The Pectoral Girdle | Anatomy & Physiology
This consists of two bones, the scapula and clavicle (Figure ). where it forms the bony tip of the shoulder and joins with the lateral end of the clavicle. Scapula: More commonly known as the shoulder blade, the scapula is a flat triangular bone located in the upper back. It connects The meeting of the scapula and clavicle forms it. The No BS Guide to Good, Healthy Carbs. The bones of the shoulder consist of the humerus (upper arm bone), the scapula (shoulder blade), and the clavicle (collar bone). The shoulder's relationship with.
At the shoulder, the coracoid process is located inferior to the lateral end of the clavicle. It is anchored to the clavicle by a strong ligament, and serves as the attachment site for muscles of the anterior chest and arm.
Scapula - Wikipedia
On the posterior aspect, the spine of the scapula is a long and prominent ridge that runs across its upper portion. Extending laterally from the spine is a flattened and expanded region called the acromion or acromial process. The acromion forms the bony tip of the superior shoulder region and articulates with the lateral end of the clavicle, forming the acromioclavicular joint see Figure 8. When visualized from above, the clavicle, acromion, and spine of the scapula form a V-shaped bony line that provides for the attachment of neck and back muscles that act on the shoulder, as well as muscles that pass across the shoulder joint to act on the arm.
Two of these are found on the posterior scapula, above and below the scapular spine. Superior to the spine is the narrow supraspinous fossa, and inferior to the spine is the broad infraspinous fossa.
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The anterior deep surface of the scapula forms the broad subscapular fossa. All of these fossae provide large surface areas for the attachment of muscles that cross the shoulder joint to act on the humerus. The acromioclavicular joint transmits forces from the upper limb to the clavicle.
The ligaments around this joint are relatively weak. A hard fall onto the elbow or outstretched hand can stretch or tear the acromioclavicular ligaments, resulting in a moderate injury to the joint. However, the primary support for the acromioclavicular joint comes from a very strong ligament called the coracoclavicular ligament see Figure 8.Fractured Clavicle (Shoulder) / Douglas Cutter, MD, CAQSM
This connective tissue band anchors the coracoid process of the scapula to the inferior surface of the acromial end of the clavicle and thus provides important indirect support for the acromioclavicular joint. Following a strong blow to the lateral shoulder, such as when a hockey player is driven into the boards, a complete dislocation of the acromioclavicular joint can result.
In this case, the acromion is thrust under the acromial end of the clavicle, resulting in ruptures of both the acromioclavicular and coracoclavicular ligaments. The scapula then separates from the clavicle, with the weight of the upper limb pulling the shoulder downward. Chapter Review The pectoral girdle, consisting of the clavicle and the scapula, attaches each upper limb to the axial skeleton.
The clavicle is an anterior bone whose sternal end articulates with the manubrium of the sternum at the sternoclavicular joint. The sternal end is also anchored to the first rib by the costoclavicular ligament. The acromial end of the clavicle articulates with the acromion of the scapula at the acromioclavicular joint. This end is also anchored to the coracoid process of the scapula by the coracoclavicular ligament, which provides indirect support for the acromioclavicular joint.
The clavicle supports the scapula, transmits the weight and forces from the upper limb to the body trunk, and protects the underlying nerves and blood vessels. The scapula lies on the posterior aspect of the pectoral girdle. It mediates the attachment of the upper limb to the clavicle, and contributes to the formation of the glenohumeral shoulder joint.
This triangular bone has three sides called the medial, lateral, and superior borders. The suprascapular notch is located on the superior border. The infraserratus bursa is found under the serratus anterior, overlying the posterolateral chest wall and is on average cm [ 22 ]. The 4 minor bursae are not consistently found and are often a result of abnormal scapulothoracic articulation [ 27 ]. These are typically found along the inferior angle of the spine, at the superomedial border of the scapula, either above or below the serratus anterior, or deep to the trapezius muscle at the medial base of the scapular spine [ 29 ].
The bursa of the superomedial border and inferior angle are frequently pathologic and responsible for symptom generation [ 2530 ].
One superficial bursa has also been described to be located between the latissimus dorsi and the inferomedial angle of the scapula approximately cm in size [ 22 ]. One intermediate level bursa, called the scaphotrapezial trapezoid bursa, has been described to be located between the superomedial scapula and the trapezius muscles in the intermediate level, approximately cm in size. Abnormal Scapulothoracic Articulation Abnormal motion of the scapula on the underlying thorax is the basis for the development of the snapping scapula syndrome [ 23 ].
Patients with scapulothoracic bursitis often present without a history of trauma or injury to the shoulder [ 31 ], although they may report a history of repetitive overhead activity such as swimming or pitching, gymnastics, or weightlifting [ 32 ]. Patients may also report neck pain or debilitating shoulder pain with possible numbness or tingling in the extremity [ 31 ], whereas a subset of patients will report a painless sensation of snapping with shoulder motion, other patients will report activity-related pain directly associated with snapping or crepitus [ 2733 ].
The Luschka Tubercle and excessive anterior angulation of the superior angle of the scapula are examples of skeletal abnormalities.
The Luschka Tubercle is a hook-shaped extension of the superomedial border of the scapula that may cause irregular scapulothoracic articulation [ 39 ].
Changes in the thorax due to kyphosis can also alter the scapulothoracic articulation [ 26 ]. The presence of an osteochondroma, a benign cartilage tumor [ 40 ], can also cause scapulothoracic crepitus [ 31 ]. An osteochondroma is the most common benign tumor of the scapula [ 41 ], with a reported incidence of 3 to 4. These lesions usually arise over the ventral surface of the bone. Chondrosarcoma can also arise in the scapula, and can affect scapulothoracic articulation in rare cases [ 45 ].
Calcific spurring of the superomedial angle of the scapula from chronic trauma or avulsion of the levator scapulae muscle has also been implicated in cases of scapulothoracic bursitis [ 46 ].
While rare, abnormal scapula motion leading to scapulothoracic bursitis can also result from nerve injury, muscle overuse, and muscle imbalance leading to impaired control of scapular motion [ 4647 ]. Impaired scapular motion, otherwise known as scapular dyskinesis [ 48 ], has been identified in patients with glenohumeral joint pathologies, including shoulder instability [ 49 ] and rotator cuff pathology [ 5051 ].
Muscular atrophy of the serratus anterior and subscapularis, as a result of long thoracic nerve palsy and glenohumeral fusion, respectively, has been reported as causes of scapulothoracic dyskinesis [ 52 ]. In a series of patients treated with resection of the 1st rib for thoracic outlet syndrome, 15 went on to develop snapping scapula syndrome due to postoperative alteration of the biomechanics of the scapulothoracic joint [ 52 ].
A recent cadaveric study has characterized a superomedial bare area on the costal surface of the scapula between the serratus anterior insertion and the origin of the subscapularis muscle [ 53 ]. This crescent-shaped area, with an average dimension of This area of the scapula may potentially lead to scapulothoracic impingement and symptomatic bursitis or crepitus.
Diagnostic Studies After a thorough history and physical examination, patients presenting with complaints concerning snapping scapula syndrome often undergo a variety of imaging studies. Disorders of the scapula can be evaluated with plain radiography Figure 4computed tomography CT Figure 5magnetic resonance imaging MRIand ultrasonography [ 54 ].
Both MRI and ultrasound are more useful for evaluating bursitis, while radiographs and CT are helpful in the evaluation of bony abnormalities. Plain radiographs in the anterior-posterior, trans-scapular scapular Yand axillary projections can characterize the anatomical features of the scapula and the adjacent thoracic cage [ 39 ].
CT is certainly the best study for characterizing the bony morphology of the scapula. Three-dimensional CT is especially helpful in characterizing subtle bony irregularities that are often responsibly for scapulothoracic irritation and ultimately, snapping scapula syndrome [ 54 ]. MRI is the study of choice for characterizing soft tissue pathology [ 5556 ].
Scapulothoracic Anatomy and Snapping Scapula Syndrome
This study is especially helpful in evaluation of inflamed bursae as well as in the evaluation of potential soft tissue tumors. Though less commonly used, ultrasonography may be a cost-effective alternative, differentiating scapulothoracic bursitis from other causes of scapulothoracic pathology such as elastofibroma dorsi [ 3457 ]. Radiographs including a AP, b axillary, and c scapular Y of the left shoulder. CT images with 3D reconstruction demonstrating a ventral surface and b dorsal surface of scapula.
Treatment Nonoperative management of symptoms is the first-line of treatment for patients with scapulothoracic bursitis [ 232627 ]. Commonly used modalities include activity modification, analgesics, nonsteroidal anti-inflammatories, and physical therapy for strengthening of the periscapular musculature and rotator cuff and improvement of scapular positioning.
Nonoperative management should be attempted for at least six months to one year before escalating to surgical management [ 58 ]. Patients with persistent pain and disability with impinging osseous lesions or failure of nonoperative treatment can be considered for surgical bursectomy and or superomedial angle resection.
Some authors have reported that patients with symptoms at the inferomedial and superomedial borders of the scapula may be better surgical candidates [ 3 ]. Examination after injection of local anesthetic may also help to define which patients will ultimately benefit from surgery, although these bursae can be difficult to accurately inject [ 59 — 61 ].
Both open and arthroscopic approaches to superomedial angle resection and bursectomy have been described [ 2429303536476263 ]. Bursae to be addressed include those adjacent to the superomedial and inferomedial angles.
Arthroscopic-assisted and all-arthroscopic Figures 6 and 7 technique [ 36263 ] for snapping scapula syndrome rely on similar principles as the open procedures, and a comprehensive understanding of the anatomy described above is critical to avoid iatrogenic damage to the periscapular neurovascular structures or underlying chest wall.
Arthroscopic images aband c demonstrating arthroscopic bursectomy for snapping scapula syndrome with the use of an arthroscopic shaver asterisks represent areas of inflamed bursa. Arthroscopic image demonstrating inflamed bursa prior to arthroscopic bursectomy.
Summary The scapulothoracic articulation is a complex anatomical structure that plays a substantial role in the overall shoulder function.
The osseous, ligamentous, and muscular periscapular relationships are intricate, and the underlying neurovascular anatomy can be variable. While scapulothoracic pathology is uncommon, a thorough appreciation of the anatomy, including the various muscular relationships and bursal planes, is critical for the evaluation of patients presenting with scapulothoracic disorders.
Snapping scapula syndrome is caused by either osseous lesions or scapulothoracic bursitis, and appropriate recognition and treatment of these disorders are dependent on a solid foundation in periscapular anatomy. Disclosure No sources of support in the forms of grants, equipment, or other items were received for this study.
Conclusions There is a considerable amount of variability in where the IASs are located, but most commonly, they correspond to the level of the upper body of T9.
Introduction Musculoskeletal practitioners commonly use contiguous bony landmarks to locate spinal levels. In spite of this inconsistency, no studies have attempted to determine as their primary goal which vertebral segment truly corresponds to the IAS. Based on these findings, the authors opined that the location of thoracic landmarks could be accurately determined using surface palpation of scapular position as a reference point.
On the other hand, several related studies have investigated the reliability of manual and physical therapists in locating spinal levels by palpation of spinous processes. Locating the precise spinal level by palpation is especially important to practitioners who intend to apply a specific therapy to a specific segment.
Chiropractors, as well, are often interested in locating spinal levels by palpation and would benefit if a valid and reliable analytic method were available. The purpose of the current study was to determine which spinal segment corresponds to the level of the IAS by means of measurements taken on retrospectively analyzed A-P full-spine radiographs that were taken with patients in an upright neutral posture.
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Methods Fifty-three radiographs were sequentially selected from the educational radiographic archives of a chiropractic college, consisting of several hundred films.