Friday, May 11, 2012

The Four Most Common Complications Which Lead to Greater Risk of Unsuccessful Revision

Artificial hip replacements have become increasingly common, yet as people begin to live longer, it is inevitable that these artificial joints will fail, wear out, or cause health complications. Should any of these issues arise a hip revision surgery will become necessary to replace the failing joint. In some instances the metal-on-metal hip implants have led to tiny metal shavings being released into the body, and in severe cases cobalt poisoning can occur. The side effects of high levels of cobalt in the bloodstream are many, from relatively minor to as severe as blindness, deafness, cardiac problems and convulsions.

Sometimes the artificial joint can become infected, leaving the patient stiff and in considerable pain. While antibiotics may be prescribed, infections will often lead to revision surgery. Other times the artificial joint can simply lose its attachment to the bone, requiring a revision. Bone scans are normally taken to allow the surgeon to determine the specific problem with the implant; the patient is injected with a weakened radioactive chemical, then a picture is taken of the bone around the artificial joint. If the joint has loosened or there is infection present, it will be clear from the photo. There are four major issues which can lead to a greater risk of the patient having an unsuccessful hip replacement surgery.

Pseudo-Tumor

The term pseudo-tumor, in the context of hip replacements, is generally used to describe a large, solid semi-liquid mass gathered around the implant which mimics an infection or a neoplasia—an abnormal mass of tissue—in the absence of either of these. The incidence of pseudo-tumors after patients receive a metal-on-metal hip implant has been reported to be between 0.1 and 3% at follow-up periods up to ten years. Those who have had a metal-on-polyethylene implant could be at an even higher risk of developing a pseudo-tumor—as high as 5.8%. These pseudo-tumors can grow rapidly in size and accompany extensive bone loss.

Discomfort and pain generally accompany pseudo-tumors and there can be bony erosions clearly visible. Pseudo-tumors in relation to hip replacement surgeries have been reported for at least three decades. Researchers are as yet unclear regarding the cause of these pseudo-tumors in those who have undergone hip replacement surgery. Many times there is a “latent” period of anywhere from 2-15 years following the initial surgery before this foreign body reaction becomes apparent. Unfortunately, those who have experienced pseudo-tumors, while requiring a revision surgery, are less likely to experience a successful revision.

Overall, relatively poor outcomes were reported in pseudo-tumor revisions with a high incidence of recurrent dislocations, palsy of the nerves and femoral artery stenosis. Hip function in those who have undergone pseudo-tumor revision surgery was largely worse than prior to the original surgery. There is also a high incidence of re-revisions in patients who undergo revision due to a pseudo-tumor. Of course the ultimate outcome is dependent upon a variety of factors, including the degree of destruction at the time of revision.

Crack in the Acetabulum

Some studies have indicated that the cross-linked polyethylene acetabulum hip joint bearings can reduce wear rates significantly over conventional polyethylene however the highly cross-linked polyethylene is more likely to crack which will lead to a revision surgery. The top of a patient’s femur fits snugly into the acetabulum, rotating when movement occurs. The hip implant seeks to mimic the natural construction of the hip joint, including the way the femur and acetabulum fit together. A hip implant is affixed to the rest of the skeleton through a process in which the acetabulum is shaved down to accommodate a man-made socket. When the femur and acetabulum do not fit together as they should, too much friction occurs which can lead to pain for the recipient and eventual cracks in the acetabulum.

While the obvious solution in the case of a cracked acetabulum is to remove the implant and replace it, there is a requirement for healthy living bone to ensure a hip implant succeeds. In many cases the hip bone hasn’t had sufficient time to recover from the initial surgery before a crack in the acetabulum occurs. When revision surgery is indicated in as few as two or three years, it is unlikely the hip bones have completely healed and recovered from the initial surgery making it much more likely the body will reject the new hip implant. Each and every hip implant causes subsequent bone trauma, increasing the odds that the next implant will be rejected.

Joint Fluid Washout and Total Dislocation

Patients who have received a hip implant device may undergo treatments known as joint fluid washout in response to an early infection which occurs in the weeks following surgery. Some surgeons believe this technique is beneficial only in the first 3 weeks while others believe it can be helpful up to 8 weeks. This can be in the form of a joint washout with normal saline or a joint washout with normal saline and an added steroid injection. While both treatments resulted in a reduction of pain and increased mobility, patients undergoing only the joint washout had less improvement than those who had the joint washout with a steroid injection. Joint washout can, however, lead to greater risk of unsuccessful revision surgery in the event it becomes necessary.

Hip dislocation can occur when the ball slips out of the socket and can be excruciatingly painful. While in some instances the dislocation can be put back in an emergency room, in other cases it will require surgery, especially when it is determined there is no muscle or tissue blocking it. If the patient experiences one or two dislocations, the tissues may naturally tighten up as time passes and no further intervention is necessary. Should the patient continue to experience dislocations a revision surgery could be indicated and the surgeon may opt for a more constrained hip replacement which does not dislocate as easily. Dislocation occurs in approximately 1% of all hip replacements, usually within the first six weeks. The patient who experiences multiple hip dislocations and requires revision surgery faces the same issue as any patient undergoing a second hip surgery which is soon after the first—the body has not had sufficient time to heal from the first surgery and may reject the new implant.

Abductor Muscle Instability

Instability occurs when the metal ball slips out of the plastic socket, or the metal ball slips out of the metal socket, depending on which type of implant the patient receives. This is an extremely painful occurrence and if it happens multiple times can be reason to consider a revision surgery. Instability is considered to be one of the most common complications following hip replacement surgery, and can occur early on, or can manifest years later. Late instability—five years or more after the surgery—generally requires intervention in the form of an operation or revision surgery. Instability may occur from a mis-positioning of the artificial components, a trauma to the area, deterioration in the patient’s surrounding muscle mass, or wear on a polyethylene component. Instability occurs in as many as 2-5% of all those patients undergoing hip replacement surgery, and a full third of these dislocations occur past the five year mark. The outcome of a hip revision surgery can be compromised by instability complications, particularly if the instability occurred early on post-op. Once more, revision surgery which occurs soon after the initial hip replacement is much less likely to be successful simply because the surrounding muscle and tissue has not yet had time to properly heal.

All in all, hip revision surgeries tend to be much more challenging than the original hip replacement surgery. Both the results of the surgery as well as the durability of the revised hip replacement tend to be significantly less predictable that in the original operation. With each revision surgery the patient loses more bone and muscle mass necessitating a longer surgery and a higher likelihood of complications than in the first surgery.

Author: Sullo & Sullo Attorneys

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