The erythrocyte sedimentation rate (ESR) and gram stain and culture are the commonly used laboratory tests in the diagnosis of pyogenic spine infections [30]. C-reactive protein (CRP) has been shown to be helpful in the diagnosis of infection and has supplanted ESR as the laboratory study of choice for assessing the presence of infection [31]. Koo et al. [29] described that the ESR and CRP level were significantly higher in the patients with pyogenic spondylitis than tuberous spondylitis. Polymerase chain reaction has been used to rapidly identify the presence of mycobacterium in formaldehyde solution-fixed, paraffin-embedded tissue specimens [32].

The earliest and most common radiographic finding is narrowing of the disc space in pyogenic spondylitis. It is due to the disc destruction by proteolytic enzyme and is followed by irregularity of endplate from the bone destruction. In progression and healing of the disease, osteolytic changes are followed by new bone formation and osteosclerotic changes at the vertebral margins [21,23]. The findings of plain radiographs for tuberous spondylitis may vary depending on the pathologic type and chronicity of the infection. In early tuberous spondylitis, the disc space is preserved more than pyogenic spondylitis from the lack of proteolytic enzyme. Radiographs may show osteoporosis of body and irregularity of endplate, among others.

MRI has been reported to be beneficial for early diagnosis and differential diagnosis of the spondylitis and is being extensively used for diagnosis [1,7,33,34,35]. The typical MRI findings of acute vertebral myelitis are low signal intensity in the T1-weighted images and high signal intensity in the T2-weighted images, due to edema of bone marrow in the infected area. However the value of differential diagnosis is low, as there is no specific difference in the contagious causes. In the chronic progress with delayed diagnosis, high signal intensity is sometimes shown in the T1-weighted images [3,34,36,37]. In addition low signal intensity is shown in both T1 and T2-weighted images, if vertebral body has progressed to a collapse and has irregular endplate sclerosis. Hence contrast enhancement images of the gadolinium are specifically required [3,37]. As the MRI is generalized, specific opinions that are beneficial to differential diagnosis of tuberculous spondylitis are being reported by various authors (Figs. 1, 2). Representative opinions deal with abscess in the vertebral body showing contrast enhancement in the peripheral rim, erosion of vertebral body surface, paraspinal abscess with relatively clear border that shows contract peripheral enhancement, extension of anterior longitudinal ligament of the inflammatory tissue and relatively preserved disk [8,34,38,39]. As for tuberculous spondylitis, it typically starts from the anterior cancellous bone in the vertebral body followed by vertebral body starting to be destructed, extending beneath anterior longitudinal ligament and creating an abscess near the vertebral body [1,3,40]. Many of the studies dealing with tuberculous spondylitis have reported that abscess involves uniquely multiple vertebral bodies, especially in gadolinium-enhanced MRIs [34,35,41]. Chang et al. [41] has reported that aforementioned form of contrast enhancement is completely shown in tuberculous spondylitis. Destruction of vertebral bodies in tuberculous spondylitis entails more of such contrast enhancement. It is assumed that abscess is formed more and also available to be used for beneficial indices when performing a differential diagnosis. Epidural extension and epidural abscess formation have been reported to be observed more in tuberculous spondylitis [35,41]. As for paraspinal abscess formed in tuberculous spondylitis, contrast enhancement is known to be more easily performed in the rim of abscess, with the importance of a differential diagnosis [4,41]. In other words, paraspinal abscess is frequently found in pyogenic spondylitis; but well-defined paraspinal abnormal signal, thin and smooth abscess wall and presence of paraspinal or intraspinal abscess are more suggestive of tuberculous spondylitis than of pyogenic spondylitis. On the other hand, if the wall of abscess is relatively thick entailing irregular contrast enhancement, it has been reported to be implying pyogenic spondylitis [30,34,42]. Chang et al. [41] has reported that cases with grade 3 or above and destructed more than 50% of vertebral body height were observed in 82% of all cases in tuberculous spondylitis. Such was observed in 30% of the cases in pyogenic spondylitis. It was concluded that vertebral body was damaged more severely in tuberculous spondylitis than in pyogenic spondylitis. On the other hand, it has been reported that disc is damaged more frequently in pyogenic spondylitis [41,42]. Lack of proteolytic enzymes in Mycobacterium as compared with agents of pyogenic infection has been proposed as the cause of the relatively preserved intervertebral disc, found totally sequestered within the involved vertebrae [1,3,12]. Chang et al. [41] has reported that 57% of a disc was preserved in tuberculous spondylitis, while only 3% was preserved in pyogenic spondylitis. A summary of data regarding the radiologic findings is in Table 2 [4,41].

Conservative management consists of antimicrobial therapy and non-pharmacological treatments, including physiotherapy and immobilization. Immobilization through bed rest is for pain control and prevention of deformity or neurologic deterioration. Length of time for bed rest, type of orthosis and duration of its use depend on location of the infection, degree of bone destruction and deformity and response to treatment. While initial antimicrobial therapy is almost always administered parenterally, its duration varies considerably. In several studies, the mean parenteral treatment duration is at least from 4 to 6 weeks, followed by oral conversion treatment [11,12,20,43,44]. At present, it is recommended that parenteral antibiotic therapy be used in maximal dosage for 6 weeks and followed with an oral course of antibiotics until a resolution of the disease. Criteria for discontinuation of antimicrobial treatment include symptom resolution or improvement and the normalization of ESR or CRP [20,45].

In tuberculous spondylitis, multiple drugs are used because of the potential for resistance to a single agent. Selection of rational combinations of drugs is based on the mechanism of action and toxicity of the agents. A 6-month three-drug regimen including isoniazid, rifampin and pyrazinamide is used for most cases of drug-sensitive infection [24,46].

A surgical treatment is required in the following: to acquire bacteriological or histological verification; if there is severe pain; if clinically important abscess is formed; if there is no response after injecting an appropriate antibiotic; if spine is deformed or such needs to be prevented due to a severe damage to the bone; or if there is neurological paralysis [38,47,48,49,50]. An operation may be performed to drain abscesses, to debride sequestered bone and disc, to decompress the spinal cord or to stabilize the spine for the prevention or correction of deformity. There is a broad range of options for the surgical management of spinal infections, which include anterior or posterior approach, single-stage or two-stage surgery and with or without instrumentation. Chen et al. [48] has described a tendency toward a decrease in the incidence of infection recurrence and revision surgery with combined approach as compared with other approaches. Single-stage surgery has advantages including lower complication rate, shorter hospital stay and early mobilization. The two-stage surgery has shorter operation time, less blood loss and increased safety for patients with poorer general health [51,52]. The efficacy of the two-staged operation did not differ between the patients with pyogenic and tuberculous spondylitis [53].

In most cases, the spine should be approached anteriorly, as it allows direct access to the infected tissues and adequate debridement. The use of titanium mesh cages may provide better anterior column support, because their structural integrity is not affected by degradative enzymes present in an infection environment. Interestingly bacteria show lower propensity of adherence to titanium compared with stainless steel [54,55,56,57]. The addition of posterior instrumentation provides even better deformity correction and faster rate of fusion and does not appear to increase the risk of infection [54]. Single-stage anterior and posterior surgery has been shown to be safe and effective using titanium implants [55,56]. Recent advances in minimally invasive spine (MIS) techniques offer alternative methods of surgical treatment. Korovessis et al. [58] showed in a small number of patients that anterior debridement and reconstruction with titanium mesh cages followed by posterior MIS screw fixation led to decreased blood loss and shortened operative time.

In tuberculous spondylitis, most authors agree that anterior radical debridement and strut graft fusion is superior. The spine is approached anteriorly so that the affected area may be dealt with most directly. Oga et al. [59] evaluated the adherence properties of M. tuberculosis and S. epidermidis to stainless steel. The Staphylococcus heavily colonized the rods and was covered with a thick biofilm, whereas only a few biofilm-covered colonies of M. tuberculosis were seen. These findings have prompted the use of anterior instrumentation at the time of initial anterior debridement. Some authors recommend that a posterior fusion should be performed in addition to an anterior fusion in order to eliminate the risk of increased deformity [60,61,62]. Anterior grafts may not provide stable fixation, especially in cases where the graft spans more than two-disc spaces [63].