ARTHRITIS OF THE HIP JOINT

Unfortunately, even the most minor of surgical operations carries some risk of complications occurring. Hip replacement surgery is very successful, and complications are relatively uncommon, considering the complexity of the procedure.

The most common complication is blood clots in the legs. The most serious complication is infection. The most important long-term complication is loosening or wear.

1. Bloodclots in the veins of the legs are the most common complication of hip replacement surgery. As long as the clots remain in the legs they are a relatively minor problem. Occasionally they dislodge and travel through the heart to the lungs (pulmonary embolism). This is potentially serious, since (very rarely) death can result from embolism. The chances of embolism are one out of several hundred. The internist will prescribe Coumadin (a blood thinning drug) to help prevent clots from forming after your surgery. Additionally, compressive calf pumps are used and leg exercises are encouraged to prevent blood clots. Blood clots can occur despite all these precautions. They are usually not dangerous if appropriately treated, but may delay your discharge from the hospital by two to three days.

2. Infection. Pioneer surgeon John Charnley found that the risk of infection after joint replacement was much greater than with most other operations, unless special precautions are taken. Since bacteria can enter the open wound at the time of the surgery in a regular operating room, he invented the laminar flow operating room in which special filters provide clean air, free of most bacteria. In addition, Charnley devised a sterile space suit for the surgeon and his attendants. The suite encloses the entire head and body, and includes a sterile face mask. Antibiotics given to you before, during and after the operation further help to lower the rate of infection.
   
   Dr. Huddleston uses all these precautions and has had four deep infections after hip replacement (and three after knee replacement) in twenty-six years as a joint replacement surgeon. All of these infections were in “immuno-compromised patients”, i.e. patients with inflammatory arthritis who were on steroids or other immuno-suppressing drugs. The risk of deep infection in first-time hip replacement is currently reported as being about 0.5%. Note that superficial wound redness and stitch “abscesses” are common in the first few weeks, resolve quickly on antibiotics, and are not included in these statistics.
   
   

   The risk of infection in the weeks after the operation is increased if you have rheumatoid arthritis or diabetes, if you have been taking cortisone for prolonged periods of time, if the affected joint has had previous infection, or if you have infection anywhere else in your body (teeth, bladder, etc.) at the time of surgery.

   The artificial joint can become infected many years after the operation. The bacteria travel through the blood stream from a source elsewhere in the body, such as from an infected wound, or a gall-bladder infection. Even regular dental work can release bacteria into the blood. Infections of the bladder, teeth, prostate, kidneys, etc. should be cleared up by appropriate treatment well before the day of surgery. Patients who have had joint replacements must take antibiotics by mouth before and after any dental work (see Long-Term Care of Your Hip Replacement) and must have all infections vigorously treated.

3. Loosening of the prosthesis from the bone is the most important long-term problem. How long the bond will last depends on a number of factors.
   1. How well the surgery is done. This is by far the most important factor. Choose a surgeon who has had a great deal of experience with hip replacement, and preferably one who restricts his practice to joint replacement surgery.
   2. The quality of your bones. The harder your bones are, the better the bond will be, and the longer the replacement will last. Osteoporosis is a factor of age, as well as the type of arthritis you have. People with rheumatoid arthritis have especially soft bones.
   3. How active you are. Excessive force on the implant can cause the bond to loosen. If you stayed in bed for the rest of your life the implant will probably never come loose! The key thing is to use common sense. (See Allowable Activities After Hip Replacement).
   4. Your weight. You should also keep your weight down because every pound you gain adds three pounds to the force on the hip.
   5. Whether or not the implant is cemented. At present it is believed that uncemented implants will last longer than cemented ones. We are not certain that this will be the case, even though the results so far are extremely good and promising (see Total Hip Replacement Surgery) with cementless implants.
   6. The design of the implant. Small abrasion particles from the implant may play a role in implant loosening. Plastic surfaces shed more particles than metal or ceramic ones.

4. Wear of the Plastic Polyethylene Socket starts from the day of surgery. The plastic socket is the weakest link in the implant. The rate of plastic wear against a metal ball is about 0.1 millimeters per year, but is more rapid in very active patients. “Cross-linked” polyethylene promises a wear rate about half that of regular poly. Plastic wear against a ceramic ball is much less in the lab, but this has not yet been shown to be true in the human body. Metal-on-metal bearings will never wear out. Nor will ceramic-on-ceramic implants, but there is a 1/20,000 risk of fracture of the ceramic ball. Dr. Huddleston uses and recommends metal on metal implants, or ceramic on ceramic implants for those patients who want them, and have a life expectancy of more than fifteen years. In all others he uses cross-linked polyethylene. (“Marathon” Polyethylene from Johnson & Johnson). Paradoxically, Dr. Huddleston may use a large-head metal-on metal implant in older patients with loose ligaments for the stability it confers and not for its wear properties.
   
   
5. Dislocation of the hip replacement occurs in a small percentage of patients regardless of how good your surgeon is (some surgeons report as high as 4%). With the Anterior Approach or the Gluteal Split techniques of hip replacement, or the use of a large femoral head the risk of dislocation is greatly reduced, although it can still occur. Dislocation means that the metal ball slips out of the plastic socket. In the first six weeks after the surgery, the ball is only held in the socket by muscle tension. During this time, before scar tissue forms around the ball, and before muscle strength returns, the hip is more likely to dislocate.

   Therefore, to prevent dislocation, certain positions have to be avoided for the first six weeks (see Restrictions to Prevent Dislocations).

   The physical therapist will teach you what positions to avoid, and how to safely use your hip replacement during this early phase of your recovery. If the hip does dislocate, it is usually a simple matter for the physician to pull on the extremity and “pop” the hip back into place (see What To Do If Your Hip Dislocates). Revision hip replacements, replacements in people who are grossly overweight and replacements in people with poor muscles are more likely to dislocate. Occasionally patients develop repetitive dislocations, requiring a brace to be worn for several months to prevent further dislocation. Sometimes further corrective surgery is needed to solve the problem.

6. Extra bone formation (ectopic bone) around the artificial hip develops less than 1% of the time. It causes the hip to be stiffer than desired. This is more likely to occur in younger males with severe osteoarthritis. Small amounts of ectopic bone appear frequently around hip replacements but do not cause a problem. Very large amounts causing severe stiffness is rare. It can be treated by surgical removal of the bone once it is “mature.” Radiation therapy may be recommended by Dr. Huddleston to try and prevent ectopic bone formation if he believes a particular patient is likely to develop it. Such radiation treatment is administered during the first 2 or 3 days after surgery, or on the day before surgery. If you need radiation, the risks will be discussed with you by the radiotherapy doctor. The risks are negligible.

7. Fracture of the femur can occur during hip replacement. This can be a small crack or a major fracture. It is more common during revision hip surgery, but can occur with first time hip replacement. Occasionally the femur may be accidentally perforated during first time or revision hip surgery. It can also fracture later from any trauma, such as falling down stairs. If your femur is accidentally cracked during surgery, you may have to remain on crutches for up to 3 months to allow healing to occur. You may have to remain in the hospital with traction for several weeks. Complete fracture may require separate surgery for fixation. Small cracks may need to be treated with “circlage” wires.

8. Residual pain and stiffness can occur. In virtually all cases hip replacement will make a significant improvement in your pain and mobility. In most cases, you will have no pain at all, and the hip will feel “normal.” The completeness of the pain relief, and the degree of mobility is partially determined by your hip problem before surgery. Rarely, patients have pain after surgery which cannot be explained. About 5% of patients with an un-cemented hip replacement develop mid-thigh-pain  (also called “end-of-stem pain). The cause is unknown but is thought to be related to a mismatch between the rigidity of the implant, versus the elasticity of the bone. Some patients with un-cemented hip replacements develop mid thigh pain. The pain is usually mild, and almost always resolves after 18 to 24 months. It has been found that the larger the diameter if the implant installed the more likely “thigh pain” will develop. For this reason, Dr. Huddleston almost never installs an un-cemented femur implant larger than 17 millimeters in diameter. (See Problems You May Encounter at Home).

9. The length of the leg may be changed by the surgery. Getting leg lengths exactly right can be very difficult. Some leg length difference may be unavoidable. Sometimes the leg will be deliberately lengthened in order to stabilize the hip or to improve muscle function. Shoe lifts may be necessary if the difference is more than a quarter of an inch. When the leg is more than an inch short to begin with, it may be impossible to equalize the legs for fear of damaging the nerves to the legs. In the first weeks after surgery, most patients complain that the operated leg feels “too long” even when the legs are perfectly equal in length. This is an artificial sensation which will resolve itself after a few months (see Problems You May Encounter at Home). Dr. Huddleston has an accurate method for getting the leg lengths correct.

10. Injury to the arteries or nerves of the leg is an exceedingly rare but possible complication. The major arteries of the leg lie close to the front of the hip joint. The damaged vessel can usually be repaired by a vascular surgeon if recognized in time. If the nerves to the leg are injured, they usually recover; but it may take 6 months or more. Occasionally, they don’t recover at all. Most patients have some numbness around their wounds which may be permanent.

11. Bleeding complications.
    1. Sometimes bleeding can occur into the wound in the days after surgery (“hematoma formation”) as a result of the use of blood thinners. It may distend the hip and cause dislocation. If it is excessive, it may require re-opening the wound under anesthesia to let the blood out.
    2. Occasionally the blood thinners may cause bleeding into the urine (or elsewhere), but this is usually temporary, and not of serious consequence.

12. Anesthetic complications can occur, and very rarely even death can occur from the anesthesia. Your anesthesiologist will see you before surgery and explain the risks involved.

13. Allergy to the metal parts. About 15% of the population has skin sensitivity to some metals. All metal implants release some metal ions into the body. However, reports of proven allergies to metal implants are surprisingly rare. You should notify Dr. Huddleston if you believe you have a metal allergy. People who know they have metal allergies should be tested with extracts of the various metal components of the implant prior to surgery. The tests are not reliable, so they are only performed if a metal allergy is suspected. Allergy to the plastic parts has never been reported. Small particles of plastic or metal from the implant may cause a “foreign body” reaction in the bone, but this is not a true allergy. Some patients with metal implants have had temporary, mild skin rashes, while some have had severe rashes that resolved only with removal of the implant. If you are known to be sensitive to nickel, chromium or cobalt you should probably have a titanium implant, even though there have been reports of allergy to titanium as well.
    
    

    ALVAL. Patients frequently enquire if the body can “reject” the hip implant. Until recently the answer has been an emphatic “no”. The body does react adversely to the microscopic particles that abrade off a plastic socket, but the reaction is not rejection but a “ histiocytic response” to foreign particles, which can cause the implant to loosen.

    Since the advent of large-head, metal on metal hip replacements, a new ominous entity has been identified which has been given the clumsy name of ALVAL  (Aseptic Lymphocytic Vasculitis Associated Lesions). A Delayed Type of metal Hypersensitivity (DTH) is induced due to high concentrations of Cobalt and Chromium ions that build up around the joint. This leads to painful inflammation in the joint (“Lymphocytic Vasculitis”). Sometimes necrotic inflammation tissue combined with proteins builds up around the hip and into the pelvis, forming so-called “pseudo-tumors” which can be seen on CT, ultrasound or MRI scans, and can be a perplexing diagnosis for the un-initiated. ALVAL is rare. It is seen most frequently in women.
    
    Symptoms include unexplained pain or discomfort in the hip, swelling of the leg, a noticeable lump near the hip, symptoms from pressure on a nerve, and occasionally a rash.
    
    Sometimes the implant comes loose in association with ALVAL. It is not known if the loosening is caused by ALVAL or if a loose implant is more likely to produce high concentrations of metal ions, which then cause ALVAL.

    If ALVAL is suspected, testing for metal sensitivity may help in the diagnosis. Skin patch testing is considered to be useless. A blood test, Lymphocyte Transformation Testing (LTT) is more reliable. Measuring the blood and urine levels of chromium and cobalt can help in the diagnosis of unexplained hip pain. Joshua Jacobs, MD at Rush University is the recognized expert on the diagnosis ALVAL.

    The treatment of ALVAL includes removing the metal bearing parts of the artificial joint (whether loose or not), and replacing the ball and socket with a ceramic on plastic bearing surface. Any “pseudo-tumors” can be “scraped out” at the same time.

    Note that the term “pseudo-tumor” does not in any way imply that this condition is cancerous. Indeed, so far, after more than twenty-five years of metal-on-metal experience in Europe, there is no evidence that metal ions from a hip replacement might cause cancer.

14. Complications From Blood Transfusions. The risks of getting AIDS from banked blood is believed to be about 1 in 2,000,000. The risk of Hepatitis B is estimated to be approximately 1 in 550 units, and Hepatitis C is 1 in 100. The risk of disease transmission from directed blood (see Blood Transfusion for Total Joint Replacement) may be the same a the risk from ordinary banked blood. The risk of an allergic reaction (hives) is 1 in 500. You can have an allergic reaction to donor blood even though it has been properly cross matched. The risk of a Hemolytic Transfusion Reaction is 1 in 10,000. The risk of a Fatal Hemolytic Transfusion Reaction is 1 in 100,000.

    All blood intended for transfusion (including your own) is screened by the blood bank for Hepatitis B virus, Hepatitis C virus, syphilis, Human T Cell Leukemia virus, and the AIDS virus. If cadaver bone is used as part of revision hip replacement, there is some risk of transmitting disease, just as with blood transfusion. The bone is screened for 6 months before being used.

15. Fat Embolism. Fat from the bone marrow can get into the circulation and cause lung or neurological symptoms. This is a very rare complication. In very rare cases it can be fatal.

16. Other minor complications can rarely occur, such as tape allergies, allergies to medications, skin rashes and so on. You should keep in mind that the chances of any significant complication that permanently affects the overall result and your satisfaction with the joint replacement are very small. Whatever treatable problems might occur along the way, you have about a 98% chance that, in the end, you will be more than satisfied with the end result of your operation.