Shoulder replacement is often the suggested treatment in a patient with end-stage arthritis of the shoulder who has exhausted their non-operative treatment modalities.

Modern shoulder replacement prostheses come in two main configurations:

• Standard (or Anatomic)

• Reverse Shoulder Replacement

So what exactly is reversed in a reverse total shoulder replacement?

To understand this, we must first look at the anatomy of the normal shoulder. Often what we refer to as the shoulder joint is actually called the glenohumeral joint. The glenohumeral joint is the articulation between the glenoid cavity of the scapula (shoulder blade) and the head of the humerus bone of the upper arm. The glenohumeral joint is a ball-and-socket joint.

The ball is the humeral head, and the socket is the glenoid cavity.

A standard shoulder replacement replaces the head of the humerus with a similar prosthetic head (usually made from metal), and the glenoid cavity is resurfaced with polyethylene (plastic) socket.

This prosthetic combination aims to replicate the native anatomy of the shoulder joint. One of the requirements for a standard shoulder replacement is an intact rotator cuff to allow adequate function.

In a reverse total shoulder replacement, the ball is attached to the glenoid (a glenosphere), and the socket fits where the humeral head has been resected.

Why was the reverse shoulder replacement developed?

The development of the reverse shoulder replacement was to address the problem of an arthritic shoulder with a deficient rotator cuff. In these patients, the standard shoulder replacement components quickly loosened and failed. The failures were due to excessive movement.

The reverse shoulder replacement addressed this by providing a more constrained prosthesis that reduced the amount of abnormal movement that had caused loosening in standard designs.

This prosthetic design alters the biomechanics of the shoulder. It forces the body to use the large shoulder muscle (deltoid) rather than relying on the deficient rotator cuff.

Several generations of prostheses have lead to the modern designs we have today.

When is a ‘Reverse Shoulder Replacement’ indicated?

Initially, the reverse shoulder replacement was indicated in patients with arthritis secondary to a significant cuff deficiency - know as Cuff Tear Arthropathy.

The indications for the use of reverse shoulder replacement have expanded with increased knowledge and experience in the use of reverse prostheses.

The current indications for reverse total shoulder replacement are:

• Cuff Tear Arthropathy - severe arthritis secondary to a chronic rotator cuff tear

• Proximal humerus fractures in the elderly - severe fractures that cannot be reconstructed with plates and screws

• Failed shoulder replacement

• Tumour of the shoulder joint

• Chronic shoulder dislocation

• Painful shoulder with an inability to raise the arm in the setting of a large irreparable rotator cuff tear - pseudoparalysis

In the right patient, this is an excellent option to reduce pain and improve function.

Mr Churchill performs both Standard and Reverse Total Shoulder Replacements.