Learning curve and complication analysis of oblique lateral interbody fusion in cases with single-segment lumbar tuberculosis: a retrospective single-center consecutive study

Abstract

Objective

Oblique lateral interbody fusion (OLIF) is becoming widely used in patients with single-segment spinal tuberculosis (STB). The learning curve and complications associated with OLIF for the treatment of STB are still unknown. This study aims to figure out the learning curve and associated complications experience of OLIF for the treatment of STB.

Methods

Between September 2018 and August 2023, 61 STB patients underwent OLIF plus percutaneous pedicle screw fixation (PPSF) were consecutively included in this research. Cumulative sum analysis (CUSUM) was applied to establish the learning curve of OLIF and determine the cut-off case number. All cases were divided into learning and experienced groups based on the cut-off case number. Clinical characteristics and relating surgical complications were compared and analyzed between the two groups.

Results

The best-fitting curve was quadratic. The fitting equation was CUSUM (min) = 95.83 + 34.16x − 0.611 x ² (x means operation case). The cut-off operation case number was 27 cases. The presence of significant differences particularly in the duration of operation, operative blood loss, overall incidence, and severity of postoperative complications was noteworthy between the two groups.

Conclusion

A total of 27 cases is the minimum number to master OLIF combined with PPSF for the treatment of patients with single-segment STB. When surgeons master this operation, the operative time, operative blood loss, overall incidence, and severity of postoperative complications will improve.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-024-07968-z.

Introduction

Tuberculosis, recognized as an infectious disease steeped in history, has left its mark as spinal tuberculosis (STB) over the course of human civilization. Unearthed fossils from the Neolithic era around 10,000 BC in what is now Germany bear witness to cervical tuberculosis [1]. STB, a distinctive variant of osteoarticular tuberculosis, presents a remarkable morbidity rate, constituting roughly 50% of all cases [2]. While the administration of anti-tuberculosis drugs remains pivotal in the management of STB, surgical intervention assumes a notable role for cases with spinal instability, progressive nerve deterioration, or severe kyphosis [3]. Three surgical methods are used to treat patients with STB [4]. Posterior-only surgery has better stability reconstruction and deformity correction, but is a non-direct tuberculosis debridement with a limitation that may bring tuberculosis bacteria to the posterior column from the anterior column [5]. Anterior-only surgical approaches are recognized by their enhanced debridement efficacy facilitated by direct visualization, yet they entail greater surgical trauma and pose an elevated risk of vascular or visceral injury [6]. The anterior combined posterior (ACP) approach is advantageous owing to its capability for thorough debridement and the provision of robust internal fixation; however, this surgical method leads to greater incidences of trauma and a higher risk of serious complications, which hinder postoperative recovery [7].

The oblique lateral interbody fusion (OLIF) technique stands as a sophisticated, minimally invasive (MI) surgical procedure designed for anterior lumbar interventions. A critical step in OLIF involves repositioning the psoas muscle to create space between the aorta and psoas, enabling access to the target vertebra or intervertebral space [8]. Studies concluded that OLIF yields superior clinical outcomes relative to traditional posterior lumbar fusion surgery for addressing lumbar degenerative conditions [9]. Moreover, our prior research, along with other investigations, has substantiated the favorable clinical outcomes and safety profile of OLIF in managing STB cases [10–12]. In a similar vein, percutaneous pedicle screw fixation (PPSF) is recognized as a MI approach to pedicle screw placement guided by X-ray. This method obviates the necessity for conventional large posterior incisions, extensive tissue dissection, and traction on the paravertebral muscles. Consequently, PPSF can effectively decrease postoperative pain and expedite the recovery period [11]. Therefore, OILF combined with PPSF for the treatment of single-segment STB is becoming widely used and preferred by surgeons. However, knowledge on ways to master the technique of OLIF and the related complications has gained surgeons’ attention, and requires further exploration.

In this investigation, the combined approach of OLIF with PPSF was employed in treating cases with single-segment lumbar tuberculosis. The aim was to trace the learning curve trajectory and compile a record of complications, all while achieving favorable clinical outcomes. The primary objective was to ascertain the requisite minimum number of operative cases for surgeons to attain proficiency in OLIF, thereby providing a procedural roadmap and sharing insights on complications. This study sought to offer guidance and experience support to surgeons seeking mastery in the combined OLIF with PPSF technique for managing patients with single-segment lumbar tuberculosis.

Materials and methods

Patient selection

Within the scope of this retrospective cohort study, 61 cases with single-segment lumbar tuberculosis were totally included. These cases underwent OLIF plus PPSF at our institution during the period spanning from September 2018 to May 2023. All patients treated using this approach recovered fully without any incidence of recurrent STB over the course of the 1-year follow-up interval.

Inclusion criteria

Patients were selectively included in the study based on stringent criteria, which included the following items: (1) possession of complete medical records, comprising detailed general information, perioperative laboratory evaluations, imaging outcomes (encompassing magnetic resonance imaging [MRI] and computed tomography [CT] scan), and comprehensive clinical data regarding postoperative clinical manifestations; (2) a documented history of undergoing solely single-segment OLIF in conjunction with posterior fixation procedures; and (3) confirmation of postoperative STB through pathological diagnosis.

Exclusion criteria

Subjects were disqualified from participation if they exhibited any of the following conditions: (1) suspected STB lacking confirmation through pathological assay, (2) preliminary or pathological diagnosis of disorders unrelated to STB, (3) a documented history of prior surgical interventions for STB, or (4) had undergone surgical procedures that did not entail the precise combination of OLIF paired exclusively with posterior fixation.

Surgical technique and outcome indexes

Every one of the 61 cases with single-segment lumbar tuberculosis underwent the comprehensive procedure involving OLIF plus PPSF. The clinical data encompassing these patients were precisely compiled and preserved for subsequent analysis. It is noteworthy that all surgical procedures were undertaken through a single seasoned surgeon with a remarkable experience in this specialized field.

Surgical technique

The decision to utilize OLIF was guided by a precise set of criteria, including: (a) the presence of single-segmental lumbar tuberculosis spanning the vertebrae from L2 to L5, (b) preoperative imaging through MRI or CT revealing a proper operative corridor between the psoas muscle and abdominal aorta [13], and (c) bony destruction not exceeding 50% of the vertebrae’s height. The OLIF surgical instrument access system was the OLIF25™ Access (Medtronic Sofamor Danek USA, Inc). The details of the OLIF25™ Access system was shown in Supplementary file 1 and 2.

The detailed OLIF procedure unfolded as Fig. 1: Under general anesthesia, the patient was accurately positioned in a lateral supine orientation, with the affected side upward to expose the region of bone deterioration. A C-arm X-ray was employed to precisely identify the surgical segments, followed by a 4 cm incision made in the lateral ventral region, running parallel to the external oblique muscle. Layer by layer, the external abdominal oblique, internal abdominal oblique, and transverse abdominal muscles were meticulously dissected. By delicately moving the extraperitoneal fat aside with precision, the anterior boundary of the psoas muscle was pinpointed using a Cobb periosteal stripper. An S-shaped retractor was then inserted to protect the sheath of the abdominal great vessels, delicately displace the psoas muscle with the Cobb periosteum stripper, and position an OLIF right-angle retractor. The intervertebral space harboring the lesion was carefully exposed between the vessel sheath and the anterior limit of the psoas muscle. A positioning needle was introduced, and the exact location of the lesioned segment was meticulously confirmed using a C-arm X-ray. Various expanders were utilized in conjunction with the probe to widen the access channel to 22 mm, with a suitable retraction device chosen to completely expose the surgical segments. To ensure the absence of vessels, nerves, or any other interfering structures within the channel, a thorough reconfirmation was undertaken before inserting a stable nail. The access channel employed in this study was an OLIF 25 Access attained from Medtronic that was headquartered in the USA. Subsequently, the abscess, granulation tissue, caseous necrotic material, and necrotic intervertebral disc were meticulously excised. Depending on the measurement of the intervertebral space height post-debridement, either a polyetheretherketone (PEEK) cage or a titanium mesh cage (TMC) filled with granular bone was meticulously implanted. Following the careful placement of a drainage tube, the layers of the incision were meticulously closed. The patient was then repositioned to the prone position, and posterior internal fixation was precisely executed using percutaneous pedicle screw instrumentation through the Wiltse approach (the paraspinal muscle approach between the multifidus and longissimus muscles) [14]. Using the C-arm X-ray, it was verified that the screws had achieved optimal placement. Eventually, the wound underwent a thorough rinsing before being meticulously closed, layer by layer. The standard case of single-segment lumbar tuberculosis was shown in Fig. 2.

Fig. 1.

Real-time case of single-segment lumbar (L4) tuberculosis patient requiring debridement with OLIF combined with PPSF surgery. (a) Preoperative positioning for OLIF combined with PPSF. (b) Establishment of OLIF channel. (c) Anterior approach surgical debridement and titanium mesh implantation. (d) Posterior internal fixation using PPSF. (e) Surgical incision suture of PPSF. (f) Spinal tuberculosis lesion tissue pending examination. (OLIF: Oblique lateral interbody fusion; PPSF: percutaneous pedicle screw fixation.)

Fig. 2.

Case of single-segment lumbar (L4) tuberculosis patient requiring debridement with OLIF combined with PPSF surgery. (a) Preoperative X-ray. (b) Preoperative CT. (c) Immediate postoperative X-ray. (d) Postoperative CT at 3 months. (OLIF: Oblique lateral interbody fusion; PPSF: percutaneous pedicle screw fixation; CT: computed tomography; MRI: magnetic resonance imaging.)

Outcome indexes

The clinical characteristics analyzed in this study involved a range of parameters: age, gender, body mass index (BMI), history of alcohol consumption and smoking, duration of the disease, preoperative levels of hemoglobin, serum albumin, and C-reactive protein (CRP), lymphocyte count, erythrocyte sedimentation rate (ESR), operation time, surgical blood loss, and postoperative complications. These complications were systematically graded into diverse levels on the basis of the Clavien-Dindo (C/D) classification system (Table 1).

Table 1.

Details of Clavien-Dindo classification of complications

Grade	Definition
I	Any deviation from the normal postoperative course without the need for pharmacological treatment or surgical, endoscopic, and radiological interventions. Allowed regimens are: antiemetics, antipyretics, analgesics, diuretics, electrolytes, and physiotherapy. Includes wound opened at the bedside
II	Requiring pharmacological treatment with drugs other than those allowed for grade I. Includes blood transfusions and total parental nutrition
III	Requiring surgical, endoscopic, or radiological intervention
IIIa	Intervention not under general anesthesia
IIIb	Intervention under general anesthesia
IV	Life-threatening complication requiring intensive care unit management
IVa	Single organ dysfunction (including dialysis)
IVb	Multiorgan dysfunction
V	Death

CUSUM analysis

It was attempted to analyze the learning curve through the cumulative sum (CUSUM) approach. The formula is as follows: . In this context, Xi denotes the specific operation time for each patient, while u is suggestive of the average operation time for the entire cohort [15]. The learning curve was plotted by summing the differences between the chronological order of operation time for each case and the overall average operation time of the entire group. The case number corresponding to the apex of the learning curve is the cut-off operation case number.

Statistical analysis

It was attempted to conduct statistical analysis through SPSS version 26.0 software developed by IBM that was headquartered in NY (USA). Expression of continuous variables adhering to the Gaussian (normal) distribution was in form of mean ± standard deviation particularly for data following a normal distribution. The criteria used to choose between the tests in the statistical analysis: t-test for inter-group comparison of continuous variables, Mann-Whitney test is applicable for inter-group comparison of ordered categorical variables, and Chi-square test for inter-group comparison of categorical variables. Considering that the data meets the assumptions of homogeneity of variance and normality, t-test was chosen as the method for inter-group comparisons. The comparable analysis of categorical parameters was undertaken through Chi-square test. A P threshold below 0.05 was suggestive of statistical significance. The sample size estimation for this study was based on the formula of specific statistical purpose, this group meet the sample size estimation requirements.

Results

A total of 61 patients with STB (27 men and 34 women) were enrolled in the study (Table 2). The mean operative time of the patients was 205.56 ± 24.15 min, the average age was 46.98 ± 17.46 years, and the mean BMI was 21.57 ± 3.12 kg/m2.

Table 2.

Comparison of perioperative characteristics of 61 tuberculosis patients

Characteristics	Learning group (n = 27)	Experienced group (n = 34)	95%CI	Cohen’s d value	P-value
Age(year)	46.48 ± 19.02	47.38 ± 16.40	(−9.978, 8.177)	-0.051	0.843
BMI(kg/m2)	21.82 ± 3.42	20.38 ± 2.90	(−1.176, 2.065)	0.459	0.585
Sex(n,%)			-	-	0.980
Female	15(55.6%)	19(55.9%)
Male	12(44.4%)	15(44.1%)
Smoking history(year)	7.44 ± 13.22	8.15 ± 12.69	(−7.370, 5.964)	-0.055	0.834
Alcohol use(year)	7.37 ± 12.16	6.91 ± 11.36	(−5.588, 6.506)	0.039	0.880
Preoperative hemoglobin(g/L)	118.74 ± 17.97	119.09 ± 16.40	(−9.171, 8.476)	-0.020	0.937
Preoperative lymphocytes(×109/L)	1.25 ± 0.44	1.21 ± 0.41	(−0.184, 0.252)	0.094	0.755
Preoperative serum albumin(g/L)	38.52 ± 4.12	37.76 ± 5.42	(−1.767, 3.274)	0.155	0.552
Preoperative CRP(mg/L)	31.44 ± 25.62	39.66 ± 40.85	(−26.250, 9,819)	-0.235	0.366
Preoperative ESR(mm/h)	55.67 ± 32.83	59.38 ± 21.55	(−17.698, 10.267)	-0.137	0.597
Course of disease(month)	6.89 ± 9.07	8.44 ± 6.89	(−5.642, 2.537)	-0.196	0.451
Operative time(min)	226.41 ± 16.88	187.41 ± 8.35	(33.797, 48.196)	3.040	<0.001*
Operative blood loss(ml)	602.78 ± 181.92	444.56 ± 112.24	(82.360, 234.078)	1.076	<0.001*
Postoperative complication			-	-	0.033*
Yes	20	16
No	7	18
C/D classification of complications			-	-	0.024*
Classification I	9	13
Classification II	9	3
Classification III	2	0

Abbreviations: BMI, body mass index; C/D, Clavien-Dindo; CRP, C-reactive protein; ESR, erythrocyte sedimentation rate; OR, odds ratio; CI, confidence interval. Statistical criteria: t-test for inter-group comparison of continuous variables, and Chi-square test for inter-group comparison of categorical variables, The Mann-Whitney test is applicable for comparing ordered categorical variables between two groups.

Learning curve

The descending trend of the operation time due to consecutive case accumulation is shown in Fig. 3, the best fitting curve is quadratic curve, and the formula is y = 260.1–2.781x + 0.025 x ² (y indicates operation time, and x indicates case number) with an R² value of 0.91. 95% CI of β₁, β₂ and β₃ are [254.2, 266], [-3.222, -2.341] and [0.018, 0.032]. The cumulative CUSUM curve is shown in Fig. 4, where the best fitting curve is a quadratic curve, and the fitting equation is y = 95.83 + 34.16x − 0.611 x ² (y indicates the CUSUM value, and x indicates the case number) with an R² value of 0.94. 95% CI of β₁, β₂ and β₃ are [59.53, 132.1], [31.46, 36.86] and [-0.653, -0.568]. The cut-off operation case number corresponding to the apex of the learning curve was determined for 27 cases.

Fig. 3.

Variation trend of operative time in OLIF combined with PPSF in single-segment STB patients. (OLIF: Oblique lateral interbody fusion; PPSF: percutaneous pedicle screw fixation; STB: spinal tuberculosis.)

Fig. 4.

Scatter plot of CUSUM learning curve for OLIF combined with PPSF in single-segment STB patients. (CUSUM: Cumulative sum analysis; OLIF: Oblique lateral interbody fusion; PPSF: percutaneous pedicle screw fixation.)

Comparison between the groups

The first 27 cases were defined as the learning group, and the last 34 were the experienced group. The comparison of clinical characteristics, including age, sex, BMI, alcohol use and smoking history, course of the disease, preoperative hemoglobin, serum albumin, and CRP levels, lymphocyte count, ESR, operation time, operative blood loss, and complications (Table 2). The presence of significant differences particularly in the operation time, operative blood loss, overall incidence, and severity of postoperative complications was noteworthy between the two groups. The experienced group had a longer operation time, more operative blood loss, and higher risk and more serious postoperative complications than that of the learning group

Complications

Among the 61 patients, 25 did not experience postoperative complications, and 36 had different degrees of postoperative complications. Among the 36 patients with postoperative complications, 22 had C/D classification I, 12 had C/D classification II, and 2 had C/D classification III (Table 3). C/D classification III cases included surgical site infection and rupture of the iliac vein. As the number of surgical cases increased, the severity and occurrence of complications decreased (Fig. 5)

Table 3.

Details of tuberculosis patients with Clavien-Dindo classification of postoperative complications

Postoperative complication	Number
Total	61
No postoperative complication	25(41.0%)
Clavien-Dindo I	22 (36.1%)
Low serum albumin	15
Mild and moderate anemia	7
High fever	2
Gastrointestinal symptoms	8
Electrolyte disorders	3
Iliac pain	6
Clavien-Dindo II	12 (19.7%)
Hypoalbuminemia	10
Severe anemia	3
Limb nerve symptoms	1
Ileus	4
Thrombus	1
Urinary tract infection	2
Clavien-Dindo IIIa	1 (1.6%)
Surgical site infection	1
Clavien-Dindo IIIb	1 (1.6%)
Rupture of iliac vein	1

Fig. 5.

Trend of complications in OLIF combined with PPSF in single-segment STB patients. (OLIF: Oblique lateral interbody fusion; PPSF: percutaneous pedicle screw fixation; STB: spinal tuberculosis.)

Discussion

The main methods for managing STB consist of surgical intervention and anti-tuberculosis therapy. Anti-tuberculosis therapy, which serves as the cornerstone of STB treatment, relies on a combination of four drugs: rifampicin, isoniazid, pyrazinamide, and ethambutol [2]. Surgical treatment of STB is assisted by anti-tuberculosis drug treatment. Surgical treatment can shorten the treatment period, reduce disability and mortality rates, and enable earlier recovery. The predominant indications necessitating surgical intervention for STB cases often involve the presence of spinal deformities, mechanical instability, and neurological deficits [3]. Surgical treatment of STB mainly consists of focus debridement and reconstruction of spinal function [3]. Complete debridement of the vertebral focus tissue is a key step in controlling tuberculosis infection. Reconstruction of spinal function is achieved by bone grafting combined with internal fixation. Currently, the surgical methods of STB mainly include anterior only, posterior only, and ACP approach.

The anterior-only approach can fully expose the anterior vertebral body and the dural sac, which is beneficial for several aspects such as complete vertebral focus debridement, reducing the STB recurrence rate and the incidence of spinal cord injury, complete internal fixation with bone grafting, correcting the deformity, and stabilizing the spine at the same time [16]. Compared with that of the posterior-only approach, the anterior-only approach has few advantages, such as a MI incision, shorter operation time, and less surgical blood loss; however, the stability of postoperative spinal reconstruction is not as good as that of the posterior-only approach [17]. The posterior-only approach can achieve three-dimensional correction and long-term stable fixation of the spine through the internal fixation system, which has the best deformity correction effect and the most stable internal fixation support, while the posterior-only approach can also avoid the surgical damage caused to abdominal organs and large blood vessels and reduce the risk of complications such as internal fixation failure and vertebra cut by pedicle screws [18]. The limitations of the posterior-only approach are evident. The posterior approach may damage the structure of the posterior column, which affects the stability of the spine, and may also introduce Mycobacterium tuberculosis from the anterior and middle columns into the posterior column to aggravate the infection. In addition, the posterior approach may lead to incomplete focus debridement owing to the small surgical field and inconvenient operation [19]. In addition, because the spinal cord and nerve roots are mainly distributed behind the vertebra, the nerve and dura may be injured during posterior surgery, which increases the difficulty of bone grafting. Owing to the traction of the lumbar muscles, posterior surgery often causes long-term postoperative low back pain [20]. The traditional ACP approach involves posterior spinal nerve decompression, deformity correction, and internal fixation, followed by anterior vertebral focus debridement and bone graft fusion. This surgical approach has the advantages of complete debridement, good deformity correction, and satisfactory clinical efficacy, especially suitable for patients with multiple-segment STB with large paravertebral abscesses [21]. In addition, the ACP approach has a strong internal fixation for single and multiple segments, and its anterior operation visual field is clear for complete debridement and sufficient bone grafting, which is most beneficial for the long-term stability of multiple-segment reconstruction. However, ACP approach is more complicated, has greater surgical trauma, requires more operation time, and causes more blood loss, which requires higher physical tolerance of patients [22].

OLIF represents an innovative MI surgical approach to the anterior lumbar region. This technique involves accessing the extraperitoneal space through the intermuscular gap of the abdominal wall, strategically displacing the psoas major muscle to establish the surgical corridor. Notably, this approach is recognized by its minimal incisions, resulting in a notable reduction in surgical trauma, a shortened operation duration, and a remarkable decrease in blood loss [12]. The Wiltse approach, a posterior internal fixation technology, was first proposed by Wiltse in 1968, and is an approach applied through the interstitial space between the multifidus and longissimus muscles [14]. It avoids paravertebral muscle dissection and injury and can significantly reduce postoperative low back pain [23]. While the OLIF technique shares similarities with traditional ACP approach, the incidence of surgical trauma in the OLIF group was relatively low [11]. The visual field is usually confined when the traditional anterior approach is used for vertebral focus debridement. However, under the OLIF surgical corridor, debridement can be performed clearly and directly, and the surrounding tissues and large vessels can be effectively protected, making the operation safer. In addition, the MI trait of OLIF combined with the Wiltse approach posterior fixation has resulted in a lower risk of complications than that of the traditional ACP approach.

It is important to note that prior to applying OLIF combined with PPSF for STB, the surgeon’s experience with OLIF combined with PPSF for lumbar degenerative disease and experience with posterior approach for STB are the most important factors. OLIF combined with the Wiltse approach posterior fixation is a new surgical technique applied to patients with STB and has a corresponding learning curve. Changes in the operation time and complications are the main characteristics of the learning curve of this approach. According to the CUSUM analysis, we found that the average operation time could be reduced when the number of operation cases reached 27, which was across the apex of the learning curve. The 61 cases were divided into learning and experienced groups before and after the apex of the learning curve. The first 27 cases were defined as the learning group; in this period, with the accumulation of surgical cases, the operator’s experience and skills improved, the operation time was significantly reduced, and the learning curve tended to be steep. The experienced group comprised 34 out of 61 cases; during this period, the experience and skill of the surgeon were well improved, the operation time was at a plateau, and the learning curve tended to be flat. In addition to operation time, the presence of significant differences particularly in the incidence and severity of complications was noteworthy between the two groups. The cumulative complication rates stood at 74.07% among patients in the learning group, contrasting with a lower rate of 47.06% observed in the experienced group. There were 11 cases with complications over C/D classification II in the learning group, including 2 with C/D classification III and 3 with C/D classification II complications in the experienced group.

Woods et al. reported complications over C/D classification II in 11.7% of 137 patients with the lumbar degenerative disease who underwent OLIF in their study [24]. In this study, the rate of complications over C/D classification II was 22.9% in patients with STB who underwent OLIF combined with the posterior approach. This complication rate is acceptable given that STB is a chronic wasting disease and this surgical procedure is more complex. However, we found that there were two cases of C/D classification III complications in the learning group: surgical site infection in the 4th case and rupture of the iliac vein in the 14th case. Postoperative surgical site infection in the fourth case may be related to prolonged operation time. Noteworthy, studies have provided evidence of a strong association between the duration of the operation and the likelihood of postoperative incision infections following spinal surgery [25, 26]. Beiner et al. pointed out that operations lasting longer than 180 min predispose patients to a higher risk of postoperative wound infections [27]. Our previous studies suggested that patients with STB are more likely to have poor wound healing when the operation time exceeds 200 min [28]. This further shows that the study of the learning curve of the operation time of OLIF has clinical significance in reducing postoperative wound infection. The learning curve of this study showed that after the number of operation cases reached 27, the average operation time could be reduced to 187.41 ± 8.35 min, thereby reducing the risk of postoperative poor wound healing. The rupture of the iliac vein during 14th operative case was caused by the misplacement of the OLIF corridor, and the surgical segment of this patient was L5–S1. Placement of the OLIF channel is particularly important for patients with surgical segments L5–S1 because of the low position of the L5–S1 segment, the close proximity of the surrounding great vessels, and the limited location of the iliac wing. These limitations often limit the operative field of view during L5–S1 OLIF surgery. In addition, the execution of OLIF particularly at the L5–S1 level continues to present challenges due to the inherent risks associated with elongating the iliac vessels and the impediment caused by the iliac wing during cage insertion. Capellades et al. have verified the remarkable anatomical diversity of vascular structures in the lumbosacral region [29]. These are the main reasons for the failure of OLIF to be applied to the L5–S1 segment. After the rupture of the iliac vein case, to solve the problem of how to place the OLIF corridor in the L5–S1 segment safely, we proposed a method to determine a safe corridor through the auxiliary V-line by analyzing the imaging anatomical characteristics of the psoas major muscle and iliac vessels. We suggest that when patients with STB with the L5–S1 segment involved plan to undergo OLIF surgery, the feasibility of OLIF surgical channel placement in the L5–S1 segment must be fully evaluated. The ease of placement of the surgical corridor can be determined by assessing the difficulty of pulling the psoas major and iliac vein and the position of the bifurcation of the iliac vessels to ensure the safety of the OLIF operation of the L5–S1 segment of the patient. After we used this method to evaluate the L5–S1segment condition, no subsequent iliac vessel injury was observed. Therefore, we suggest that this set of evaluation methods can be used to evaluate patients with STB with OLIF surgical plan for the OLIF L5–S1 segment, thereby reducing intraoperative iliac vessel damage and enhancing surgical safety.

Conclusion

The learning curve is crucial for surgeons to perform OLIF for patients with STB. A total of 27 cases is the minimum number of surgical cases that need to be accumulated to master OLIF combined with a posterior fixation for the treatment of patients with single-segment STB. When surgeons master this operation, the operation time, operative blood loss, overall incidence, and severity of postoperative complications will improve.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Abbreviations

OLIF

Oblique lateral interbody fusion

STB

Spinal tuberculosis

PPSF

Percutaneous pedicle screw fixation

CUSUM

Cumulative sum analysis

ACP

Anterior combined posterior

MI

Minimally invasive

MRI

Magnetic resonance imaging

CT

Computed tomography

PEEK

Polyetheretherketone

TMC

Titanium mesh cage

BMI

Body mass index

CRP

C-reactive protein

ESR

Erythrocyte sedimentation rate

C/D

Clavien-Dindo

Author contributions

XD, WS and ZH designed and performed the study. GJ, YT and ML collected and analyzed the data. GJ, QW and HL interpret the results. GJ wrote the first draft of the paper. All authors revised the paper critically for intellectual content and approved the final version.

Funding

This research was supported by the Natural Science Foundation of Chongqing (CSTB2022NSCQ-MSX0972), Chongqing medical scientific research project (Joint project of Chongqing Health Commission and Science and Technology Bureau) (2023QNXM030) and the Natural Science Foundation of Chongqing (CSTB2022NSCQ-MSX0781).

Data availability

The data and materials supporting the conclusions are included in this article, data are available from the authors upon reasonable request.

Declarations

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.

Ethical approval and consent to participate

This study was in accordance with the Declaration of Helsinki (as revised in 2013) and was approved by the Institutional Ethics Board of The First Affiliated Hospital of Chongqing Medical University (K2023-076). All necessary written informed consent were provided by participants in this study. All the subjects in this study are consent to participate this study, and the written consent forms were obtained from all individuals of this study.