Treatment of single-segment lumbar tuberculosis by unilateral biportal endoscopic debridement, interbody fusion, and percutaneous pedicle screw fixation

doi:10.21203/rs.3.rs-4945137/v1

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Treatment of single-segment lumbar tuberculosis by unilateral biportal endoscopic debridement, interbody fusion, and percutaneous pedicle screw fixation

https://doi.org/10.21203/rs.3.rs-4945137/v1

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Introduction: Unilateral biportal endoscopic (UBE) technique is an emerging minimally invasive spinal surgical technique that has been used to treat a variety of degenerative spinal diseases in recent years, while there are rare reports on the treatment of lumbar tuberculosis (LTB). Consequently, this study intends to investigate the effectiveness and feasibility of UBE debridement, interbody fusion, and percutaneous pedicle screw fixation for single-segment LTB.

Methods: A total of 31 patients with single-segment LTB from January 2020 to September 2021 were included. The operative time, estimated blood loss, time to ambulation, postoperative hospital stay, and complications were recorded. Clinical outcomes include erythrocyte sedimentation rate (ESR), c-reactive protein (CRP), the visual analog scale (VAS) score, Oswestry disability index (ODI), American Spinal Injury Association (ASIA) neurological classification, Cobb angle, and lumbar

lordotic angle were analyzed. X-rays or computerized tomography (CT) were reviewed 6 months after surgery and at the final follow-up, and surgical segmental fusion was evaluated using Bridwell grading criteria.

Results: The mean operative time was 171.61 ± 19.03 minutes, the mean estimated blood loss was 243.87 ± 26.54 ml, the mean time to ambulation was 1.87 ± 0.76 days postoperatively, and the mean postoperative hospital stay was 5.61 ± 1.17 days. There were 4 cases of procedure-related complications and the incidence was 12.9%. The levels of ESR and CRP returned to normal 3 months after the procedure. VAS scores of low back and leg, as well as ODI, were significantly improved postoperatively compared with before the operation, and the differences were statistically significant (P < 0.05). All patients were ASIA grade E at the last follow-up. The postoperative Cobb angle was 9.81 ± 2.4^°, the lumbar lordotic angle was 42.59 ± 6.16^°, and both had no significant loss of correction during the final follow-up. Bony fusion was achieved in all cases at the final follow-up.

Conclusions: UBE debridement, interbody fusion, and percutaneous pedicle screw fixation is a feasible, effective, and safe surgical procedure for the treatment of single-segment LTB.

Health sciences/Diseases/Infectious diseases/Tuberculosis

Health sciences/Health occupations/Orthopaedics

Biological sciences/Microbiology/Clinical microbiology

Unilateral biportal endoscopy

Percutaneous pedicle screw fixation

Minimally invasive surgery

Lumbar tuberculosis

Spinal infectious diseases

Spinal tuberculosis (TB) is an infectious disease of the spine characterized by bone destruction, fractures, and deformities, accounting for approximately half of osteoarticular TB ¹. Anti-TB drug chemotherapy is the main method to treat lumbar tuberculosis (LTB) and has excellent efficacy, while medical therapy alone is usually insufficient when patients with persistent low back pain, neurological dysfunction, spinal instability, and severe or progressive kyphotic deformity. Therefore, it is extremely necessary for patients with LTB to have a surgical intervention, which the goals of surgery are to remove infected lesions, prevent or treat neurological impairment, as well as correct and prevent the progression of spinal deformity ². At present, the main surgical approaches include anterior debridement, traditional posterior open surgery, and combined anterior and posterior approaches ³, while these surgical approaches have pros and cons, there is no consensus on the optimal surgical method for LTB ⁴.

With the development of surgical techniques, minimally invasive surgery has become increasingly popular in recent years. Unilateral biportal endoscopic (UBE) is an emerging minimally invasive technique that is widely used to treat degenerative spinal diseases because of its advantages of operative freedom, large working space, broad surgical field, and can use of basic spinal surgical tools ^5,6. Currently, some scholars have also attempted to apply this technique to treat spinal infectious diseases, such as epidural abscess, and suppurative spondylitis⁷. Nevertheless, to our knowledge, the UBE technique for LTB has been reported rarely. Consequently, this study was conducted by retrospectively analyzing this group of cases and evaluating the clinical outcomes, which the goals were to investigate the effectiveness and feasibility of UBE debridement, interbody fusion, and percutaneous pedicle screw fixation in the treatment of single-segment LTB, and summarized the surgical points and precautions.

General information

The study protocol was approved by the Ethics Committee of our Hospital and performed according to the Declaration of Helsinki. A total of 31 patients (18 males and 13 females) were diagnosed with LTB and underwent UBE debridement, interbody fusion, and percutaneous pedicle screw fixation from January 2020 to September 2021 in our institution were included in this study, and all patients were informed of the potential risks of the procedure and signed written consent preoperatively. Inclusion criteria: (1) patients diagnosed with LTB; (2) the age range is 18 to 65 years; (3) patients with intractable low back pain that is not relieved by anti-tuberculosis medications, and/or the presence of severe or progressive neurological dysfunction; (4) imaging showed a single-segment lesion with massive epidural abscess, with/without bone destruction, and no severe spinal deformity (Fig. 1a-e); (5) the patients who underwent UBE debridement, interbody fusion, and percutaneous pedicle screw fixation; (6) complete clinical data and the postoperative follow-up period was more than 12 months. Exclusion criteria: (1) patients with active tuberculosis that is not effectively controlled and is highly infectious ⁸; (2) other spinal diseases(eg. other spinal infections, spinal trauma, and spinal tumors); (3) lesions involving two or more segments; (4) the patients unable to tolerate surgery.

Preoperative preparation

Anti-TB drugs using the HRZE chemotherapy regimen, which include isoniazid (0.3g/d), rifampicin (0.45g/d), pyrazinamide (30mg/kg·d), and ethambutol (15mg/kg·d) were administered 2–4 weeks before the operation. The procedure was performed when the patient's temperature and ESR were significantly decreased or normal.

Surgical procedures

All operations were performed by a team of physicians. The patient was placed in a prone position under general endotracheal anesthesia, the lesioned segment was identified and 2 portals were marked under C-arm fluoroscopy guidance, and then the skin was sterilized, and the waterproof sterile draping and skin care membranes were used. Two K-wires were inserted into the marked portals under fluoroscopy to confirm the disc space at the level of the lesion. Two portals were created for the operation, which were located 1 cm above and 1 cm below the center where the junction of the K-wires was located, and close to the outer side of the pedicle. The distance between the two portals may vary depending on the level and height of the patient, but the cranial portal is located approximately 2 cm above the caudal portal. Two longitudinal incisions of about 1.5 cm were made to introduce the arthroscope and instruments. For the left-side approach, the arthroscope was inserted using the cranial portal as the viewing portal and the various instruments were inserted using the caudal portal as the working portal (Fig. 2a-b), whereas the opposite was true for the right. The lower end of the upper lamina and interlaminar space as landmarks for laminectomy were identified using a shaver (Fig. 2c). Laminectomy was performed using a high-speed burr, and concomitant contralateral laminectomy was performed for those with bilateral symptoms or a high number of epidural abscesses, followed by the bilateral flavectomy was performed using pituitary forceps and Kerrison punches. Localized healthy autologous bones collected were retained for use as interbody grafts. Hyperplastic vessels were visible after the dura and nerve roots were slightly drawn toward the midline with a special retractor by an assistant (Fig. 2d), carefully hemostatic by radiofrequency and discectomy was performed using tools, and lesioned nucleus pulposus was identified (Fig. 2e). The arthroscope was introduced into the intervertebral space to monitor the preparation of the endplate and lesion clearance. The residual lesion tissue and nucleus pulposus were completely removed, the pus in the spinal canal and around the vertebral body were cleaned, and the sequestrum and the cartilaginous endplate were removed with a curette to exposethe subchondral bone until the wound had blood ooze. Forpatients with obvious endplate destruction and severe vertebral collapse, only the removed healthy bones were implanted into the disc space (Fig. 2f), while the bones are insufficient, artificial bone or allogeneic bone can be used. For cases with intact or mild destruction of superior and inferior endplates, the Cage can be implanted. A cage trial implant was inserted into the disc space to determine the size of the real cage. A special cannula was used to fill the anterior part of the disc space with autologous bone collected from the healthy lamina, articular processes, and spinous process basal due to the concern of bone loss caused by continuous flushing. After the dura and nerve root were protected with a retractor, the cage packed with autologous bone was carefully inserted under endoscopic surveillance to avoid injury to the dura and nerve root. The cage was deeper inserted into the disc space with the help of a hammer and demonstrated its position and size under fluoroscopy. Streptomycin 1.0 g and isoniazid 0.2 g were administered locally. Finally, ipsilateral percutaneous pedicle screws were inserted through the two portals, the contralateral percutaneous pedicle screws were inserted with conventional skin incisions, a drainage catheter was placed and incisions were sutured (Fig. 2g-h). Bacterial culture and pathological diagnosis were performed on the collected lesioned tissues postoperatively.

Postoperative management

All patients continued oral HRZE (isoniazid + rifampin + pyrazinamide + ethambutol) chemotherapy postoperatively, pyrazinamide was discontinued 6 months after the procedure, and then the patients received 9- to12 - month regimens of HRE(isoniazid + rifampin + ethambutol) chemotherapy ⁹. Prevent infection with intravenous antibiotics for 24 hours after the procedure. The drainage catheter was removed when the drainage flow was less than 30ml every 24 hours. The patients were instructed to wear a brace to ambulate 1 day postoperatively, and continued protection for 3 months. X-ray (Fig. 1f), computed tomography (CT) (Fig. 1g), and magnetic resonance imaging (MRI) were performed on all patients before discharge.

Outcome indexes

The operative time, estimated blood loss, time to ambulation, postoperative hospital stay, and complications were recorded. Clinical outcomes include erythrocyte sedimentation rate (ESR), c-reactive protein (CRP), the visual analog scale (VAS) score, Oswestry disability index (ODI), American Spinal Injury Association (ASIA) neurological classification ¹⁰, Cobb angle, and lumbar lordotic angle were analyzed. The lumbar lordotic angle was measured by Cobb's method as the angle of intersection of the vertical lines of the extensions of the endplates on L1 and S1. All patients were examined clinically and radiological at 1, 3, 6 months, and the final follow-up postoperatively. The surgical segmental fusion was assessed using Bridwell grading criteria ¹¹, while there was uncertainty in the X-ray, further evaluation was done by CT.

Statistical analysis

SPSS 26.0 software was used for statistical analysis. All measurement data were tested for normal distribution characteristics expressed as the mean ± standard deviation (SD), significant differences in ESR, CRP, VAS, and ODI were determined using repeated-measures analysis of variance, the paired t-test was used to evaluate changes in the Cobb angle, and lumbar lordotic angle, while the neurological function was statistically analyzed by Wilcoxon signed rank test, P < 0.05 was considered to be statistically difference.

General clinical information

A total of 31 patients (18 males and 13 females, mean age [± SD] was 52.42 ± 10.44 years) who met the criteria were included in our study. The mean duration of symptoms was 5.39 ± 2.58 months, and the mean follow-up time was 19.26 ± 2.85 months. The mean operative time was 171.61 ± 19.03 minutes, the mean estimated blood loss was 243.87 ± 26.54 ml, the mean time to ambulation was 1.87 ± 0.76 days after the procedure, and the mean postoperative hospital stay was 5.61 ± 1.17 days. We observed 4 cases of perioperative complications: 2 cases with transient pain in the buttocks, 1 case with temporary dysesthesia, and 1 case with local incision fat liquefaction, in which the incidence of complications was 12.91% (Table 1). These complications recovered after conservative treatment, and no infection was observed.

Table 1

Clinical data of included patients.
Variables	Value
Age(years)
Mean	52.42 ± 10.44
Range	27–71
Gender
Male	18
Female	13
Level
L1-2	2
L2–3	2
L3–4	5
L4-5	14
L5-S1	8
Duration of symptoms (months)	5.39 ± 2.58
Follow-up period (months)	19.26 ± 2.85
Operative time (minutes)	171.61 ± 19.03
Estimated blood loss (ml)	243.87 ± 26.54
Time to ambulation (days)	1.87 ± 0.76
Postoperative hospital stay (days)	5.61 ± 1.17
Complication
transient pain in the buttocks	2 (6.45%)
temporary dysesthesia	1 (3.23%)
local incision fat liquefaction	1 (3.23%)

Plus-minus values are means ± SD.

Values are presented as the number of patients unless stated otherwise.

Symptom function

The general symptoms, low back and leg pain in all patients were significantly improved after the procedure. The VAS scores of low back and leg, and ODI on the next day, 1 month, 3 months, 6 months, and the last follow-up after the operation were significantly improved compared with before surgery (P < 0.05) (Table 2). Neurological deficits in all patients improved before discharge and normalized at the last follow-up, which the results were evaluated by ASIA classification (Table 3).

Table 2

Clinical outcomes (VAS and ODI) of pre- and post-surgery.
Date	VAS score of low back	VAS score of leg	ODI score (%)
Preoperative	7.48 ± 1.22	6.03 ± 1.28	42.55 ± 5.13
Post-
1 day	4.10 ± 1.16^*	3.00 ± 1.32^*	-
1 month	3.32 ± 0.94^*	2.03 ± 1.22^*	32.28 ± 5.10^*
3 months	2.03 ± 1.22^*	1.42 ± 1.12^*	21.59 ± 4.96^*
6 months	1.35 ± 0.91^*	0.94 ± 0.73^*	16.28 ± 5.11^*
Final follow-up	0.90 ± 0.75^*	0.48 ± 0.57^*	8.67 ± 2.41^*

VAS: Visual Analog Scale, ODI: Oswestry Disability Index, Pre: preoperative, Post: postoperative.

^*Significantly different from the preoperative value (P < 0.05).

Table 3

Preoperative and postoperative ASIA neurological classification.
Date	Grade D of ASIA	Grade E of ASIA
Preoperative	19	12
Before discharge	11	20
Post-3 months	5	26
Final follow-up^*	0	31
ASIA: American Spinal Injury Association, Post: postoperative
*Wilcoxon signed rank test, compare preoperative neurological function classification with the final

follow-up, P < 0.05.

Laboratory and radiographic results

The postoperative pathological findings were all consistent with the diagnosis of spinal TB. The mean pretreatment for ESR and CRP was 45.68 ± 11.02 mm/h and 53.33 ± 7.84mg/L,respectively,which returned to normal levels during the final follow-up in all patients, and there was a statistical difference in ESR and CRP preoperatively and postoperatively (P < 0.05) (Table 4). Cobb angle was 15.23 ± 2.45^° preoperatively, which significantly decreased to 9.81 ± 2.4^° before discharge (P < 0.05), and Cobb angle was 10.94 ± 2.57^° at the final follow-up (P < 0.05). The preoperative, before discharge, and the final follow-up lumbar lordotic angle were 47.96 ± 9.32^°, 42.59 ± 6.16^°, and 44.19 ± 5.58^°, respectively. Compared with the preoperative lumbar lordotic angle, it significantly decreased before discharge (from 47.96 ± 9.32^° to 42.59 ± 6.16^°, P < 0.05). However, there was no significant difference between the preoperative lumbar lordotic angle and the final follow-up (from 47.96 ± 9.32^° to 44.19 ± 5.58^°, P > 0.05) (Table 5). The Cobb angle and lumbar lordotic angle were decreased postoperatively and there was no significant loss of angle at the final follow-up. The X-ray or CT at 6 months after the operation showed that 17 cases (54.84%) had a segmental fusion, 12 cases (38.71%) had fusion trends but were not fused, and 2 cases (6.45%) showed no segmental fusion, which the bony fusion was obtained in all patients at the final follow-up (Figs. 1h-i). No loosening or fracture of the internal fixation occurred in all patients.

Table 4

Laboratory outcomes (ESR and CRP) of pre- and post-surgery.
Date	ESR (mm/h)	CRP (mg/L)
Preoperative	45.68 ± 11.02	53.33 ± 7.84
Before discharge	33.39 ± 7.84^*	36.81 ± 5.83^*
Post-
1 month	20.97 ± 5.08^*	25.31 ± 7.8^*
3 months	11.58 ± 2.22^*	6.19 ± 1.09^*
6 months	7.13 ± 2.35^*	4.92 ± 0.93^*
Final follow-up	5.84 ± 1.93^*	4.63 ± 1.08^*
ESR: erythrocyte sedimentation rate, CRP: C-reactive protein, Pre: preoperative, Post: postoperative

^*significantly different from the preoperative value (P < 0.05).

Table 5

Radiographic outcomes (Cobb angle and lumbar lordotic angle) of pre- and post-surgery.
Date	Cobb angle (^°)	lumbar lordotic angle (^°)
Pre-op	15.23 ± 2.45	47.96 ± 9.32
Before discharge	9.81 ± 2.4^*	42.59 ± 6.16^*
Final follow-up^‡	10.94 ± 2.57^*	44.19 ± 5.58^†
Pre: preoperative, Post: postoperative

The Cobb angle is the angle of intersection between the vertical line of the superior edge of the cranial vertebral body and the vertical line of the inferior edge of the caudal vertebral body.

The lumbar lordotic angle was measured by Cobb's method as the angle of intersection of the vertical lines of the extensions of the endplates on L1 and S1.

^‡Paired t-test, ^*significantly different from the preoperative value (P < 0.05); ^† no significantly different from the preoperative value (P > 0.05).

Spinal TB is common extrapulmonary TB, accounting for about 3–5% of all TB, most commonly in the thoracic and lumbar spine, which leads to low back pain, spinal deformity, and neurological dysfunction according to the course and severity ¹. Nerve injury occurs in up to 10%-43% of spinal TB, which has a high rate of disability ¹². Consequently, drug chemotherapy alone is inadequate for intractable low back pain, severe or progressive neurological dysfunction, and deformity. Surgery plays an important role in the treatment of spinal TB mainly by debridement, decompression, maintenance of stability, and restoration of normal sequence ². The surgery on spinal TB dates back to 1960 when Hodgson and Stock ¹³ performed the first anterior lesion removal and fusion in 412 patients with satisfactory results. Since Mycobacterium TB mostly invades the anterior-middle column, the most direct debridement and decompression can be achieved through the anterior approach without compromising the stability of the posterior. Thus some scholars advocate that anterior is the ideal surgical approach for spinal TB ¹⁴. Nevertheless, it is reported to have more bleeding, operative time, and hospital stay than the posterior approach, and complications such as vascular injury, instrument displacement, and fracture ⁴. For patients with an abscess in the spinal canal, posterior open surgery can be directly performed to remove compression, and pedicle screw fixation can also be performed in spinal instability or kyphotic deformity to maintain or reconstruct spinal stability, correct deformity, and promote bone graft fusion, to effectively treat spinal TB. Although the conservative posterior approach compensates for the anterior, some surgeons deem that it is more destructive to the posterior structure, and may bring Mycobacterium TB located in the anterior column into the otherwise healthy middle and posterior columns resulting in the spread of infection and increasing the risk of nerve injury ⁴.

Minimally invasive treatment of spinal TB has been reported successively and has shown its unique advantages ¹⁵. We treated patients with LTB with the UBE technique, which uses two incisions as viewing and working portals, respectively, the endoscope into the viewing portal to monitor the surgical field, and various instruments into the working portal for operation. Endoscopic decompression and debridement are safer and more efficient, which can ensure adequate decompression and effective removal of the lesion while preserving more normal musculo-ligamentous and bony structures, thereby reducing postoperative complications such as low back pain, muscle atrophy, and spinal instability. Furthermore, percutaneous screw fixation can effectively maintain or reconstruct spinal stability and promote bony union. Some scholars have applied the UBE technique to treat epidural abscesses with excellent outcomes in recent years ⁷. Kim ¹⁶ first reported the successful treatment of patients with spinal TB using biportal endoscopic debridement and percutaneous screw fixation in 2021 and concluded that this technique can be helpful in the diagnosis and treatment of spinal TB. All patients had excellent outcomes after the procedure in this study with no cases of recurrence during the follow-up period. Through some reports above and the results of this research, UBE debridement, interbody fusion, and percutaneous pedicle screw fixation for LTB are feasible under the premise of strictly master surgical indications.

UBE technique is gradually developing and widely used, and it has been extended from degenerative spinal diseases ^5,6 to spinal infectious diseases ^7,15 and even the resection of the spinal canal occupying lesions ¹⁷, with effects comparable to traditional open surgery. Debridement and decompression were performed by the UBE technique under endoscopic surveillance, resulting in more lesion removal and adequate decompression, handling the intervertebral space and bone graft fusion under visualization makes endplate preparation more complete and implantation of bone graft safer. This technique has a broad and clear vision, which is close to the traditional posterior open surgery, the endoscopic structure is easy to identify, the surgical operation is flexible, and the basic tools more familiar to the surgeon can be used for decompression. It combines the characteristics of endoscopic and open surgery and truly reflects the concept of minimally invasive. When the UBE technique is used to treat spinal infectious diseases with bilateral neurogenic symptoms or massive abscesses in the spinal canal, it is recommended to preserve the ipsilateral ligamentum flavum first, which reduces the risk of injury to the dura and ipsilateral nerve root from instruments during contralateral decompression. In cases with LTB, there is significant vascular proliferation, rich blood supply, and easy bleeding. If the ligamentum flavum is removed first, the surgical field is blurred because of hemorrhage, which increases the risk of nerve injury. Specifically for epidural abscess compressing the dura and nerve roots, dura expansion significantly causes the risk of injury to increase when contralateral decompression. Inflammatory exudates often tightly adhere the ligamentum flavum to the dura and nerve roots, and care should be taken during dissection to reduce iatrogenic dural tears. Topical anti-TB drugs provide an effective anti-infection effect ¹⁸. Hemostasis during operation should be careful to maintain clear vision, but should not be maintained by increasing water pressure to prevent the spread of infectious lesions and spinal cord hypertension syndrome. Based on the results of this study, the indications for this technique in the treatment of LTB are as follows: (1) severe or progressive neurological dysfunction due to nerve compression by an abscess; (2) spinal instability owing to vertebral was destroyed; (3) no relief or worsening of symptoms with drug chemotherapy alone. Limitations: (1) the anterior column was severely destroyed, or massive abscess formation at the anterior required for anterior debridement, or the formation of a massive paravertebral abscess; (2) insufficient debridement and decompression may result due to blurred vision; (3) the retroperitoneum may rupture leading to the entry of flushing fluid and tubercle bacillus into the abdominal cavity as a result of the continuous flow of large amounts of flushing fluid ¹⁹; (4) lesions involving segments ≥ 2 or severe spinal deformity.

The posterior debridement and decompression were performed by the UBE technique, surgeons may be concerned about intraspinal or central nervous system infections. To this end, Rath ²⁰ reported posterior debridement and internal fixation for 43 cases of spondylitis (37 suppurative spondylitis and 6 spinal TB) as early as 1996 with outcomes similar to those of anterior decompression, and concluded that posterior debridement and decompression combined with interbody fusion and internal fixation was sufficient for radical debridement and maintenance stability in spinal infectious diseases and that the use of instruments and autologous bone in the presence of infection did not carry a higher risk of persistent or recurrent infection. In 2020, Xu ²¹ reported 62 cases of single-segment lumbosacral spinal TB in adults treated with one-stage posterior debridement, internal fixation, and interbody fusion, with at least 5 years of postoperative follow-up. The results revealed that ESR and CRP returned to normal within 3 months after surgery, and the postoperative VAS score and ODI improved significantly compared with those before the operation. Only one patient had a recurrence of local abscess due to irregular anti-TB medication, which improved with incisional drainage and regular drug chemotherapy. The water-mediated spinal endoscopic operation allows for targeted decompression with continuous irrigation, generating hydraulic pressure, reducing bleeding, and thus maintaining a clear view. Nonetheless, some surgeons are concerned about the risk of spread of infection during debridement due to continuous irrigation when dealing with spinal infectious diseases, but it is worth noting that the UBE technique for spinal infectious diseases has been reported in previous studies with good effects ^7,16. Moreover, other scholars have reported the percutaneous endoscopic debridement for spinal TB with satisfactory outcomes and no recurrence cases ²². Others have suggested that the use of implants may increase the risk of infection because it can reduce the effectiveness of antibiotics while increasing bacterial adhesion and glycocalyx formation. Chang ²³ surveyed bacterial adhesion to implants in 1994 and found that bacterial colonization was less likely to occur in titanium compared to stainless steel. Previous studies have confirmed that the use of titanium implants in spinal infectious diseases was safe and effective, provided that the infected lesion is effectively debrided, and treated with regular antimicrobial drug treatment after the procedure ²⁴. The results of this study were consistent with the above reports, no intraspinal or extraspinal infection, recurrence or implant-related complications occurred, which may be related to regular drug chemotherapy before and after surgery, as well as perioperative use of antibiotics. No cases of the spread of infected lesions were identified in this study, which considered the following reasons: (1) relatively low water pressure during the procedure; (2) the UBE technique creates two portals, and we performed longitudinal and transverse incisions in the fascial layer, which the flushing fluid can flow smoothly from the viewing portal to the working portal, and it is less likely that Mycobacterium tuberculosis settles in the body. Consequently, the author concluded that water-mediated spinal endoscopy techniques for the treatment of spinal infectious diseases offer unique advantages. One aspect is debridement can relieve the compression of the spinal cord or cauda equina and nerve roots by abscess, and copious saline continuous flush can remove most of the inflammatory factors, pus as well as bacteria and discharge them in time, eliminating the stimulation of inflammatory pain-causing factors. Another aspect is that debridement and decompression under endoscopic surveillance are safer and more effective, which can ensure adequate decompression and complete removal of the lesion.

Autologous bone graft was used interbody fusion is good practice in the treatment of spinal infections. However, some have expressed concern about the safety and efficacy of using cages and local autologous bone in LTB. It is worth noting that cage and local autologous bone as grafts for interbody fusion in spinal TB has been reported in previous studies ^25,26. In 2016, Wang ²⁵ performed interbody fusion with titanium a mesh cage which was filled with autogenous bone from the healthy lamina, spinous process as well as allograft bone for lumbosacral TB in the aged, and all achieved excellent fusion postoperatively. Tang ²⁶ adopted the autogenous bones from lamina with the spinous process (LSP), transverse process strut (TPS), and iliac graft (IG) as bone grafts in the treatment of single-segment thoracic TB in 2020. They concluded that LSP and TPS have several advantages as bone grafts. First, compared to IG, LSP and TPS can reduce trauma, bleeding, procedure duration, postoperative drainage, and complications. Also, LSP and TPS as autogenous bones have cortical bone structures supporting the bone defect space, which can ensure and maintain segmental stability and alignment. It has been reported in the literature that synthetic, allogenic, and autogenous bones can achieve good fusion rates as bone graft materials for spinal fusion ²⁷. In this study, the reasons why the authors option the cage and local autologous bones plus artificial or allogeneic bone instead of the autologous ilium to promote fusion are as follows: (1) IG has some complications ²⁸, such as hematoma and infection at the donor site, as well as limited iliac bone material in elderly, which is more invasive, bleeds, operative time, and may result in prolonged bed rest due to intractable pain in the bone extraction area postoperatively; (2) previous studies have demonstrated that the cage, local healthy autografts, artificial and allografts are safe and feasible graft materials with high fusion rates in spinal fusion ^26–28; (3) the local autologous bones from the patients included in this study were all from the healthy lamina, articular processes, and the spinous process basal; (4) some patients who used the cage as a graft had intact or less disrupted endplates in this study. According to previous studies and considering this procedure as minimally invasive, we tried to apply the cage or autologous bones from the healthy lamina, articular processes, and the spinous process basal as well as artificial or allogeneic bone as graft materials, which the bony fusion achieved in all cases at the final follow-up, without graft-related complications. Based on the series of studies mentioned above and the results of this research, the authors deem that interbody fusion with the cage or local healthy autologous bones plus artificial or allogeneic bone is safe and feasible for LTB. The common approach of UBE-assisted endoscopic fusion is posterior and transforaminal interbody fusion, which is less disruptive to normal bony structures than conservative open fusion procedures, while this approach obtains less local autologous bone and is insufficient to achieve solid intervertebral fusion. For this reason, Eum²⁹ proposed a novel UBE-assisted endoscopic fusion technique that is known as extreme transforaminal lumbar interbody fusion in 2022, which fills and laterally places the posterior space with a larger spacer to increase the surface contact area and insert the maximum amount of bone material, with satisfactory short-term results after the procedure. In the decompression of bony structures, our experience is of using a transarticular approach, sequentially removing the inferior articular process, the inferior margin of superior lamina, the superior margin of inferior lamina, as well as the apical and medial of the superior articular process using various tools to fully expose the ipsilateral dural sac and traversing nerve root, and to decompress to the outer of the opposite traversing nerve root and the inner edge of the pedicle if bilateral decompression is required. After determining the approximate location of the medial of the pedicle with a probing hook when removing the superior articular process, the osteotomy with an endoscopic pendulum saw or ultrasonic osteotome can be attempted, which not only provides high efficiency, a neat osteotomy surface, and reduces cancellous bone bleeding, but also allows for the acquisition of intact large bones, avoiding the loss of small bones due to continuous irrigation during the procedure.

Currently, there is no consensus on the selection of internal fixation segments for LTB. It mainly includes long-segment, short-segment, and diseased levels of interbody fixation. Nonetheless, they have different pros and cons, and the choice of the specific fixation method should be determined according to the patient's condition. Since the patients included in this study all had LTB, considering the high mobility of the lumbar, if the fixed segment is too long, it will sacrifice the normal motor unit and increase adjacent segmental degeneration and junctional kyphosis ^4,8,21. Based on this study and previous experience with conventional open surgery, the authors concluded that depending on the size of the lesion destruction of LTB, the stability of the spinal reconstruction was ensured short-segment and diseased level interbody fixation should be used as possible to preserve normal motor units and reduce trauma to achieve an optimum clinical outcome.

In our study, all completed the procedure successfully, and the operative time was close to traditional posterior open surgery reported in previous studies, while significantly less than the anterior approach and combined anterior and posterior approaches. Secondly, the procedure has less bleeding compared to traditional open surgery. Also, traditional open surgery usually requires prolonged bed rest and a long hospital stay postoperatively, which leads to a series of complications such as hypostatic pneumonia ^4,9,21. However, patients can wear a brace to ambulate one day after the procedure and shorten hospitalization in this study. The above results reflect the short operation time, less injury, less bleeding, and rapid recovery characteristics of this procedure. All patients showed a significantly reduced in symptoms such as low back and leg pain after the procedure in this study, which the VAS scores of low back and leg, as well as ODI significantly improved compared to preoperatively. Some patients had instability but no significant spinal deformity in this study, and few patients had spinal cord injuries due to spinal deformity caused by bone destruction. But all patients had epidural abscesses, in which 19 patients with ASIA D had high-grade abscesses with spinal cord compression, their degree of spinal cord injury would have been more severe than the other 12 patients with ASIA E. Previous studies have confirmed that high-grade abscesses with cord compression were significantly associated with the neurological deficit at presentation but not with poor outcomes ³⁰. All patients with neurological dysfunction improved after surgery and all returned to normal at the last follow-up. The reasons for this that effective debridement and continuous saline irrigation intraoperatively. Secondly, interbody fusion and percutaneous pedicle screw fixation can reconstruct or maintain spinal stability and improve the series of symptoms caused by spinal instability due to lesions invading the vertebral body. Besides, though some patients had spinal instability due to vertebral destruction in this study, most of them had no significant kyphotic deformity. Therefore, this may explain the lack of significant change in the Cobb angle and lumbar lordotic angle postoperatively compared to preoperatively. Both ESR and CRP were significantly decreased in patients after the procedure than before surgery, and both returned to normal at the 3 months postoperatively, which is consistent with previous studies ^9,21. The results of X-ray or CT at 6 months after surgery showed fusion of the segments in 17 cases, a tendency of fusion but not complete fusion in 12 cases, and no fusion in 2 cases, bony fusion was achieved at the final follow-up in all cases, similar to traditional open surgery ^4,21. No internal fixation loosening, fracture, and pseudarthrosis occurred in all patients during the follow-up period. A total of 4 (12.9%) procedure-related complications occurred in this study, the incidence is far lower than that of conventional open surgery ⁴. Two patients who underwent unilateral laminectomy and bilateral decompression had mild pain in the buttocks the next day after the operation, whereas they had no this symptom preoperatively. We deem that the cauda equina was stimulated during the contralateral decompression was performed, and the symptom disappeared after treatment with medications. One case had temporary dysesthesia with no impairment of movement and the symptom disappeared after being observed. There was one case of local fat liquefaction in the incision after surgery, which was considered to be related to the patient's obesity and diabetes, and the incision healed after a dressing change. No postoperative epidural hematoma was observed, which may be related to the fact that we routinely placed a drainage tube and maintained it unobstructed before closing the incision, and no complications such as incisional infection, dural tear, or cerebrospinal fluid leakage occurred in all cases.

There are still some potential drawbacks to this study. First of all, this is a single-center retrospective study with a relatively small number of cases treated with this procedure, and selection bias in the inclusion of patients. we plan to conduct a prospective multicenter study with a large sample size to further understand the clinical efficacy of the UBE technique for LTB. Second, we selected patients with only single-segment lesions and there is uncertainty about the safety and efficacy of this procedure when applied at multiple levels, which the study lacks comparisons with other procedures, and the advantages of this procedure for LTB need to be further demonstrated. Furthermore, the follow-up period is relatively short, and there is uncertainty regarding its long-term efficacy and impact on spinal stability. Nevertheless, postoperative symptoms as well as laboratory and imaging findings were significantly improved in the patients included in this study, indicating the feasibility and effectiveness of the UBE technique for the treatment of LTB.

UBE debridement, interbody fusion, and percutaneous pedicle screw fixation are feasible, efficient, and safe methods for the treatment of single-segment LTB, which may become a new approach to minimally invasive surgery for the treatment of LTB.

ASIA: American Spinal Injury Association; CRP: C-reactive protein; CT: Computerized tomography; ESR: Erythrocyte sedimentation rate; HRZE (isoniazid+rifampin+pyrazinamide+ethambutol); HRE (isoniazid+rifampin+ethambutol); IG: Iliac graft; LSP: lamina with spinous process; MRI: Magnetic resonance imaging; ODI: Oswestry disability index; TB: Tuberculosis; TPS: Transverse process strut; UBE: Unilateral biportal endoscopic; VAS: Visual analog scale; LTB: Lumbar tuberculosis

Author contributions

XBW and TL: scientific research design and wrote the manuscript. XBW, YL and YBL: operation, implementation, evaluation, and paper review. XBW and TL: statistical analysis and data collection. All authors have read and approved the final manuscript.

Conflicts of interest

The authors declare that they have no competing interests.

Availability of data and materials

The data sets generated and analyzed during the current study are not publicly available due to restrictions on ethical approvals involving patient data and anonymity but can be obtained from the corresponding author on reasonable request.

Ethics approval and consent to participate

All methods were carried out following the relevant guidelines and regulations. This study was approved by the Ethics Committee of the First Affiliated Hospital of Xinjiang Medical University. All surgical patients participating in the study were aware of the study and signed the informed consent forms.

Funding

This work was supported by Natural Science Foundation of Hunan Province(2024JJ7474) and Science and Technology Plan Project Funding Grant of Shaoyang City (2023NS2015).

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No competing interests reported.

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Treatment of single-segment lumbar tuberculosis by unilateral biportal endoscopic debridement, interbody fusion, and percutaneous pedicle screw fixation

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