Who was John Charnley?
Simply stated, he was both a visionary and a relic. He laid the foundation for modern orthopaedics, an entire branch of medicine. But then defined that new branch in terms of pre-World War II surgical medicine (no antibiotics in surgery, for example). Brilliant, flawed, and compelling—here is the complicated story of Sir John Charnley as told in Chapter 3 of the book: “As Far North as Memphis” by Professor Charles Crawford of the University of Memphis and James Bradley.
From Dentistry to Orthopaedics
John Charnley was born 1911 in Bury, England, a town of 55,000 people which dates back to the Roman era. He’d initially intended go into dentistry. His father operated a chemist shop where he also performed dentistry in a back room—but the headmaster at Charnley’s school convinced him to choose medicine as a career instead.
At the age of eighteen, Charnley was accepted by the University of Manchester to study medicine, and while there he would have been exposed to lectures by Harry Platt, one of the leading British orthopedic surgeons of the time. Charnley graduated in 1935 and was awarded a fellowship from the Royal College of Surgeons of England in his first year as a physician.[i]
Four years later, Charnley returned to Manchester where he simultaneously held two posts: resident casualty officer at the Manchester Royal Infirmary and assistant resident surgical officer. These duties kept him extremely busy, but the work gave him valuable surgical experience and brought him into contact with orthopaedic injuries for the first time. It so happened that the orthopedic unit was supervised by none other than Platt himself, who was assisted by Henry Osmond-Clarke.[1] Both men were influential in guiding Charnley towards specializing in orthopedics and orthopedic surgery, but there may have been an additional factor in his decision, an incident that had occurred when Charnley was still a student.
He was a member of the university’s mountaineering club, and during a climbing trip a fellow student took a bad fall and fractured his thigh bone. The injury was severe, but the climbers could not leave the top of the climb due to darkness. Charnley applied a splint to the leg, but during the night the injured student succumbed to shock. To what degree this tragedy affected Charnley’s career choice is not known, but such an event undoubtedly would have had an impact on any young doctor.[ii]
Forged in World War II
For Charnley the Second World War was a pivotal experience. Joining the Royal Army Medical Corps in May 1940, he spent the majority of his military service in Cairo, Egypt, where he came to the attention of St. John Dudley Buxton. Buxton’s duties included the organization of military orthopedic centers in the Middle East, and he soon noticed Charnley’s abilities, assigning him a variety of responsibilities, one of which was to have important consequences.[iii]
Among his duties was supervision of a machine shop, where Charnley was responsible for manufacturing appliances and surgical instruments for one of the Cairo centers. His work there, together with his natural mechanical skills, added to his knowledge of metalworking, an expertise that would be of enormous benefit later. Buxton was also probably responsible for Charnley’s being invited to join, as an associate member, the British Orthopedic Association in 1943.[iv] Charnley remained in Cairo from the fall of 1941 to May 1944, when he was sent back to England to serve as orthopedic surgeon at the military hospital in Shaftesbury, England.
Following his discharge from military service in 1946, Charnley returned to Manchester to resume work with Platt, who soon sent him to one of the peripheral country orthopedic hospitals. It was an assignment that exposed Charnley to elective orthopedic surgery. For the first time he was treating patients afflicted with bone and joint tuberculosis, with poliomyelitis, or with other diseases. All were problems for which corrective surgery appeared appropriate. After six months he returned to Manchester, and in 1947, following Harry Platt’s retirement, Charnley was named Consultant Orthopedic Surgeon at the Manchester Royal Infirmary and visiting orthopedic surgeon at Wrightington Hospital near Wigan, in northwest England.[v] It was the latter appointment that would turn out to be central to Charnley’s future research.
The Idea of a Total Hip Replacement Takes Root
By 1951, many orthopedic surgeons, with the notable exception of McKee, were beginning to believe that total hip replacement would never be a viable surgical option. Charnley himself had given serious thought to the problems that would be encountered in such surgery—in fact, he claimed to have even designed a hip arthroplasty as early as 1946 but had abandoned the procedure after a preliminary trial proved unsuccessful—and he likewise had become pessimistic about whether total hip replacement was feasible.[vi]
Charnley did not completely stop thinking about hip arthroplasty, especially for patients with osteoarthritis in both hip joints and those suffering from rheumatoid arthritis, an inflammation of the membrane that protects the joints. He also became intrigued when a patient who had received a Judet acrylic prosthesis complained that his hip would squeak when he leaned forward and that the noise was so pronounced that his wife would leave the room.[vii] It was not an isolated incident either: Charnley was aware of other patients with Judet hips that exhibited the same phenomenon, typically about two years after surgery, although the squeaking would eventually disappear.
Charnley believed the squeaking was caused by friction between the femoral prosthesis and the hip socket and that the underlying problem was a lack of lubrication inside the joint. The squeaking stopped, he thought, only because of loosening of the prosthesis in the socket, not because of improved lubrication. This insight sent him on a search for a way to lubricate the artificial joint or, failing that, to find a material that would lessen resistance and friction and also be suitable for insertion in human bodies.[viii]
Charnley Rejects Lubricating the Hip, Narrows the Problem
After an exhaustive study of the science of lubrication—both biological and mechanical—Charnley concluded there simply was no way to introduce a lubricant into the joint. That left just two options: either the prosthesis itself would need a permanent coating, such as that naturally produced by the body in healthy joints, or the material from which the prostheses was fabricated would have to be of a type that produced minimal friction. Every solid has a “coefficient of friction”—the higher the coefficient number, the greater the friction—and the coefficient of friction for normal joint cartilage is, to quote Charnley’s own words, “phenomenally low.”[ix] In his search for such a “slippery substance,” Charnley made contact with Henry Crossley, the owner of Henry Crossley Limited, a company that was then looking into new uses for a new product. The product’s chemical name was polytetrafluor-ethylene, or PTFE, but it would become better known by its trade name, Teflon.[x]
Although the effects of this product on the human body were unknown at the time, the material was believed to be inert in the human body, and its low surface friction characteristics made it appear to be the ideal material for Charnley’s purposes. Indeed, the notion of introducing a “slippery surface” (in this case, Teflon[2]) marked a key advance over McKee’s work at Norwich; because there was no longer a need for continued lubrication, low-friction arthroplasty was now feasible.[xi]
Charnley Goes Single-Cup and Excises the Femoral Head
At some point between 1956 and 1958, Charnley began experimenting with the material in his own hip arthroplasty cases. At first, he used a “double-cup” technique, in which PTFE was applied to the acetabulum, forming a kind of thin cup, while a second cup coated with the material covered the femoral head. The aim was to reproduce the kind of coatings found naturally in the joint. While the procedure produced good results in pain relief and movement, Charnley realized that the femoral cup would inhibit blood supply to the bone, and he decided to try a different approach, using only one cup.[xii] He optimistically hinted at such a modification in a 1959 lecture delivered to a division of the British Medical Association, saying it was “probable” that a prosthetic “femoral prosthesis, articulating with a PTFE socket” would work better than his original double-cup design.[xiii]
This next step required the removal of the femoral head by excision and replacing it with a prosthesis of the type used by Moore but keeping the acetabulum PTFE cup Charnley had developed. His engineering colleagues also convinced him to make the diameter of the femoral ball as small as possible to further reduce friction and to allow for a thicker acetabulum cup. This would help prevent slippage of the cup within the hip socket. The final result was a femoral prosthesis with a ball approximately half the diameter of Moore’s device. Other surgeons would question the wisdom of this final change, but Charnley would remain steadfast in his belief that his approach was the correct one.[xiv]
Acrylic Dental Cement
He also decided to add acrylic dental cement to fix the femoral device. Not that using cement to fix an implant to bone was a new idea. Some 70 years earlier, Gluck had tried this, using a variety of materials including an alloy of copper and mercury, “plaster of Paris, and stone putty (rosin with pumice stone or gypsum).”[xv] And as recently as 1953, Haboush had used dental acrylic cement to affix the two parts of his prosthesis.[xvi] But Charnley would use the cement not as adhesive, but as grout to make a better in-bone fit.
Now all Charnley had to do was make the devices and surgically implant them. Because he knew exactly what he wanted, he initially fabricated them in his attic workshop.[xvii] Charnley felt confident that he had found the formula for total hip replacement.
Charles F. Thackray Ltd and Harry Craven Join Charnley
The exact date that Charnley performed his first total hip replacement using PTFE—he always called it “low-friction arthroplasty”—and the name of the first patient who received the new prosthesis are not known. Part of the confusion is due to Charnley’s own later, but inconsistent, accounts, but it was probably in 1956.[xviii] Two years later he hired a technician, Harry Craven, to take over the actual fabricating process, although if a piece needed modification Charnley would typically make the changes himself. Only when both men were satisfied with the design would the prototype be sent to Charles F. Thackray Ltd., in Leeds for manufacture.[xix] The relationship with Thackray was long-standing, having begun in 1947 when Thackray replaced Charnley’s previous supplier of “hip fracture devices.” The Thackray company itself had started out as a retail pharmacy but had been deeply involved in the manufacture of surgical equipment since the end of World War I.[xx]
Charnley opened a special bio-mechanical workshop in 1961, and a year later he installed a wear testing machine to evaluate the characteristics and suitability of various materials, including PTFE, for implants. For a while, everything went well—Charnley performed approximately 300 apparently successful hip replacements using PTFE cups—but a major problem began to appear. The same year that he began testing material in his new workshop, Charnley discovered that particles that had worn off the acetabular cup were causing some “adverse tissue reactions” in patients over the three-year period that PTFE had been used. Charnley had even detected some wear in the cups after the first year, but he had assumed this was a normal “bedding-in” process and would subside in time.[xxi] In fact, the wear continued, tripling after three years. Moreover, while the wearing itself was troubling enough, the particles were causing material masses to form around the joint and were destroying the bone itself.
Deeply concerned, Charnley injected PTFE particles into his own thigh to determine once and for all whether the product itself was the cause. It was. When the mass in his leg increased in size over a nine-month period, he knew that the material could no longer be safely used and that the cups already implanted had to be removed. Patients were notified, and he performed each revision surgery himself.[xxii] It was a setback that made Charnley an extremely cautious man.
Craven Tests a New Plastic
At about the same time, Craven was quietly testing a sample of a new plastic that had been developed in Germany to make plastic gears and which was being used locally in Lancashire textile machinery. The material was “ultra-high molecular weight polyethylene,” UHMWPE for short. Craven had showed the sample to Charnley, who had told Craven he was wasting his time. Fortunately, Craven ignored Charnley’s advice and began testing a sample.[xxiii]
The results were immediate and striking after three weeks of continuous testing, the new plastic still did not show as much wear as PTFE had exhibited in only twenty-four hours. Charnley was now interested, but because of his experience with Teflon he again experimented on himself by placing small samples in his own thigh. The new product appeared to be inert in humans, but Charnley was taking no chances. After six months, when there were still no discernible effects from the sample in his thigh, and after some further testing in the workshop he concluded that HMWP was indeed safe to use. Charnley performed the first arthroplasty using the new plastic in November 1962.[xxiv]
Although Charnley, ever cautious, did not immediately publish the results of his revised procedure, word spread of his success. Within a year, the demand for his devices had grown to the point that increased production of implant devices was needed. Craven had been making the cups in the biomechanical workshop as needed, but Charnley asked him to build a machine that would produce the parts faster. He did, and the machine was later sold to Thackray. The femoral prosthesis was forged from stainless steel by a company in Sheffield, then taken to Thackray where it was machined to its final shape. Final polishing was then done at Wrightington.
The Eureka! Moment but Charnley Blocks Wide Distribution
Surgeons were naturally anxious to learn more about his breakthrough, but there was a hitch. Charnley himself had a strong working knowledge of physical mechanics—thanks largely to his army posting in Cairo—but he was doubtful as to whether other surgeons had the requisite understanding and skill. In his view, as reported in a 1959 lecture to a division of the British Medical Association, total hip replacement required “training in mechanical techniques which, though elementary in practical engineering, are as yet unknown in the training of a surgeon.”[xxv] He was determined to rectify this oversight: only surgeons who visited the Center and agreed to undergo at least two and a half days of training (to learn Charnley’s specific procedures) were permitted to purchase the devices from Thackray. Even then, not all surgeons who wanted to attend were accepted by Charnley.
This sharply limited Thackray’s profits, and it also created resentment among surgeons who felt they should be allowed to purchase the prosthesis based on their reputation alone. By 1968 Thackray was needing more sales if it was going to continue manufacturing the devices, and Charnley agreed to no longer require that surgeons have his personal approval before training at the Center. But he still insisted that any surgeon who wished to purchase his devices from Thackray first had to attend at least a two-day training session at Wrightington. Even this final restriction would be lifted a few years later, thereafter, allowing anyone to purchase a prosthesis from Thackray.[xxvi]
Charnley’s cautious approach was evident in other respects as well. One was his decision to offer his arthroplasty only to elderly patients—those older than sixty-eight years of age—who had severe disabilities. His philosophy in this regard put him at odds with prevailing attitude of American surgeons, who believed that hip replacement should be primarily used for younger patients and those who could be expected to lead a more active life after surgery. But even with these age and disability restrictions, Charnley had no shortage of patients. By 1967, upwards of 700 total hip replacements were being performed every year at Wrightington.[xxvii]
Charnley Finally Publishes – Refuses to File Patent
Although his accomplishments had become widely known, Charnley declined to publish his research until he was certain that the long-term results were positive—he was not about to risk a repeat of the Teflon experience. When he finally did publish, ten years after his first use of HMWP, he was able to report that 90 percent of his patients had no pain whatsoever after surgery, with the remaining patients indicating only slight or intermittent pain. Of those patients who had been able to walk only a limited distance with the aid of crutches or canes before the surgery, over 80 percent claimed to be able to walk, unaided, an unlimited distance afterwards.[xxviii]
Despite Charnley’s reluctance to allow sales of his prostheses to surgeons unfamiliar with his procedure, he gladly shared information about his procedure—once he was satisfied there were no hidden problems. In fact, he did not even patent his original design, which led to the copying of his prosthesis by others, although he later did obtain patents on some instruments and other innovations. When he realized that he could not keep others from using his name in connection with the copies, he asked that competing products carry both his name and that of the imitator, creating a hyphenated name, such as the Charnley-Müller prosthesis, an arrangement that Charnley had previously authorized. In fact, the Charnley-Müller device was different from Charnley’s in two important details. The copy’s femoral head was half again as large as Charnley’s and was fabricated from chrome-cobalt instead.[xxix]
Other manufacturers produced their own variations, again using Charnley’s name. In response, Charnley attempted to copyright his name to prevent imitators from passing their prostheses off as Charnley-authorized products without his express approval. Nonetheless, the Charnley-Müller prosthesis gained popularity in the U.S. because of its larger femoral head size, its material (chrome-cobalt), and the fact that the surgical procedure with this implant did not require the removal and reattachment of the greater trochanter section of the femur.[3] Thackray later produced chrome-cobalt prostheses to compete with other manufacturers in the American market, but the product failed to perform as well as the competition and eventually was dropped. Charnley himself never used anything but stainless steel.[xxx]
Charnley’s Way or the Highway
Surgeons also adopted another Wrightington innovation: conducting surgery inside a “sterile air tent.”[xxxi] Charnley was unwilling to rely on antibiotics to deal with infection; he was determined to minimize the risk of infection in the first place. To accomplish this, he worked with F. Hugh Howorth (of Howorth Air Engineering) to create “an ultra-clean operating environment.” Besides the enclosure itself, called a “greenhouse,” they designed impermeable masks and gowns that were vented by a built-in air exhaust system. The overall effect was to reduce the postoperative infection rate from 9 percent to less than 1 percent.[xxxii]
Charnley officially retired in 1975 but continued to conduct research on, and write about, orthopedics. He had truly changed the world of orthopedic surgery, and for his many accomplishments, especially the hip replacement innovations he developed, he garnered numerous honors in Britain and would be knighted in 1977, five years before his death.[xxxiii] By then his hip replacement procedure had indeed become “the gold standard” in orthopedic hip surgery.[xxxiv]
Besides his direct contributions to orthopedic surgery, Charnley left still another legacy, one that was epitomized by his long, albeit troubled, relationship with Thackray. If total hip replacement was to be a safe and reliable surgical option, quality prostheses and other critical components were essential. In this regard, as with surgery itself, Charnley was a perfectionist. Besides the prosthetic femoral stem and acetabular cup, two other kinds of manufactured devices were needed: screws or nails to hold the cup in place, and tools to perform the procedure. Moreover, any component that was to remain in the body had to be made of an inert material—it must neither react to surrounding body tissue nor induce a reaction that would cause the body to reject the implant. Fine polishing, the last step in the manufacturing process, ensured that the surface of the prosthesis was as smooth as possible.[4]
Of course, none of these items was already on the shelf waiting to be ordered. Each device had to be designed and manufactured, usually by companies that had beginnings unrelated to surgery, let alone orthopedic implants. They were in a new field as well and would be called upon to manufacture products that met exacting quality standards. Thackray had once been a retail pharmacy, while other British companies had equally diverse origins. So, too, in the United States, where the first three American manufacturers started out as makers of customized splints.
[1]Platt and Clarke would each later be knighted for their work in orthopedics. Platt would also be the first orthopedic surgeon to serve as President of the Royal College of Surgeons of England, and Osmond-Clarke would become orthopedic surgeon to the Royal Family.
[2]Teflon is a trademarked brand of PTFE made by DuPont, but the properties of Charnley’s PTFE were essentially the same.
[3]The greater trochanter, also called the great trochanter, is a large protuberance at the upper part of the femur but below the femoral head. Charnley’s procedure required its removal and reattachment.
[4]Matte finishing, which did not require the same level of polishing, would be tried in later years. This is treated in Chapter Five.
[i]Waugh: 12. S. M. Donald, “Sir John Charnley (1911-1982): Inspiration to Future Generations of Orthopaedic Surgeons,” Scottish Medical Journal 52, no. 2 (May 2007): 44.
[ii]Waugh: 18-19.
[iii]Ibid: 24-25.
[iv]Ibid: 25, 31.
[v]Ibid: 33-35; Donald: 43.
[vi]Waugh: 100.
[vii]Ibid: 101.
[viii]Ibid.
[ix]John Charnley. “Surgery of the Hip-Joint: Present and Future Developments.” British Medical Journal (March 19, 1960): 826.
[x]Waugh: 105.
[xi]Charnley: 826; Waugh: 105.
[xii]Waugh: 101-106.
[xiii]John Charnley. “Surgery”: 826.
[xiv]Ibid: 106-107.
[xv]Enyon-Lewis, Ferry, and Pearse” 1534.
[xvi]Nisbet: 124.
[xvii]Ibid: 125.
[xviii]Waugh: 105; Gomez and Morcuende, “Historical”: 32.
[xix]Waugh: 113-117.
[xx] Gomez and Morcuende, “Historical”: 34.
[xxi]Waugh: 120.
[xxii]Ibid: 120-121.
[xxiii]Nesbit, 127.
[xxiv]Waugh: 123-124.
[xxv]Wrightington Hospital
[xxvi]Waugh: 129.
[xxvii]Ibid: 128, 137.
[xxviii]Ibid: 128, 130; Donald: 45.
[xxix]Waugh: 172.
[xxx]Ibid: 171-176.
[xxxi]“Obituary,” British Medical Journal. 285 (21 August 1982): 567.
[xxxii]Nesbit: 131.
[xxxiii]Donald: 46.
[xxxiv]B. M. Wroblewski. “Professor Sir John Charnley (1911-1982),” British Society for Rheumatology 41 (2002): 825.
