Reverse Shoulder Arthroplasty: Surgery for Cuff Tear Arthropathy

What Is Reverse Total Shoulder Arthroplasty?

Reverse total shoulder arthroplasty (rTSA) is a unique shoulder replacement design in which the normal ball-and-socket geometry is literally reversed:

A metal ball (glenosphere) is fixed to the socket side (glenoid/scapula)
A socket (polyethylene cup) replaces the humeral head

This reversal changes the mechanics of shoulder function in a way that allows the deltoid muscle — rather than the rotator cuff — to power shoulder elevation. It was specifically engineered for situations where the rotator cuff is absent or irreparably torn.

Why Reverse Rather Than Standard Replacement?

In a standard (anatomic) total shoulder replacement, the rotator cuff is essential — it centers the ball in the socket and enables arm elevation. Without a functioning rotator cuff, the humerus rides upward when you try to raise your arm, causing the implant to rock and fail.

By reversing the geometry:

The center of rotation moves medially and inferiorly
The deltoid's moment arm for elevation is increased
Deltoid function alone becomes sufficient to raise the arm overhead

This biomechanical innovation, developed by French surgeon Paul Grammont in the 1980s, transformed treatment of cuff tear arthropathy and has expanded to many other shoulder conditions.

Indications

Primary indication — Cuff Tear Arthropathy (CTA): Massive, irreparable rotator cuff tear combined with glenohumeral arthritis. The combination of missing cuff and joint destruction makes anatomic replacement unreliable.

Other indications:

Failed prior shoulder replacement requiring revision
Complex proximal humerus fractures in the elderly (some centers)
Severe rheumatoid arthritis with cuff incompetence
Tumors of the proximal humerus (oncologic reconstruction)
Irreparable cuff tears without arthritis (selected cases with pseudoparalysis — inability to raise arm)

Day of Surgery

Anesthesia: General anesthesia plus interscalene nerve block (same as anatomic TSA).

Surgical approach: Deltopectoral (same as anatomic TSA — between deltoid and pectoralis major). Typically 2–3 hours.

Key steps:

Deltopectoral approach; subscapularis assessed (may be irreparable in CTA)
Humeral head removed
Glenoid is reamed and the baseplate with central post is fixed to the scapula with screws
Glenosphere trial and final glenosphere attached to baseplate
Humeral canal prepared; polyethylene cup and stem inserted
Trial reduction: range of motion and deltoid tension checked
Final implant assembled; closure

Hospital stay: Typically 1–2 nights.

What to Expect: Outcomes

Pain relief: Excellent — comparable to anatomic TSA (>90% significant pain reduction)

Range of motion:

Forward elevation: Most patients achieve 90–130° (enough for daily activities and overhead reaching)
External rotation: Often limited; varies by remaining cuff tissue
Activities like hair combing, reaching shelves, dressing all typically achievable

rTSA does not restore normal shoulder motion — it trades some motion for reliable function in the absence of a rotator cuff.

Risks and Complications

Scapular notching: The polyethylene cup impinges on the scapular neck with arm adduction, causing bone erosion — addressed with modern implant design modifications
Dislocation: The "reverse" construct is more stable in arm-forward positions but can dislocate with extreme positions
Acromial or scapular spine stress fracture: Uncommon but important complication (the acromion experiences increased deltoid tension)
Infection (<1–2%)
Nerve injury: Axillary nerve
Implant loosening: Glenoid baseplate loosening most consequential

Recovery

Sling: 4–6 weeks
Passive motion PT: Begins at 2–4 weeks
Active motion: 6 weeks
Strengthening: 3 months
Return to functional daily activities: 3–4 months
Maximum improvement: 12–18 months (shoulder strength continues to improve for 1–1.5 years)