Mitchel D. Armstrong MD BMSc FRCSC Bandar M. Assiry MBBS SB‐orth and Ryan T. Bicknell MD MSc FRCSC Division of Orthopaedic Surgery, Department of Surgery, Queen’s University, Kingston, ON, Canada A rotator cuff tear can be classified as acute (no irreversible muscular fatty atrophy and generally reparable) or chronic (with irreversible muscular fatty atrophy and generally irreparable). Instability of the glenohumeral joint due to a long‐standing irreparable rotator cuff tear often occurs in an anterior and superior direction, called anterosuperior escape, often leading to a pseudoparalysed shoulder, generally defined as a loss of active forward elevation with maintained passive movement. These abnormalities can eventually lead to arthritic changes at both the glenohumeral and acromiohumeral articulations. Shoulder arthritis can include osteoarthritis, rheumatoid arthritis, post‐traumatic arthritis, and cuff tear arthropathy. Each type of arthritis is not infrequently seen in combination with a rotator cuff tear. A conventional anatomic total shoulder arthroplasty (TSA) is used to relieve pain and improve function in arthritic shoulders. The articular surfaces are unconstrained and allow the healthy rotator cuff and extrinsic shoulder muscles to restore shoulder function. In most arthritic shoulders, with or without a rotator cuff tear, the ball‐and‐socket biomechanics of the glenohumeral joint are maintained. However, each type of arthritis may present in combination with rotator cuff dysfunction and loss of the normal biomechanics, often leading to instability and pseudoparalysis. In this situation, the outcome of a traditional shoulder arthroplasty is substantially compromised.1–3 The incidence of rotator cuff tear dysfunction in the population of shoulder arthritis patients is difficult to determine, but occurs in a minority of patients. Although shoulder arthritis is much less common than hip or knee arthritis, the incidence and indications for shoulder arthroplasty continue to increase. Rationale In general, rTSA is an implant that provides increased stability for a shoulder that has lost, or is at increased risk of losing, its normal ball‐and‐socket function. This most commonly occurs due to soft tissue (usually rotator cuff) or bony deficiency. However, as experience with this implant increases and with newer research, the indications for rTSA are expanding. The traditional indication for rTSA has been rotator cuff tear arthropathy with pseudoparalysis in elderly low demand patients. However, indications have rapidly expanded to now include younger high demand patients, other causes of arthritis, cuff insufficiency, or impending insufficiency, as well as some types of proximal humerus fractures. RTSA may be considered when the patient presents with a clinically symptomatic, irreparable rotator cuff tear associated with anterosuperior escape and an irrecoverable pseudoparalysis. However, deltoid function must be preserved and there must be adequate glenoid bone stock to allow secure glenoid component fixation.17,18 RTSA in patients with rheumatoid arthritis is considered a reliable treatment option, with similar results to rTSA in rotator cuff arthropathy without a higher complication rate.11 The use of rTSA for cuff tear arthropathy in patients younger than 65 years of age generates some treatment controversy. However, rTSA is now emerging as a reasonable treatment option for these patients, providing subjective functional improvements, but with higher complication rates and implant longevity concerns.913–16 RTSA is also used as a revision procedure for shoulder arthroplasty associated with instability, this is associated with reasonable survival rates and higher complication rates than other indications. Instability can still remain an issue for one in seven patients.10 RTSA can be used for the treatment of complex proximal humerus fractures in elderly patients. Patients show better forward flexion and abduction, with lower revision rates when compared with hemiarthroplasty.4,12,19,20 RTSA has also been shown to be more cost‐effective when compared with hemiarthroplasty.7 There has been a dramatic increase in rTSA implant design and surgical techniques over the past 10 years. This has led to debate within the literature regarding many factors, including optimal positioning of the glenosphere and baseplate and humeral stem as well as size and design of the glenosphere. The effects of subscapularis muscle repair also show discordance within the literature. rTSA has enjoyed tremendous success considering its relatively short proliferation. This implant design provides a surgical option in difficult situations that previously were inadequately addressed with other surgical options. However, the pain and functional outcomes, survival, and complication rates have been somewhat inconsistent and concerning long term. As a result, authors have searched for implant design and technique methods to optimize the outcomes. Utilizing a lower neck‐shaft angle (135°) on the humeral component leads to a greater impingement free range of motion (ROM) and decreases the rate of scapular notching when compared with a higher angled (155°) design (p = 0.0081).30,39,40 The neck‐shaft angle does not appear to affect the rate of postoperative dislocation.35 Use of a larger diameter glenosphere (>42 mm) decreases the rate of scapular notching (p <0.001) and improves ROM (forward flexion and external rotation) (p <0.05).31,33 However, both the size of the glenosphere and the presence of notching does not appear to affect the clinical outcome at short‐term follow‐up.22,29,32 Inferior glenoid tilt of >10° does not reduce the rate of scapular notching and does not appear to confer a clinical benefit.23,30 Inferior glenoid positioning is desirable to decrease the rate of scapular notching and may improve clinical outcome scores.22,25,41,42
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Reverse Total Shoulder Arthroplasty
Clinical scenario
Relevant anatomy
Importance of the problem
Top three questions
Question 1: Among patients with shoulder pain and dysfunction, which indications, compared to others, are most relevant for reverse total shoulder arthroplasty (rTSA)?
Clinical comment
Available literature and quality of the evidence
Findings
Cuff tear arthropathy
Rheumatoid arthritis
Cuff tear arthropathy in younger patients
Failed arthroplasty
Proximal humerus fractures
Resolution of clinical scenario
Question 2: In patients undergoing rTSA, do some surgical techniques, compared to others, result in better outcomes?
Rationale
Clinical comment
Available literature and quality of the evidence
Findings
Humeral component neck‐shaft angle
Larger diameter glenosphere
Inferior glenoid component tilt and positioning
Glenoid lateralization
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