|THE EXTRAPULMONARY DISEASE - THE SPINE CLINIC
|Year : 2017 | Volume
| Issue : 2 | Page : 94-99
Tuberculosis of the spine: The current clinical landscape
Kunal Shah, Abhay Nene
Department of Spine Surgery, Wockhardt Hospital, Mumbai, Maharashtra, India
|Date of Web Publication||30-Nov-2017|
Department of Spine Surgery, Wockhardt Hospital, Mumbai, Maharashtra
Source of Support: None, Conflict of Interest: None
Tuberculosis is a major health problem in developing countries, and India is considered endemic for the disease. Tuberculosis of the spine is one of the most common extrapulmonary manifestations. Patients present at various stages of the disease ranging from paraplegia and spinal instability to merely early back pain. Thus, it becomes hard to typeset a plan for the management of spinal tuberculosis, which clearly needs to be individualized. However, a modern philosophy of treatment has emerged based on advanced imaging and diagnostic techniques, improved knowledge of tuberculosis pharmacology, and a better understanding of surgical indications, keeping the new resistant strains of the tuberculous mycobacterium in mind. This article puts forward the modern approach – the “Millennium Doctrine” – towards the diagnosis and treatment of tuberculosis to help in preventing disability and complications.
Keywords: Diagnosis, spinal tuberculosis, surgery
|How to cite this article:|
Shah K, Nene A. Tuberculosis of the spine: The current clinical landscape. Astrocyte 2017;4:94-9
| Introduction|| |
In the late 1980s, the medical fraternity seemed to be on its way to achieving control over tuberculosis (TB), one of the most dreaded infectious diseases of the 20th century. However, a rising worldwide incidence of diabetes mellitus and human immunodeficiency virus (HIV), marked a dramatic comeback by this “millennium bug.” The west, especially UK and North America experienced, a rise in TB cases due to increasing migrants from endemic Asian countries., Despite a general improvement in the awareness of TB, a rising economy, government and nongovernment initiatives to control TB, there has been a rise in cases of spinal TB across the world, crossing the socioeconomic barrier.
The evolution of multidrug-resistant (MDR) and extremely drug resistant (XDR) strains have led to a further increase in the numbers, and a new covert form of TB which can wreck destruction in the spine by the time it is diagnosed and then controlled.
| Clinical Presentation|| |
Modern spinal TB usually presents with the innocuous back pain, often not acute or severe. The classical constitutional symptoms of fever, loss of appetite, and weight loss are often missing, and are certainly not necessary for the diagnosis. A young patient with thoracolumbar back pain not purely of the mechanical type, with night pains and paraspinal muscle spasm on examination should arouse the suspicion of spinal TB in endemic regions. Osteomalacia and spondyloarthropathy are the most likely differentials in a similar clinical setting. In nonendemic countries, however, this presentation is missed, and sometimes magnetic resonance imaging (MRI) scans get delayed till many more clinical features and more advanced destruction of the vertebral column appears. This among others is a reason why many more cases of spinal TB need surgical treatment in the western world, whereas larger numbers get conservatively managed in India, for example.
| Diagnosis|| |
Radiographs of the spine are usually the first investigation in all cases of suspected spinal TB. X-rays miss early lesions and obvious bony destruction may not be apparent for up to 3 months from the time the disease sets in. Hence, in case of strong clinical suspicion, one would be well advised to go ahead with advanced imaging and not be under a false sense of security that the X-ray may offer. The obvious advantage of an X-ray is its low cost and availability. Also, in proven cases, the surgeon often falls back on the X-ray to assess spinal alignment and deformity as X-rays can be done in the vertical/load bearing position as against MRI.
Magnetic resonance imaging (MRI)
MRI is the gold standard in the imaging of TB spine. Availability of MRI is largely responsible for early diagnosis, and hence, early institution of treatment, precluding progression to mechanical instabilities and deformities. MRI also helps assess disease progression on treatment as well as the healed status of the disease. The “whole spine sequence” screens the entire spine for associated lesions. Ever since the widespread use of MRI, the reported incidence of “skip lesions” in spinal TB has increased. Apart from the obvious disadvantage of high costs, MRI has been found to be “over sensitive,” and if not interpreted in the correct perspective, can show false detection
Computed tomography (CT)
CT scan is the imaging modality of choice in occipitocervical lesions and sacroiliac (SI) joint lesions as the MRI defines these areas poorly and often cannot differentiate inflammatory from infective etiology. Moreover, CT scans are useful in defining the extent of the bony destruction when surgical reconstruction is planned in spinal TB. CT scans are also used in some postoperative cases of spinal TB where stainless steel implants have been used because stainless steel produces significant artefacts, which can hamper interpretation of the picture.
Traditionally, spinal TB would be diagnosed in endemic regions such as India on the basis of clinicoradiological judgement. Tissue diagnosis was not considered necessary as this was the most common spinal infection by far. However, with emergence of drug-resistant TB and atypical infections, tissue diagnosis (through biopsy) and culture have become mandatory. Today's state of the art recommendations suggest tissue diagnosis and culture for all suspected cases of spinal TB. A “therapeutic trial” of anti-TB treatment based on radiological and clinical diagnosis is considered legitimate only in a population setting when treating large numbers of patients in groups in a national program.
TB reported on the basis of MRI can turn out to be other non-TB infections, including more sinister lesions such as round cell tumors and other malignancies. Moreover, even if we get the radiological diagnosis right, it does not give any information about the drug sensitivity on the bug – a very important prerequisite to treat TB in today's era of drug resistance.
Biopsy can be performed during surgery or percutaneously. Percutaneous biopsy can be performed under fluoroscopy, CT scan (the modality of choice for guiding biopsy of lesions in the spine), ultrasonography (used for abscesses, lesions on or near the surface of bone, biopsy of cervical spine lesions), and MRI (advocated for musculoskeletal lesions, not clearly visible on fluoroscopy or CT).,
Tissue biopsy from a spinal lesion is now a safe, effective, and reproducible option, and is universally possible even in the traditionally tricky regions of the spine. The surgeons need to train and persuade the radiologists in case the latter are diffident in performing spinal biopsies.
Biopsy material is most likely to grow the organism when it is taken from granulation tissue rather than abscesses. Hence, a CT-guided, targeted tissue biopsy using an 11-G needle is now the gold standard. Fine needle aspiration cytology (FNAC) should be avoided in the spine as the yield is consistently lower than core biopsy as do aspiration of pus alone. Biopsy of granulation tissue is ideal, but if no granulation tissue is available, bone biopsy can be done with good results.
Percutaneous techniques for biopsy have a variable rate of positive yield ranging from 36% to 91% in the infectious spondylodiscitis.,, However, success rate of CT-guided percutaneous biopsy was as high as 91% in the series of Chew et al. Staatz et al. reported 76% positive rate using CT-guided biopsy. Percutaneous biopsy is a technique driven procedure and can be falsely negative due to inadequate sample size, sampling error, or empirical anti-TB treatment (ATT) at the time of biopsy., If percutaneous biopsy is inconclusive, a second percutaneous procedure should be considered before doing an open biopsy. Open biopsy is the most reliable method of procuring a sample for diagnosis but has the obvious drawback of needing anesthesia. It should be considered when repeat percutaneous procedure fails to give a positive result, if there is gross structural damage to tissue, if there is neurodeficit or if the lesion is not accessible through percutaneous approach. Open biopsies have a higher rate of success than percutaneous procedure,, and is indicated if repeated percutaneous biopsies turn out negative and there is a clinic radiological suspicion of non-TB infection or tumor.
Culture of MTB in clinical specimens using TB MGIT culture, the current gold standard is substantially more sensitive than smear microscopy. However, the problem with culture is longer incubation time of approximately 10–14 days. This often leads to patients being put on empirical first-line ATT, and if patient has resistant TB, then this would further increase the tissue destruction and mechanical weakness of the spine. Thus, we need newer tools in the diagnosis of TB to institute timely treatment as per se nsitivity and avert mechanical and neural complications that are so rife in spinal TB.
Newer ultrafast modalities of diagnosis consisting of rapid molecular tests including Gene X-pert and line probe assay (LPA) have revolutionised the utility of nonoperative treatment in spinal TB.,
The development of the Xpert MTB/RIF assay is a breakthrough for the diagnosis of tuberculosis. The GeneXpert test showed a sensitivity of 95.6% and specificity of 96.2% for spinal TB. It is a molecular test which detects DNA of mycobacteria and helps in the detection of mycobacteria as well as rifampicin resistance in just 2 hours. LPA is a similar molecular test detecting resistance not only to rifampicin but also to isoniazide, quinolones, and second-line injectables, thus diagnosing not just MDR but also XDR TB in just 48 hours. Thus, these tests must be asked for on every biopsy specimen in addition to TB MGIT culture and histopathology.
We studied the pattern of drug resistant tuberculosis in the spine to provide guidelines to physicians treating MDR spine TB and make a possible formula for “empirical second-line” treatment if any. We studied the drug resistance pattern of 111 patients of culture proven drug resistant tuberculosis and found resistance to isoniazid (103 patients; 92.7%) followed by 220 rifampicin (91 patients; 82.7%), and streptomycin (82 patients; 74.5%). Among the second-line drugs, resistance was the highest to ofloxacin (38.8%) followed closely by ethionamide (34.4%), moxifloxacin (15.5%), and PAS (8.8%). Lowest resistance was to aminoglycosides – kanamycin and amikacin (5.55%), capreomycin (1.1%);d no resistance was found to clofazamine. Thus, ee could give a possible medical plan for “empirical second-line treatment” in cases where the physician is faced with a situation where the cultures are negative and we are clinically suspecting resistant spine TB.
| Management|| |
Management of spinal tuberculosis has come to a full circle. From the period of conservative management due to lack of well described surgical treatment to aggressive anterior reconstructive surgeries (the “Hong Kong operation”) to now systematic nonsurgical approach due to modern diagnostic techniques and better understanding of chemotherapeutic drugs. It is famously said that spinal tuberculosis in the absence of significant deformity or neurological deficit is medical disease rather than a surgical disease.
Nonsurgical treatment has been proven to be successful with good functional outcomes even in the presence of large abscesses, gross bony destruction, or even early neurological involvement [Figure 1].,
|Figure 1: Excellent result of nonsurgical treatment in a case of thoracolumbar junctional TB treated with 12 months of chemotherapy only.|
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Commonly chemotherapeutic regimens for drug sensitive TB are given for variable duration ranging from 6 month to 12 months, and the older tradition of continuing treatment beyond this for 18 and even 24 months no longer holds scientific value. The standard four-drug initiation phase consisting of isoniazide (H), rifampicin (R), pyrazinamide (Z), and ethambutol (E) for the first 2 months and continuation phase consisting of HRE for another 4–10 months is the regimen now followed. There is no advantage in using streptomycin for “better osseous penetration” as was earlier believed. The trend of adding a fluoroquinolone to the primary four-drug ATT randomly has no scientific basis and should be condemned.
| Determining Endpoint of Treatment|| |
The biggest problem in spinal TB is the lack of strict criteria to determine “healed status.” The endpoint for stopping anti-tuberculous drugs is not well defined.
Clinical improvement, laboratory markers, and radiological assessment help us to determine “healed” status. However, back pain can persist due to mechanical causes even after the disease has healed. Deformity also persists. Though most patients report significant improvement in pain with medical treatment, it has no objective markers and persistence of pain cannot be considered as lack of response. Thus, a “clinical” improvement is judged on the basis of improvement in constitutional symptoms, which are rare at presentation to begin with. Weight gain while on treatment is the other determinant which is nonspecific. Laboratory markers are nonspecific and MRI can continue to show soft tissues and even sterile abscesses after complete eradication of infection [Figure 2]. Thus based on response to drugs, the duration of treatment varies on case to case basis, but the current recommendation is 6–12 months of ATT.
|Figure 2: A young male was on medical treatment for his thoracic spinal TB with paravertebral abscess. MRI at 12 months of treatment (b) looked similar to MRI at the completion of 6 months of treatment (a) despite an excellent clinical recovery. Chemotherapy was discontinued as per protocol at 12 months. The MRI at 18 months (c) done for academic purposes showed complete resolution of the abscess despite being off medication for 6 months.|
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Drug resistant tuberculosis has bought a new dimension in the formulation of chemotherapeutic regimens. We published the first series of 25 culture proven MDR TB spines  in 2009 that brought to light the growing menace of drug resistance in the spine. Our follow-up paper cited before  reported the resistance patterns of MTB in the spine. We gave guidelines in formulating regimens for MDR TB and insisted on tailormade chemotherapeutic regimens.
| Indications for Surgery|| |
Clear surgical indications have remained mainly constant which involve sudden onset neurological involvement, gross deformity or profound neurological involvement at presentation, or progressive neurological involvement while on ATT.
The borderline indications for surgery have clearly moved to nonsurgical treatment. These include:
Even large psoas and prevertebral abscesses are now drained percutaneously for pain relief and culture tissue. Surgical drainage is advised only if the abscess causes a mass effect such as dysphagia or flexion deformity in the hip.
Spinal cord compression
Radiological cord compression due to epidural soft tissue is no longer an indication for emergency surgery unless accompanied by significant neurological deficit clinically. The authors suggest intravenous methylprednisolone and appropriate ATT with close observation in such cases.
Surgeons realize that spinal instability is a transient phenomenon. As the disease responds to treatment, the bony defects fill up and a once unstable spine can heal with excellent functional outcome [Figure 3].
|Figure 3: A clinically unstable central body lesion due to tuberculosis of C4, showing complete bony fusion at the end of 12 months of chemotherapy.|
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| Surgery|| |
With major advances in the posterior approach and techniques in spine, decompressions and stabilization has become easier. Majority of patients are now treated with posterior only approach with favorable results., Advantages with posterior approach are – it is less morbid to patient, is technically an easier and familiar approach for the surgeon, there is preservation of diaphragm and segmental vessels, it biomechanically gives a long lever arm for deformity correction, and screws/anchors give a better hold in the pedicles (posteriorly) which remain least affected as compared to the inflamed vertebral bodies anteriorly.
However, the anterior approach has the advantage that it gives a better anterior reconstruction and neurological decompression as it approaches the lesion directly., Although anterior approach helps in direct decompression, there are certain situations where anterior approach cannot be used such as past history of anterior surgery including CABG, pan vertebral lesions, concomitant pulmonary effusion/adhesions, elderly patients with comorbidities, and anterior approach is avoided in L4-5, L5S1 level due to proximity to major vessels.
Today, anterior column defects are reconstructed through the posterior “transpedicular approach,” making a 360-degree fusion possible through the single posterior incision. Thus, the morbid anterior approach is now hardly used [Figure 4].
|Figure 4: Reconstruction of the anterior column using a titanium mesh cage, from the ‘posterior – only’ approach (a) Anteroposterior view. (b) Lateral view.|
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Use of titanium and stainless steel implants in active spinal TB was controversial till the last decade but has now been proven to be safe and efficacious.
“Splintage surgery” in the elderly
There is an increasing trend, which we also endorse, to perform a “quick fix” surgery in elderly patients who are under the threat of being bedridden due to spinal TB. This comes from the belief that older people tolerate bedbound status poorly and the morbidity and complications of bed rest are high in this group. We noted significantly higher surgical complications in patients over 70 years of age who underwent surgery for spinal TB and were bed ridden preoperatively.
A quick posterior fixation, termed as a “splintage surgery” acts as an internal brace and permits early ambulation in older patients.
Surgery for pediatric tuberculosis spine
Children become special subjects for spinal TB. With the “growth factor” to contend with, rapid progression of the spinal deformity has to be averted. Hence early surgical stabilization is often justified in children. In pediatric age group “spine at risk” signs (facet dislocation, lateral translation, retropulsion, and toppling) help to decide on prophylactic stabilization. Surgical indications remain the same as adult patients. Special attention needs to be given for spinal instrumentation. Pedicle screw systems are good but have the disadvantage of lack of good smaller diameter screws and low profile systems. Implant prominence leads to skin breakdown, especially in the presence of kyphosis and wasted spinal musculature. Sublaminar wires can be a good cost effective alternative.
Further, drug resistance has been found to be significantly higher in children with spinal TB, and therefore, biopsy to know sensitivity patterns is especially necessary though they are young.
| Management of Complications of Healed Disease|| |
Late-onset paraplegia – a delayed presentation of old healed TB spine with progressive neurology and a very high grade kyphosis – is by far the most challenging situation in surgical practice today.
Tuberculosis heals with kyphosis. Healed tuberculosis presents with back pain, pulmonary complication, cosmetic issues, spinal canal stenosis, and late-onset paraplegia. Surgery for kyphosis is indicated if deformity is more than 60° to prevent late-onset neurological deficit. Surgery for kyphosis between 30–60° is indicated based on the disability of the patient. Operative treatment is a significant undertaking and involves complex osteotomies associated with morbidity. Clear understanding of goal of surgery is required to plan treatment.
| Conclusions|| |
The understanding and management of spinal TB has changed much philosophically during the last two decades. The previously described Hong Kong operation, the MRC trials, and the Middle path regimen of Tuli et al., have given way to a new “millennium doctrine”. Currently, the following cardinal principles govern the management of patients with spinal tuberculosis:
The diagnosis of spinal tuberculosis mandatorily must rely upon a positive tubercular culture or histopathology. Keeping in view the mounting threat of MDR/XDR TB, anti-TB drug treatment must not be initiated singly on the basis of clinico-radiological suspicion.
Just a course of 6–12 months of anti-TB chemotherapy is necessary to achieve a cure of spinal tuberculosis; the old practice of 18–24 months of anti-TB drug treatment in spinal tuberculosis is invalid.
A well-tailored, duly monitored nonsurgical treatment often yields as good a result as elective surgery in such conditions as spinal instability, in a paraspinal abscess, and in a radiological spinal cord compression. Earlier, such conditions were often thought of as grounds for surgical intervention.
In the elderly with spinal TB, the focus increasingly is on early ambulation rather than a prolonged bed rest. Early splintage surgery may maximize the benefit.
In children with spinal TB, the “spine at risk signs” can help predict the lesions that need early stabilization surgery in order to prevent the development of growth-related deformity in later years.
The all-posterior surgical approach has gained universal acceptance for carrying out surgical reconstruction in spinal TB. The anterior approach is undertaken only in a small minority.
Implants carried out in an active spinal disease have been found to be quite safe and efficacious.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]