Shoulder replacement for arthritis: which kind, and why

Two designs

The shoulder is a ball at the top of the arm bone resting against a shallow socket on the shoulder blade. Its shape does little to hold it together. The rotator cuff does that: four tendons wrap around the ball and keep it centred while the larger deltoid muscle lifts the arm.

• An anatomic replacement, the total shoulder replacement, keeps that arrangement. The worn ball is replaced with a metal one on a stem, and the socket is lined with plastic. It needs a working rotator cuff to keep the new ball in place.
• A reverse shoulder replacement swaps them round. The ball is fixed to the shoulder blade and the socket to the arm, which moves the pivot point so the deltoid can lift the arm on its own, with no cuff at all.

The rotator cuff decides

If the cuff is intact and working, an anatomic replacement is usually the better operation, because it gives back more movement. If the cuff is torn beyond repair, an anatomic replacement fails. With nothing holding it down, the ball rides upwards, wears the socket unevenly, and the pain comes back, sometimes within a few years. That shoulder needs a reverse replacement.

So before recommending either, I need to know the state of the cuff. Part of that comes from examination, testing each tendon's strength in turn. The rest comes from imaging. A CT scan shows how much of the socket has worn and at what angle, which matters for placing the implant. An MRI or ultrasound shows the cuff when the examination leaves doubt.

A few other things push towards a reverse replacement even when the cuff looks reasonable: a socket worn badly at the back, a fracture of the top of the arm bone in an older patient, or a thin cuff in someone in their late seventies, which is likely to tear in the years ahead. That last one is a judgement made shoulder by shoulder.

What each gives back

Both relieve pain well, and pain is why most people have either. The difference is in movement.

• After an anatomic replacement, rotation and overhead reach come back more fully, because the muscles that make those movements still work. Combing your hair, reaching behind your back and fastening clothes generally become possible again.
• After a reverse replacement, lifting the arm forwards and out to the side improves a great deal, often in a shoulder that could not be lifted at all. Rotation stays limited, so reaching a back pocket, tucking in a shirt or fastening a bra behind you may stay awkward. The limit comes from the design and does not improve with time.

After a reverse replacement, heavy lifting is restricted for good: as a rule, nothing much over five kilograms with that arm.

How long they last

An anatomic replacement in a well-chosen shoulder commonly lasts fifteen to twenty years or more. Its weak points are the plastic socket loosening over the years and the cuff tearing later on. If the cuff gives way, the shoulder can be converted to a reverse replacement, and that is a well-established operation.

A reverse replacement commonly lasts ten to fifteen years or more. Revising one is harder than revising an anatomic replacement, so it is mostly an operation for older patients.

The operation and the first months

Both are open operations, done through an incision at the front of the shoulder, under general anaesthesia with a nerve block that numbs the arm for the first hours afterwards. Most people are in hospital for two to four days.

The arm is in a sling for about three weeks, with gentle assisted movement from early on. From three to six weeks you move it yourself below shoulder height, and from six weeks you work overhead and start light strengthening. Strength and movement keep improving through most of the first year.

Plan for a few practical things. Sleeping is easier propped up on pillows for the first weeks, and the sling stays on at night. You will need help with dressing, bathing and cooking at first. Driving waits until you are out of the sling and can control the wheel with both hands, which for most people is around six weeks.

How I approach it

Shoulder replacement of both kinds was part of my shoulder fellowship at Seoul National University Bundang Hospital in South Korea. The first thing I want to know about an arthritic shoulder is whether the cuff is working. The answer usually settles which operation, and I will go through your own scans with you to show why.

Not every arthritic shoulder needs replacing. Many are managed for years with exercises, pain relief and the occasional injection. If your shoulder hurts and you are not sure it is arthritis, shoulder pain covers the commoner causes. A torn cuff in a healthy joint is stitched back instead, by keyhole rotator cuff repair. And if you cannot tell whether a painful shoulder is stiff or weak, frozen shoulder or rotator cuff tear explains the quick test that separates them.

Further reading

• American Academy of Orthopaedic Surgeons, OrthoInfo: Arthritis of the shoulder.
• American Academy of Orthopaedic Surgeons, OrthoInfo: Shoulder joint replacement.
• American Academy of Orthopaedic Surgeons, OrthoInfo: Reverse total shoulder replacement.

Common questions