Revision of Total Knee Replacement
Implants may fail for any of several physiologic reasons: loosening, infection, dislocation, or patient-related factors. The anatomy and pathophysiology of failed joint replacement implants contribute to the decision to perform revision surgery.
Some revisions will be necessary because the implants have loosened. When they were first put in, the large metal and plastic implants of joint replacement were placed with the intention of staying fixed for a long time. They were either cemented into position or bone was expected to grow into the surface of the implant. In either case, the implant was firmly fixed to bone.
However, the friction of the joint surfaces rubbing against each other wears away the surfaces of the implant, creating tiny particles. These particles accumulate around the joint. In a process called aseptic, or noninfected, loosening, the bonds of the implant to the bone are destroyed by the body's attempts to digest the wear particles. When the prosthesis becomes loose, the patient may experience pain, deformity, or instability. In addition, the process of digestion, or lysis, of wear particles also digests normal bone. This can weaken or even fracture the bone, and jeopardize the success of the revision surgery. In this event, surgery will also address the bone stock deficiencies. Aseptic loosening is the most common mode of failure of hip and knee implants.
Infection is another physiologic cause of implant failure. The large foreign metal and plastic implants can serve as a surface for bacteria to latch onto. In addition, the tissue that has been previously operated on has an altered blood supply, which may not be adequate to fight infection. Even if the implants remain well-fixed, the pain, swelling, and drainage often make revision necessary. Lastly, the chronic fight against an infection can weaken the patient and endanger their life. Realistic risk of infection with current surgical techniques and antibiotic regimens is about 0.5%.
Dislocation is yet another mode of failure of joint replacement surgery. (Dislocation is a sudden popping out or migration of the implant from its normal position.) It is more commonly a problem of hips rather than knees. The rate of dislocation after hip replacement ranges from zero to 10%, but averages about one in 50 patients. Some of these patients will experience multiple dislocations and require revision. The dislocation may be caused by loosening, inadequate soft tissues, bony or scar tissue impingement, incompatible component position, neurologic factors (such as neuropathy or Parkinsonism), or patient noncompliance.
Younger and more active patients have a higher rate of revision. Obese patients have a higher incidence of wear and loosening. Patients whose primary surgery was performed for inflammatory arthritis, patients with avascular necrosis, and patients with a previous hip fracture are at higher risk for loosening. These anatomic and physiologic conditions lead to the necessity of joint revision surgery.
The natural history of failed implant surgery is an increase in pain, a change in the position of the implant, or a decrease in the function of the implant with limp or dislocation. Patients who demonstrate these symptoms and signs may require revision joint surgery. Therefore, a standard assessment is performed, including a history and physical examination, X-rays, laboratory tests, and possibly aspiration or scintigraphic studies.
Treatment Alternatives to Revision Surgery
Although there are some surgical alternatives to revision joint surgery, they are rarely used, due to two main factors: these procedures can sometimes be more complex and lead to worse results than revision surgery and the results of modern revision joint surgery are outstanding.
One alternative to hip revision is called resection arthroplasty. This involves removal of the entire hip joint. This can give some relief of pain but naturally will lead to a decrease in function as compared to modern hip replacement.
Another procedure is called fusion, also known as arthrodesis. It may be used as an alternative to knee revision. Again, pain may be relieved, but at the expense of keeping the knee in a straight, nonbending position. These procedures may have a use in cases of severe joint infections that cannot be eradicated.
Greater than 90% of patients who undergo revision procedures will be expected to have good to excellent results, even considering the higher rate of complications as compared to first-time joint replacement. After weighing the alternatives, most patients and physicians prefer revision to other surgical options.
Benefits and Limits
Revision joint surgery, as previously stated, can be a major procedure that requires complex techniques. It can also have a higher complication rate than primary surgery. In addition, some patients are not medically able to tolerate a long and difficult surgical procedure.
Because of this, nonoperative treatment options are sometimes considered as a first step in the treatment of a failed implant. Obviously, problems that would damage remaining bone quality or make later treatment difficult would eliminate the nonsurgical options. Also, patients treated nonsurgically must realize that they may have significant limits on their function and activity.
Pain that is caused by a failed joint replacement may initially be treated with an increase in pain medications. These treatments may be limited by side effects, such as gastrointestinal upset and ulcers, drowsiness, and constipation. Increased reliance on assistive devices, such as a cane, crutches, or a walker, may be used to postpone revision. Likewise, a brace may decrease episodes of instability or dislocation. These techniques may be cumbersome and a burden to the patient, however. Modification and restriction of activity itself can be used to decrease symptoms. The less active a patient is, the less likely they are to be symptomatic. Finally, some infected joint replacements are treated with suppressive antibiotics to control the infection symptoms. This approach has a variable success rate and would not be expected to eradicate the infection.
Surgical Intervention and Considerations: Knee Surgery
Knee revision surgery entails consideration of the femur (thigh bone), tibia (shin bone), and patella (kneecap) components.
- Bone stock deficiencies are classified according to several grading systems, and lysis, fracture, or stress shielding can lead to bone loss.
- The failed components are removed by a combination of surgical methods and specialized instruments. Reconstruction may require implants with extensions to reach better-quality bone and that effectively replace lost ligament stability.
- Ground-up or bulk bone graft may be used.
- An implant is fixed in place through cemented or bone in-growth techniques.
Joint revision surgery is usually performed as a planned surgical procedure. Patient condition and characteristics of the failed and new components will contribute to the planning process. Most surgical methods will proceed along a similar stepwise pattern.
Preoperatively, blood donation may be required, due to the extensive dissection necessary to perform this surgery. Additionally, antibiotics will be given either before or early in the case to aid in prevention of infection. The patient will be brought to the operating room suite and anesthetized for pain control and muscle relaxation.
ConsiderationsThe surgical incision may utilize the site of the previous incision or it may be placed in another location. It is likely that a more-extended incision will be used in order to facilitate implant and scar removal as well as simplify the insertion of the new component. Great care is taken during dissection, as the normal position and appearance of nerves and blood vessels can be altered by the previous surgery and wear of the old components. The failed implants and any old cement pieces are removed using specialized techniques. In addition, abnormal bone and scar tissue is removed to achieve a new bed for fixation of the prosthesis.
Reconstruction of the hip or knee bones must then be performed. Some procedures will have bone almost equal to a primary procedure. Others will have more-severe bone loss. In these cases, revision will require the use of bone graft and/or metallic plates, cages, and screws. Once bone has been reconstructed, the process of implantation can begin.
Several techniques are available to implant the revision joints.
Knee revision implants
- May be about the same size as primary implants, or they can have extensive stems, wedges, and build-ups if bone quality is poor.
- May substitute for damaged or absent ligaments.
- Will often use cement for fixation, but occasionally uncemented techniques are selected.
Once the components are in place, the closure of tissue layers is performed. Drains are placed to collect any fluids or blood. The joint may be protected after surgery in a brace or splint. The medical condition of the patient is closely monitored and blood count is assessed. Antibiotics and some method of blood clot prevention will be continued in the postoperative period and thus complete the steps of the surgical procedure.
Potential Surgical Complications
Any surgery can have potential complications. The complexity of revision joint surgery increases the chance of complications. A realistic assessment of these risks is essential prior to a revision procedure.
Infection, bleeding, and trauma to nerves or blood vessels are a potential with any surgical procedure. These are addressed and minimized by using antibiotics before and after surgery, working in a sterile operating room, use of blood-preserving techniques, and utilizing well-planned surgical exposures. The risk of these complications is higher than primary procedures.
Malpositioning or loosening of the new components is possible. In addition, the revision implants may migrate due to poor bone quality or inadequate fixation to the bone. More-severe destructive processes with greater preoperative bone loss are more likely to create this problem.
Deep venous thrombosisx and pulmonary embolism, or blood clots in the legs or lungs, can occur in conjunction with a revision procedure. The extensive surgery with subsequent twisting and trauma of the blood vessels can create clotting. In addition, the relative immobility of the patient after surgery increases the chance of clots. A clot in the lungs can become a life-threatening situation if the clot is large.
Dislocation of a hip implant is more common after revision surgery. This is due to the extensive dissection required to remove the failed components as well as the poorer quality of the surrounding soft tissues after multiple procedures. In order to decrease the chance of dislocation, soft tissues are stretched out, which can lead to a lengthening of the operated leg.
Medical conditions can be aggravated or caused by the extensive revision procedure. Patients may have heart and lung complications, or stroke conditions. Rarely, death can occur. The decision to perform revision joint surgery is made when the benefits of pain relief and functional improvement outweigh the risk of these potential complications.
Rehabilitation and Convalescence
Rehabilitation after joint revision surgery is as aggressive as possible without damaging the new implant construct. In most cases, physical therapy will be initiated within 24 hours of the procedure. Therapy will continue for up to three months following the surgery.
Weightbearing may be restricted at first and a protective brace may be utilized.
Assistive devices, such as a walker or crutches, will be used early in the convalescence period. Patients will progress to a cane or no assistive device. In the hip , as in primary surgery, precautions may be placed regarding sitting, bending, and sleeping positions. For the knee,14 emphasis will be placed on regaining motion.
Restrictions remain in place for six to 12 weeks. Some patients will begin their rehabilitation in a rehabilitation hospital setting, while others will opt for home and outpatient therapy.
Improvement in strength and limp may continue to improve over one to two years.
As with any operation, knee replacement surgery has risks as well as benefits. Most people who have a knee replacement do not experience serious complications.
Complications occur in about one in 20 cases, but most are minor and can be successfully treated. Possible complications include:
- Infection of the wound
- Unexpected bleeding into the knee joint
- Ligament, artery or nerve damage in the area around the knee joint
- Blood clots or deep vein thrombosis (DVT) – clots may form in the leg veins as a result of reduced movement in the leg during the first few weeks after surgery. They can be prevented by using special support stockings, starting to walk or exercise soon after surgery, and by using anticoagulant medicines
- Fracture in the bone around the artificial joint during or after surgery – treatment will depend on the location and extent of the fracture
- Excess bone forming around the artificial knee joint and restricting movement of the knee – further surgery may be able to remove this and restore movement
- Excess scar tissue forming and restricting movement of the knee – further surgery may be able to remove this and restore movement
- The kneecap becoming dislocated – surgery can usually repair this
- Numbness in the area around the wound scar
- Allergic reaction – you may have an allergic reaction to the bone cement if this is used in your procedure
- In some cases, the new knee joint may not be completely stable and further surgery may be needed to correct it.