The Challenge of Choosing the Right Shoulder ReplacementBack in the 1970s, there was only one prosthetic implant available for patient's needing a total shoulder replacement (TSR). Today, there are more than 70 different shoulder systems on the market. In this review article, surgeons from the William Beaumont Hospital in Michigan present information on the major types of prostheses surgeons use most often.
The authors offer guidelines for deciding which option might work best for different types of patients. Sometimes there's really more than one that could work. So, the surgeon must examine each patient carefully in making that final decision as to which one to choose.
The surgery can be very complicated. Multiple factors must be considered such as the patient's age, underlying pathology, condition of the rotator cuff (muscles around the shoulder), and current/desired level of function. Shoulder replacements are indicated when pain is disabling and loss of motion and strength leaves the person unable to complete daily tasks and activities.
Most patients who need a shoulder replacement have arthritis either from age-related degeneration (osteoarthritis) or from a previous injury (posttraumatic arthritis). Sometimes, there's been a history of fracture, tumors, severe rotator cuff damage, and even a failed first shoulder replacement surgery.
Even though there are dozens and dozens to choose from, surgeons tend to pick between one of three main types of arthroplasty (another name for shoulder replacement). There's the hemiarthroplasty (only one side of the joint is replaced), the reverse total shoulder arthroplasty (RTSA), and the total shoulder replacement (TSH) already mentioned.
Here's a summary of the detailed information the authors offered about each of the other major options to choose from. First, the hemiarthroplasty. This is just the replacement of the humeral head and upper neck of the humeral bone supporting the head. At first, these were designed for people with humeral neck fractures. But the use of the hemiarthroplasty has expanded over time as surgeons found other problems that were solved with this component. Now it is also used for arthritis, rotator cuff tears, and osteonecrosis (bone death caused by loss of blood supply) of the humeral head.
Studies show that the hemiarthroplasty is more likely to be successful when used in younger patients and early after the injury (in other words, without a long delay between injury and operation). Sometimes it's just difficult to decide between the hemiarthroplasty and a full shoulder replacement. Why do a full replacement when a partial replacement would work just as well? But there's no sense in doing a partial replacement if the patient is going to end up needing a full shoulder replacement eventually anyway.
The most reasonable use of the hemiarthroplasty is for the patient who has bone loss and soft tissue damage that makes surgical reconstruction a very complex project. Without adequate bone mass and sufficient muscle strength, the implant loosens, which can lead to implant failure. Hemiarthroplasty offers a way around those complications.
It's most effective when the shoulder socket is perfectly fine but the head of the humerus is arthritic, damaged from osteonecrosis or rotator cuff tears, or defective. Patients who receive a hemiarthroplasty report it is certainly better than doing nothing -- they get pain relief, increased motion, and improved function. The net result is an improved quality of life.
It's also possible to resurface the joint when arthritis has damaged the joint surface but there's no need to tear the whole thing out and replace it. This procedure is called a resurfacing hemiarthroplasty. The humeral head is smoothed but not removed. Sparing the humeral side also preserves the patient's natural joint angles. If there's a need for a total shoulder replacement later, then it can be done sometime down the road. Shoulder resurfacing is used most often in young (55 years old or younger), active/athletic adults.
And for the patient with severe rotator cuff damage, hemiarthroplasty is still possible but with an extended-coverage head. This modification is needed because without the rotator cuff, it's difficult to keep the humeral head in the center of the joint. The extended-coverage head makes contact more fully inside the socket. That feature helps keep it in the joint and more stable but without getting pinched under the acromion (the curved bone across the top of the shoulder).
A reverse shoulder arthroplasty is used in older adults who have a torn rotator cuff that can't be repaired. Instead of the round ball replacing the head of the humerus (upper arm bone), the socket is attached to the bone. The round replacement ball of the joint (called the glenosphere) is inserted into the place where the natural shoulder socket used to be.
This design helps maintain shoulder stability when the muscles are deficient and unable to function as they should. In fact, many patients who suffer pseudoparesis (inability to lift the arm) benefit from a reverse shoulder arthroplasty. The change in the fulcrum allows them to lever the arm up even when the muscles are weak from irreparable injury or damage.
When both sides of the joint are involved, it makes the most sense to perform a total shoulder replacement. Loss of joint cartilage from arthritis leading to pain and disability are the main reasons to do a full joint replacement. The rotator cuff must be in good condition to support the joint and restore full function of the shoulder and arm. And there has to be enough good bone stock to support and hold the implant in place.
Many, many studies have shown the benefit of the total shoulder replacement (TSR). Compared with the other options, the TSR gives patients more motion, less pain, and improved strength. Regardless of where the erosion occurs in the joint or what causes it (osteoarthritis versus inflammatory arthritis), the complete replacement of both sides solves the problem.
That brings us to the topic of what to do when the shoulder replacement fails. Revision arthroplasty (a second surgery) is often possible. First, the surgeon evaluates what went wrong -- did the implant come loose for some reason? If so, was it because of bone loss? Muscle weakness? Or was the implant in the wrong position, perhaps even the wrong size for the patient? Sometimes the implant just wears out and must be revised or replaced.
If any of those situations occurs, the patient should be prepared for the fact that the results of the revision usually aren't as good as the original implant procedure. The revision must be designed for each individual based on the amount of bone stock available, the strength of the muscles, what can be salvaged, and what can't be saved. Each individual muscle has a specific purpose and should be evaluated. Nerve function can be compromised by scarring, so the nerves must be carefully assessed as well.
When it comes to the need for reconstructive (or revision) shoulder surgery, surgeons are often faced with a complex challenge that can't be solved with a simple formula. The guidelines presented in this article will help, but experience and first-hand assessment are the real keys to making the final treatment decision that is just right for the patient.
J. Michael Wiater, MD, and Meredith H. Fabing, DO. Shoulder Arthroplasty: Prosthetic Options and Indications. In Journal of the American Academy of Orthopaedic Surgeons. July 2009. Vol. 17. No. 7. Pp. 415-425.
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