The scapula is a unique bone which is ‘suspended’ behind the thorax by it’s muscular attachments; offering great stability & motion to the arm at the same time as large amount of mobility. It is very mobile & able to shift in all directions.
The scapula is well covered and protected by muscles and protected by other bones (proximal humerus, acromioclavicular joint, and clavicle).
The first investigator to publish on the topic of scapula fractures was Desault in 1805. Because of the rarity of this injury, the literature is replete with small case series or retrospective reports with poorly controlled variables.
The scapula is a flat and triangular bone, with a thin translucent body, surrounded by borders that are well developed because of their positions as muscular origins and insertions. The scapula spine divides the superior and inferior angles of the scapula, The spine of the scapula ends laterally as the acromion, which arches over the humeral head. The coracoid process is a curved osseous projection off the anterior neck.
The pear-shaped glenoid fossa lies at the lateral angle, its margin covered by a fibrocartilaginous labrum, which is confluent above with the long head of the biceps tendon at the supraglenoid tubercle. This labrum enhances the depth of the glenoid by 50%. The glenoid fossa is approximately 39 mm in a superior–inferior direction and 29 mm in an anterior–posterior direction in its lower half, which is 20% wider than the top half.
The back of the scapula is divided by the scapula spine into the supraspinatus and infraspinatus fossae, which are origins for their respectively named muscles. Its concave anterior surface serves as a broad origin for the subscapularis muscle. Along with the clavicle, the acromion serves as origin for the deltoid muscle. The trapezius also originates on the acromion and spine anteriorly.
The medial border of the scapula is the site of attachment of the serratus anterior, which functions in scapula protraction, and rhomboid muscles, the function of which is scapula retraction.
The levator scapulae muscle inserts on the superior medial border and is specifically named for its function.
The lateral border of the scapula forms a thick condensation of bone that ends in the neck of the scapula and is the site of origin of the teres major and minor muscles, as well as the insertion for the long head of the triceps on the neck, and part of latissimus dorsi at the inferior angle.
The coracoid process is the origin for the coracoclavicular and coracoacromial ligaments, and for the coracobrachialis and short head of biceps muscles, as well as the insertion for the pectoralis minor.
Just proximal to the coracoid on the superior margin is the scapula incisura, traversed by the transverse scapular ligament, above which lies the suprascapular artery and below which runs the same nerve. The axillary nerve emerges from the quadrilateral space below Teres minor.
The scapula is part of a suspensory mechanism, which attaches the upper extremity to the axial skeleton by the clavicle. The only direct bony link to the axial skeleton is via the clavicle. Thus the upper extremity is ‘suspended’ by a linkage of ligaments and muscles from the clavicle & thorax. Eighteen muscular origins and insertions on the scapula aid in its function to provide a stable base from which glenohumeral mobility can occur.
The SSSC is a bony–soft tissue ring made up by the glenoid, coracoid, and acromion processes, as well as the distal clavicle, the acromioclavicular joint, and coracoclavicular ligaments. The superior strut is the middle clavicle, and the inferior strut is the lateral scapula. Lesions to two of these structures allow for significant displacement at the individual site and the entire SSSC itself.
Motion of the humerus results from simultaneous motion at the sternoclavicular, acromioclavicular, scapulothoracic, and glenohumeral articulations. This concert of muscular forces constrain the scapula body on the thorax at approximately 35° anteverted to the coronal plane, and position the glenoid fulcrum so that the rotator cuff can function as a dynamic stabilizer of the proximal humerus. This force vector of the rotator cuff, compressing the humeral head against the glenoid, counteracts the shear forces on the glenohumeral joint imparted by the large deltoid muscle.
These forces are formidable even during ordinary activities; when the arm is held in 90° of abduction, the joint reactive force is 90% of body weight.
The unrestrained configuration of the shoulder and associated joints results in exceptional axial and rotational mobility. At less than 90 degrees of abduction the deltoid muscle force creates a shear vector in the glenoid fossa. This force is neutralized by the rotator cuff muscle, which generates a stabilizing compressive force across the glenoid. If there is an alteration in the glenoid axis caused by a displaced fracture displacement, the lever arm of the rotator cuff muscle is distorted, converting the compressive force into a shear or sliding force. Then forces are magnified at 45 degrees or more of glenoid fracture tilt.
In addition, a fracture of the scapular spine may cause rotator cuff dysfunction because the entire scapula collapses with hortening, with resultant shortening of the rotator cuff lever arm.
Scapula fractures are relatively uncommon. Approximately 50% of scapula fractures involve the body and spine.
Glenoid neck constitute about 25%
fractures of the glenoid cavity (glenoid rim and fossa) make up approximately 10% of scapula fractures.
The acromial and coracoid processes account for 8% and 7%, respectively.
Mechanism of injury & Associated injuries
The typical mechanism of injury is major trauma, such as a pedestrian RTA.
Scapula fractures have a high association with concomitant injuries. Research shows that 80-95% of scapula fractures have associated injuries. The associated injuries may be multiple and/or life-threatening. As a result, diagnosis and treatment of scapular injuries may be delayed or suboptimal. Long-term functional impairment may occur. As more focus is placed on the proper management of scapular injuries, functional outcomes should improve.
- Rib fractures - 25-45%
- Pulmonary injury - 15-55%
- Humeral fractures - 12%
- (5-10% brachial plexus injury)
- Skull fractures - 25%
- CNS deficits 5%
- Major vascular injury - 11%
- Splenic injury - 8%
Due to the often associated life threatening and more clinically urgent injuries scapula fractures are often diagnosed later, once the patient is stable. It may be noted on the ATLS chest radiographs. Essentially, a high index of suspicion of scapula fractures should be applied to all major chest trauma.
AP of Shoulder: it is essential to rule out articular involvement with a high quality AP view in which there is no overlap of the humerus over the glenoid;ideally, the view should be purely tangential to the glenoid; 45 deg cephalic tilt allows evaluation of coracoid fracture
Apical Oblique View: is useful to assess the lateral displacement of the fractures.
CT Scanning allows more accurate assesment of articular step off, as well as displacement and angulation of glenoid neck. CT scanning is particulary helpful in evaluation of intra articular glenoid fracture.
The classifications of Ada and Miller, as well as that of Hardegger et al, are comprehensive and anatomically defined. The former is based on a retrospective experience of 116 scapulae, for which nomenclature was developed for fractures of each scapula process (acromion and coracoid), three types of neck fractures, as well as the glenoid and body. The Hardegger classification is similar but names two types of glenoid and two types of neck fractures. This classification is based on the experience of 37 operatively treated fractures.
Historically, scapula fractures have been treated with closed means. One of the earliest descriptions of treating scapula fractures was published in 1805 in Desault’s treatise on fractures. More recently, indications for operative management have been described. Hardegger et al reported that if significant displacement occurs, conservative treatment alone cannot restore congruence, and stiffness and pain may result, thereby indicating open reduction and stabilization.
The management of scapula fractures has historically been nonoperative, perhaps in part because of the paucity of information regarding outcomes, combined with a relative unfamiliarity in treating these injuries. Treatment has emphasized symptom relief and early motion to prevent long-term stiffness. After motion is restored in the first four to 6 weeks, therapy is directed at rehabilitating the rotator cuff and strengthening parascapular musculature. Because more than 90% of scapula fractures are minimally displaced, this noninvasive approach is effective for most.
No well-documented role for closed reduction techniques or effective orthotic management exists.
A number of investigators have accumulated data about injury characteristics that may portend a poor prognosis, shedding light on potential indications for surgery. These recommendations fall more in line with contemporary management principles for other periarticular fractures.
Ada & Miller did a follow-up of 16 such patients treated nonoperatively, of whom 50% had pain, 40% had exertional weakness, and 20% had decreased motion at a minimum of 15 months' follow-up. A group of eight patients in this same study were treated operatively, and all achieved a painless range of motion.
Nordqvist and Petersson analyzed 68 patients with a mean 14-year follow-up and found that 50% of patients with residual deformity have shoulder symptoms.
Displaced articular fractures of the glenoid, for example, are the clearest indication for surgery. If humeral head subluxation, early arthrosis, and a poor outcome are to be prevented, open reduction internal fixation (ORIF) should be performed.
Fractures of the scapula neck should be treated operatively if displacement or angulation renders functional imbalance to the parascapular musculature. Ada and Miller have recommended ORIF if the glenoid is medially displaced more than 9 mm or there is more than 40° of angular displacement.
Double disruption of the superior shoulder suspensory complex (SSSC) is an entity that has gained distinct attention since Goss discussed its significance in relation to scapula fractures. The significance of this entity was recognized much earlier, however, by a number of investigators noting that the weight of the arm and the muscle forces acting on the humerus result in a typical pattern of displacement inferior and anteromedial. Therefore, treatment recommendations have consisted of stabilizing one or both lesions to restore integrity to the SSSC, thereby preserving its function of maintaining a stable relationship between the upper extremity and axial skeleton, and providing a firm attachment for the many soft tissues that enable shoulder function.
Although there was previously an enthusiasm for fixing the clavicle fracture in all double disruption fractures, it is now preferred to manage each fracture as it's own entity, being aware of the SSSC effects. Therefore, a completely undisplaced fracture does not require fixation, but displaced SSSC, with shortening does require reduction and fixation.
a 3D model, one can plan the fixation on a life-size exact reproduction of the fracture and bone. This means that a smaller incision and less disruptive approach can be taken to the fracture and one can plan the direction of fixation to avoid the suprascapular and axillary nerves (orange). The blue arrows depict the screw and buttress plate directions to reduce the glenoid and lateral scapula border.
- Desault PJ. A Treatise on Fractures, Luxations, and Affections of the Bones. Philadelphia: Fry and Kanmerer; 1805. p. 57-67
- Ada JR, Miller MD. Scapular fractures: Analysis of 113 cases. Clin Orthop 1991;269:174-80.
- Hardegger FH, Simpson LA, Weber BG. The operative treatment of scapular fractures. J Bone Joint Surg Br 1984;66:725-31.
- Nordqvist A, Petersson C. Fracture of the body, neck or spine of the scapula: A long-term follow-up study. Clin Orthop 1992;283:139-44.