…….Recreating Human Anatomy With Little Help From Technology
Joint replacements have come a long way. It is a great pleasure to be able to be of some service to the society by making arthritics pain-free, mobile and independent. For the last decade or so, you might have noticed a marked increase in the number of elderly relatives or friends having undergone hip or knee replacement surgeries. Typically, these elderly people get a pain-free joint for ten years or so following the surgery. They had arthritis set in with old age, and the joint replacement surgery gave then a new lease of life.
This gave them relief from pain and enhanced their mobility. However, this surgery did not allow them very good range of movement or any sporting activity. They had to follow several restrictions in order to have long-lasting results. Squatting, cross legged sitting and any impact activities were forbidden forever.
While traditional joint replacement suited elderly patients as they were happy with the outcome, youngsters have been typically unsuitable for joint replacements because they are high-demand individuals and would shake their joints loose in no time. Not fair. Why should youngsters not have all the excitement they deserve? There are so many young people out there with disabling arthritis. Surely they cannot be deprived of freedom from pain.
The only reliable solution for the “end stage arthritis” is “replacement” of the worn out joint and fortunately, things have changed for good.
Joint replacements surgeries have been attempted well over a century and surgeons have experimented with different materials and hardware for building artificial joints (referred to as prostheses). Early joints were designed from unlikely materials like wood and ivory. Naturally, they failed miserably. Then came unrefined metals like industrial-grade steel and soft plastics like acrylic. Unfortunately, they also failed to get the desired outcomes.
Artificial joints made from Cobalt-Chrome and Titanium were the first success story in joint replacements. However, what changed the scenario profoundly was the invention of PMMA bone cement. Interestingly, even this goes back as long as seventy-five years. PMMA bone cement helped in conducting the first historically-successful joint replacement.
While those were good for elderly people with limited mobility and whose primary concern was the relief from the pain, these joint replacements did not work for young and active people.
Over last few years, there have been major advances on multiple fronts, which incrementally built in the reliability and longevity in the traditional artificial joints. Broadly speaking, there have been significant advancements in terms of materials, design, pre-operative planning, techniques and training. All of these improvements have allowed us to offer the option of surgery even to the young patients, who are looking to get rid of the pain as well as lead normal physically active life.
The materials with which joints are made have seen significant improvements. The classic material like Stainless Steel and Cobalt-Chrome still remain the favourite material for most classic joint replacements. Newer alloys are strong, yet lightweight. They are friendly to human bones. They can merge with the bones and stay attached for decades without any failure or rusting. These artificial joints are made of Titanium and Tantalum alloys. They form reliable foundations of joint replacements, which remain anchored with the bones for a significantly long time. raditionally, the surface of the joints is made of a hard-wearing plastic, known as “Ultra high molecular weight Polyethylene”. However durable it may be, it is a type of a plastic and eventually, it will wear out with time, because joint surfaces are moving all the time. Introduction of pink ceramics have offered us a reliable long-lasting solution. Ceramic is a hard material and does not get worn out even after prolonged usage. This has led to greatly enhanced longevity of the joint surfaces. Theoretically, a ceramic joint surface can last for many decades, equivalent to the active life span of most of us.
Use of a high-quality Titanium or Cobalt-Chrome joint with a Ceramic-articulating surface is considered as most reliable artificial joint for a young active individual who needs joint replacement. It allows a near normal activity for the long-term without fear of failure. The joint replacement prosthesis needs to be fixed to the bone in some way.
The classic way to fix the prosthesis to bone is using PMMA Bone Cement, which is basically an acrylic polymer. We have been using it routinely for many patients. It is a very reliable method, where the cement sets in twelve minutes and the joint is ready to use. While it is a boon for elderly patients, it is not so for the young patients. For an active young individual, this cement can be a weak link.
Development of advanced coatings on prosthesis allows the prosthesis to merge with the bone. Porous coats and hydroxy-apatite coating have enabled us to do long-lasting “cement-less joint replacements”. Because there is no cementing which can fail the joint can last much longer.
Having a perfect material of joint replacement is a great achievement. But, will it really work?
It may not work unless we understand the design of our human body. The anatomy of human joints is a beauty. A lot of research has been done to map the geometry of human joint surfaces. A lot of work has also been done (and under way) to understand the dynamics of our body and our joints. This research has led to the design of modern joint replacements, which come quite close to our own human anatomy. Knee joints are particularly complex in its arrangement. Artificial joints have come quite close to their natural design.
The design of the joint replacement plays a crucial role in its functionality as well as life. Today, we have so many policemen, soldiers and sportsmen who are leading a normal life after undergoing modern joint replacements.
It’s great to have a perfect material and a perfect design. To get the desired outcome, we need to have three more things in place: Planning before surgery; the art of performing the surgery; and proper rehabilitation after the surgery.
Advances in technology are helping. Advances in materials and machining technologies are enabling orthopedics to get perfect alloys and ceramic surface for joint replacements that are close to natural. Computer-based technology is also helping orthopedics to get the precise design for joint replacements. Technology is also enabling us in planning precisely.
CT Scans of the joints are used with a 3D printer to obtain exact mapping of the worn-out joint. These technologies help orthopedics to plan how exactly to deal with the joint in the operation theatre and there are no unpleasant surprises during surgery. Advances in technology are helping us do thorough planning well before going into the surgery.
The surgical handicraft has also vastly improved. Minimally invasive approach gives patients a huge relief from pain. Earlier, patients had to stay in the hospital well over a week following a single knee replacement. Now, the time for which a patient needs to stay in hospital is hardly four or five days. In the modern surgeries, the blood loss is much less and usually a blood transfusion is not required. The use of computerized navigation during the surgery adds a further bit of precision to the entire knee replacement procedure.
The author is a Sr Consultant, Orthopedics and Joint Replacement with Fortis Hospital, Mulund