Revision Joint Replacement Surgery
Modern joint replacement surgery and the prostheses used in these surgeries are a mature technology, with much advancement over the past several decades. However, despite the wide success and excellent outcomes, nearly all artificial joints can be expected to wear out after enough time and wear. Joint replacement surgery is analogous to repairing the moving parts of a car, then sealing the engine compartment and achieving decades of 16+ hours of daily use without lifting the hood again!
Interestingly, many of the revision surgeries that we perform today are not so much because the implant failed, but rather because the bone surrounding the implant failed and no longer provides adequate support. The prostheses gradually may become loose.
There can be a number of reasons why joint replacements need to be revised. Trauma and periprosthetic fractures (fractures that occur around the replacement) often result from the same types of accidents that routine broken bones occur in, such as falling or being involved in a motor vehicle accident. Mechanical (aseptic) loosening is another common cause, as the prosthesis becomes loose from the surrounding bone; this often is an indirect result from a slow inflammatory reaction from worn away plastic material (osteolysis). Infection is another cause for revision surgery. Other potential causes include instability or recurrent dislocations, or mechanical failure, such as breakage of the artificial joint parts, although this has become a very uncommon reason in recent years when compared to those listed above.
Regardless of the reason, revision surgery is a complex and demanding surgery, with a wide variation in complexity depending on the diagnosis and underlying problem, scar tissue, potential damage to nerves or blood vessels (again, often because of scar tissue or calcified tissue called heterotopic bone), and longer surgical time and increased blood loss because of the need to remove the old components.
Revision joint replacements are among the most complex procedures in modern orthopaedics, and in contrast to routine primary (first time) joint replacement surgeries, relatively few surgeons and centers perform revision surgeries. For that reason, many of our patients undergoing revision surgery have been referred from other centers or surgeons.
Trauma and Periprosthetic Fractures
When a patient with an artificial hip or knee is involved in a fall or trauma, most often it is the surrounding bone that breaks before the metal prosthesis fails. As a result, the bone surrounding and anchoring the artificial joint may fracture, requiring that the joint replacement be revised as part of the surgery to treat the broken bones.
This often is a significantly more complex procedure than simply treating the fracture alone, as the old prosthesis may be loose but still attached in places to some bone fragments or cement. Old cement usually has to be completely removed from the bone, a time-consuming process that leads to extended operating time and increased blood loss. Scar tissue around the area leads to an increased incidence of nerve injury and bleeding. Once the hip or knee replacement has been reconstructed with the surrounding fracture stabilized with fixation (often wires, plates, screws, and/or bone graft), it is common that a prolonged period of limited weight-bearing is needed in order to allow the fractured bone surrounding the prosthesis to heal.
Mechanical (Aseptic) Loosening and Osteolysis
Another relatively common reason for failure of an artificial hip or knee is loosening of the bone surrounding the implant that occurs without any known infection. Over time, a patient's bone may simply re-absorb in the area that previously held the prosthesis with bony ingrowth or cement, leading to the gradual onset of pain as the prosthesis loosens.
A bone scan (not to be confused with a bone density scan, which checks for osteoporosis) is often helpful for diagnosing early loosening of a prosthesis that cannot yet be seen on regular x-rays. When loosening has been progressing for some time, advanced loosening changes become visible on regular x-rays without the need for a bone scan.
A common reason for accelerated loosening is a process known as osteolysis. This term simply refers to the resorption of bone, but it usually is indirectly related to a slow inflammatory reaction caused by plastic wear. If an artificial joint contains a metal or ceramic surface that rubs against a plastic (polyethylene) surface, over a period of years millions of microscopic plastic particles are generated from the wear. White blood cells try to digest these plastic particles, and when they cannot be digested, the cells burst and release the enzymes that they normally use to digest bacteria and foreign bodies. As a result of this process being repeated millions of times, some of the bone that anchors the prosthesis in place is reabsorbed, leading to loosening.
To learn more about Joint Replacement Surgery or to make an appointment, please call us at 203.598.0700.