The Evolution of Shoulder Arthroplasty

CHAPTER PREVIEW

CHAPTER SYNOPSIS

This chapter chronicles the evolution of shoulder replacement arthroplasty. Major concepts and contributors are identified. Many implants of historical significance, as well as those used today, are reviewed.

IMPORTANT POINTS:

1

The first shoulder arthroplasty was performed in 1893.
2

Most arthroplasty systems can be classified as unconstrained, semi-constrained, or constrained.
3

Most standard arthroplasty systems in use today are unconstrained devices.
4

Semi-constrained systems highlight attempts to solve some common problems, but few remain in use.
5

Constrained systems have significant applications for treating rotator cuff–deficient arthritic shoulders and other complex problems.
6

Modularity and prosthesis adaptability allow more reliable re-creation of humeral anatomy and may improve results.
7

Many renowned experts in the orthopedic community have contributed to the evolution of shoulder arthroplasty.

CLINICAL/SURGICAL PEARLS:

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The development of prosthetic replacement of joints in orthopedics is often a fascinating journey to review. The evolution from early ideas to successful, time-tested arthroplasties is filled with quantum leaps forward as well as steps back, and many of the great talents in our field have participated. The shoulder is no exception. In fact, the shoulder’s extensive range of motion and heavy reliance on soft tissue for stability and function have produced a varied array of ideas and implants. As some have succeeded while others have failed, many valuable lessons learned continue to guide what we implant today, as well as shape our ideas for future advances.

Although the common view is that shoulder arthroplasty development has lagged behind its counterparts in the hip and knee, it is on this joint that the first total replacement was attempted. This was performed by the French surgeon Jules Emil Péan in 1893. Prior to this, ivory had been used as a prosthesis material by Themistockles Gluck, and he had designed a hemiarthroplasty for the shoulder as well. However, Péan’s procedure was unique. It was performed for tuberculosis infection in a 37-year-old baker and remained functional for two years until the inevitable recurrence of infection prompted its removal. The implant, which today resides in the Smithsonian Institute, was constructed of rubber and platinum ( Fig. 3-1 ). The use of artificial materials was quite contradictory to most efforts of the time, which largely focused on the creation of pseudoarthroses or the resurfacing of joints with soft tissues. That, coupled with the involvement of both the glenoid and humerus in the arthroplasty, made the procedure very novel. Its success, however short lived, was remarkable as well, especially given the diagnosis for which it was utilized.

Despite Péan’s development, a return to the use of foreign artificial materials did not happen for many years. Instead, the focus remained on mobilizing ankylosed joints with osteotomies and soft tissue interposition. These techniques were applied on a limited basis to the shoulder, likely because scapulothoracic motion made glenohumeral ankylosis more tolerable functionally. Because the indications for arthroplasty at the time were severe functional loss rather than painful arthritis, shoulder procedures were less commonly performed. However, pioneers of these interposition procedures, such as John B. Murphy (who used local fascial or fatty tissue), William Baer (chromicized pig bladder), and Russell and Andrew MacAusland (free flaps), did apply their techniques to the shoulder with some success. These techniques were frequently used into the 1930s. Perhaps more importantly, requirements for a successful joint arthroplasty were defined. Stable, painless, and increased motion and asepsis all persist as benchmarks sought and measured by surgeons to this day.

An interest in artificial arthroplasties was reestablished in 1923 by the work of Marius Nygaard Smith-Petersen. He noted that the reaction to foreign material in the body was often a synovium-like lining. This led him to the development of the cup (mold) arthroplasty. This was basically a cap placed on the femoral head for hip resurfacing, and represented the state-of-the-art for nearly 30 years. Materials evolved from glass initially to metals, the most commonly used being Vitallium. Although loosening of the implant was a major problem leading to frequent early failure, some good results were noted. This concept was applied to the shoulder by Jónsson. He originally used hip cups but later used implants specifically designed for the humerus. Other resurfacing cups with softer materials were tried as well. Varian utilized Silastic, and Swanson experimented with silicone rubber. However, both these were abandoned, with the Silastic implant noted to have high rates of failure and complications. It is interesting to note the legacy of the cup arthroplasty. The concept is currently seeing a resurgence in its use in both the hip and shoulder. Possible advantages have led surgeons back to the technique, which is often offered to younger patients as a bone-preserving alternative despite a lack of research on its success in this population. The Copeland prosthesis has been the most widely studied shoulder option, and good results have been published for a variety of diagnoses in the short to middle term. Even its failures have led to progress. Matsen, building on findings from femoral retrievals that noted a smooth fibrocartilage on the acetabulum, developed his “ream and run” procedure. In this operation, the glenoid is reamed to restore concentricity, relying on the foreign body reaction to a humeral hemiarthroplasty to restore a fibrocartilage surface over the bone. This procedure has been used successfully, and again illustrates how early concepts can lead to important future advances.

In the 1950s, the first implants bearing a resemblance to today’s arthroplasties were introduced. An anatomically based Vitallium implant was designed by Krueger and used for the treatment of avascular necrosis, and others were using acrylic to fashion stemmed implants for fractures. However, the major leap toward modern arthroplasty was made by Charles S. Neer II in 1953. Building on concepts he learned from the treatment of femoral neck fractures of the hip, Neer designed and implanted a stemmed humeral prosthesis for the treatment of severe fractures of the proximal humerus ( Fig. 3-2 ). This was done to address the inevitable problem of osteonecrosis of the humeral head after these fractures. Neer emphasized that the soft tissue components of the procedure were the most important for stability and function, with the hemiarthroplasty providing a scaffold upon which to rebuild the shoulder. Promising early results and forward thinking led him to expand the indications for this implant to post-traumatic and finally degenerative arthritic conditions. Through his pioneering work, the metallic stemmed humeral arthroplasty was established as a viable option and came to the forefront in the treatment of proximal humeral pathology.

The move toward total shoulder replacement, a concept not visited since Péan’s operation in 1893, was greatly influenced by the work of John Charnley. His success with a low-friction metal on high-density polyethylene arthroplasty in the treatment of hip arthritis prompted interest in the use of similar materials in the shoulder. By the early to mid-1970s, several arthroplasty systems using a polyethylene glenoid component had been introduced for use. The first complete system was the Neer II, created by Neer and Robert Averill and introduced in 1973. This was closely followed by the St. Georg in Europe (1975) and the DANA (Designed After Natural Anatomy, 1976). The progress toward a function total shoulder arthroplasty had begun, but not without problems.

Early shoulder systems often met the goals of pain-free motion and functional gains. However, the establishment of stability continued to be problematic. The lack of bony constraint and large motion range of the shoulder made a stable articulation harder to achieve than in other joints. Most efforts to address this problem focused on building constraint into the prosthesis. Most of the early shoulder systems, including the Neer II, St. Georg, and DANA, had both standard and constrained glenoid options, reflecting the primary issue of the time. In fact, stability problems were one of the major forces that drove the evolution of the total shoulder arthroplasty (the other being glenoid fixation problems). As more implants were introduced, total shoulder systems could be classified by their level of constraint: unconstrained, semiconstrained, and constrained. R. Michael Gross has diagramed this expertly in his “Family Tree,” included in this chapter ( Fig. 3-3 ).

The most successful early example of an unconstrained system is the Neer II. This system utilized multiple humeral components with varied stem lengths and two head sizes. This articulated with a polyethylene glenoid component. Much like John Charnley’s hip arthroplasty, the Neer prosthesis is quite similar to modern arthroplasties of today, and Neer’s results with its use are comparable. The Neer II system is still widely used.

The European counterpart to the Neer implant was the St. Georg, developed by Engelbrecht and Stellbrink ( Fig. 3-4 ). This was originally a polyethylene glenoid that was created to be implanted with Neer’s humeral component, but later they designed their own humeral prosthesis to complete the system. Unfortunately, this system’s use was complicated by another common issue with early total shoulder arthroplasties, that of glenoid loosening. In fact, the rate of loosening was high enough that the surgeons abandoned glenoid resurfacing for a period, instead relying on glenoid reshaping osteotomy or bone grafting to treat this arthritic surface. It should be noted that the St. Georg glenoids were generally more constraining than Neer’s standard implant, which may have contributed to the higher rate of loosening.

Closely following these implants, the DANA, the Bechtol, the Monospherical, and the Cofield were all introduced as unconstrained options. The DANA and Monospherical (also called the Gristina) were similar, requiring greater humeral resection to accommodate a larger humeral head and adding additional constraint on the glenoid side. The Cofield system ( Fig. 3-5 ) utilized bony ingrowth as opposed to cement for fixation on both sides of the joint. The glenoid component was metal-backed and fixed with a post and screws. Also offered was a posterior augmented option, highlighting the emerging identification of posterior wear of the glenoid as an important consideration for glenoid positioning in osteoarthritic shoulders. In following the results of the Monospherical, Gristina et al. were the first to highlight a vast difference in postoperative motion and function based on the status of the rotator cuff and other soft tissues found at surgery. Surgeons today continue to be very aware of these concepts and their effect on the success of arthroplasty.

Semiconstrained systems were designed to add stability and were also used in rotator cuff deficient shoulders. These implants altered the glenoid component to control and contain the humeral head. Many of these options were included in the aforementioned unconstrained systems. Hooded glenoids work against superomedial directed forces on the humerus and were offered with the DANA and the St. Georg. Even Neer’s system includes hooded components (200% and 600%) ( Fig. 3-6 ), although these were rarely used. Deepening the glenoid fossa on the component also helped to stabilize the humeral head. This alteration was employed by the St. Georg (see Fig. 3-4 ) as well as the English-MacNab ( Fig. 3-7 ), which also had a hood. Lastly, a superior spacer could be attached to the acromion to prevent superior migration of the head. The Clayton spacer, a polyethylene block attached to the acromial undersurface, was one such device. The French surgeons Mazas and de la Caffiniére developed an implant utilizing all three of these mechanisms. The Mazas shoulder employed a large polyethylene glenoid with a deep fossa and superior hood that attached directly to the acromial undersurface ( Fig. 3-8 ). In a review of nearly 40 cases using this prosthesis, instability was noted in 9 and postoperative stiffness in 14. In fact, most semiconstrained implants had a poor track record, with marginal function and high complications. The addition of constraint generally applies higher loads to the already tenuous fixation on the glenoid side, often leading to loosening and failure. The fact that semiconstrained implants were often used in cases where the rotator cuff was compromised may also explain the marginal results. Most semiconstrained systems have fallen out of favor and are not used today.