Fifty-seven year old John Charnley was on his way from Wrightington Hospital in Wigan England to Oxford University in 1968 to give a talk about his long effort to develop a prosthetic joint implant, the world’s first.
Since 1949, as a visiting orthopedic surgeon at Wrightington and continuing over the next two decades, Charnley and his technicians plowed through multiple designs, metals, polymers, cements and, incredibly, more than 300 consecutive failed hip surgeries, to invent the first reproducibly successful hip replacement surgery and implant.
Charnley, who would eventually be knighted for his accomplishment, was standing on the shoulders of several giants of orthopedic surgery—both surgical and commercial—notably, Friedrich Pauwels (1885-1980) who laid down basic concepts of hip biomechanics in the early 1900s, the German company Hoechst whose Ultra High Molecular Weight polymer (UHMWP) was the final puzzle piece for Charnley and the Copenhagen company Kaler and Jansen and their acrylic bone cement which Charnley would always refer to as the “grout” interface between metal and bone.
With those three components, primarily, Charnley gave physicians the power to say “I can fix that” to millions of disabled patients who’d been fated to live with severely limited mobility and chronic pain.
Before Charnley, orthopedics was a backwater medical specialty of fracture repair, bracing and external prosthetics. The big musculoskeletal problems of the day—arthritis, polio, scoliosis—were treated palliatively, and poorly, forcing patients to steel themselves for tortuous journeys to bone-on-bone joint fusion (aka auto-fusion) and/or early death.
Little did Charnley know, as he made the 169 mile trip to Oxford that day that he was about to meet a student, an aeronautical engineer, who would change orthopedics as much, probably more, than he did. Indeed, this MIT and Columbia University graduate, who was at Oxford University to earn his doctorate, would influence how the entire musculoskeletal industry would design, test, approve, and ultimately, commercialize orthopedic and the very first widely available spinal implants and instruments.
That student would also challenge, to Charnley’s chagrin, the prevailing wisdom that the human hip was a ball and socket joint.
Surgeon Veterans
From the end of World War II to about 1980, surgeon veterans like Charnley, Harrington, Cloward, Küntscher and so many others, who were profoundly influenced by their war time service, created the modern practice of orthopedics and spine repair.
Orthopedics is the largest sector in medicine today (most patients, most healthcare providers, most interventions) and spine is its largest sub-specialty. Every 1.4 seconds, a healthcare provider somewhere in the world employs techniques, uses instruments, and implants man-made constructs that can be traced to the ideas of these pioneering surgeons.
Charnley, like many other World War II physician veterans, viewed his profession in non-commercial terms. Work was less “employment” and more a “calling” to engage in one of the greatest clinical, scientific and existential wars in human history—the good fight to beat back disease and disability. Patents? Royalties? Charnley didn’t bother with those. His good name, gracing his good work, was his ethos.
Finally, in a clear departure from pre-WWII attitudes, Charnley and his fellow surgeon veterans were comfortable with…and humbled by the challenge…opening the human body in order to repair it.
In retrospect, we can see how important of a beachhead Charnley’s hip replacement was. It became, and remains, the basis for every articulating joint repair technology that came next, including the spine (139 synovial joints).
The name Charnley will forever be linked to hundreds of millions of lives made immeasurably better by his good work.
From the 1960s Space Race to the 1980s Orthopedics Laboratory
Atlas rockets with 860,000 pounds of thrust lifted seven Mercury astronauts 160 miles into earth orbit in the early 1960s. Getting to the moon, 239,000 miles from earth, would require, calculated NASA’s engineers, 1.5 million pounds of thrust. No single rocket could do that—then or now. But ten rockets strapped together might. So, with a Jupiter rocket in the middle and nine Redstones clustered around, Boeing/NASA made the Saturn V—which pounded out almost twice the thrusting power of Atlas.
NASA was worried, however, about unsynchronized ignition. If any of the fuel bloated rockets ignited a microsecond too late or soon, it would send a fuel and fire spewing rocket off into…God only knew where.
Seth Greenwald was one of Saturn V’s engineers. He had engineering degrees from MIT and Columbia University and working at Boeing was tantamount to a post-graduate education in systems methods for solving multi-factorial problems.
Aerospace engineers, slide rules holstered to their belts…left nothing untested, unmeasured, unanalyzed, or unbroken. Necessity being the mother of invention, they also conjured up new testing machines to simulate and stress every part, pilot or procedure.
Greenwald did vibration analysis for the Saturn booster rockets, “The major concern was that when you fired a liquid propellant,” he remembers, “the thrust builds up to the point where you can no longer control it. Four rocket engines may fire but if the thrust differentials between the engines were even microseconds apart you lost control of the rocket.” It took hundreds of static firing tests for Greenwald and the other engineers to solve that problem.
Greenwald spent five years in aerospace engineering before leaving to pursue a doctoral degree at Oxford University in England. In 1968, Robert Duthie, the Nuffield Professor of Orthopaedic Surgery at Oxford said to Greenwald, “We have this chap Charnley coming. He’s doing this experimental surgery.” And Duthie, who actually wasn’t sure Charnley’s surgery would ever catch on, asked Greenwald to put together a companion talk about biomechanics of the hip.
Which Greenwald did. His lab work was published in the journal Nature, titled: “Incongruent Surfaces in the Human Hip.”
To measure the articulating surfaces of the hip joint, Greenwald developed a three-legged micrometer gauge which measured the curvature of both the femoral head and the acetabulum surfaces of the hip joint. He used 53 cadaver hips of widely varying ages to gather data. He calculated the radius of curvature at four points which were equidistant from each other along an equatorial circle. The data clearly showed that there were substantial differences in curvature from point to point on both the acetabulum and the femoral head.
The joint surfaces, Greenwald proved, were not spherical and could not be congruent. Furthermore, said Greenwald, because the hip joint is incongruent, the site and size of the actual contact areas will depend on the position of the joint and the magnitude and direction of the applied load.
Bottom line, the human hip did not articulate as a ball and socket joint!
By inference, then, a ball and socket prosthesis could well alter the direction and magnitude of biomechanical forces in the hip, the adjoining spine, the knee…essentially radiating entirely new forces throughout the musculoskeletal system.
Charnley, who based his hip replacement design on the premise that the hip was a ball and socket joint, gave his presentation at Nuffield first and Greenwald followed. A few days later, Charnley sent a sharply critical note telling Greenwald he was absolutely wrong and furthermore, after performing hundreds of hip surgeries he knew that human hips were balls and sockets.
Greenwald and the FDA
Thirteen years later, after Greenwald had formalized his approach to orthopedic testing and product development at both the Cleveland Clinic Foundation and at the Cleveland Research Institute, DePuy contacted him for help with a novel meniscal bearing and rotating platform knee designs and their FDA submissions, which appeared stalled. The New Jersey meniscal bearing knee and rotating platform knees (developed by Michael Pappas and Frederick Buechel) were the first knee designs where the tibial inserts moved. The FDA, quite rightly concerned, in effect said, “There is nothing like these designs. You have to do an IDE; PMA complete with mechanical testing.” So DePuy turned to Greenwald.
As a true “first”, the New Jersey meniscal bearing knee required Greenwald to develop an entirely new testing machine. Which he did. After 5 million cycles, DePuy’s meniscal bearing knee design survived as did the rotating platform.
Greenwald still remembers the experience. “The FDA panel, consisted of my colleagues including the Chairman Eric Radin, were not interested in hearing from DePuy’s surgeons who had all implanted the unapproved device. All they wanted to know was the testing results. I was the only person that had done any testing. They talked to me for an hour. Based on what I told them, they approved the meniscal bearing knee with the rotating platform to follow.”
Three months after Greenwald’s groundbreaking presentation, the FDA asked him to join the orthopedic advisory panel. He would serve on that panel for 13 years including a stint as chairman.
Charnley, Müller and the AO
After his Nature paper in 1968 and the back and forth with John Charnley, Greenwald’s star was rising. Henry Mankin, who’d recently left New York’s Hospital for Joint Disease (now better known as the NYU Langone Orthopedic Hospital) for Harvard where he accepted the Edith M. Ashley Professorship of Orthopedic Surgery, was a growing fan. C. McCollister Evarits, formerly one of Robert Duthie’s residents, was now Chairman of Orthopaedics at the Cleveland Clinic and would become instrumental in getting Greenwald to Cleveland.
In 1967, Müller founded Protek AG, to market the Charnley-Muller hip prostheses. Profits from Müller’s companies funded the Maurice E. Müller foundation and, over the years, other foundations which advanced orthopedic surgery education and research.
In 1974, Maurice Edmond Müller, Professor at the University of Bern and Head of Orthopaedic Surgery at the Inselspital in Bern asked Greenwald to come to Switzerland and design a proper orthopedic laboratory.
Müller, who co-founded the AO Foundation (Arbeitsgemeinschaft für Osteosynthesefragen) had visited Charnley’s Wrightington lab many times during the 1960s. In 1967, one year before Charnley’s fateful meeting with Greenwald, Müller started his own large-scale production of Charnley’s hip through Protek AG (which later merged with Sulzer Medica, and then spun off as Centerpulse and, finally, acquired by Warsaw, Indiana-based Zimmer, Inc.).
Charnley agreed to lend his name to the Protek manufactured implant and the Charnley-Müller prosthesis was born.
Then…Müller decided to make the prosthetic head bigger (30mm), increase the number of neck lengths and drop Charnley’s osteotomy of the great trochanter in order to insert the femoral component.
Charnley was not happy. He retracted his support saying in a 1970 letter, “…those manufacturers who in the past have made the Charnley-Müller with the 30 mm head should now drop my name…Müller attached my name to his prosthesis out of courtesy because we are close personal friends and because he was acknowledging my pioneer work…The situation has now changed in so far as my operation is certainly a more extensive mechanical procedure than his…”
Greenwald spent two months in 1974 in Switzerland with Müller, developing a plan for a first-of-its-kind orthopedic research and development lab—which was inclusive of:
- An electronics facility to develop and fabricate electro/mechanical surgical instruments
- A machine shop for prototyping new surgical tools and implants
- A histology lab to prepare biological and implant material for microscopic analysis
- A tissue and biomaterials lab to study the failure modes of new biomaterials
- An illustration and reproduction facility to create graphs, charts, exhibits
- An animal surgical suite with facilities
- A film studio and gait laboratory to support educational and information dissemination
- A bio-mechanical and materials testing lab
- Project research labs which visiting surgeons could use to carry out their personal research
Greenwald also proposed that the Müller Foundation integrate an educational program for visiting surgeons. Müller accepted it all and asked Greenwald to stay on as the lab’s first director.
Greenwald deferred, returning to Cleveland, eventually, to utilize almost precisely the same plan he’d given Müller to start the Cleveland Research Institute…where the modern spinal implant industry would first take root.
In 2002, the International Society of Orthopaedic Surgery and Traumatology (SICOT) named Müller the “Orthopedic Surgeon of the Century” and in 2016, Greenwald received the SICOT Medal for Contributions to Orthopaedic Surgeon Education.
As for Charnley, over the years his antipathy for the Müller/Greenwald approaches continued. In speeches and writing, he expressed his staunch skepticism of the AO techniques and principles maintaining that the best experimental model was inferior to an adequate clinical judgment.
In Part II: The Cleveland Research Institute Begins, Art Steffee, Frank Janzen and the first battle in the Spine Patent Wars.
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| A Pittsburgh native, Dr. Mankin graduated from The School of Medicine at the University of Pittsburgh in the Class of 1953. In 1960, Dr. Mankin completed his orthopedic surgery residency at the Hospital for Joint Disease in New York, where he started his career as a Professor and Director of Orthopaedics, followed by time at Mt. Sinai Hospital before ultimately moving to Boston in 1972. At Mass General, Dr. Mankin was Chief of Orthopedic Surgery from 1972 to 1996, as well as the Edith M Ashley Professor of Orthopedic Surgery at Harvard Medical School. Upon arrival to Mass General, he brought fellow orthopedic educators, including the late Drs. Richard Smith, Michael Ehrlich, and Robert Leffert.
Dr. Mankin wrote more than 600 publications and world-renowned lectures. Dr. Henry Mankin left an indelible mark on orthopedic surgery and the world in general. |
A Swiss surgeon and entrepreneur, Dr. Müller developed many internal fixation techniques to treat bone fractures and significantly advanced hip prostheses development. He has been honored with numerous awards including when the International Society of Orthopaedic Surgery and Traumatology (SICOT) named him the “Orthopedic Surgeon of the Century” at a congress in San Diego. Müller was also the patron who founded the Zentrum Paul Klee in Berne, Switzerland.
He worked in Jimma in Ethiopia, in Liestal, in Fribourg, and in 1957 began his orthopedic practice in Zürich. In 1960 he became Chair of the Department of Orthopaedics and Traumatology at the hospital of St. Gallen. From 1963 to 1980 he was Professor at the University of Berne and Head of Orthopaedic Surgery at the Inselspital in Berne. In 1958, Müller co-founded the Arbeitsgemeinschaft für Osteosynthesefragen. Inspired by the work of Belgian surgeon Robert Danis, Müller developed new tools and fixation implants for orthopedic surgery, marketed by Synthes Holding AG. |
