The posterior approach is generally performed while the patient sits on the operating table with the ipsilateral arm lying by his or her side [25, 27, 38]. To minimize the risk of pneumothorax, the scapula can be elevated from the posterior chest wall by repositioning the ipsilateral hand to the opposite shoulder, thereby increasing the potential distance the needle must travel from the skin to chest wall [36]. A 22-gauge, 3-in. needle is generally used.

The superficial landmarks described in the posterior approach techniques serve to guide the needle to slide into the notch. As discussed in the anatomy section (above), the notch is not a defined structure in 15 % of the population. Furthermore, the potential complication of this approach is pneumothorax as the trajectory of the needle is toward the thoracic cavity.

The superior approach [30, 31] was initially described to permit SSNB performed in patients in the supine position but the sitting position is the preferred position in clinical practice.

The needle entry point for the superior approach has been described as cephalad and lateral to the midpoint of the spine of the scapula [30]. In general, the needle is directed to the lateral half of the floor of the suprascapular fossa because the supraspinatus muscle is attached to the medial half. A 1.5-in. needle is usually sufficient to reach the floor of the scapular fossa. Potential advantages of this approach include ease of access, no reference to the notch, and extremely low risk of pneumothorax [30, 31].

In this approach, the needle entry point is at a landmark known as the “Neviaser portal” [32, 33, 36]. The site can be found by palpating the “soft spot” 1 cm medial to the junction of the clavicle and the scapular spine (Fig. 20.4). The needle is inserted and angled toward the coracoid. When bone contact is made (scapula), the needle is then directed anteriorly until no bone is felt, then retracted marginally, and moved posteriorly until bone again is felt [32]. This positions the needle tip at the coracoid base of the supraspinous fossa [32]. As this places the needle tip in the supraspinous fossa, an adequate block is achieved by flooding the plane with local anesthetic. Initial reports advised using 25 mL of local anesthetic solution with this lateral approach [32]. Subsequently, a modified lateral SSNB approach was published which demonstrated sufficient spread of solution throughout the supraspinous fossa with a volume of 5 mL (see below) [33].

Despite the many number of approaches and techniques published to date, few studies have actually compared them. An old study on pulsed radiofrequency lesioning of the SSN [39] compared 4 commonly used blind techniques [25, 26, 29, 40], in terms of the final position of the needle tip relative to the suprascapular notch with radiographical correlation. They found that the needle tip was usually a significant distance from the notch such that a heat lesion would not affect the SSN in all techniques. When comparing the blind methods, they found that the approach suggested by Granirer [29] offered the best approximation of “needle tip to notch” [39].

Fluoroscopy and CT have been described to locate the suprascapular notch [34, 41]. For the fluoroscopic technique, the patient is placed in the prone position. A C-arm is then used to identify the notch (Fig. 20.5) [41]. The suprascapular notch will be seen superior to the spine of the scapula, medial to the coracoid process, and lateral to the rib margins (Fig. 20.5) [41]. To obtain an optimal image, the C-arm will often need to be obliquely angled away from the side of the proposed block and in the cephalocaudad orientation [41]. Visualization of the suprascapular notch is further improved when the ipsilateral arm is placed above the shoulder (“arm up” position) compared to when the affected arm is placed by the side (“arm down position”) (91 % vs. 47 %; p < 0.0001) [43].

Ultrasound (US) guidance is the most recent imaging technique that has been employed to assist SSNB. Several articles have been published describing this technique [7, 8, 35, 37, 42]. Ultrasound guidance is a relatively new technique, and various methods utilizing sonography have been published [7, 8, 35, 37, 42]. Both anterior and posterior approaches have been described. The anterior approach targets the suprascapular nerve shortly after it branches from the brachial plexus (in the supraclavicular area) underneath the omohyoid muscle [44]. The major limitation of this approach is the proximity to the brachial plexus (median 8 mm; range 4–15 mm). For the purpose of this chapter, the more widely practiced technique of US-guided SSNB will be described.

The ideal site to perform SSNB with ultrasound is at the floor of the suprascapular fossa, between the suprascapular notch and spinoglenoid notch [8] (Fig. 20.2). At this site, the SSN runs along the floor of the suprascapular fossa covered by the fascia of supraspinatus in a natural compartment, which will contain the spread of the local anesthetic or injectate [8]. Applying an ultrasound-guided injection technique approximated the needle tip to the nerve and has been shown to achieve a complete block with a reduced volume of local anesthetic [45]. A small volume (5 mL) of injectate will result in adequate flooding of the nerve [46] with minimal spread to the brachial plexus [33]. Furthermore, this target is independent of the suprascapular notch, which can be absent in some individuals. The risk of pneumothorax is substantially reduced because of the direction of the needle [47].

The ultrasound-guided SSNB may be performed with the patient either in the sitting or prone position. A high-frequency (7–13 Hz) linear ultrasound probe is used. The probe is placed in a coronal plane over the suprascapular fossa (Fig. 20.6). The probe should be placed such that the midpoint of the probe divides a line between the coracoid process and posterior aspect of the acromion (Fig. 20.6). A slight anterior tilt is placed on the probe to improve visualization of the target structures (Fig. 20.6). In this view, the identifiable structures (from superficial to deep) are the trapezius muscle, the supraspinatus muscle, and the suprascapular fossa floor (Fig. 20.6). The suprascapular nerve and artery are commonly seen on the floor running underneath the supraspinatus muscle layer (Fig. 20.6).

SSNB is performed by passing a 22-gauge, 3-in. needle in an in-plane approach from medial to lateral.

One randomized single-blind trial compared the blind approach to SSNB with a CT-guided approach [48]. This study did not find any significant difference between the blind or CT-guided SSNB in terms of pain and disability scores [48]. Both groups showed significant improvement post SSNB [48]. There were no significant adverse effects in either group, and patient satisfaction scores were high [48].

The efficacy of ultrasound-guided SSNB was compared to the landmark-based technique [9]. In this study, patients with chronic nonspecific shoulder pain were randomized with 25 patients in each group. The investigators found that initially both groups improved in terms of pain relief. However, the analgesic effect was better sustained at 1 month in the ultrasound-guided group compared to the control group [9]. Furthermore, while there were no complications in the ultrasound group, the control group recorded 2 cases of arterial puncture and 3 cases of direct nerve injury with neurological deficit [9].

In summary, various approaches have been described for the blockade of SSN. Disadvantages of the approach using the notch as a landmark are the potential absence of the notch in some individuals and the potential risk of pneumothorax. The superior approach may negate these disadvantages. On limited evidence, these studies would suggest ultrasound is useful in approximating the block needle in the vicinity of the SSN and thereby increasing efficacy and reducing complications of SSNB. The majority of recent studies utilizing US-guided SSNB for acute and chronic shoulder pain management may reflect this.