Robot-Assisted vs Fluoroscopy-Guided Minimally Invasive Transforaminal Lumbar Interbody Fusion for Lumbar Degenerative Diseases: A Comparative Study

Introduction

Lumbar degenerative diseases are one of the common conditions affecting the quality of life of middle-aged and elderly people [1]. In the early stages, these diseases often manifest as lower back discomfort. As they progress, they can compress nerves, leading to symptoms such as leg pain, numbness, weakness, restricted movement, and even urinary and fecal dysfunction, severely impacting quality of life [2]. If conservative treatment is ineffective for more than 3 months or if the condition continues to worsen, surgical treatment is recommended.

Surgical approaches for lumbar degenerative diseases have long been a topic of debate. Traditional open fusion and fixation surgeries typically cause significant trauma, excessive bleeding, prolonged recovery, and substantial damage to lumbar muscles, and can lead to chronic lower back pain [3]. Introduced in 2003, minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) offers benefits such as reduced trauma, quicker recovery, better lumbar muscle protection, and fusion rates comparable to open surgery, making it a widely used minimally invasive procedure [4]. However, MIS-TLIF involves placing pedicle screws percutaneously under fluoroscopy, which is challenging due to the deep location in the lower lumbar spine, potentially leading to inaccuracies, high surgical complexity, and a steep learning curve. Moreover, increased fluoroscopy use increases patient radiation exposure [5,6]. Consequently, achieving precise and swift percutaneous pedicle screw insertion remains the primary challenge in clinical application of MIS-TLIF.

With the successful application of artificial intelligence and robotic navigation technology in spinal surgery, orthopedic robots provide robust support for the precise one-time implantation of screws. Numerous studies and meta-analyses have confirmed the accuracy and safety of robot-assisted pedicle screw placement surgeries for cervical, thoracic, and lumbar vertebrae [7–9]. The economic burden and the issue of the learning curve have led to certain limitations on the use of robots in this field. At present, there are still relatively few studies on robot-assisted MIS-TLIF. This study aimed to compare the clinical outcomes of MIS-TLIF for single-level lumbar degenerative diseases between robot-assisted and fluoroscopy-guided approaches, to determine the safety and feasibility of robot-assisted MIS-TLIF.

Material and Methods

ETHICS STATEMENT:

The study was approved by Ethics Committee of the Honghui Hospital, Xi’an Jiaotong University. Written informed consent was obtained from all participants.

PATIENT POPULATION:

A retrospective analysis was conducted on 40 patients who underwent robot-assisted MIS-TLIF (RA group) at our hospital from January 2020 to January 2022. There were 17 males and 23 females, with an average age of 53.0±7.1 years. Disease types included 12 cases of lumbar spondylolisthesis, 7 cases of lumbar spinal stenosis, and 21 cases of lumbar disc herniation. The affected segments were L5/S1 in 15 cases, L4/5 in 19 cases, L3/4 in 4 cases, and L2/3 in 2 cases. The duration of illness was 12.6±8.3 months. Another 40 patients who underwent fluoroscopy-guided MIS-TLIF (FG group) were analyzed, consisting of 16 males and 24 females, with an average age of 53.2±7.3 years. Disease types included 10 cases of lumbar spondylolisthesis, 8 cases of lumbar spinal stenosis, and 22 cases of lumbar disc herniation. The affected segments were L5/S1 in 16 cases, L4/5 in 20 cases, L3/4 in 3 cases, and L2/3 in 1 case. The duration of illness was 12.3±9.1 months. All the above data are shown in Table 1.

INCLUSION AND EXCLUSION CRITERIA:

Inclusion criteria: (1) Imaging confirmed single-segment lumbar degenerative disease; (2) Failure of regular conservative treatment for more than 3 months; (3) Complete clinical data, with postoperative follow-up time >12 months. Cases with spinal tumors, infections, deformities, trauma, or previous lumbar surgery history were excluded.

RA GROUP: The surgical robot used was the TiRobot® system (Tinavi Medical Technologies Co., Beijing, China). After general anesthesia, the patient was positioned prone. The affected vertebra was localized under C-arm fluoroscopy and marked on the skin. Standard disinfection and draping were performed. The robot tracker and ruler were installed. A lumbar CT scan was conducted using the O-arm, and the data were transmitted to the workstation. The optimal path for pedicle screw insertion into the target vertebra was planned, and, with robotic assistance, percutaneous pedicle guide needles were placed (Figure 1). The skin overlying the 2 Kirschner wires on the symptomatic side was incised, creating an approximately 2-cm–long incision. A working cannula was inserted through the incision, and foraminal decompression was performed, retracting the nerve root and excising the herniated nucleus pulposus tissue. Further disc tissue was removed, and autograft and allograft bone were implanted into the intervertebral space using a bone graft funnel. A suitable-sized fusion cage was then placed into the intervertebral space. The cannulated screws were tapped, and 4 hollow pedicle screws were inserted sequentially. Bilateral titanium rods were installed and appropriately compressed to secure them. Under fluoroscopic confirmation of satisfactory internal fixation and fusion cage placement, the working channel was removed. The wound was repeatedly flushed with normal saline, and meticulous hemostasis was ensured. The incision was sutured, and a routine drainage tube was placed on the decompressed side. The surgery was completed.

FG GROUP:

After general anesthesia, the patient was positioned prone. Two 1-cm incisions were made slightly lateral to the projection of the bilateral pedicles of the target segment on the skin, under C-arm fluoroscopy. Under fluoroscopic guidance, a puncture needle was inserted through the pedicle, and the core was replaced with a Kirschner wire. After re-fluoroscopy, the position of the guide wire was confirmed to be satisfactory. The skin overlying the 2 Kirschner wires on the symptomatic side was incised, measuring about 2 cm. A working cannula was placed through the incision to perform foraminal decompression, retracting the nerve root, and excising the protruding nucleus pulposus tissue. The remaining intervertebral disc tissue was further removed, followed by the insertion of autograft and allograft bone into the disc space using a bone graft funnel. A suitable-sized cage was then placed into the disc space. Tapping was done through the guide wire opening, and 4 hollow pedicle screws were inserted sequentially. Titanium rods were installed bilaterally and appropriately tightened. Fluoroscopy confirmed satisfactory internal fixation and cage placement, after which the working channel was removed. The wound was repeatedly flushed with normal saline and hemostasis was assured. The incision was sutured, and a routine drainage tube was placed on the decompressed side. The surgery was completed.

POSTOPERATIVE MANAGEMENT:

For the first 48 hours after surgery, cefoxitin sodium was administered to prevent infection, and within 24 hours, nonsteroidal anti-inflammatory drugs were administered for pain relief. On the first day after surgery, under the guidance of a physician, patients performed exercises in bed. On the second and third days after surgery, the drainage tube was removed and walking activities began while wearing a brace. For the next 3 months, patients continued to wear the brace and gradually strengthened the back muscle by performing exercises.

OBSERVATION INDICATORS:

We recorded the surgical times for the 2 groups, as well as intraoperative blood loss, radiation exposure time, hospital stay duration, VAS scores of back and leg pain, Oswestry Disability Index (ODI), and postoperative complications. The imaging evaluation was performed by a blinded independent radiologist. VAS scores were used to assess the degree of pain in the back and legs, ranging from 0 (painless) to 10 (the most severe pain). ODI scores were collected to determine the impact on daily living activities, ranging from 0% (no disability) to 100% (maximum disability) [10]. Clinical evaluations were conducted before the operation, 3 days after the operation, and at the final follow-up. We determined the total radiation exposure time by calculating the sum of the cumulative time differences from the start to the end of intraoperative radiation.

To evaluate the accuracy of pedicle screw placement after lumbar spine surgery, we used the Gertzbein-Robbins grading criteria [11]. The screw positions are categorized into 5 levels: A grade indicates that the screw has not penetrated the bone cortex; B grade means the screw has penetrated the bone cortex by ≤2 mm; C grade indicates penetration between 2 mm and ≤4 mm; D grade means penetration between 4 mm and ≤6 mm; E grade indicates penetration greater than 6 mm. A grade is considered precise placement, while A and B grades together represent clinically acceptable placements. Grades C to E indicate suboptimal screw placement.

According to Babu et al, postoperative facet joint violation (FJV) is assessed and categorized into 4 levels [12]. Level 0: The screw is not on the facet joint and does not enter the joint. Level 1: The screw is on the superior articular process but does not enter the joint. Level 2: The screw passes through the facet joint surface by ≤1 mm. Level 3: The screw passes through the facet joint surface. Level 0 is considered to have no FJV, while Levels 1, 2, and 3 indicate varying degrees of FJV.

At the 12-month follow-up, a lumbar spine CT scan was performed to assess intervertebral fusion. Intervertebral fusion is defined as the presence of clear continuous bone callus formation between the upper and lower endplates, as shown on three-dimensional lumbar CT scans [13].

STATISTICAL ANALYSIS:

Statistical analysis was conducted using SPSS 23.0 statistical software (IBM, USA). Measurement data are represented by the mean±standard deviation, two-factor repeated measures analysis of variance was used to compare the differences in the indicators (VAS, ODI scores), and the independent-samples t test was used to compare the differences in the other indicators between the 2 groups. LSD (least significant difference) was used for post hoc testing. Count data are presented as frequency (n, %), and comparisons between groups were made using the χ² or Fisher exact test. The significance level α was set at 0.05 for two-sided tests.

Results

GENERAL INDICATORS:

No statistically significant difference was observed in the general data (age, sex, medical history, disease segment, disease type, and duration of follow-up) between the 2 groups (Table 1). The operating time, radiation exposure time, and intraoperative blood loss were not statistically different between the RA group and the FG group (P>0.05; Table 1). However, the hospital stay was shorter in the RA group compared to the FG group, with a statistically significant difference (P<0.05; Table 1).

SCREW POSITION AND FJV:

Each of the 2 groups was implanted with 160 pedicle screws. According to the Gertzbein-Robbins classification, the RA group had 153 A-grade screws and 7 B-grade screws, with an A-grade accuracy rate of 95.6% (153/160). The FG group had 131 A-grade screws, 23 B-grade screws, and 6 C-grade screws, with an A-grade accuracy rate of 81.9% (131/160). The accuracy rate of A-grade screws in the RA group was significantly higher than that in the FG group (Table 2). In the FG group, although the C-grade screws penetrated the cortex by more than 2 mm, there were no symptoms such as nerve damage, so no adjustment of the screw path was needed.

The FJV grades for the RA group were: 143 at level 0, 13 at level 1, 3 at level 2, and 1 at level 3. For the FG group, the FJV grades are: 109 at level 0, 38 at level 1, 10 at level 2, and 3 at level 3. The incidence of FJV in the FG group was 31.9% (51/160), which was significantly higher than the 10.6% (17/160) in the RA group (Table 2).

CLINICAL OUTCOMES:

In both groups, the VAS back and leg pain scores and ODI scores were lower on the third postoperative day and at the final follow-up compared to preoperatively, with significant differences within each group (Tables 3–5). On the third postoperative day, the VAS back pain score in the RA group was significantly lower than in the FG group, although no significant difference was found between the 2 groups at the final follow-up (Table 3). There were no statistically significant differences between the 2 groups in the VAS leg pain scores and ODI scores at any postoperative time point (Tables 4, 5).

INTERVERTEBRAL FUSION AND COMPLICATIONS:

The RA group had an 87.5% intervertebral fusion rate (35/40), while the FG group had an 85.0% fusion rate (34/40). There was no statistically significant difference between the 2 groups’ fusion rate (P>0.05; Table 6). In the RA group, there were 2 cases of dura mater tearing, 1 case of nerve damage, and 1 case of incision infection. The FG group had 3 cases of dura mater tearing, 1 case of epidural hematoma, and 1 case of nerve damage. All these complications were significantly alleviated after conservative treatment. There was no statistically significant difference in the complication rate between the 2 groups (P>0.05; Table 6). During follow-up, none of the patients in either group developed postoperative complications such as lower-limb venous thrombosis, loosening, or fracture of internal fixation. A representative case is shown in Figure 2.

Discussion

Percutaneous foraminal endoscopy, microscopy, and minimally invasive channel techniques are currently widely utilized minimally invasive surgical approaches for the treatment of lumbar degenerative diseases. Previous studies indicate that each of these minimally invasive techniques has distinct advantages and limitations, and there is currently insufficient evidence to determine which approach offers superior outcomes [14]. MIS-TLIF has recently emerged as one of the primary surgical techniques for treating degenerative lumbar spine diseases, owing to its minimally invasive and highly efficient characteristics. However, the requirement for percutaneous pedicle screw placement, particularly in the deeper lower lumbar region, introduces additional complexity and risk to the procedure, as well as extending the duration of surgery. This is primarily due to the interference caused by soft tissues in the lumbar area and the natural curvature of the lumbar spine. The robotic navigation assistance system, with its advanced tracking capabilities and intraoperative 3D navigation technology for precise spatial positioning and path guidance, enhances the accuracy and safety of the procedure. Consequently, it has progressively gained recognition and acceptance among orthopedic surgeons. In 2013, Hu et al utilized robotic assistance for the implantation of 960 lower cervical pedicle screws in a cohort that included numerous patients with prior spinal surgeries or spinal deformities [15]. Notably, the accuracy rate was maintained at 98.9%, underscoring the substantial benefits of robot-guided techniques in spinal surgery. MacLean et al performed an extensive meta-analysis encompassing 46 studies involving data from 4670 patients and 25 054 screws [16]. Their findings demonstrated that robot-assisted procedures generally exhibited higher accuracy, lower revision rates, and reduced blood loss compared to manual, fluoroscopic, or CT navigation methods. In the present study, the RA group achieved an A-grade screw placement accuracy rate of 95.6% (153/160), which was significantly higher than the 81.9% (131/160) observed in the FG group. This outcome aligns with prior research, further validating the considerable advantages of robot-assisted MIS-TLIF screw placement. The main factors affecting the accuracy of robots are as follows: Firstly, the surgeon’s operational proficiency and clinical decision-making ability directly determine the accuracy of the robotic system, including their adaptability to operating the robotic system, as well as their intraoperative planning and decision-making abilities. Secondly, differences in patients’ individual anatomical and physiological characteristics can affect the accuracy of the robotic system. Thirdly, the standardization of surgical process management and the stability of the surgical environment are key to avoiding “non-technical errors”.

FJV directly compromises the anatomical integrity of the facet joints, thereby impacting joint stability and biomechanics, and exhibits a strong correlation with adjacent segment degeneration following surgery. Consequently, in both open and minimally invasive surgical approaches, it is imperative to minimize screw intrusion into the facet joints to prevent FJV. Babu et al categorized FJV into 4 grades based on its severity, with grade 1 and higher indicating that if a screw penetrates the facet joint, FJV is deemed to have occurred [12]. Prior research has demonstrated that robot-assisted pedicle screw placement results in a lower incidence of FJV compared to traditional fluoroscopy-guided techniques [17,18]. This advantage primarily stems from the robotic navigation system’s ability to precisely plan the screw trajectory and position the entry point more laterally, thereby substantially reducing facet joint intrusion. In contrast, fluoroscopy-guided screw placement depends heavily on the surgeon’s tactile feedback, often leading to an entry point closer to the facet joints. As a result, fluoroscopy-guided surgery exhibits a significantly higher incidence of FJV relative to robot-assisted procedures.

Robotic-assisted surgery ensures precise screw placement in a single attempt, eliminating the need for repeated fluoroscopy to adjust drill hole angles and directions. This approach minimizes additional bone and soft tissue damage, reducing intraoperative blood loss and significantly shortening operation times. Shorter surgery times decrease surgeon fatigue and reduce risks associated with general anesthesia, enhancing overall surgical safety. Li et al found that robotic-assisted MIS-TLIF surgery outperformed fluoroscopy-guided procedures, suggesting that robotic-assisted MIS-TLIF is safer and more effective despite having longer operation times [19]. It offers higher screw placement accuracy and reduces radiation exposure for surgeons and adjacent segment degeneration. However, there were no statistically significant differences in postoperative pain and functional improvement between the 2 groups. In the present study, the RA group had comparable operation times to the FG group. The conventional view posits that robotic-assisted procedures can reduce radiation exposure time, but no statistically significant difference in radiation exposure time was observed between the RA group and the FG group in this study. This finding may be attributed to the fact that we are still in the early phase of robotic system adoption, with insufficient proficiency in its operation. Additionally, the robotic group required not only computed tomography (CT) scans but also a certain number of intraoperative fluoroscopic verifications. These factors are the primary reasons for the lack of a significant reduction in radiation exposure time in the RA group. Intraoperative blood loss was slightly lower in the robotic group, though the difference was not statistically significant, aligning with previous research. Additionally, the robotic-assisted group had a shorter hospital stay, indicating faster postoperative recovery and aiding rapid patient rehabilitation. De Biase et al compared operation times and complication rates of robot-assisted MIS-TLIF and fluoroscopy-assisted MIS-TLIF for lumbar spinal stenosis, finding no statistically significant differences [20]. Both groups showed significant improvements in VAS and ODI scores pre- and post-surgery, but the robotic-assisted group had a significantly lower VAS score for low back pain on the third postoperative day. This suggests that both methods improve patient pain and function, with early postoperative pain improvement being more pronounced in the robotic-assisted group, likely due to its high single-time screw placement accuracy, which eliminates the need for secondary adjustments and reduces bone and soft tissue damage. At the final follow-up, no statistically significant difference was observed in the back VAS scores between the 2 groups. The potential reasons for this finding are as follows: Firstly, with the passage of time, back trauma in both groups had essentially healed, resulting in mild residual back pain in all patients by the final follow-up. Secondly, postoperatively, patients actively participated in rehabilitation exercises – particularly those targeting the recovery of lumbar and back muscles – which contributed to the near-resolution of back pain.

The area around the spine contains important blood vessels and nerves. If screws are misplaced, it can lead to severe nerve damage, dura mater tears, hematomas, and significant bleeding. A study by Hu et al found that problems related to robot use during surgery occurred in 1% to 54% of cases, including poor registration, learning curves, and clinical complications [21]. Keric et al analyzed 462 pedicle screws implanted in 90 patients and found that robot-assisted surgery had a lower complication rate compared to fluoroscopy-guided surgery [22]. The revision rates for screw misplacement were 0.58% for the robot-assisted group and 4.95% for the fluoroscopy group. The perioperative adverse event rates, including hematomas and dura mater tears, were 6.1% and 12.5%, respectively. The postoperative complication rate, including wound infections, were 16.6% and 33.3%, respectively. The complication rates in the present study were significantly lower than in previous studies, and no cases of deep vein thrombosis in the lower limbs, loosening, or breaking of internal fixation occurred postoperatively. This may be due to the surgeons’ extensive experience with robot use in our study, or it may be related to insufficient follow-up time and a small sample size. Additionally, the RA and FG groups had similar and high fusion rates, comparable to traditional open surgery results [23], which confirms the reliability of MIS-TLIF surgery in intervertebral bone graft fusion.

The primary benefit of robot-assisted MIS-TLIF lies in the integration of robotic technology with MIS-TLIF techniques. This combination allows for minimally invasive decompression and fusion at the surgical site using the flexible operating space of MIS-TLIF, while also utilizing the robot’s precision to accurately implant pedicle screws percutaneously. By merging these advanced technologies, superior therapeutic outcomes are achieved through highly precise and minimally invasive methods. However, there are challenges associated with this approach: the learning curve is steep for beginners, who must become proficient in both robotic and MIS-TLIF techniques. Additionally, initial applications may result in longer surgery times and increased complications. The integration of robotic and MIS-TLIF technologies is still in its early stages and requires further research.

This study also has the following limitations: 1. It was a single-center, retrospective study with a small sample size, leading to potential biases in the data results. The follow-up period was short, so long-term efficacy and complications need further validation. 2. The learning curve for robot-assisted MIS-TLIF is lengthy, necessitating advanced surgical skills and experience. It is suitable only for single-level lumbar degenerative diseases. Multicenter, large-scale, and prospective studies are needed.

Conclusions

Compared to fluoroscopy-guided MIS-TLIF, robot-assisted surgery offers advantages in terms of screw placement accuracy, and improvement in early postoperative pain, hospital stay duration, and facet joint violation. Robot-assisted MIS-TLIF is a safe and effective treatment option for single-level lumbar degenerative disease.