3.4.1. Spinal/vertebral disease
Spinal or vertebral TB (Pott’s disease) involvement is noted in approximately 50% of bone and joint TB cases.52,153–155
Most patients present with slowly progressive back pain.156–157 Fever and constitutional symptoms are not common unless there is concurrent extraspinal or disseminated disease. Given nonspecific complaints, the diagnosis of spinal TB usually is not made until several months after the beginning of symptoms.72,73,80,154,155,156–162 Radiographic findings include loss of vertebral body height and scalloping of vertebral bodies by paraspinous fluid collections; however, these findings are insensitive.163 CT and magnetic resonance imaging (MRI) imaging are more sensitive for detection of vertebral and soft-tissue abnormalities associated with spinal TB.163 Findings include anterior vertebral involvement of thoracic or lumbar vertebrae adjacent to the endplate with evidence of marrow edema with minimal sclerosis; discitis of intervening disks with preservation of the disk until late in disease; and large paraspinal abscesses (calcification being suggestive of TB). MRI is the modality of choice for assessing spinal cord involvement or damage.80,159,160,163–168
CT-guided needle biopsy of vertebrae and/or aspiration of paraspinal fluid collections have the highest diagnostic yield, outside of surgery, and are the recommended initial diagnostic sampling method (Table 1).23,72,73,77If CT guided sampling cannot be performed or is nondiagnostic, a surgical biopsy can be obtained for definitive diagnosis and to assess for etiologies other than TB osteomyelitis.23,50,72,78,169–174 It is important to assess the patient for other manifestations of TB disease, as studies have demonstrated that one-third of patients with spinal TB had evidence of TB elsewhere, and the diagnosis of TB disease was made in one-quarter of patients by obtaining nonspinal specimens.73
3.4.2. Joint TB (TB arthritis)
Joint TB is usually a mono-arthritis affecting large, weight-bearing joints such as the hip or knee. Symptoms can include swelling, pain and loss of function. Focal signs typically associated with septic arthritis, such as local erythema and warmth, are often missing, as are constitutional symptoms. Cartilage erosion, deformity and draining sinuses have been associated with late presentation. M. tuberculosis has also been associated with prosthetic joint infections. Osteomyelitis affecting other sites in the skeleton is uncommon but has been described.52,175–178 Multifocal presentations can occur in 15% to 20% of cases, often in immune-suppressed individuals, and can be misinterpreted as metastases or inflammatory arthritis.74,179
Radiologic findings suggestive of joint TB include synovial thickening and joint effusion, however differentiation from other arthritic conditions can be difficult. MRI changes suggestive of joint TB include moderate but uniform thickening of the synovium, as compared with the larger and irregular thickening seen in rheumatoid arthritis. Adjacent fasciitis and cellulitis can be seen in both TB and pyogenic arthritis but are more indicative of a pyogenic arthritis.153,164,177–181
Synovial fluid aspirate is a reasonable first step in obtaining a diagnosis of joint TB.79,153,178,182 Typical synovial fluid findings are that of an elevated white blood cell count (WBC) (10,000 to 20,000 WBC per ml with neutrophil predominance), decreased glucose (less than 2.2 mmol per L) and elevated protein (greater than 25 g per L).79,153,157,178 The yield of synovial-fluid AFB smear is low (19%); however, NAAT and mycobacterial culture synovial-fluid sensitivity is relatively high at 75 to 85%.23,50,51,74,75,79,153,178,182 Synovial biopsy with sampling for NAAT, mycobacterial smear and culture, as well as histopathology, has high diagnostic yield (94%) and should be obtained if joint TB is still a diagnostic consideration and synovial fluid mycobacteriology assessment is negative (Table 1).23,50,51,74,75,79,153,178,182
3.4.3. Bone and joint TB treatment
In a review of bone and joint TB treatment with isoniazid (INH) and rifampin (RMP) anti-TB therapy for individuals with drug-susceptible TB (majority of studies were observational cohort in adults and children), a risk of relapse was 1.35% with 6 months of anti-TB therapy (539 individuals studied), 0.86% with 6-12 months of anti-TB therapy (437 individuals studied) and 0.51% with greater than 12 months of anti-TB therapy (1,386 individuals studied).183 Similar outcomes were identified in 2 small randomized controlled trials.184–186
Increased risk of failure/relapse has been associated with extensive disease at the outset of treatment (radiographically defined or with evidence of smear positivity at beginning of therapy), evidence of sclerotic bony disease on imaging, and Erythrocyte sedimentation rate (ESR)/C-reactive protein (CRP) (both measures of inflammatory response) elevation at end of treatment.162,183 The definition of cure is difficult in bone and joint TB, and follow-up samples are infrequently obtained to demonstrate lack of mycobacterial growth. Alternative definitions of cure have utilized radiologic markers; however, vertebral x-rays may never return to baseline and studies in spinal TB have shown that 50% of patients will have MRI evidence of TB activity even at the end of 12 months of treatment.165,168,187 Studies utilizing vertebral CT positron emission tomography (PET) imaging have suggested decrease in PET activity may predict when TB treatment for spinal TB can be safely discontinued, but there is not enough evidence to recommend currently.188 Routine surgery for bone and joint TB is not required to achieve cure, but should be considered to treat complications of vertebral TB (neurologic compromise) and joint disease (pain and immobility).161,185,189
We conditionally recommend 6 months of standard anti-TB therapy for individuals with drug-susceptible bone and joint TB with extension to 9-12 months in individuals with markers of increased risk of failure/relapse; diagnostic biopsy sample smear positive for acid-fast bacilli and/or elevated erythrocyte sedimentation rate/C-reactive protein (ESR/CRP) at planned end of treatment (poor evidence).
We conditionally recommend against routine surgical intervention as part of treatment in spinal TB. Surgical treatment of spinal TB should be considered in those with progressive neurologic deterioration and in those less than 15 years of age with significant kyphosis (poor evidence).
We conditionally recommend against routine surgical intervention as part of treatment in joint TB. Surgical treatment should be considered to prevent extension of disease and to provide relief of pain and immobility after control of infection is established (poor evidence).
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