María Luz Padilla del Rey MD, FIPP, CIPS, EDPM1, Eleni Episkopou MD, CIPS2, and Agnes R. Stogicza MD, FIPP, CIPS, ARSA-PMUC3 1 University Hospital Complex of Cartagena, Region of Murcia, Spain Shoulder pain is the third most common musculoskeletal complaint [1], with a lifetime prevalence of 8.4 per 100 people over the age of 18 [2]. It is a frequent complaint among elderly patients, which leads to a greater functional disability and decrease in their quality of life [3]. The causes of chronic shoulder pain are variable, ranging from rotator cuff pathology, osteoarthritis, and myofascial pain to peripheral nerve entrapment. The suprascapular nerve (SSN) is responsible for the sensory innervation of the posterosuperior quadrant of the glenohumeral joint (GHJ) capsule and part of the acromioclavicular joint (ACJ), and it also innervates the supraspinatus and infraspinatus muscles [4, 5]. According to Lauremonie et al., areas with the highest nociceptive density (subacromial bursa, long head of the biceps tendon and coracoacromial, coracoclavicular and transverse humeral ligaments), known as anatomic pain generators, are innervated by the same nerves (SSN, axillary nerve, and lateral pectoral nerve) that innervate anatomic regions at particularly high risk of injury, such as the rotator cuff and the GHJ. These nerves, following the proposed “nerve bridge” principle, may transmit stimulation from the injured tissue to areas rich in nociceptors creating a “nociceptor sensitization” with secondary pain sites away from the primary injured structure [6]. This could explain why some authors advocate for treating pain generators, their parent nerves (whose distribution shows variations) [5], and the injured trigger areas. The SSN, a mixed nerve that includes sensory and motor fibers, arises from ventral rami of the upper trunk of the brachial plexus (C5, C6 and, sporadically, C4 roots). SSN variable origin has been found from the ventral rami of the C5 and C6 (76.0%), C4, C5, and C6 (18%) and C5 (6%) [7]. The SSN courses through narrow osseoligamentous structures, which renders it susceptible to compression and traction injuries. It runs laterally through the posterior cervical triangle and backward to the clavicle, under the inferior belly of the omohyoid muscle and deep to the trapezius muscle reaching the superior border of the scapula at the suprascapular notch underneath the superior transverse scapular ligament (STSL) [8]. The suprascapular notch, also known as the supraspinatus notch or incisura scapulae, is a bony depression that represents the most common site of compression of the suprascapular nerve. Several anatomic variations of the notch, classified into six morphotypes [9], have been described that range from a simple bony tunnel to a wide and soft bony depression (Figure 44.1). Figure 44.1 Six classified basic types of the suprascapular notch. It is important to note that an independent ligament has recently been described that lays on the anterior side of the suprascapular notch, below the STSL, named the anterior coracoscapular ligament (ACSL). The presence of the ACSL varies from 18.8% to 60% and, depending on its position with respect to the SSN, it may predispose to or protect against SSN compression [10]. As the SSN passes through the suprascapular notch, roughly 3 cm medially to the supraglenoid tubercle, it courses posteriorly and laterally in the supraspinatus fossa along the inferior surface of the supraspinatus muscle straight to the scapular spine [11]. At this point, it passes through the spinoglenoid notch (depression at the lateral base of the scapular spine that occurs 1.8 to 2.1 cm medial to the glenoid rim) under the spinoglenoid ligament (or inferior transverse scapular ligament). The spinoglenoid ligament connects the scapular spine and the posterior shoulder capsule bridging over the scapular neck. The suprascapular artery (branch of the subclavian artery) and vein generally pass over the STSL; however, variations have been observed, some of them being one of the possible causes of SSN entrapment. A cadaveric study published in 2015 offers a classification of topography of the SSN, artery, and vein at the suprascapular notch region distinguishing four types of arrangements: The nerve along with the vessels are in direct contact with the bony surface as they travel in the supraspinous fossa toward the spinoglenoid notch, then on to the infraspinous fossa. Classically, the SSN innervates 70% of the shoulder girdle which consists of three bones (scapula, clavicle, and humerus), three synovial joints (glenohumeral, acromioclavicular and sternoclavicular), and two gliding mechanisms (scapulothoracic and subacromial) all acting as a single biomechanical unit. The articular branch, which arises from the LT, is sensory and supplies the coracoclavicular and coracoacromial ligaments, the acromioclavicular joint, the glenohumeral joint (posterior and superior aspects), and the subacromial bursa [13]. Some cadaveric studies have found the presence of a cutaneous branch of the SSN in 14.7% of upper limbs, presumably contained within the axillary nerve and responsible for the cutaneous innervation of proximal-lateral one-third of the arm [14]. The SSN bifurcates to medial (MT) and lateral (LT) trunks at the suprascapular notch. The MT provides motor innervation to the anterior region of supraspinatus muscle, whereas the LT provides motor innervation to the posterior region of the supraspinatus muscle as well as the superior, middle and inferior regions of the infraspinatus muscle. The main trunk of the nerve terminates in motor branches to the infraspinatus muscle. Diagnostic injection may be performed at any level of its path, but proximal to the pathology of the nerve. Needles: 22–25G 2–3.5 inch. Drugs: 1–3 ml of local anesthetic ± steroid.
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Complications of Suprascapular Nerve Procedures
2 Metropolitan Hospital Clinic, Athens, Greece
3 Saint Magdolna Private Hospital, Budapest, Hungary
Introduction
Anatomy
Origin
Path
Neurovascular Relations
Innervation
Sensory Innervation
Motor Innervation
Indications
Indications for Nerve Ablation and Pulsed RF
Chronic Shoulder Pain
Contraindications
Technique
Diagnostic Injection
Radiofrequency Ablation and Cryoablation
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