Musculoskeletal tuberculosis refers to tuberculosis involvement of the bones and/or joints. Musculoskeletal tuberculosis forms around 1-4% of all cases of tuberculosis.
It is quite an old disease. Spine tuberculosis has been identified in Egyptian mummies dating back 9000 years.
The first notable description was made by Sir Percivall Pott who described tuberculous spondylitis in 1779.
Other names for musculoskeletal tuberculosis are
- Skeletal tuberculosis
- Tuberculosis of bone and joints
- osteoarticular tuberculosis
It is also communicated as bone TB amongst the general population.
Skeletal tuberculosis is found more in children, adolescents, and young adults, than in the elderly.
The diagnosis could be quite challenging and require a high index of suspicion, as it can appear similar to other diseases and infective processes.
The spine is the most common site of involvement in musculoskeletal tuberculosis, followed by the hip and knee.
In the spine, the usual involvement is vertebral bodies and intervertebral discs in the dorsolumbar regions.
After the dorsolumbar spine following regions are affected commonly.
- Cervical vertebrae
- Craniovertebral junction
- Sacrum and sacroiliac joints
- Ribs
- Pelvic bones
- Small bones of the foot
- Long bones
- Sternoclavicular joint
- Sternum
- Bursae
Sometimes, more than one site may be affected by musculoskeletal TB in the same patients and is termed multifocal skeletal tuberculosis.
The peaks of occurrence have been found to be in the first, third, and sixth decade of life.
Predisposing Factors
The following are the main predisposing factors for musculoskeletal tuberculosis
- Malnutrition
- Endemicity of the disease
- Poor sanitation [as in slums]
- Overcrowded housing
- Acquired immunodeficiency syndrome
Pathology and Spread of Musculoskeletal Tuberculosis
Mycobacterium tuberculosis is the most common causative organism although atypical mycobacteria have been reported in lesions of the synovial sheath. The infection in musculoskeletal organs is always secondary to another focus, usually in the lungs or in the mediastinal lymph nodes.
The organisms spread through the bloodstream and settle in the bone usually near the epiphyseal cartilage in proximity to the synovial membrane. As they proliferate, they form ‘tubercle’, the microscopic pathological lesion with central necrosis surrounded by epithelioid cells, giant cells, and mononuclear cells.
Two types of microscopic lesions of musculoskeletal tuberculosis are known
- Caseating exudative type – caseating necrosis and cold abscess formation
- Proliferating type – cellular proliferation with minimal caseation e.g the tuberculous granuloma
The type of lesion formed would depend on how does the body deal with bacteria or the immunity of the person.
Infection in bone and synovial tissue is secondary. The initial infection occurs in the lung (human type) or the intestine (bovine type).
Typically, an active focus is set up in a metaphysis (in a child) or in an epiphysis (in an adult), where the acute exudative reaction may cause local necrosis until caseation occurs.
There is an increase in blood circulation [hyperemia] following the inflammation. The intense hyperemia causes marked decalcification locally and are visible on x-ray as local osteoporosis.
The periosteum may react to a superficial cortical lesion by producing new periosteal bone. The exudates may penetrate outward through the soft tissue to exit through the skin as a sinus that chronically drains caseous material, particles of bone, and partially liquefied, thick, grayish-yellow substance.
Cartilage is resistant to tuberculous destruction. Therefore, the epiphyseal plate is not destroyed. However, the granulation tissue may invade the area of calcified cartilage and interfere with longitudinal growth in children.
The infected synovium may be swollen and congested with granulation tissue. The articular surface is studded with many translucent tubercles There are deposits of fibrin covering many areas.
The joint fluid usually is moderately increased and clear. It contains rice bodies, which are small accumulations of fibrin, and pieces of articular cartilage.
Caseation necrosis of the synovium and the capsule is rare.
Abscesses in the soft tissues have a tendency to migrate along fascial planes and erupt at a distance from the original focus. This is seen best in the spine, where the infective material may enter the fascia enveloping the psoas muscle and erupt at the groin. [cold abscess]
The areas of predilection occur in the following order of frequency are
- Spine
- Hip
- Knee
- Ankle
- Tarsus or foot
- Shoulder
- Elbow.
Symptoms and Signs of Musculoskseltal Tuberculosis
The musculoskeletal tuberculosis begins often with insidious onset of symptoms. Often patients ignore it or confuse it with some other ailments.
Therefore, the diagnosis is often delayed. The condition also poses diagnostic challenges because of the following uncertain histories and often, a lack of lung involvement that could be used to aid in diagnosis.
The patient with skeletal tuberculosis presents with one or more of these symptoms. The symptoms may vary as per the site
- Back pain
- Mass on back/neck [cold abscess]
- Pain in joint
- Swelling of the joint
- Limping
- Spine deformity
- Hip or knee deformity
- Joint stiffness
- Neurological deficit
- Muscle spasms
- Discharging sinus
Constitutional symptoms like low-grade fevers, night sweats, weight loss, and malaise are seen in a few patients only.
Lab Studies
Routine biochemical parameters are often normal.
Montoux Test
Also called tuberculin skin test or purified peptide test, it involves intradermal injection by injecting 0.1 mL of a liquid containing 5 TU (tuberculin units) of PPD.
It tests the presence of an immune response against tuberculosis. The test just tests that and is not necessarily indicative of current infection. False tests can be seen in old infections and after BCG vaccination.
Erythrocyte sedimentation rate
It is a marker of inflammation and is always elevated, Markedly raised values may indicate strong activity of the infection.
PCR for tuberculosis
It is used to confirm the infection at a particular site. The test is done on aspirate from the site and uses amplification technology to confirm the presence of bacteria.
Cytology
The aspirate [eg joint aspirate in case of suspected joint involvement] tissue swabs or abscess samples can be subjected to staining and studied for the cellular reactions that may suggest tuberculosis. The presence of AFB [acid fast bacilli or mycobacterium] is almost confirmatory.
Culture and Sensitivity
The sample can be given for culture to confirm but again not all cases will grow mycobacterium as musculoskeletal tuberculosis is a paucibacillary type mostly [contains few bacteria]. Drug sensitivity will reveal the susceptibility or resistance of the TB bacilli to a particular drug.
Culture takes a very long time and is often not done in endemic areas as the trial of antitubercular drugs can be initiated on clinical, lab works, and radiological observations.
Culture has been reported to be positive in 50-80 percent.
Surgical Biopsy
It is very rarely required and done only when the diagnosis is not certain in spite of exhausting other avenues.
The biopsy can be performed with a needle biopsy. The same tissue can be used for microbiological procedures as well.
Histologically, signs of granuloma with epithelioid cells may suggest tuberculosis.
Imaging in Musculoskeletal Tuberculosis
X-rays
X-ray of the affected part may show the destruction of the involved bone or joint. However, it is inconclusive in soft tissue affections or in cases where the disease is in the early stage and is yet to bring bony changes.
CT
Computerized tomography is helpful in defining the disease further. CT is good for bony lesions but also shows shoft tissue shadows though not as good as MRI.
MRI
MRI is used more frequently than CT for musculoskeletal tuberculosis imaging as it is able to define soft tissue affections better.
MRI helps to catch the disease early before it is evident on x-rays. It may also pick the hidden lesions or lesions like granuloma in the spine. It also helps in assessing complications, assessing response to treatment, and provides better delineation of vertebral lesions with adjoining soft tissue involvement and nerve compressions.
Ultrasound
Ultrasound is helpful in tenosynovitis lesions.
Management of Musculoskeletal Tuberculosis
In medicine, early detection of the disease and treatment are key factors in the successful management of the disease. If musculoskeletal tuberculosis is diagnosed and treated at an early stage, the majority of patients are expected to achieve healing with near-normal function.
The goals of treatment are
- Contain and eradicate the infection
- Relieve pain
- Preserve and restore bone and joint function
- Preserve and restore neurological function (In cases of the spine)
The mainstay of treatment of musculoskeletal tuberculosis is multidrug antitubercular chemotherapy. Apart from this, the following measures are applied.
- Rest
- Traction or splint [whenever required]
- Active or assisted exercises of the involved joint throughout the period of healing
Adequate nutritional support is also essential, as in all forms of tuberculosis.
Antitubercular chemotherapy
Antitubercular chemotherapy is the standard treatment of all tuberculous lesions including musculoskeletal tuberculosis. The drugs for therapy are
- Rifampicin
- Isoniazid
- Ethambutol
- Pyrazinamide
- Streptomycin
Some authors have recommended the use of moxifloxacin as the first line too.
Second-line antitubercular drugs are
- levofloxacin or moxifloxacin
- Linezolid
- Bedaquiline
- Clofazimine
- Cycloserine
- Terizidone
- Delamanid
- Imipenem-cilastatin
- Meropenem
- Amikacin
- Ethionamide
- p-aminosalicylic
The second-line drugs are used when there is drug-resistant or intolerance to first-line drugs.
There had been various regimes of antitubercular drugs in vogue. But with the introduction of DOTS by WHO, most of the physicians follow it.
Rest
Rest is a very important part of musculoskeletal tuberculosis treatment. The rest relieves pain and provides an atmosphere for healing.
The rest to the part can be provided by
- Lying down [spinal tuberculosis]
- Splintage [Posterior knee splint in knee tuberculosis]
- Traction
An initial period of rest is to be followed by supervised gradual mobilization and exercises.
Initial treatment is given under supervision and the patient is hospitalized for that. This is done to take care of the affected part by traction or splint and to train the patient for modified self-care at home.
For example in cases of spinal tuberculosis with neurological deficit patient is advised to rest for 12-16 weeks. The patient needs to stay in bed throughout that time. No sitting or standing is allowed. The patient is allowed and encouraged in bed turn. This needs to be monitored and his response to therapy needs to be monitored failing which he might undergo surgery. This would definitely require hospitalization.
Thus an initial period of hospitalization enables supervised treatment. Continuation treatment can be on a domiciliary basis.
Surgery
Operative intervention is required when the patient with musculoskeletal tuberculosis is not responding to an adequate trial of chemotherapy. Surgery aims at removing the diseased tissue and decreasing the bacterial load so that the response to drugs increases.
This is the basic rationale behind the surgery in the treatment of active musculoskeletal tuberculosis. Depending on the region and extent of the surgery, there might be a need for an additional implant for fixation or traction postoperatively.
Surgery may also be done if the therapeutic outcome is not satisfactory or an unacceptable deformity is left after the treatment. A loss of motion so severe that it hampers the activity of daily living is also an indication for surgery, if feasible.
It is also required for an unstable spine.
References
- Aggarwal AN, Dhammi IK, Jain AK. Multifocal skeletal tuberculosis. Tropical Doctor 2001;31:219–220. [Link]
- 2. Jain AK. Treatment of tuberculosis of the spine with neurologic complications. Clin Orthop Rel Res 2002;398:75–84.
- Tuli SM. Tuberculosis of the Skeletal System: Bones, Joints, Spine and Bursal Sheaths, 3rd ed. Bangalore: Jaypee Brothers, 2004.
- Shah BA, Splain S. Multifocal osteoarticular tuberculosis. Orthopedics. 2005;28(3):329–32.
