Paraplegia is the most serious complication of spinal TB, mainly due to direct mechanical spinal cord compression as a result of an expanding abscess, caseous necrotic material, TB granulation tissue and bony elements [7]. Other mechanisms, such as instability, meningitis, infective thrombosis of spinal vessels and some adverse changes in the spinal cord have also been implicated for the worsening of neurological status [8]. The classification for paraplegia in spinal TB includes early onset paraplegia (active spinal TB) and late onset paraplegia (healed spinal TB), as proposed by Hodgson et al. [9]. Early onset paraplegia for spinal TB is mainly caused by soft pressure (pus, caseous necrotic tissue and tuberculous granuloma) of the spinal cord resulting in slow, continuous and gradual compression. Late onset paraplegia for spinal TB is mainly caused by rigid pressure (kyphotic bone ridge, granulomatous scar and contracture) [10]. All cases included in our series are early onset paraplegia patients, as determined through radiological presentation and operation findings, with the materials which caused spinal cord compression in our series mainly being soft materials, such as fluid pus, proliferous granuloma and osteolytic bony destruction. Therefore, this finding is consistent with that of previous literature reports. Due to the short period of spinal cord disturbance, no signals of spinal cord denaturation, necrosis and malacia were detected through MR examination. However, epidural adhesion was identified in most patients, resulting in a higher rate of dural tears and cerebrospinal fluid leak.
Paraplegia as a result of spinal TB is always incomplete and can be cured or improved. Some scholars have suggested that early onset paraplegia can be cured through conservative anti-TB drugs management because the spinal cord pressure is soft and is easily absorbed under effective anti-TB drugs treatment [11]. However, many experts deemed that irreparable damage to neurological impairment may occur as a result of long periods of anti-TB drug conservative treatment. Therefore surgical intervention needs to be administered only when suitable [12, 13]. The principle of surgical intervention is to effectively and safely relieve neural pressure, maximizing the decrease of the infectious burden, and reconstructing spinal stability, while minimizing damage to the physical body. Until now, the timing of surgical intervention suitable for paraplegia of spinal TB has been disputed [14]. Batirel et al. [15] believed that paraplegia caused by spinal TB is a slowly developing process, and a short delay in surgical decompression may not change the final level of recovery of neurological function. Wang et al. [16] and Chandra et al. [17] considered a period of 2–4 weeks of normal quadruple anti-TB drug treatment before operation is advocated, but stated that emergency operation is needed as neurological impairment progresses. Zhang et al. [18] stated that surgery can be performed after a significant decrease of ESR and CRP has been observed. For our series, early operation was defined as operation carried out within 3 weeks of paraplegia. We found significant neurological function improvement together with other positive indexes after early surgery.
This study sample included 104 cases of incomplete paraplegia, of which 95 cases (91.3%) fully recovered, and 14 cases of complete paraplegia, of which only 2 cases (14.3%) fully recovered. The cure rate of incomplete paraplegia was significantly higher than that of complete paraplegia. Some experts have been concerned that early surgical intervention may lead to systemic TB dissemination. In our series, insignificant elevation of ESR and CRP values were transiently observed after surgery, and no cases of disseminated TB were observed during the hospitalization period and subsequent follow up. Anterior approach is commonly used in spinal TB and has some merit for debridement and interbody fusion; however it is less accessible for spinal canal decompression [19]. Li et al. [20] reported that effect of single anterior debridement decompression, autogenous rib grafts, and instrumentation are good for spinal TB. Varatharajah et al. [21] reported that anterior surgery is beneficial for debridement and kyphosis correction, but results in low maintainability of kyphosis correction. A single posterior approach is mainly used for treating spinal degenerative diseases.
In recent years, many scholars have reported of successful results from single posterior surgery for spinal TB. For patients with spinal TB paraplegia, spinal cord decompression is more accessible through a posterior approach, thus the single posterior approach is a suitable choice for cases of spinal TB paraplegia with small prevertebral abscesses [22]. Ukunda et al. [23] found that the posterior-only surgical approach is advantageous for kyphosis correction and disability improvement. Zhang et al. [24] reported that posterior debridement, fixation and interbody fusion are safe and effective methods for patients with upper thoracic spinal TB. In our series, most cases (78%) received a single posterior approach and the relapse rate was very low (2.2%). Therefore, the therapeutic effect of the single posterior approach for spinal TB paraplegia was found to be excellent. For cases with large prevertebral abscesses, the procedure of posterior decompression and fixation combined with two stage anterior debridement and interbody fusion was chosen, and no cases of relapse were reported during the follow-up period. Therefore, we believe that a preoperative CT scan or MRI is essential for choosing the appropriate method of surgery. Additionally, we considered that a postoperative CT scan or MRI is also important for deciding whether two stage anterior surgery is necessary or not. If the paravertebral pus has not been cleared and drained well after single posterior surgery, then an additional two-stage anterior debridement was advocated due to decreased probability of TB relapse and faster healing of TB lesions [25, 26]. Kyphotic correction is also an important index for therapeutic evaluation, and in this study, significant correction of kyphotic Cobb’s angle was achieved after operation and good alignment was maintained during the follow-up period. Therefore, early surgical intervention is not only results in faster neurological recovery but can also achieve excellent kyphotic correction and sustainment.
This study has some innate limitations. It is not a prospective study, and therefore did not include a control cases and included only a small number of cases. Therefore, the conclusion need to be verified through further studies.