Trends in Lumbar Spinal Decompression Surgery at a Single Tertiary Center: A Retrospective Review

1. Study Design and Setting

This retrospective cohort study was conducted at a tertiary healthcare institution in Singapore. The study adhered to the STROBE (Strengthening the Report of Observational Studies in Epidemiology) guidelines [30].

2. Study Population

All patients aged 18 years and above who underwent lumbar decompression surgery between January 2021, and December 2024 were included in this study. The inclusion and exclusion criteria are detailed as follows.

3. Data Collection

Data were extracted from electronic medical records. Variables included demographics (age, sex, body mass index [BMI], smoking status), comorbidities, magnetic resonance imaging (MRI) findings, surgical details, and functional scores. MRI pathological findings were systematically documented and cross-checked for accuracy. Outcomes were assessed using 36-Item Short Form Survey (SF-36) and visual analogue scale (VAS; back and leg pain) scores at baseline, 3 months, 6 months, and 2 years. Surgical variables included operation time, length of stay, and reoperation rates. Operation time included time for anesthesia and draping, operation time from skin incision to wound closure, and recovery time.

4. Treatment

All patients underwent either endoscopic or open microscopic single-level spinal decompression surgery. All surgeries were performed by 9 board-certified spine surgeons with either interlaminar or transforaminal approach depending on preoperative imaging and stenosis location. The transforaminal approach was primarily utilized for foraminal, or extraforaminal stenosis, with or without concomitant lateral recess stenosis, allowing targeted decompression of the exiting and traversing nerve roots through undercutting of the superior articular process and removal of hypertrophied ligamentum flavum. The interlaminar approach was preferentially used for cases with predominant central canal stenosis to facilitate bilateral or central decompression. In all cases, the extent of decompression was tailored to achieve adequate neural element decompression. Patients were mobilized within 24 hours postoperatively, and standard rehabilitation protocols were followed.

5. Outcome Measures

The primary outcome measures were the SF-36 and VAS scores. Secondary outcomes included length of hospital stay, and reoperation rates.

6. Statistical Analysis

Statistical analyses were performed using RStudio ver. 4.3.3 (R Foundation for Statistical Computing, Austria). Descriptive statistics were used to summarize baseline variables. Continuous variables were expressed as mean±standard deviation or median with interquartile range (IQR). The normality of mean differences in pre and postoperative SF-36 and VAS scores was assessed using the Student t-test, Shapiro-Wilk, Mann-Whitney and Cohen d tests. Statistical significance was set at p<0.05.

7. Ethical Approval

This study was approved by the institutional ethics board (ECOS Ref No. 2020-2381). Consent was waived due to the retrospective nature of the study.

1. Patient Characteristics

A total of 588 cases of single-level lumbar spine decompression cases were done during the study period. 364 cases were endoscopic; 224 cases were open microscopic (Table 1). Median age was 61 (IQR, 45–69) years, with 53.7% male and 46.2% female. Median BMI was 26 (IQR, 23–29) kg/m², and mean duration of symptoms from diagnosis to surgery for elective cases was 128 days. 93 patients (41.5%) demonstrated more than a single level of pathology on preoperative MRI, but clinical-radiological correlation identified a single symptomatic level responsible for the patients’ predominant symptoms. Consequently, all included patients underwent single-level decompression surgery. Most patients (62.1%) presented with neurogenic claudication, while 37.9% had predominant radicular symptoms. Common comorbidities included hypertension (55.2%), diabetes (28.7%), and obesity (32.2%).

Table 1.

Clinical characteristics, pathology, and surgical characteristics of patients with lumbar spinal stenosis

2. Surgical Characteristics

For single-level unilateral cases, decompression was done via the transforaminal approach in 14.1% of cases, and interlaminar in 85.9%. The mean duration of a single-level ESS was 148 (standard deviation [SD], 75.8) minutes, while that of a single-level open microscopic decompression surgery was 186.0 (SD, 79.4) minutes. The median hospital stay was 1 (range, 1–3) day. No major intraoperative complications were reported. The mean duration of hospital stay was 1.3 (SD, 0.5) days for endoscopic cases, and 1.95 (SD, 2.35) days for microdecompression cases. One revision emergency surgery was required for an endoscopic case, due to inadequate decompression at the original site. One revision surgery was required for a microdecompression case, also due to recurrence of symptoms.

3. Outcomes

A total of 295 patients had documented functional scores at follow-up appointments and 293 patients had no documented follow-up at the point of data collection. Following hospital protocols, these patients would be contacted by telephone on the day of their scheduled appointment and would be given a new appointment within 1 month. For patients who remain unreachable despite repeated efforts, their data were classified as lost to follow-up.

SF-36 and VAS back pain and leg pain scores were used to determine the pre and postoperative functional status up to 6 months. A higher score for SF-36 demonstrates a better patient-reported health status, while a lower VAS score demonstrates lower pain intensity for the patient.

At 1, 3, 6 months, and 2 years postoperatively, both endoscopic and open microscopic groups demonstrated statistically significant improvement in functional outcomes across nearly all SF-36 subdomains and VAS scores (Table 2). At 1 month postoperatively, Short Form Health Survey physical function (SFPF) improved by 11.2 points in the endoscopic group (p<0.001) compared to 7.0 points in the open group (p=0.005). VAS for leg pain (VASLP) improved by 3.6 in endoscopic cases compared to 3.5 in open cases (both p<0.001). Short Form Health Survey role function emotional improvement was more pronounced in the endoscopic group (8.9 vs. 0.9), though this did not reach statistical significance (p=0.10 in difference-in-difference [DID] analysis). Short Form Health Survey mental health (SFMH) showed early improvement in both groups (5.4 in endoscopic vs. 9.0 in open).

Table 2.

Comparison of mean differences in pre- and postoperative SF-36 scores for patients who underwent endoscopic versus open (microscopic) single-level lumbar spinal decompression

At 3 months, both groups maintained improvements in SFPF, Short Form Health Survey bodily pain (SFBP), and Short Form Health Survey social function (SFSF) scores. By 6 months, VAS for back pain (VASBP) and VASLP reductions were sustained in both cohorts, with more pronounced reduction in back pain among endoscopic patients (-3.30 vs. -3.17), although this difference was not statistically significant (DID=-0.14, p=0.82).

At 2 years, functional scores remained improved in both groups. The SFPF score in the endoscopic group improved by 18.6 points (SD, 21.7; p=0.064), while the open group improved by 36.7 points (SD, 20.9; p=0.007). DID analysis yielded a between-group difference of -18.1 points in SFPF (p=0.155), indicating a trend favoring the open approach for long-term physical functioning, although not statistically significant. In contrast, SFBP, SFSF, and SFMH scores were sustained or modestly improved in both groups, with no statistically significant differences. VAS scores for both back and leg pain remained stable over the 2-year follow-up, indicating durable pain relief across both surgical modalities.

Both endoscopic and open decompression approaches offer durable symptom relief and functional benefit, with minor differences in long-term outcomes that may relate to patient selection, surgical complexity, or learning curve factors.

A formal DID analysis (Table 2) was performed to evaluate whether the magnitude of improvement in functional outcomes differed significantly between surgical techniques. Overall, there was no statistically significant difference in most outcome domains, confirming that both endoscopic and open decompression yield comparable functional recovery. At 6 months, SFPF scores improved more in the open group (DID=-7.37, p=0.23), SFBP showed a trend toward greater improvement in the endoscopic group (DID=7.63, p=0.16).

Although SFPF and SFBP improvements at 2 years were numerically higher in the open group, none of the DID comparisons reached statistical significance. The sustained improvements in VASLP and VASBP were similar in both groups, with DID values showing no significant intergroup disparity.

To explore the impact of surgical experience on functional outcomes, cases were stratified by surgeon and year (Figure 1). Endoscopic SFPF improvements varied across surgeon-year strata, with mean improvements ranging from -7.5 to 35 points. A positive correlation was observed between cumulative case volume and improved mean SFPF scores over time for most surgeons. For example, surgeon 5 in 2023 and 2024 recorded both the highest case volume and the greatest functional gains (SFPF, 35 points). Conversely, earlier years and lower-volume surgeons showed more modest gains or even negative improvement trends.

Figure 1.

Mean operation duration for endoscopic spine surgery and mean Short Form Health Survey bodily pain (SFBP) score improvement for each surgeon from 2021 to 2024.

This pattern suggests a learning curve effect in endoscopic decompression, with functional outcomes improving as surgeon experience and procedural frequency increased.

The mean duration of operations varied across the years by surgeons. For endoscopic cases, most surgeons had an increase in the mean improvement in SF-36 scores from 2021 to 2024 (Figure 1). For open microscopic cases, most surgeons demonstrated a similar improvement in SF-36 scores across time (Figure 2).

Figure 2.

Mean operation duration for endoscopic spine surgery and mean Short Form Health Survey social function (SFSF) score improvement for each surgeon from 2021 to 2024.

1. Temporal Trends in Endoscopic Versus Microscopic Lumbar Decompression

We observed an increase in the adoption of ESS during the study period, from 40.2% in 2022 to 93.1% in 2024. This trend likely reflects a combination of factors such as growing surgeon familiarity and preference, rapid technological advances in endoscopic systems, and increasing patient demand for minimally invasive treatments.

Among all 8 surgeons, the proportion of ESS cases became greater than open microscopic cases. This is due to ESS being more ergonomically efficient for both the main surgeon and the surgical team, faster operative time, and shorter hospital stays. Efficient decompression can be achieved with minimal soft tissue damage, reducing the length of hospital stay and recovery time.

2. Operative Time: Learning Curve and Experience

One finding in our study was the initially long mean operative time observed in endoscopic surgeries, particularly during the earlier phases of adoption. In 2022, the mean operative duration for endoscopic decompression was 249 minutes, compared to 150 minutes for open microscopic procedures. This difference was largely attributed to the steep learning curve associated with mastering endoscopic techniques, including the intricacies of equipment setup, navigation under a different optical system, and handling intraoperative challenges through limited working channels.

However, as surgeons gained more experience, operative times for endoscopic cases significantly decreased, reaching a mean of 145 minutes by 2024. The surgical cutting time is likely to be much shorter than 145 minutes, as the time recorded reflects the time needed for general anesthesia, positioning and draping the patient.

We examined the relationship between surgeon experience over time and patient outcomes, focusing on caseload and mean duration of operative time and the magnitude of functional score improvement across 4 SF-36 domains and VAS (Figures 1–6). The analysis was done for all cases (endoscopic and open microscopic) for each surgeon. In the SFPF domain, magnitude of score improvements were generally consistent over time. The SFBP domain showed variable outcomes. Most surgeons had a consistent magnitude of SFBP score improvements, while the others demonstrated a decrease. The Short Form Health Survey general health domain showed stable and small increases in the magnitude of score improvements across the years. For the SFSF, SFRPF, VASLP, and VASBP domains, most surgeons had an increase in magnitude of score improvement over time.

Figure 3.

Mean operation duration for endoscopic spine surgery and mean Short Form Health Survey general health (SFGH) score improvement for each surgeon from 2021 to 2024.

Figure 4.

Mean operation duration for endoscopic spine surgery and mean Short form role function emotional (SFRPF) score improvement for each surgeon from 2021 to 2024.

Figure 5.

Mean operation duration for endoscopic spine surgery and mean visual analogue scale for back pain (VASBP) score improvement for each surgeon from 2021 to 2024.

Figure 6.

Mean operation duration for endoscopic spine surgery and mean visual analogue scale for leg pain (VASLP) score improvement for each surgeon from 2021 to 2024.

Improved familiarity with instrumentation, better preoperative planning, and refined surgical workflows contributed to faster operative times. Hence, structured training programs and mentorship during the adoption of new surgical technologies is important.

It is expected that as endoscopic techniques become more mainstream, operative times will continue to converge with, or even surpass, those of conventional open microscopic surgeries in efficiency.

3. Recurrence and Reoperation Rates

Both groups showed low recurrence and reoperation rates, underscoring the effectiveness and durability of decompression for both techniques. However, recurrence may become more evident with longer follow-up, and future studies are warranted.

4. Strengths and Limitations

This study has several limitations that should be acknowledged. First, its retrospective design inherently introduces heterogeneity and selection bias. The choice between ESS and open microscopic decompression was non-randomized and guided by surgeon judgment, patient anatomy, radiological characteristics, and evolving surgeon experience. Although we restricted the cohort to elective single-level decompression cases and used DID and temporal trend analyses to mitigate confounding, residual selection bias cannot be fully eliminated. In addition, the exact surgical cutting times were also not consistently recorded, and hence the duration used to calculate the mean operative time, which includes draping and placing the patient under anesthesia, is longer than expected based on current literature. Furthermore, other outcomes such as serum creatinine kinase as a muscle inflammatory marker, estimated blood loss and return to work were not recorded, thus limiting the objective assessment of functional recovery in patients. Another key limitation of this study is that ESS was analyzed as a single category despite encompassing technically distinct procedures, including interlaminar and transforaminal approaches. Differences in approach selection, decompression trajectory, and anatomical targets may influence operative complexity, learning curves, and outcomes. These technique-specific differences could not be fully accounted for due to sample size constraints within each subgroup. A further limitation of this study is the substantial loss to follow-up, with outcome data available for approximately half of the cohort at 2 years. This degree of attrition may introduce survivorship bias and limits the strength of conclusions regarding long-term durability of outcomes. Loss to follow-up was primarily related to missed outpatient appointments and inability to re-establish contact in this retrospective dataset, rather than documented adverse outcomes. To address this, long-term results were interpreted with caution and considered alongside short- and midterm outcomes, where data completeness was higher and consistent improvements were observed across both surgical groups. Future multicenter studies with larger sample sizes, prospective designs, predefined follow-up schedules and randomized or propensity-matched cohorts are needed to better control for selection bias and confounding variables. Such studies would provide more robust evidence regarding the comparative efficacy, safety, and learning curve characteristics of ESS versus open microscopic decompression for LSS.