The year, 1950 was a landmark in development of joint replacements. European designs set a milestone in evolution of it. The article mentions about its evolutionary phases, giving safe, pain free and lasting results to millions, and now the robotics is taking a front seat.

First ever orthopaedic prostheses and implants were found in Egyptian mummies dating back to over 3000 years ago. It makes us wonder how they had this technology that time. However, it was rudimentary and surgical techniques were not evolved. Surgery became successful only after we realised importance of hand washing and sterilisation. Antibiotics improved results and surgical procedures became a norm.

Last millennium ended with the twentieth century. Three surgeries became well known as the most successful and life changing procedures of the twentieth century; they were – cataract operation, cardiac bypass and hip replacement.

Because of arthritis and injuries ,our joints tend to get irreversibly damaged leaving us immobile and in pain. Joint replacement gives us freedom from pain as well as ability to enjoy life. Today, we are able to replace so many joints in the body. Hip and knee replacements are known to everyone. We can do shoulder, elbow, wrist, ankle, joints of fingers and toes. Even discs in backbone can be replaced. In this millennium, we have progressed by leaps and bounds. It’s very interesting to know how joint replacements evolved. Although ancient Mayans and Egyptians implanted shells and ivory as tooth implants, they were not aware that these materials are not friendly with our body. Bone pegs, Ivory rods, silver rods, copper wires etc., were tried to fix bones between fifteenth and nineteenth century. Even wooden balls were tried out to replace joints of the jawbone. The failure was because these materials are not inert and our body rejects them. Also they don’t last.

Subsequently, various types of hip replacements were attempted. Hip joint is a ball and socket joint, which connects our legs to the body. It is a weight bearing joint, taking the entire load of our body. Ivory hip was the first one to be designed. Then someone used a glass cup as a socket of hip. As early as 1930s acrylic hip replacement was designed. Although these designs failed, perhaps the “Acrylic hip” was the first successful design. Failures were because of multifold reasons; most of these materials were incompatible with human body, they were not wear resistant, so failure was quick, glass was brittle and would eventually shatter or the prosthesis would not anchor in bone leading to loosening. Although all of these materials failed, the acrylic hip design was carried forward for many decades and still similar joints continue to be made. Credit goes to Judet brothers.

First breakthrough came after the introduction of cobalt chrome alloy in medical devices. Cobalt chrome is smooth; can be given mirror finish; is very hard – therefore wear resistant. It is very strong, long lasting yet inert to the human body. Dr Austin T. Moore from North Carolina and Thompson from New York separately designed cobalt chrome hip replacements which were the first ones to succeed. Similar designs remain in use worldwide, till date. Although “Austin Moore” and “Thompson” prostheses were pioneering designs they were not blessed with longevity in all cases.

While these American designs were enjoying success, a British Mastermind Sir John Charnley was working in his garage to design a hip replacement which was destined to be so successful that the results and longevity are still considered a gold standard. He used completely different materials. Thus 1950 was a landmark in development of joint replacements. The materials he used are still widely used after seventy years.

He was a hands on person; an orthopaedic surgeon and an engineer. After working in an Orthopaedic unit near Manchester, he would come home and work in his garage workshop on various implant designs. He used Plexiglas or Acrylic cement. This is like epoxy where acrylic liquid is mixed with acrylic powder and the cement sets in fifteen minutes. Acrylic cement was first used in 1930s by plastic surgeons to bridge gaps in skull bones. Other material he used was high density polyethylene.

John Charnley developed this “Charnley Hip”. It had a stainless steel stem and head construct which was fixed in thighbone using bone cement. The high density polyethylene socket which was fixed in pelvis using bone cement. Normally, the size of femur head (ball of the hip) is around 50mm. Charnley hip had head size of 22mm. Much smaller than normal head, giving rise to the celebrated concept of “low friction hip replacement”.

Charnley hips lasted for decades. It was common to see patients, who had surgery thirty or forty years back, still walking strong. When I went to work in England, I was fortunate enough to meet patients who had hip replacement done by Charnley himself. Such was the serendipity; a pleasant coincidence! Charnley got the perfect materials; bone cement, HDPE socket and steel stem which will be unbeaten into the next millennium.

Around same time, a Swiss surgeon Maurice Muller designed the hip with 32mm head size.

In south coast of England at Exeter, RSM Ling designed a hip replacement which has become a classic design for hip replacement stems. He used polished, double tapered stainless steel set, which when cemented in thigh bone, would last almost lifelong. These European designs set a milestone in evolution of joint replacement.

Norfolk and Norwich Hospital in England is – where I started my career in England. We used to have our academic meetings in Mckee lecture hall. Mckee and Farrar were legendary surgeons who designed the “metal on metal” hip joint, the very first of its kind. This robust joint could let people do activities of their choice. This laid foundations for the famous “Birmingham metal on metal hip”. Perhaps, it’s the most robust hardware ever to be designed, to go in human body and last for decades.

While the materials of joint replacements were evolving every decade, the surgical techniques were being perfected in every possible way. Along with hip replacement, effects were on to be able to replace other joints in the body, like the shoulder, elbow etc., to benefit patients with Arthritis. In older days, joint replacement was a major undertaking. It was a lengthy, complicated surgery leading to lot of blood loss and extended hospital stay. As the surgical and anaesthetic techniques evolved, we could do these surgeries quickly, using tissue friendly techniques; blood loss became minimal. Post-operative pain control improved and thus joint replacements became widespread and popular, giving safe, pain free and lasting results to millions.

Titanium alloys were developed around second world war time. Titanium is light, strong and especially friendly to bone. It quickly gained popularity in the field of prosthetic design and stayed there. Further advances came along in seventies and eighties. The articulating surfaces of prosthetic joints evolved after ceramics came into play. Ceramic balls and bearings almost never wear out, increasing longevity and robustness of joints further. The fixation of these prostheses to bone pioneered by John Charnley, using acrylic cement evolved in a very unique way. Methods were devised to coat the prosthetic joints with “calcium hydroxyapatite” or titanium wire mesh, making the prosthesis a bone friendly device. Such prostheses literally “healed” to bone to become permanent part of our body. This allowed us to perform joint replacement surgeries for much younger people.

In the old days, joint replacements were only performed on senior patients. Now it’s a huge boon to many young sufferers of arthritis, who would be otherwise crippled. We perform “cement less ceramic joint replacements” for young people where coated titanium alloy prostheses are used along with ceramic bearings.

Small joints like fingers are lightweight so, carbon joints were developed for them.

While a lot of work was done to invent hip prostheses between 1930 and 1950, just a decade later Gunston from Canada and Insall from New York managed to design the first successful knee replacement. Unlike hip joint the knee joint is a hinge which also rotates. Our knees are complex structures. Knee replacements demanded not only a successful design, but also a perfectly designed surgical technique. Lots of specially designed instruments were also required in order to perform the surgery. From the geometrically deigned knee replacement, significant advances were made to what we use today. At present we use an “anatomically designed” knee prosthesis which behaves exactly like a normal knee. Not only that, it is performed in a tissue friendly manner where surgery is swift, accurate and with minimal tissue trauma. Pain control techniques are so good that we are able to safely perform single sitting both sided knee replacements.

Insall continued to improve on the mechanical instrumentations throughout seventies and eighties. The longevity of knee replacements went to 90% at fifteen years, which was commendable. First out of the box idea was to give visual inputs to a computer and the computer then will work out geometry of the carpentry during the surgery. This was called “navigated total knee replacement”. During surgery once the bones are exposed, tiny pins are fixed to bones – the pins have reflective ends. Computer maps the entire knee joint with the help of infra-red beams. Entire surgical planning is then displayed on screen where we can figure out how many millimeters bone to cut, and at what angle. This improved the accuracy of knee replacements. Certain extremely difficult cases which were previously inoperable could now be given excellent results using computerized navigation.

Further improvement on the navigation was done in such a way that all this planning is done in surgeon’s office day before surgery. This is “customized knee replacement”. Patient’s CT scan of the knee is entered in to the computer, where the computer plans out geometry and math well in advance. Then a 3D printed jigs are custom made to facilitate surgery using these calculations. The surgery can be performed with extreme precision and with a predictable error free outcome.

A combination of conventional surgical technique, computerized navigation and CT scan based customization has resulted in the latest “Robotic” technology for joint replacements. Here the surgeon guides the robotic arm to perform the perfect bony cuts to give patient the ideal joint replacement. It has been quite a journey, especially since last ninety years. The success story started with introduction of cobalt chrome and stainless steel in the early joint replacements. Subsequent advances with titanium alloys, ceramics and pyrocarbons perfected the materials. Better understanding of anatomy gave us the perfectly designed prostheses. Improved surgical training made surgeries safe and pain free for patients.

Technological innovations led to introduction of computers, and finally robotics has to play a major role in giving freedom from pain to many.

Dr Sachin Bhonsle,
Senior Consultant, Joint
Replacement Surgeon, Fortis
Hospitals, Mulund.

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