The scapula is the bridge between the axial skeleton and arm via the glenohumeral and acromioclavicular (AC) joints and the sternoclavicular articulation. The scapula functions as a semistable, fairly mobile platform for the humeral head and upper extremity to work against. Finally, it serves as a point of attachment for various soft tissue structures (musculotendinous and ligamentous) ( Fig. 13.1 ).
Scapular fractures are usually the result of high-energy trauma (most often direct but occasionally indirect). Avulsion and stress or fatigue fractures can also occur. Numerous fracture patterns have been described.
Fractures of the scapula account for 2% of all fractures, 5% of shoulder fractures, and 3% of injuries to the shoulder girdle ( Box 13.1 ). Such fractures are relatively infrequent for two reasons: (1) the scapula lies over the posterior chest wall and is protected by the rib cage and the thoracic cavity anteriorly and a thick layer of soft tissues posteriorly, and (2) the relative mobility of the scapula allows considerable dissipation of traumatic forces. With the increased, broad use of computed tomography (CT) in trauma patient evaluation, diagnosis of scapula fractures is increasing, most notably in the geriatric population. To this point, in trauma patients who receive chest radiographs and chest CT, 60% of scapula fractures are diagnosed by CT only. The vast majority of scapula fractures (>90%) are insignificantly displaced, primarily because of the strong support provided by the surrounding soft tissues, thus making nonoperative management the treatment of choice. Although largely nonoperative, there has been a growing body of literature discussing scapula fracture imaging, classification, three-dimensional (3D) mapping, and surgical management. In addition, the growing prevalence of reverse shoulder arthroplasty is accompanied by an increase in acromial stress fractures.
1% of all fractures
≥90% insignificantly displaced
Body and spine: ∼52%
Glenoid fossa: ∼29%
Glenoid neck: ∼8%
Acromial/coracoid process: ∼11%
Incidence of associated injuries is 80%–90%, including major, multiple, and life-threatening injuries
Because of the significant trauma often involved, patients sustaining a scapula fracture have an 80% to 95% incidence of associated osseous and soft tissue injuries (local and distant) that may be major, multiple, and even life threatening. These patients need to be carefully evaluated when they arrive in the emergency department, and appropriate supportive care must be rendered. As a result, scapula fractures are often diagnosed late, have a delay in definitive treatment, or both. Such delay can compromise the patient’s final functional result. In addition, if the associated injuries involve the shoulder complex, the patient’s scapula fracture recovery may be even further compromised. Herrera et al. reported on 22 patients with displaced scapula fractures managed operatively 21 to 57 days (mean delay, 30 days) after the acute event. Although technically challenging, they found that the surgery could be safely conducted with good outcomes.
A thorough knowledge regarding the local bony, soft tissue, and neurovascular anatomy is necessary when evaluating and treating scapula fractures, particularly if operative management is required. The scapula is composed of the scapular body and its four processes: the glenoid, acromial, coracoid, and spinous processes. The glenoid process extends laterally from the scapular body and is composed of the glenoid neck and glenoid cavity which in turn is composed of the glenoid rim and glenoid fossa. The coracoid process extends superiorly from the glenoid process and then anteriorly and laterally. The acromial process extends laterally from the spinous process and eventually anteriorly. The spinous process protrudes posteriorly from the scapular body and extends from the medial scapular border (forming the spinomedial angle) to its junction with the glenoid and acromial processes at the spinoglenoid notch (through which the suprascapular artery and nerve pass from the supraspinatus fossa to infraspinatus fossa). The superior scapular border meets the medial scapular border at the superior angle, and the medial scapular border meets the lateral scapular border at the inferior angle. The scapula takes part in three articulations: the glenohumeral joint, AC joint, and scapulothoracic articulation. The scapula serves as a point of attachment for numerous ligaments: the glenohumeral ligaments, coracoacromial (CA) ligament, AC ligaments, coracohumeral ligament, and coracoclavicular ligament (with its trapezoid and conoid portions). The scapula also serves at a point of attachment for 18 musculotendinous structures. The subscapularis muscle lies over the anterior scapular surface, and the serratus anterior inserts along the inferior angle of the scapula. The supraspinatus and infraspinatus muscles lie posteriorly within the supraspinatus and infraspinatus fossae, respectively. More superficially, the trapezius muscle inserts along the scapular spine, acromion, and clavicle, whereas the deltoid muscle originates from the scapular spine, acromial process, and distal end of the clavicle. The levator scapulae and rhomboids attach along the medial scapular border, while the teres minor and teres major muscles attach along the lateral border. Tendons of the pectoralis minor, short head of the biceps, and coracobrachialis attach on the coracoid process; the latter two form the conjoined tendon. The long head of the biceps originates at the superior glenoid margin, while the long head of the triceps attaches along the inferior glenoid margin. A small slip of latissimus dorsi muscle variably originates at the inferior angle of the scapula, while the omohyoid attaches along the superior scapular border. These muscles are served by nerves arising from the brachial plexus. The brachial plexus and axillary vessels pass medial to the coracoid process and deep to the pectoralis minor tendon. The suprascapular notch is found along the superior scapular border just medial to the base of the coracoid process and is bridged by the transverse scapular ligament. The suprascapular nerve courses through the notch beneath the ligament, while the suprascapular artery passes above the ligament. The scapula is served by two sets of vessels that anastomose with each other. The glenoid process is served by the circumflex scapular artery, which courses inferiorly to superiorly, and the suprascapular artery, which courses superiorly to inferiorly, anastomosing over the posterior glenoid process. The scapular body is served by the thoracodorsal artery, which courses inferiorly to superiorly, and the dorsal scapular artery, which courses superiorly to inferiorly, anastomosing along the medial border of the scapula.
Most shoulder functions involve complex glenohumeral and scapulothoracic movements that occur in a precise sequence. The scapula is capable of six basic movements over the posterior chest wall: elevation, depression, upward rotation, downward rotation, protraction, and retraction. Combinations of these movements allow the positioning of the upper extremity optimally in space. Trauma to the scapular region resulting in fracture nonunion, fracture malunion, soft tissue scarring, muscle damage, and nerve injury can have adverse mechanical and functional consequences.
Location of fractures of the scapula
Quite a number of scapula fracture patterns occur. Typically, they are classified by anatomic area: body and spine, glenoid neck, glenoid cavity, acromial process, and coracoid process. The etiology of scapula fracture by location is most recently described by Tucek et al., with the largest cohort to date based on CT imaging. Older reports have a smaller number of patients or are largely based on radiographs. Most scapula fractures involve the body (∼52%).
Fractures of the glenoid cavity (the glenoid rim and glenoid fossa) were previously reported at 10%, but more recent studies report an incidence closer to 29%. Fractures of the scapular processes occur in 11% of scapular fractures. Least common are fractures of the glenoid neck (5%–8%) ( Fig. 13.2 ).
A group of injuries termed double disruptions of the superior shoulder suspensory complex (SSSC) have also been described and often involve fractures of the coracoid, acromial, and glenoid processes.
New classification scheme
In 2013 and 2014, the Arbeitsgemeinschaft für Osteosynthesefragen (AO) Foundation and the Orthopaedic Trauma Association put forth a new scapular fracture classification system focusing on articular segment and scapular body involvement, respectively. , The goal was to describe these injuries in a comprehensive, reliable, reproducible, and accurate manner and to provide a base for further clinical studies. Other variables, such as displacement, were acknowledged as being of equal importance in determining appropriate treatment and predicting outcomes. Fractures of the articular segment are given the designation “F,” which includes three groups: F0, F1, and F2. The F1 group has three subgroups, each with three categories, and the F2 group has two subgroups ( Fig. 13.3 ). Fractures of the scapular body are given the designation “B,” and the involved borders are assigned letters as follows: l, lateral border; m, medial border; and s, superior border ( Fig. 13.4 ). The junction between the articular segment and scapular body is defined by a line parallel to the plane of the glenoid cavity (superior to inferior rim), beginning at the lateral border of the scapular notch and exiting along the lateral scapular margin. Fractures of the acromial and coracoid processes are given the designation “P” and are considered independent systems. This updated classification system has significantly higher intraobserver and interobserver reliability compared with the historical Euler and Ideberg classification. In addition, some fracture patterns cannot be classified by the Euler and Ideberg classification systems. Studies are still needed to determine how these classification schemes relate to management and prognosis.
The physician’s attention is initially drawn to the scapular region by the patient’s complaints of pain. Characteristically, the arm is held adducted, and all movement is resisted, particularly abduction, which is especially painful. Local tenderness is typical. Abnormal physical findings in the area include swelling and crepitus. In rare cases, notable swelling due to the fracture can push the scapula dorsally as the subscapularis swells and the supraspinatous and infraspinatous fossas are visibly full divided by the spine, often referred to as the Comolli sign, as described by him in the 1930s. , Ecchymosis is less than what might be expected given the degree of bony injury. However, the specific diagnosis of a scapula fracture is ultimately radiographic. These injuries are often initially missed or detected incidentally on the patient’s admission chest radiograph or CT scan ( Fig. 13.5 ). It cannot be overemphasized that scapula fractures are typically accompanied by associated injuries that often require more urgent management.
Associated injuries and complications
The most significant complications associated with scapula fractures are those that result from accompanying injuries to adjacent and distant osseous and soft tissue structures. , Because of the severe traumatic forces involved, these patients have an average of 3.9 additional injuries, with the most common sites being the ipsilateral shoulder girdle, upper extremity, lung, and chest wall. Of these patients, 64% have accompanying rib fractures, 15% to 40% have fractures of the clavicle, 15% to 55% have pulmonary injuries (e.g., hemopneumothorax, pulmonary contusion), 12% have humeral fractures, and 5% to 10% sustain injuries to the brachial plexus and peripheral nerves. , Fractures of the skull are found in approximately 25% of patients, cerebral contusions in 10% to 40%, central neurologic deficits in 5%, tibia and fibula fractures in 11%, major vascular injuries in 11%, and a mortality rate of 2%. Tatro et al. describe a complication rate of 33%; pneumonia 19%, acute respiratory distress syndrome 7%, and deep vein thrombosis/thrombophlebitis 5.6%. Given all the associated injuries, scapula fractures are often considered an unofficial surrogate for other injuries in blunt trauma cases, warranting thorough secondary and tertiary surveys and clinical monitoring. This concept is demonstrated in a study evaluating 291,632 pediatric patients who sustained blunt trauma. The 1960 patients with scapula fracture were 10 times more likely to also have great vessel injury (1.17%) compared with those without a scapula fracture (0.12%, P < .0001). The authors suggested the presence of scapula fracture warrants CT scans in pediatric blunt trauma patients to rule out great vessel injury. Landi et al. have described a compartment syndrome associated with a scapula fracture. Various other cardiothoracic, genitourinary, and gastrointestinal injuries have also been reported. Majoub et al. recounted a case of quadrilateral space syndrome after scapula fracture. Interestingly, Stephens and associates reviewed 173 blunt trauma patients (92 with scapula fractures and 81 controls) and concluded that scapula fractures are not a significant marker for greater mortality or neurovascular morbidity. Several other studies have demonstrated no increase in mortality associated with scapula fracture but significantly greater severity scores in trauma patients sustaining scapula fractures. , ,
Complications related to scapula fractures themselves are relatively uncommon. Nonunion, although possible, is quite rare. Malunion can occur in various forms depending on the particular fracture type. Malunion of a scapular body fracture is generally well tolerated; however, painful scapulothoracic crepitus has been described on occasion. Fractures of the glenoid cavity can result in symptomatic glenohumeral degenerative joint disease. Shoulder instability can be associated with significantly displaced fractures of the glenoid neck (angular displacement) and fractures of the glenoid rim. Fractures of the glenoid neck with significant translational displacement can give rise to glenohumeral pain and dysfunction related to altered mechanics of the surrounding tissues. While the criteria for surgical management are evolving as more scapula fractures are diagnosed with the broad use of CT scan–based trauma evaluations, it is important to note that, regardless of intervention, many patients do well with nonoperative management of a scapula fracture. A recent systemic review examining 453 patients sustaining scapula fractures with follow-up data revealed high satisfaction rates in those managed nonoperatively (90%) and operatively (94%).
Complications associated with surgical management occur approximately 3% of the time and include infection (both superficial and deep), intraoperative neurovascular injury, loss of fixation, and others. A poorly managed postoperative rehabilitation program can lead to unnecessary shoulder stiffness.
Finally, complications related to poor patient compliance can occur. Examples include suboptimal shoulder range of motion caused by unwillingness to follow the postoperative physical therapy program and hardware failure associated with failure to observe postoperative instructions.
A fracture of the scapula is a radiographic diagnosis, but precisely defining the injury can be difficult. If a scapula fracture is suspected or noted on other imaging modalities, a scapula trauma series is indicated, including true anteroposterior (AP), lateral views of the scapula (including scapular Y view), and a true axillary projection of the glenohumeral joint ( Fig. 13.6 and Box 13.2 ). These radiographs are useful for diagnosis of scapular body and spine acromion process but have been shown to be less accurate in diagnosis of coracoid process, glenoid fossa, and neck fractures. Regardless, radiographs should be used to trend fracture displacement and healing in outpatient follow-up.
Fractures often detected incidentally on chest radiograph or CT
Scapula trauma series:
AP and lateral views of the scapula
Axillary view of the glenohumeral joint
Weight-bearing view of the shoulder
CT with and without reconstructions
Three-dimensional CT with humeral subtraction
The scapula is a complex bony structure. One must be able to visualize and evaluate the scapular body and spine and its three other processes: the glenoid process, acromial process, and coracoid process. The glenoid process is composed of the glenoid neck and glenoid cavity; the glenoid cavity is made up of the glenoid fossa and glenoid rim. The scapula takes part in three articulations (the AC joint, glenohumeral joint, and scapulothoracic articulation), each of which must be carefully evaluated. Associated shoulder girdle injuries should also be considered, including those involving the clavicle, proximal part of the humerus, and sternoclavicular joint.
If an injury to the SSSC (the linkage system between the clavicle and scapula) is suspected, a weight-bearing AP film is obtained if tolerated (see Fig. 13.6 ). If the fracture appears displaced, intra-articular, or complex in pattern, CT imaging is necessary. Anecdotally, some institutions are able to reconstruct dedicated images of the scapula from a chest CT. Using this feature may help to reduce radiation exposure, trips to the imaging suite, and cost. Regarding the epidemiology of scapula fractures and imaging, Tatro et al. recently examined 10 years of National Trauma Bank patients and noted that the incidence of scapula fracture diagnosis has increased concurrently with the increase in diagnostic CT trauma scans. While CT imaging is not indicated for minimally displaced scapula fractures, the increased use of CT scans in trauma patients aids in diagnosing previously missed scapula fractures, regardless of clinical significance. Tadros et al. found two-dimensional CT was less sensitive than 3D CT for diagnosis of scapular neck and spine fractures.
Images in the superior plane allow the evaluation of the AC joint and acromial process, whereas the inferior images allow the visualization of the scapular body and spine and the scapulothoracic articulation ( Fig. 13.7 ). The middle images allow visualization of the glenoid neck, glenoid cavity (glenoid rim and glenoid fossa), coracoid process, and glenohumeral articulation ( Fig. 13.8 ). In certain clinical situations, reconstructed views can be of great value. The proximal part of the humerus can be subtracted for optimal visualization of the glenoid cavity, and other reconstructed images are possible ( Fig. 13.9 ). Three-dimensional CT can be extremely helpful to an orthopedist trying to evaluate the most complex fracture patterns and has the highest sensitivity for detecting all scapula fracture patterns compared with radiographs and two-dimensional CT ( Fig. 13.10 ). Interestingly, McAdams et al. found that CT scanning did not improve the evaluation of glenoid fractures over plain films but did help in identifying associated injuries to SSSC. Conversely, Anavian et al. suggested that 3D CT more accurately measures scapular fracture displacement. Dugarte et al. described innovative 3D CT fracture mapping of scapula fractures. This technology may contribute not only to preoperative planning but also a registry of scapula fractures that may lead to an improved classification system.
The clinician must be careful to avoid mistaking nontraumatic radiographic findings (epiphyseal lines, os acromiale, glenoid dysplasia, and scapular foramina) for actual traumatic changes.
Types of fractures and methods of treatment
Glenoid neck (extra-articular) fractures
The glenoid neck is that portion of the glenoid process medial to the glenoid cavity and lateral to the scapular body. The coracoid process arises from its superior aspect. The junction between the scapular body and glenoid neck is defined by a line parallel to the glenoid cavity (superior to the inferior rim), running from the lateral border of the scapular notch to the lateral scapular margin. True glenoid neck fractures (discussed here) comprise approximately 5% of all scapular fractures. They exit along the inferior glenoid neck/lateral border of the scapular body, course through the spinoglenoid notch, and exit most often medial to the coracoid process (surgical neck fractures) or, rarely, lateral to the coracoid process (anatomic neck fractures). These injuries are to be distinguished from those far more common disruptions that involve the inferior glenoid neck/lateral border of the scapular body but course through the body to exit through its medial (most common) or superior borders. Such injuries, termed scapular neck and body fractures, should simply be termed (and managed as) scapular body fractures to avoid confusion and will be discussed in the section dealing with scapular body fractures.
Glenoid neck fractures may be caused by the following:
A direct blow over the anterior or posterior aspect of the shoulder.
A fall on the outstretched arm with impaction of the humeral head against the glenoid process.
In rare cases a force applied over the superior aspect of the shoulder complex.
The stability of the glenoid neck is primarily osseous, specifically its junction medially with the scapular body. Secondary support is provided by its attachments superiorly to the clavicular, AC joint–acromial strut via the coracoid process, coracoclavicular ligament, and CA ligament ( Fig. 13.11 ). Tertiary soft tissue support is provided anteriorly by the subscapularis muscle, superiorly by the supraspinatus muscle, and posteriorly by the infraspinatus and teres minor muscles. In a true/complete glenoid neck fracture (a fracture exiting both the superior and lateral scapular margins), displacement may occur ( Box 13.3 ). That these injuries are not more common is somewhat surprising because this portion of the glenoid process is quite narrow; however, the large muscular soft tissue envelope, general mobility of the scapula, and relative girth of this area compared with the rest of the scapula helps to explain why these fractures are uncommon. When they do occur, it is important to note that instability leading to displacement can be due to injury of the SSSC (see Fig. 13.11 ). Historically, Goss suggested that a double hit to the SSSC would lead to instability and warrant fixation. However, Williams et al. performed a biomechanical study demonstrating that a scapular neck fracture exiting medial to the coronoid base is only unstable if the CA, coracoclavicular, and AC ligaments and capsule are disrupted. Hardegger et al. described a rare case wherein the fracture line exited the superior scapular margin lateral to the coracoid process (the anatomic neck) ( Fig. 13.12 ), thereby allowing the glenoid fragment to be displaced laterally and distally by the pull of the long head of the triceps muscle. Arts and Louette described a similar injury. They saw these fractures as inherently unstable (the primary support is completely disrupted and the fracture is lateral to the secondary support system) and in need of an open reduction and internal fixation (ORIF). In contrast, fractures of the surgical neck are only rendered unstable and in need of surgical management when accompanied by associated injuries to the secondary support system. More than 90% of scapular neck fractures lack significant displacement. Management is nonoperative, and a good to excellent functional result can be expected.
ML displacement (lateral border offset) ≥20 mm
AP angular displacement (angular deformity) ≥45 degrees
Decrease in the GPA to ≤20–22 degrees
Combined angular deformity ≥35 degrees with ML displacement ≥15 mm
Displaced double lesions of the SSSC
Clavicle and scapula fracture displaced ≥10 mm or
Complete AC separation with scapula fracture displaced ≥10 mm
Rule out a “false glenoid neck” fracture (i.e., an inferior glenoid neck fracture that does not exit the superior scapular margin)
Defining significant displacement of glenoid neck fractures continues to evolve. Due to the low incidence of scapula fractures, indications for fixation are based on small retrospective studies. Cole et al. used the following as operative indications for displaced glenoid neck fractures: medial lateral (ML) displacement (also referred to as lateral border offset) greater than 20 mm, AP angular displacement or angular deformity greater than 45 degrees, a decrease in the glenopolar angle (GPA) to less than 22 degrees, or combined angular deformity greater than 35 degrees with ML displacement greater than 15 mm. It should be noted that measurement of the GPA can be falsely underestimated based on rotation of scapula relative to the neutral plane ( Fig. 13.13 ). , Limb and McMurray described the case of a patient with a glenoid neck fracture so severely displaced and inferiorly angulated that the humeral head was articulating with the medial fracture surface and lateral margin of the scapular body. ML translational displacement of 1 cm was chosen by Zdravkovic and Damholt, Nordqvist and Petersson, and Miller and Ada , as separating major from minor injuries. Bateman stated that this degree of displacement could interfere with abduction. Hardegger and coworkers pointed out that significant ML translational displacement changes the normal relationships between the glenohumeral articulation and the undersurface of the distal end of the clavicle, the AC joint, and the acromial process. This displacement alters the mechanics of nearby musculotendinous units, resulting in a functional imbalance of the shoulder complex as a whole (a disorganization of the CA arch). Miller and Ada , stated that resultant weakness (especially abductor weakness), decreased range of motion, and pain (particularly subacromial pain) were largely due to rotator cuff dysfunction. The premise that significant ML translational displacement of the glenoid process can lead to shoulder discomfort and dysfunction certainly makes sense intuitively. The complex bony relationships in the glenohumeral region are clearly altered, as are the mechanics of the musculotendinous structures that pass from the scapula to the proximal part of the humerus (the deltoid muscle and rotator cuff, in particular). The fracture line usually exits the superior scapular margin medial to the coracoid process (the surgical neck region). The glenoid fragment is then drawn inferiorly by the weight of the arm and either anteromedially or posteromedially by the adjacent muscle forces causing ML transitional displacement. Whether the glenoid fragment displaces medially or the scapular body displaces laterally has been argued but is clinically irrelevant ( Fig. 13.14 ).
Bateman and DePalma stated that excessive angulation of the glenoid fragment could result in glenohumeral instability (anterior, posterior, or inferior). Normally, the glenoid cavity faces 5 degrees superiorly and is retroverted 6 degrees relative to the plane of the scapular body. With increasing angulation, the humeral head loses the normal bony support provided by the glenoid cavity (bony instability), which translates into glenohumeral discomfort and dysfunction. , Miller and Ada , stated that AP angular displacement of 40 degrees or more was unacceptable. They saw this degree of displacement as adversely altering not only glenohumeral but also other bony relationships, as well as musculotendinous dynamics, particularly those of the rotator cuff, with resultant pain and overall shoulder dysfunction (diminished range of motion and loss of strength) ( Fig. 13.15 ). Van Noort and van Kampen recommended surgical management for glenoid neck fractures with a decrease in the GPA to 20 degrees or less and normal GPA ranges from 30 to 45 degrees. , Bartonicek et al. described the management of glenoid neck fractures with various displacements, including those with significant translational displacement in the superior/inferior direction and those with significant superior angular displacement.
Imatani, McGahan and associates, and Lindholm and Leven recommended nonsurgical treatment of all glenoid neck fractures, but their studies give few details to justify this conclusion. Van Noort and van Kampen managed 13 patients with neither significant angular displacement, neurologic injury, nor associated ipsilateral shoulder injuries, all of whom had a good to excellent outcome regardless of the degree of translational displacement when treated nonoperatively. Bozkurt et al. reported on 18 patients treated nonoperatively and found that decreased functional outcome correlated significantly with increased inferior angulation of the fracture and the presence of associated injuries.
Although somewhat ambivalent in their recommendations, two studies do mention surgical management as an option in selected cases. Armstrong and Van de Spuy said that, although most of these injuries do well, more aggressive treatment, including ORIF, may be indicated in patients who are young and fit. Wilber and Evans stated that ORIF might be indicated if the glenoid fragment is markedly displaced or angulated but did not think that they had enough information or experience to warrant definitive surgical indications. Judet, Magerl, Ganz and Noesberger, and Tscherne and Christ reported that operative management of displaced glenoid neck fractures prevents late disability and yields better results. Neer, as well as Neer and Rockwood and Butters, presented the recommendations of other investigators, as did a review article by Guttentag and Rechtine. Boerger and Limb reported the case of a patient with a fracture of the glenoid neck, acromial and coracoid fractures, a dislocated AC joint, and incomplete paralysis of the infraspinatus muscle treated with ORIF of the acromial and glenoid neck fractures. DeBeer et al. described the operative treatment of a professional cyclist who was able to return to competition after 6 weeks and urged more aggressive management in high-demand patients.
Miller and Ada , retrospectively reviewed 16 displaced glenoid neck fractures (≥1 cm of ML translational displacement or ≥40 degrees of AP angulation) managed nonoperatively (36-month average follow-up). They found that 20% had decreased range of motion, 50% had pain (75% of which was night pain), 40% had weakness with exertion, and 25% noted popping. In particular, these patients often had shoulder abductor weakness and subacromial pain that was due at least in part to rotator cuff dysfunction. They recommended ORIF of glenoid neck fractures with this degree of displacement. Chadwick et al. agreed.
Pace et al. reviewed nine patients with insignificantly displaced fractures and found that the majority had some activity-related pain that was believed to be due to impingement and cuff arthropathy despite 90% good to excellent results. A long-term follow-up study by Zdravkovic and Damholt included 20 to 30 patients (it is difficult to determine the exact number from the text) with displaced glenoid neck fractures and noted that nonoperative treatment yielded satisfactory results. Nordqvist and Petersson evaluated 37 glenoid neck fractures treated without surgery (10- to 20-year follow-up) and found the functional result to be either fair or poor in 32%. They said that for some fractures, early ORIF might have improved the result. Hardegger et al. reported 80% good to excellent results in five displaced glenoid neck fractures treated surgically (6.5-year follow-up). They said that operative management of such injuries prevented late disability and yielded better results. Gagey et al. found a good result in only 1 of 12 displaced fractures treated nonoperatively. They stated that such injuries could “disorganize the coracoacromial arch” and recommended ORIF.
Clearly, these investigators agree that the vast majority of glenoid neck fractures can and should be treated without surgery. More recent literature trends to support operative management of displaced scapular neck fractures; however, refining selection criteria is difficult due to the low incidence of scapula fractures. In a recent systematic review, Kannan et al. found significant difference in satisfactory results for nonoperative management of scapular neck fractures with displacement less than 10 mm (94.7%) compared with fractures with displacement greater than 10 mm (15.7%). Satisfactory results were defined as return to work, outcome described as excellent/satisfactory/good, minimal to no pain, and range of motion that was full or slightly limited. Also in this review, all patients with greater than 10 mm of displacement managed with ORIF had satisfactory results, suggesting greater than 10 mm of displacement as appropriate selection criteria for operative management.
The diagnosis is ultimately radiographic. Plain radiographs are helpful, but because of the complex bony anatomy in the area, CT is generally necessary to determine management based on completion of the glenoid neck fracture, and more accurate measurement of AP angulation, ML displacement, and GPA compared with radiographs. , CT can also identify injuries to adjacent bony structures and articulations. These injuries should not be confused with the more common fractures that course through the inferior glenoid neck and then exit through the scapular body (see Fig. 13.12 ). CT readily reveals that the latter are not complete disruptions of the glenoid process because the superior aspect of the glenoid neck is intact. Some of these injuries are akin to fractures of the scapular body and can be managed as such ( Fig. 13.16 ). Finally, if an injury to SSSC (the clavicular-scapular linkage) is suspected, a weight-bearing AP view of the shoulder is obtained if tolerated.
Glenoid cavity (intra-articular) fractures
Fractures of the glenoid cavity make up 30% of scapula fractures. The majority (>90%) are insignificantly displaced and are managed nonoperatively ( Fig. 13.17 and Box 13.4 ). Significantly displaced fractures require surgical treatment or at least merit surgical consideration. Ideberg reviewed more than 300 such injuries and proposed the first detailed classification scheme, , , which was subsequently expanded by Goss, who added four varieties (types Ib, Vb, Vc, and VI) to Ideberg’s original five ( Fig. 13.18 ). Type I fractures involve the glenoid rim: type Ia, the anterior rim; and type Ib, the posterior rim. Fractures of the glenoid fossa make up types II to V. Type VI fractures include all comminuted injuries (more than two glenoid cavity fragments).
Glenoid rim fractures
Unstable glenohumeral articulation:
Displacement of fragment ≥10 mm
Involvement of ≥¼ of glenoid cavity anteriorly
Involvement of ≥1⁄3 of glenoid cavity posteriorly
Glenoid fossa fractures
Articular step-off ≥5 mm
Unstable glenohumeral articulation
Severe separation of fragments
Fractures of the glenoid rim occur when the humeral head strikes the periphery of the glenoid cavity with considerable violence ( Fig. 13.19 ). These injuries are true fractures, distinct from the small avulsion injuries that occur when a dislocating humeral head applies a tensile force to the periarticular soft tissues. Iatrogenic fractures of the glenoid rim have also been described as a unique entity, occurring through suture anchor holes. , A true axillary view of the glenohumeral joint, CT imaging (routine and reconstructive), and, if necessary, 3D scanning should be used allow one to determine the size and displacement of the rim fragment, whether persistent subluxation of the humeral head is present and therefore whether stability of the glenohumeral articulation is significantly compromised and/or articular step-off acceptable ( Figs. 13.20 and 13.21 ).
Fractures of the glenoid fossa occur when the humeral head is driven with significant force into the center of the concavity. The fracture generally begins as a transverse disruption (or slightly oblique), for several possible reasons:
The glenoid cavity is concave; therefore forces tend to be concentrated over its central region.
The subchondral trabeculae are transversely oriented; therefore fractures tend to occur in this plane.
The glenoid cavity is formed from two ossification centers; therefore the central region can remain a persistently weak area.
The glenoid cavity is narrow superiorly and wide inferiorly, with an indentation along its anterior rim. This anatomy constitutes a stress riser where fractures are particularly prone to originate before coursing over to the posterior rim ( Fig. 13.22 ).
Once a transverse disruption occurs, the fracture can propagate in various directions, depending on the exact direction of the humeral head force. An AP projection of the glenohumeral joint, reconstructed CT images, and even 3D CT with humeral subtraction may be necessary to accurately determine whether and to what degree articular incongruity, separation, or both are present. If an injury to the SSSC (the scapular-clavicular linkage) is suspected, a weight-bearing AP view of the shoulder is obtained.
Goss-Ideberg type I fractures of the glenoid rim are designated as Ia for anterior rim and Ib for posterior rim. Anterior rim fractures are often associated with instability events, and those involving the anteroinferior glenoid rim overlap in description with osseous Bankart lesions. For acute anterior rim fractures involving less than 5% of the glenoid surface, conservative management may be appropriate as long as the glenohumeral joint is concentrically reduced.
Surgical management of fractures of the glenoid rim is indicated if the fracture results in persistent subluxation of the humeral head (failure of the humeral head to lie concentrically within the glenoid cavity) or if the articulation is unstable after reduction. DePalma stated that instability could be expected if the fracture is displaced 10 mm or more and if a quarter or more of the glenoid cavity anteriorly or a third or more of the glenoid cavity posteriorly is involved. Hardegger and coworkers concurred and stated that operative reduction plus fixation of the fragment is indicated to prevent recurrent or permanent dislocation of the shoulder. Guttentag and Rechtine and Butters agreed with these recommendations. Several papers describing the operative management of glenoid rim fractures have appeared in the literature. Surgery, if necessary, is designed to restore articular stability and prevent posttraumatic degenerative joint disease ( Fig. 13.23 ).
With type II glenoid fossa fractures, the humeral head is driven inferiorly, creating an inferior glenoid fragment. Surgery is generally indicated if an articular step-off of 5 mm or more is present or if the fragment is displaced inferiorly and carries the humeral head with it such that the humeral head fails to lie in the center of the glenoid cavity ( Fig. 13.24 ). Strict indications for surgical intervention based on articular step-off are lacking; various sources recommend management of step-off ranging from 2 to 10 mm. , , Cole et al. evaluated a case series of operative scapula fractures and of the 29 intra-articular glenoid fractures treated, a step-off of 4 mm was used as the threshold for operative management. The inferior fragment is often further displaced inferiorly by the origin of the long head triceps and should be monitored for displacement. Bartonicek et al. described their experience with operative management of 29 inferior glenoid fractures with a mean 52-month follow-up. Their indications for operative management included articular step-off greater than 3 to 4 mm, involvement of at least one-third of the glenoid, and unspecified significant displacement. In this cohort, all fractures healed and there was no evidence of glenohumeral arthritis in follow-up. Complications included: hardware failure, hematoma, infection, external rotation weakness (due to mobilization of infraspinatous on approach), and stiffness.
These injuries can result in posttraumatic degenerative joint disease, glenohumeral instability, or both.
Type III (glenoid fossa) fractures occur when the force of the humeral head is directed superiorly and causes the transverse disruption to propagate upward, generally exiting through the superior scapular margin in the vicinity of the suprascapular notch. , Displacement is usually minimal, with the fragment lying medially. Consequently, these injuries are generally treated nonoperatively and heal uneventfully.
Any glenoid cavity fracture may be associated with a neurovascular injury due to the proximity of the brachial plexus and axillary vessels, as well as the considerable violence involved. Type III injuries, as well as type Vb, Vc, and VI, are especially prone to such neurovascular involvement. Neer and Rockwood considered compression of the adjacent neurovascular structures by these and fractures of the coracoid process to be indications for surgery. They and others also described the occurrence of suprascapular nerve paralysis associated with fractures involving the coracoid process and the glenoid neck that extend into the suprascapular notch (electromyography [EMG] testing was essential to make the diagnosis, and early exploration was recommended). Cole et al. note a suprascapular nerve injury in 12 of 84 scapula fractures treated operatively, although nerve injury itself was not an indication for surgery. Nerve injury was confirmed by EMG either preoperatively or postoperatively. Preoperative EMG was obtained at least 2 weeks from injury, and postoperative EMG was obtained in cases where the nerve was identified as injured intraoperatively. In 4 of the 12 cases the suprascapular nerve was found partially torn with incarceration in the fracture site and/or callus. In 2 of the 12 cases, the suprascapular nerve was completely torn.
Surgical management of type III fractures is indicated if the fracture has an articular step-off of 5 mm or more with lateral displacement of the superior fragment ( Fig. 13.25 ). It is important to understand the fracture pattern in type III. For example, if the acromion process, scapular spine, and body are united as one fragment while a portion of the glenoid and coracoid base and process compromise a separate fragment, the two fragments are still united by soft tissue via the CA ligament directly, and the coracoclavicular ligaments and AC ligaments and capsule indirectly. These soft tissue components of the SSSC provide stability to this fracture pattern and allow for nonoperative management. If all of these ligaments are injured and/or there is a more complex fracture pattern, operative management may be necessary. If so, it is important to note that the origin of the short head of the biceps and coracobrachialis on the coracoid process can lead to inferior displacement of this fragment.
These injuries can result in posttraumatic degenerative joint disease and severe functional impairment. Hui et al. reported on 10 such combined injuries.
Type IV (glenoid fossa) injuries occur when the humeral head is driven directly into the center of the glenoid cavity. The fracture courses transversely across the entire scapula and exits along its medial border. If there is an unacceptable articular step-off (≥5 mm) with the superior fragment displaced laterally, or if the superior and inferior glenoscapular segments are severely separated, ORIF is indicated to prevent symptomatic degenerative joint disease, nonunion at the fracture site (an extremely rare occurrence but a definite concern in the case shown [ Fig. 13.26 ]), and instability of the glenohumeral joint. Ferraz et al. described a type IV glenoid fossa fracture that progressed to a nonunion. When explored surgically less than 2 years after injury, a 7-mm articular step-off and grade III cartilaginous erosion of the humeral head were noted.
These glenoid fossa injuries are combinations of type II, III, and IV injuries and are caused by more violent and complex forces. The same clinical concerns and operative indications detailed for the type II, III, and IV fractures apply to type V fractures ( Fig. 13.27 ). Nork et al. reported on several types IV and V fractures with associated disruptions of the scapular body that required surgical management of both injuries.
Type VI glenoid cavity fractures are caused by the most violent forces and include all disruptions in which more than two articular fragments are present. Goss originally recommended against operative management of these comminuted fractures in 1992. Several papers since report the high union rate of surgically treated scapula fractures due to the rich blood supply and muscular envelope, yet the union rate for comminuted intra-articular glenoid fractures is not well described. With advancement in arthroscopic-assisted ORIF and dual (anterior/posterior) open approaches to scapula and glenoid ORIF, the dogma of managing all of these type VI fractures nonoperatively should be reexamined on a case-by-case basis. There may be a role for surgical correction in a younger patient versus allowing the fracture to heal and treating painful/symptomatic articular incongruence or glenohumeral arthrosis with arthroplasty.
Overview of glenoid fossa fractures
The Goss-Ideberg classification (see Fig. 13.18 ) is helpful in categorizing glenoid fractures, because it is often referenced in case reports and other literature discussing management and outcomes of these fracture types. However, it is important to note the limitations of this classification system. First, this classification system does not predict morbidity nor does it guide intervention. Second, approximately 25% of glenoid fractures cannot be classified by this system. Although the superiority and mainstream use of the updated AO classification is yet to be determined, Gilbert et al. demonstrate higher intraobserver and interobserver reliability of the AO classification compared with Ideberg and Euler’s classification systems.
Reports by Aulicino et al. and Aston and Gregory lend support to the role of surgery in managing significantly displaced glenoid fossa fractures. Lee et al. reported the case of a child who sustained a type II fracture that required ORIF. Ruedi and Chapman stated that “grossly displaced intra-articular fractures of the glenoid that render the joint incongruent and unstable profit from operative reconstruction and internal fixation as incongruities result in osteoarthritic changes.” Rowe advocated surgical management of severely displaced injuries. Bauer and coworkers reviewed 20 patients treated surgically for significantly displaced fractures of the scapula (6.1-year average follow-up) and reported greater than 70% good or very good results based on the Constant score. They recommended early ORIF for grossly displaced fractures of the glenoid fossa, glenoid rim, glenoid neck, and coracoid and acromial processes. Hardegger and associates reported that if “there is significant displacement, conservative treatment alone cannot restore congruency,” and stiffness and pain can result: “for this reason open reduction and stabilization are indicated.”
Kavanagh et al. presented their experience at the Mayo Clinic in which 10 displaced intra-articular fractures of the glenoid cavity were treated with ORIF. They found ORIF to be “a useful and safe technique” that “can restore excellent function of the shoulder.” In their series, the major articular fragments were displaced 4 to 8 mm. The authors emphasized that they remained uncertain how much incongruity of the glenoid articular surface can be accepted without risking the long-term sequelae of pain, stiffness, and traumatic osteoarthritis. Soslowsky and coworkers found the maximal depth of the glenoid articular cartilage to be 5 mm. Consequently, if a glenoid fossa fracture is associated with an articular step-off of 5 mm or more, subchondral bone is exposed. Schandelmaier et al. reported a series of 22 fractures of the glenoid fossa treated with ORIF. They stated that “if the postoperative courses are uneventful, excellent to good results can be expected.” Leung et al. reviewed 14 displaced intra-articular fractures of the glenoid treated with ORIF (30.5-year average follow-up) and reported nine excellent and five good results. Anavian et al. reported on 33 patients with displaced intra-articular fractures of the glenoid with or without involvement of the scapular body. They noted good functional outcomes postoperatively with a low complication rate. Mayo et al. described their experience with 27 fractures treated operatively for displaced glenoid fossa fractures. They were able to accomplish what they termed anatomic reconstruction with a low complication rate and good functional outcomes.
Zahid et al. described 100% union rates, return to work, and improved Disability of the Arm, Shoulder and Hand (DASH) scores at a minimum of 6-month follow-up in 12 patients with intra-articular glenoid fractures managed surgically, consisting of 5 Ideberg type III, 6 Ideberg type IV, and 1 Ideberg type V fractures. In a systematic review of scapula fractures, 44 patients with displaced glenoid fractures were evaluated and 32 were treated surgically. In those treated surgically, 90% had satisfactory results (e.g., clinical outcome described as good/satisfactory/excellent, little to no pain, return to work, full to slightly limited range of motion). Only 25% of patients with displaced glenoid fractures managed nonoperatively had satisfactory results.
Based on these reports, it is reasonable to conclude that surgery has a role in the treatment of glenoid cavity fractures. Numerous case reports and studies describe arthroscopically assisted fixation of displaced glenoid cavity fractures. The proposed advantages include limited associated soft tissue dissection, preservation of the blood supply to the fracture fragment, direct arthroscopic visualization of the articular reduction, preventing intra-articular screw penetration, and the possibility of addressing associated capsulolabral and rotator cuff pathology. Complications include technical difficulty, possible suprascapular and axillary nerve injury from K-wire/screw placement, stiffness, and recurrent instability. Sugaya et al. described eight patients with significantly displaced type Ia fractures managed arthroscopically. Yang et al. studied 18 patients with Goss-Ideberg type III glenoid cavity fractures who underwent arthroscopically assisted reduction and fixation with 4.0-mm cannulated screws. At final follow-up (minimum 2 years), they reported excellent range of motion as well as validated patient outcome scores (average visual analog scale, 0.7; Constant score, 96.8; American Shoulder and Elbow Surgeons, 96.0; and University of California at Los Angeles score, 34.3) without complications. Tauber and coworkers reported on 10 patients with acute anterior glenoid cavity fractures (Goss-Ideberg type Ia) compromising at least 21% of the glenoid fossa. They used cannulated titanium screws placed percutaneously under arthroscopic visualization. At a 2-year follow-up, nine patients had good/excellent results and one had a fair result. One patient had recurrent instability. Bauer and coworkers reported on five patients with intra-articular fractures of the glenoid cavity who were treated with arthroscopic reduction and suture fixation through drill holes. Multiple case reports have described arthroscopic management using partially threaded cannulated screws and K-wires.
Fractures of the scapular body and spine
These injuries are often rather alarming radiographically: extensive comminution and displacement are often present ( Fig. 13.28 ). However, there has been very little enthusiasm in the literature for operative treatment for the following reasons: bone stock for fixation is at a premium, 90% or greater of these injuries heal quite nicely with nonoperative care, and a good to excellent functional result can be expected.
The reasons for this generally favorable prognosis are as follows: (1) scapular body fractures almost invariably go on to union, and (2) the thick layer of soft tissues within the scapulothoracic interval and the mobility of the scapulothoracic articulation compensate for most residual deformities of the scapular body. The literature does mention a fracture of the scapular body with a lateral spike entering the glenohumeral joint as an indication (albeit extremely uncommon) for surgical management, and a similar recommendation was made in two cases involving patients with fractures of the scapular body and intrathoracic penetration by one of the fragments. , Bowen et al. reported a case of a significantly angulated greenstick fracture of the scapular body that required a closed reduction. On rare occasions, malunion of a scapular body fracture can result in scapulothoracic pain and crepitus requiring surgical exposure of its ventral surface and removal of the responsible bony prominence(s). Nonunion of a scapular body fracture requiring surgical management has been described. ,
The vast majority (>90%) of fractures of the scapular body (and insignificantly displaced fractures of the scapula in general) are managed nonoperatively. These patients are initially placed in a sling and swathe binder for comfort. Local ice packs to the affected area are helpful during the first 48 hours, as needed. Absolute immobilization is generally short (48 hours) but can continue for up to 14 days, depending upon the clinical situation. The patient is then permitted to gradually increase use of the upper extremity as symptoms allow, and sling and swathe protection is gradually decreased until the 6-week point.
Physical therapy is prescribed during this period and focuses on maintaining/regaining shoulder range of motion. The program begins with dependent circular and pendulum movements, as well as external rotation to but not past neutral and gradually moves on to progressive stretching techniques in all ranges. Close follow-up is necessary to monitor and guide the patient’s recovery, and radiographs are obtained to ensure that unacceptable displacement does not occur at the fracture site(s).
At 6 weeks, osseous union is usually sufficient to discontinue all external protection and encourage full functional use of the upper extremity. However, the rehabilitation program continues until range of motion, strength, and overall function are maximized. Six months to 1 year may be required for a full recovery, but a good to excellent result should be readily obtainable.
Recently, some have recommended dramatic changes in the management of scapular body fractures, and surgical management in certain situations is gaining favor. The group led by Cole has been particularly active in this regard. In 2013 they summarized their approach to the management of scapular body fractures, with an emphasis on surgical indications, approaches, and techniques.
The scapular body is that portion of the scapula medial to a line parallel to the plane of the glenoid fossa (superior to inferior rims), running from the lateral border of the scapular notch (coursing through the spinoglenoid notch) to the junction between the inferior glenoid neck and the lateral scapular border. Its superior, medial, and lateral cortical borders surround a thin central zone. The superior border meets the medial border at the superior angle, while the lateral border meets the medial border at the inferior angle. The scapular spine protrudes posteriorly. It meets the medial border at the spinomedial junction and joins the acromial and glenoid processes at the spinoglenoid notch. The lateral border/glenoid neck pillar is quite important to the overall integrity of the scapula ( Fig. 13.29 ). Fractures of this area if associated with a second scapular body disruption (most often an exit point along the medial border but occasionally at the superior border via the scapular spine) can significantly alter the position of the glenoid process/glenohumeral joint relative to the surrounding bony and soft tissues (destabilizing the overall shoulder complex), with adverse functional consequences. Radiographic findings that indicate significant compromise of the integrity of the lateral border/glenoid neck pillar and the overall integrity of the scapular body include (1) ML translation of the glenoid process relative to the lateral scapular border of greater than or equal to 20 mm as seen on AP radiographs or 3D CT, (2) AP angulatory deformity of the lateral border of 45 degrees or greater as seen on a scapular Y view or 3D CT, (3) lateral border/glenoid process ML translation of 15 mm or greater and AP angular deformity of the lateral border greater than or equal to 30 degrees, and (4) a GPA of 20 degrees or less as seen on AP radiographs ( Fig. 13.30 ). In such situations, reestablishing the integrity of the cortical perimeter of the scapular body (especially the lateral border/glenoid neck pillar but often the medial and/or superior borders as well) has been recommended by several authors to restore scapular length, alignment, rotation, and, ultimately, overall shoulder mechanics/function ( Box 13.5 ).
Unacceptable position of glenoid process
ORIF, which aids ORIF of associated glenoid process fracture
Rare fractures with especially severe displacement
ORIF border disruptions, especially lateral border/glenoid neck pillar
Dynamic compression plates
Malleable reconstruction plates
The patient is placed on a radiolucent table either prone or lateral decubitus with affected side up, and the scapular body is approached posteriorly. An extensile Judet approach may be used. The posterior deltoid and infraspinatus muscles are detached from their origins and reflected from medial to lateral, allowing access to the lateral and medial scapular borders and the scapular spine. This exposure is limited by the suprascapular neuromuscular bundle, which must be protected. The circumflex scapular artery, if encountered, is tied off ( Fig. 13.31 ). A modified Judet approach with development of the infraspinatus/teres minor interval is used if exposure of the posterior glenoid process and access of the interior of the glenohumeral joint is necessary. Further development of this interval allows access to the lateral scapular border. Access to the scapular spine is gained through the posterior deltoid/trapezius interval. Access to the medial scapular border is gained through the infraspinatus/rhomboids interval. Gauger and Cole described minimally invasive approaches for recent (<10 days old) scapular border fractures with simple patterns (two exit points) in seven patients. They noted outcomes that they described as being comparable with the normal uninjured population without complications.
Disruptions of the lateral border, medial border, and superior border/scapular spine are exposed, reduced, and provisionally stabilized. The lateral border/glenoid neck pillar has priority and is managed first, because its reduction reorients the glenohumeral joint and reestablishes an intact post to facilitate reconstruction of the rest of the scapula. Once the scapular perimeter has been reestablished, the borders are definitively stabilized. A dynamic compression plate is used for the lateral border. However, if the inferior aspect of the glenoid neck is involved, a contoured reconstruction plate may be required to gain purchase on the glenoid process. Medial border disruptions are secured with a reconstruction plate contoured appropriately to gain fixation over the medial scapular spine and down the medial border ( Fig. 13.32 ). Disruptions involving the superior border via the scapular spine are stabilized with a dynamic compression plate applied along the scapular spine. Locking plates are used wherever bone stock is deficient. Particularly complex patterns may require other fixation devices ( Fig. 13.33 ). Associated fractures involving the glenoid, acromial, and coracoid processes as well as double disruptions of SSSC are managed according to the principles detailed for those specific injuries.
Nork et al. described 17 patients with displaced Goss-Ideberg IV, V, and VI glenoid cavity fractures with significantly displaced scapular body fractures exiting the medial border. They felt that ORIF of the medial border disruption significantly aided in the ORIF of the glenoid process fracture. Bartonicek and Fric reported on 22 patients with scapular body fractures with or without articular involvement treated surgically (minimal follow-up, 12 months). They stated that in all patients, primary bone union and anatomic restoration between the glenoid process and scapular body were achieved. Congruency and stability of the shoulder was achieved in all, and the average Constant score was 94. Cole et al. described 74 patients with displaced scapular body fractures with or without articular involvement treated surgically. All fractures united in good position. The authors concluded that restoration of normal anatomy was relatively safe and effective, thus affording to the patient the best chance for an optimal functional recovery. Cole et al. reported on five patients who underwent reconstructive surgery for extra-articular scapula malunions. The mean time from injury to surgery was 15 months (range, 8 to 41 months). All fractures united. All patients were pain free and expressed satisfaction with the result. Four of the five individuals returned to their original occupation and activities. A recent systematic review found 97 patients with scapular body fractures, of which 75 (77%) were managed nonoperatively. Results were satisfactory in 100% of the nonoperative patients and in 95% of those treated surgically.
Isolated acromial fractures
The acromial process extends laterally from the scapular spine and then anteriorly. Its medial border is defined by a line that courses perpendicular to the surface of the acromial and scapular processes and ends at the deepest point of the spinoglenoid notch. The acromial process is formed from two ossification centers: one for its anterior end and one for its posterolateral tip. The acromial process has four basic functions:
Provides one side of the AC articulation
Serves as a point of attachment for various musculotendinous and ligamentous structures
Lends posterosuperior stability to the glenohumeral joint
Serves as an important component of SSSC (the scapular-clavicular linkage)
Acromial fractures can be caused by a direct blow from the outside or a force transmitted via the humeral head. Avulsion fractures are the result of purely indirect forces occurring where musculotendinous or ligamentous structures (the deltoid and trapezius muscles and the CA and AC ligaments) attach to the acromion. Stress/fatigue fractures have been reported. , These injuries may be minimally or significantly displaced. Kuhn et al. proposed a classification scheme that prompted some discussion. They emphasized the need for ORIF if an acromial fragment is displaced inferiorly by the pull of the deltoid muscle and is compromising the subacromial space, thereby resulting in impingement symptoms and interference with rotator cuff function.
The diagnosis is radiographic. True AP and lateral views of the scapula and a true axillary projection of the glenohumeral joint detect most acromial fractures. An os acromiale can complicate the evaluation. However, on occasion, CT may be needed to precisely define the injury and disclose involvement of adjacent bony and articular structures. A weight-bearing AP projection is obtained if a disruption of the scapular-clavicular linkage (SSSC) is suspected.
Atraumatic fracture secondary to thinning of the acromion can be due to either cuff tear arthropathy with superior migration of the humeral head and acetabularization of the acromion or iatrogenic fracture after aggressive acromioplasty. ,
Although significantly displaced, isolated, nonavulsion acromial fractures have been described, , the vast majority are nondisplaced or minimally displaced. Symptomatic nonoperative care will reliably lead to union and a good to excellent functional result. However, significantly displaced injuries require surgical management. Symptomatic acromial nonunion, although uncommon, has been reported in the literature. , Iatrogenic fracture after acromioplasty has been reported ( Fig. 13.34 ).