A Surgical Revisitation of Pott Distemper of the Spine Larry T

The Spine Journal 3 (2003) 130–145

Review Articles A surgical revisitation of Pott distemper of the spine Larry T. Khoo, MD, Kevin Mikawa, MD, Richard G. Fessler, MD, PhD* Institute for Spine Care, Chicago Institute of Neurosurgery and Neuroresearch, Rush Presbyterian Medical Center, Chicago, IL 60614, USA Received 21 January 2002; accepted 2 July 2002

Abstract Background context: Pott disease and tuberculosis have been with humans for countless millennia. Before the mid-twentieth century, the treatment of tuberculous spondylitis was primarily supportive and typically resulted in dismal neurological, functional and cosmetic outcomes. The contemporary development of effective antituberculous medications, imaging modalities, anesthesia, operative techniques and spinal instrumentation resulted in quantum improvements in the diagnosis, management and outcome of spinal tuberculosis. With the successful treatment of tuberculosis worldwide, interest in Pott disease has faded from the surgical forefront over the last 20 years. With the recent unchecked global pandemic of human immunodeficiency virus, the number of tuberculosis and secondary spondylitis cases is again increasing at an alarming rate. A surgical revisitation of Pott disease is thus essential to prepare spinal surgeons for this impending resurgence of tuberculosis. Purpose: To revisit the numerous treatment modalities for Pott disease and their outcomes. From this information, a critical reappraisal of surgical nuances with regard to decision making, timing, operative approach, graft types and the use of instrumentation were conducted. Study design: A concise review of the diagnosis, management and surgical treatment of Pott disease. Methods: A broad review of the literature was conducted with a particular focus on the different surgical treatment modalities for Pott disease and their outcomes regarding neurological deficit, kyphosis and spinal stability. Results: Whereas a variety of management schemes have been used for the debridement and reconstruction of tuberculous spondylitis, there has also been a spectrum of outcomes regarding neurological function and deformity. Medical treatment alone remains the cornerstone of therapy for the majority of Pott disease cases. Surgical intervention should be limited primarily to cases of severe or progressive deformity and/or neurological deficit. Based on the available evidence, radical ventral debridement and grafting appears to provide reproducibly good long-term neurological outcomes. Furthermore, recurrence of infection is lowest with such techniques. Posterior operative techniques are most effective in the reduction and prevention of spinal deformity. Conclusions: Unlike historical times, effective medical and surgical management of tuberculous spondyitis is now possible. Proper selection of drug therapy and operative modalities, however, is needed to optimize functional outcomes for each individual case of Pott disease. © 2003 Elsevier Science Inc. All rights reserved.

Keywords: Pott disease; Tuberculosis; Spondylitis

Introduction sis in 1996 than in any previous year in history [7]. There are presently over 40 million active cases of tuberculosis Tuberculosis has and continues to be the world’s most globally with 8 to 10 million new cases expected each year prevalent and lethal infectious disease with over 3.5 million [8]. Based on a 1% to 2% incidence of skeletal involvement, deaths yearly [1–6]. More individuals died from tuberculo- World Health Organization figures estimate that there are FDA device/drug status: not applicable. over 800,000 active cases of tuberculous spondylitis [8,9]. Nothing of value received from a commercial entity related to this Within the United States itself, the prevalence of tuberculo- research. sis increased from 1986 to 1992. Increasing populations of * Corresponding author. Chicago Institute of Neurosurgery and Neu- roresearch, 2515 North Clark Street, Suite 800, Chicago, IL 60614, USA. elderly nursing home patients, the homeless, Southeast Tel.: (773) 388-7759; fax: (773) 935-2132. Asian and Central American immigrants and patients in- E-mail address: [email protected] (R.G. Fessler) fected with the human immunodeficiency virus (HIV) have 1529-9430/03/$ – see front matter © 2003 Elsevier Science Inc. All rights reserved. PII: S1529-9430(02)00410-2

L.T. Khoo et al. / The Spine Journal 3 (2003) 130–145 131 all contributed to this increasing prevalence [10–14]. De- spite improved screening and treatment programs, tuberculosis persists as a significant health problem in the United States [6,8]. In African nations, the reported rate of cases has increased by over 200% in the last 5 years because of the region’s unchecked HIV pandemic [3,15]. In sub- Saharan Africa alone, conservative estimates show that there are approximately 25 million cases of active HIV with up to 50 million cases worldwide [16]. Of HIV cases in developing nations, approximately 10% to 15% will develop active tuberculosis. Up to 60% of these HIV-positive tuberculosis patients will have skeletal involvement, a figure that is far greater than the usual 1% to 2% incidence seen in HIV-negative patients [17,18]. From these epidemiological data, it is clear that a global resurgence of Pott disease is upon us.

Historical perspectives “To attend to a distemper from its beginning through a long and painful course, to its last fatal period, without even a hope of being able to do anything which shall be really serviceable, is of all tasks the most unpleasant” (Sir Percival Pott, 1779)[19]. Although Dr. Pott is credited with this early grim description of spondylitis, tuberculosis as a disease has afflicted humans since the dawn of time [19]. From the Arene Candide cave in Liguria, Italy, the remains of a 15- year old male buried in the first half of the fourth millennium BC were found to have tubercular lesions of the vertebral column [20]. Similarly, evidence of tuberculous spondylitis has been found in the mummified remains of both Egyptian kings and slaves alike from as early as 3400 BC [21]. In the Sanskrit writings of ancient India, numerous references to tuberculosis under the eponym “Yakshma” are replete in the Rig, Atharva Vedas (3500 to 1800 BC) and Susruta Samhitas (1000 to 600 BC) [21,22]. It is humbling Fig. 1. For centuries, many of those who survived their bout with tubercu- to note that the Vedic physicians’ prescription of high alti- losis would suffer from chronic gibbus deformities. Treatment of the kyphus was limited to primarily external manual reduction maneuvers tude, fresh air, rest, immobilization and constitutional sup- including this example of a novel extension, traction-type bench utilized by plementation was the same as that used by “modern” West- Hippocratic school physicians of the middle-ages [32]. ern doctors until the 1940s [23]. One millennium later, Hippocrates in his work, On Artic- ulations, vividly described both the deforming kyphus and the sanitoriums and also made surgical intervention feasible draining fistulae in patients afflicted by “Pott’s Distemper.” by lowering the mortality rate [25–29]. In an effort to assess Galen subsequently recognized the relationship between the efficacy of these new medical and surgical treatments, these tubercular changes and spinal deformity and pub- the Medical Research Council (MRC) was founded in 1963 lished his observations in the second century AD [24]. As to direct prospective research on the epidemiology, diagno- such, both Hippocratic and Galenic physicians used a novel sis and treatment of tuberculosis [26,30–37]. “extension” bench to control spinal deformities through manual reduction techniques (Fig. 1). In their respective Pathophysiology sixteenth- and seventeenth-century publications, Diechamp in France and Severino in Italy both postulated that the pro- Tuberculosis is a chronic, insidious and recurrent bacte- gressive spinal deformity was responsible for the paraplegia rial infection caused by M. tuberculosis, Mycobacterium observed in these patients [8]. With the advent of germ the- bovis or Mycobacterium africanum. M tuberculosis is the ory, Robert Koch correctly identified M. tuberculosis in most common cause of tuberculosis and appears as an 1892 as the microbial culprit responsible for this wake of “acid-fast bacillus” with appropriate staining on micro- human suffering [23]. In 1944, the introduction by Schatz scopic examination. The lungs are most commonly infected and Waksman of streptomycin emancipated thousands from because M tuberculosis is a strict aerobe and strongly de-

132 L.T. Khoo et al. / The Spine Journal 3 (2003) 130–145 pendent on oxygen tension. Miliary spread of the bacilli with tuberculoma formation can, however, occur in virtu- ally any organ [1,2,38–40]. The gross pathologic finding in tuberculous spondylitis is one of granuloma formation con- sisting of exudative granulation tissue and interspersed abscesses. As the abscesses coalesce, regions of caseating necrosis result and appear as a yellow, opaque, “cheesy” substance. Microscopic examination of the granuloma re- veals a nodular pattern with central necrosis. Langerhans gi- ant cells with peripheral nuclei are common, although not pathognomonic [41]. Special staining of adequate pathologic samples may expediently reveal a causative acid-fast bacilli in the case of M. tuberculosis or other fungus [17]. Tuberculosis infections of the spine are usually the result of seeding from an extraspinal source (eg, pulmonary infection) and commonly manifest as paradiscal, anterior or central lesions [17]. In adults, there are four primary patterns of involvement: 1) paradiscal, 2) anterior granuloma, 3) central lesions and 4) appendiceal type lesions [8,9,42]. Of these, the paradiscal lesion is the most common and repre- sents approximately half of all cases [41]. In the paradiscal lesion, the primary focus of infection is in the vertebral metaphysis. The enlarging granuloma subsequently erodes through the cartilaginous end plate and then begins to nar- row the disc space (Fig. 2). Anterior granulomas develop beneath the anterior longitudinal ligament and can span several vertebral segments. Although anterior granulomas typically demonstrate less bony destruction and deformity than paradiscal or central lesions, elevation of the periosteum can result in bone devascularization with subsequent development of an abscess, necrosis and deformity. In central lesions, the entire vertebral body is involved, thereby causing significant deformity as the body loses structural integrity causing one or more pathologic fractures. Patients with central lesions will commonly have two or three affected vertebrae. Infections of the atlas, axis and isolated neural arches are less frequent but more likely to cause neurological deficits [43,44]. Skip lesions in different stages of development occur in approximately 10% of patients [41]. Lastly, the appendiceal type of lesion propagates in the laminae, pedicles, articular facets and spinous processes, causing initial expan- sion followed by subsequent rupture and failure [8]. Abscesses, commonly found in spinal tuberculosis, follow tissue planes but may extend into the spinal canal at any level. Fig. 2. Example of a tuberculoma of the lumbar spine at L4 and L5. The The periphery of the abscess can form thin or dense adhe- sagittal gadolinium-enhanced T1-MRI image demonstrates spondylitic sions with visceral and vascular structures. Further, these le- destruction with increased signal and enhancement of the vertebral bodies and disc space (A). Lateral and AP radiographs show the bony erosion and sions may cause symptoms resulting from neurovascular kyphoscoliotic deformity with intervertebral collapse and tilt that is typical compression (eg, pain), hemorrhage and direct mass effect of the early gibbus (B, C). Plain radiographs, however, often underestimate [4,20,21,26,30–37,39,45–48]. In the neck, abscesses are more the full extent of the infection. Often, contrast-enhanced CT or MR images common in children than adults. Such lesions are often symp- are needed to completely define the degree of tuberculous injection in the tomatic because of compression of the trachea and esophagus paravertebral soft tissue (D, E). [49]. In the thorax, the abscess may invade the lung and create pleural and/or diaphragmatic adhesions with the lung. In- vasion of the femoral trigone occurs when the abscess travels region through the greater sciatic foramen. A rupture of an down the psoas sheath from the lumbar region. Abscesses in abscess through the skin may create a draining sinus, thereby the sacral region can also invade the perineum or the gluteal increasing the risk of superinfection.

L.T. Khoo et al. / The Spine Journal 3 (2003) 130–145 133 Neurological deficits are a consequence of 1) direct neural to the initial degree of radiographic kyphosis [17]. With cir- compression by granulomas, abscesses, sequestra of vertebral cumferential erosion of both the posterior arch and anterior bodies and discs (extra- and intradural extramedullary tuber- body, translational instability can occur with resultant ante- culomas), 2) direct invasion of the neural parenchyma (in- rior, lateral, rotatory subluxation and a significantly increased tramedullary intradural tuberculoma), 3) tuberculous meningi- risk of neurological compromise [3,62]. tis, 4) pathological dislocation and subluxation of bony elements, 5) vascular compromise (thrombosis, direct pres- Clinical presentation sure) [8,17,24,38,50–52]. The granulomas can create neurological compromise by transdural compression of neural ele- The clinical presentation of a particular patient will vary ments or by invading the dura. The majority of such depending on the age and health status of the patient, the lo- compressive lesions are secondary to an admixture of purulent cation of the infection, the stage of the disease and the ab- material and osseous elements [53]. However, pure granulo- sence or presence of abscesses, sinus tracts and neurological matous or abscess-only compression of neural elements with- compromise. Systemic symptoms of weight loss, fever and out an associated bony lesion has also been reported [54,55]. malaise usually precede spinal involvement for several Intramedullary tuberculomas, first described in 1830 by months. When the spine is involved, the most common pre- Sere, are much rarer than their intracranial counterparts but senting complaint is one of pain with an insidious onset as have the same histological appearance of central caseation opposed to complaints of acute pain with pyogenic infec- surrounded by an often intense pachymeningitic arachnoiditis tions [60]. Cervical involvement may present with com- [8,51]. Because of the predominance of anterior spinal ele- plaints of torticollis, neck pain and stiffness, stridor and ment involvement, ventral neural compression is most com- dysphagia. Neurological compromise reported in 10% to mon, but isolated or concomitant posterior compression may 61% of patients with spinal tuberculosis may be manifested occur. Also, abscesses or the sequestra of vertebral body or as somatosensory changes, weakness and changes in bowel disc in the epidural space may directly press on neural ele- and bladder function [60]. In underdeveloped countries, ments resulting in neurological deficits. Tuberculous spinal paraplegia, kyphosis, deformity and draining sinuses are meningitis may present in three main forms: 1) tuberculoma common presenting complaints because of poor health-care arising in the pachymeninges, 2) secondary extension of in- access and patient neglect [32,67]. Even in industrialized tracranial basal meningitis and 3) secondary extension from nations, the diagnosis of tuberculosis can be delayed for up tuberculous meningitis [52]. Thick exudates are typically to 2 years after the onset of symptoms [58]. A complete seen surrounding the meninges, cord and nerve roots with in- physical and ophthalmological examination may yield sys- termingled fibrous bands of granulation tissue. At times, cys- temic signs of mycosis, spinal alignment deformity, subcu- tic formation with pockets of cerebrospinal fluid can occur as taneous flank masses and evidence of cutaneous fungal in- a result of these changes [56]. Vascular ischemia, infarction, fections and/or sinuses. The neurological examination delayed myelomalacia, gliosis and syringomyelia may also should assess the function of cranial nerves, somatosensory result [57]. Isolated pathologic dislocation or subluxation of and motor systems and the rectal sphincter, and determine the bony elements is an infrequent cause of neurological the presence of myelopathy (ie, hyperreflexia, sustained compromise [58–61]. In the setting of apparent disease quies- clonus and pathological reflexes, such as Babinski and cence, late paraplegia may occur because of such vertebral Hoffman signs). Classical physical findings include local body failure. Paraplegia is far more common in tuberculosis tenderness, muscle spasm, restricted spinal motion, defor- than in other forms of pyogenic spondylitis because of the in- mity and neurological deficit [3,4,26,30–37,46–48,62,68– creased frequency of neural arch involvement and of patho- 72]. Pain is an excellent localizing sign with the most com- logical fracture with neural compression [62,63]. mon locations being the thoracic spine followed by the lum- Spinal lesions comprise 50% of cases of articuloskeletal bar, cervical and sacral regions [67,73]. Paraplegia is most tuberculosis, which comprise 3% of tuberculosis cases in often from thoracic and cervical spondylytic destruction HIV-negative and 60% of HIV-positive cases [8,9,17,18]. Of [49,73]. Abscesses and fistulae are found in the groin and spinal tuberculomas, 5% are in the cervical spine, 75% in the buttocks and can be mistaken for other types of anorectal thoracic spine and 20% in the lumbar and sacral spine. Ky- fistulae [38]. photic deformity results from the collapse of anterior vertebral elements and is most commonly seen in thoracic lesions. Clinical subgroups The loss of one vertebral body may produce as much as 32 degrees of kyphosis, but often multiple levels are affected In younger children, far more extensive disease with mil- [39,49,64–66]. Kyphotic deformity progresses until the col- iary spread is often found at the time of diagnosis. Al- lapsing vertebral bodies meet anteriorly or the granulating though larger abscesses are more frequently encountered, and caseating tissue mature into bone. By the first 18 months there is a relatively low incidence of paraparesis (15% to after medical treatment, most of the vertebral collapse has oc- 20%) and paralysis in pediatric cases. This is in direct con- curred, and the ultimate degree of kyphotic deformity is pro- trast to the adult subgroup that has far more localized dis- portional to the initial loss of the vertebral bodies as opposed ease but a much higher incidence of paraplegia (over 80%)

134 L.T. Khoo et al. / The Spine Journal 3 (2003) 130–145 [1,25,45,49,67,74–76]. In the United States, Europe and able to rapidly detect and diagnose several strains of Myco- Middle East, where disease prevalence is relatively low, bacterium without the need for prolonged culture and spe- older adults are more commonly infected than children. cial histological staining techniques [87]. Furthermore, PCR However, in areas of higher prevalence (eg, Asia and Cen- techniques have been used to identify discrete genetic muta- tral America) children are more commonly infected than tions in DNA sequences associated with drug resistance adults [3,4,26,30–37,46–48,62,68–72]. In western coun- [88]. Rifampin resistance has been mapped to a small region tries, spinal involvement is typically less severe with fewer of an RNA polymerase (rPOB) gene, and ciprofloxacin and neurological symptoms and a milder degree of deformity streptomycin resistance has been localized to gyrase A (Gyr [6,75,77]. Also spondylitis without disc involvement has A) and ribosomal protein SR (rPSL) genes [3]. As such, been increasingly reported in industrialized nations in con- PCR techniques can now be used to specifically select drug trast to the classic spondylodiscitis typically seen elsewhere therapy based on the organism’s genetic makeup for each [6], presumably because of better access to care and early case [89]. diagnosis. Radiographic evaluation In immunocompromised patients with advanced HIV disease, the clinical presentation can be masked by numerous The classic case of tuberculous spondylitis is described other HIV-associated changes in the central and peripheral as beginning anteriorly and advancing superiorly and inferi- nervous system, including vacuolar myelopathy of the spinal orly to the disc space. However, hematogeneous seeding to cord, demyelinating neuropathy, dementia and coexistent in- the end-plate subchondral metaphyseal bone is more likely fection with other organisms (cytomegalovirus, herpes, vari- because of its rich vasculature [90]. As the disease progresses, cella, Jacob-crutzfeld, treponema, Candida, Cryptococcus, paravertebral abscesses develop, the disc space is destroyed Mucormycosis, Toxoplasma) [18]. Instead of classic paraple- and adjacent bodies become rarefied, resulting in kyphotic gia, deformity and pain, these individuals may present with deformity as the vertebral body collapses. Imaging studies progressive ataxia, dementia, spastic paraparesis, myelopathy are used to visualize this process and include spine and and sphincter disturbances [8,78,79]. Lastly, a distinct syn- chest plain films, radionuclide scanning, CT and magnetic drome of tuberculous spondylitis has been reported in intra- resonance imaging (MRI). The basic imaging analysis in- venous drug addicts, many of whom are HIV positive as well. cludes spine and chest plain films to visualize advanced rar- In these patients, acute fever, intense back pain, weight loss, efaction, bony deformity, disc space narrowing, anterior night sweats and rapidly evolving deficits with diffuse mil- vertebral collapse, vertebrae plana, kyphosis and abscesses. iary spread was observed [24,80]. Rarefaction, vertebral edge lucency and loss of cortical mar- gins can be seen 2 to 4 weeks after spinal infection and may involve multiple segments. Paravertebral shadows indicat- Evaluation and diagnosis ing paravertebral swelling usually over two to three segments is often seen as the illness progresses. Abscesses may Laboratory investigations appear as widened paravertebral shadows with soft tissue In the laboratory evaluation the white blood cell count is calcifications and loss of the psoas muscle shadow. Involve- typically normal and the erythrocyte sedimentation rate ment of the disc space resulting in disc space narrowing on (ESR) is elevated above 20 mm/hour in 80% to 100% of pa- radiographs is commonly seen before vertebral body col- tients with spinal osteomyelitis [81]. However, 5% to 10% lapse (Fig. 2, A to C). With plain radiographs, the extent of of children have an ESR greater than 20 mm/hour [82], and the disease is often underestimated, requiring radionuclide healthy elderly patients and pregnant women have mildly scanning, CT and MRI with contrast enhancement to fully elevated ESRs [83]. The Mantoux test (tuberculin skin test) demonstrate the extent of the tuberculomas and abscesses is typically positive, but anergic individuals will produce (Fig. 2, D and E). The differential diagnosis of granuloma- false-negative results. Serological testing using enzyme- tous disorders of the spine includes sarcoidosis, Candida, linked immunosorbent assay and agglutination titers can Torulopsis, Aspergillus, Coccidioides immitis, Blastomyces, provide additional information about tuberculosis and fun- Actinomyces [91], Nocardia [91–93], atypical Mycobacte- gal infections. The definitive diagnosis is made with open or rium [21,93–96], Brucella [97,98], nonvenereal Treponema percutaneous trephine needle biopsy of the bone and disc (yaws) [99] and Echinococcus (hydatid disease) [100]. using computed tomography (CT) or fluoroscopic guidance Technetium 99m pyrophosphate is the most common [84,85]. Cultures and special stains of the biopsied speci- scintigraphic study, because it is the most sensitive. How- mens will identify the causative pathogen. However, such ever, it is not specific [101]. Gallium scintigraphy can be isolation of the bacterium from clinical specimens can often performed in early stages of disease and is useful for whole take several weeks with sensitivities as low as 50% [86]. body screening. CT is excellent for defining the anatomy of Recent advances in polymerase chain reaction (PCR) tech- bony destruction, extension into the spinal canal, posterior niques have opened exciting new avenues of diagnosis and element involvement and formation of paravertebral ab- treatment. By amplifying species-specific DNA sequences scess. As a single modality, however, MRI is the modality in even formalin-fixed paraffin-embedded samples, PCR is of choice, because it provides superior anatomic detail of

L.T. Khoo et al. / The Spine Journal 3 (2003) 130–145 135 the thecal sac, neural structures and paravertebral areas mens. The 5- and 10-year results confirmed the effective- [40]. CT myelography can show similar details, but scintig- ness of the ambulatory regimen and could demonstrate no raphy cannot. Myelography also allows for collection of benefit of the other adjunctive measures [34,36]. With the cerebrospinal fluid for analysis to evaluate neurological in- addition of rifampin, the MRC altered their recommenda- volvement. With gadolinium, MRI can discriminate be- tions to the following front-line agents: INH, rifampin, tween abscesses and granulation tissue and can define a soft pyrazinamide, streptomycin and ethambutol. Second-line tissue mass and the extent of bony destruction. Noncon- agents include ethionamide, cycloserine, kanamycin, capre- trasted CT scans provide useful and complementing render- omycin and PAS. The latest MRC studies have demon- ing of bone detail, especially for surgical planning. strated that isoniazid and rifampin given for 6 to 9 months was as effective as isoniazid and paraaminosalicylic acid or ethambutol given for 18 months [31,33]. However, signifi- Medical management cant controversy continues to surround the optimal length of therapy. In particular, several authors have criticized the In general, chemotherapy and adequate rest and nutrition large degree of bone resorption and kyphosis seen with only are the cornerstones of therapy for spondylitis caused by short-course 6- and 9-month regimens [106–108]. To pre- typical and atypical Mycobacterium, fungi, actinomyces, vent recurrence, prevent delayed kyphosis and to eradicate a nocardia, brucella, echinococcus and nonvenereal tre- paucibacillary disease with slow-growing bacilli, triple- ponema organisms. The overall goals of medical treatment drug therapy (INH, rifampin, ethambutol) for 18 months or include 1) recovery and/or maintenance of neurological four-drug therapy (add pyrazinamide) has been advocated function, 2) recovery and/or maintenance of mechanical by these groups. For the cases typically seen in Western in- spine stability, 3) diagnosis and elimination of the causative dustrialized nations, a 6-month, three-drug regimen with pathogen and 4) functional return to activities of daily living INH, rifampin and pyrazinamide should be used for most as soon as possible. Medical and conservative management patients with drug-sensitive infection [109]. alone for cases without significant paraplegia, deformity or Isoniazid is administered at a typical dose of 5 mg/kg/ instability has yielded good results in countless patients. In day up to 300 mg/day and should be supplemented with py- Tuli’s classic series of over 200 cases without neurological ridoxine to prevent peripheral neuropathy. Rifampin 10 mg/ deficit, resolution of disease with good outcomes was ob- kg/day up to 600 mg/day is concurrently given with iso- tained in 94% of patients with antibiotic treatment alone [9]. niazid. Pyrazinamide should also be prescribed at a dose of This “middle-path” of reserving surgery only for medical 15 to 30 mg/kg/day up to 2.0 g/day for up to 2 months only failures is further substantiated by findings of the MRC, to prevent hepatotoxicity [4,26,30–37,46–48]. Because who found 93% favorable outcomes in patients treated with pain, inflammation and bone resorption are of particular only a 6- or 9-month regimen of antibiotics [46,47]. How- concern during the initial phase of therapy, several groups ever, the true meaning of “favorable” must be interpreted in have advocated the use of nonsteroidal anti-inflammatory light of the health-care resources available and the func- agents. The antiprostaglandin effect of these agents is tional expectations of the patient and physician. thought to decrease nonspecific synovial inflammation and bone resorption as well [62,69,110]. Baseline laboratory val- Antimicrobial regimens ues for hepatic enzymes, bilirubin, serum creatinine, Blood The modern era of antituberculous therapy began in 1943 Urea Nitrogen (BUN), Complete Blood Count (CBC), and with Waxsman’s discovery of streptomycin [28]. Within 5 platelets should be obtained initially, and these values may years after its introduction, mortality rates in conservatively be monitored at 1 or 3 months or more frequently depending managed patients decreased by nearly 70% across the globe on particular clinical situations. Directly observed therapy is [102]. Isoniazid (INH) and p-aminosalicylic acid (PAS) were an important component of medical management, because pa- subsequently introduced in 1952 with excellent clinical effi- tient nonadherence to a prescribed treatment is a major cause cacy in eliminating the risk of disease dissemination and of therapeutic failure and of the emergence of resistant or- preventing chronic abscess and sinus formation [103]. ganisms. In this multi–drug resistant era, drug susceptibility These drugs were also successfully used without surgery should be tested before starting treatment and again 3 months when patients were kept immobilized in orthoses at bed rest later. When technically feasible, PCR should be performed for long periods [104]. early on to allow for rapid identification of resistant strains A second major evolution in tuberculosis treatment came and timely adjustment of the drug regimen. If the organisms about in Nigeria when a shortage of beds forced physicians are resistant to isoniazid, then ethambutol 15 to 25 mg/kg/day to use INH and PAS on an ambulatory basis. Although cos- up to 2.5 g/day should be added to the chemotherapy. metic deformity was problematic, over 96% of their patients were cured with this regimen [105]. The MRC subsequently Operative indications and timing conducted controlled prospective studies on the effect of the length of bed rest, plaster of Paris jacket orthoses and the With the indisputable efficacy of medical treatment addition of streptomycin to standardized INH and PAS regi- alone, the proper role of surgery in the treatment of tubercu-

136 L.T. Khoo et al. / The Spine Journal 3 (2003) 130–145 lous spondylitis is a subject of ongoing controversy [40]. On be slow and prolonged [67]. Patients with active caseating the one hand, Hodgson and Stock [111] advocated surgical disease and nonosseous abscesses typically recover faster debridement of tuberculous spinal lesions as soon as possi- than those with a chronic hard, bony kyphus and long-stand- ble after the diagnosis has been made. From their experience, ing neural compression [45]. Hodgson and Stock [111] un- they observed that earlier surgical extirpation was technically derscored this finding in their study that demonstrated a di- easier, prevented delayed deformity, shortened the patient’s rect correlation between the duration of neurological length of hospitalization and reduced the incidence of relapse. symptoms before surgery and the time to recovery postoper- On the other hand, the prospective trials comparing the out- atively. Other poor prognosticators for neurological im- comes of surgical intervention with that of medical treatment provement include direct infiltration of the pachymeninges alone have not substantiated such a philosophy. Indeed, present and radiographic evidence of spinal cord atrophy [67,118]. MRC recommendations are that surgery be reserved only for Surgical morbidity and complications also increase for de- diagnostic biopsy, spinal instability, severe deformity, myelop- layed procedures, because late fibrosis makes operative de- athy, severe sepsis, significant abscesses and open draining si- bridement more difficult as well [24]. nuses [4,26,30–37,46–48]. As a useful heuristic, the spinal surgeon should consider three main questions for every case of Treatment of kyphosis tuberculous spondylitis. First, what is the rationale for the operation (eg, to treat infection, neurological deficit, deformity pain The residual kyphosis that is seen after ambulant chemo- or functional restriction)? Second, when should the operation therapy has always been a source of concern. In Konstam’s be performed (ie, early, during medical treatment or after)? Fi- original study of ambulant chemotherapy, only 75% devel- nally, what is the best operation or combination of procedures oped a clear radiographic bony fusion with 49% having 0 to to accomplish these goals? 10 degrees of residual kyphosis and 18% having more than 30 degrees of kyphosis [105]. Data from other MRC studies have also echoed these findings with nonsurgical regimens Treatment of neurological deficits yielding a solid fusion in 65% to 79% of cases [31,36]. For cases of mild neurological deficit (eg, paraparesis) or From a review of their experience, Moon et al. found that even early paraplegia, several studies have demonstrated the the kyphotic progression in these patients was typically ar- effectiveness of medical therapy without surgery [112,113]. rested within the first 6 months of drug treatment and was Lin et al. found that the majority of patients with only mild not influenced by the overall length of therapy beyond that neurological symptoms would improve without surgical de- [3,62,68–70]. A controlled study by the Medical Research compression [114]. Of 89 consecutive patients with clear Council of England compared the results of inpatient versus paraplegia who were treated with antibiotics and bedrest outpatient medical treatment and found a slightly greater alone, Pattison [63] demonstrated that 85% returned to a mean total vertebral loss and angulation in patients treated normal life with full activity. Similarly, Moon et al. [69] on an ambulant basis [36]. Further, use of orthoses and plas- conservatively treated 75 such patients with favorable out- ter casts did not seem to affect the ultimate kyphotic angula- comes seen in 95% of them. However, more recent prospec- tion in either group. When compared with adult cases as a tive data would suggest that the prognosis of patients with whole, more advanced cases of tuberculous spondylitis and moderate to severe neurological impairment is significantly children with posterior element involvement are more likely improved by early surgical decompression and reconstruc- to be complicated by significant residual kyphosis after am- tion. When Lin et al. considered all patients with neurologi- bulant chemotherapy [30,31,69,122,123]. Rajasekaran and cal deficit; they found that there was an improvement rate of Shanmugasundaram [124] prospectively analyzed the ky- 94% with early surgery versus only 79% with nonsurgical photic angulations after medical treatment in over 90 pa- management [114]. Patients with deficits that were man- tients for 6 years. From the controlled nonsurgical arm of aged according to the “middle-path” regimen who subse- the study, these authors were able to extrapolate a unique for- quently had surgery obtained a similar overall success rate mula to predict the final gibbus angle after treatment within a of 78.5% as well [9,61,115]. From a review of the literature, 90% degree of accuracy [125]. From the formula Y 5.5+30.5X patients with less severe neurological deficit and those un- (Yfinal angle of the deformity, Xinitial loss of vertebral dergoing earlier surgery fare better than patients with severe body height), patients with an excessive predicted Y value deficits and later surgery [9,38,67,116–119]. Ultimately, were surgically reconstructed. Cases with multiple levels of numerous studies have emphasized that neurological out- vertebral involvement, thoracic lesions, active growth and come is directly correlated with rigid bony fusion regardless skeletal immaturity were also predictive of an increased of whether it is spontaneous or surgically induced [38,120,121]. amount of posttreatment kyphosis [8,115]. As such, some authors have advocated only a fusion procedure Based on these considerations, an attempt should be for patients with mild deficits and reserved aggressive decom- made to estimate the amount of kyphosis expected after pression for cases of severe paraplegia [45,49]. medical treatment alone. When this figure is excessively The overall prognosis for neurological recovery after high or there is evidence of significant progression during timely surgical intervention is generally good but can often medical treatment, surgical intervention to correct and pre-

L.T. Khoo et al. / The Spine Journal 3 (2003) 130–145 137 vent deformity is reasonable. Absolute criteria of the degree of acceptable deformity will vary tremendously from case to case. Whereas a 20-degree deformity may be considered acceptable to patients in developing nations with limited medical resources, few patients in Western countries would be willing to accept such a severe long-term cosmetic deformity. However, operative correction of severe kyphosis is extremely technically demanding and carries a high risk of neurological injury [116,126]. Reduction of significant chronic fixed deformities for cosmetic reasons should be performed sparingly and with great caution [3]. In such cases, it is best to operate earlier on while the kyphosis is still mobile and not excessive.

Surgical techniques From the late 1800s until the early 1900s, thousands of posterior laminectomies were performed worldwide for tuberculosis. The outcomes of these operations were, however, uniformly disappointing [64,74,116,127–129]. Seddon Fig. 3. Numerous corridors of access have been used in the surgical treat- [130], in his 1934 review on the topic, openly condemned ment of tuberculous spondylitis. The specific choice of approach should be laminectomy for its dismal results, its inability to provide tailored to the location of the bulk of the abscess and tuberculoma. For most cases of Pott’s disease, the pathology lies ventrally thereby necessi- adequate access for safe debridement and its failure to arrest tating an anterior approach for adequate debridement and reconstruction. progression of the deformity. Founded on the orthopedic These approaches are shown in italics. principle that ankylosis of peripheral joints often led to remission of destructive synovitides, Hibbs [64] introduced the concept of in situ posterior arthrodesis with autogenous of streptomycin and INH in the 1950s, the surgical mortality bone grafting in 1911. Because of the lack of spinal instru- rate plummeted from 70% to 0% to 2.1%, thereby causing a mentation at the time, such unsupported fusions proved in- renaissance of surgical treatment for Pott disease [139]. effective in preventing delayed kyphosis and subsequent Abscess drainage and excision paraplegia and were thus largely abandoned as a surgical solution [131]. In his original manuscript, Sir Percival Pott described To address these surgical shortcomings, Capener [132] successful drainage of a tuberculoma: “The remedy for this and Menard [76,133] used a lateral rachiotomy (eg, costo- most dreadful disease consists merely in procuring a large transversectomy) approach to obtain an improved postero- discharge of matter.... and in maintaining such discharge until lateral corridor for the debridement of ventral tuberculomas the patient shall have perfectly recovered the use of his legs” in the late 1920s (Fig. 3). Like laminectomy, however, pos- [19]. For the majority of cases of tuberculous spondylitis, terolateral approaches also contributed to the instability of such open drainage was generally ineffective and often le- the spinal column. Transperitoneal and transthoracic surgi- thal. With the efficacy of modern antituberculous therapy, cal exposures of the anterior spine were subsequently devel- many patients now experience early resolution of their oped in the 1930s to treat both tuberculosis and spondylolis- sepsis but still demonstrate persistent large tuberculomas thesis [134,135]. On the other side of the globe, Ito et al. known as “cold abscesses” [3,56,75,80,112]. Percutaneous [129] concurrently reported his series of tuberculosis pa- aspiration or open drainage of these lesions was originally tients who were successfully treated by anterior debride- thought to speed patient recovery, to prevent abscess exten- ment and grafting. Many surgeons, however, openly op- sion and to minimize subsequent bony destruction and de- posed such aggressive surgical debridement in light of the formity. After decades of experience, this technique has extremely high mortality (30% to 70%) that resulted from been shown to be ineffective with an increased risk of mor- secondary infections [66,127,128]. The morbidity of open bidity and no benefit over chemotherapy alone for treatment surgery before antituberculous therapy was so high that of tuberculous infection [3,62,69,70]. As such, simple aspi- Calot [136] remarked in 1930, “The surgeon who, so far as ration or drainage of large abscesses is not indicated except tuberculosis is concerned, swears to remove the evil from for purposes of obtaining a tissue diagnosis. CT-directed bi- the very root, will find only one result awaiting him—the opsies using a fine needle have proven quite effective in death of his patient.” Despite these grim outcomes, the confirming the causative organism, thereby obviating the knowledge gained from these early pioneering efforts need for open spinal biopsy [140]. For rare cases where ag- would serve as the bedrock on which modern spinal surgery gressive debridement is not possible because of either ex- would be built [66,76,133,137,138]. After the introduction tensive disease or poor medical condition of the patient, ab-

138 L.T. Khoo et al. / The Spine Journal 3 (2003) 130–145 scess drainage can be accomplished by means of a limited tively and prospectively in the literature. Better outcomes transpedicular, costotransverse or retroperitoneal approach for deformity, disease recurrence, neurological deficit and [132,141]. disease elimination have been demonstrated [67,106,108, More aggressive drainage and excision of infected foci 111,144–148]. The results of the MRC’s controlled long- without fusion was commonly performed worldwide for term trial comparing the Hong Kong operation, simple de- similar reasons [32,139]. By removing all bony and soft tis- bridement and medical treatment alone, demonstrated that sue sequestra and opening new vascular channels, exci- 1) anterior bony fusion occurs earlier and in a higher per- sional therapy was shown to reduce general toxemia and to- centage of patients undergoing the more radical operation tal time to disease remission in the preantibiotic era [8,115]. (70% vs. 20% and 26%, respectively, at 5-year follow-up), Somerville and Wilkinson [142] retrospectively studied 130 2) kyphotic angulation was less common at 5 years, and 3) patients treated with excisional therapy without fusion and at 10 years, kyphotic angulation increased in the simple de- compared these results with 105 patients treated only with bridement group but stabilized and decreased in the radical antituberculous therapy; they could demonstrate no differ- debridement plus fusion group [26]. In their series of 412 ence in outcome. In response to these findings, Tuli et al. consecutive patients treated with this procedure, Hodgson et [9,61,115] suggested that only cases with progressive bony al. [144] had a mortality rate of 2.9% with no cases of de- destruction, increasing size of abscess, new neurological layed paraplegia. deficit, disease recrudescence and failure to respond to drug therapy should undergo excisional therapy. Subsequent pro- Surgical approaches spective MRC data have, however, shown no long-term benefit of focal debridement and abscess evacuation over Tuberculomas of the anterior craniovertebral junction that of ambulant chemotherapy alone [30,31]. Other authors and atlantoaxial region can be debrided through either tran- such as Neville [143] actually reported poorer outcomes for soral or extreme lateral approaches. These cases typically patients undergoing excisional therapy. As excisional ther- require concurrent occipitocervical fusion to prevent col- apy without fusion generally leaves a significant anterior lapse, instability and delayed deformity in this biomechani- column bony deficit, several studies have found an increased cally tenuous area of the spine [38]. Mid-cervical lesions rate of nonunion, progressive kyphosis, persistent draining are typically treated by means of standard anterior cervical sinuses and delayed neurological deficits in this group of approaches with excellent results (eg, Cloward and South- patients [3,65,89,124,143] Based on these considerations, it wick-Robinson) [49] or combined anterior and posterior re- would seem that excisional surgery without fusion should construction. Some authors have advocated approaches be performed only in rare circumstances. through the posterior cervical triangle, because abscess cavities in this region seem to have a propensity for dorsal extension [145]. For lesions of the cervicothoracic junc- Anterior surgical techniques tion, transsternal, transmanubrial, or lateral extracavitary Based on present MRC guidelines, radical ventral debri- approaches have been employed with varying degrees of dement, fusion and reconstruction of the vertebral column success [8,149–151]. In the thoracic spine, radical debride- remains the gold standard of surgical treatment for tubercu- ment and reconstruction can be accomplished through ei- lous spondylitis [4,26,30–37,46–48]. Although anterolat- ther a transthoracic, extrapleural anterolateral or extended eral decompression of the lumbar spine had previously posterolateral approach (eg, costotransversectomy, lateral been reported by other surgeons [8], it was Hodgson and extracavitary approach; Fig. 3) [26,38,152]. Extrapleural coworkers’ [67,111,144] experience that led to populariza- techniques afford the theoretical benefit of avoiding tuber- tion of radical anterior debridement or what is now known culous empyema, although there have been no data to sub- as the “Hong Kong” procedure. Although numerous vari- stantiate its superiority over standard thoracotomy [153]. ants of the Hong Kong operation have been described, the Because of the limited access afforded by posterolateral ap- hallmarks of the procedure are aggressive extirpation of all proaches, there may be increased risks of blind neurovascu- infected foci, thorough neural decompression and solid ar- lar and visceral injury, residual foci of abscesses and in- throdesis by means of bone grafting. Infected bone, caseous fected sequestra and a decreased rate of fusion because of a pus and sequestra must be aggressively extirpated back to smaller graft area available for arthrodesis. Compared with the level of healthy, bleeding bone. Leaving behind infected transthoracic approaches, costotransversectomy (lateral ra- sequestra can lead to disease recurrence and delayed defor- chiotomy) yielded a lower rate of solid fusion (78% vs. mity with neurological deterioration [131]. Decompression 95%) and a higher mortality rate (8% vs. 3%) [154]. How- for cases with neurological deficit should be carried to ever, more recent literature would suggest that wider poste- the level of dura, thereby increasing the chance of recovery rolateral exposures by means of lateral extracavitary ap- [3,68]. In cases where only debridement is required, the proaches might yield outcomes equivalent to that of posterior longitudinal ligament can be left intact [24,38]. transthoracic approaches [152]. In such regions as the high The success of radical anterior operation and concurrent thoracic spine, which are poorly accessed by means of tho- chemotherapy has been well substantiated both retrospec- racotomy, a lateral extracavitary procedure provides an ef-

L.T. Khoo et al. / The Spine Journal 3 (2003) 130–145 139 fective alternate approach. Larger degrees of kyphosis tend to allow better access through such posterolateral approaches, with better visualization of the dura. For the lumbar spine, the debridement and reconstruction is typically performed through a lateral retroperitoneal approach to afford maximal extensile exposure of the vertebral column and psoas musculature [67,111,144]. Anterior transperitoneal or retroperitoneal approaches used for lumbar interbody fusion operations typically are too restrictive in their exposure of the mid and upper lumbar spine to allow for safe debridement and reconstruction [155]. On the other hand, these approaches are well suited for access to the low lumbar and lumbosacral regions [124,125,156]. Supple- mental posterior sequential instrumentation and fusion is often necessary. Fig. 3 summarizes the operative corridors provided by these various approaches. Tuberculosis patients undergoing surgery frequently have a compromised immune system, depleted nutritional reserve and an overall poor potential for wound healing. As such, wound closure in such cases should be performed in multiple layers with interrupted nonabsorbable monofila- ment sutures to prevent chronic draining sinuses [38]. As infected exudates typically persist at the operative site for some time after surgery, it is desirable to have well-vascularized surfaces nearby to allow for effective antibiotic con- Fig. 4. This 45 year-old male presented with severe posterior thoracic pain, centrations and maximal reabsorption of fluids. Many sur- radicular numbness, and early myelopathy. Parasagittal non-enhanced T1- geons thus preferentially debride tuberculomas anteriorly to MR images demonstrated a kyphus of the mid-thoracic spine with collapse allow for drainage of the operative site to either the pleural of the intervertebral disc space and gibbus-type compression of the spinal or peritoneal surfaces [17,67,106,129]. cord (A, B). The patient was treated via a two-stage procedure with initial thoracotomy, radical ventral debridement, and autogenous rib grafting. Posterior hook-type instrucmentation was then applied. A lateral radio- Grafting considerations graph shows the rib-grafts in place with the final construct (C). The patient made a good neurological recovery with evidence of radiographic fusion After debridement, grafting should be performed to recon- and minimal kyphotic progession. struct the anterior support column of the spine, promote solid bony arthrodesis and ensure a successful fusion. In an MRC prospective study of 119 patients, 58 underwent radical anterior debridement with autologous grafting, whereas the other of rib graft during thoracotomy made their use popular in 61 had debridement alone. Fusion rates, nonunion rates and adults as well (Fig. 4). Clinical results have, however, been mean kyphotic angles were lower in the grafted group both at mixed in this population. In adults, Kemp et al. [149] demon- 5- and 10-year follow-up [30]. Traditionally, iliac crest, rib or strated a high incidence of delayed rib fracture (32%), partial fibular autologous grafts have been employed with reliable re- collapse and pistoning of the struts into the adjacent end plates. sults [30,58,67,146,149,154,157–159]. More recently, metal- When compared with full-thickness iliac crest grafts, rib seg- lic cage or mesh type devices containing nonstructural au- ments yielded a markedly lower long-term fusion rate (62% vs. tograft have also been successfully used [152]. The ideal graft 94.5%) and a higher mean increase in kyphosis as well (20 de- must provide strong support while bony arthrodesis occurs. grees). Similarly, Hodgson et al. [144], who exclusively used Fibular grafts provide excellent structural integrity but also iliac crest grafts in Hong Kong, reported a far lower amount of contain a large area of cortical bone that is slowly remodeled, delayed kyphosis and pseudoarthrosis. For these reasons, most often requiring several years to fully incorporate [160]. During experienced authors have advocated the use of full-thickness il- this time, the poorly vascularized necrotic matrix of the cortical iac crest for reconstruction of large defects with significant ky- bone may shelter microbes from antibiotics in the bloodstream, phosis [111,125,149]. The use of anterior compressive spinal thereby increasing the risk of persistent disease. For these rea- instrumentation as an adjunct to debridement and grafting has sons, Bradford and Daher [161] and Louw [162] have used been successfully described [163,164]. Others have cited poor vascularized rib grafts for stabilization in children and demon- bone stock, potential for progressive bone erosion from local strated significantly earlier incorporation (mean, 8.5 weeks) disease progression and fear of persistent hardware infection as and higher fusion rates. The ease of use and ready availability reasons to avoid the use of anterior instrumentation [24,38].

140 L.T. Khoo et al. / The Spine Journal 3 (2003) 130–145 Posterior surgical techniques an instrumented posterior fusion either preceded or fol- Although many patients often improve initially after de- lowed by an anterior debridement and grafting [62,68,172]. compressive laminectomy, neurological compromise typi- Moon et al. [71] reported on the use of posterior Harrington cally recurs without fusion as instability progresses. Bos- rod instrumentation as a first-stage procedure in 39 adults worth et al. [120] studied this phenomena in 14 patients with multisegmental spondylitis and obtained excellent decompressed with laminectomy with all unfused patients postoperative reduction of the deformity with minor long- dying. Laminectomy for tuberculous spondylitis should thus term loss of correction (less than 3 degrees). be reserved only for rare cases of isolated posterior neural Güven et al [173] have used single-stage pedicle-screw arch disease with posterior epidural compression [43,112,130]. type posterior instrumentation for cases of limited mono- For these cases, 60% to 90% can expect a good to fair result segmental spondylitis without paraplegia or extensive de- with those with lesser deficits, subacute disease and young struction and obtained good control of delayed kyphotic age faring the best [43,165]. Even for such cases, several progression as well (less than 3.4 degrees). Compared with experienced authors recommend a subsequent instrumented prior hook-type or sublaminar wire-type constructs, trans- fusion to prevent delayed kyphotic progression and neuro- pedicular fixation has been shown to be biomechanically far logical deterioration [8,24,166]. For Pott disease, posterior superior with regard to rigidity, stiffness, torsional strength spinal operations thus continue to play a pivotal role in the and its ability to maintain the correction of deformity treatment of kyphosis for both prevention and correction of [65,71,72,106,152,173]. However, large postdebridement the deformity. defects should still be grafted after transpedicular fixation to There is evidence that young children are at particular ensure adequate ventral column support. In such instances, risk of progressive kyphosis after successful anterior recon- posterior instrumented correction without anterior grafting struction because of persistence of growth in the posterior can lead to corporal collapse, failed union, pseudarthroses, spine despite anterior arrest. Posterior in situ arthrodesis ei- hardware breakage and progressive kyphosis [3,71,72]. Use ther prophylactically or as a salvage procedure has been of distraction maneuvers without anterior support further in- advocated by several authors to treat this skeletal growth creases the possibility of these complications. Hooks and imbalance. Schulitz et al. [167] followed 117 children oper- sublaminar wire fixation should be used where transpedicu- ated for Pott disease with either anterior or posterior nonin- lar fixation is not possible. Examples of this include tho- strumented fusions. At 10 years, the anterior fusion group racic vertebrae with very small pedicles, severely os- had a mean kyphotic increase of 12 degrees, whereas the teoporotic bone and incompetent pedicles from either combined anterior-posterior fusion group actually experi- erosion or prior fracture. Long-segment constructs can often enced an improved correction of 7 degrees. On the other exert excessive lever-arm moments at the ends of the im- hand, such authors as Bailey et al. [58], Fountain et al. plants, thereby also increasing the risk of screw pullout. Use [168], and Upadhyay et al. [148,169] have reported a much of hooks or sublaminar wires at the termini of the construct lower incidence of late kyphotic progression in children af- can help to prevent this (Fig. 4). ter successful anterior debridement and fusion. Of note, Surgical correction of a severe kyphotic deformity however, is that these authors typically included children (greater than 30 degrees) will often require posterior tech- who were older than the cohort of Schulitz et al. Neverthe- niques that are more complex and technically demanding. less, it is prudent to follow children closely after anterior re- Smith-Peterson et al. [174] first described a posterior closed construction so that posterior fusion can be performed when wedge osteotomy in 1945 with V-shaped resection of a por- needed to arrest progressive kyphosis [24,170]. tion of the posterior arch and a subsequent closure in exten- In adults, posterior instrumented techniques have also sion. With this technique, Simmons [175] was able to been used to prevent delayed deformity as well as to pro- achieve an average of 56 degrees of correction in kyphotic mote fusion and prevent kyphotic progression after anterior lumbar deformities. However, use of this type of closing os- reconstruction. Several authors have expressed dissatisfac- teotomies necessitates anterior grafting, because a large de- tion with the ability of anterior grafting alone to correct pre- fect is created ventrally after extension. In the classic operative kyphosis and to prevent delayed deformity Galveston one-stage posterior closing wedge osteotomy, a [3,62,69,70,124]. A significant loss of gibbus correction has modified bilateral costotransversectomy approach to the often been observed within the first 6 to 24 months after spine is performed to allow for wedge-shaped resections of radical anterior debridement and fusion [171]. This has been the vertebral arch, intervertebral disc and a portion of the particularly true for cases involving larger defects more body centrum. Once this wedge of bone has been removed, than two disc spaces in size where over 25% of patients may the posterior and middle columns of the spine are preferen- have late kyphotic angles over 20 degrees [124]. Thoracic tially shortened, thereby allowing for angular corrections of lesions, marked preoperative kyphosis and the use of rib 30 to 50 degrees [116]. Because there is bone-on-bone con- grafting have also been associated with more severe late de- tact ventrally, the need for anterior reconstruction is obvi- formity after anterior surgery [38]. For such cases, some ated unless there is a need for either debridement or decom- surgeons have advocated use of a two-staged approach with pression. The decancellation or corporal eggshell technique

L.T. Khoo et al. / The Spine Journal 3 (2003) 130–145 141 of Thiranont and Netrawichien [89] can also be used to sparingly as a second-line of defense. For cases of spondyli- achieve excellent correction of kyphosis as well. As the pro- tis uncomplicated by significant kyphosis, unresponsive cedure involves transpedicular curettage and evacuation of sepsis, questionable diagnosis or neural deficit, early detec- the vertebral body’s cancellous bone in addition to excision tion and medical treatment should always be the mainstay of the posterior elements, this operation carries additional of management. Only when progressive deformity, neurosurgical risks [173,176]. Surgical morbidity and mortality logical deficit or incapacitating pain/dysfunction ensue can be significant for these technically demanding proce- should the spine surgeon be prepared to intervene. dures, with an 8% to 10% incidence of postcorrection neurological complication [3,173–175]. 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Four Galen. His insistence that cadaver dissection be an essential part of the education of physicians fueled a contro- Hundred versy that lasted for centuries. The extraordinary beauty of the illustrations not only served to establish the au- Sixty thority of the science but also became treasures of art. Years Ago Who should be credited with the original illustrations is an unresolved topic of scholarly debate. in Spine . . .

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