Joint Replacement Surgery

Joint Replacement surgery has undoubtedly proven to be one of the milestone advancements in medicine during the last century. With the development of better materials and techniques, surgeons well-trained in this surgery, can reproducibly produce good results for their patients, alleviating their pain, suffering and disability. Millions of patients worldwide have benefitted from this surgery, experiencing a new life in their crippled limbs.


Though most of the joints of the body have been successfully replaced, it’s the knees and the hips which are the most important for a mobile life, and the bulk of the practice and research in joint replacements is devoted to these joints.


Total Knee Replacement (TKR)

            Osteoarthritis of the knees has assumed epidemic proportions in our country. Our social, cultural and religious activities encourage us to squat, kneel and sit cross-legged. These postures involve bending the knees to a great extent, and, pose enormous stresses on the joints, leading to their wear-and-tear. Though our forefathers could tolerate these stresses to a greater extent, with increasingly sedentary lifestyles and westernized diets, our bodies are now not as tolerant. Hence, osteoarthritis is now affecting an increasingly greater proportion of populations, with those even in the age group of 30 to 50 years being commonly affected.

            
What is this ‘osteoarthritis’? Its not some dreaded disease, like rheumatoid arthritis (gathiya), but simply, wear-and-tear of the protective layer covering the bones making the joint, called ‘articular cartilage’. Once this cushioning layer wears off, our bones start rubbing each other, producing a characteristic sound (crepitus), and, more importantly, pain. To start with, this pain is present on the inner sides of the joint, and is only experienced in activities like descending stairs, or getting up from a chair. At this stage, conservative treatment including activity modification, exercises, knee caps, some supplements, and, if required, injections into the joint can help. Gradually, the disease advances leading to greater pain, present with all walking activity, or even at rest, and to deformities of the joint. This is when total knee replacement is the treatment to restore pain-free mobility to the patient.

            Total knee replacement (TKR) involves shaving off the bones forming the knee joint- namely femur (thigh bone), tibia (shin bone) and patella (knee cap), and replacing them with artificial components, made of a special metal alloy (cobalt-chrome, titanium or oxinium), with a plastic insert between them. These components are accurately matched to the size of the patient’s own bones, and are placed in a very careful manner, so that, to correct the deformities of the leg. The components are fixed with a special ‘cement’ to the bones. This gives a painless, smooth surface to the joints, and the patient can get back to his active life.

With constant evolution of design, materials, manufacturing processes and, most importantly, surgical techniques, this ‘artificial’ joint usually serves the patient for 20 to 30 years, thus, lasting his or her lifetime. Then, if need arises, the plastic insert can be replaced with a newer one by a simple surgery, or in some cases, all the components are taken out, and fresh components are put, in a revision TKR.


Partial Knee Replacement

            With the increasing incidence of osteoarthritis in younger population, alternatives to knee replacement were sought. High tibial osteotomy (HTO) was one such procedure, in which the alignment of the knee joint is corrected to neutral alignment, and as a result, progression of osteoarthritis is halted or atleast retarded. This procedure is only effective in early osteoarthritis when the disease is limited to the medial compartment. The advantage of this procedure is that the native joint is preserved, and a future knee replacement can be avoided or atleast delayed for 10-20 years. However, the pain relief obtained after this surgery is not always reliable. Hence, the enthusiasm for HTO is going down, esp in the western countries, and partial knee replacement procedures addressing only the affected knee compartments gradually gained popularity. Unicompartmental knee replacement and patellofemoral knee replacement are two such procedures.

            
Unicompartmental knee replacement (UKR) involves replacement of the articulating surfaces only on the affected medial (inner) or lateral (outer) side of the knee, without sacrifice of any of the knee ligaments. Hence, there is a more ‘natural’ feel to the knee
as compared to a total knee replacement (TKR). And since much less bone is resected in comparison to that in a TKR, a future revision after 15-20 years can be simpler than that after a TKR. Also, there is shorter incision, shorter surgical time, lesser morbidity and earlier functional recovery. UKR is indicated only when the wear-and-tear is limited only to the medial or lateral compartment.

            Patellofemoral knee replacement (PFKR) involves replacement of the worn-out surfaces of the articulation of the patella (knee cap). Isolated patellofemoral arthritis manifests itself as pain in front of the knee mainly on ascending/descending stairs or getting up from a chair. This can be successfully treated by PFKR. In this procedure, the bones and ligaments of the main joint are preserved.


Total Hip Replacement (THR)

            
         Hip Replacement surgery has been in vogue for over 30 years, before knee replacements became popular, and has consistently given good results to the patients. The hip joint is a ball-and-socket joint, and has a great deal of inherent mobility. The hip is even more important for mobility than the knee. Any disease involving the hip joint leads to immense difficulty in walking, and results in severe disability. Once the destruction of the hip joint occurs, like in knees, Hip Replacement surgery remains the only option.
      
  Unlike knees, primary osteoarthritis of the hips is not commonly seen in Asian populations. But, hip joints may develop osteonecrosis, osteoarthritis infections secondary (including to tuberculosis), trauma (ball and socket fractures) and childhood hip diseases (like developmental dysplasia of hips, Perthe’s disease). Other arthritic processes, like ankylosing spondylitis and rheumatoid arthritis also commonly involve the hip joint. Osteonecrosis, or avascular necrosis (AVN), of hip involves collapse and destruction of the ball (femur head) due to interruption of its blood supply, which may be due to alcohol usage, steroid intake, or without any cause (idiopathic). These diseases of the hip can be seen in young to middle-aged people, and hence, hip replacements should last even longer than knee replacements. This has been achieved with the newer uncemented hips with high-performance bearings like ceramic-on-ceramic, metal-on-metal, etc. These can last upto 30 to 40 years with negligible wear of these newer materials as compared to polyethylene.

           Fractures of the hip in the elderly population are very common due to weakened bones and predisposition to falls. Traditional fixation of these fractures with screws or nails is not successful in all cases, and the current treatment of choice is a partial or total hip replacement. Cemented hips are commonly used in these people due to decreased costs, and early mobilization.

            
          


Partial Hip Replacement

            If the disease involves only one part of the joint (femur head), like hip fractures in elderly, only the affected part can be replaced, and the other half of the joint (acetabulum) can be left as such, in a partial hip replacement or hemiarthroplasty.







            
The advantages of hemiarthroplasty over total hip arthroplasty are decreased surgical morbidity due to a relatively less extensive surgery, and a slightly lower rate of post-operative dislocations. Besides these, the cost can be quite handy with some coutry-made implants. However, the long term survival of hemiarthroplasty is in the range of 10-20 years, after which the socket (acetabulum) wears out, and then it has to converted into a total hip replacement. Hence, hemiarthroplasty is now considered only for elderly, low-demand patients, and total hip arthroplasty is the preferred surgery for younger patients.


FAQ's             

Q: What is the success rate of Joint Replacements?

A: Joint Replacement is one of the most successful procedures ever, which if performed by a surgeon well-trained in this art, has a success rate of over 99% over the short term. The only major immediate complication is infection, whose incidence has been reduced to <0.5 % with current aseptic techniques and antibiotic prophylaxis.

      The long term survival of the prosthetic joints depends on the materials, industrial processes, age/activity level of patient, bone quality, and of course, surgical accuracy. Most of the quality joints available today have over 95% survival rate at 25 years.


Q: What is the minimum age after which one can/should undergo total joint replacements?

A: Once the bony growth has completed, by the age of 14-16 years in girls, and 16-18 years in boys, anyone can undergo Joint Replacement, if need arises. However, since the long term survival of this artificial joint is in the range of 25-35 years, this procedure should be undertaken, only if essential under the age of 40.


Q: What is the recovery period after a Joint Replacement surgery?

A: With the evolution of quality of fixation, and confidence of surgeons, there is no ‘bed-rest’ after Joint Replacement surgeries now-a-days. The patient gets moving the day after the surgery, with the aid of a walker. Bedside exercises are taught by the physiotherapist, and by the time of discharge 5-7 days after the surgery, the patient is relatively pain-free, and can carry out his day-to-day activities without any assistance. Some kind of walking aid is continued for 6 weeks after surgery. It takes 3 months to gain adequate strength, and normal gait after the surgery.


Q: What is the role of CAS (computer-aided surgery) or ‘navigation’ in Joint Replacements?

A: With the aid of some laser markers put on bones and instruments, a computer software can ‘guide’ the surgeon regarding the direction of bone cuts, and magnitude of soft-tissue releases. However, apart from a few complicated cases, with the most severe deformities, this computer ‘guidance’ has not been found to add to the accuracy of surgeons well-trained and experienced in Joint Replacements. On the other hand, it makes the surgery longer (thereby increasing the surgical morbidity and infection rate), and more expensive (the navigation system comes at a prohibitive price!). However, few orthopaedic surgeons find it more comforting to use technology, to be sure of their accuracy, and to convince patients that they are giving the best results, which may not be always the case.