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Белорусский государственный медицинский университет

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Травматология и ортопедия

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Essentials of Orthopedic Surgery, third edition / 12-The Knee

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464 B.G. Evans

surgery to debride the torn portion of the meniscus. In older patients, if the meniscal tear does not cause locking, frequently these can be treated with nonsteroidal antiinﬂammatory (NSAI) medications and an intraarticular corticosteroid injection. These treatments will reduce the effusion and pain. With continued activity, the soft meniscal tissue can be worn down and a stable edge reestablished.

Ligament Injuries

Injury to the ligamentous structures are manifest by instability in the knee. In addition to pain and swelling, patients report a sense of the knee shifting or giving way, which may occur only with speciﬁc activities such as descending stairs or when turning on the loaded extremity. The initial management of these injuries is rest, ice, and elevation. A splint or knee immobilizer can also be helpful to protect the knee. As the initial pain subsides, it is important to begin to work on restoring range of motion, using a brace to protect the injured ligament. As the pain further decreases, strengthening is begun. If after the strengthening program is completed the knee remains unstable, the patient may be a candidate for surgical reconstruction.

Patellofemoral Pathology

The patellofemoral joint is one of the most common areas of pain in the knee. Common complaints are anterior knee pain, which is aggravated by activities involving high loads on a ﬂexed knee such as stair climbing or bicycling. This pain can be the result of degenerative changes in the patellofemoral articulation or a result of maltracking of the patella within the trochlear groove. A grinding or snapping sensation may also be noted. Pain is usually relieved by rest; however, if the patient is sitting for a prolonged period of time with the knee ﬂexed, such as in a theater, on a plane, or during a long car ride, anterior knee pain will result. Frequently patients try to change the position of the knee to relieve their discomfort. This symptom is referred to as movie sign and is indicative of degenerative changes in the patellofemoral joint. Softening of the articular surface is referred to as chondromalacia patella; this can be a primary problem or it may be secondary to excessive trauma to the joint caused by maltracking of the patella within the trochlear groove.

The treatment of these conditions is primarily nonoperative. Improving the patellar tracking can be done through a series of exercises to retrain the quadriceps and through patellar mobilization exercises. The exercise program need to be maintained for a minimum of 6 to 8 weeks to demonstrate beneﬁt. The symptoms frequently recur. If the symptoms are recurrent and do not respond to the nonoperative regimen, and patellar maltracking is evident, operative intervention may be indicated. Operative

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intervention is directed at correcting the patellar tracking and maximizing the quadriceps function with postoperative physical therapy.

Arthritis

The management of arthritic symptoms within the knee is similar to management elsewhere in the body. The nonoperative management of arthritis within the knee consists of a ﬁve-modality approach. The ﬁrst line of therapy is the use of NSAI agents, which will reduce the pain and swelling associated with the knee. Although all the NSAI drugs (NSAIDs) function in a similar fashion, there is wide variation in individual patient response. Therefore, minimally two or three different NSAIDs should be tried. The most common side effect of this course of treatment is dyspepsia.

The second line of treatment of arthritis, the selected use of intraarticular corticosteroid medication, can be effective in patients who have an acute exacerbation of the arthritic pain. The injection can quiet their pain and restore them to a baseline level of discomfort. The injection should not be utilized for the control of baseline pain. If the injection is required at a frequency of greater than one every 6 to 8 weeks, some other course of treatment should be initiated, such as surgery. If the knee is injected more frequently than two to three times per year, the corticosteroid may have a detrimental effect on the articular cartilage.

Physical therapy can be very helpful in the treatment of arthritis of the knee. As the soft tissue sleeve is very important to the function of the knee, by optimizing the function of the soft tissues the symptoms of arthritis can be reduced. Physical therapy should be directed at maintaining the range of motion of the knee and optimizing the strength of the quadriceps and the hamstring muscles. In the late stages of degenerative arthritis, physical therapy may worsen the patient’s symptoms and should be limited to the patient’s tolerance.

Assistive devices such as a cane or crutch may be helpful in the management of arthritis of the knee. These aids can limit the stress across the painful knee and improve the patient’s walking tolerance. The ﬁnal approach to the management of arthritis of the knee is modiﬁcation of the patient’s activities, such as sports, the work environment, and possibly arranging special parking for the patient the patient’s car. Frequently, patients with signiﬁcant knee arthritis are also overweight. Weight loss in these patients can signiﬁcantly reduce symptoms and the need for other treatment modalities.

Surgical Reconstruction for Arthritis

When all nonoperative measures have failed to relieve the symptoms of knee arthritis, surgical intervention should be contemplated. The surgical

466 B.G. Evans

correction of knee arthritis can be separated into treatments that retain the patient’s articular surfaces and knee replacement. Nonreplacement options include the use of arthroscopy to “clean out” the knee; this procedure can remove the small cartilage fragments that accumulate in arthritic joints and debride any loose articular fragments. The pain relief from this procedure, however, is short lived, lasting only 3 to 6 months. Patients should be informed preoperatively that if extensive arthritis is noted during arthroscopy, the pain may be worse after surgery. In that setting, the patient is a candidate for knee replacement.

Patients with osteoarthritis of the knee frequently develop angular deformities. The most common deformity is varus angulation of the knee, which results from erosion of the medial compartment of the knee. As the deformity progresses, a greater portion of the weight-bearing stress is concentrated in the medial compartment of the knee. Osteotomy is a procedure to realign the articulation. The proximal tibia is transected, and a wedge of bone is removed from the lateral aspect. When the two new surfaces are brought together, the varus deformity is corrected. This procedure redistributes some of the weight-bearing stress to the lateral compartment and can result in improved symptoms in the knee. The result is generally successful for 5 to 10 years. Osteotomy is contraindicated in knees that are stiff or unstable. When the symptoms return, knee replacement surgery is indicated.

Arthrodesis or fusion of the knee is an option for the management of young active patients, particularly physical laborers. Fusion results in a stiff straight knee that will allow the patient to ambulate and stand for long periods of time without difﬁculty. However, signiﬁcant limitations also exist. The gait pattern is signiﬁcantly abnormal. In addition, patients will have difﬁculty sitting, particularly in conﬁned spaces such as public transportation and theaters. Resection arthroplasty is a procedure in which the articular surfaces are resected and a ﬁbrous pseudoarthrosis forms within the joint space. Pain may be decreased; however, the knee is signiﬁcantly unstable, requiring a brace for ambulation. Arthrodesis and resection arthroplasty are not commonly performed. Currently, these procedures are reserved for the management of a failed total knee replacement.

Total knee replacement (TKR) is commonly utilized to relieve the symptoms of knee arthritis and restore function (Fig. 12-6). Approximately 200,000 arthroplasties are performed annually in the United States; the average age of patients receiving a TKR is 70 to 74 years. Successful results can be obtained in more than 95% of patients, with survivorship at 10 to 15 years of 90%. All components are currently ﬁxed with polymethylmetacrylate (PMMA) bone cement. Noncemented components, those used with porous ingrowth surfaces for bone ingrowth, have been associated with a higher incidence of loosening and pain.

The proximal tibia is cut perpendicular to the long axis of the shaft, and the femoral articular surface is cut using speciﬁc guides to remove the

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FIGURE 12-6. Standing AP radiograph of both knees 2 weeks after one-stage bilateral knee replacements in the 70-year-old female patient whose preoperative radiograph is shown in Figure 12-4.

femoral trochlea and distal and posterior femoral condyles. The ACL is removed; however, the PCL can be resected or retained depending on the design of implant chosen. For proper function of the arthroplasty, the MCL, LCL, and, if retained, PCL must be carefully balanced. The components are then ﬁxed to the surfaces of the tibia and femur with bone cement. The patella is normally resurfaced as well after resecting the articular surface parallel to the anterior surface.

The patient is mobilized into a chair on the ﬁrst postoperative day, and full weight-bearing may be allowed immediately. However, a knee immobilizer should be utilized to protect the knee from acute ﬂexion while walking, and this is continued until the quadriceps function returns. The critical element of the postoperative therapy is the restoration of motion. If the motion is not restored within the ﬁrst 3 to 6 weeks, maturation of the scar tissue will prevent major gains in motion after that point. Many patients can be safely discharged at 3 to 4 days after surgery.

Frequently, however, these patients require home physical therapy to continue to work on range of motion and ambulation in the ﬁrst few weeks after surgery. The total rehabilitation period after total knee replacement is between 3 and 6 months, although patients are functionally mobile after 2 to 3 weeks. Knee replacement can be performed bilaterally in one stage in medically healthy patients (see Fig. 12-6). The initial increase in debilitation postoperatively is offset by a reduction in the overall period of rehabilitation after sequential unilateral TKR.

468 B.G. Evans

Aseptic loosening of the implants after TKR occurs at a low rate. Several studies have documented a 15-year survivorship of greater than 90% and less than 0.5% per year rate of aseptic loosening after cemented TKR. If a TKR is noted to be loose earlier than 5 years postoperatively, it should be evaluated for deep infection. Deep sepsis is associated with early loosening after TKR. Young age, marked obesity, and high demand also negatively impact upon the long-term survival of the replacement. To date, the best data indicate noncemented TKR are equal to the cemented replacement. Several studies suggest poorer results when cement is not used, particularly for ﬁxation of the tibial component. Increased tibial loosening and pain have been noted with these devices. At present. because of the generally increased cost for the noncemented porous-coated implants and poorer clinical results, the use of these devices is difﬁcult to justify.

The majority of the complaints after cemented TKR are from the patellofemoral joint, which can be the result of poor soft tissue alignment at the time of arthroplasty and may lead to painful subluxation or dislocation of the patellar component. If inadequate bone is resected from the patella at the time of resurfacing, a marked increase in the patellofemoral stress can be noted, which may become painful. Several authors have advocated not resurfacing the patella. However, several studies now demonstrate a higher rate of patellofemoral complaints after TKR without patellar resurfacing. If signiﬁcant patellofemoral arthritis exists at the time of arthroplasty, patients with weight greater than 60 kg and height greater than 160 cm will have more pain postoperatively if the patella is not resurfaced.

The most common complication after TKR is thromboembolic disease (TED). The rate of deep venous thrombosis ranges from 25% to 50% of cases in patients evaluated with venography or duplex Doppler analysis. Similar to patients receiving total hip replacement (THR), currently it is recommended that all patients receive some form of prophylaxis against TED. Mechanical methods such as the pneumatic compression stockings appear to have a greater beneﬁt after TKR compared to THR. Low-dose Coumadin and aspirin are currently the most commonly utilized medications. The efﬁcacy of low molecular weight heparin is currently under investigation.

Deep infection occurs at a rate of approximately 1% after TKR for osteoarthritis over the life of the implant. The most common organisms are skin ﬂora, primarily Staphylococcus aureus and Staphylococcus epidermidis. In particular to knee replacement, the relatively thin soft tissue envelope at the inferior aspect of the skin incision can lead to wound dehiscence and allow entry of the ﬂora into the joint. Any area of skin breakdown after TKR should be treated aggressively to prevent deep infection, particularly in patients with prior incisions and in those with diabetes or signiﬁcant vascular disease.

If a deep infection is established, the only way to eradicate the infection is to remove the implants and cement and then thoroughly debride the

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joint. A cement spacer is then placed into the joint space, and the patient should receive 6 weeks of intravenous antibiotics. The serum bactericidal titers (SBT) again should exceed 1:8. After 6 weeks, the knee can be reimplanted if adequate soft tissue and bone remains. However, as a result of the inevitable scarring the clinical result is compromised.

Occasionally, after TKR range of motion of the knee does not progress well. If the patient is less than 2 to 6 weeks past surgery, a gentle manipulation of the knee in the operating room under anesthesia may be beneﬁcial.

If the motion cannot be restored, particularly if the patient is beyond 6 weeks after replacement, additional surgery may be necessary to restore functional range of motion.

Summary and Conclusions

The knee is a complex joint with function provided by the combination of osseous and soft tissue structures. The soft tissue envelope plays a signiﬁcant role in the pathology of the knee and in the management of these conditions. With careful history, physical examination, and appropriate use of the available diagnostic modalities, knee pathology can be accurately determined and successful treatment instituted. Successful management of knee pathology includes treatment of the speciﬁc etiology, but optimal management of the soft tissue envelope with directed physical therapy is essential to an optimal outcome.