A Primer on Knee Surgery
James, a 64-year-old white male, has a history of debilitating osteoarthritis in his left knee, as well as type II diabetes and hypertension. He is scheduled for total knee replacement (TKR) surgery in the morning. Preoperative lab tests show white blood cells in his urine – a sign of an untreated urinary tract infection. The physician orders one gram of intravenous cefazolin to be given upon arrival in the operating room (OR).
On the evening before surgery, a staff nurse shaves his left leg. The next morning, the physician delays surgery, there is a lack of traffic control in the OR, and an OR tech is found to be wearing artificial nails. James is at risk for a postoperative surgical site infection (SSI).
Given that SSIs account for 38 percent of postoperative infections, potential complications must be weighed carefully against the benefits of surgery. In the case study, susceptibility was increased not only by existing chronic and acute health conditions, but also by rescheduling the procedure and the failure of staff to comply with practice guidelines set by the Centers for Disease Control and Prevention (CDC).
While infection is only one of the possible risks involved in total knee replacement surgery, the procedure itself is highly successful. Researchers have found that the operation relieves pain in over 90 percent of cases and most prostheses last 10 to 15 years before requiring adjustments.
As a result, the numbers of TKRs performed in the U.S. are on the rise. In 1990, according to the Agency for Health Care Policy and Research – now known as the Agency for Healthcare Research and Quality (AHRC) – there were 150,000 operations with total expenditures of $3.5 billion – or $9,000 per procedure in hospital costs alone. Just nine years later, reports the American Academy of Orthopaedic Surgeons, 267,000 procedures were completed. The average surgical patient was 68 years of age, with women comprising 61 percent of the candidates.
Given that the “graying of America” is in full swing, healthcare travelers and permanent staff alike should become more familiar with the characteristics of disorders prompting the degenerative process. By understanding different surgical alternatives, contraindications, potential complications, and follow-up care, professionals can assist patients in regaining function and promote positive outcomes.
UNDERSTANDING THE CAUSES
The normal knee is a complex joint consisting of bones and soft tissue structures designed to move and endure the forces of everyday activity. Two of the knee’s compartments are located at the junction of the tibia and femur, with the third lying beneath the patella, or kneecap. Each absorbs the stress of activity through cartilage, or meniscus, a rubbery tissue that protects the bone.
Arthritis in general, and osteoarthritis in particular, are responsible for the inflammation and subsequent degeneration of joints. Sudden or acute injury can cause arthritis, resulting in pain, swelling, warmth, and redness. Osteoarthritis, the most common form of the disorder, is the primary reason knee joints degenerate. A disease of the cartilage, osteoarthritis causes this joint surface to slowly erode until the underlying bone is exposed. As the bones rub together, individuals experience significant pain.
Osteoarthritis of the knee may develop in each of the weight-bearing compartments. In early stages, it is usually confined to one area while the other two remain relatively healthy. When affecting the inside (medial) compartment, the disease produces a bowleg deformity. If the outside (lateral) area is impacted, patients suffer from a knock-knee effect. Since this condition is progressive, it can be managed conservatively in the short-term. Nonsteroidal anti-inflammatory drugs, nutritional supplements such as glucosamine and chondroitin sulfate, cortisone injections, and physical therapy – as well as weight loss – may delay the need for surgery, but eventually many people require reconstruction.
Rheumatoid arthritis, caused by an immune system dysfunction, can also affect the knees. Abnormal antibodies are produced and deposited in the lining tissue of the joints (synovium). This causes chronic inflammation and slow destruction of the cartilage. All of the synovial joints in the body can be affected and the level of arthritis is equal for both sides, with the left and right hands, knees, or ankles, for example, being affected.
ASSESSMENT TECHNIQUES
The primary techniques for determining the presence of osteoarthritis of the knee – and potential candidacy for surgery – are a detailed patient history and physical exam. Providers need to keep in mind that as knee joints degenerate, patients might experience fluid retention, decreased range of motion, morning stiffness, and bone spurs. Additionally, pain initially present only during weight-bearing exercises often becomes worse and more constant. As suggested by AHRQ’s Total Knee Replacement Patient Outcomes Research Team (PORT), professionals should note any crackling sound in the knee, evaluate range of motion, quadriceps muscle strength, and joint stability, and check for pedal pulses.
Several diagnostic tools are available as well. Bloodwork can verify the presence of infection or rheumatoid arthritis, while biopsies may rule out any metastatic disease. Standing knee x-rays (preferred over non-weight-bearing ones), CT and bone scans, and MRIs also can provide detailed information.
Another diagnostic technique – arthroscopy – allows physicians to insert small instruments the size of a pen into the knee to observe damage to cartilage, tendons, and ligaments and to confirm a diagnosis of osteoarthritis. Requiring only three tiny incisions, it is much less traumatic than the traditional method of surgically opening the knee with long incisions (arthrotomy). Arthroscopy is also commonly used to trim and smooth degenerated and worn cartilage, thereby reducing the source of inflammation. The synovium may also be trimmed, decreasing swelling further. As the degree of arthritis increases, however, the benefits of arthroscopy diminish. Patients undergoing this procedure almost always are discharged within 24 hours, with full recovery in up to three months.
CANDIDATES FOR SURGERY
While individuals with arthritis are prime candidates for surgery, knee joint replacement is also indicated in those diagnosed with certain knee tumors, reduced function, or pain that limits daily activities or does not respond to conventional therapy.
Typically, the treatment is contraindicated in individuals with knee infections, paralysis of quadriceps, or severe peripheral vascular disease. Additionally, knee joint replacement is not recommended for patients with cancer or other terminal illnesses, morbid obesity, or mental dysfunction.
TYPES OF KNEE RECONSTRUCTION
Since the first attempt at surgically treating the debilitating effects of arthritis over 100 years ago, research on knee reconstruction continues to evolve. In 1968, a Canadian orthopaedist, Frank Gunston, developed a metal on plastic knee replacement secured to the bone with cement. Four years later, John Insall, MD, an Englishman living in New York City, designed the prototype for current total knee replacements.
Several surgical alternatives are available to patients today. Each attempts to relieve pain, delay the progression of osteoarthritis symptoms, and improve quality of life.
Osteotomy
Indicated in active or obese patients under 60, an osteotomy is performed when the medial compartment is damaged. After the joint is debrided, it is repositioned to allow for free movement and even distribution of weight. Surgeons reshape the tibia or femur to remove deformity and improve alignment. Patients undergoing this procedure may resume full activities in three to six months.
Hemicallotasis
A less invasive alternative to osteotomy, this procedure involves attaching the knee with pins to an external frame. Patients are mobile during the several weeks that the device is worn.
Unicompartmental Arthroplasty
When a portion of the knee joint surface needs to be replaced, the treatment of choice is unicompartmental arthroplasty. Candidates must have an intact anterior cruciate ligament (ACL) and experience no inflammation, cartilage calcification, dislocation, or damage to other sections. Suggested for individuals 60 and older who are sedentary but not obese, this procedure involves the removal of bone and the implantation of a prosthesis.
Patients stay in the hospital two to three days and the knee recovers in two to three months. Physical therapy is required to restore motion and strength. This treatment is less commonly performed than total knee replacement because, in most cases of arthritis, the joint surfaces are diffusely worn.
Arthrodesis
If total knee replacement failure is considered high, arthrodesis, or knee fusion, is often recommended. With this approach, the ends of the femur and tibia bones are cut flat then pressed together so the leg is just slightly bent and held in this position by pins or plates and screws. The ends of the bones grow together over a couple of months, and the knee fuses in a nearly straight position. Though the knee can no longer bend, it is not painful and most patients walk with only a slight limp.
Chondroplasty
Also called autologous chondrocyte implantation, this new technique has been performed on young patients with knee defects who were at risk for developing osteoarthritis. Considered an option for patients whose knees are damaged by injuries, it combines arthroscopy with the removal of healthy tissue, which is then grown in a laboratory and reimplanted into the joint, stimulating regeneration.
Total Knee Replacement
Traditionally, the approach to reconstructive surgery has been to replace all three compartments of the knee when function deteriorates substantially. With TKR, the surfaces of the knee joint are replaced with prosthetic materials, consisting of metal on the femoral (thigh) side and plastic on the tibial (shin) side.
The knee joint is opened through a vertical incision based on the front of the kneecap. Appropriate jigs and templates are used to accurately remove the surfaces of the femur and tibia and to shape them to receive the prosthetic components. Some ligament adjustment may be necessary. The patella is similarly prepared for a new plastic surface.
Prostheses can be secured in two ways. One fixation technique applies fast-curing bone cement (polymethylmethacrylate), while the cementless design is textured to encourage bone growth into the implant for stability. Generally, cemented knee replacements – preferred for older patients – last 20 years or more, depending on activity levels, weight, and health conditions. Cementless implants, introduced in the 1980s, may require pegs or screws for stability until bone growth occurs. While long-term comparisons are not possible, research has shown that cementless designs, often recommended for younger patients, can be as successful as cemented prostheses in the short-term. A combination of the two approaches – with the tibial component cemented and the femoral section cementless – is also showing promise.
After surgery, most patients stay in the hospital for several days and have extensive physical therapy upon discharge. TKR provides excellent pain relief, is durable, and restores function, but recovery can take up to one year.
As loosening, wear, osteolysis, or component breakage may occur slowly over time without pain or other symptoms present, experts suggest evaluating total knee replacements yearly with a diagnostic x-ray. If failure occurs, revision total knee replacement surgery can be performed. While results and recovery times for this operation may differ from primary TKRs, most patients experience good pain relief and can walk as desired.
COMPLICATIONS AND RISKS FOR TKR
Similar to any major surgical procedure, there are several potential risk factors involved in TKR. In addition to the loosening or dislocation of prostheses, patients may develop stiffness or complications from the general or regional anesthesia used.
Additionally, following total knee surgery, patients might be susceptible to deep vein thrombosis. Blood clots that break loose and pass through the heart and lungs can cause pulmonary embolus. Anti-coagulation medications are routinely given to minimize the chance of this occurrence. However, these medications also carry a risk of bleeding, especially at the surgical site.
Despite the success of TKR surgery, infection is a major area of concern. Patients with diabetes mellitus, urinary tract infections, or active concurrent infection elsewhere, are highly susceptible. Those who have had previous surgeries on the affected joint, use oral steroids, or suffer from poor nutrition or obesity are also at increased risk. Advanced age, a history of smoking, and prolonged operative time and hospitalization are additional factors affecting the incidence of infection.
In particular, prosthetics lead to a high rate of infection, caused by low-virulent pathogens that, once established, are difficult to treat. The predominant infectious organisms are gram-positive (Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus Group B). These bacteria readily attach to the devices, encasing themselves in a protective biofilm. This makes them more resistant to white blood cells, impairing the host response and/or causing direct tissue damage.
The diagnosis and treatment of deep infections is challenging. In the United States, the prosthesis is surgically removed and debridement is performed. Following a period of antibiotic therapy, the implants are replaced.
Pain is another complication. Although 90 percent of patients have complete, or nearly complete, relief following TKR surgery, some experience persistent pain. Even if their prostheses are functioning correctly, individuals may be affected. While the pain may resolve in time, additional surgery could be required if a specific cause and treatment can be identified.
FUTURE TRENDS FOR TKR
There are still many areas where enhancements can be made with total knee replacement surgery. Research to perfect the fixation of artificial joints to bone is ongoing. In addition, different materials, including metals, plastics, ceramics, and composites, are being studied to increase the life of prostheses. Over the years, there have been many design changes. As the prosthesis evolves into more of a “normal” knee, functional results improve.
To meet the goals of researchers – namely, long-term success and normal function – it is necessary to properly evaluate candidates for specific types of knee surgery. Today, scientists are divided on the benefits and risks of replacing one or both knees. Currently being debated is the likelihood of complications occurring more frequently with simultaneous bilateral TKRs than with staged procedures.
While repeat surgery is uncommon for the elderly, scientists have discovered that, in the general population, certain factors increase the need for additional knee replacements. These include: male sex, younger age, longer length of hospital stay for primary knee replacement surgery, other health conditions, unspecified arthritis type, surgical complications, and primary knee replacement performed at an urban hospital.
Researchers are also looking at less invasive alternatives to knee surgery as ways to control the staggering disability and economic costs of arthritis treatment. While the study is not yet open for patient recruitment, a clinical trial sponsored by NIH’s National Center for Complementary and Alternative Medicine will examine the cost-effectiveness of and long-term outcomes following acupuncture treatment for osteoarthritis of the knee.
IMPROVING OUTCOMES
On the road, mobile providers can assist in evaluating patients’ range of motion, developing care plans and exercise regimens, and reviewing home health needs. Physical therapists, in particular, can design exercise programs that include range of motion, strengthening, balance, endurance, and functional activities. By sharing local and national support resources – and emphasizing the importance of compliance with exercise regimens – travelers can help to improve the quality of life for individuals considering, undergoing, and recuperating from knee surgery.
For a list of professional and consumer organizations providing information on this topic, visit “Knee Surgery Resources.”
To view the full text of the SSI guidelines released by the Centers for Disease Control and Prevention Hospital Control Practices Advisory Committee, visit http://www.cdc.gov/ncidod/hip/SSI/SSI_guideline.htm
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