Chapter 23 Tuberculosis and Other Unusual Infections
Tuberculosis is transmitted primarily through inhalation or ingestion of Mycobacterium tuberculosis or Mycobacterium bovis. After exposure, the infection may be cleared by the host, lead to a primary infection, or can later be reactivated from a latent infection. Thereafter, lymphogenous, hematogenous, or contiguous extension to other tissues and organ systems may occur. The clinical presentation depends on the presence of isolated musculoskeletal involvement or miliary disease. Miliary disease has a rapid course, and constitutional symptoms include fever, chills, and cough, with accompanying pleuritic pain, weight loss, and fatigue. The patient may have acute or chronic symptoms.
Current estimates of the worldwide rate of tuberculosis infection are as high as one third of the world’s population. Tuberculosis remains one of the most frequent causes of death worldwide; the World Health Organization reported 1.3 million deaths in 2008. The highest rate of new cases is in Southeast Asia, but the highest rates of infection and mortality are in sub-Saharan Africa.
According the Centers for Disease Control and Prevention, there were 12,904 new cases of tuberculosis reported in the United States in 2008. Since 1992, there has been a decrease in the rate of cases in the United States. There were 644 deaths in the United States attributed to tuberculosis in 2006.
Populations most at risk include individuals with acquired immunodeficiency syndrome (AIDS) or other immunodeficiencies, patients with chronic renal failure, substance abusers, homeless or incarcerated individuals, and immigrants from developing countries. Foreign-born individuals accounted for 59% of recent tuberculosis cases in the United States. The high-risk period for developing the disease is within the first 5 years of immigration. Population density continues to be a risk factor; 75% of newly reported cases occur in metropolitan areas with a population of more than 500,000.
Tuberculosis commonly affects the pulmonary system but can affect virtually any organ system of the body. Extrapulmonary involvement is noted in approximately 14% of patients, with 1% to 8% having osseous disease. Approximately 50% of patients with osseous tuberculosis have pulmonary involvement, and 30% to 50% of patients with osseous disease have vertebral involvement, most often in the lower thoracic spine. Frequently, a primary extraosseous lesion is not well delineated. Less frequently observed appendicular involvement usually affects major weight-bearing joints of the lower extremity, most commonly the hip and knee, followed in frequency by the foot, elbow, and hand. Virtually any other bone or joint can be involved. Soft tissue abscesses with sinus tracks have been described, as has tenosynovitis.
The spine is the most common (30% to 50%) site of osseous involvement, especially in elderly individuals; however, spinal involvement also is common in children and in young adults from developing countries. A primary accompanying lesion may be discovered from the pulmonary or urogenital system or from an unknown source. Lymphogenous and hematogenous spread have been implicated in thoracolumbar lesions but less often in cervical or sacral lesions. Usually, active spinal lesions involve a particular segment: two vertebral bodies and the corresponding disc. Some authors have speculated that these areas are affected most often because of the generous arterial and venous supply and the high oxygen pressure requirement of the tuberculosis bacilli. A peridiscal presentation occurs in approximately 80% of patients, with the anterior vertebral body affected and contiguous progression through subligamentous burrowing (anterior longitudinal ligament) and eventual extension to the adjacent vertebrae. Less frequently, lesions occur centrally in the vertebral body. These lesions are more difficult to diagnose and may mimic a tumor or contribute to significant spinal deformities. Patients may have intramedullary granulomas, arachnoiditis, segmental collapse with anterior wedging, and gibbus formation (Pott disease). The posterior elements of the spine are rarely the only sites affected. Perispinal abscesses with sinus extension to the skin also may arise and extend through tissue planes to reach intraperitoneal structures. They have been reported to occur as far distally as the popliteal fossa. Patients present with pain, weakness, and, in the late stages, paralysis.
Appendicular joint involvement typically affects the major weight-bearing joints of the lower extremities. Lesions involve the articular cartilage, which eventually is separated by granulomatous tissue. The trabecular zones of the bone are affected, with subchondral involvement affecting the weight-bearing capability of the joint, which may progress to significant accelerated joint surface degeneration. Pathological assessment reveals a central caseating lesion within necrotic tissue and multinucleated giant cells.
Other, less frequently involved joints include the ankle, foot, and upper extremity joints. Patients may present with a limp and a joint that is warm and swollen and has a decreased range of motion. Tuberculosis in a joint markedly decreases its functional use; even when adequately treated, the disease may reactivate in isolated regions. Peripheral joint involvement from tuberculosis can be confused with other rheumatological conditions (e.g., gout and rheumatoid arthritis).
Patients may have a normochromic or normocytic anemia, pancytopenia, or thrombocytopenia. Frequently, the white blood cell count is normal and the sedimentation rate may be elevated or normal. The patient may have the syndrome of inappropriate antidiuretic hormone. Tuberculosis skin testing usually is effective in diagnosing this condition; however, false-negative rates can be 20% to 30%. Immunocompromised individuals frequently have an unreliable skin test result. The hallmark of the diagnosis is demonstration of the tuberculosis acid-fast bacilli from a tissue or fluid source. Bone cultures taken from disc involvement are positive in 60% to 80% of cases. Sputum and gastric cultures of patients with pulmonary involvement usually are positive in more than 50%.
Transbronchial biopsy specimens in patients with pulmonary involvement are positive in 70% to 86% of patients. Pulmonary exudates may reveal predominantly leukocytes or polymorphonuclear leukocytes and have a low pH that is slightly to moderately acidic. Molecular subtyping also has been used to assess infection patterns and sensitivities to medications.
Plain radiographs of involved joints assist in guiding treatment. When a joint is involved, synovial infiltration that affects the subarticular bone usually is present. Periarticular erosions observed radiographically have an almost lytic appearance and can mimic infection, noninfectious arthropathy, or malignancy. Periarticular bone mass is decreased and may mimic juvenile arthritis. Progression to fusion is rare but can occur. Characteristics of typical spinal involvement have been described previously. Anterior vertebral involvement occurs more commonly than central vertebral involvement. There is a relative sparing of the intervertebral disc space. Later stages include a focal segmental collapse with anterior wedging and gibbus formation, characteristic of Pott disease.
Other imaging studies include a bone scan or a gallium scan, which can detect 88% to 96% of osseous tuberculosis lesions. Such scans are quite sensitive but not particularly specific for tuberculosis. MRI and CT also can provide more detail and delineate the disease in earlier phases. MRI and CT are helpful in defining soft tissue abscesses. Calcifications (best seen on CT) within paraspinous abscesses indicate bone destruction and are characteristic of spinal tuberculosis. CT or ultrasound-guided fluoroscopy can assist in obtaining appropriate tissue or fluid samples for additional studies. Arthrography and other imaging studies for tendon sheaths have been described but are used less frequently.
The primary treatment objectives for tuberculosis of bone include halting the infection, limiting deformity, maintaining mobility, and reducing discomfort. A multidisciplinary approach with the assistance of infectious disease and pain management specialists is ideal. Other affiliated team members should include nurses, physical therapists, occupational therapists, and orthotists. Approximately 90% of patients can be treated conservatively with chemotherapy, relative rest, and guided remobilization. Adjunctive splinting (passive, dynamic, functional) and casting techniques are useful for marked or painful and progressive joint involvement. At times, destructive changes are markedly progressive and eventually may lead to fusion of the joint (e.g., elbow), so it is crucial to place the extremity in a position of function (elbow flexion 70 to 90 degrees) to obtain an optimal range for future functional use.
A judicious, well-guided chemotherapeutic approach to tuberculosis along with the assistance of an infectious disease specialist yields optimal results. The pharmacological agents and duration of treatment depend on the patient’s age, dissemination of disease, and accompanying medical conditions (e.g., AIDS, chronic renal failure). Several agents interact with medications typically used for immunosuppressed individuals, especially patients infected with human immunodeficiency virus (HIV). In these patients it may be necessary to adjust dosages and modify treatment regimens. Various combinations of medications are available, including isoniazid, rifamycin, ethambutol, pyrazinamide, and streptomycin. The typical approach consists of the use of a wide variety of combinations with an intensive initial treatment regimen and a gradual phasing out of pharmacological agents. Treatment duration can last 6 to 12 months. Because treatment for tuberculosis frequently is modified, readily available guidelines from the Centers for Disease Control and Prevention should be consulted. Although primary and secondary resistance to multiple medications has been reported, especially in countries outside the United States, most are isolated cases. Generally, only a small percentage of patients (<3%) are resistant to multiple chemotherapeutic agents.
Treatment should not be limited to the patient, but chemoprophylaxis should be considered in family members and other close contacts who have a positive tuberculosis skin test. Chemoprophylaxis is particularly important in individuals who are younger than age 50 to 55 years. Older individuals may not tolerate some of the medications typically used for prophylaxis. Treatment for chemoprophylaxis may last 3 to 12 months, depending on the conversion of the tuberculosis skin test.
Patients may require analgesics for pain. In severe cases, a pain management specialist should be consulted. Although the use of systemic corticosteroids to reduce symptoms in severe cases has been described, their use may mask a septic joint, and intraarticular corticosteroid injections can accelerate the destructive articular changes.
Operations applicable to bone and joint tuberculosis include (1) arthrotomy, including biopsy, synovectomy, and curettage with bone grafting of articular erosions; (2) curettage and bone grafting of extraarticular skeletal lesions; (3) resection of joints; (4) resection of bones; (5) evacuation or excision of soft tissue abscesses; (6) arthrodesis; and (7) amputation. There have been reports of arthroscopic treatment of joint tuberculosis, but these series have been small. The best success has occurred in the knee with the use of arthroscopic débridement.
Most authorities agree that effective antibiotic therapy should be started before surgery for tuberculosis. Miliary dissemination of the disease has been reported when surgery was done without adequate chemotherapeutic coverage.
In tuberculosis of the foot (Fig. 23-1), many bones may become involved, and a delay in diagnosis increases the risk of joint involvement. Operative indications include juxtaarticular focus or joint destruction. Bones with cystic changes typically respond better than rheumatological-appearing joints. When present, isolated lesions usually involve the calcaneus or talus. When several bones are involved, especially in adults, amputation is the procedure of choice. Curettage is indicated for isolated lesions even when sinuses are present.
FIGURE 23-1 A and B, Anteroposterior and oblique radiographs of tuberculous lesion involving base of first metatarsal. Medial and lateral cortices are eroded. C, MR image shows circumferential destruction of base of first metatarsal with extension into soft tissues.
(From Lonner JH, Sheskier SC: Tuberculosis of the foot as the initial manifestation of acquired immune deficiency syndrome: a report of two cases, Foot Ankle Int 16:167, 1995.)
FIGURE 23-2 Tuberculosis of calcaneus before (A) and 6 months after (B) curettage, grafting with cancellous bone chips, and primary closure of wound. The calcaneus healed without drainage, an excellent result.
When lesions involve the subtalar or midtarsal joints, a triple arthrodesis is indicated (see Chapter 34). When the subtalar and the ankle joints are affected, posterior arthrodesis (see Chapter 11) of these joints can be done.
When the disease is extensive, especially when complicated by sinuses or secondary infection, excision of bones or amputation is indicated. Involvement of a phalanx or metatarsal often is best treated by excision. When a tarsal bone is excised, a proportionate amount of bone is taken from the opposite side of the foot so that proper alignment can be maintained.
When a metatarsal is excised, amputation of the corresponding toe permits better approximation of adjacent metatarsals and provides a foot with a better appearance and function. Excision of the first metatarsal should be avoided if possible.
Begin a Kocher incision (see Technique 1-19) 10 cm proximal to the lateral malleolus, and follow the lateral border of the Achilles tendon to the superior surface of the calcaneus; continue it inferiorly to the lateral malleolus, and end it 2.5 cm distal to the calcaneocuboid joint.
A long-leg cast is applied with the knee in 30 degrees of flexion and the ankle in moderate equinus. At 3 weeks the cast is changed to a short-leg cast, and the foot is maintained in mild equinus. Protective weight bearing is begun at 8 weeks, and cast immobilization is continued for 4 months. A shoe insert with heel elevation is required later.
Grasp the neck of the talus and apply slight traction; use sharp subperiosteal dissection to sever all soft tissues and ligamentous attachments on the posterior and inferior aspects from anteriorly to posteriorly, and remove the talus. If the bone is necrotic, it must be removed in pieces.
A long-leg cast is applied with the knee in 30 degrees of flexion and the ankle in moderate equinus. A window is removed from the cast on the dorsum of the foot and ankle and is loosely replaced. At 2 or 3 weeks the cast is changed to a short-leg cast, and the foot is maintained in equinus. Protective weight bearing is begun at 8 weeks, and cast immobilization is continued for 4 months. A comfortable shoe with heel elevation is fitted.