Robotic-assisted midline lumbar interbody fusion for the treatment of degenerative lumbar spinal stenosis: a prospective, randomized, controlled, non-inferiority clinical trial protocol

Introduction

Degenerative lumbar spinal stenosis (DLSS) primarily results from the progressive degeneration of spinal structures, such as osteophyte formation within the spinal canal, facet joint hypertrophy, and ligamentum flavum thickening (1). These changes reduce the spinal canal volume, compress neural elements, and lead to low back pain and bilateral lower extremity neurological symptoms (2). With the accelerating trend of population aging, the incidence of DLSS has risen steadily, establishing it as a significant health concern among the elderly population. When conservative management fails after at least three months, surgery becomes the optimal treatment for symptomatic relief (3).

Historically, posterior lumbar interbody fusion (PLIF) has been the standard surgical technique for multilevel DLSS (4,5). PLIF provides thorough decompression and, combined with conventional pedicle screw fixation (PSF), effectively restores three-dimensional spinal stability. Consequently, it offers high fusion rates and satisfactory clinical outcomes, sustaining its widespread use (6). However, the PLIF approach typically necessitates a longer incision, extensive paraspinal muscle dissection, and disruption of the posterior ligamentous complex. This results in greater surgical trauma, increased blood loss, and risks damage to the facet joints and multifidus muscle (7)^. These factors contribute to a higher incidence of persistent postoperative low back pain (8). Furthermore, screw loosening remains a major complication in osteoporotic patients, leading to higher revision rates and significantly impacting quality of life (9).

In 2009, Santoni et al. introduced the cortical bone trajectory (CBT) technique, characterized by a medially-inferior to laterally-superior screw trajectory (10). It minimizes paraspinal muscle dissection, preserves the ligamentous complex, and avoids facet joint violation, thereby overcoming significant drawbacks of traditional PLIF. It maximizes screw contact with cortical bone, enhancing pullout strength and providing robust fixation, particularly beneficial for osteoporotic and obese patients (11,12). Driven by the evolution of minimally invasive spine surgery (MISS) concepts, midline lumbar interbody fusion with cortical bone trajectory (MIDLIF-CBT) emerged as a minimally invasive alternative (13,14). Its primary benefit lies in enabling decompression, interbody fusion, and screw placement through a single, small midline incision. The CBT screw trajectory, angling laterally and superiorly from the pars interarticularis, requires minimal operative space. This significantly reduces paraspinal muscle retraction and dissection, thereby minimizing approach-related morbidity (15,16).

MIDLIF minimizes muscle dissection and iatrogenic injury inherent to traditional pedicle screw fixation. Conventional techniques require lateral entry points near the facet joints, necessitating extensive paraspinal and multifidus muscle dissection. This risks injury to the medial branches of the dorsal rami, potentially causing persistent postoperative low back pain or failed back surgery syndrome (FBSS) (17). In contrast, CBT’s midline entry points and medial-to-lateral, caudal-to-cephalad trajectory eliminate the need for extensive muscle stripping or mamillo-accessory complex exposure (18). This minimally invasive approach facilitates earlier ambulation, aligning with enhanced recovery after surgery (ERAS) principles (19). Supporting this, Hung et al. demonstrated MIDLIF causes less multifidus damage and fatty infiltration than PLIF, leading to superior pain relief (20).

Within spine surgery, robotic assistance has demonstrably improved screw placement accuracy, reduced neurological complication rates, decreased radiation exposure, shortened operative times and surgeon learning curves, and enhanced safety for both medical staff and patients (21,22). Numerous studies and meta-analyses report comparable or superior accuracy for robot-assisted screw insertion compared to conventional techniques (23,24). However, a critical gap persists in the current research evidence. Existing literature has predominantly focused on comparing robotic-assisted versus conventional fluoroscopic techniques (25), or evaluating MIDLIF-CBT against traditional fusion methods (26-28). These findings are confounded by the combined effects of assistive technology and the core surgical technique. With the robotic platform established as a common technological baseline—significantly mitigating various challenges and limitations associated with conventional techniques—can the innovative minimally invasive combination (MIDLIF-CBT) still demonstrate clinical value superior to the standard established technique (PLIF-PSF)? This study employs robotics as a controlled variable to directly compare the MIDLIF-CBT technique against the conventional PLIF-PSF technique. This design enables a pure evaluation of their inherent differences in safety, efficacy, and their distinct capacities to promote ERAS principles, isolated from the variable of surgical execution tool. We present this article in accordance with the SPIRIT reporting checklist (29) (available at https://jss.amegroups.com/article/view/10.21037/jss-25-149/rc).

Methods

Trial design

This study employs a prospective, randomized, controlled, non-inferiority trial design conducted at a single center. The flowchart of the study protocol is shown in Figure 1. All surgical procedures will be performed at Beijing Shijitan Hospital Affiliated to Capital Medical University. Participants will be allocated in a 1:1 ratio to the experimental and control groups using computer-generated randomization.

Figure 1 Participant flow through the randomized controlled trial. CBT, cortical bone trajectory; CT, computed tomography; DLSS, degenerative lumbar spinal stenosis; JOA, Japanese Orthopaedic Association; MIDLIF, midline lumbar interbody fusion; MRI, magnetic resonance imaging; ODI, Oswestry Disability Index; PLIF, posterior lumbar interbody fusion; VAS, Visual Analog Scale.

Trial registration: the protocol was registered with the Chinese Clinical Trial Registry (www.chictr.org.cn, Registration Number: ChiCTR2500095896).

Participants

Participants were recruited from patients diagnosed with DLSS presenting to spine surgery department of Beijing Shijitan Hospital Affiliated to Capital Medical University between January 2025 and December 2025.

Inclusion criteria

Patients were eligible if they met all of the following criteria:

• Aged 60–80 years.
• Confirmed diagnosis of DLSS.
• Failure to respond to at least 3 months of standard conservative management.
• With at least one of clear indications for lumbar interbody fusion: the presence of spondylolisthesis (Meyerding grade I or higher); radiographic evidence of instability on dynamic X-rays, defined as translational motion >3 mm or angular motion >10°; severe stenosis necessitating an anticipated bilateral facetectomy of >50% during decompression.

Exclusion criteria

Patients were excluded if any of the following applied:

• History of previous lumbar spine surgery.
• Presence of significant spinal deformity, spinal tumor, infection, or inflammatory spinal disease.
• Severe comorbidities (e.g., cardiac, hepatic, renal), malignant disease, or medical conditions deemed to pose unacceptable surgical risk.
• Chronic use of systemic corticosteroids.
• Diagnosed psychiatric disorders.
• Refusal to provide written informed consent.

Discontinuation criteria

Participants were withdrawn from the study under the following circumstances:

• Withdrawal: development of evidence suggesting potential harm from continued participation or poor protocol adherence.
• Dropout: occurrence of a serious adverse event (SAE) or suspected unexpected serious adverse reaction (SUSAR), loss to follow-up, or voluntary withdrawal of informed consent.
• Study termination: participant refusal of further treatment or required follow-up assessments.

Eligibility criteria for intervention providers

Only board-certified attending spinal surgeons from Beijing Shijitan Hospital, possessing valid national medical licensing and hospital credentials for performing lumbar fusion procedures, are authorized to deliver interventions in this trial. All participating surgeons must have a minimum of 5 years of independent surgical experience with at least 100 prior lumbar interbody fusions as primary operator. Additionally, each surgeon must complete manufacturer-certified training on the specific robotic system and successfully perform 5 proctored robotic-assisted procedures before enrolling any participants. Ongoing participation is contingent upon strict protocol adherence and maintenance of all certifications.

Randomization and blinding

A computer-generated randomization schedule was produced using SAS software (SAS Institute Inc., Cary, NC, USA) by a research assistant not involved in the trial. Allocation concealment was ensured using the sequentially numbered, opaque, sealed envelopes (SNOSE) technique. The group assignment for each participant, generated by the computer program, was placed in a sealed, opaque envelope. Upon obtaining written informed consent, the envelope was opened to reveal the participant’s treatment allocation. Participants were randomly assigned to either the robotic-assisted midline lumbar interbody fusion with cortical bone trajectory screw fixation (RA-MIDLIF-CBTSF) group or the robotic-assisted posterior lumbar interbody fusion with pedicle screw fixation (RA-PLIF-PSF) group.

Due to the nature of the surgical interventions being compared (two distinct operative techniques), blinding of the participating surgeons and operating room personnel was not feasible. However, study participants, outcome assessors, and data analysts remained blinded to group assignment throughout the trial. Personnel enrolling participants and assigning interventions will remain blinded to the random allocation sequence, which will be exclusively managed and concealed by an independent biostatistician using a centralized computer-generated randomization system.

Data collection and management

Data were collected using paper case report forms (CRFs) complemented by electronic data capture (EDC), with all outcome assessors receiving centralized training to ensure standardized evaluation procedures. Primary assessment instruments and radiographic evaluations performed by blinded independent reviewers using standardized protocols to ensure measurement consistency and data reliability. Following the completion of data collection, the database was locked. Once locked, the data files were immutable. Any discrepancies identified post-lock were documented and rectified exclusively within the statistical analysis programs after confirmation and approval. The final locked dataset was uploaded to the ResMan Clinical Trial Public Management Platform. The schedule of the enrolment, intervention, and assessment is shown in Table 1.

Baseline data

All enrolled patients will undergo comprehensive baseline assessment prior to randomization. Demographic characteristics (age, sex, body mass index), clinical history (duration of symptoms, prior conservative treatments), and preoperative functional status will be systematically documented. Key baseline metrics include the Oswestry Disability Index (ODI), Visual Analog Scale (VAS) scores for low back and leg pain, and Japanese Orthopaedic Association (JOA) score. Imaging data [magnetic resonance imaging/computed tomography (MRI/CT)] confirming single-level DLSS, along with lumbar anteroposterior (AP), lateral, and flexion-extension (dynamic) radiographs to assess spinal stability, will be reviewed to standardize anatomical severity. Operative level distribution (L3–L4, L4–L5, L5–S1) and comorbidities (quantified via the Charlson Comorbidity Index) will be recorded. Health economic parameters (baseline healthcare utilization and quality-of-life metrics) will also be collected using standardized questionnaires. These data will ensure balanced group allocation and facilitate adjusted analyses of postoperative outcomes.

Interventions

Group A (control group): RA-PLIF-PSF

Patients underwent RA-PLIF-PSF under general anesthesia in prone position. After fluoroscopic identification of target level(s), an 8–12 cm midline posterior incision (length proportional to fused levels) was made. Subperiosteal dissection exposed relevant decompression structures. Robot-assisted bilateral pedicle screw insertion was performed at the pathological level(s). Following screw placement, disc distraction, rod fixation, and compression were applied. Fluoroscopy-guided decompression, discectomy, and interbody fusion with bone grafting were completed. Standard closure included drain placement.

Group B (experimental group): MIDLIF-CBT

Patients underwent RA-MIDLIF-CBT under general anesthesia. A 3–5 cm midline posterior incision was made. Subperiosteal dissection exposed medial facet joints and lamina isthmus, preserving proximal joint capsules. Robot-assisted CBT screw trajectory planning followed Matsukawa’s method. Decompression side screws were deferred. Following unilateral facetectomy, ligamentum flavum excision, and thecal sac protection, discectomy and interbody cage placement were performed. CBT screws were then inserted. After fluoroscopic confirmation, lordotic rods were secured. Wound closure mirrored Group A.

Concomitant care

During the trial, participants are permitted to receive necessary medical treatments for general comorbidities (e.g., hypertension, diabetes mellitus) to ensure their overall health and safety. However, any invasive interventions specifically targeting the lumbar spine (including but not limited to epidural injections, nerve blocks, radiofrequency ablation, or additional spinal surgeries) are strictly prohibited during the study period. Any other non-protocol-specified therapies or interventions that may potentially influence the study outcomes must be discussed with and explicitly approved by the attending physician of this study during outpatient follow-up visits. All concomitant care, whether permitted or prohibited, must be fully documented in the CRFs.

Follow-up schedule

The visit schedule includes an immediate postoperative assessment prior to hospital discharge, followed by planned follow-up evaluations at 1, 3, 6, and 12 months after surgery. At each of these follow-up visits (including discharge), patient symptoms will be documented, a physical examination will be performed, and clinical efficacy will be assessed. Imaging studies will be conducted at specific intervals: lumbar spine radiographs (AP, lateral, and flexion-extension views) will be obtained at the 3-, 6-, and 12-month postoperative visits to evaluate implant position and spinal stability, while lumbar CT scans will be performed at the 6- and 12-month follow-ups specifically to assess interbody fusion status.

Outcomes

Primary outcome

• ODI: assessed disability severity. The sum of scores from 10 items (each scored 0–5) was converted to a percentage (total/50). Higher percentages indicate greater disability.

Secondary outcomes

• Pain intensity: measured using the VAS (0= no pain, 10= worst imaginable pain).
• Functional status: assessed with the JOA score (Chinese version, patient-reported; 0–29 points). Improvement rate was calculated as: [(postoperative score − preoperative score)/(29 − preoperative score)] × 100%.
• Surgical parameters: operative time, incision length, intraoperative blood loss, total intraoperative fluoroscopy radiation dose (mSv), postoperative 24-hour drainage volume, and postoperative hospital stay.
• Screw placement accuracy: evaluated using the modified Gertzbein-Robbins classification (Grades 0 and 1 considered accurate) (30).
• Facet joint violation: assessed using the Babu grading system (Grade 0: no intrusion; Grade 1: lateral to facet; Grade 2: <1 mm intrusion; Grade 3: ≥1 mm intrusion or intra-articular).
• Radiographic outcomes:
  • Segmental instability: defined as >3 mm translation or >11° angulation on dynamic flexion-extension radiographs.
  • Fusion status: determined by presence of continuous bridging bone trabeculae across the disc space. Non-union indicators included cage subsidence, endplate cystic changes, or radiolucent lines.

ERAS adherence & economic impact: evaluated using a validated scoring system developed based on previous trial data and established ERAS quality frameworks. The multi-level metric was assessed independently by two quality control committee members, averaged, weighted, and summed for a total adherence score (higher scores indicating better ERAS implementation).

AE monitoring and reporting

AEs

All AEs occurring during the study period were recorded, including but not limited to: spinal nerve injury, dural tear/cerebrospinal fluid leak, iatrogenic fracture, new-onset motor weakness, gait difficulty, surgical site infection, deep vein thrombosis, pneumonia, urinary tract infection, adjacent segment disease, pseudarthrosis, revision surgery, and any other event potentially compromising participant health.

• Recording: investigators documented all AEs in the CRFs, capturing time of onset, severity, duration, suspected relationship to intervention, and outcome.
• Assessment: causality and severity were evaluated using a standardized 5-point scale.

SAEs and SUSARs

SAEs were defined as any AE resulting in death, a life-threatening experience, persistent or significant disability or incapacity, hospitalization or prolongation of existing hospitalization, or other medically significant events. SUSARs referred to SAEs that were deemed potentially related to the study intervention and considered unexpected, meaning they were not consistent with the known safety profile or anticipated effects of the surgical procedures involved in the trial.

Reporting

• Investigators recorded SAEs using ICH E2B(R3) compliant fields.
• After investigator review and assessment of causality/severity, SAE reports were submitted within 24 hours of awareness to the sponsor, Institutional Review Board (IRB), and Clinical Trial Office.
• SUSARs were reported by the sponsor to investigators, the institution, and the IRB following expedited timelines (7- and 15-day requirements).

Unblinding: emergency unblinding was permitted for SAE/SUSAR management. Reasons for unblinding were documented in the CRF.

Sample size

The sample size was calculated for a non-inferiority trial design with a 1:1 allocation ratio between the experimental (RA-MIDLIF-CBT) and control (RA-PLIF-PSF) groups. Based on prior literature (31), the standard deviation (SD) of the ODI score following RA-PLIF-PSF was 15.9. As no existing data reported the ODI SD for RA-MIDLIF-CBT, we conservatively assumed an equal SD (S =15.9) for both groups. The study hypothesized that both techniques would yield similar clinical efficacy, corresponding to a true intergroup difference in postoperative ODI (δ) of zero. The non-inferiority margin (Δδ) was set at 12.8, representing the minimal clinically important difference (MCID) for ODI established in the literature (32). Using a one-sided significance level (α) of 0.025 and a power (1 − β) of 90%, the required sample size per group was calculated using the following formula for non-inferiority trials comparing two means: N=2(Z1−α+Zβ)2S2(δ−Δδ)2=2(1.96+1.28)2×15.92(0−12.8)2≈33. Given that patients in Beijing Shijitan Hospital Affiliated to Capital Medical University come from all over the country, making follow-up work challenging, we have preset a loss to follow-up rate of approximately 10%. We have planned a total sample size of 37 for each group, amounting to a total of 74 cases.

Statistical methods

Measurement data were statistically described based on their distribution normality. Normally distributed data were summarized using mean and SD, while non-normally distributed data were presented as median and interquartile range. Categorical data were described using counts and percentages. The primary outcome (ODI score) and secondary outcomes (VAS and JOA scores) were analyzed in the per-protocol population (i.e., patients who completed at least one follow-up visit).

A repeated measures analysis was performed using the mixed-effects model procedure PROC MIXED in SAS 9.4 to compare between-group differences over time. Changes from baseline in ODI, VAS, and JOA scores at each time point were assessed, and least-squares means along with 95% confidence intervals were calculated for these changes. The fixed effects, including treatment group (RA-MIDLIF-CBTSF vs. RA-PLIF-PSF), time (1, 3, 6 months, and 1 year after randomization), and the time-by-treatment interaction, were further examined by estimating standard errors and test statistics for the fixed effects.

Independent samples t-tests were used for other continuous variables (reported as mean ± SD), while Chi-squared tests or Fisher’s exact tests were applied for categorical variables. A two-sided significance level of P<0.05 was used for all tests. All statistical analyses were conducted using SAS version 9.4.

Missing data and subgroup analyses

All analyses will primarily follow the intention-to-treat (ITT) principle, including all randomized participants in the group to which they were originally allocated, regardless of the intervention actually received. A secondary per-protocol analysis will include only participants who completed the study without major protocol deviations. For both analyses, participants will be analyzed within their randomly assigned group (robotic-assisted or open surgery).

Missing data will be addressed through multiple imputation methods using chained equations, creating 20 imputed datasets based on available baseline and outcome variables under the missing at random assumption, with final estimates pooled using Rubin’s rules; complete case analysis will be performed as sensitivity analysis.

Pre-specified subgroup analyses will examine treatment effects by age (<65/≥65 years), stenosis severity (central/lateral), and number of operated levels (single/multiple), with interaction terms tested in regression models; sensitivity analyses will include per-protocol analysis and alternative imputation methods to verify result robustness.

Strategies for achieving adequate participant enrolment

To ensure target sample size attainment, a proactive retention strategy will be implemented. Prior to discharge, participants will receive detailed education regarding the complete follow-up schedule and required examinations, accompanied by a written timeline. Systematic follow-up reminders will be initiated for participants who miss scheduled visits by more than 1 week, beginning with telephone contact followed by SMS reminders if needed. All contact attempts will be documented to maintain engagement and minimize loss to follow-up.

Quality control and monitoring

A comprehensive quality control protocol was established and distributed to all study personnel. A dedicated quality control officer was appointed to oversee trial conduct. The principal investigator (PI) was responsible for:

• Monitoring subject enrollment and documenting reasons for withdrawal.
• Compiling comprehensive AE reports.
• Arranging medical follow-up for withdrawn participants.
• Maintaining close communication with assessors to identify and address issues during data collection and intervention delivery.

Study progress was reviewed biweekly through meetings between the PI and research team to monitor AE occurrence and ensure timely recruitment. Additionally, the PI conducted monthly audits of source data and intervention fidelity. Any necessary protocol modifications were submitted to the Ethics Committee of Beijing Shijitan Hospital, Capital Medical University for approval prior to implementation.

One formal interim analysis for efficacy and futility will be conducted by an independent statistician when 50% of participants have completed their 12-month follow-up, using group sequential methods with O’Brien-Fleming stopping boundaries. The Data and Safety Monitoring Board (DSMB) will have exclusive access to unblinded interim results and may recommend early trial termination to the steering committee (SC) if either: (I) overwhelming efficacy (P<0.001) is demonstrated for primary outcomes; or (II) futility conditions (conditional power <20%) are met. The SC retains final decision authority regarding trial termination, based on the DSMB’s recommendation and overall risk-benefit assessment.

Trial conduct will be monitored through a combination of centralized and on-site monitoring coordinated by an independent clinical research associate, with initial site initiation visits followed by quarterly routine monitoring visits and a final close-out visit. The monitoring process will include: (I) verification of informed consent documentation against source records; (II) 100% source data verification (SDV) for primary outcome measures and AEs; (III) review of eligibility criteria compliance; (IV) assessment of protocol adherence in intervention delivery; and (V) evaluation of data quality through systematic query resolution tracking. All monitoring findings will be documented in formal reports with categorized findings requiring corrective and preventive actions (CAPA), which must be addressed by the site within 30 days of identification.

Ethics and informed consent

This study will be conducted in accordance with the ethical principles of the Declaration of Helsinki and its subsequent amendments, the “Administrative Measures for Clinical Research Initiated by Investigators in Healthcare Institutions (Trial)”, the “Ethical Review Measures for Biomedical Research Involving Humans”, and relevant national regulations. The study was approved by the Ethical Committee of Beijing Shijitan Hospital Affiliated to Capital Medical University (No. IIT2024-035-003). Any safety-related issues, including protocol amendments, informed consent form modifications, or SAEs, were promptly reported to the IRB. Study termination or premature closure was also reported to the IRB.

Trained research physicians from the spinal surgery department will obtain written informed consent from all potential participants using institution-approved consent documents. The process will involve a comprehensive explanation of the trial’s purpose, procedures, risks, benefits, and alternative treatments in language appropriate to the participant’s understanding, with adequate time provided for questions. All signed consent forms will be maintained in secure trial documentation files. For participants lacking decision-making capacity, enrollment was permitted only after IRB approval and when deemed by the investigator to be in the participant’s best interest. In such cases, consent was provided by a legally authorized representative. Participants retained the right to withdraw at any stage of the study without penalty. This study does not involve the collection or use of biological samples from participants.

Study findings may be published in medical journals; however, participant confidentiality will be strictly maintained according to legal requirements. Personally identifiable information will not be disclosed unless mandated by law. Authorized representatives of regulatory authorities and the IRB may access participant records for audit purposes as stipulated by applicable regulations.

Approved amendments will be promptly communicated to all relevant parties through the following procedure: the coordinating center will distribute the updated protocol document and a summary of changes to all participating clinical sites within 5 working days of approval; PIs at each site are responsible for immediately implementing the changes and informing their site staff; the trial registry (ChiCTR) will be updated within 10 working days of approval; and all current participants will be informed of relevant modifications by their site investigator and may be required to provide renewed consent if the changes affect their participation. Minor administrative corrections that do not affect study procedures will be documented and shared at the next routine monitoring visit.

All participants will receive standard medical care for trial-related injuries in accordance with China’s healthcare policies. The sponsor has obtained clinical trial insurance to cover compensation for any harm directly resulting from trial participation. This coverage includes necessary medical treatment and financial compensation for temporary or permanent disability, as determined by an independent adjudication committee. Participants experiencing trial-related AEs will continue to receive appropriate medical management until resolution or stabilization. For procedures specifically required by the trial protocol, associated costs will be borne by the study. These provisions adhere to the Ethics Guidelines for Clinical Research and China’s regulations on human subjects protection.

Trial governance and oversight committees

Coordinating center

The coordinating center, located within the Department of Spinal Surgery at Beijing Shijitan Hospital, is staffed by a PI, Clinical Project Manager, Study Coordinators, and Data Management Specialists. It serves as the operational hub for daily site coordination, document preparation, and staff training. The center manages trial device allocation, supports SC activities, and submits regular progress reports to oversight bodies.

SC

Comprising 5–7 members including an independent chair, PI, site investigators, and biostatistician, the SC provides high-level trial oversight. The committee reviews and approves protocol amendments, assesses interim analyses, and makes recommendations regarding trial continuation. It holds final responsibility for result interpretation and publication planning, convening quarterly via teleconference with annual face-to-face meetings.

Endpoint adjudication committee (EAC)

This independent blinded committee of three spinal surgery and radiology experts adjudicates all endpoint events using predefined criteria. Before trial initiation, the EAC establishes an adjudication charter defining outcomes such as fusion success and re-operation rates. Members review source documents independently before reaching consensus on endpoint determinations, with results provided for final analysis.

Data management team

The hospital’s data management specialists and programmers maintain the EDC system and perform quality control checks. Their responsibilities include developing data management protocols, generating queries for site resolution, coding AEs and medications, and preparing blinded reports for committee review before database locking.

Other oversighting entities

An independent DSMB comprising non-participating surgeons and statisticians periodically reviews unblinded safety data to assess risk-benefit profiles and provides continuation recommendations. The institutional and site ethics committees ensure ongoing protocol compliance with Declaration of Helsinki and Good Clinical Practice (GCP) standards through initial and continuing review of all trial documents.

Trial status

The study protocol was registered at Chinese Clinical Trial Registry (www.chictr.org.cn, Registration Number: ChiCTR2500095896). Participant recruitment commenced on February 1, 2025, and remains ongoing. As of the submission date, 37 participants have been enrolled. Recruitment is projected to conclude by January 31, 2026.

Plans for dissemination of trial results

The primary trial results will be disseminated through publication in a peer-reviewed international medical journal, regardless of the outcome. A comprehensive final report will be submitted to the funding commission as part of the grant closure requirements. Furthermore, key findings will be presented at relevant national and international scientific conferences to share insights with the healthcare professional community.

Discussion

This prospective randomized controlled non-inferiority trial aims to determine whether RA-MIDLIF-CBTSF is non-inferior to RA-PLIF-PSF in treating DLSS, specifically regarding the primary endpoint of clinical efficacy as measured by ODI at 12 months and key postoperative recovery metrics relevant to ERAS principles (e.g., time to ambulation, length of stay, opioid consumption) enhancement within an ERAS pathway.

While robotic assistance in spine surgery is increasingly prevalent, its specific impact on accelerating patient recovery and optimizing ERAS protocols remains poorly characterized and lacks high-level evidence unclear. Current research on the integration of surgical robotics and ERAS principles, particularly within spine surgery, is nascent and lacks high-level evidence from randomized controlled trials (RCTs) (33). Although the success of ERAS programs hinges on multidisciplinary collaboration and patient-provider engagement, surgical technique refinement is a critical component paramount (34). Robotic assistance offers potential advantages in precision and minimally invasive approaches, which could align precisely with this principle of procedural optimization and contribute to reduced tissue trauma, potentially facilitating faster recovery (35).

The design of this study is underpinned by a core premise: the evaluation of surgical techniques in modern spine surgery must advance to a more refined stage. We did not approach robotic assistance as an independent intervention variable to be validated, but rather positioned it as an “enabling platform” that ensures complex techniques are performed accurately, safely, and reproducibly. By comparing MIDLIF-CBT and PLIF-PSF on this equitable platform, we effectively controlled for the potential confounder of “execution precision”. Consequently, any observed differences in ERAS outcomes—whether in postoperative pain or the speed of functional recovery—can be more robustly attributed to the inherent disparities between the two surgical techniques in terms of surgical access, extent of tissue trauma, and biomechanical properties. This design does not aim to validate the value of the robot itself, but to investigate whether the MIDLIF-CBT technique, a concept designed for maximal minimal invasiveness, can translate its theoretical advantages into definitive and quantifiable clinical gains when empowered by robotic technology.

Addressing a critical evidence gap, this RCT investigates the confluence of robotic technology and ERAS principles by directly comparing RA-MIDLIF-CBT to RA-PLIF-PSF. The study is designed to evaluate their comparative effectiveness in improving ERAS outcomes and potentially reducing the economic burden of postoperative care for elderly DLSS patients. The findings will provide robust evidence to establish the clinical utility of RA-MIDLIF-CBT, define its application value in contemporary geriatric spine surgery, and guide the development of more standardized and optimized ERAS protocols incorporating robotic assistance.

Acknowledgments

We would like to thank all the patients for their participation in this investigation. We would also like to thank the orthopedic clinicians for their involvement in patient diagnosis for this research.

Footnote

Reporting Checklist: The authors have completed the SPIRIT reporting checklist. Available at https://jss.amegroups.com/article/view/10.21037/jss-25-149/rc

Peer Review File: Available at https://jss.amegroups.com/article/view/10.21037/jss-25-149/prf

Funding: This work was supported by the Capital Health Development Research Special Project (No. 2024-2-2088).

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jss.amegroups.com/article/view/10.21037/jss-25-149/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study will be conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Ethical Committee of Beijing Shijitan Hospital Affiliated to Capital Medical University (No. IIT2024-035-003). Written informed consent will be obtained from all participants.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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