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The business of medicine, and especially surgery, seems to have a language all of its own some of the time. It's easy to forget what the medical staff is talking about, even if you've listened carefully to their explanations. So we have included a guide to some of the common words you'll hear regarding your treatment. Just click on a letter below to look up a word.
If you have a suggestion for an addition to this glossary, let us know via e-mail.
A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
ACL: Refers to one of the knee ligaments, called the anterior cruciate ligament. Click here to learn more.
Acetabulum: The cup-shaped cavity in the pelvis into which the ball-shaped head of the femur fits. The hip joint is a ball-and-socket joint; the acetabulum is the socket. During a hip replacement procedure, the worn out bone and cartilage in the acetabulum is removed, the socket reshaped, and a properly-sized prosthetic socket inserted.
Allograft: A type of graft tissue, whether bone or ligament/tendon, that is taken from a deceased person who donated their tissue and implanted in another patient who has a tissue deficiency. Allergic responses to foreign tissue are prevented by processing of tissue so that the proteins are removed. Thus, for example, bone allografts do not have proteins, just the calcium and supporting structure that can be very helpful in rebuilding bone loss in complex hip and knee replacements.
Alumina: This is a type of ceramic material used in orthopaedic (usually total hip) bearings. The wear rate of alumina ceramic bearings is better than anything else in total hip replacements. When people refer to ceramics in joint replacement surgery, they usually mean alumina, since this is the most common type of ceramic now used in hip replacement surgery. It is not used in knee replacements yet. While there is a theoretical risk of an alumina bearing breaking in the body, this risk is so small with modern biomaterials that it is essentially a theoretical consideration.
Analgesics: This term refers to pain killing or reducing medications used by doctors. The analgesic class of drugs includes common names like aspirin and Tylenol, as well as narcotic pain relievers like morphine, Demerol, and others.
Anterior approach: The “anterior approach” is a term used by surgeons who do hip replacement surgery. It refers to the exact route the surgeon must take to reach the hip joint. In the United States, when surgeons say “anterior approach” they commonly refer to the lateral approach. See “lateral approach” in this glossary for more details.
Arthroplasty: Surgical procedure to alter a joint, relieve pain and restore range of motion by realigning, reconstructing or replacing a joint. May also refer to partial or complete excision of a diseased joint. Typically, when surgeons refer to a total hip or knee "arthroplasty," they mean a total hip or knee replacement procedure.
Arthroscopy: Minimally-invasive diagnostic and treatment procedure using a small, lighted, optic tube which is inserted into the joint through a small incision. Images of the inside of the joint are projected onto a screen. Small instruments inserted through the incision in the skin are used to perform the surgery. Arthroscopy minimizes surgical trauma with essentially no blood loss. Arthroscopic procedures are most commonly performed in the knee and shoulder joints.
Autograft: A type of graft tissue taken from the same patient, but from another location. Typically, bone is removed from the pelvis and put in complex fractures, or other operations to promote healing. In hip and knee replacement surgery, we almost never use these kinds of grafts since the tissue required is too much. Most grafts in joint replacement surgery are of the “allograft” type.
Avascular necrosis: Loss of bone caused by insufficient blood supply. Loss of blood supply can occur for many reasons such as steroid or heavy alcohol use and exposure to certain chemicals. In many cases, the cause of avascular necrosis will not be known. In the hip joint, it leads to progressive collapse of the femoral head (the ball of the hip joint), and secondary arthritic changes. in the knee, avascular necrosis is less common.
Bursa: Fluid-filled sac located between a bone and a tendon or muscle. Bursa sacs are normal and allow smooth gliding of the tendons and ligaments during normal movement of the joints. In disease processes such as arthritis, the bursa sacs located close to the joint may become inflamed and painful.
Cartilage: Smooth material that covers bone ends of a joint to cushion the bone and allow the joint to move easily without pain. Cartilage is the body's natural bearing surface, with very low friction, and a soft, pliable, wet surface. Once destroyed in the adult joint, cartilage cannot regenerate itself. Surgical procedures to restore cartilage are successful in young patients with isolated, small cartilage injuries. With extensive destruction of cartilage in the hip or knee joints, replacement of the joint with an artificial surface is typically the only choice available.
Corticosteroids: Potent anti-inflammatory hormones that are made naturally in the body or synthetically for use as drugs. Most commonly prescribed drug of this type is Prednisone. One of the side-effects of Prednisone therapy is avascular necrosis.
Coumadin™: Anticoagulant used to prevent the formation of blood clots. The generic name for Coumadin is Warfarin. This drug thins the blood and decreases the risk of blood clots after surgery.
Cruciate Ligaments: There are two cruciate ligaments in the knee (so-called since they cross each other in the middle of the knee). These ligaments are about the thickness of the little finger. They are stout, and keep the knee joint from moving too far forward or backward; in other words, they keep the tibia bone from moving out from under the femur bone when the knee goes through a range of motion.
During most total knee replacements, both cruciate ligaments are surgically removed. The ligaments are usually worn away and frayed from arthritis in most cases anyway, and the new knee components have mechanisms that compensate for the lack of these ligaments.
There is one surgical technique variation in which the PCL is spared, and it serves to stabilize the knee, instead of mechanical components that could do the same thing. This technique is a variation of surgery; in general there is no advantage to preserving this ligament versus substituting for it during surgery. It all depends on the preference of the surgeon; the outcomes for the patient are identical.
Both the ACL and PCL are preserved entirely in partial (unicompartmental) knee replacements, and in unispacer surgery.
Deep Venous Thrombosis (DVT): Also know as a blood clot. After hip or knee surgery, or any surgical procedure, the risk of blood clots increases. Obesity, diabetes, certain genetic profiles, inactivity, trauma, burns and orthopaedic procedures increase your risks. If you have had a blood clot in the past, you have an increased risk of a clot after a surgical procedure in the future. Compression boots, early exercise and mobility of the patient, minimizing the surgical trauma, and anticoagulant drugs reduce 5he risk of clots. Most clots can be "silent" and occur without any obvious signs. The clot can break off and go to the lungs, causing breathing difficulties, or even death. This occurs rarely. New and unexpected swelling of the leg, calf pain, cough, chest pain, or difficulty breathing after surgery can be indicative of a blood clot. If there is any suspicion of a clot, you will get a deep venous ultrasound, which is a non-invasive test designed to detect clots. If a deep clot is found in the leg, the anticoagulant drug must be continued for several months. By then, the thinking is that the clot is re-absorbed by the body, and there is no danger of it breaking off and going to the lungs. While the body is eliminating the clot, the anticoagulant drug ensures that the clot does not grow further.
Diamond-like ceramic: Diamond coatings on metal substrates, and synthetic diamond bearing surfaces are being investigated for hip and knee replacements. These materials are ultra-tough, and offer very low wear rates, thereby offering the possibility of longer lasting hip and knee replacements. These technologies are under development and will be available in the United States in the near future.
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Extension: Movement in which the bones on either side of the joint are taken further apart, increasing the angle of the bones. Extension is the opposite of flexion. When you straighten your knee, you are extending the knee joint. In the hip, extension refers to the ability to swing the thigh back, such as when you take a step back. Your ability to stand and walk depends on being able to straighten the knee out fully after surgery. With progressive arthritic change in the knee joint, people lose the ability to fully straighten the knee. During surgery, the bone is prepared in such a way that the knee can be straightened while the you are under anesthesia. After years of keeping the knee slightly bent, and the resulting muscle contractures, you may require therapy and motivation after knee replacement. Knee replacement is generally easier before stiffness results in lost motion. Even though the surgeon may be able to restore motion during surgery, the shortened, weakened muscles must be re-educated through therapy. The movement that you have before going into surgery often predicts how much movement you will achieve after knee replacement.
Femoral head: The “femoral head” refers to the ball part of the hip joint. The hip is a ball-and-socket joint. The femoral head sits at the top end of the femur, which is the thigh bone, and the longest bone in the body. The head is covered with a smooth layer of cartilage. During walking, this head, or ball moves back and forth inside the socket.
Femur: Longest and largest bone in the human body, extends from the hip to the knee. The femur has the knee and hip joints at either end.
Flexion: Movement in which the bones on either side of the joint are brought closer together, decreasing the angle of the bones. Flexion is the opposite of extension.
Gait: Pattern of how a person walks. With hip and knee arthritis, the gait pattern is altered, leading to a limp. Typically, the patient will subconsciously put less weight on the arthritic joint, leading to an abnormal gait.
H
Hip Resurfacing: An alternative to total hip replacement, this operation is similar in that the hip joint is replaced with a prosthesis. But, instead of a femoral stem being implanted in the thigh bone, the arthritic ball is preserved and capped with metal. This operation has been around for many decades and is now enjoying a resurgence because of recent improvements that promise better results than in the past. Be sure to read more about hip resurfacing here.
Joint: The point of connection between two bones or elements of a skeleton. The knee is the joint of the femur and the tibia. It is overlain by the sesamoid bone, the patella or the kneecap, which guides the patellar tendon in a smooth path over the bony projections of the knee. The hip is a joint between the head of the femur and the acetabulum. The head of the femur or ball of the hip joint moves within the cup-like socket acetabulum of the pelvic bone.
Joints are covered on the inside by smooth cartilage and they typically contain a small amount of natural lubricating fluid. Diseased and worn joints may benefit from an augmentation of this fluid such as cortisone injections to reduce the inflammation in the joint.
Also see ligaments.
Lateral approach: The “lateral approach” is a term used by surgeons who do hip replacement surgery. It refers to the exact anatomic route the surgeon must take to reach the hip joint. The patient is placed on the side. Then, the skin is cut over the hip area. Next, a thick layer of tissue called the fascia lata is cut. Next, a heavy muscle which helps one walk is split, and the hip joint becomes visible. Once the joint is dislocated, the femoral head is cut off, and the artificial hip is inserted. A variant of this procedure is the minimally invasive hip replacement, which is essentially the same operation, but performed with a smaller incision.
Legg-Calve'-Perthes disease (or Perthes disease for short): A hip disorder that develops in childhood. The theory is that during childhood, for some unknown reason, the blood supply to the hip ball (femoral head) is lost. As a result, a part or all of the bone involved temporarily dies. The socket part of the hip (acetabulum) is fine, but the head intermittently loses its blood supply and goes through cycles of healing and injury. As a result, the head becomes deformed.
Instead of the usual round shape of the hip ball, a patient with Perthes disease has a flattened and deformed hip ball on x-rays. Because of the incongruence between the flat head and the round socket, degeneration and arthritis can set in very quickly. These patients are typically referred for joint replacement surgery and the challenge is how to defer surgery as long as possible, since many patients with Perthes disease will develop hip arthritis early on in their lives. After hip replacement of course, the pain is relieved, and function and movement are restored.
Ligaments: Joints are held together by ligaments. With advanced arthritis, these ligaments can become torn and stretched. During a hip or knee replacement procedure, the supporting ligaments are usually preserved, and "balanced" by the surgeon to get as much mobility and stability back as possible. If necessary, special implants can be used that substitute for the damaged ligaments and provide stability to the joint.
Lovenox®: Anticoagulant used to prevent the formation of blood clots. This is a substitute for Coumadin. The disadvantage of using Lovenox over Coumadin is higher cost, and the need for the daily injections that the patient must self-administer. The advantage is that monitoring of the drug is not necessary. Click here for more.
Musculoskeletal system: The complex system involving the body's muscles and skeleton, and including the joints, ligaments, tendons and nerves. The hip and knee joints are part of the musculoskeletal system. Certain diseases such as ankylosing spondylitis, rheumatoid arthritis, lupus, fibromyalgia, psoriasis, and osteoarthritis have profound effects of the musculoskeletal system. Ultimately, these diseases may lead to the destruction of major joints such as the hip and knee joints, necessitating reconstructive surgery on these joints.
NSAID: Abbreviation for the class of nonsteroidal anti-inflammatory drugs. NSAIDs do not contain corticosteroids and are used to reduce pain and inflammation. Aspirin and ibuprofen are the two commonly used NSAIDs. These drugs are the first line treatment for arthritic pain. They reduce pain by interrupting the cycle of inflammation that causes pain in diseased joints. NSAIDs do not alter the course of degenerative arthritis, and none of them restore cartilage. Celebrex, Vioxx and Bextra are the newest in this class of drugs and have the advantage of reduced gastrointestinal side-effects. Previous NSAIDs such as Naproxen, Relafen, Feldene and others may be equally effective for some patients. The pain and stiffness of early osteoarthritis will respond very remarkably to Tylenol or one of the NSAID drugs. It is distinctly unwise to embark on any reconstructive surgery of an arthritic hip or knee without trying an NSAID type drug first, because the majority of patients can achieve pain relief for many years and avoid surgery entirely.
Osteoarthritis: Also known as degenerative joint disease. Cartilage that cushions the ends of bones breaks down causing bones to rub together. The patient may experience pain and loss of movement. The patient will experience pain and stiffness. With physical breakdown of the joint space, the shape of the joint surfaces is altered, and the friction inside the joint increases. The diseased joint will feel hot and swollen. Symptoms will respond to Tylenol, appropriate exercise, hydration and NSAIDs. If X-rays show destruction of the joint, and if all other means of controlling pain have failed, and if the joint begins to lose mobility, replacement of the osteoarthritic joint with artificial implants should be considered as a last, salvage resort. Additional information:
Osteotomy: Refers to realignment of the arthritic joint. This is a procedure that is not as common as hip or knee replacement surgery. It is applicable mainly to the young, healthy patient who has a good understanding of the underlying problem. As an example, a relatively young patient with knee arthritis localized to the inside of the knee joint and a leg that is bow-legged for some reason, may be a candidate for an osteotomy of the tibia. The surgeon will cut the tibia bone close to the joint, and re-align the leg, so that the patient's weight and load-bearing are shifted away from the painful part of the knee.
An osteotomy preserves the patient's own joint, reduces pain and improves function for at least 10 or more years. There are very specific indications and contra-indications for osteotomy surgery. In older patients with diffuse and widespread osteoarthritis, joint replacement is more successful and predictable. In our practice, if indicated, the osteotomy is always preferable to replacing the joint.
Partial Knee Replacement: Same thing as “Unicompartmental Knee Replacement.”
Perthes Disease: Same as Legg-Calve'-Perthes disease.
PCL: Refers to one of the knee ligaments, called the posterior cruciate ligament. Click here to learn more.
Primary Care Physician: General practitioner who provides preventive care, identifies and treats common medical conditions, and makes referrals to medical specialists when necessary. Many insurance companies require patients to have a primary care physician refer them to an orthopaedic surgeon. Check with your company for details.While we may instinctively seek a specialist for our ailments in the U.S., the value of a good primary care physician cannot be overemphasized. A primary care doctor can diagnose your problem, get appropriate X-rays, and initiate therapy, pain management, and lifestyle alterations that can keep you going and help you avoid surgery. The primary care doctor has the big picture in mind. In contrast, a specialist, such as an orthopaedic surgeon, particularly one who is focused on reconstruction of the hip and knee joints, has a very constricted perspective. It is worthwhile for you to learn about the values of a good primary care doctor, and how such doctors work with specialists, so that you can use both professionals to your maximum benefit.
Prosthesis: An artificial body part replacement. For hip and knee replacement procedures, the prosthesis refers to the set of artificial components that will be used to replace the arthritic joint.
Range of motion (ROM): Measurement of the extent to which a joint can go through its normal spectrum of movements. In addition to flexion and extension, hip and knee joints also rotate internally and externally. The combination of flexion, extension, internal rotation, and external rotation determine the range of motion of the hip and knee joints. The hip can also be kicked away from the body in a lateral movement called abduction, or it can be swung in toward the opposite leg laterally in a movement called adduction. These movements are not present in the knee, since the knee has to be stable against side-to-side movement during walking. After surgery, the physical therapist and surgeon will often measure your progress by comparing successive range of motion (ROM) measurements.
Rheumatoid arthritis: A chronic inflammatory disease that causes joint pain, stiffness and swelling. A systemic problem, the disease affects the entire body, including the musculoskeletal system. It can lead to severe destruction of the hip and knee joints, requiring joint replacement surgery.
Silicon Nitride ceramic: A promising type of ceramic material made by a company called Amedica. The toughness and strength of this ceramic is superior to the other ceramic materials available to orthopaedic surgeons today. The wear properties of this new type of ceramic are excellent. Hip bearings made from silicon nitride will be available in the United States in the near future.
Soft tissue: Ligaments, tendons and muscles in the musculoskeletal system. These are critical components of your major joints. but you cannot see them on the x-rays, which show only the bones. The condition of your soft tissues will have a major impact on your recovery and ultimate result from joint replacement surgery. A program of regular, low-impact exercise is the best option to keep the soft tissues in good condition.
Sprain: A partial or complete tear of a ligament.
Strain: A partial or complete tear of a muscle or tendon.
Synovitis: Inflammation of the synovial membrane, the tissue that lines and protects the joint. Synovitis occurs almost inevitably in arthritic hip and knee joints and contributes to swelling and stiffness that goes along with arthritis.
Synovial fluid: A clear, sticky fluid that is released by the synovial membrane and acts as a lubricant for joints and tendons. This is the equivalent of the body's natural "grease." It is recycled by the body, just like an oil change in a car. Progressive arthritis and wear of the hip and knee ultimately overwhelm the body's capacity to provide a smooth gliding surface for the joints.
Synovium: The biological lining of the major joints in the human body, such as the hip and the knee. The lining produces synovial fluid.
Tendon: The tough cords of tissue that connect muscles to bones. Tendons are the motors that drive the joint in one direction or another. Just above and below your kneecap is a tough, rope-like structure that consists of a tendon. This tendon, called the quadriceps tendon, is what produces the ability to straighten the knee from a bent position. If this tendon were completely torn, the knee would dangle, and you would not be able to straighten it out, not matter how hard your muscles tried. It would be like breaking the drive shaft of a car. You can rev the engine all you want, but the wheels would not spin. Tendons take the pull of the muscles, and convert it to useful movement of the joints.
Tendonitis: An inflammation in a tendon or the tendon covering commonly treated by primary care physicians. Tendonitis typically responds quickly to NSAID drugs, rest and appropriate rehabilitation.
Tibia: Shin bone or larger bone of the lower
leg. If you run your hand down the front of the leg, from the knee to the front
of the ankle, the hard bony surface is the front of the tibia bone.
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U
Unicompartmental Knee Replacement: This refers to a partial knee replacement, which resurfaces either the inside or outside of the knee. For an x-ray showing a unicompartmental knee (front to back view) click here. For a side-view picture of the typical parts used in a unicompartmental knee, click here. Usually, the surgery trauma is less, and recovery is faster with a unicompartmental knee, also known as a partial knee, since only the arthritic part of the knee is replaced. The topic of partial replacements is covered in greater detail elsewhere on this web site, to go there, please click here.
Unispacer Implant: This is similar to inserting a shim into the arthritic, narrowed joint. Most knees develop arthritis on the inside, resulting in bow-legs. The unispacer is a device that is placed like a shim, separating the bones. It is not fixed to bone. No bone is removed to accommodate it. The metal glides against the bone, and in selected cases, it can give lasting relief. For a picture of a unispacer, click here.
For a front-to-back view of a knee with a unispacer device on your left side of the x-ray and a partial knee on your right side, please click here.
The downside to the unispacer is that recovery is longer. While the patient is mobile very quickly, and the surgery involves minimal trauma and no removal of bone, the pain lingers on, and takes a long time (as in six months or so) to slowly get better. In comparison, the pain relief with total knee replacements and unicompartmental knee replacements is dramatic and almost immediate. The other downside to a unispacer device is that it is indicated very rarely; most patients are simply not candidates for it.
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X
Xenograft: This type of tissue is taken from an animal (i.e., a different species than humans) and processed before implanted in the body. An example is heart valves from pigs that are sometimes used to repair or replace defective heart valves in humans. In hip and knee replacement surgery, we typically do not use xenograft tissue. Most large bone, tendon, or ligament defects in joint replacement surgery are repaired by allograft tissue.
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Z
Zirconia: A type of ceramic material that has been used in the past for both hip and knee prosthesis bearings. This material is stronger than alumina ceramic (which is the more common ceramic used today in artificial joint replacements), but zirconia can behave very erratically in the body and is very sensitive to even small changes in manufacturing variables. Accordingly, this material is no longer available for hip and knee bearing in the United States.
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