I. Osteoarthritis
A. Etiology and diagnosis
1. Primary changes of osteoarthritis (OA)
a. Loss of articular cartilage
b. Remodeling of subchondral bone
c. Formation of osteophytes
2. The disease process usually involves all of the tissues that form the synovial joint (articular cartilage, subchondral bone, metaphyseal bone, synovium, ligaments, joint capsule, and muscles crossing the joint).
3. OA is the most common cause of long-term disability in patients older than 65 years.
a. It affects all ethnic groups and geographic locations.
b. It is more common in women.
c. The knee is the most commonly affected joint.
d. It occurs most frequently in the hands, feet, knees, hips, and spine, but it can develop in any synovial joint.
4. Although the name implies that it is an inflammatory disease, inflammation does not appear to be a major component of OA in most patients.
5. There is a strong association between age and OA, but OA is not simply the result of mechanical wear from joint use.
6. The etiology of OA is multifactorial.
a. On a cellular level, it appears that OA is the result of deterioration in the ability of chondrocytes to maintain and restore articular cartilage.
b. Evidence that chondrocytes undergo age-related telomere erosion and increased expression of the senescence marker, β-galactosidase, suggests that cell senescence is responsible for the age-related loss of chondrocyte function.
c. Evidence is emerging that subtle morphologic abnormalities around the hip that result in femoroacetabular impingement are a major contributing factor to hip OA in young patients.
d. The known causes of secondary OA are listed in
Table 1.
e. The age of onset of secondary OA depends on the underlying cause.
[Table 1. Causes of Secondary Osteoarthritis]
f. Overall, women are disproportionately affected at a higher rate than men; men younger than 55 years are diagnosed at a higher rate than women.
B. Physical examination
1. Knee
a. Physical examination of the knee often reveals restricted range of motion, crepitus, tenderness along the joint line, an effusion, and some degree of deformity.
b. Patellar tracking and ligament stability should be assessed.
2. Hip
a. It is important to stabilize the pelvis when examining the hip.
b. The lumbar spine may compensate for restricted motion in the hip.
c. Passive range of motion of the hip joint may elicit symptoms.
d. Loss of internal rotation of the hip is usually associated with hip pathology, including OA.
e. Hip flexion contracture or limb length discrepancy may be present.
f. Pain with hip flexion, internal rotation, and adduction is suggestive of femoroacetabular impingement.
3. Atrophy in muscles crossing the affected joint is often present in chronic disease.
4. Patients with OA have an altered gait and increased energy cost. The degree of knee pain is correlated with decreased walking speeds, step rates, single-limb stance time, and vertical ground reaction forces.
C. Radiographs
1. Weight-bearing radiographs are the most effective at confirming the diagnosis of OA.
2. In the knee, sunrise views and AP views in flexion may demonstrate OA not visible on standard AP and lateral views.
3. Radiographic changes
a. Narrowing of the cartilage space
b. Increased density of the subchondral bone (sclerosis)
c. Osteophytes
d. In more severe cases, subchondral cysts (geodes), loose bodies, joint subluxation, deformity, and malalignment may be present.
e. Bony ankylosis is rare but may occur.
D. Treatment
1. Treatment of pain related to OA includes medications, injections, orthoses, activity modification, weight loss, physical therapy, and assistive devices.
2. Medications that are effective at treating the symptoms of OA include acetaminophen, glucosamine and chondroitin sulfate, nonsteroidal anti-inflammatory drugs, and prednisone.
3. Orthoses include shoe wedges and unloading knee braces. The usefulness of bracing is controversial.
II. Inflammatory Arthropathy
A. Preoperative considerations
1. Inflammatory arthropathies are often associated with poor host bone quality as a result of oral corticosteroid treatment or disuse osteopenia.
2. Articular cartilage damage may be the indication for joint replacement, but joint replacements are done in these patients for other reasons as well, such as femoral neck fracture or femoral head osteonecrosis.
3. Total hip arthroplasty (THA) is preferred over hemiarthroplasty in conditions such as rheumatoid arthritis (RA) and systemic lupus erythematosus because of involvement of the entire joint and cartilage damage.
4. Patients with RA have an increased risk of late prosthetic infection.
5. Deformity of the lumbar spine may predispose patients with RA or spondylitis to acetabular component malpositioning.
6. 90% of patients with RA have cervical spine involvement.
a. Patients with RA should have cervical spine lateral flexion/extension views prior to elective surgery to rule out atlantoaxial instability.
b. A difference of >9 to 10 mm in the atlantodens interval on flexion/extension views or space available for the cord of <14 mm is associated with an increased risk of neurologic injury and usually requires surgical treatment.
7. Patients with RA also may have micrognathia or loss of motion in the temporomandibular joint.
8. Several of the inflammatory arthropathies are associated with acetabular protrusio.
9. Preoperative planning in patients with juvenile rheumatoid arthritis is imperative to ensure that appropriately sized (small) components are available.
10. The risk of infection for total joint arthroplasty is probably increased in patients with psoriatic arthritis.
a. Avoid skin incision through active psoriatic lesions because they can be highly colonized by bacteria.
b. Preoperative treatment of lesions in an incision area is recommended.
11. Patients with ankylosing spondylitis may have an increased risk of heterotopic ossification, although this risk is not supported by strong data.
a. These patients are also at greater risk of pulmonary complications because of chest wall constriction and fibrotic changes.
b. Preoperative cardiopulmonary evaluation is recommended.
c. Compared with patients with OA, the risk of infection is slightly higher in patients with ankylosing spondylitis, and patients typically can expect a lower level of functional return.
B. Intraoperative considerations
1. Cemented and uncemented acetabular components have been used successfully in patients with inflammatory arthropathies.
2. Exposure of the hip joint is more difficult in cases of ankylosis or acetabular protusio.
a. An osteotomy of the trochanter can also be used to facilitate exposure.
b. Conventional trochanteric osteotomy has been associated with an incidence of nonunion approaching 20%. Therefore, a trochanteric slide or an extended osteotomy may be considered as alternatives to achieve exposure.
c. Because exposure is typically more challenging, a femoral neck osteotomy should be considered in situ if the femoral head cannot be easily dislocated.
3. Fixed pelvic hyperextension and the loss of lumbar lordosis may result in exaggerated anteversion of the acetabular component in the standing position.
a. Excessive flexion of the acetabular component should be avoided to reduce the risk of anterior dislocation.
b. Some surgeons prefer anterior approaches for these patients because large hip flexion contractures can be improved with anterior capsulectomy.
c. Adductor tenotomy should be considered when adduction contracture is present.
III. Osteonecrosis
A. Diagnosis and management options for the knee
1. Osteonecrosis of the knee is much less common than osteonecrosis of the femoral head.
2. There are two distinct osteonecrosis presentations:
a. Spontaneous osteonecrosis of the knee (SPONK); see
Figure 1
[Figure 1. Spontaneous osteonecrosis of the knee. A, AP radiograph of both knees showing a SPONK lesion in the medial condyle of the right knee. B, MRI scan showing a unilateral SPONK lesion.]
[
Figure 2. Osteonecrosis of the hip. A, A crescent sign (arrow) is seen as a subchondral radiolucency on a standard hip radiograph. B, MRI scan showing small necrotic segment (arrow). C, Radiograph of same patient in part B; note that the lesion is not visible.]
i. SPONK is more common in women older than 55 years.
ii. In 99% of patients, SPONK involves only one joint and only one condyle (typically, the epiphysis of medial femoral condyle). There is some evidence that these lesions actually represent microfractures.
b. Secondary osteonecrosis of the knee
i. Secondary osteonecrosis typically involves more than one compartment of the knee or even the metaphyseal bone.
ii. Approximately 80% of cases have bilateral involvement, and many cases are multifocal.
iii. Patients with secondary osteonecrosis are also typically women (3:1), but they are usually younger than 55 years of age and have associated risk factors for osteonecrosis.
iv. Osteonecrotic lesions can occur in the epiphysis, diaphysis, or metaphysis.
B. Evaluation
1. Differential diagnosis—It is important not to confuse osteonecrosis with similar knee disorders such as osteochondritis dissecans, transient osteoporosis, bone bruises, or occult fractures.
a. Osteochondritis dissecans is more common in the lateral condyle of adolescent (15- to 20-year-old) males.
b. Transient osteoporosis is more common in young to middle-aged men.
i. Transient osteoporosis is most common in the hip, followed by the knee and foot/ankle.
ii. Multiple joint involvement, referred to as transient migratory osteoporosis, is present in about 40% of patients with transient osteoporosis.
c. Occult fractures and bone bruises are generally associated with trauma, bone fragility, or overuse.
2. Imaging
a. MRI is the most useful single study for differentiating osteonecrosis from other conditions.
i. Bone edema on MRI is a common feature of OA, osteonecrosis, cartilage injury, and transient regional osteoporosis.
ii. With osteonecrosis of the hip, a double density sign on MRI is commonly seen, caused by the advancing edge of neovascularization and new bone formation (Figure 2).
3. Treatment
a. Nonsurgical
i. Nonsurgical treatment includes analgesics (narcotics and nonsteroidal anti-inflammatory drugs), protected weight bearing, and physical therapy directed at quadriceps strengthening.
ii. Good results have been demonstrated with nonsurgical management of SPONK but not with secondary osteonecrosis.
b. Surgical options for SPONK
i. High tibial osteotomy when angular malalignment is present
ii. Unicondylar knee arthroplasty (UKA) when there is a smaller total area of bone involvement
iii. Total knee arthroplasty (TKA) for larger lesions or bone collapse that precludes the use of UKA
c. Surgical options for secondary osteonecrosis
i. Diagnostic arthroscopy (to remove small, unstable osteochondral fragments)
ii. Core decompression (for lesions that do not involve the articular surface)
iii. Osteochondral allograft (for larger compartmental lesions in younger patients)
iv. TKA (when there is a large area of involvement, articular collapse, or multiple compartment involvement)
IV. Osteonecrosis of the Hip
A. Epidemiology/overview
1. Femoral head osteonecrosis (ON) occurs in 20,000 patients per year and accounts for approximately 10% of the THAs performed in the United States.
2. The average age at presentation is 35 to 50 years.
3. The risk factors for ON can be divided into direct and indirect causes (see
Table 2).
4. The pathophysiology of ON has yet to be completely elucidated.
5. Osteonecrosis of the hip occurs bilaterally in 80% of patients, so the contralateral hip should be evaluated even if it is asymptomatic. Early diagnosis may improve the chances for the success of head-preserving surgical procedures such as core decompression or grafting.
6. Multifocal osteonecrosis is defined as disease involving three or more sites (hip, knee, shoulder, ankle).
a. Multifocal osteonecrosis occurs in 3% of patients diagnosed with osteonecrosis; therefore, evaluation of all painful joints is important in patients with osteonecrosis.
[Table 2. Risk Factors Associated with Osteonecrosis of the Femoral Head]
b. Patients who present with osteonecrosis at a site other than the hips should have an MRI of the hips to rule out an asymptomatic lesion in the femoral head.
B. Imaging
1. MRI is 99% sensitive and 99% specific for ON.
2. Focal increases in signal on T2-weighted images or the presence of a low-intensity band on T1-weighted images are pathognomonic radiographic findings in osteonecrosis.
3. Transient osteoporosis must be differentiated from osteonecrosis because surgical treatment is not necessary for transient osteoporosis.
a. Transient osteoporosis has a similar appearance on MRI to bone edema, with increased signal on T2-weighted images and decreased signal on T1-weighted images (
Figure 3). The signal changes often involve the femoral head, with extension into the femoral neck.
b. Transient osteoporosis lacks the double density appearance typical of osteonecrosis.
C. Principles of treatment
1. Factors important in determining treatment
a. Presence of symptoms
b. Presence of collapse
c. Size of the lesion
d. Degree of involvement of weight-bearing surface
e. Acetabular involvement
[Figure 3. A 45-year-old man presented with left hip pain persisting for 10 weeks; the final diagnosis was transient osteoporosis of the hip. A, Coronal T1-weighted magnetic resonance imaging (MRI) scan demonstrating an area of low signal intensity (long arrow) extending down to the intertrochanteric area. Spared normal marrow is seen medially (short arrow). B, Axial fat-suppressed T2-weighted fast spin-echo MRI scan demonstrating high signal intensity in the involved area (arrow), moderate joint effusion (thin arrow), and normal marrow (short arrow). C, Coronal short tau inversion recovery MRI scan demonstrating high-signal-intensity edematous marrow lesion (arrow) and joint effusion (thin arrow). D, Oblique axial fat-suppressed contrast-enhanced MRI scan demonstrating enhancement of the marrow edema (white arrow), synovitis (thin white arrow), and a thin subchondral low-signal-intensity structure in keeping with an insufficiency fracture (black arrow).]
2. Medical treatment of early-stage disease with bisphosphonates has been described but remains investigational and is not uniformly successful.
3. Collapse of the femoral head is associated with worse outcomes for all head-preserving treatment options.
4. Smaller lesions with sclerotic borders typically have a better prognosis for bone-preserving procedures.
5. Evidence of acetabular cartilage damage or pain resistant to medical management is an indication for THA.
6. The surgical treatment of asymptomatic disease is controversial.
D. Treatment
1. Head-preserving procedures for osteonecrosis of the femoral head
a. Core decompression
i. Core decompression represents a family of procedures that include drilling a single large hole or multiple holes in the femoral head. This procedure may also include debridement of the lesion and bone grafting.
ii. Core decompression has traditionally been performed with an 8- to 10-mm cannula with or without bone graft; however, multiple small drill holes have also been shown to be effective. Recently, a technique including 2 or 3 passes of a 3.2-mm pin into the lesion has been shown to be effective in early stages of disease.
b. Proximal femoral osteotomy
i. Osteotomies have reported success rates from 60% to 90%.
ii. Osteotomy is less popular in the United States because it causes distortion of the proximal femur, which can make future THA more challenging.
c. Nonvascularized or vascularized fibular graft
i. Vascularized fibular grafts are technically challenging procedures, but several centers have shown good results (80% success) at 5-to 10-year follow-up.
ii. Nonvascularized grafts are easier to perform, but they appear to be less effective for later stages of disease.
iii. Both vascular and nonvascular grafting procedures include excavation of the necrotic lesion and are really variants of core decompression.
2. Arthroplasty procedures
a. Conventional hemiarthroplasty of the hip with a unipolar or bipolar prosthesis
i. This technique has the same problem of unpredictable results as is reported with hemiresurfacing.
ii. The concern for component loosening is diminshed because of the presence of the stem, which confers a larger surface area for fixation.
iii. This technique spares acetabular bone in comparison to THA because the acetabulum is not replaced.
b. Resurfacing hemiarthroplasty
i. Resurfacing hemiarthroplasty requires adequate available bone to support the femoral head resurfacing component.
ii. Reports on medium-term follow-up have indicated problems with acetabular erosion and pain.
iii. Femoral component loosening is rare.
c. Total hip arthroplasty
i. THA provides more predictatable pain relief than hemiarthroplasty options.
ii. Studies report higher rates of loosening and osteolysis than THA for other diagnoses.
iii. Results may improve with modern, alternative bearing surfaces.
d. Resurfacing arthroplasty
i. Resurfacing arthroplasty involves both acetabular and femoral resurfacing.
ii. The management of osteonecrosis with resurfacing arthroplasty is somewhat controversial. The results are influenced by the extent of necrosis and cyst formation in the femoral head and the quality of bone stock in the femoral neck.
iii. Good midterm results have been reported in select patients.
V. Impact of Comorbidities
A. Neuromuscular diseases
1. Parkinson's disease
a. Parkinson's disease was originally considered an absolute contraindication to TKA because of failed rehabilitation due to hamstring rigidity, flexion contracture, and inhibition of the extensor mechanism, but several studies have shown that hip and knee replacements can be successful at improving function and relieving pain in these patients.
b. Function after THA or TKA appears to be related to the stage of the neurologic disease.
2. Neuropathic arthropathy (Charcot arthropathy secondary to diabetes mellitus, neurosyphilis, central cord syndromes)
a. Historically, Charcot arthropathy was considered a contraindication to TKA, but good results can be obtained with careful limb alignment, reinforcement of bone defects, and the use of stems and constrained devices to treat joint subluxation.
b. Complication rates are higher than in patients with other diagnoses.
c. The outcome of joint arthroplasty in patients with neuropathic arthropathy secondary to neurosyphilis appears to be worse than in patients with neuropathic arthropathy secondary to diabetes.
B. Obesity
1. The relationship between BMI of 30-40 and long-term survivorship is less clear in the literature.
2. Obesity increases the chance of infection due to mechanical wound problems related to thick layers of subcutaneous fat and concomitant diabetes.
3. Some reports suggest that obesity may increase the chance of aseptic loosening in THAs and TKAs.
4. A BMI >32 has been shown to lead to early failure of unicompartmental knee arthroplasty.
5. In general, studies focusing on weight change after surgery show that patients remain obese after joint arthroplasty.
VI. Thromboembolic Disease
A. Epidemiology
1. THA and TKA are associated with a risk of symptomatic venous thromboembolism (VTE), which includes deep venous thrombosis (DVT) and pulmonary embolism (PE)
2. The prevalence of fatal PE after THA or TKA is 0% to 0.32%, and the prevalence of symptomatic PE is ~ 1%.
B. Prophylaxis
1. There is general agreement that prophylaxis is required, but the range of appropriate regimens remains controversial with some lack of consistency between recommendations by the American College of Chest Physicians, the American Academy of Orthopaedic Surgeons, and real-world practice patterns.
2. The selection of a prophylactic agent involves a balance between safety and efficacy.
3. Several pharmacologic and mechanical agents have been shown to be effective for the prevention of VTE in THA and TKA patients:
a. Warfarin
b. Low-molecular-weight heparin
c. Fondaparinux
d. Mechanical compression
i. Pneumatic compression has been shown to be effective in limiting clot formation after total knee arthroplasty.
ii. At present, mechanical devices are recommended as adjunctive devices after total hip arthroplasty.
e. Aspirin
i. The use of aspirin remains controversial, but data suggest that it may limit development of symptomatic PE.
ii. It may not be as effective in THA as the other agents unless it is combined with compression devices. Further study of the efficacy of aspirin is needed in both hip and knee arthroplasty patients.
|
3. |
The ideal duration of therapy has not been established. The median time to diagnosis of DVT was 17 days in THAs and 7 days in TKAs. Prophylaxis should be continued for a minimum of 10 to 14 days beyond hospital discharge. Data suggest that prolonged prophylaxis (up to 35 days) may limit symptomatic events in THA patients. In contrast, there is only limited evidence to suggest that prolonged prophylaxis (beyond 2 weeks) is beneficial for TKA patients. |
|
4. |
Inheritable thrombophilia a. Antithrombin III deficiency, protein C deficiency, and prothrombin 20210A gene mutation appear to increase the chance of VTE in total joint arthroplasty patients. b. Factor V Leiden and methylene tetrahydrofolate reductase mutations do not appear to increase the chance of VTE. c. Identification of specific genetic risk factors for VTE is needed. |
Top Testing Facts
1. Evidence is emerging that subtle morphologic abnormalities around the hip that result in femoroacetabular impingement may be a contributing factor to hip OA in young patients.
2. THA is preferred over hemiarthroplasty in conditions such as RA and systemic lupus erythematosus because of involvement of the entire joint and cartilage damage.
3. A difference of >9 to 10 mm in the atlantodens interval on flexion/extension views or space available for the cord of <14 mm is associated with an increased risk of neurologic injury and usually requires surgical treatment.
4. Osteochondritis dissecans is more common on the lateral aspect of the medial femoral condyle in adolescent (15- to 20-year-old) males.
5. With osteonecrosis of the hip, a double density sign is commonly seen on MRI, caused by the advancing edge of neovascularization and new bone formation.
6. Early diagnosis of femoral head osteonecrosis may improve the chances of the success of head-preserving surgical procedures such as core decompression or bone grafting. The best prognosis is with small lesions with sclerotic margins.
7. Collapse of the femoral head is associated with worse outcomes for all head-preserving treatment options.
8. Obese patients are at increased risk for various complications in the perioperative period.
9. DVT prophylaxis is required after THA and TKA. The selection of a prophylactic agent involves a balance between efficacy and safety.
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