Preliminary Clinical and Radiological Outcomes of Trans–Superior Articular Process Endoscopic Lumbar Discectomy

Lumbar disc herniation is a leading cause of low back pain and sciatica, imposing a substantial burden on quality of life and healthcare systems worldwide [1-3]. It results from displacement of nucleus pulposus material through the annulus fibrosus, leading to neural compression and radicular symptoms, and affects approximately 12% to 40% of adults, with peak incidence between 30 and 50 years of age and a higher prevalence in men [1, 2, 4-6]. Established risk factors include age, obesity, smoking, cardiovascular comorbidities, and occupational lumbar loading, while pathological forms range from disc bulge and protrusion to extrusion and sequestration [4, 6, 7]. Although conservative management remains effective for many patients, surgical intervention is required in refractory cases, with minimally invasive endoscopic techniques increasingly favored due to clinical outcomes comparable to open microdiscectomy and the advantages of reduced tissue injury, shorter hospitalization, and faster recovery [5, 7-9]. Accumulating evidence from randomized trials and meta-analyses demonstrates that both approaches provide comparable clinical outcomes, patient satisfaction, and overall recall or complication rates [10-13]. Nevertheless, important technical differences have been reported. The interlaminar approach is consistently associated with shorter operative times and lower radiation exposure, particularly at the L5–S1 level, whereas the transforaminal approach often requires greater technical expertise and increased fluoroscopic guidance. Although both techniques show low rates of dural tears and reherniation, some studies suggest a slightly higher incidence of dural injury and persistent muscle weakness with the transforaminal route [11, 13].

Anatomical variations of the superior articular process (SAP) present a significant challenge to standard transforaminal endoscopic access, especially in patients with foraminal narrowing or SAP hypertrophy. To address these limitations, modified techniques such as the transfacet and trans–superior articular process approaches have been introduced, allowing safe endoscopic access while maintaining spinal stability [14, 15]. Recent systematic reviews and treatment algorithms emphasize that selection of the endoscopic route should be individualized based on disc herniation morphology, spinal level, and patient-specific anatomy. While the transforaminal approach is generally preferred for foraminal or extraforaminal herniations and upper lumbar levels, the interlaminar route is favored for central or subarticular herniations at L4–L5 and L5–S1, particularly in the presence of a high iliac crest or SAP hypertrophy. In this context, the trans-SAP approach represents an important technical adaptation that expands the indications of endoscopic discectomy in anatomically complex cases [11, 12, 15].

Despite the growing global adoption of endoscopic lumbar discectomy and the increasing refinement of techniques such as the trans-SAP, evidence from Southeast Asia, and particularly from Vietnam, remains limited. Differences in patient characteristics, spinal anatomy, disease presentation, surgeon experience, and healthcare systems underscore the need for region-specific data to validate the safety, feasibility, and effectiveness of advanced endoscopic approaches in routine clinical practice. Therefore, the objective of this study was to prospectively evaluate the clinical, radiological, and perioperative outcomes of full-endoscopic lumbar discectomy using the Trans-SAP approach in patients with lumbar disc herniation treated at a tertiary referral center in Vietnam, with particular attention to its applicability in anatomically challenging cases involving foraminal or migrated disc herniations.

(A, B) Exposure of the superior articular process (SAP) and identification of the ligamentum flavum (LF) attachment at the apex of the SAP. (C) Partial resection of the SAP using a high-speed burr to enlarge the intervertebral foramen. (D) Removal of the herniated disc fragment causing nerve root compression. (E) Adequate decompression with a freely mobilized tranversing nerve root (TNR) after removal of the herniated disc. DH: disc herniation, IVD: intravertenral disc.

Outcome Measures

Clinical outcomes were evaluated using standardized and validated assessment tools. Pain intensity was measured using the Visual Analog Scale for both leg pain and back pain. Functional disability was assessed using the Oswestry Disability Index, while overall patient satisfaction was evaluated according to the modified MacNab criteria at the final follow-up.

Radiological outcomes were assessed using magnetic resonance imaging performed both preoperatively and postoperatively to confirm adequate neural decompression and to identify the absence of residual or recurrent disc fragments. Intraoperative and perioperative parameters, including operative time, length of hospital stay, and procedure-related complications, were systematically recorded.

Economic feasibility was also assessed by documenting the total surgical cost after reimbursement by the national health insurance system. In addition, the time required for patients to return to work was recorded for each case, based on postoperative recovery status and occupational demands.

Follow-up

All patients were evaluated by the same surgical team throughout the follow-up period to ensure consistency in clinical assessment. Scheduled follow-up visits were conducted at 1 day, 1 month, 6 months, and at least 12 months postoperatively. At each visit, patients underwent clinical evaluation including Visual Analog Scale and Oswestry Disability Index scoring, as well as a detailed neurological examination to detect any sensory or motor deficits.

Final follow-up data obtained at 12 months or later were used for the primary outcome analysis. Postoperative magnetic resonance imaging was performed either during a scheduled follow-up visit or immediately in cases where new or recurrent symptoms were reported, in order to confirm adequate neural decompression and exclude residual or recurrent disc herniation. All adverse events and postoperative complications, such as dural tears, transient dysesthesia, or infections, were documented and analyzed.

STATISTICAL ANALYSIS

All statistical analyses were performed using SPSS software version 20 (IBM Corp., Armonk, NY, USA). Continuous variables were expressed as mean values with corresponding standard deviations, while categorical variables were presented as percentages. Comparisons between preoperative and postoperative Visual Analog Scale and Oswestry Disability Index scores were conducted using the paired t-test for normally distributed data or the Wilcoxon signed-rank test for non-normally distributed data. A p-value of less than 0.05 was considered to indicate statistical significance. Subgroup analyses were additionally performed to compare clinical outcomes between patients with and without migrated or foraminal disc herniations, in order to further evaluate the effectiveness of the Trans-SAP approach in these more complex clinical scenarios.

Figure 3. Postoperative MRI demonstrating complete neural decompression after Trans-SAP endoscopic lumbar discectomy. Note: (A), (B): Pre-operative; (C), (D): Post-operative

This prospective study demonstrates that full-endoscopic lumbar discectomy using the trans–superior articular process approach provides effective symptom relief, reliable neural decompression, and an acceptable safety profile in patients with lumbar disc herniation, including anatomically complex cases. Overall, the procedure resulted in substantial clinical improvement, low complication and reoperation rates, short hospitalization, and favorable economic feasibility in a Vietnamese tertiary-care setting.

The Trans-SAP approach achieved marked and sustained improvements in pain and functional status, which are consistent with outcomes reported for full-endoscopic transforaminal lumbar discectomy in the international literature. Multiple studies have demonstrated significant reductions in VAS scores for leg pain, with mean values decreasing from approximately 7.0–7.6 preoperatively to below 1.0 at long-term follow-up, including outcomes at 5 years [13, 16-18]. Improvements in functional disability have been similarly robust, with Oswestry Disability Index scores commonly declining from around 60–70% before surgery to approximately 10% at mid- and long-term follow-up [9, 16, 19-21]. High patient satisfaction rates, with 93–94% of patients reporting excellent or good outcomes, have also been consistently reported after endoscopic discectomy [10, 13], supporting the clinical relevance of the improvements observed in the present cohort.

Radiological outcomes in this study further support the technical effectiveness of the Trans-SAP approach. Adequate neural decompression was achieved in more than 90% of cases on postoperative magnetic resonance imaging, despite a substantial proportion of patients presenting with migrated or foraminal disc herniations. These morphologies are widely recognized as technically demanding for standard transforaminal endoscopic access due to superior articular process hypertrophy or foraminal narrowing [19, 21, 22]. Reported recurrence rates following endoscopic lumbar discectomy typically range from 2% to 8% in large series [16, 18, 23], and the low rates of residual and recurrent disc herniation observed in this study are comparable with these benchmarks, suggesting that SAP-assisted access provides sufficient working space and visualization for effective decompression.

The perioperative safety profile observed in this cohort aligns with published data on the feasibility of endoscopic lumbar discectomy. Complication and reoperation rates reported in the literature are generally low and comparable to those of open microdiscectomy, typically ranging between 2% and 8% [9, 10, 13, 24]. Although a learning curve has been described for percutaneous endoscopic techniques, with proficiency often achieved after approximately 27–36 cases [21], outcomes from experienced centers consistently demonstrate low rates of neurological injury and revision surgery. The favorable safety outcomes in this study support the view that careful anatomical orientation and limited resection of the superior articular process can mitigate procedure-related risks, even in complex anatomical settings.

The minimally invasive nature of the Trans-SAP technique is further reflected in its perioperative and recovery-related advantages, which have been widely documented. Endoscopic lumbar discectomy is associated with smaller incisions, minimal blood loss, and shorter hospital stays, typically ranging from 1 to 4 days, when compared with open surgery [13, 16, 19, 22]. These features facilitate early mobilization and rapid return to work, contributing to favorable functional and socioeconomic outcomes. From an economic perspective, although endoscopic procedures may involve higher upfront costs related to specialized equipment and training, cost-utility analyses indicate lower overall societal costs and favorable quality-adjusted life year outcomes compared with microdiscectomy [9, 18]. Together, these findings support the Trans-SAP approach as a clinically effective, safe, and economically reasonable extension of endoscopic lumbar discectomy.

The results of this study support the Trans-SAP endoscopic approach as an effective extension of standard endoscopic lumbar discectomy techniques. It appears particularly useful for patients with foraminal stenosis, migrated disc herniation, or superior articular process hypertrophy, in whom conventional transforaminal access may be restricted. Adoption of this technique may expand the indications for endoscopic surgery while maintaining favorable clinical, radiological, and economic outcomes.

This study has several limitations. The single-center design and lack of a comparative control group limit direct comparison with interlaminar, standard transforaminal, or open surgical approaches. The sample size was moderate, and although all patients were followed for at least 12 months, longer-term data are needed to assess spinal stability and late recurrence. Additionally, outcomes may reflect the experience of a specialized endoscopic surgical team, which may limit generalizability to lower-volume centers.

Full-endoscopic lumbar discectomy via the trans–superior articular process approach is a safe and effective surgical option for lumbar disc herniation, including cases with challenging anatomy. The technique provides significant pain relief, meaningful functional recovery, high rates of radiological decompression, and low complication and reoperation rates, with the added benefits of rapid recovery and economic feasibility. Further multicenter and comparative studies are warranted to validate these findings and refine patient selection criteria.