Is the Reverse Shoulder Replacement the Answer to Rotator Cuff Deficiency?

For a while now, there has been the notion that poor results of traditional shoulder replacements for patients with severe rotator cuff tears could be improved with a new type of implant. That implant is called a reverse shoulder arthroplasty (more about this in a minute). But as more studies are completed, the clinical perception that the reverse shoulder arthroplasty has better results has come under question.

In this study from New Zealand, results for severely damaged shoulders from massive rotator cuff tears using the reverse shoulder arthroplasty are compared with hemiarthroplasty. Now for a brief description of these two surgical approaches.

The “normal” artificial shoulder was designed to copy our real shoulder. The glenoid component (the socket) was designed to replace our normal shoulder socket with a thin, shallow plastic cup. The humeral head component was designed to replace the ball of the humerus with a metal ball that sits on top of the glenoid.

This situation has been compared to placing a ball on a shallow saucer. Without something to hold it in place, the metal ball simply slides around on the saucer. In the shoulder that “something” is the rotator cuff and the muscles that attach to the tendons. Without a rotator cuff to hold the metal ball centered in the plastic socket, the metal quickly wore out the plastic socket and the joint became painful once again.

The answer to this dilemma was to rethink the mechanics of the shoulder joint and design an artificial shoulder that worked differently than the real shoulder joint. The solution was to reverse the socket and the ball, placing the ball portion of the shoulder where the socket used to be and the socket where the ball or humeral head used to be.

This new design led to a much more stable shoulder joint that could function without a rotator cuff. The artificial joint itself provided more stability by creating a deeper socket that prevented the ball from sliding up and down as the shoulder was raised. The large deltoid muscle that covers the shoulder could be used to more effectively lift the arm, providing better function of the shoulder. The final goal is to have a shoulder that functions better, is less painful, and can last for years without loosening.

With the hemiarthroplasty operation only half of the hip is removed and replaced. (Hemi means half, and arthroplasty means joint replacement.) The hemiarthroplasty replaces only the ball portion of the shoulder joint, not the socket portion.

As this study showed, by comparing 102 patients who received the reverse shoulder arthroplasty with an equal number of patients who received a hemiarthroplasty, results could be compared equally. Items compared included differences in operating times, survivorship of the patient and/or the implant, and revision rates (i.e., second surgeries affecting the implants). In each group, half the patients were women and half were men.

Outcomes were first compared and reported six months after the first surgery. Everyone was followed for at least three years. Some patients were in the study for up to 11 years. They found that reverse shoulder arthroplasty did, indeed, provide better function and results were considered “superior” to that of the hemiarthroplasty.

Healing and recovery seemed to take longer in the hemiarthroplasty group. Younger patients in both groups had the worst function. And patients in the reverse shoulder group had higher rates of complications (e.g., dislocations, infections, ongoing pain, loosening of the socket).

Overall, the results support the use of reverse shoulder arthroplasty (over hemiarthroplasty) primarily for older patients with a degenerative shoulder joint and humeral head collapse from a massive rotator cuff tear. In fact, the authors suggest “use of the reverse shoulder arthroplasty should continue to be restricted to elderly patients.”