1. Does knee replacement involve replacing the entire joint?
Is knee replacement the replacement of the entire knee joint?
Prof. Guan Zhenpeng: This is a wrong understanding. Many people mistakenly believe that joint replacement means replacing all the joints, but in fact, joint replacement is also called surface replacement, which is equivalent to replacing the parts of the joint. Specifically, because the cartilage on the surface of the knee joint is worn out, a joint replacement only replaces this layer of cartilage, which is a very thin layer on the surface, and then puts a metal joint on it, which is similar to putting a brace on a broken tooth. Finally, a “plastic pad”, a high-density polyethylene joint surface, is added between the two metal joints for shock absorption. This allows the patient to regain normal joint function and reduces pain.
After knee replacement, will I be able to function like a normal person? To what extent can I recover?
Professor Guan Zhenpeng: The purpose of knee replacement is to reduce pain and restore the basic function of the joint. After surgery, normal walking and basic living are fine, but kneeling and squatting are only possible for patients who have recovered exceptionally well, and most patients cannot squat or move vigorously after surgery. Most patients are unable to squat or do strenuous activities after surgery. Especially if the patient performs strenuous activities like an athlete after surgery, it will increase the wear and tear on the joint.
Do you still have pain and other symptoms after surgery?
Prof. Zhenpeng Guan: There are two stages of post-operative pain. In the first stage, after the surgery, the pain will appear after the anesthesia has passed, which is the pain caused by the surgery and will gradually disappear with time. Especially this postoperative pain is much lighter than the pain caused by disease before surgery, and during the pain process, the doctor will use various methods, such as analgesics, to eliminate the pain.
In the second stage, after the postoperative joint function is restored, the pain will gradually disappear in more than 95% of patients. According to my experience, about 1/3 of the patients feel that the new artificial joint is as suitable as their own joint one year after surgery, and they do not feel any pain; 1/3 of the patients occasionally feel a little discomfort and pain when it is rainy or cloudy after surgery, which is also normal, because it is an artificial joint after all, and it has a wear and tear process with itself; and 1/3 of the patients have pain because of joint adhesion or functional exercise. In another 1/3 of patients, the pain is caused by joint adhesions or untimely functional exercises, but this pain is much less than the joint pain before surgery and basically does not affect life.
What are the problems that can occur if the knee is not replaced?
Professor Guan Zhenpeng: First of all, we need to understand why we need a joint replacement. There is a layer of cartilage on the surface of the knee joint, which is often referred to as “brittle bone”, and it has no nerves. For various reasons, such as rheumatoid arthritis, ankylosing spondylitis, and joint injury, the cartilage wears away, exposing the bone beneath the cartilage. Unlike cartilage, there are nerves inside the bone, and when the bone wears away, the patient feels pain, and this pain can have an impact on life.
In the early stages, the pain may only be felt when there is more movement, and for patients in their 50s and 60s, they may be hesitant to have surgery. By the time the disease has progressed to an advanced stage, the patient may feel pain even at rest, which has severely affected their lives. At this point, the patient may be 70 years old, and if joint replacement is still not performed, the joint wear will become more and more severe, and eventually the joint will become deformed and stiff, and the patient will be confined to a wheelchair. At the beginning, only one side of the joint may need to be replaced, but at a later stage, both joints will be more severely worn and may require treatment.
2. Which patients are suitable for knee replacement?
Which patients need knee replacement?
Prof. Zhenpeng Guan: There are many causes of joint wear, such as the common osteoarthritis, which has a prevalence of over 50% in people over 60 years old. In addition, some specific types of inflammatory diseases, including rheumatoid, ankylosing spondylitis, and traumatic synovitis of the knee, can also cause wear and tear of joint cartilage.
It is important to understand that normal human joint cartilage has a certain degree of elasticity, and when cartilage is destroyed, it is equivalent to the beads in the axle of a bicycle being worn out, and the bicycle can no longer be ridden. Likewise, when cartilage wears out, the joints cannot move and there is pain.
When this pain interferes with life, joint replacement needs to be considered. If imaging reveals that the joint has worn down more severely, but the patient can still walk, then surgery can be considered based on the individual patient’s condition. If X-rays show that the cartilage has worn away and the patient cannot walk more than 500 meters on their own and it hurts when they do, then knee replacement should be considered.
Are obese patients suitable for knee replacement? Is it necessary to lose weight before replacing the joint?
Prof. Guan Zhenpeng: Obesity itself is one of the causes of osteoarthritis, and when you are overweight, it can aggravate joint wear and tear. In addition, after joint replacement, obesity can increase the wear and tear of the new joint, thus reducing the life of the artificial joint. In this way, obese patients do need to lose weight. However, there is also a practical problem, as the patient cannot lose weight through exercise because he or she has pain when walking before surgery.
Therefore, the problem needs to be viewed in two ways: for particularly obese patients, joint surgery will also be more difficult, the surgical process of wound exposure time, increasing the chances of infection, therefore, it is recommended that preoperative weight loss; for patients who are not particularly obese, it is recommended that the first joint replacement, after the replacement of the joint can be normal exercise, then through exercise to lose weight, otherwise a vicious circle will occur.
3. Can arthritis patients have knee replacements?
Are young arthritis patients suitable for knee replacement?
Professor Guan Zhenpeng: Generally, osteoarthritis is less common in young people, and rheumatoid and ankylosing spondylitis are more common. For example, ankylosing spondylitis is more common between the ages of 20 and 40, and juvenile rheumatoid arthritis develops at the age of 10. By the time a patient is 20 years old, the joints are so badly damaged that they are unable to lead a normal life, such as getting married, having children, or finding a job. At this point, a knee replacement is required.
Although artificial joints have a certain lifespan, young people who have had their joints replaced may have to wait 15 to 20 years before having them replaced again. However, from a quality of life perspective, the best age for a person is at this stage, so you should not wait until you are 60 years old to replace the joint because of the possibility of a second replacement at age 20. Therefore, for young patients, knee replacement is still necessary to increase self-confidence and to integrate into social life.
Is knee replacement suitable if I have been taking hormones for a long time?
Professor Guan Zhenpeng: Some patients with rheumatoid and ankylosing spondylitis must take hormones because of the disease, but taking hormones can cause osteoporosis, so can such patients undergo joint replacement? The answer is yes.
However, it is important to make sure that the doctor is aware of the hormones before surgery so that he or she can provide “hormone protection” before and during surgery. As a result of taking hormones, the patient’s own hormone production is reduced and adrenal cortex function is suppressed. By the time the surgery takes place, the body will have a stressful reaction to the surgery and more hormones will be needed. However, the adrenocortical function is suppressed, and it is no longer possible to produce the normal amount of cortisol, much less the amount needed during stress, so the patient will have a series of symptoms of adrenocortical hormone deficiency: high fever, gastrointestinal disorders, circulatory deficiency, indifference, depression or agitation, delirium or even coma, which is called adrenal crisis. By “hormone protection”, we mean that the doctor takes measures to avoid the occurrence of adrenal crisis.
In addition to prednisone and hydrocortisone, some prescriptions for rheumatoid, asthma and skin diseases may also contain hormones. Such cases also need to inform the attending physician.
4. Can knee replacement be performed in patients with three high levels of diabetes?
Can a diabetic patient have a knee replacement? What range of blood sugar control is needed?
Prof. Guan Zhenpeng: 1/3 to 1/2 of the patients who need joint replacement have diabetes. For diabetic patients, there are two major problems after joint replacement.
The first problem is that the incidence of post-operative infection is three to four times higher than in the general population. After surgery, if a diabetic patient has higher blood sugar and inflammation elsewhere in the body, such as pneumonia and urinary tract infections, bacteria are more likely to multiply in the bloodstream at this time, and these bacteria, if left unchecked, can spread through the bloodstream to the joint replacement, which in turn can cause joint infections. And the most dreaded complication after artificial joint replacement is infection.
The second problem is that post-operative wounds do not heal easily in diabetic patients, which also increases the chances of infection.
Therefore, diabetic patients who want to have a knee replacement must have their blood sugar under control before surgery. It is recommended that fasting blood glucose be controlled at 6-8 mmol/L and not more than 8 mmol/L, and that blood glucose not exceed 10 mmol/L two hours after a meal, and that surgery be considered when blood glucose is stable.
Can patients with high blood pressure and heart disease have knee replacement surgery?
Prof. Zhenpeng Guan: Many elderly people have three highs: high blood sugar, high blood lipids and high blood pressure. Patients who need joint replacement surgery basically have high blood pressure and high blood lipids. For these patients, the main risk is the sudden increase of blood pressure during the surgery or within 1~2 weeks before and after the surgery because the blow of the surgery stimulates blood pressure, which in turn promotes the occurrence of cardiovascular accidents, i.e. heart attack, brain infarction or cerebral thrombosis.
Although the risk of surgery is higher in this type of patients, it is not absolutely impossible to operate. Patients need to go to the cardiology department to ask the doctor to help control the blood pressure. Moreover, patients with high blood pressure cannot eat or drink before surgery (it is okay to drink a small sip of water while taking antihypertensive medication) to ensure that the blood pressure will not be too high during surgery, and only then can the surgery begin.
Due to the high risk of surgery for patients with hypertension and heart disease, it is recommended that such patients go to a large general hospital, especially one with a strong internal medicine department, for artificial joint replacement. For example, Peking University People’s Hospital has a strong cardiology department or monitoring room, so if there is a danger during the operation, the internist will be able to rescue the patient in time.
5.Artificial knee joint: what is the difference between domestic and imported?
What is the difference between domestic and imported joints? How to choose?
Prof. Guan Zhenpeng: The early domestic joints imitated the imported joints, the material is basically the same, the only difference is in the production process. At the same time, the imported joints may have been updated to the fourth generation, while the domestic joints are still in the third generation, which will affect the degree of refinement of the joints. As for the service life, the domestic joints are a little less than the imported joints. However, imported joints are more expensive than domestic joints, so the choice between the two should be based on one’s financial situation.
I have been doing joint replacement surgery independently since 2002 and have done nearly 4,000 cases since then, both with domestic and imported joints. From what I have observed so far, there is not much difference between using domestic joints and imported joints in 10-15 years, and there may be a significant difference after 15 years, but it is impossible to predict at this time.
Does osteoporosis affect the service life of artificial joints?
Prof. Zhenpeng Guan: This is a rather controversial issue. On the one hand, osteoporosis is commonly referred to as “bad, brittle” bones. After joint replacement surgery, osteoporotic patients have poor grip on the artificial joint, just like a stick in a pile of sand, it will easily fall down. This is why patients with osteoporosis are prone to loosening of the prosthesis, which in turn affects the life of the artificial joint.
However, on the other hand, most knee replacements in China are now fixed with bone cement. Osteoporosis causes the bones to be “fragile” and the bone cement fixes the artificial joint and also glues the “fragile” bones, i.e. the bones and the prosthesis grow together. This reduces the impact of loosening of the artificial joint due to osteoporosis.
Also, osteoporosis is often caused by diseases or medications, such as rheumatoid or hormone use. In addition, joint pain that prevents walking can also cause bone loss. And after the artificial knee replacement, patients are able to walk and exercise, sunshine, so that the bone quality can be improved instead.
6. How do I deal with knee replacements in both legs?
When both legs need knee replacement, should they be replaced together or separately?
Prof. Guan Zhenpeng: In terms of cost and pain, patients who have bilateral replacements together suffer less, only one anesthesia is used, the originally bent leg can be straightened after surgery, and it is easier to exercise after surgery.
However, studies have found that when both knees are replaced at the same time, the incidence of post-operative complications can be 1+1>2 for the elderly, with a higher chance of cardiovascular and cerebrovascular accidents, as well as an increased chance of infection. It is important to know that the surgery for simultaneous replacement of both knees is longer, and the incision exposure is extended, making it difficult to predict what will happen at this time. Therefore, although the patient will suffer twice with separate replacements, the risks of the surgery are significantly reduced and the patient recovers quickly after the surgery, and the lost blood and hematocrit can be restored more quickly.
It is recommended that older patients, especially those with hypertension and heart disease, should have one leg replaced if both knees need to be replaced, and then have the other leg done after 2 to 3 months when they have recovered. It is important to note that when replacing both sides separately, the interval should not be too long, as this can affect the functional exercise of the leg that has not been operated on.
As for young patients, if the economic conditions are slightly worse, the health condition is good, there are no problems such as diabetes and hypertension, and the joint deformity is particularly serious, after the replacement of one side of the joint, the non-operated leg will affect the exercise of the operated leg, which can be replaced at the same time.
7.Knee replacement details of interest to patients
Is general anesthesia or local anesthesia used for knee replacement?
Professor Guan Zhenpeng: Anesthesia for knee arthroplasty depends on the situation. Some patients are afraid to hear the sound of the operation and choose general anesthesia; if they don’t care about that, they can choose local anesthesia.
After general anesthesia, the patient is a little slower to recover and more expensive; local anesthesia is a little cheaper because the patient will be awake when the anesthetic wears off. In the early years of the United States, most hospitals used general anesthesia, but now they have changed. At Peking University People’s Hospital, I prefer to use local anesthesia if only one side of the knee is being replaced, because the entire surgery takes just over an hour and local anesthesia is sufficient and the patient recovers quickly after the surgery.
Is the incision caused by the surgery large?
Prof. Guan Zhenpeng: Generally, the incision is 15-20 centimeters, and it may be smaller for thin patients, and the wound is usually back to a line within 3 months after surgery. However, for patients with keloid, although the incision is also 15-20 cm, the wound will heal into a large and hard scar within 1~3 months after surgery, and the scar will soften slowly after a period of time.
Does the surgery bleed a lot? Do I need blood transfusion?
Prof. Zhenpeng Guan: Nowadays, there are two methods of blood management during surgery. One is to tie a tourniquet at the root of the thigh when doing the surgery, so that there is no bleeding from the incision throughout the surgery. After the surgery, the tourniquet is released and the doctor injects the hemostatic medicine into the joint cavity to stop the bleeding. 100~200ml of blood is drained out after the surgery.
Another way is to operate without a tourniquet. This is because studies have concluded that the use of a tourniquet during surgery may aggravate the formation of a blood clot. If a tourniquet is not used, a blood recovery device can be used to collect the blood coming out of the surgery, filter it through the device, and reinject it into the body. 200 to 300 ml of blood is usually re-recovered during the surgery.
If only one side of the knee is replaced, the intraoperative bleeding can be recovered after washing and filtering, and the final post-operative bleeding is only 100-200 ml, so no blood transfusion is needed at this time. However, if both knees are replaced at the same time, a blood transfusion may be necessary after surgery. There was a patient who had a double knee replacement, and after the operation, the hematocrit dropped to 6-7 grams, he was white and weak, and he was unable to exercise.
How long did the patient need to be hospitalized after the surgery?
Prof. Zhenpeng Guan: Generally, joint replacement takes about 14 days from the time the surgery is done to the time the stitches are removed, and in the past, they waited until the stitches were removed before they were discharged from the hospital, but this is not the case now. For example, the Peking University People’s Hospital will choose several secondary hospitals as rehabilitation hospitals. After the surgery at the Peking University People’s Hospital, patients only need to stay in the hospital for 3-5 days, and after the higher risk time, they can be transferred to the rehabilitation hospital for rehabilitation exercises, and they can go home when the stitches are removed at the rehabilitation hospital and there is no oozing or bleeding from the wound. In other words, the length of stay is still 14 days, just different hospitals. In the United States, most patients return directly to the community for rehabilitation three days after surgery, and patients have specialized rehabilitation staff in the community to provide guidance. However, patients should never return home to change their own medications unless a child in the family is a physician.
8.How are common complications treated after knee replacement?
What are the main post-operative complications?
Prof. Zhenpeng Guan: The incidence of complications after artificial knee replacement is very low, and the most common one is infection. Once an infection occurs, the most common method is to surgically remove the prosthesis, kill the bacteria around it, and reinstall a new joint, which is slightly painful for the patient.
There is now worldwide research on how to prevent infection. In fact, the infection rate after joint replacement used to be very high, with foreign data showing 1% to 2%, but now the statistics for major hospitals in China are about 0 or 5%, which is quite low. However, for many people, this is only a probability, but for each patient, it is “yes” or “no”, i.e., either infection or no infection.
There are many factors that can cause infections, such as diabetes. In addition, postoperative pneumonia can also cause infection if not taken care of. To prevent infection, my experience is to keep some antibiotics at home. After a joint replacement, patients need to take antibiotics promptly if they have a cold, fever, pneumonia, urinary tract infection, etc. It is important to know that if left untreated, the inflammation travels through the bloodstream to the artificial joint and can cause infection.
In addition to infection, a common complication after artificial knee replacement is a blood clot. Usually blood clots occur 2 to 3 weeks after surgery, or 4 to 5 weeks after surgery. After having an artificial knee replacement, the clotting factors in the blood vessels of the patient’s lower extremities increase in viscosity, clotting in the blood vessels, slowing the flow of blood and creating a blood clot. More seriously, the clot can travel down the bloodstream to the heart if it falls, causing a pulmonary embolism, and once a pulmonary embolism occurs, the patient’s life is in danger, and the incidence of this condition is 1 per 1,000 to 2 per 1,000.
In order to prevent thrombosis, after the surgery, we will let the patient move as early as possible, or use plantar vein pumps, elastic stockings and anti-thrombotic drugs. Through various measures, the incidence of blood clots is now very low. However, after the surgery, if the patient’s leg is very swollen, he or she must be seen promptly for ultrasound to check for thrombosis, and if there is any thrombosis, it must be treated promptly.
In addition, other complications, such as neurovascular injury, are mostly caused by improper operation during surgery, but this is very rare. Some patients cannot lift their feet after surgery, mostly because the nerves were temporarily paralyzed during the surgery. After the surgery, some patients’ nerves are still paralyzed, which is only temporary and will improve after a period of time. Swelling and incisional ooze are complications that occur in many surgeries.
9. Knee replacement consultation guide
What is the cost of knee replacement? Is it reimbursable by medical insurance?
Prof. Guan Zhenpeng: Imported joint prostheses generally cost 30,000 to 60,000, while domestic ones cost 1,50,000 to 20,000. Together with other costs such as surgery, the total cost of an imported joint is 50,000 to 70,000, while the cost of a domestic joint is 50,000 to 60,000.
In Beijing, joint prostheses are reimbursed for 9,000 yuan, while other costs, including anesthesia, surgery, and blood transfusions, are reimbursed on a sliding scale. The situation varies from province to province, so you need to ask the health insurance department for details.
What are your clinic hours? How can I get your number for patients who want to have joint replacement surgery?
Prof. Zhenpeng Guan: I am available on Monday mornings and Wednesday afternoons at the Xizhimen Campus of Peking University People’s Hospital.
My specialty is artificial joint replacement, such as artificial knee replacement, artificial hip replacement, and revision surgery of hip and knee replacement. In particular, hip and knee replacement is required due to rheumatoid arthritis with high flexion contracture and ankylosing spondylitis. In addition, we are experienced in doing O-leg, ectropion, and severe deformities. Patients with these needs can register with me or make an appointment through the website to add a number.
What information should patients bring to the doctor’s office to determine if they can have surgery?
Prof. Zhenpeng Guan: If a knee replacement is needed, it is recommended to take a standing x-ray. If the local hospital does not provide standing x-rays, it is recommended to come to our hospital for this. In addition, orthopantomogram, lateral radiograph and patellar axial radiograph of the knee joint are required.
As for the blood tests, they are done to find out if the patient has hypertension, hyperlipidemia, diabetes, etc., and to make an assessment. Therefore, if the test results are abnormal, it is best to bring them with you to your appointment.
How long does it take to schedule a bed for surgery?
Prof. Zhenpeng Guan: It usually takes 2 to 3 weeks, at the earliest it will take about a week, at the slowest it will take less than a month. If the patient has an emergency, it is necessary to contact again specifically.