Rotator Cuff Tear Arthropathy: Pathophysiology ...

M u s c u l o s k e l e t a l I m a g i n g • R ev i ew Eajazi et al. Rotator Cuff Tear Arthropathy

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Musculoskeletal Imaging Review

Rotator Cuff Tear Arthropathy: Pathophysiology, Imaging Characteristics, and Treatment Options Alireza Eajazi1 Steve Kussman2 Christina LeBedis1 Ali Guermazi1 Andrew Kompel1 Andrew Jawa3 Akira M. Murakami1

OBJECTIVE. The purpose of this article is to review the biomechanical properties of the rotator cuff and glenohumeral joint and the pathophysiology, imaging characteristics, and treatment options of rotator cuff tear arthropathy (RCTA). CONCLUSION. Although multiple pathways have been proposed as causes of RCTA, the exact cause remains unclear. Increasing knowledge about the clinical diagnosis, imaging features, and indicators of severity improves recognition and treatment of this pathologic condition.

Eajazi A, Kussman S, LeBedis C, et al.

he shoulder has the most mobility but the least intrinsic stability of all joints in the human body [1]. A complex association of static and dynamic stabilizers balances the joint’s mobility with its functional stability. The rotator cuff tendons play a crucial role in maintaining this dynamic stability in the naturally unstable glenohumeral joint [2, 3]. The loss of this important stabilizer can lead to a complex pattern of joint degeneration referred to as rotator cuff tear arthropathy (RCTA). Understanding the role of the rotator cuff in maintaining the balance between mobility and stability leads to an appreciation of the progressive findings seen in RCTA and the treatment options that are available if arthropathy progresses to joint failure. In 1977, Charles Neer and his colleagues invented the term “cuff tear arthropathy” and eventually provided the first detailed description of RCTA in 1983 [4]. RCTA has three major characteristics: first, massive rotator cuff tear (Fig. 1A); second, degenerative changes (i.e., glenoid erosion, loss of articular cartilage, osteoporosis of the humeral head, and eventually humeral head collapse) (Figs. 1B and 1C); and third, superior migration of the humerus resulting in “femoralization” of the humeral head (Fig. 2A) and “acetabularization” of the coracoacromial arch [5] (Fig. 2B). Understanding the imaging findings and stages of RCTA is important in the preoperative evaluation of the patient with a symptomatic massive rotator cuff tear because

Keywords: arthropathy, biomechanics, imaging, MRI, rotator cuff tear, shoulder DOI:10.2214/AJR.14.13815 Received September 3, 2014; accepted after revision April 27, 2015. 1 Department of Radiology, Boston University Medical Center, 820 Harrison Ave, FGH Bldg, 3rd Fl, Boston, MA 02118. Address correspondence to A. Eajazi ([email protected]). 2 Department of Radiology, University of California, San Diego, San Diego, CA. 3

Boston Sports and Shoulder Center, New England Baptist Hospital, Boston, MA.

WEB This is a web exclusive article. AJR 2015; 205:W502–W511 0361–803X/15/2055–W502 © American Roentgen Ray Society

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this information can be used to determine the proper surgical treatment of end-stage arthropathy and to provide patients with realistic expectations about the postoperative outcome. The objectives of this article are to review the biomechanical properties of the rotator cuff and glenohumeral joint and their relationship to the pathophysiology of RCTA. We will discuss the various imaging modalities and classification systems for the diagnosis of RCTA and will review the current management options for treatment. Biomechanics of Shoulder The glenohumeral joint lacks intrinsic osseous constraints, which allows a high degree of mobility but simultaneously creates inherent instability. This instability is compensated for by many static stabilizers, such as the labrum, joint capsule, and glenohumeral ligaments. The dynamic stabilizers of the rotator cuff—which consist of the supraspinatus, infraspinatus, teres minor, and subscapularis muscles—are crucial. These muscles provide stability through a mechanism termed “concavity compression” [6–8] (Fig. 3). The forces acting on the shoulder can be divided into three components: a stabilizing compressive force, a destabilizing translational superior-inferior force, and an anteriorposterior force. Joint stability is simply a balanced ratio between the translational forces in any direction and the compression forces [9–11]. For instance, the combined force of the subscapularis muscle anteriorly and the infraspinatus and teres minor muscles poste-

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Fig. 1—MRI of rotator cuff tear arthropathy. A, Coronal proton density–weighted MR image of 73-year-old woman shows massive rotator cuff tear. B, Coronal proton density–weighted MR image of 69-year-old woman shows chronic superior migration of humeral head (arrow) resulting in full-thickness chondral loss, osteophyte formation, and subchondral cystic changes over superior humeral head and superior glenoid. C, T2-weighted fat-suppressed MR image of right shoulder of 58-year-old woman shows chronic superior migration of humeral head resulting in degeneration and maceration of superior labrum (arrowhead).

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Fig. 2—Radiography of rotator cuff tear arthropathy. A, Frontal radiograph of right shoulder of 73-year-old woman shows femoralization of humeral head and erosion of greater tuberosity (arrowhead). B, Frontal radiograph of left shoulder of 87-year-old man shows acetabularization of coracoacromial arch— that is, reshaping of coracoacromial arch to create socket for superior aspect of humerus (arrow).

riorly provide antagonistic forces that compress the humeral head onto the glenoid bone [3, 12]. This stability also depends on the effective glenoid arc and the area of the glenoid’s articular surface available for humeral head compression [13]. Also important is the interplay between the deltoid muscle and the rotator cuff. The rotator cuff provides a net inferiorly directed and compressive force, whereas the strong deltoid muscle provides a superiorly directed force; these forces result in a net force balance or force coupling of the glenohumeral joint [14] (Fig. 4A).

Massive Rotator Cuff Tear There is no general agreement regarding the definition of a “massive” rotator cuff tear, although its prevalence has been reported in the literature to range from 10% to 40% of all rotator cuff tears [15–17]. Both functional and anatomic characteristics have been used to classify massive rotator cuff tears, but each type of characteristics has some disadvantages. Cofield et al. [18] defined a massive rotator cuff tear as a cuff tear with a diameter of 5 cm or larger, whereas Zumstein et al. [19] defined it as complete detachment of two or more ten-

dons. Other investigators have proposed classification systems based on the area of the defect or on indexes of tear dimensions [20]. Despite the different criteria used to define a massive rotator cuff tear, the result of a massive rotator cuff tear is the destabilization of the glenohumeral joint and the attritional destruction of the primary static stabilizers, leading to chondral wear and subsequent osteoarthritis [21]. It is noteworthy that massive rotator cuff tears, although technically challenging to repair, are not necessarily irreparable [22]. Signs of irreparability include static superior migration of the humeral head, a narrowed or absent acromiohumeral interval (AHI), and fatty infiltration affecting 50% or more of the rotator cuff muscles [16, 17, 23, 24]. Pathogenesis of Rotator Cuff Tear Arthropathy The exact cause of RCTA is unknown, although numerous pathomechanical concepts have been hypothesized for its development. Crystal-Mediated Theory An association between RCTA and the presence of calcium phosphate crystals in synovial fluid and tissue was proposed by Halverson et al. [25]. They postulated that the calcium phosphate–containing crystals in synovial tissue induce an immunologic cascade that leads to the release of proteolytic enzymes and that these proteolytic enzymes

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Eajazi et al. the glenoid bone is often eccentric, involving the anterior-superior margin. This wear leads to an accelerated process of further cuff destruction and arthropathy (Fig. 4B). Nutritional factors—The nutritional factors associated with massive full-thickness tears are related to the loss of motion and periarticular damage due to disruption of the normal joint milieu. The loss of fluid pressure and the accompanying reduction in the quality of the chemical content of the synovial fluid lead to cartilage and bone atrophy. Recurrent bloody effusions and the loss of glycosaminoglycan content of the cartilage further accelerate the destruction of both bone and soft tissue [27]. Fig. 3—Drawing shows concavity-compression mechanism (triple-headed arrow) of rotator cuff: Rotator cuff muscles (single-headed arrows) provide joint stability and center humeral head on glenoid cavity. (Drawing by Murakami AM)

cause the rapid degradation of the cartilage matrix components and the destruction of periarticular and articular structures [26]. Rotator Cuff Tear Theory Neer et al. [21] hypothesized that massive rotator cuff tears lead to the degeneration of the shoulder joint through two mechanisms: a mechanical pathway and a nutritional pathway. This concept is based on clinical observations and pathologic observations made at surgery and on review of histologic samples.

Mechanical factors—The mechanical factors associated with massive rotator cuff tears lead to unbalanced muscle forces. These factors are anteroposterior instability of the humeral head, resulting from massive cuff tears and rupture or dislocation of the long head of the biceps tendon, which leads to superior migration of the humeral head and acromial impingement. Shoulder joint wear occurs as a result of repetitive trauma from the altered biomechanics associated with the loss of primary and secondary stabilizers. The wear on

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Force Couple Theory The deltoid and rotator cuff muscles work cooperatively to preserve a balanced force couple for the glenohumeral joint in both the coronal and transverse planes. The muscles inferior to the humeral head equator maintain a balanced coronal force, whereas the subscapularis and infraspinatus–teres minor complex balance each other in the transverse plane. In this capacity, the rotator cuff muscles function as primary dynamic stabilizers to maintain a concentric reduction during rotation of the humeral head on the glenoid bone [28–31]. A massive rotator cuff tear can disrupt this force couple, as shown fluoroscopically by Burkhart et al. [14] in comparisons of the kine-

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Fig. 4—Rotator cuff. (Drawings by Murakami AM) A, Rotator cuff biomechanics. Drawing shows that net inferior and compressive force vector (double-headed arrow) of rotator cuff is balanced by net superiorly directed force vector of deltoid muscle (single-headed arrow). B, Rotator cuff insufficiency. Drawing shows superior migration of humeral head and degenerative changes of glenohumeral joint (arrow) that are suggestive of rotator cuff insufficiency.

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Rotator Cuff Tear Arthropathy matic patterns of massive rotator cuff tears. As a result, the uncoupled or unopposed deltoid muscle leads to superior migration of the humeral head, which in turn results in the distinctive degenerative wear pattern on the acromion and coracoid process. Additionally, the uncoupling leads to instability and reduced motion, which lead to chondral loss. Fatty degeneration of the rotator cuff muscles, which occurs after a rotator cuff tear, is characterized by atrophy of the muscle fibers, fibrosis, and fatty accumulation within and around the muscles [32, 33]. It is frequently associated with an aging-related reduction of the regenerative potential of the rotator cuff tendons [34]. Studies have shown that lowgrade preoperative fatty degeneration may predict a better clinical outcome [32, 33], whereas high-grade infiltration is associated with a worse clinical outcome [35, 36]. A delayed diagnosis of a rotator cuff tear also worsens the prognosis because both the tendon and muscle belly undergo atrophy and degeneration [37]. Fatty infiltration and muscle atrophy have also been shown to not improve after successful structural repair of the rotator cuff, and their presence is associated with poor functional results [32, 38–40]. The risk of irreversible fatty infiltration of the rotator cuff muscles may limit future treatment options and must be considered when counseling patients. This event has a negative influence on both functional and radiographic outcomes [41]. Diagnostic Imaging Radiography A few classification systems based on radiography have been developed to define the bone changes that occur in RCTA. Although the characteristics of these systems overlap, each system focuses on a different set of findings associated with the disorder. These systems include the Seebauer system [27] and the Hamada system [42]. The Seebauer classification system separates RCTA into four distinct types: IA, IB, IIA, and IIB [27]. Each type is characterized by a massive rotator cuff tear, a distinctive level of joint instability, humeral head translation, and articular surface erosion [27]. This classification system is a biomechanical description of RCTA, in which each type is distinguished on the basis of the degree of superior migration of the humeral head from the center of rotation and the amount of instability [27]. The extent of decentralization seen on radiographs depends on the size of

the rotator cuff tear, the integrity of the coracoacromial arch, and the degree and direction of glenoid bone erosion [27] (Fig. 5). The Hamada classification system describes structural changes within the coracoacromial arch and changes in the acromiohumeral interval (AHI) on anteroposterior radiographs as the bases for classification [43]. This system divides massive rotator cuff tears into five radiographic stages, with consecutive stages indicating disease progression [42]. Table 1 shows the characteristics of each of the stages in this system. MRI The multiplanar imaging capabilities of MRI combined with its excellent soft-tissue contrast make it ideally suited for imaging the rotator cuff. Although a massive rotator cuff tear can often be diagnosed on the basis of physical examination and advanced radiographic findings as detailed earlier, MRI can be used to evaluate the integrity of the cuff overall or to determine whether an existing tear is repairable when other findings are ambiguous. Additionally, MRI can assist in the characterization of chondral loss that can be typical of RCTA. CT The primary use of CT in patients with advanced osteoarthritis of the glenohumeral joint has been in the assessment of the glenoid bone. In particular, advanced osteoarthritis can be associated with posterior glenoid bone loss, which can inevitably lead to posterior subluxation of the humeral head. These findings are associated with a poor clinical outcome after total shoulder arthroplasty (TSA) [44]. Accurate assessment of the glenoid bone stock is also important in surgical planning because a small volume of

bone may require bone grafting to accommodate the glenoid prosthesis [45]. CT has been shown to be more effective than radiography in this assessment and in the measurement of glenoid version [46]. Glenoid version is defined by Friedman et al. [47] as the angle between a line drawn from the medial border of the scapula to the center of the glenoid bone and the line perpendicular to the face of the glenoid bone on the axial 2D CT slice at or just below the tip of the coracoid process. Both CT and MRI can be used to assess the degree of fatty infiltration according to the classification system proposed by Goutallier et al. [33]. They first described a classification system based on the presence of fatty streaks within the muscle belly on CT, but the grading criteria have since been applied to MRI [37, 48]. The classification system that Goutallier et al. [33] described in their original article in 1994 is composed of five stages of fatty infiltration (Fig. 6 and Table 2). Sonography Sonography is an alternative modality for evaluating the rotator cuff that is capable of providing images with high image contrast but without the use of ionizing radiation. The diagnostic accuracy of shoulder sonography for rotator cuff tears can reach as high as 91% and 100% for partial- and full-thickness tears, respectively [49–51]. Although the accuracy of sonography hinges on the skill and experience of the operator performing the examination [52], sonography is a suitable alternative modality in patients who are not able to undergo MRI because it is contraindicated or cannot be tolerated. Management Patients presenting with RCTA present with pain, disability, or both. Numerous treatment

TABLE 1: Classification System for Assessing Rotator Cuff Tear Arthropathy (RCTA) on Radiography According to Hamada et al. [42] Stage of RCTA

Characteristics

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AHI is ≥ 6 mm

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AHI is ≤ 5 mm

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AHI is ≤ 5 mm and there is acetabularization of the coracoacromial arch

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Glenohumeral joint is narrowed 4a

Without acetabularization

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With acetabularization

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Humeral head osteonecrosis is present and eventually results in humeral head collapse

Note—AHI = acromiohumeral interval.


Eajazi et al. TABLE 2: Classification System for Assessing Fatty Infiltration of Rotator Cuff Muscles on Imaginga According to Goutallier et al. [33]

Surgical Options Total shoulder arthroplasty—TSA is most commonly performed for the treatment of

advanced degenerative osteoarthritis in patients older than 60 years [54]. Other indications include inflammatory arthritis, humeral head avascular necrosis with secondary glenohumeral arthritis, postinfectious arthritis, and Charcot arthropathy [54, 55]. Unconstrained TSA prostheses were used by Neer et al. [4, 21] to treat 26 shoulders with RCTA and yielded poor functional outcomes. The poor outcomes were thought to be related to the superior migration of the humeral head seen with a defective rotator cuff, which resulted in eccentric loading of the superior aspect of the glenoid component. Over time, this eccentric loading resulted in loosening of the glenoid component, a complication that Franklin et al. [56] termed the “rocking horse glenoid.” Constrained and semiconstrained TSA prostheses were used with the hope of preventing superior humeral head migration and thus the eccentric loading of the superior aspect of the glenoid component. Nevertheless, these prostheses still caused stresses at the superior interface of the glenoid component and therefore were also associated with high rates of glenoid component loosening [57, 58].

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Stage of Fatty Infiltration

Characteristics

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Normal muscles, no fatty streaks

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Some fatty streaks

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Fatty infiltration is present but there is more muscle than fat

3

Moderate fatty infiltration is present in which there is as much fat as muscle

4

Severe fatty infiltration is present in which there is more fat than muscle

aCT or MRI.

options are available, and the treatment of choice varies according to the patient’s circumstances, surgeon’s preferences, and resources. Initial Management The initial management of RCTA should begin with conservative measures including activity modification, oral analgesics including nonsteroidal antiinflammatory drugs or cyclooxygenase inhibitors, physical therapy, fluid aspiration, and intraarticular injections of corticosteroid and hyaluronans. Aspiration and corticosteroid administration may be a useful adjunct to

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physical therapy for patients who are unable or unwilling to undergo surgical intervention. Intraarticular corticosteroid injections may be useful at first, but multiple injections are not recommended because of decreasing utility and the possibility of increasing the risk of infection [53]. Although the initial management of RCTA should begin with conservative measures, surgical intervention is often required.

Fig. 5—Radiographs show examples of types of rotator cuff tear arthropathy (RCTA) according to Seebauer classification system [27]. A, 58-year-old man with type IA RCTA. Type IA is characterized as centered and stable. Imaging findings are intact anterior restraints, minimal superior migration, femoralization, and acetabularization. B, 74-year-old woman with type IB RCTA. Type IB is characterized as centered and medialized. Imaging findings are intact anterior restraints, minimal superior migration, and medial erosion of glenoid bone. C, 87-year-old man with type IIA RCTA. Type IIA is characterized as decentered, limited, and stable. Imaging findings are compromised anterior restraints, superior translation, minimal stabilization by coracoacromial arch, and superior and medial erosions of glenoid bone. D, 68-year-old man with type IIB RCTA. Type IIB is characterized as decentered and unstable. Imaging findings are incompetent anterior structures, anterior-superior escape, and no stabilization by coracoacromial arch.




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Humeral hemiarthroplasty—Humeral hemiarthroplasty is now a current treatment option for patients with symptomatic RCTA and modest functional goals [53, 59–62]. The benefits of humeral hemiarthroplasty are a shorter and technically easier surgery: Repair of the rotator cuff is easier because of less humeral lateralization [58], and the lack of a glenoid component eliminates the potential complication of component loosening. Humeral hemiarthroplasty also avoids the problem of the rocking horse glenoid. The results from several studies have shown no pain or mild pain in 47–86% of shoulders with glenohumeral arthritis and a deficient rotator cuff treated with humeral hemiarthroplasty [53, 59–61]. Active forward elevation of the glenohumeral joint was also found to increase by an average of 17–50° after humeral hemiarthroplasty [53, 59–61]. Based on the “limited-goals” criterion proposed by Neer et al. [4, 21], between 63% and 86% of humeral hemiarthroplasties were considered to have successful outcomes [53, 59, 61]. However, studies have shown that a significant number of patients are left with painful and unsatisfactory shoulders after humeral

hemiarthroplasty, even though this surgical option helped many patients and was preferable to TSA [53, 61, 63]. Reverse total shoulder arthroplasty— RCTA is currently the primary indication for reverse TSA, as this group has reported predictable outcomes [64]. The ideal candidate for reverse TSA is an older patient with decreased functional demand, a preoperative active forward elevation of the glenohumeral joint of less than 90°, and an intact deltoid muscle. As surgeons have gained more experience with reverse TSA, the indications have been expanded to include revision arthroplasty, inflammatory arthropathy with a massive rotator cuff tear, painful and irreparable rotator cuff tear, proximal humeral nonunion or malunion, acute fractures, tumor, and chronic pseudoparalysis without arthritis [65–75]. A reverse TSA is essentially a reversal of the normal shoulder ball-and-socket anatomy. In this design, the concave component replaces the humeral head, and the convex component is fixed to the glenoid bone, which results in a “humerosocket” and a “glenosphere.” It is composed of three main components: the baseplate (metaglene), the

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Fig. 6—Stages of fatty infiltration of rotator cuff muscles according to classification system proposed by Goutallier et al. [33]. A, MR image of 33-year-old woman shows stage 0 fatty infiltration. B, MR image of 74-year-old man shows stage 1 fatty infiltration. C, MR image of 58-year-old woman shows stage 2 fatty infiltration. D, MR image of 73-year-old woman shows stage 3 fatty infiltration. E, MR image of 58-year-old man shows stage 4 fatty infiltration.

glenosphere, and the humeral socket. The baseplate is a metal-backed plate that directly contacts the glenoid bone (Fig. 7). This design results in a semiconstrained prosthesis that stabilizes the glenohumeral center of rotation like a functioning rotator cuff [76]. This design avoids the superior migration of the humerus on the glenoid bone, thereby restoring the deltoid muscle’s anatomic resting length. The deltoid muscle now can compensate for the rotator cuff deficiency. By replacing both sides of the joint, reverse TSA offers more reliable pain relief than humeral hemiarthroplasty [59]. Multiple series of patients with RCTA that was treated using reverse TSA have shown substantial improvements in Constant-Murley scores, an average active forward elevation of the glenohumeral joint of greater than 110°, and good long-term joint stability [77– 81]. Furthermore, a faster recovery may be achieved because the rotator cuff does not need to be protected during the early postoperative period [82]. Several clinical studies have also reported noticeable improvements in activity and quality of life after a successful reverse TSA [65, 78, 81, 83, 84].



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Fig. 7—Reverse total shoulder arthroplasty (TSA). A, Drawing shows anatomy after reverse TSA: “Ball” is at glenoid, and “socket” is on humeral head. Axis is moved medially and distally to allow control by deltoid muscle. Arrow shows restored center of rotation. (Drawing by Murakami AM) B, Radiograph of 74-year-old woman who underwent reverse TSA of right shoulder shows prosthesis. C, Photograph shows reverse TSA prosthesis.

Arthrodesis—Another surgical option is glenohumeral arthrodesis, which has the goal of relieving pain by eliminating motion. The most noticeable disadvantage of this procedure is the total loss of glenohumeral joint motion. Additionally, the compensatory scapulothoracic motion may expose the acromioclavicular joint to excessive motion and result in further pain [91, 92]. Despite these drawbacks, some patients may benefit from glenohumeral arthrodesis. Patients with multiple failed previous operations, a history of infection, or a deficient anterior deltoid muscle may have the best outcomes with glenohumeral arthrodesis [93].

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Although abundant long-term data are not available, short- to intermediate-term outcome studies suggest that survivorship of

the reverse TSA is comparable with humeral hemiarthroplasty and TSA [78, 81, 85–90].

Fig. 8—Complications of reverse total shoulder arthroplasty (TSA): dislocation and stress fracture. A, Frontal radiograph of left shoulder of 69-year-old woman shows dislocation of components of reverse TSA prosthesis. B, Frontal radiograph of left shoulder of 73-year-old man shows acromial stress fracture (arrowhead) due to reverse TSA prosthesis.

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Complications Despite favorable short- and medium-term clinical results, the overall complication rate of reverse TSA is high, ranging between 19% and 68% depending on what is considered to be a complication [94]. Wall et al. [79] reviewed the results of reverse TSA according to cause and reported a 19% complication rate in 186 patients, with the most common complications being dislocation (7.5%) (Fig. 8A) and infection (4%). Glenoid fractures, humeral fractures, pain, radial nerve palsy, and loosening of the glenosphere or baseplate were among the least commonly reported complications. It is impor-




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Fig. 9—Complication of reverse total shoulder arthroplasty (TSA): scapular notching. A, Drawing shows Nerot-Sirveaux grading system (grades 1–4) for characterizing postoperative scapular notching after reverse TSA. (Drawing by Murakami AM) B, Radiograph of left shoulder of 69-year-old woman who underwent reverse TSA shows grade 4 scapular notching.

tant to understand that the risk of complications in the revision surgeries was more than double that observed with primary surgeries (37% and 13%, respectively) [79]. Instability is one of the other complications that may be related to undertensioning of the deltoid muscle, deltoid insufficiency or detachment, or medial impingement of the humeral component on the scapular neck [79]. Overtensioning of the deltoid muscle, however, can lead to fracture of the acromion, especially in elderly patients with osteoporosis [95] (Fig. 8B). Given the dead space surrounding the prosthesis, there is a substantial risk of postoperative hematoma formation and deep infection [78]. Another common complication is scapular notching, which is due to the impingement of the medial aspect of the humeral cup on the scapular neck during adduction [96–100]. The incidence of scapular notching has been reported to be as high as 96% [78]. A classification system proposed by Sirveaux et al. [43] in 2004 to grade scapular notching is illustrated in Figure 9. In grade 1 of this classification, notching involves only scapular bone. Grade 2 notching contacts the inferior screw of the baseplate. Grade 3 notching extends to the superior aspect of the inferior screw of the baseplate, and grade 4 notching extends past the superior aspect of the inferior screw of the baseplate to include the area under the baseplate. The clinical relevance of scapular notching is controversial. In some studies, significant scapular notching was associated with worse clinical outcomes and premature baseplate failure [66, 100]. Both the prevalence and severity of scapular notching are noted to increase over time [98]. Other studies have found no relation between notch-

ing and a lower Constant-Murley score, decreased range of motion, pain, or glenoid component loosening [98]. The incidence of scapular notching has been shown to depend on several factors, including the position or offset of the glenosphere. For example, the use of laterally offset glenospheres in different styles of prostheses has reduced the incidence of scapular notching to between 0% and 13% [81, 94]. Conclusion RCTA is an uncommon and challenging to treat condition. Increased knowledge about the clinical diagnosis, imaging features, and imaging and clinical indicators of severity improves recognition of this pathologic condition. Multiple pathways have been proposed as the cause of RCTA, but the exact cause remains unclear. The initial management of RCTA should begin with conservative measures, but surgical intervention is often required. The current surgical treatments of RCTA are TSA, humeral hemiarthroplasty, and reverse TSA, with reverse TSA being the most recent advancement. In patients with advanced RCTA, painful pseudoparalysis, or both, reverse TSA can provide predictable pain relief and return of function but is associated with a relatively high risk of complications. The significant complication rate underscores the importance of strict patient selection and careful operative technique and the need for design modifications to the existing arthroplasty prostheses. References 1. Bahk M, Keyurapan E, Tasaki A, Sauers EL, McFarland EG. Laxity testing of the shoulder: a re-

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