Knee replacement surgery or Arthroplasty, as it is professionally referred to, is an orthopedic surgical procedure in which the articular surface of a musculoskeletal joint is replaced, remodeled, or realigned. It is an elective procedure that is done to relieve pain and restore function to the joint after damage by arthritis or some other type of direct or indirect trauma. The procedure involves cutting away damaged bone and cartilage from your thighbone, shinbone and kneecap and replacing it with an artificial joint (prosthesis) made of metal alloys, high-grade plastics and polymers. The prosthesis selected must be nontoxic yet resistant, compatible and durable. Meeting all these criteria usually means that the prosthesis will not last 10–20 years. 75% of artificial knees will last 20 years and 90% will last 10 years.
Knee replacement surgery is a decision that requires meticulous consideration by both the patient and his doctor. In determining whether a knee replacement is right for him, the orthopedic surgeon assesses his knee’s range of motion, stability and strength. X-rays, CT scans and MRIs help determine the extent of damage and if the doctor decides that a knee replacement surgery is indeed required, various different sets of procedures are available. Encouragingly, knee replacement surgeries are one of the most common bone surgeries that are performed around the globe and over 90% of the patients report unprecedented levels of pain reduction and a much greater increase in comfort and their ability to move around which serves as a reliable indicator of how successful and alleviating they are.
There are many different kinds of arthroplasty as listed below:
- Interpositional arthroplasty: This involves the creation of a gap and the insertion of tissues like skin, muscles or tendons to keep the inflammatory surfaces apart. This is the go-to procedure for treating the advanced forms of hallux rigidus.
- Excisional/Resectional arthroplasty: This involves the removal of the joint surface and the attachment of the remaining ends so that in time, the scar tissue can fill in the created gap. One variant of is the Stainsby procedure which consists of excision of part of a proximal phalanx in a metatarsophalangeal joint, reduction of the plantar plate and kirschner wire fixation of the metacarpal bone to the remaining phalanx.
- Resurfacing arthroplasty: The goal of knee resurfacing is to restore the best possible function to the joint by replacing damaged joint surfaces with artificial ones. Modern knee resurfacing systems involve placing a non-cemented porous metal cups on the ends of the articulating surfaces of the bones involved in the formation of the knee joint. This results in an articulating metal-on-metal surface.
- Mold arthroplasty: This involves the interposition of material between the bony surfaces after the removal of synovial membrane and articular cartilage. Another form includes the replacement of the knee joint with a metal hinge.
- Silicone replacement arthroplasty: This involves implantation of prosthetic joints constructed of silicone to replace joints damaged by arthritis, avascular necrosis, trauma; silicone is also used as spacers in certain medical procedures for example Keller’s bunionectomy, local joint complications, breakage/breakdown, dendritic synovitis or osteolysis, loosening of joints from anchoring bone, multinucleated giant cell reaction, erosion through soft tissues etc.
But for the last 45 years, the form of arthroplasty with the greatest success rate is the surgical replacement of arthritic or necrotic joint with a prosthesis. For example, a knee joint that is seriously affected by osteoarthritis may be replaced entirely (total knee arthroplasty) with a prosthetic knee. The purpose of this procedure is to relieve pain, to restore range of motion and to improve walking ability, thus leading to the improvement of muscle strength.
It is congruous with ease of comprehension to divide knee replacement surgeries into their offshoots. Primarily, they are divided into total, partial and bilateral replacement surgeries. Total knee replacement surgeries are pertinent when the damage, inflammation and pain exacerbate to such an extent that a person’s daily activities are considerably marred. This is usually the last resort for such patients when all other non-interventional and interventional procedures have failed to bring about considerable relief. A total knee replacement has a significant success rate and the relevant statistics are only improving with time.
During total knee replacement, the affected knee joint is replaced with artificial material. The knee is a modified hinge joint that provides motion at the point where the thigh meets the lower leg. The thighbone (femur) abuts the large bone of the lower leg (tibia) at the knee joint. During a total knee replacement, the end of the femur bone is removed and replaced with a metal shell. The end of the lower leg bone (tibia) is also removed and replaced with a channeled plastic piece with a metal stem. Depending on the condition of the kneecap portion of the knee joint, a plastic “button” may also be added under the kneecap surface. The artificial components of a total knee replacement are referred to as the prosthesis. The eventual goal involves establishing your knee joint till the point that it is able to bend and flex with markedly increased ease. In some cases, it is not uncommon for the surgeon to replace the undersurface of the kneecap with a plastic coating. In total knee replacement surgery, the posterior cruciate ligament, the ligament that basically stabilizes each side of the knee joint, is either retained, sacrificed, or substituted by a polyethylene post. Each of these various designs of total knee replacement has its own particular benefits and risks.
Total knee replacement surgery is recommended for patients whose knee joints have been deteriorated by either progressive arthritis, trauma, or other rare destructive diseases of the joint. The most common reason for knee replacement in the United States is severe osteoarthritis of the knees. Regardless of the cause of the damage to the joint, the concomitant increasing pain and stiffness and the impaired daily function lead the patient to consider total knee replacement. Decisions regarding whether and when to undergo knee replacement surgery are not that easy since these surgeries demand some major lifestyle alterations and patients should bear that in mind. Patients should understand the associated risks as well as the benefits before making concrete decisions regarding the future of their knees.
Risks of total knee replacement include blood clots in the legs that can travel to the lungs (pulmonary embolism). Pulmonary embolism can cause severe shortness of breath, chest pain, and even shock in dire cases. Other risks include urinary tract infection, nausea and vomiting (usually related to pain medication), chronic knee pain and stiffness, bleeding into the knee joint, nerve damage, multiple blood vessel injuries, and infection of the knee which can require reoperation. Furthermore, the risks of anesthesia include potential heart, lung, kidney, and liver damage.
A partial knee replacement on the other hand only involves replacing the part of the knee that is damaged or arthritic. This procedure requires a smaller incision and therefore less blood loss. Partial knee replacement surgery removes damaged tissue and bone in the knee joint. It is done when arthritis is present in only part of the knee. The areas are replaced with an artificial implant, called a prosthetic. The rest of the knee is preserved. Since partial knee replacements are most often done with smaller incisions, so there is less recovery time.
A partial knee arthroplasty is a viable option if a specified region of the knee is affected by arthritis or any other joint-degrading disease. In order to opt for this procedure, the patient should have a relatively mobile knee which isn’t completely invaded by arthritis, especially under the kneecap. The patient should have his ligaments intact and no major defects of the knee. Such a procedure is most often carried out in people aged 60 and/or older. Not all people can have a partial knee replacement. They may not be very good candidates if their conditions are far too severe. Also, the patient’s medical and physical condition may not allow him to have the procedure.
However, a partial knee arthroplasty has a few risks associated with it as well. They include blood clots, fluid buildups in the knee, failure of the replaced parts to attach to the knee, nerve damage, vascular damage, associated pain and in the rarest of conditions, reflex sympathetic dystrophy which is a disorder that causes lasting pain, usually in an arm or leg, and it shows up after an injury, stroke, or even heart attack. But the severity of pain is typically worse than the original injury itself. Reflex sympathetic dystrophy is now commonly known as Type I Complex Regional Pain Syndrome (CRPS).
Another avenue that patients can opt for is the bilateral knee replacement. A bilateral knee replacement is only suggested to patients who have both of their knees infested by severe, crippling arthritis. However, more risk is associated with this type of surgery, so it is typically only recommended to those who are in relatively better health and are motivated enough to undergo the surgeries and later on the rehabilitation process to fully recover. As the name suggests, this procedure involves replacement of both of one’s knees. Double knee replacement surgery may involve either one surgery or two. When both the knees are replaced at the same time, the surgery is known as a simultaneous bilateral knee replacement whereas when each knee is replaced at a different time, it is called a staged bilateral knee replacement. Either surgery may involve any combination of total knee replacement or partial knee replacement.
Since in the case of simultaneous bilateral knee replacement both of the knees are replaced during the same surgery, the primary advantage is that there is only a single hospital stay and only one rehabilitation period to go through in order to heal both the knees. However, rehabilitation is considerably slower, as it is more difficult to use both knees at the same time. In fact, many people who undergo simultaneous bilateral knee surgery need assistance at home while they are recovering. This type of procedure also takes longer to perform. Simultaneous bilateral knee replacement typically takes three to four hours to complete, while staged bilateral knee replacement only takes about only two hours. Since simultaneous bilateral knee replacement requires more time and heavier doses of anesthesia, there is an increased risk of post-surgery complications. This surgery isn’t recommended for those suffering from cardiac or pulmonary conditions. These high-risk groups may experience dire heart problems or excessive blood loss during and/or after surgery.
As far as a staged bilateral knee replacement is concerned, both the knees are replaced during two separate surgeries. These surgeries are performed a few months apart. Each surgery lasts about two hours. This staged approach allows for one knee to recover before the second knee undergoes surgery. The foremost advantage of a staged procedure is the reduced risk of complications. It also requires a shorter hospital stay. However, since this procedure requires two surgeries, the overall rehabilitation period is much more prolonged.
Before these surgeries, the patients are expected to give their medical history and partake in a few routine tests. The doctor will likely use the results from these tests to paint an accurate picture of the extent of damage done to the knee. The doctor will also be interested in knowing how strong the muscle support around a patient’s knee is, and how well they can move the joint. This will enable the surgeon to design a well-equipped and informed plan of action regarding the patient’s condition and go with the most feasible option as per the patient’s demands.
Lamentably, it’s not all rainbows and butterflies after going through these Arthroplastic procedures. About 10 per cent will be less than satisfied with the results. Some of the reasons are obvious, including postoperative infection or a bone fracture around their replacement. However, the most common reason is the development of persistent pain around the newly replaced joint. The most pivotal of steps in finding a solution to persistent discomfort is to first figure out the cause of pain. Listed below are most common causes of pain after knee replacement:
- Loosening of the implant: This is most often the cause of pain years or decades after the knee replacement. However, it is seldom the cause of persistent pain immediately after surgery.
- Infection: Infection is a serious concern that warrants apprehension. Any increase in pain after knee replacement should raise flags for infection. Frequently, the signs of infection are apparent, but subtle infections may be the cause of persistent discomfort.
- Patellofemoral (kneecap) problems: Significant forces are applied to the kneecap, even with normal activities, such as getting up from a chair or walking down the stairs. Getting a kneecap to perform well with a replacement can be technically challenging even for a skilled surgeon. And if it is not carried out perfectly, an improperly fixed kneecap can prove to be very agonizing.
- Alignment problems: Many patients focus on the knee replacement implant brand or type. A poorly aligned implant may not function well, no matter its quality. Surgeons are investigating if computer navigation will help improve implant alignment. An unaligned implant can cause severe valgus and can be very discomforting in the long run.
Other issues that can cause persistent pain include bursitis, complex regional pain syndrome, and pinched nerves. However, they are not very bothersome, since with proper precautions and skillful hands, most of these can be avoided.
After the surgery, the biggest challenge that awaits the patient is successful rehabilitation. Knee replacement surgeries usually require an in-hospital stay of several days. During this time, the patient’s progress is monitored and physiotherapist is assigned to the patient. Physiotherapy is by far the most important part of a successful recovery so it should be given utmost importance. A Continuous Passive Movement (CPM) machine is used to begin the process of physiotherapy. This machine moves the new knee joint through its range of motion while the patient rests in bed. The pain levels are controlled with medication so that the patient can partake in the exercises.
Although the hospital follow-up is very important, most of the recovery takes place at home. Once at home, it is important to keep the surgical area clean and dry. The doctor advises specific bathing instructions to minimize the risk of infection. The stitches or surgical staples are usually removed during a follow-up hospital visit. Physiotherapy should be continued and it is important to resume normal activities as soon as possible after the patient is discharged from the hospital. Walks for as long a period of time as possible are highly recommended, even if mechanical assistance in the form of crutches and walkers is required. Furthermore, he patient should continue to take all medicines prescribed by his doctor. He shouldn’t stop taking antibiotics, blood thinners, or other medication simply because he feels better. Such medications should be stopped only if his doctor tells him to.
All in all, knee replacement surgeries are highly effective and paint a very hopeful and optimistic future for those with diseased knees. Although they are pretty expensive and have a degree of risk associated with them, the good greatly outweighs the bad. With the ever-advancing scientific research and the heavy backing of medicinal procedures, knee replacement surgeries have a very bright future ahead of them. One with reduced risks and associated complications and happier patients with healthier knees.