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Treatment of Pott’s disease
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According to the World Health Organization, tuberculosis has become the world's most deadly infectious disease, killing nearly 3 million people per year. Each year there are 8 million new cases of tuberculosis, and 50% of them are infectious. Spinal tuberculosis is the most common form of musculoskeletal tuberculosis. In HIV-negative patients, between 3% and 5% of tuberculosis cases are skeletal, compared with 60% of cases in HIV-positive patients. The incidence and the site of involvement Spinal tuberculosis is the most dangerous form of skeletal tuberculosis because of its ability to cause bone destruction, deformity, and paraplegia. Paraplegia is more common in tuberculosis than in pyogenic spondylitis because the neural arch is involved more often with the former. The spine is involved in 50% of cases of musculoskeletal tuberculosis: 4.2% in the cervical spine, 55.8% in the thoracic spine, 16.9% in the thoracolumbar spine, and 22.8% in the lumbar and lumbosacral spine. Three forms of vertebral involvement have been described; peridiscal, central, and anterior. Two-thirds of the classifiable cases present with peridiscal involvement, while in more than 50% of the cases the primary focus can not be determined because of the extension of the disease. Progression of the vertebral disease is usually by direct subperiosteal or subligamentous spread. Diagnosis Tuberculosis constitutes a diagnostic challenge. Diagnosis is usually a long and tedious process. Usually the clinical manifestation favors the diagnosis however, diagnosis should be confirmed by evaluating the radiographic changes, computed tomography (CT) and magnetic resonance image (MRI) findings, cultures of blood, and/or percutaneous vertebral aspirates, then bone biopsy, either by an open or percutaneous procedure. PPD is predictive in 86% of the cases. Tc99 MDP scintigraphy may be negative in 35% and furthermore Gallium scans could be negative in nearly 70%. No single imaging finding is pathognomonic of Pott’s disease. Slow growth rate of mycobacteria on solid media is a problem due to the nature of the mycobacteria and direct microscopy is insensitive, because samples may contain only a few organisms. And yet, low number of mycobacteria are detected at spine. Diagnostic procedures such as culture, antigen demonstration, serology tests, and polymerase chain reaction are of high priority. The polymerase chain reaction has facilitated the diagnosis and management of tuberculosis. Treatment There have been discussions on whether the treatment of choice should be conservative chemotherapy for 12 months or chemotherapy and surgery combined. Management should be based on the goals of treatment for each individual case. Effective chemotherapy for spinal tuberculosis is the gold standard and mainstay of the treatment and all other methods of treatment are regarded as supplementary. Drug Treatment Regimens The standard triple chemotherapy (isoniazid, rifampin, and pyrazinamide), should be given for at least 12 months, rather than the 6- to 9-month short-term chemotherapy that has been proposed by some authors. Upadhyay et al reported that 6 months of three-drug chemotherapy in conjunction with radical surgery was adequate for the management of tuberculosis of the spine because it produced results comparable with 9-month and 18-month chemotherapeutic regimens, however this should be taken cautiously. Good general supportive care and an effective chemotherapy started at the early stages of the disease are the keys to early and effective eradication and minimizing complications. MRC Working Party showed that the combined standard 18-month chemotherapy with isoniazid and PAS produced a cure rate of 90% in children, which was identical to the results obtained with an additional initial 3-month streptomycin treatment. Ambulant chemotherapy alone provided treatment of tuberculosis with a minimum increase of kyphosis. The results of ambulant chemotherapy, however, were not always satisfactory. Surgery Although chemotherapy is the mainstay in the management of tuberculosis spondylitis, surgical procedures still play an important role. Problems arising from bone destruction, paraplegia, and pulmonary insufficiency due to spinal deformity can not be solved with chemotherapy alone. Indications for surgical treatment include 1) neurological involvement, 2) deformity and/or impending increase in deformity, and 3) the presence of large tuberculosis abscess and/or abundant necrotic tissue. Abscess, tuberculosis lesion, paraplegia, and kyphosis, have been managed surgically by various procedures: Cold Abscess. Aspiration or surgical drainage was carried out for some patients with a large cold abscess because it was thought that evacuation of the abscess improved the patient's general condition, and rapid progression of the abscess along the spine was prevented. Tuberculous destructive lesion. Two surgical methods-focal débridement and anterior radical surgery-are available to eradicate the lesion. 1. Focal débridement. Focal débridement can effectively remove the diseased tissue and sequestra and also can evacuate the abscess; however, it does not prevent the progression of kyphosis due to the lack of anterior support. Focal débridement and simple abscess evacuation provide no long-term advantage over ambulant chemotherapy alone and therefore are no longer accepted as a preferred method of treatment. 2. Anterior radical surgery. Anterior radical debridement and arthrodesis with a strut graft and chemotherapy has been the treatment of choice. There is evidence that better results regarding deformity, recurrence, development of paralysis, and resolution are obtained when radical surgery is performed combined with chemotherapy. Paraplegia. During the early phases of the disease with active infection, possible reasons include direct compression of the neural structures by the abscess and/or sequestrated bone fragments, direct dural invasion, vascular compromise due to compression or thrombosis, acute instability, or severe deformity. Direct compression by abscess or necrotic tissue is the most frequent cause of early onset paralysis and generally has a good prognosis and a relatively high probability to resolve with effective treatment. Paraplegia due to vertebral tuberculous lesion is caused by direct impingement of the abscess, ischemia due to altered blood supply, intra dural abscess and kyphosis. It is generally known that the recovery rate from paraplegia is influenced by many factors: the patient's general state, age, and spinal cord condition; the level and the number of involved vertebrae; the severity of spinal deformity; the duration and severity of paraplegia; the time to initiation of treatment; the type of treatment; and drug sensitivity. Paralysis occurring in children generally have a better prognosis compared to adults Paralysis lasting longer than 6 months is most unlikely to improve, and late paralysis with inactive disease and significant kyphosis is much less responsive to treatment. Paralysis due to vascular insufficiency has a worse prognosis. Several methods have been used for the treatment of patients with paraplegia: 1) chemotherapy alone, 2) laminectomy, 3) costotransversectomy, and 4) radical surgery. In the early stages of the disease, paraplegia caused by abscess can be resolved by effective chemotherapy alone as by decompressive surgery, however, chemotherapy alone is inappropriate management of paraplegia in the patient with advanced tuberculosis and deformity. It is unfair to allow a patient to lie paralyzed for some weeks to months awaiting a cure through conservative care. Decompressive laminectomy will destabilize already hampered spine therefore should not be done. When patients with Pott's paraplegia and severe spinal deformity do not respond to chemotherapy and have worsening neurology, decompressive surgery is indicated to arrest the progress of paralysis and hopefully to restore normal neurology. Kyphosis /Deformity Tuberculosis kyphosis is an unstable lesion that tends to progress until there is sound bony fusion anteriorly. Kyphosis has been managed by several surgical procedures: posterior fusion, anterior radical surgery, and various combined operations such as a one-stage, two-stage, or three-stage procedures. Each patient should be cautioned about the high neurologic risk with corrective surgery of the rigid deformed spine. Until now, the following surgical procedures have been practiced by various surgeons: 1. Flexible Kyphosis: Skeletal traction Posterior fusion Anterior radical surgery Two-stage operation: Posterior instrumentation followed by anterior radical surgery Anterior release and graft, followed by posterior instrumentation Three-stage operation (anterior release followed by posterior instrumentation and delayed anterior radical surgery). 2. Fixed Kyphosis. One-stage operation Two-stage operation (anterior release, deformity correction and anterior graft, followed by posterior instrumentation) Multi-stage operation (osteotomy, halopelvic device, posterior instrumentation and fusion). Skeletal traction for cervical kyphosis. Posterior fusion for kyphosis. Disproportionate posterior spinal growth has been suspected as a contributing factor in the progression of kyphotic deformity after management of spinal tuberculosis by posterior fusion only. Especially, in children frequently there will be a loss of the initial gain of correction and progression of kyphosis after noninstrumented posterior spinal fusion if anterior fusion is not achieved. Additional instrumentation seems to prevent the progression of kyphosis. Anterior radical surgery for kyphosis. Radical surgery (Hong Kong Operation) was found to give better results than focal débridement for the correction and prevention of kyphosis. Progression of kyphosis is more observed in multilevel lesions Posterior closing wedge osteotomy for kyphosis (Galveston one-stage operation). This technique is a very effective one-stage operation. It involves a modified bilateral costotransversectomy approach to the spine, followed by removal of structures in a wedge shape, including the vertebral arch, the disk, and a portion of the centrum. The wedge is closed by posterior compression instrumentation, enabling an angular correction of 30° to 50°. Decancellation or corporal eggshell procedure. This posterior close wedge procedure involves transpedicular curettage or evacuation of the cancellous bone of the vertebral body, excision of the posterior elements and posterior wall of the body, and correction of kyphosis by closing the wedge. This is a highly demanding procedure with additional surgical risks. Two-stage operations. 1. Anterior radical surgery, followed by posterior resection and instrumentation. Yau et al used Luque instrumentation in a two-stage procedure to correct the deformity. 2. Combined posterior instrumentation plus anterior radical surgery for flexible kyphosis (two-stage operation). This procedure may be most appropriate for active cases of progressive kyphosis where the curve is stil flexible. Prevention and correction of kyphosis and kyphoscoliosis by posterior instrumentation has three advantages. Posterior stabilization of the spine arrests the disease early, encourages early fusion, and enables correction of the deformity. The procedure is indicated only in those patients who are likely to develop or who have a pre-existing deformity. It is suggested that a formula be used to predict the kyphosis that will remain at the end of chemotherapy to determine if prophylactic or corrective spinal instrumentation surgery is indicated. (Rajasekaran formula: Y=a+bX (Y= deformity, X=pretreatment loss in VB, a= constant value of 5.5, b= constant value of 30.5)) A two-stage operation, combining posterior instrumentation and anterior interbody fusion, can be an option for multisegmental tuberculosis of more than two segments. Instrumentation at a distance from the infective process restores spinal stability and prevents graft fracture, slipping, sagging, and resorption. Because of the anterior column deficiency due to the anterior column destruction posterior instrumented correction of kyphosis produces an anterior bone gap that should be reconstructed by anterior strut graft; otherwise, recollapse, instrumentation failure, and recurrent kyphosis will be inevitable. After it has been shown that anterior instruments can be used safely at the infected site in tuberculosis patients there have been reports showing the advantages of anterior radical debridement strut grafting and anterior instrumentation. Of course anti tuberculosis drug treatment should never be replaced by any kind of surgery alone. References
Anti-TB drugs First line drugs İsoniazid bactericidal 5mg/kg Rifampicin bactericidal 10mg/kg Streptomycin bactericidal 15mg/kg Pyrazinamide bactericidal 35mg/kg Etambutol bacteriostatic 30mg/kg Thiacetazone bacteriostatic 350mg/d Principles
Mechanism of action Against large population of mb actively multiplying in the walls of the cavity Isoniasid (bactericidal) Rifampicin (bactericidal) Streptomycin (bactericidal) Etambutol (bacteriostatic) Pyrazinamide (ineffective) Against small population of mb slowly multiplying inside macrophage and low pH Pyrazinamide (most effective) Isoniasid (ineffective) Rifampicin (ineffective) Streptomycin (ineffective) Intermittently multiplying bacilli in solid caseous material Only rifampin is active
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