Mark A. Frankle, MD, is a clinical professor or orthopedics at the University of South Florida Morsani College of Medicine, Chief of the Shoulder and Elbow Service, and Director of the Shoulder and Elbow Fellowship at the Florida Orthopaedic Institute in partnership with the Foundation for Orthopaedic Research and Education in Tampa. Dr. Frankle is the president-elect of the American Shoulder and Elbow Surgeons, and his clinical and research interests are optimizing implant design as a means to improve patient care.
The unsolved problem: A muscular imbalance
In patients who have pseudoparalysis in addition to a large rotator cuff tear, there exists a loss of glenohumeral stability. In these patients, the problem is not so much that they lose strength from the deficient cuff, but more so that they lose the stable fulcrum due to the loss of the medially directed force of the rotator cuff to pull the humeral head into the platform of the glenoid. When the deltoid is activated, it becomes a destabilizing force resulting in instability.
Neer described in a 1983 Journal of Bone and Joint Surgery (JBJS) article, “following a massive tear of the rotator cuff there is inactivity and disuse of the shoulder, leaking of the synovial fluid, and instability of the humeral head. These events in turn result in both nutritional and mechanical factors that cause atrophy of the glenohumeral articular cartilage and osteoporosis of the subchondral bone of the humeral head.” To address this problem, he used a reverse shoulder arthroplasty with features including a cemented keeled glenoid component and a cemented humeral stem in 1970 with the Neer-Averill prosthesis “Mark I.” The idea of reversing the prosthesis emerged because of difficulties encountered in implanting an anatomic glenoid implant large enough to stabilize the prosthesis and prevent proximal migration. This was a particular problem in cases with a small glenoid and inadequate bone stock. The Mark I model had a large glenosphere, which did not permit reattachment of the cuff or its remnants. Charles Neer believed it very important to be able to reconstruct the cuff around the prosthesis; his philosophy preceding the Grammont concept of replacing the irreparable rotator cuff with the deltoid, the only intact muscle available for shoulder elevation. To allow for the repair of the cuff, Neer developed the Mark II prosthesis, a “three-element” prosthesis with a smaller glenosphere, which allowed for a better periprosthetic reconstruction. Neer then developed the Mark III prosthesis, which had an axial rotation between the humeral stem and the diaphysis. After this trial, Neer abandoned his constrained prosthesis experiments in 1974, concluding that constraint did not eliminate the requirement to repair the rotator cuff, particularly the supraspinatus, to recover a good range of motion. Unfortunately, all of these devices failed. Understandably, after this experience, Dr. Neer was opposed to future developments of a reverse total shoulder. Hence, for the next 20 years, little development or publication on reverse total shoulders appeared in the literature in North America.
Neer then popularized the idea of doing a hemiarthroplasty, which would allow him to repair the supraspinatus. When he reported his outcomes, he made a classification of outcomes for patients with more extensive muscle and bony pathology. He coined the term “limited goals,” which would improve a patient’s comfort and allow for shoulder function below shoulder level. Others later modified this procedure with capsular reconstruction, bone blocks, and even a bipolar implant, but none of these procedures provided predictable improvements in function.
Unfortunately, the earliest patients in whom I performed a hemiarthroplasty with limited goals progressively deteriorated with continued loss of motion and increasing pain ( Fig. 65.1 ). I was uncertain about how to help these patients. This theme of patients with massive rotator cuff tears with significant loss of shoulder function seemed to come to my clinic in ever-greater frequency, and, despite all my efforts to help these patients, they remained disabled.
In France around the same time, Grammont started to develop a reverse total shoulder implant. A limited report showed some problems, and then in 1991, he published the early results of his reversed prosthesis in Orthopaedics, stating, “Problems of fixation now solved!” He introduced a belief that the reason this now worked and provided functional improvement was due to the improved moment arm of the deltoid that would optimize its function. He also stated that his design would reduce the shear forces because the center of the rotation of the implant was close to the bone.
In 1997 Tornier was trying to launch their Aequalis anatomic shoulder in the United States, and I was invited to spend a week with the designing surgeons, Pascal Boileau and Gilles Walch. The trip turned out to be a major turning point in my career. Both Gilles and Pascal were wonderful hosts and taught me a great deal. During this trip, I asked Gilles particularly about that original patient that I had, in whom I previously performed a hemiarthroplasty for cuff tear arthropathy that progressed with increasing glenoid erosion. He said, “Well, there’s this guy named Grammont, and I’ve been using his prosthesis for a few years. I don’t know how it works, but it works.” It was manufactured by Medinov and was designed by Grammont, Trouilloud, Baulot, and Capon, with Michel Colombier, a mechanical engineer from Medinov. I was able to get a picture of the implant from a pamphlet ( Fig. 65.2 ). Later, Medinov was purchased by Landanger and became a part of DePuy in 1999.
I was hired by Howmedica with Mike Pearl and Greg Nicholson to design their shoulder system. Howmedica was a big manufacturing company, and there was always a little friction in this group. I was very interested in fracture prosthetic design at that point, whereas the rest of the designers were interested in things like the adjustable head-neck-shaft angle, in which I was not as interested. When I came back from that visit in France, I wanted to do a reverse prosthesis because of how poorly the patients whom I had originally performed a hemiarthroplasty for cuff tear arthropathy had progressed. So, I gave a Howmedica engineer the pamphlet with the pictures of the Medinov implant and said, “Make me a custom shoulder implant that looks like this.” However, the implant I received looked quite different, and unfortunately, the implant failed at 3 months when the poly dissociated from the humeral stem. Shortly after this, Howmedica then decided to fire me from the development team. Furthermore, when I tried to contact the engineer who helped to design this custom implant, I was told he had left the company!
At that time, I was using the Foundation shoulder system, which was designed by Richard Freidman and manufactured by a small company called Encore Medical. The design featured a fixed 135-degree neck-shaft angle with a female taper. Fig. 65.3 is an example of this generation of implants, including an onset humeral component that would allow for the humeral stem to be used as a platform system. They subsequently hired me as a consultant, at which point I then asked them to help me to continue to make custom reverse shoulder implants.