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Orthopaedic

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Infection

Question
63 out of 65
 

Tuberculosis of spine best diagnostic modality is



A Clinical

B X-ray

C MRI

D CT guided biopsy

Ans. D

CT guided biopsy

One fifth of TB population is in India.

a. Three percent are suffering from skeletal TB.

b. Vertebral TB is the most common form of skeletal TB and accounts for 50% of all cases of skeletal TB.

c. Almost 50% are from pediatric group.

d. Every day 1000 die of tuberculosis in India.

e. Neurological complications are the most crippling complications of spinal TB ( Incidence : 10 to 43%).

Spinal tuberculosis diagnosis

History

a. Presentation depends on Stage of disease,Site

b. Presence of complications such as neurologic deficits, abscesses, or sinus tracts.

c. Average duration of symptoms at the time of diagnosis is 3 – 4 months. Back pain is the earliest and most common symptom.

Physical examination of the spine:

i. Localised tenderness and paravertebral muscle spasm,

ii. Kyphotic deformity,

iii. Cold abscess swelling/sinus tract

Lab Studies

a. Mantoux/Tuberculin skin test (purified protein derivative {PPD}) A positive test can be observed, one to 3 months after infection. Positive in 84 – 95 % of patients who are HIV negative

b. Negative in almost 20 per cent patients with active disease if the disease is disseminated, or if the patient is immunocompromised or suffering from exanthematous fever.

c. ESR may be markedly elevated (neither specific nor reliable).

d. ELISA: for antibody to mycobacterial antigen-6 , sensitivity of 60 – 80%.

e. IFN – Release assays (IGRAs)

f. Recently, two in vitro assays that measure T-cell releaseof IFN–in response tostimulation with the highly specific tuberculosis antigens ESAT- 6 and CFP-10 have become commercially available.

Radiological Diagnosis

a. Plain Radiograph

b. CT SCAN

c. MRI SPINE

d. BON SCAN

TB bacilli are rarely found in CSF, therefore imaging plays pivotal role in suggesting the diagnosis.

Plain Radiograph

Patterns of Vertebral Involvement

1. Fourpatterns:

a. Paradiscal (Commonest)

b. Central

c. Anterior, and

d. Appendiceal/ poslenor (RAREST)

i. More than 50% of bone has to be destroyed before a lesion can be seen on X-ray. This process takes approximately six months.

ii. The classic roentgen triad in spinal tuberculosis is primary vertebral lesion, disc space narrowing and paravertebral abscess.

iii. Typical tubercular spondylitic features in long standing paraspinal abscesses = produce concave erosions around the anterior margins of the vertebral bodies producing a scalloped appearance called the Aneurysmal phenomenon.

iv. fusiform paraspinal soft tissue shadow with calcification in few .( Skip lesions as involvement of non-contiguous vertebrae (7 – 10 % cases).

CT Scan

a. Patterns of bony destruction.

b. Calcifications in abscess (pathognomic for Tb)

c. Regions which are difficult to visualize on plain films, like :

i. Cranio-vertebraljunction(CVJ)

ii. Cervico-dorsal region,

iii. Sacrum

iv. Sacro-iliacjoints.

d. Posterior spinal tuberculosis because lesions less than 1.5cm are usually missed due to overlapping of shadows on x rays.

MRI

a. Lack of ionizing radiation, high contrast resolution and 3D imaging.

b. Detect marrow infiltration in vertebral bodies, leading to early diagnosis.

c. Changes of discitis

d. Assessment of extradural abscesses/subligamentous spread.

e. Skip lesions

f. Spinal cord involvement.

g. Spinalarachanoiditis.

h. MRI is the modality of choice as delineates leptomeningeal disease better, direct evaluation of intramedullary lesions, associated osseous signal change and epidural abscesses.

i. Typical (spondylo-discitis) and atypical (spondylitis without discitis) types.

Spinal Tuberculosis- Paradiscal Lesions:

a. Most common pattern of spinal tuberculosis.

b. It is adjacent to the I/V disc leading to a narrowing of the disc space.

c. Disk space narrowing is caused either by destruction of subchondral bone with subsequent herniation of the disc into the vertebral body or by direct involvement of the disc.

d. MR imaging shows low signal on T1-weighted images and high signal on T2-weighted images in the endplate, narrowing of the disc, and large paraspinal and sometimes epidural abscesses.




Spinal Tuberculosis


Paradiscal Lesions

Spinal Tuberculosis Confirmatory Diagnosis

Microbiology studies are used to confirm diagnosis:

a. Ziehl-Neelsen staining a quick and inexpensive method.

b. Obtain bone tissue or abscess samples to stain for acid-fast bacilli (AFB), and isolate organisms for culture and drug susceptibility this is considered the gold standard and now a days performed by CT guided biopsy.

c. Pcr for the material is routinely performed as the lesions are paucibacillary.

d. Culture results are available only after a few weeks andPositive only in 50% of cases.

Infection Flashcard List

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