration of the anesthetic is also diluted to a half or third, the HDP rate is reduced to 20% (it is still a contraindication in patients with decreased lung reserve) but carries the risk of not achieving surgical anesthesia and decreasing the duration of the blockade. According to Renes et al., if the injection is done at the C7 root level, the minimum volume required to block C5-C6 in 50% of patients was 2.9 mL (maximum volume of 6 mL), with no PN block (although there is a substantial risk of vascular lesions from punctures at this level). Renes et al. avoided PN block by administering the anesthetic in the "cornet pocket " (intersection of the first rib with the subclavian artery and posterolateral aspect of the BP) and a volume less than 20 ml [18]. Aliste et al. compared ISB with supraclavicular block following the Renes technique, finding equal pain control, but with HDP rate of 9% [19]. Cornish found a 1% of HDP rate by advancing a catheter from the supraclavicular level and locating the tip at the infraclavicular level, inferomedial to the coracoid process [20, 21].

A combination that could be effective would be the association of a SSN block with a BP block at infraclavicular level [22] (addresses the axillary, lateral pectoral, subscapular nerves), although Petrar et al. [23] reported a 3% incidence of HDP during infraclavicular BP block (30 mL ropivacaine 0.5%).

The following paragraphs describe different techniques to achieve a selective block of the nerves supplying the shoulder.

#### **3.1 Upper trunk (UT) approach**

It focuses on the anesthetic deposit near the UT, before the take of the SSN. At this level, the phrenic nerve (PN) has diverged from the BP. Compoy et al. [24] found that 5 mL of methylene blue injected around UT stains SSN, lateral pectoral nerve, and roots of C5 and C6, but not of the PN [25]. Kim et al. found analgesic equivalence between UT block and ISB, achieving equivalent surgical anesthesia and HDP incidence of 5% vs. 71% using 15 mL of injectate [26]. Ultrasound (US) examination reveals the plexus in the groove between the anterior and middle scalene muscles, deep to the prevertebral fascia. The sternocleidomastoid muscle (SCM) lies superficially, and the PN can be seen on the anterior surface of the anterior scalene muscle (ASM), crossing it towards the medial side, after the last contribution originating in the C5 root. Sonoanatomy of the transverse processes can be used to identify spinal roots. Serial images reveal the process of confirmation of the UT [27].

The blocking needle is advanced from lateral to medial, under the deep cervical fascia until its tip reaches the UT lateral edge, proximal to the exit of the SSN (it is identified as a rounded hypoechoic structure that separates laterally from the UT and runs deep to the omohyoid muscle). The needle does not pass through the middle scalene muscle (MSM), where the dorsal scapular nerve (DSN) and long thoracic nerve (LTN) are located. The injectate volume is 7 to 12 mL of local anesthetic (LA) (one-half or one-third strength). Here the nerves have a greater amount of perineural tissue, protecting against neurological dysfunction, which has been reported in about 14% of ISBP blocks and can last for up to 10 days (**Figure 7**).

The UT provides anesthesia to nerves from the spinal cord segments C5 and C6 (originating fiber to SSN and AN, inferior subscapular nerve, and partially, to LPN) [25] and decreases the incidence and severity of PN block. HDP was observed in 97.5% in ISB vs. 76.3% of the UT block groups (P = 0.006); paresis was complete in 72.5% vs. 5.3% of the patients, respectively. The decrease in spirometry values from baseline was significantly greater in the ISB block group. UT block provides non inferior analgesia compared to ISBP block [28].

It can be supplemented with blockade of the supraclavicular nerves to anesthetize the skin over the shoulder. The needle is retracted to the space between prevertebral fascia (over the MSM) and superficial (enveloping) layer of the deep cervical fascia, under the SCM, where the supraclavicular nerves are located. A new injection of 2 to 3 mL of LA blocks nerves supplying skin over collarbone and shoulder cap and their sensitive contribution to the acromioclavicular joint.

#### **3.2 Supraclavicular nerve trunk blockade**

The supraclavicular nerve trunk (C3 and C4) emerges at the posterior edge of SCM. The superficial cervical plexus (SCP) is localized by placing a transducer on the posterior edge of the SCM at the level of the upper pole of the thyroid cartilage. It can be difficult to identify the individual nerves. The greater auricular nerve (GAN) is a useful reference reliably identified as a small superficial hypoechoic round structure on SCM (**Figure 8**) [29].

*Regional Anesthesia for Shoulder and Clavicle Surgery DOI: http://dx.doi.org/10.5772/intechopen.101939*

#### **Figure 7.**

*Upper trunk and supraclavicular nerves blockade. A. C5 and C6 (bifid) roots at interscalene space, near to PN. C7 TP view. B. UT formation (inferior to C7 TP). C. Origin of supraescapular nerve (SSN). D. Back to UT - needle at its posterior surface. Local anesthetic (LA) injection at posterior surface of UT. E. Retreated needle to space between SCM-MSM. LA injected around supraclavicular nerves***.**

#### **3.3 SSN blockade**

The posterior approach in the suprascapular fossa (in the space between the suprascapular notch and the spinoglenoid notch) where the nerve travels through its floor under the supraspinatus muscle fascia, results in adequate flooding of SSN with minimal propagation to the BP [30] but may spare MSAb. This approach is inferior to ISBP block for pain control, at least in the first 4 hours [31–33]. The UT (C5-C6) is the major contributor to the suprascapular, axillary, and subscapular nerves. Hence, UT blockade can provide adequate control of shoulder pain, but it is still remarkably close to the PN [34, 35].

With ultrasound image, the SSN could be identified as it branches from UT, and runs laterodorsally underneath the omohyoid muscle, in 81% of cases vs. 36% in the supraspinatus fossa, at an average depth of 8 mm vs. 35 mm in the supraspinatus fossa. Peripheral nerve stimulator can help in the identification [35]. Rothe et al.

#### **Figure 8.** *Supraclavicular nerve trunk and SCP scan process.*

studied twelve healthy volunteers; the SSN was followed into the subclavian triangle under the inferior belly of the omohyoid muscle; injecting 1 mL of lidocaine 2%, 10 blocks were performed, 8 demonstrated a reduced manual muscle-testing scale (MMT) of the supra- and infraspinatus muscles at 15 min and 30 min; increasing

*Regional Anesthesia for Shoulder and Clavicle Surgery DOI: http://dx.doi.org/10.5772/intechopen.101939*

#### **Figure 9.**

*Scan sequence of the SSN at the supraclavicular fossa. A: Locate the transverse process of C6 vertebral vertebra and C6 and C5 roots. B: Scanning downward, locate the C7 TP and C7 root, which can be seen laterally to vertebral vessels. C: Just below the C7 transverse process, C7 root runs towards the interscalene groove. The PN is diverging from the BP, on the anterior surface ASM. Caudally to the C7 transverse process, UT and MT conformation can be imaged. D: In the supraclavicular fossa. From the UT branches the SSN. E: The SSN travels below the omohyoid muscle. F: The SSN separates from the UT, below omohyoid muscle. The nerve goes along suprascapular artery.*

the injected volume, produced musculocutaneous and radial nerves blockade due to cephalic diffusion of the anesthetic (**Figure 9**) [36].

In 14 BP of 7 corpses, the separation between the SSN and the PN was found to be 2.5-6.4 cm, and the injection of 10 mL of solution around the SSN produced staining of the UT of the BP and its branches (SSN, anterior and posterior divisions - 14 cases, 100%), the middle trunk (MT) (13 cases, 93%), the PN (3 cases; 21.4%) [37]. In the cadaveric study by Sehmbi, the SSN and omohyoid muscle were easily identified and, with nerve injections of 5 mL, nerve staining with contrast dye was seen in 90% of dissections. The UT, MT, and LT were stained in 90%, 80% in 20% of dissections, respectively. The PN was mildly stained in 20% of the dissections [38]. **Figure 9** shows the scan sequence of the SSN at the supraclavicular fossa.
