Introduction
The strong, healthy patient suffering from a sports injury or due to any accident or trauma only needs a stabilization procedure. Whereas weak, elderly patients suffering from complications of arthritis and trauma, which requires joint decompression of the joints or arthroplasty, are the ideal candidates for shoulder surgery. Shoulder surgery can be performed safely under general anesthesia, regional block anesthesia, or a combination of the two. The choice of anesthetic technique is greatly influenced by the patient's preferences, the nature and scope of the intended procedure, the surgeon's preferences, and the anesthesiologist's skill. Early postoperative pain following shoulder surgery is a primary cause of concern and distress for patients and orthopedic surgeons. Therefore, adequate pain control is critical for the patient's recovery.
Until the early 1980s, almost all shoulder surgeries were performed under general anesthesia. Interscalene brachial plexus block (ISB) was first proposed as a novel but effective anesthetic technique in the second half of the twentieth century. The brachial plexus supplies the shoulder, arm, and hand; a single injection close to the brachial plexus is sufficient to anesthetize this. Several techniques have been developed for anesthetizing the brachial plexus, ranging from achieving paraesthesia below the shoulder level to using a peripheral nerve stimulator to determine the location of the needle tip. Recently ultrasound (US) imaging allows the identification of the exact location of the brachial plexus and its branches. Considering anatomic landmarks allows for satisfying anesthesia and analgesia for the shoulder.
Current regional anesthetic techniques enable efficient postoperative pain control following shoulder surgery, decreased muscle spasms and earlier movement, fasting physiotherapy treatment in the postoperative period, and ultimately enhance patient recovery and outcome.
What Is the Anatomy of the Shoulder?
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The humerus, scapula, and clavicle are the bones that form the framework for the shoulder girdle. The shoulder girdle comprises the sternoclavicular joint, acromioclavicular joint, glenohumeral joint (shoulder joint), and scapulothoracic articulation.
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The shoulder muscles and ligaments permit and restrict movement while offering active and passive stabilization of the shoulder. The shoulder has three degrees of freedom biomechanically.
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The muscles that act at the shoulder allow free motion of the shoulder joint: flexion (bending movement of the arm), extension (forward raising of the arm), abduction (the direction of the arm away from the midline), adduction (the movement of the limb towards the midline), circumduction (workout of the arm in a circular direction), internal rotation (rotation towards the center of the body), and lateral rotation (away from the body).
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The labrum, capsule, and glenohumeral ligament provide static stability to the shoulder, while the tendon of the biceps muscle, the rotator cuff, and the periscapular muscles provides stability.
What Is the Nerve Supply of the Shoulder?
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The cervical (C3,4) and brachial plexuses (C5,6) provide sensory innervation to the shoulder. The suprascapular (upper trunk of the brachial plexus) and axillary nerves (posterior cord of the brachial plexus) are brachial plexus terminal branches that supply most of the motor and sensory innervation to the joint.
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The lateral pectoral, musculocutaneous, and subscapular nerves provide minor sensory innervation. The suprascapular nerve supplies the supra and infraspinatus muscles, descending posteriorly through the scapular notch.
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This nerve originates from the superior trunk of the brachial plexus, specifically C5 to C6 and possibly C4. It provides cutaneous supply to the posterior shoulder capsule and upper thoracic region, the acromioclavicular and sternoclavicular joints, the subacromial bursa, and the coracoclavicular ligament.
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The axillary nerve is formed by the nerve roots C5 to C6, with a small contribution from C4. It is derived from the brachial plexus's posterior cord. The axillary nerve enters the quadrilateral space from the anteroinferior aspect of the subscapularis muscle and divides into two trunks.
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The anterior trunk supplies the motor innervation of the anterior and middle deltoid muscles. The superior lateral brachial cutaneous nerve provides cutaneous innervation to the skin and the deltoid muscle and branches to the teres minor and posterior deltoid muscles before terminating as the superior lateral brachial cutaneous nerve.
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Local anesthetic blocking of the nerve supply to the synovial membrane, capsule, and articular joints of the shoulder, periosteum, ligaments, and shoulder muscles is often required to suppress shoulder discomfort following surgery successfully.
What Is Interscalene Block?
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This is the standard method and is most often used during shoulder interventions. This method of brachial plexus blockage occurs at the nerve root or trunk level.
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The superior trunk or C5 to C6 nerve roots are numbed with a local anesthetic that may block C7 and C8 nerve roots based on the amount of local anesthetic used.
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The interscalene block is administered as either a single injection or a continuous peripheral nerve block.
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Various techniques have been used to perform interscalene block, including ultrasound guidance and nerve stimulation alone or nerve stimulation combined with ultrasound and paresthesia technique.
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Visualization of the relevant anatomy, needle-tip position, and local anesthetic spread using ultrasound have largely replaced initiated paraesthesia and nerve stimulation as sole methods of localizing nerves.
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Although it can combine peripheral nerve stimulation with or without pressure monitoring with ultrasound, there is no solid evidence that any single or combined approach minimizes the risk of peripheral nerve injury following regional anesthesia.
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Compared to nerve stimulation, ultrasound allows for fewer needle passes, lower volumes of local anesthesia, and better postoperative analgesia.
What Is the Alternative Nerve Block to Interscalene Block?
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Alon Winnie described the percutaneous technique of palpating and injecting a local anesthetic into the groove between the anterior and middle scalene muscles at the level of the cricoid cartilage and the sixth cervical vertebra in 1970.
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The Classic Winnie Approach, known as the anterior approach, is still used frequently, particularly for the single-injection blockade.
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The needle is directed medially, slightly caudally, and slightly posteriorly (towards the contralateral elbow), with the endpoint for injection being paresthesia in the C5 to C6 nerve distribution.
What Are the Lateral Approaches to the Interscalene Block?
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Modification of Winnie’s Technique:
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Winnie's technique was later on modified by Meier et al. to the postoperative problems and to ease the placement of catheters. Meier’s technique uses the same landmarks as Winnie but enters the skin at 30 degrees and two to three centimeters cephalad. The needle is aimed at the clavicle's middle to the lateral third.
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Borgeat and Ekatodramis modified the Winnie method. The nerve stimulation technique is used to identify the endpoint for injection. The needle is inserted approximately 0.5 cm below the cricoid level and directed toward the interscalene groove. These blocks benefit surgical procedures involving the clavicle, the proximal humerus, and the shoulder joint.
What Are the Posterior Approaches to the Interscalene Block?
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Pippa first described the cervical paravertebral block. Later, Boezaart et al. improved on this technique by inserting the needle between the levator scapulae and the trapezius muscle to alleviate neck pain caused by the hand entering the extensor musculature.
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Finally, Van Geffen et al. used ultrasound to perform a single injection interscalene block using the landmarks described by Pippa.
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Antonakakis used ultrasound to place a catheter for a continuous interscalene block. This has the potential to obstruct the brachial plexus. The catheter is better anchored when using the cervical paravertebral approach because it passes through multiple layers of muscle, and vital structures are less likely to be injured.
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The extent to needle progress to reach the site may be painful for the patient, which is the main disadvantage of the cervical paravertebral approach.
What Are the Complications of Interscalene Nerve Block?
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Common complications include - phrenic nerve blockade, Horner's syndrome, recurrent laryngeal nerve blockade, and vasculature puncture (hematoma).
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Sometimes the catheters may become infected, twisted, knotted, or entrapped. The chances of complications can be reduced by knowledge of the anatomical structures and location of the needle and surrounding structures.
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Rarer complications include bleeding into the carotid artery, local anesthetic injected into the intervertebral artery, subdural space, intervertebral foramina, collapsed lung, and nerve injury.
What Are the Alternative Blocks for Shoulder Surgery?
1. Suprascapular Nerve Block: The suprascapular and axillary nerves can be blocked by this technique. When these nerves are blocked individually than in the traditional interscalene block, there may be minimal issues and adverse effects. In addition, in this technique, the phrenic nerve is not blocked, so these blocks can be used in patients who are not candidates for an interscalene block.
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The disadvantage of these blocks is that they do not stop branches near the injected area or the sites not supplied by these nerves. This may result in insufficient analgesia in the surgical field, necessitating intravenous analgesics, local anesthetic infiltration, or general anesthesia.
2. Supraclavicular Block: Provides the most consistent and time-efficient anesthesia of any brachial plexus technique for the entire upper extremity. This technique was limited due to the risk of pneumothorax when using landmark-based techniques.
3. Subacromial Block or Intra-articular Injections: Arthroscopic shoulder procedures such as subacromial decompression and rotator cuff restoration are used. These procedures can cause mild to severe pain. Based on the predicted intensity of the pain, single injections or continuous infusions in the subacromial space are used.
Conclusion:
Over the last century, anesthesia management for shoulder surgery has advanced dramatically. The advancement of techniques and technologies has allowed for a reduction in the anesthetic and surgical impact on patients and a reduction in complications and drug consumption.
