By any measure, what Charnley accomplished in the late 1950s and early 1960s had transformed the treatment of hip disease, and the succeeding years saw both remarkable advances in orthopedic surgery and a sharp rise in the number of successful hip implants. Surgery did not merely partner with science and engineering—the fields essentially merged, producing benefits that would have been unimaginable just a few years earlier. It is no exaggeration to say that because of Charnley’s breakthrough the once lame could now walk. But that was only the beginning.
Even though Charnley was clearly the leader in total hip replacement, he was not the only British surgeon conducting research in the area. Throughout the ensuing decade, McKee continued his work at Norwich, while three other groups developed their own distinct surgical techniques, each with a different combination of methods and materials. And while Charnley’s name would be forever identified with his devices (and with their derivations, such as the Charnley-Müller prosthesis), these other systems would come to be associated with the specific locales in which they were developed instead of with the names of the surgeons who designed the techniques and new devices. Hence, the Stanmore Group, the Redhill-Ring Group, and, not least, the group that gave its name to the Exeter Hip. And each of these in turn would go its own way in choosing materials and manufacturers.
Yet despite their differences, each group initially shared a common feature: research was led and controlled by surgeons, not by independent engineers or manufacturers. No doubt one reason for this was a factor that had no equivalent in the United States: Britain’s National Health Service (NHS). Established in 1948, the NHS guaranteed every British citizen access to medical care, including surgery, and it supported research in a wide variety of fields while attempting to keep costs down. And research, from the NHS perspective, meant medical research conducted by surgeons. As at Wrightington, so also at other locales.
It was a system that produced some remarkable breakthroughs, but the role of the surgeon as director of all aspects of research and product development was not to last, and the first departure from this practice occurred at Exeter. Whereas Charnley always maintained close control over every aspect of his research, including both the design and the manufacture of his implants, the Exeter team shifted much of the responsibility for design and testing to a university engineer and left control of the manufacturing process itself to the company actually producing the devices. At that time, its supplier was The London Splint Company. Of course, there could be drawbacks with either method. If a surgeon-researcher became comfortable with specific techniques and materials that appeared to work satisfactorily, there was little incentive to develop alternative techniques or materials. To be sure, there was usually quick response whenever difficulties arose—witness Charnley’s actions following his unsuccessful efforts with PTFE—but the primary aim in such instances was to improve the system already being used. On the other hand, greater independence for manufacturers could create another set of problems, as Exeter’s own experience would one day demonstrate.
Many of these differences in surgical techniques and implant design came about partly because total hip replacement surgery was still in its infancy in the 1960s. New devices that looked promising, whether coming from surgeons or engineers, might or might not work very well in practice, but as yet there was little in the way of uniform testing in either the U.S. or the UK. Nor is this surprising. Despite fundamental differences in how health care was delivered, the two countries were similar in one key respect: although research and testing of new medicines prior to their use by the public was routine, neither government mandated a testing regimen or approval of orthopedic devices prior to their use in actual surgery, and this remained true throughout the decade.
This absence of uniform testing protocols was not, however, due to any failure to appreciate the risks involved. Instead, it was mainly because of the inherent differences between administering medicine to a patient and surgically placing a prosthesis into the patient’s body. The pharmaceutical review model relies on randomized testing over a time period long enough to evaluate both beneficial and adverse effects, all the while controlling for independent factors that might influence the outcome. Double-blind studies are even better: these are trials in which neither the patient nor the doctor knows whether the medication being administered is actually the drug being tested, another drug, or a placebo. Moreover, if severely adverse effects are detected, or if a patient simply wishes to withdraw from the study, his or her participation in the trial can be halted.
Replicating this testing model within the context of hip replacement surgery was simply not possible. Whereas dosage could be carefully measured and monitored, surgeons typically had varying skill levels and different levels of familiarity with the various products and techniques; it could take years before problems were detected and clearly attributed to a particular surgical technique or implant material; double-blind studies were impossible because the surgeon would always know which technique and devices were being used; and any knowledge or advancements that might come about while a study was underway—such as improvements in materials or surgical practices that would likely benefit the patient—would (if the pharmaceutical model were indeed adopted) necessarily be delayed despite their obvious advantages.
Finally, there was also an ethical dilemma that troubled the medical profession right from the beginning of orthopedic implants. Although doctors must provide what they believe to be the best possible treatment for their patients, clinical trials may require that this standard be subordinated to a larger goal—namely, the future good of all patients. However, unlike the usual situation with regard to new medicines, about which a physician may know little, surgeons in the early days of total hip replacement typically favored one method over the others precisely because they truly believed it was superior for specific reasons. May a physician ethically withhold a treatment that he or she believes is in the patient’s best interest?
No doubt the pioneers in total hip arthroplasty were aware of these difficulties and did their best to balance the risks of unproven procedures and materials against the needs of patients who were suffering severe pain or who could not walk. Charnley had shown what was possible; the question now was whether another method would permit the surgery to be performed faster, easier, with less likelihood of infection, and with better long-term benefits to the patient. Theories about how to do this were plentiful, but for even the best researchers there was a jagged learning curve, and many advances were preceded by earlier failed attempts to improve upon Charnley’s procedures and materials. The consequences of so many different approaches to joint replacement would trouble the field of orthopedic implants for decades, affecting both patients and manufacturers. And the conflicts started even before news of Charnley’s success was widely known.
The Stanmore Group
One team of researchers, centered at Stanmore on the outskirts of London, was the product of a collaboration between physicians John T. Scales and J. N. Wilson, both of whom practiced at Stanmore’s Royal National Orthopaedic Hospital. The design team also included Ian Duff-Barclay, a biomechanical engineer for the British Petroleum Research Centre who had been assigned to work for the Institute of Orthopaedics at the University of London. Duff-Barclay was not working for Scales and Wilson, but with them, as evidenced by his co-authorship of numerous articles.
Their experiments began in 1956, and the first product of that research was the development of a “double-cup” acetabulum prosthesis. As the name implies, this device used two cups instead of just one. However, this was not the same as the double-cup device Charnley had initially used. At Stanmore, an outer cup was first fixed into the hip socket by nails driven in by a pneumatic hammer specifically designed for this purpose. This was done to keep the nails from backing out and interfering with the movement of the prosthetic femoral head. As further assurance against such interference, a second, inner cup was also inserted and locked into position. This inner cup could be removed, if necessary, but the chief advantage of the system was that the acetabulum cup did not require cement. Stanmore researchers had discovered that the acrylic resin in the cement, such as that used by Charnley at Wrightington, would degrade and begin to appear in patient urine just over a year after the implant.
A second difference from Charnley’s procedure was that both components of the Stanmore prostheses—the femoral prosthesis and the acetabular cup—were made of metal, whereas Charnley’s acetabular cup was a form of plastic. Stanmore’s femoral stem was also round-tapered and slightly angled to make its insertion into the femur’s marrow cavity easier.
In testing various metals thought to be suitable for prostheses, Stanmore researchers concluded that a cobalt-chromium alloy offered the best wear qualities. Titanium had showed the worst test results—devices made of titanium failed soon after testing started—and stainless steel did not perform much better. Consequently, Stanmore surgeons used chrome-cobalt for both the cup and the femoral stem, and the Stanmore Total Hip Replacement was patented in both the United Kingdom and the United States in 1966.
Stanmore’s other major contribution during the early years of orthopedic implant surgery was a change in how various innovations moved from theory to practice. By working as a design team that included an engineer as well as a surgeon, the group developed a new way of conducting biomedical engineering in the field. Expertise in chemistry and physics, especially in the development of implant materials, was not merely as important as surgical skill—the two fields had become intertwined.
The Redhill-Ring Group
A second group began its work at Redhill General Hospital in southwest England under the direction of Peter A. Ring, who had become interested in hip replacement surgery while holding a research fellowship at the Royal College of Surgeons from 1954 to 1957. Three years later, he began his own research at Redhill, working along the same lines as Charnley, including the use of a cemented plastic cup with a metal femoral prosthesis. Like Charnley, he also noticed that the plastic would break down and that the resulting particles would irritate the surrounding tissue. In revision surgery—subsequent corrective surgery that was sometimes required when a device did not seat properly or otherwise did not perform as intended—he also discovered that the cement did not bond the cup firmly enough to the hip socket. Further experiments convinced him that attaching the cup with a long threaded shaft, along with careful positioning of the femoral prosthesis, would produce a sufficient bond without the use of any cement.
Ring eventually became convinced that the best material for a metal prostheses was cobalt-chrome alloy, which was also the material settled on at Stanmore. The shape of the femoral stem was similar to the one used by Moore in the U.S., but Ring’s device had openings in it that allowed bone material to grow into and around the shaft after insertion. Neither component of the Redhill prosthesis used cement for fixation or bonding.
The overall design remained unchanged until 1967, when a series of changes were introduced, each responding to a deficiency in its predecessor. That year the Redhill group redesigned the acetabular cup and the screw that held it in place in order to reduce fatigue fractures that resulted from weight and other stresses over time. When problems also arose with the femoral stem—it originally had been very narrow—the stem was redesigned to eliminate a tendency to tilt.
Unfortunately, this 1969 change had its own downside: it produced “prosthetic migration,” the movement of the prosthesis from its original position. To resolve this new problem, Redhill researchers created three different sizes of femoral stems in 1971, each of which used a “straight-stem” design originally developed by Moore. These final changes seemed to eliminate this problem, although there would be additional modifications, and Ring’s total hip replacement system would not finally become standardized until 1981.
Switching from metal-on-metal to metal-on-plastic was one thing, but Ring was unwilling to adopt Charnley’s use of cement. In fact, a number of disadvantages associated with cement persuaded him to avoid it entirely. Cement made any subsequent removal surgery more difficult, and the likelihood that hip replacements would loosen also tended to be greater with patients who had cemented implants than with those whose implants had been done without cement. The problem was not so much with the loosening itself as with the presence of particles that inevitably wore off the plastic cup as a consequence of the loosening. These particles, in turn, could increase toxicity problems.
Ring also was concerned about two problems connected with the acrylic cement itself. The first was a consequence of mixing the polymer: the chemical reaction produced heat and pouring the heated cement into the bone might cause tissue damage. Secondly, Ring believed that later infections in patients might be due to the amount of cement in the body. For both of these reasons, Ring decided to stay with uncemented fixation.
The Exeter Group
The third research group, this one in Exeter, a few miles south of London, first began working on hip replacements in 1965. The Exeter team consisted of an engineer, Clive Lee, and a surgeon, Robin Ling. Lee held an engineering degree and had worked for Rolls Royce on jet engines in the early 1960s, and Ling had specialized in orthopedics at the Royal National Orthopedic Hospital at Stanmore a few years before Scales and Wilson began their research there. When Ling had arrived in Exeter in 1963, he had initially sought a position in pediatric orthopedics, but the area was already filled with specialists. He then turned to his second choice: trauma injuries. It was a decision with far-reaching consequences.
Throughout the mid-1960s, thanks to the work of Charnley and others, the demand for hip replacement surgery continued to increase, and the question for Ling and Lee—as it had been for Ring—was which kind of device to use in their surgeries. Initially, they used a metal-on-metal prosthesis, but by 1969 the group was encountering problems with prosthesis loosening, which they attributed to excessive friction found in the metal-on-metal design. Something better was needed, and Charnley’s device looked to be a good starting point.
But there were significant problems with this pursuing this idea. The surgeons at Exeter had become accustomed to using a posterior approach to the surgery (i.e., through the back of the joint), whereas Charnley always insisted that purchasers of his prosthesis use a lateral (side) approach. The differences between the two techniques were not negligible. To reach the bone, surgical incisions must safely traverse layers of tissue while avoiding major blood vessels and minimizing damage to other body tissue. Each path, of course, presents a different set of difficulties, which in turn require different surgical techniques. Adherents of each surgical model truly believe their chosen method is decidedly superior; hence a lasting disagreement over how best to access the hip socket. Ling and Lee were understandably unwilling to use what to them appeared to be the less desirable approach.
The Exeter team also faced a further obstacle if they intended to use Charnley’s devices. Removal and reattachment of the femur’s greater trochanter was an integral part of Charnley’s procedure, but Exeter surgeons believed this carried an unacceptable risk of infection. On the other hand, if they did not agree to follow Charnley in this regard, they would not be allowed to participate in the training at Wrightington or purchase prostheses from Thackray. To resolve this dilemma the Exeter team ultimately chose to design their own prosthesis, one which differed substantially from other hip replacement devices. Their product would become known as the “Exeter Hip,” which initially was sold exclusively through the London Splint Company.
The Exeter Hip used a metal-on-plastic prosthesis with cemented fixation and differed from other devices in two very obvious respects. One was the lack of a “collar” on the neck of the femoral component. This collar supposedly took much of the load and transferred it to the surface of the remaining femoral bone. Without such a collar, it was widely believed, the remaining bone would atrophy. However, the Exeter team had found otherwise when it reviewed follow-up X-rays of patients who had received McKee-Farrar hip implants, so they chose to omit the collar as unnecessary.
A second difference was the shape of the prosthetic stem inserted into the femur. Exeter used a “double-taper” stem, in which the stem itself forced the acrylic cement down into the femoral canal while it was being inserted, in order to improve fixation. The Exeter Hip was first used in November 1970 after extensive laboratory testing. In a variation on Charnley’s own restrictions on the sale of his devices, the London Splint Company agreed not to sell the Exeter devices to surgeons who had not been trained at Exeter until the group had completed at least five years of clinical trials.
Hard Choices
Complicating the search for the “best” hip replacement method for all of the groups was a dilemma: the long-term consequences of using a given material or design might not become apparent for many years after the surgery. The same was true for fixation methods. Yet conducting 10 or 15 years of clinical trials before going forward with a particular implant system was not a realistic option: the demand was too great. People were suffering, and the potential benefits for most patients far outweighed the risks. Moreover, the various implants seemed to be working well, and no law required surgeons or patients to wait.
The real question facing orthopedic surgeons was which particular mix of materials and fixation methods to use.
Making the Devices
Implant devices introduced in the 1960s and early 1970s reshaped not only the science of hip surgery but the business of orthopedic implants as well. While the various British research groups were developing variations on or alternatives to Charnley’s procedure, orthopedic manufacturers in Britain and the U.S. were beginning to compete for business in the rapidly growing total hip market. The usual first step was to negotiate an agreement with one of the research groups to manufacture a particular prosthetic device—obtaining such rights through acquisitions and mergers would be a later development—and a number of companies entered into such arrangements. Thackray, of course, continued to manufacture Charnley’s devices, while other manufacturers worked with the various researchers. But the field on which Richards Manufacturing competed was rapidly becoming crowded.
Zimmer UK
An early and major competitor in the field, this one American-owned, had a familiar name—Zimmer. However, it was not Warsaw’s Zimmer, not Zimmer USA, but Zimmer UK, and the difference was profound: Zimmer UK and Zimmer USA were entirely different companies.
Zimmer UK was the end product of a dispute that had its beginnings in 1938, when there was only one company with the Zimmer name. That was the year that Frank Saemann, who had been Zimmer’s sales manager for six years, convinced company founder Justin Zimmer that a stronger European presence was needed if Zimmer Manufacturing was to compete on the international stage. It appears that Saemann and Zimmer were not in complete accord—to put it mildly—on how to do this, and Saemann soon found himself in virtual corporate exile in Europe. At any rate, Saemann moved to Europe and organized a new international sales force, but with some unusual contract provisions that left Saemann in effective control of European divisions that would eventually become Zimmer UK, Zimmer Holland, Zimmer France, etc. Meanwhile, Zimmer’s U.S. activities continued to operate under the name Zimmer USA. In the years that followed, Saemann did a remarkable job of marketing Zimmer products and, more importantly (especially to Saemann, as it turned out) spreading the Zimmer name throughout Europe.
However, when World War II broke out, a bitter dispute arose between Zimmer and Saemann, over profits and over the right to the Zimmer name. Because of soaring wartime demand for orthopedic products, name recognition and a great deal of money was at stake. The matter wound up in court and was not resolved until 1945, when Saemann prevailed. Besides money damages, Saemann was given the right to register the name Zimmer UK (and other like-named European companies) and use the name Zimmer in marketing even though the true owner would be Saemann’s new venture, the Orthopedic Equipment Company, or OEC. Saemann also apparently copied the Zimmer catalog page for page and reportedly even used Zimmer’s catalog numbers modified only by a prefix or a suffix.
Not surprisingly, when Stanmore researchers needed a manufacturer for its new metal-on-metal devices, they turned to Zimmer UK, which was already a major player in the field. But despite the Zimmer name, Stanmore’s agreement was actually with OEC. In fact, OEC would retain control of the Zimmer UK and its European affiliates until 1982, when Zimmer USA’s owners paid Saemann $14 million for the exclusive right to use the Zimmer name. Nor was Stanmore the only research group that would do business with Zimmer UK.
Down Brothers
Down Surgical was a home-grown British manufacturer that in the mid-19th century had started out as a maker of medical instruments for surgeons at Guy’s Hospital in London. The company eventually came to be owned by Arthur W. Down and his brother Hubert, and as Down Brothers, Ltd., it earned a reputation as a manufacturer of quality surgical products. Business grew steadily and by 1951 Down Brothers had begun its own marketing operation for orthopedic products made in both the Europe and the United States, including Stryker beds and a range of orthopedic instruments. Its catalog that year also included both Judet and Smith-Petersen hip prostheses as well as modified Judet models. Soon the company was also marketing an even greater variety of orthopedic implants, including the Moore and Thompson femoral models. Down Brothers—it would become Down Surgical, Ltd., in 1972—was in fact the initial manufacturer of Redhill’s total hip replacement prostheses, but this did not last for Ring eventually switched to Zimmer UK to make his devices.
Deloro Stellite
Another competitor to enter the total hip field, albeit somewhat later, was Deloro Stellite, a manufacturer of sophisticated alloys such as chrome-cobalt. The company had moved into instrument and device marketing in the 1950s, but it was not until 1972 that it established a branch company (Deloro Surgical Ltd.) to take advantage of the rising demand for total hip replacements and related surgical instruments. Within a few years Deloro Surgical would be manufacturing several hip systems, all made from Deloro’s own trademarked chrome-cobalt alloy called Vinertia and would do so for the rest of the decade.
Howmedica
Near the end of the 1960s yet another American company, Howmedica, acquired the rights to the popular Exeter Hip, although not through negotiations with the research group. Like Deloro Stellite, it was originally a metal manufacturer (Howe Sound) that supplied raw material to various orthopedic manufacturers, but in 1946 it had begun offering various implants made of Vitallium, a trademarked alloy of cobalt, chromium, and some other elements, and by the mid-1960s the company was specializing in chrome-cobalt products. The company changed its name to Howmet in 1964, and four years later Howmedica was spun off as a separate company manufacturing orthopedic products. Almost immediately, Howmedica took over the London Splint Company and, consequently, production of the Exeter device, but its first years in this role were hardly auspicious.
Although the original design of the Exeter Hip had exhibited few problems, within two years of Howmedica’s acquisition of the London Splint Company a number of broken femoral stems made it clear that a stronger stem was required. The breakages apparently were due to changes in the design of the stems that had been made by Howmedica for “reasons of symmetry and ease of manufacture.” Pfizer would take control of the company in 1972, but problems with the Exeter Hip would continue.
Zimmer USA
Back in Warsaw, Indiana, Zimmer USA was not sitting on its corporate hands and in fact had begun marketing its first hip prosthesis in 1950, a femoral-only implant it had developed in association with Dr. Palmer Eicher, working at the Indiana University Medical Center. This gave Zimmer USA an even wider product line, and by the end of the decade its sales were the largest in the industry. When the company received substantial backing from five wealthy local investors, the company was able to add even more products to its catalog.
During the same period, Zimmer USA also began experimenting with porous materials for its implants in an attempt to encourage biological fixation of the implants, and in 1971 the company would market its first Charnley-type system, using a metal femoral stem with a plastic acetabular cup. The following year Zimmer would merge with Bristol-Myers.
DePuy
What of DePuy, Zimmer USA’s long-time Warsaw competitor? Its story was quite different, and it certainly was not as quick as other manufacturers to enter the orthopedic field. The company had grown steadily during the 1940s under the joint leadership of Winifred DePuy Leiter and her husband Herschel, and by 1950 it was the industry leader with more than 50 employees and some $3.2 million in annual sales. But a sequence of events led to a leveling off of the company business in the 1950s. Winifred Leiter died in 1949, and Herschel soon remarried, this time to Amrette Aile. When he died only a year later, she took over management of the company.
It was not a smooth transition. DePuy employees had been under the impression that Leiter had promised to leave the company to its salesmen, and an ownership battle took place. Amrette and her new husband—she married Harry Hoopes in 1951—prevailed, an outcome which would have a long-term effect on the company. Throughout the ‛50s and into the early ‛60s DePuy continued to record strong sales of its soft goods, but the company did not make any significant capital investments. In fact, its 1964 total sales were even lower than they had been in 1950.
Complacent is probably the best word to describe the DePuy top management at this time, and a 1956 article in the Warsaw Times-Union newspaper is unintentionally revealing: it describes a plant and manufacturing process that does not appear to have changed very much over the years. Although Mrs. Hoopes is portrayed as a hands-on manager, the article also mentions that she and her husband had been in Europe for three months the previous year. DePuy’s top management seemed fully satisfied with what it had always made and sold.
This abruptly changed in 1965 when a group of investors purchased DePuy from the Hoopes family. J. Keaton Landis, who had been DePuy’s sales manager, became company president and began to strengthen DePuy’s market share by acquiring other companies and adding new product lines. The turnaround was dramatic, and in 1968 DePuy secured exclusive marketing rights to the Müller Hip, a leading total hip replacement prosthesis. This expansionist approach was short-lived, however. Also in 1968, soon after it purchased Kellogg Industries—another manufacturer of “soft” products such as braces and splints—DePuy was sold to Bio-Dynamics Corporation of Indianapolis, Indiana. DePuy Manufacturing then became DePuy Orthopedics, and for the next five years Bio-Dynamics kept the company under close control and did not allow it to expand.
DePuy’s competitors, however, were not so hampered, and the industry experienced what can only be described as explosive growth in the late 1960s and early 1970s. But advances in hip replacement techniques and new prosthetic devices were not the only reasons for this. Another was a shift in how society looked at artificial joints: as more and more orthopedic specialists came to see total hip replacement as a viable option for their patients, patients likewise grew accustomed to the idea as well. Replacing a section of bone with a surgically implanted prosthesis no longer sounded like science fiction.
And there was a further development in the 1960s that would have even greater consequences for the orthopedic implant industry, especially in the U.S. Halfway through the decade, a dramatic social policy change took place in America: the federal government, 20 years after President Harry Truman championed the concept of health insurance for the elderly, on July 30, 1965, at the Truman Library in Independence, Missouri, President Lyndon B. Johnson signed Medicare into law.
Next Chapter: Richards Manufacturing and Medicare
