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Shoulder girdle and upper arm


Core Procedures

Surgical Exposures Around the Shoulder Girdle and Upper Arm

  • Approaches to the shoulder girdle

  • Approaches to the shoulder joint

  • Medial extensile exposures

  • Distal (brachial) extensile exposures

While arthroscopy has allowed access to the glenohumeral, sternoclavicular and acromioclavicular joints and to the subacromial–subscapular space, enabling surgeons to undertake a variety of reconstructive procedures, it is not always possible to use a minimally invasive approach for complex and traumatic conditions of the shoulder. In particular, complex reconstruction and revision of the shoulder joint for arthritis and complex fractures of the shoulder girdle require extensive exposures, which are often beyond the routine practice of the surgeon.

Patients with disorders of the shoulder girdle and upper arm present with syndromes that include pain leading to maladaptive muscle activity, and abnormalities of movement due to disordered or pathological biomechanics, often on a background of progressive tissue degeneration. When non-operative treatment has failed to relieve pain and re-establish normal movement, surgical intervention may be considered. Surgery has to address, first, the anatomy of pain and, second, the pathological anatomy of disordered biomechanics: these may not be concordant. The surgical exposure must respect neural pathways and the vascular supply of intact tissues: if possible, surgical exposures should be interneural (i.e. between or respecting neural territories) and intervascular (i.e. between or respecting vascular territories, or angiosomes). Successive layers of the surgical exposure (integument, deep fascia, muscle and joint) have overlapping, but not necessarily identical, innervation and blood supply; most exposures around the shoulder girdle and upper arm are dictated by knowledge of the anatomy of the trunk nerves, the major vessels and the territories that they support.

Surgical surface anatomy

The sternal end of the clavicle is readily palpated at the sternal notch. The anterior border of the clavicle is superficial, while the posterior border of the lateral two-fifths of the bone is often obscured by the attachment of trapezius along its superior surface. The surface anatomy of the superior exposure for the acromioclavicular region and superior compartment of the shoulder (acromion; subacromial space; superior rotator cuff; rotator interval; tendon of the long head of biceps) is shown in Fig. 39.1 .

Fig. 39.1, Surface topography of the right shoulder. The patient is reclining in the deckchair position with the head at the top of the view. Three reliable and readily palpable surface markings are marked with stars: the tip of the coracoid (yellow), the posterior angle of the acromion (white), and the notch between the medial border of the acromion and the posterior aspect of the distal clavicle (which must therefore indicate the posterior margin of the acromioclavicular joint, blue) (1). The lateral border of the coracoacromial ligament is marked (2). The posterior margin of the supraspinatus part of the superior rotator cuff is indicated by a line (3) that is a projection of the line describing the anterior border of the spine of the scapula (which must therefore be the posterior boundary of the supraspinatus fossa). The humeral head is described by a circle marked by palpation between index, middle and thumb. These landmarks allow precise placement of a surgical incision over known pathology of the rotator cuff. This incision respects the position and direction of the lateral supraclavicular nerve while permitting adequate exposure of the superior compartment of the shoulder. The distal extent of the incision respects the potential course of the axillary nerve from posterior to anterior on the deep surface of deltoid.

The surface marking of the axillary nerve is useful and simple ( Fig. 39.2 ); it helps to guide the exposure of the posterior scapula and shoulder joint.

Fig. 39.2, Surface marking of the axillary nerve. The deltoid tuberosity is at the midpoint of the humerus (1), on a line (black) midway between the lateral border of the acromion (2) and the lateral epicondyle (3). With the arm in abduction, the inferior border of the posterior part of deltoid is a straight line (brown) between the medial border of the scapula at the base of the spine of scapula (4) and the deltoid tuberosity (1). The axillary nerve passes directly posteriorly, towards the palpating finger at the midpoint of the posterior border of deltoid (5). It then passes around the humerus at about the midpoint of the muscle (solid orange line). The literature is replete with many estimations of the variability of the distance between the acromion and the axillary nerve deep to deltoid; this rule of thumb is practical and based on the individual's size. Incisions for the exposure of the posterior aspect of the shoulder joint and for the scapula (e.g. for fixation of a scapular fracture, posterior stabilization of the shoulder, and latissimus dorsi tendon transfer, dotted orange line) are medial to this point (5). The posterior cutaneous nerve of the upper arm passes from deep to the posterior border of deltoid at (5) and supplies the skin at (1).

Clinical anatomy

Clavicle, acromioclavicular and sternoclavicular joints

The general anatomical arrangement of the medial and lateral ends of the clavicle is similar. Both the sternoclavicular and acromioclavicular joints and the metaphysial regions of the clavicle associated with them are characterized by asymmetrical, highly variable surfaces that form the articulations; relatively strong intrinsic ligaments that reinforce a thin joint capsule; and complex extrinsic ligaments that create fulcra around which the clavicle rotates on the sternum and the scapula rotates on the distal clavicle. Both are reinforced by a muscular envelope, which also provides stability. The sternal facet of the clavicle is larger than its counterpart on the sternum, which is very variable in shape, size and orientation. The acromial facet of the clavicle is larger than its counterpart, which is also variable in its shape, size and orientation. Both joints have an intra-articular disc, which becomes meniscoid in early adult life, and fimbrial or nearly absent later. This allows the wide range of translation, rotation and gliding at each end of the clavicle that enable the scapula to move in a wide arc around the chest wall, thereby positioning the glenoid fossa in space. The function of subclavius and its relation to the sternoclavicular and acromioclavicular joints is shown in .

The scapula rotates at the acromioclavicular joint, guided by the concentric–eccentric activity of the medial and lateral intrinsic stabilizers of the scapula (rhomboid, middle trapezius and serratus groups, respectively) and its vertical rotators/stabilizers (levator scapulae and upper and lower trapezius, acting with subclavius and pectoralis minor). The important stabilizers of the acromioclavicular joint are the posterior acromioclavicular capsule and the middle fibres of trapezius. The inferior acromioclavicular capsule and coracoacromial ligament may have the greatest density of proprio­ceptors and nociceptors in the shoulder region, suggesting a role for the joint not only as a mechanical fulcrum but also as the afferent field for the scapulothoracic joint, given that the mass of muscle spindles is insufficient for kinaesthesia to be generated simply by the periscapular muscle afferents. Resection of the joint should be carefully considered.

Deltoid

The function of deltoid is complex: the anterior part contributes to flexion–abduction and internal rotation, and the posterior part to extension–abduction and external rotation of the shoulder joint. The middle part of the muscle is morphologically very different from the anterior and posterior parts, which are simple delta-shaped muscles with convergent and slightly spiralling fibres. The middle part is rhomboidal with a complex interdigitation of several columns of muscle fibres, facilitating powerful abduction of the arm by a form of bipolar ratcheting action. Deltoid moves the elbow in space relative to the midline axis; coracobrachialis acts as part of the opposing force-couple. Deltoid and pectoralis major form a continuous muscular envelope around the shoulder girdle and upper arm. There is an interval anteriorly between the two muscles in most people; however, continuity is often seen and the cephalic vein may be absent. The motor innervation of this muscular envelope is derived from the anterior divisions of C3,4 (flexor component) and C5,6 (extensor component). Pectoralis major is innervated via the small-calibre lateral and medial pectoral nerves, suggesting a simple ‘on–off’ mass action, whereas the axillary nerve, which innervates deltoid, is of large calibre, suggesting a greater afferent component (from muscle spindles) and subtlety in the function of the middle part of the muscle. Approaches that incise the middle part of deltoid should be made carefully because the muscle does not possess a true raphe (the so-called ‘deltoid raphe’ is a misnomer) but rather a series of aponeurotic laminae. The muscle fibres can be parted from these laminae to leave the fibres intact and attached proximally ( Figs 39.3 and 39.4 ). The anterior approach to the shoulder joint is described in .

Fig. 39.3, Dissection through deltoid. A , The anterolateral corner of the acromion is marked with a blue star. The anterior leaf of deltoid has been sharply dissected from the anterior internal aponeurosis, which remains attached to the lateral border of the acromion, revealing the underlying parietal layer of the subdeltoid bursa. The anterior leaf can be elevated from the anterior border of the acromion if needed, without detaching this important aponeurotic cable within deltoid. The white arrow shows the most anterior of the several intramuscular aponeuroses of the deltoid, which serves as a guide to the atraumatic dissection of deltoid in this exposure. B , The cauterized acromial artery lies in the slender fat-filled space (white arrow) between the deep surface of deltoid and the coracoacromial ligament, under which the scalpel has been placed. The aponeurotic part of deltoid can be retracted firmly while the less robust anterior leaf must be retracted with care. The acromion is marked with a blue star. C , The beginning of the repair: the anterior leaf is pulled back under the anterior margin of the posterior leaf (white arrow). The remainder of the muscle is sutured in two layers: the deep layer with the parietal bursa, and the superficial epimysial layer, restoring the normal anatomy.

Fig. 39.4, Demonstration of the parts of deltoid: cadaveric dissection. A , The middle and posterior parts of the muscle seen from the side. The posterior part is the more massive and spirals around the lateral aspect of the humerus; it is a powerful external rotator of the arm. B , The middle and anterior parts. The anterior part (A) is overlapped by the middle part (M) at the lateral border of the acromion and the axillary nerve (white arrow), in this case immediately distal to the reflection of the subdeltoid bursa on to the humerus. The posterior part of deltoid (P) is attached to the internal muscular aponeurosis, as well as to the humeral shaft at the tuberosity. C , The middle deltoid inserts on to the posterior aspect of the internal aponeurosis of insertion proximal to the posterior part, forming a common aponeurosis with the anterior part of the muscle. Partial disinsertion of the anterior deltoid from the humerus risks detachment of the all-important middle part.

Dissection around the shoulder

There are a multiplicity of surgical approaches to the shoulder girdle, shoulder joint and upper arm. For simplicity, the principal exposures are grouped into those for the shoulder girdle, those for the shoulder joint and those for the upper arm (which are extensile developments of the exposures of the shoulder joint). All exposures share several common features and follow similar principles. The essential feature of all surgical exposures of the shoulder and upper arm (and for all limb exposures) is the common task of identifying the neurovascular structures, on the basis of which the musculoskeletal structures are exposed.

All surgical exposures of the shoulder girdle, shoulder joint and upper arm are developed in layers. Each layer is characterized by relevant concepts that aid the safe exposure of structures and optimize surgical decision-making and outcomes ( Table 39.1 ). The local exposures (of the proximal humerus and glenoid fossa) can be extended distally (into the upper arm) and medially (for the brachial plexus anteriorly and for exposure of the scapula posteriorly). Extensile exposure of the infracoracoid brachial plexus allows exposure of the axillary nerve when scarring obliterates normal relationships in the axilla (exposure 7 in Table 39.1 ). The anterior exposures can be combined with exposure of the clavicle for an extensile exposure of the entire brachial plexus, associated vessels and forequarter.

TABLE 39.1
Core procedures and pitfalls
Surgical exposure Goal of exposure Essential anatomy Pitfalls
1 Medial (supra-)clavicular Sternoclavicular joint Tendon of sternocleidomastoid Proximity of the great vessels posterior to sternohyoid and sternothyroid
2 Clavicular Shaft of clavicle; retroclavicular and supraclavicular brachial plexus Supraclavicular nerves; retroclavicular brachial plexus and vessels Supraclavicular neuroma; proximity of the subclavian vein to the medial two-fifths of the clavicle
3 Superior Acromioclavicular joint; superior (posterior) rotator cuff Scapular suspension (posterior acromioclavicular joint capsule and ligament) Failure to reconstruct the posterior acromioclavicular joint capsule, leading to acromioclavicular instability
4 Deltoid-splitting:
Anterolateral
Direct lateral		 (3) and proximal humerus Relationship of the axillary nerve to the subdeltoid–subacromial bursa Traction or direct injury of the axillary nerve by retraction of the muscle or incision through the deltoid without clear identification of the nerve; early axillary nerve bifurcation (upper and lower branches)
5 Medial scapular Scapulothoracic exposure Shape and position of the scapula Injury of the dorsal scapular vessels
6 Anterior
deltopectoral		 Proximal humerus and glenoid fossa; anterior rotator cuff Axillary nerve and posterior circumflex vein (and artery) Exposure of the quadrilateral space; haemorrhage from the posterior circumflex humeral vein
7 Anterior extensile (medial) (6) and infracoracoid brachial plexus Relationship of the clavipectoral fascia to the brachial plexus Exposure of and/or traction lesion of the musculocutaneous nerve
8 Anterior deltobrachial extensile (distal):
Anterolateral
Anteromedial		 (6) and anterior shaft of humerus Relationship of the musculocutaneous nerve to coracobrachialis Exposure of and/or traction lesion of the musculocutaneous nerve
9 Posterior Proximal humerus and glenoid fossa (posterior rim) Suprascapular nerve and vessels; axillary nerve Exposure of and/or traction lesion of the nerve to infraspinatus and the axillary nerve
10 Posterior scapular (9) and neck and body of scapula Suprascapular nerve; circumflex scapular artery Exposure of and/or traction lesion of the nerve to infraspinatus and the axillary nerve
11 Posterior deltobrachial extensile (9) and posterior shaft of humerus Relationship of the radial nerve to the medial head of triceps Exposure of the radial nerve
Key: 1–5, approaches to the shoulder girdle; 6 and 9, approaches to the shoulder joint; 7 and 10, medial extensile exposures; 8 and 11, distal (brachial) extensile exposures.

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