Reverse Total Shoulder Arthroplasty

Reverse total shoulder arthroplasty (RTSA) has transformed the management of complex shoulder conditions, particularly rotator cuff arthropathy. It reverses the ball-and-socket: a convex glenosphere is fixed to the glenoid and a concave socket to the humerus, and the deltoid becomes the primary arm elevator.

Who. Use has grown exponentially over the past decade, an increase of over 300 percent, and RTSA now represents over 60 percent of all shoulder arthroplasties in some series. Mean age is 65-75 years, though indications are expanding to younger patients. The female predominance of 60-65 percent reflects the demographics of rotator cuff arthropathy.

History. The earlier reverse designs, Neer's Mark I and II, failed through glenoid loosening from eccentric loading. Professor Paul Grammont (Lyon, France) developed the modern design in 1985, and his key innovation was medialisation of the centre of rotation. Modern semi-constrained designs achieve over 90 percent ten-year survivorship with revision as the endpoint, a figure about the implant rather than the shoulder (see Outcomes and Prognosis).

Cuff tear arthropathy. Cuff tear arthropathy (CTA) is the end stage of a massive rotator cuff tear with secondary degenerative change, and it is the most common indication for RTSA. It develops as a cascade:

1. A massive rotator cuff tear, usually of supraspinatus and infraspinatus
2. Loss of the force couple, so the deltoid pulls the humeral head superiorly unopposed
3. Superior migration, with the head articulating with the undersurface of the acromion
4. Mechanical change: increased joint reaction forces and altered synovial fluid
5. Cartilage destruction on both the glenoid and the humeral head
6. Bony remodelling: femoralisation of the humeral head and acetabularisation of the glenoid

The Grammont principles. Grammont answered the failures of the earlier reverse designs with two moves. Moving the centre of rotation from the lateral humeral head to the glenoid surface (medialisation) eliminates the moment arm that caused glenoid loosening, reducing eccentric loading on the glenoid fixation by over 90 percent, and increases the deltoid moment arm by 30-40 percent. Lengthening the arm by 1-3cm (distalisation) tensions the deltoid and converts it from a short, relatively weak elevator into an efficient one.

What it restores. Elevation is deltoid-powered and is restored reliably. Most patients have limited active external rotation afterwards, because the posterior cuff, infraspinatus and teres minor, is deficient; if the teres minor is intact, external rotation is preserved, and a latissimus dorsi transfer can improve it in select cases (see Restoring Active External Rotation).

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History. Pain is anterolateral and may radiate to the deltoid. Night pain is common, with difficulty sleeping on the affected side, and overhead activity and reaching hurt; the course is often chronic and progressive over years. Active elevation is severely limited (pseudoparalysis), so the patient cannot comb their hair or reach overhead. Ask what has already failed: injections, physiotherapy, cuff repair.

Examination. The findings in cuff tear arthropathy:

• Inspection: deltoid atrophy is rare, and if present reconsider RTSA; anterior prominence from superior humeral migration
• Palpation: anterior shoulder tenderness; the AC joint is often arthritic
• Active range: severely limited elevation, pseudoparalysis below 90 degrees
• Passive range: preserved, which excludes frozen shoulder
• Strength: positive Hornblower's sign and external rotation lag

Differential diagnosis. The table sorts the painful, weak, elevation-limited shoulder by active against passive range and by the feature that distinguishes each cause.

The deltoid before anything else. RTSA is deltoid-powered, so inspect deltoid bulk for atrophy, test sensation over the lateral shoulder and deltoid strength against resisted abduction, and read the old incisions for a previous deltoid detachment. Obtain EMG and nerve conduction studies if any of this is concerning, and document the findings preoperatively, which carries medicolegal importance.

Radiographs. A standard shoulder series is first line: AP in neutral, internal and external rotation, a scapular Y and an axillary lateral. Assess:

• The acromiohumeral interval and superior migration of the humeral head
• Femoralisation (rounding) of the humeral head
• Acetabularisation of the acromion and glenoid
• Severity of glenohumeral arthritis
• Acromioclavicular joint arthritis

CT with 3D reconstruction. CT is essential for RTSA planning, because it shows the glenoid version, bone stock and the best baseplate trajectory. Look at:

• Bone stock anteriorly, posteriorly and inferiorly
• Version: excessive retroversion, over 15 degrees, may need bony increased offset (BIO) augmentation or a posteriorly augmented baseplate
• Erosion pattern, centred or decentred (Seebauer)
• Vault depth and screw trajectory; the inferior screw trajectory must be planned to avoid the scapular spine
• Prior hardware at revision

MRI. Not essential if the diagnosis is clear, but useful for teres minor integrity, which predicts postoperative external rotation, for Goutallier grading of fatty infiltration, for subscapularis status (repair or leave), for biceps pathology, and to exclude infection at revision.

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The decision. The core indication is cuff tear arthropathy with pseudoparalysis, and every indication requires intact deltoid function; this is non-negotiable. The established indications:

• Cuff tear arthropathy with pseudoparalysis: Hamada 4 and 5 are the primary indication, and grade 3 is a candidate if symptomatic
• Massive irreparable rotator cuff tear with pseudoparalysis, without arthritis
• Proximal humerus fracture in the elderly (over 70), comminuted, with poor bone quality
• Failed hemiarthroplasty with cuff deficiency or tuberosity non-union

Indications have expanded to:

• Revision of a failed anatomic TSA with cuff deficiency
• Rheumatoid or other inflammatory arthritis with a massive cuff tear or cuff deficiency
• Tumour reconstruction of the proximal humerus
• Fracture sequelae (malunion, nonunion)

Contraindications. Absolute:

• Deltoid dysfunction (paralysis, severe atrophy)
• Axillary nerve palsy
• Active infection
• Significant medical comorbidities precluding surgery

Relative:

• Young age (under 60), because of high revision risk over a lifetime; weigh risk and benefit carefully
• Prior deltoid detachment (lateral approach with poor repair)
• Severe glenoid bone loss, which may need bone graft or a custom implant
• Charcot arthropathy
• Non-compliance with postoperative restrictions

Conservative management first. Activity modification and analgesia, physiotherapy for the remaining muscles (deltoid and periscapular), and subacromial, glenohumeral or AC joint injections for symptomatic relief. Its role is limited in cuff tear arthropathy with pseudoparalysis.

When to operate. After at least 3-6 months of failed conservative management, with significant functional impairment (pseudoparalysis) or uncontrolled pain affecting quality of life, in an elderly patient willing to accept activity restrictions. In appropriately selected patients RTSA provides reliable pain relief and functional improvement.

Lifelong restrictions. Avoid lifting greater than 10-15kg, because of the risk of acromial stress fracture and instability, and avoid contact sports and high-impact activity. Swimming, golf and tennis are often possible at low demand.

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Function. Forward elevation improves from a mean of 50 degrees to 120-140 degrees. External rotation is often limited, 0-30 degrees on average, and internal rotation is variable, often reaching the sacrum or buttock. Strength improves on the preoperative pseudoparalysis, and pain relief is excellent in over 90 percent of patients.

Survivorship depends on the endpoint. In Guery's cohort of 80 prostheses, implant survival with revision as the endpoint was 91 percent at 120 months, and 84 percent with glenoid loosening as the endpoint.

Function fails first. With an absolute Constant score under 30 as the endpoint, survival in the same cohort was 58 percent at 120 months, a figure that did not differ by aetiology.

Quote both or neither. Roughly two in five shoulders had failed functionally by ten years while the prosthesis was still in situ. A survivorship figure over 90 percent describes a prosthesis that has not been taken out, not a working shoulder, and the gap between the two curves is the honest long-term result of this operation. Guery's curve had two inflections: one at about three years from early loosening, and a second from about six years reflecting progressive functional deterioration.

The long term. Revision rates are higher in younger patients (under 60). Glenoid loosening is a long-term concern with medialised designs, and lateralised designs may have improved long-term outcomes, which remains under investigation.

Predictors of a good outcome.

• Intact teres minor (better external rotation)
• Adequate deltoid function preoperatively
• Patient understanding of activity restrictions
• Primary indication (CTA) rather than complex revision
• Surgeon experience with the RTSA technique

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The gap a reverse leaves. A reverse restores elevation but not external rotation. The established solution is to combine it with a modified L'Episcopo transfer: the latissimus dorsi and teres major are detached, rerouted around the humerus and reattached posterolaterally, converting these internal rotators into active external rotators. Boileau popularised performing both the reverse and the transfer through a single deltopectoral approach in the beach-chair position, avoiding the classic two-incision posterior dissection.

Choosing the operation. The two patterns are named for what has been lost:

• CLEER, combined loss of active elevation and external rotation (an irreparable postero-superior cuff plus loss of teres minor, in cuff tear arthropathy or tumour reconstruction), is the indication for the combined reverse plus transfer. Clinically it is the patient with a positive Hornblower and a dropping arm from an absent teres minor.
• ILER, isolated loss of external rotation with preserved elevation, can be treated by the transfer alone, without a reverse.

What the patient gains. The transfer restores the ability to control the spatial position of the arm, external rotation with the arm at the side, which is the main driver of patient satisfaction, rather than adding elevation.

Measuring the tilt. Inferior tilt of the baseplate and a low glenosphere are measured, and two radiographic parameters quantify them:

• RSA angle (Boileau): the inclination of the glenoid baseplate relative to the floor of the supraspinatus fossa (the scapular reference line). Cuff tear arthropathy glenoids are frequently superiorly inclined, and leaving that superior tilt is a leading driver of notching. The target is a neutral inclination, an RSA angle under 5 degrees, obtained by inferior reaming, an inferiorly tilted or augmented baseplate, and lowering the baseplate on the glenoid.
• Prosthesis-scapular neck angle (PSNA) (Simovitch): the angle between the glenosphere and the scapular neck. Together with the height of glenosphere implantation it predicts inferior notching, and glenosphere height carries roughly eight times more influence than the neck angle.

The targets. Combine neutral or inferior inclination with inferior glenosphere overhang of more than 5 mm and a low baseplate position. Lowering the sphere is the single most powerful preventive step; persistent superior inclination and a high or flush glenosphere are the malpositions most strongly linked to notching in long-term data.

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Global Epidemiology and Utilization:

• RTSA utilization has grown several-fold over the past two decades and is now the most common shoulder arthroplasty in many high-income health systems
• It overtook anatomic TSA in the US around the late 2010s and continues to expand into fracture and revision indications
• Mean age at surgery is typically 70-75 years with a female predominance (around 60-65 percent), mirroring cuff tear arthropathy demographics

Related pages: Rotator Cuff Arthropathy is the disease this operation was invented for and the page that carries the Hamada staging in full; Rotator Cuff Tears for the reparable end of the spectrum, and the judgement about reparability that decides whether a patient reaches this page at all; Total Shoulder Arthroplasty (Anatomic) for the alternative that requires a competent cuff and fails by rocking-horse glenoid loosening without one; Shoulder Arthroplasty Complications and Revision Shoulder Arthroplasty for instability, infection and the revision setting in which Boileau found complications ran at 47 percent rather than 5; Proximal Humerus Fractures for the acute fracture indication tested in the Sebastia-Forcada trial carded above; and Latissimus Dorsi Anatomy for the muscle transferred in the modified L'Episcopo procedure described here.

RTSA is a young procedure with rapidly evolving design philosophy. Examiners reward candidates who can discuss genuine controversy rather than recite dogma.