Midterm surgical results of the lamina with spinous process in treating one-level thoracic or lumbar tuberculosis: a retrospective study

A retrospective study investigated the results of the lamina with spinous process (LSP) as a bone graft in one-level thoracic or lumbar spinal tuberculosis with the one-stage posterior approach of debridement, fusion and internal instrumentation. Data from 35 patients from January 2013 to December 2015 were analysed. Surgery time, blood loss, hospitalization time, drainage volume, and follow-up (FU) duration were recorded. The visual analogue scale (VAS), Oswestry Disability Index (ODI), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), American Spinal Injury Association (ASIA) grade, segmental angle, and bone fusion were compared between preoperative and final FU. All of the patients were followed up for a mean 43.90 ± 10.39 months. The mean age, surgery time, blood loss, hospitalization time, hospital cost and drainage volume were 33.65 ± 11.06 years, 182.40 ± 23.82 min, 280.80 ± 76.82 mL, 14.05 ± 3.58 days, 74,382.00 ± 11,938.00 yuan, and 340.00 ± 167.20 mL, respectively. VAS and ODI were significantly improved at the final FU. The ESR and CRP recovered to normal. The mean angle of 24.35 ± 5.74°preoperatively showed a significant difference between 1 week, postoperatively and final FU. Although there were the loss of angle at final FU comparing with the 1 week postoperatively, it still maintain the good alignment and the segmental stability. All patients achieved bony fusion with a mean time of 12.90 ± 3.91 months. In conclusion, the LSP as a structural bone graft is reliable, safe and effective for segmental stability reconstruction, which could be one choice for surgical management of thoracic or lumbar spinal TB.


Materials and methods
Patient population. This study was approved by the Institutional Review Board of the First Affiliated Hospital of Chongqing Medical University and conducted in accordance with the Declaration of Helsinki. All participants provided written informed consent before their data were stored in our hospital database and used for study purposes. The treatment plans were all developed while providing routine clinical care. When communicating with patients before surgery, the advantages and disadvantages of the possible approaches were fully explained to the patients and their family members, so the patients could choose the right treatment for themselves. From January 2013 to December 2015, in the spine unit of our department, the data from 35 patients with one-segment thoracic or lumbar spinal TB were reviewed retrospectively. The surgery procedure was performed by the same spine team for all patients.
The inclusion criteria were adult thoracic or lumbar spinal TB, one-stage posterior approach, and internal instrumentation and reconstruction. The patients were indicated for surgery because of the following: increasing kyphosis, neurological deficits, bone destruction affecting spine stability, and the bone damage of the infected vertebral body did not exceed 1/2 the vertebral height of the thoracic spine and did not exceed 1/3 the vertebral height of the lumbar spine. The exclusion criteria were active pulmonary TB, spine fractures and spine cancer.
Preoperative management. Once the clinical diagnosis was made, anti-tuberculosis chemotherapy was given immediately. Anti-TB drugs in the HREZ standard programme include isoniazid (5-10 mg/kg/ day), rifampicin (10 mg/kg/day), ethambutanol (15 mg/kg/day) and pyrazinamide (25 mg/kg/day), which were administered 3-4 weeks before surgery 2,10 . Surgery was performed when ESR, c-reactive protein (CRP), and body temperature recovered to normal or decreased significantly, or when ESR decreased below 60 mm/h and CRP decreased gradually. When the neurological dysfunction gradually worsened and anti-TB drug therapy failed, we shortened the duration of drug therapy and considered emergency surgical treatment.

Surgical techniques.
After the administration of general anaesthesia, the patients were placed in the prone position. Posterior segments of the spine, such as the lamina and facet joints, were exposed through a median incision. Pedicle screw fixation was performed according to imaging and c-arm X-ray results to ensure accuracy. The entire LSP was cut off using a sharpened drill or ultrasonic osteotome, and then one of the facet joints was removed for decompression and radical debridement. The LSP was trimmed by a bone knife, a sharpened drill, or an ultrasonic osteotome to obtain a suitable and three-cortical-sided bone graft (Fig. 1). Depending on the remaining space, one LSP was trimmed suitably, before the implantation of LSP, a few of autologous granular bones were filled in the bone defect and afterward, the instrumentation was locked with force. Gelatine was used locally mixed with 1.0 g streptomycin and 0.2 g isoniazid. Negative pressure drainage was performed, and the collected specimens were sent for bacterial culture and pathological findings.
Postoperative care. After the surgery, the oral chemotherapy regimen (12 HREZ/12-18HRE) for the patients must be followed up strictly with the physician, paying close attention to the side effects of the anti-TB drugs and adjusting the drugs and treatment in a timely fashion when they occurred. Walking training under the guidance of a rehabilitation therapist was started 1 week after the surgery. Clinical and imaging examinations for all of the patients were performed at 1 week, 3 months, 6 months, 12 months and then annually after surgery. All radiographic data and measurements in our study were reviewed by one senior spine surgeon and one senior radiologist.

Statistical analysis. The statistical analysis was performed using Statistic Analysis System (SAS Institute
Inc., Cary, NC, USA). The results are expressed as the mean ± SD and Student's t-test was performed. Differences with P values < 0.05 were considered statistically significant.

Results
All of the patients were followed up for a mean 43.  Fig. 2). The neurological impairments were improved significantly at the final FU using ASIA grading ( Table 2). The thoracic spinal TB was well cured and all patients achieved bony fusion at a mean 12.90 ± 3.91 months. The mean angle of 24.35 ± 5.74° preoperatively showed a significant difference between 1 week postoperatively and final FU. Although there were the loss of angle at final FU comparing with the 1 week postoperatively, it still maintain the good alignment and the segmental stability (Figs. 3, 4). One case of rod fracture was observed 2 years postoperatively, and the revision surgery was performed with an iliac graft (Fig. 5). Some postoperative complications occurred, such as water-electrolyte imbalance (two cases) and superficial infection (two cases).

Discussion
With the rising incidence of TB, there are more than eight million new cases of tuberculosis each year, with it remaining a leading infectious disease cause of death globally 1-3 . Spinal TB is the most common and severe form of osteoarticular TB. Formal adequate and long-term anti-tubercular drugs, bed rest and supportive nutrition are necessary in the management of spine TB 4-6 . Despite the efficacy of conservative regimens, surgical treatment is still recommended for patients with bone destruction, sequestration, a paraspinal or spine canal abscess, or neurological impairment. Surgery, such as the single-stage anterior approach, can be challenging to apply because of the need to overcome severe trauma such as massive blood loss, a longer operation time, and more serious complications. A posterior pedicle screw system with bone grafting and correction of the kyphotic deformity has been widely applied for stabilization, effectively treating thoracic or lumbar spinal disorders. Hence, the principles of management of spinal TB have been modified to allow them to become more accurate and individualized 7-13 .    www.nature.com/scientificreports/ After surgical debridement and decompression of the spinal cord or nerves, a variety of intervertebral bone grafts can be used to restore the stability of the anterior and middle columns. Iliac crest or fibula grafts, considered the "gold standard", could achieve a high rate of bone healing. However, complications at the donor site, such as persistent pain, haematoma, and unhealed wounds, can also occur. The use of allografts can avoid complications, but their use is associated with an increased rate of graft failure and the risk of disease transmission. Autologous bone grafts with a titanium mesh cage have been widely used, and they have a high bone fusion rate. However, problems such as subsidence, stress occlusion, and radiation opacity can affect surgical planning [14][15][16][17][18][19][20] . Although the transverse process had advantages of reducing trauma, shortening hospital stay, the bone defects caused by the lumbar spine TB are larger than these in thoracic spine which the transverse processes of lumbar spine have deeper anatomical characteristics limited by difficulty in being exposed and which the mechanical requirements of lumbar spine are higher than thoracic spine [21][22][23][24] . Therefore, this study aimed to find a new method of bone grafting to provide support and promote bone fusion to reduce the incidence of complications.
The use of the LSP as the bone graft has the following advantages. First, in our study, the surgery time in minutes, blood loss, hospitalization time, hospital cost and drainage volume were 182.40 ± 23.82 min, 280.80 ± 76.82 mL, 14.05 ± 3.58 days, 74,382.00 ± 11,938.00 yuan, and 340.00 ± 167.20 mL, respectively. Compared with the iliac crest or fibula graft used in previous studies [17][18][19][20][21][22][23][24] , the use of the LSP could reduce trauma and bleeding, shorten surgical and hospitalization times, decrease postoperative drainage volumes, and reduce postoperative complication rates. The LSP are present in the surgical exposure area during the posterior approach, which can reduce bleeding and trauma. Second, in our study, all patients achieved bony fusion at a mean 12.90 ± 3.91 months. The mean angle of 24.35 ± 5.74° preoperatively showed a significant difference between 1 week postoperatively and final FU. Although there were the loss of angle at final FU comparing with the 1 week postoperatively, it still maintain the good alignment and the segmental stability. Furthermore, the VAS and ODI were also improved during FU, and thus, the patients recovered soon after surgery and VAS and ODI were significantly improved at the final FU. Hence, the use of LSP could achieve biomechanical stability and satisfactory clinical efficacy. Although the LSP could provide good support, strength, and fusion properties, the bony fusion time was long compared with other bone grafts, which could have caused the segmental angle loss. One case of rod fracture was observed at 2-year FU because of the bone union.
Hence, the LSP, as an autogenous bone, has a cortical bone structure and is short on cancellous bone tissue. The use of the LSP could be suitable for supporting the bone defect space, which could ensure and maintain the segmental stability and could be one more choice for the surgerons, However, using a single LSP as a bone graft had a risk of delayed bony fusion or even nonunion, and therefore it could be suggested that longer use of a brace is necessary while the bone is not fully healed during the FU.

Conclusion
Our study results showed that use of the LSP as a bone graft could be one choice in the surgical management of one-level thoracic or lumbar spinal TB, resulting in good bone fusion and spinal stability restoration. It is a reliable, safe, effective and structural bone grafting method. However, we declare that the retrospective nature of this small-sample study may be associated with bias. Second, although we are the first to report the use of LSP as a structural bone graft, the use of a single LSP as a bone graft had a risk of delayed bony fusion or even nonunion. Third, our study did not consider intra-and inter-observer differences, which are associated with bias. Fourth, we need to perform biomechanical tests to determine differences in strength, which could confirm that the LSP meets the biomechanical needs. In the future, prospective, randomized studies with long-term follow-up are needed.