Each patient underwent tracheal intubation under general anesthesia. After installing the appropriate quadrant expandable channel, the soft tissue over the lamina and facet surface was exposed, and the segment was confirmed using a C-arm. Once the microscope was successfully positioned, the unilateral lamina (as determined by the senior surgeon), the inferior and partial superior articular process, the ligamentum flavum, and the intervertebral disc were carefully removed. This procedure decompressed the unilateral spinal canal and exposed the nerve root. A suitable-sized interbody fusion cage was then placed, followed by the insertion of pedicle screws and a connecting rod on the decompression side. The operating table was tilted to the opposite side, and after adjusting the microscope and installing the channel, the base of the spinous process and the contralateral portion of the lamina were removed. A laminar rongeur was used to dissect the ligamentum flavum until the contralateral nerve root was exposed. Pedicle screws and a connecting rod were then inserted on the opposite side. Finally, wound drainage was applied, and the incision was closed in layers.

Postoperatively, all patients received neurotrophic drugs, muscle relaxants, and painkillers based on their symptoms. Patients were instructed to use a hard bed and wear a waist brace during daily activities for 3 months. They were also advised to avoid prolonged standing or strenuous physical labor. At the three-month follow-up visit, they were evaluated in the outpatient department, where their maximum walking distance was recorded, and they were allowed to remove the waist brace based on their tolerance. A similar assessment was conducted at the one-year follow-up visit.

Baseline data, including age, gender, BMI, smoking status, diabetes, operation segment, operation time, and hospital stay, were collected from medical records. Pain was assessed using the Visual Analogue Scale (VAS), which was recorded preoperatively, immediately postoperatively, and at 1-month and 1-year follow-up visits. Lumbar function was evaluated using the Oswestry Disability Index (ODI) and maximum walking distance (MWD), both recorded at the same time points (10). Additionally, inflammatory markers, including C-reactive protein (CRP) and white blood cell (WBC) count, were analyzed.

Complications were identified from medical records. Major complications, defined as those that adversely affected recovery or required intervention, included incision suppuration, cerebrospinal fluid leakage, intraspinal hematoma, internal fixation failure, and delayed bone union. Other complications, including incision redness, swelling, and pain, were classified as minor. All major second surgical procedures for the operated segment during unplanned returns to the inpatient department were defined as reoperations.

All data were analyzed using SPSS 20.0 (Chicago, IL, USA) and presented as percentages or means ± standard deviations. Categorical variables, including gender, smoking, diabetes, complications, and reoperation rates were analyzed using Fisher's exact tests or Chi-square tests, as appropriate. Measurement data, including age, BMI, operation time (OT), length of hospital stay (LOS), VAS, ODI, and MWD, were compared using dependent t-tests. Linear logistic regression was used to evaluate the relationship between obesity and clinical outcomes, with results presented as odds ratios (OR) and 95% confidence intervals (CI). Kaplan–Meier survival curves were used to illustrate the relationship between complications, reoperations, and time in both groups. A P-value < 0.05 was considered statistically significant.

Epstein et al. provided the radiological description of LCS in 1977 (11). Stenosis refers to any type of narrowing of the spinal canal, nerve root canal, or intervertebral foramina, which can be caused by bone or soft tissue changes. The narrowing can affect the bony canal, the dural sac, or both. Multiple factors contribute to the development of spinal stenosis, often acting synergistically to exacerbate the condition. Degeneration of the intervertebral disc often causes protrusion, leading to ventral narrowing of the spinal canal. Additionally, the height of the intervertebral space decreases, further narrowing the recess and intervertebral foramina, and increasing the strain on the facet joints. Increased load can lead to facet joint arthrosis, hypertrophy of the joint capsules, and the development of expanding joint cysts, resulting in spinal instability (12). Moreover, the decrease in intervertebral height also contributes to hypertrophy of the ligamentum flavum.

LCS can lead to the compression of nerve roots, meninges, intraspinal vessels, and, in rare cases, the cauda equina. During physical activity, reduced arterial blood flow can cause ischemia, whereas venous congestion and nerve compression can lead to secondary perfusion deficiency, resulting in claudication (13, 14).

Approximately 24–89 million females and 39–125 million males worldwide were obese in 2016 (15). Nishida et al. reported that obesity is a global health concern that promotes chronic low-grade inflammation, leading to insulin resistance (16). Sakai et al. analyzed the characteristics of 1,119 patients aged over 65 years who were treated for LCS and found that insulin resistance is a significant risk factor for ligamentum flavum hypertrophy (17). In contrast, Rigsby et al. collected baseline and six-month abdominal MRIs from 98 overweight or obese but otherwise healthy subjects, examining the relationship between dorsal epidural fat volumes and BMI. They found that a one-point increase in BMI corresponded to a 45 mm³ increase in dorsal epidural fat volume (P < 0.001, 95% CI: 31.87–76.77) (18). Therefore, obese patients are more likely to develop LCS. Besides, obese increases mechanical load, which accelerates lumbar degeneration. It is reported that lumbar IVD deformation following treadmill walking increases with increasing BMI (19). This persistent mechanical damage accelerates the loss of water in the nucleus pulposus and the decrease in the elasticity of the annulus fibrosus, leading to disc bulging or protrusion, which in turn directly occupies the spinal canal space.

In this study, we collected patient data and found that the NOB group achieved significantly better improvement in VAS scores (1.2 ± 0.4 vs. 1.8 ± 1.7, P < 0.05) at the 1-month follow-up compared to the OB group. Additionally, significantly better recovery in ODI scores was observed in the NOB group at the 3-month (16.5 ± 1.8 vs. 18.3 ± 2.9, P < 0.05) and 1-year (13.6 ± 1.7 vs. 15.5 ± 2.8, P < 0.05) follow-ups compared to the OB group. Regarding MWD, the OB group showed significantly lower MWD at each time point compared to the NOB group (P < 0.05). Onyekwelu et al. compared the clinical outcomes of 2,447 patients treated with lumbar spinal surgery, of whom 1,266 were obese and 1,181 were non-obese. They found that the non-obese patients had significantly better recovery in ODI scores and less blood loss (P < 0.05) (20). Moreover, Kaplan–Meier survival curves for BMI, complications, and reoperations were analyzed, with the NOB group exhibiting significantly better outcomes compared to the OB group (P < 0.05). Similarly, Divi et al. reported contrasting outcomes in a study involving 366 patients treated with lumbar fusion surgery, who were classified into four groups based on BMI. They found no significant differences among the groups, although patients with the highest BMI tended to experience more complications (21).

Linear logistic regression analysis revealed a moderate relationship between BMI and VAS/ODI scores. However, BMI emerged as a risk factor for unfavorable MWD outcomes at each time point (P < 0.05). Possible explanations for this include: (1) Obesity leads to metabolic dysfunction and increased biomechanical load, which may promote fat infiltration in the paravertebral muscles (22). This excess load on the spine, combined with compromised lumbar support, could account for the decreased maximum walking distance in obese patients; (2) Obese patients are more prone to metabolic dysfunction than normal-weight patients (23). Regarding CRP and WBC levels, obese patients showed significantly higher levels of inflammatory markers preoperatively compared to non-obese individuals (P < 0.05). This trend persisted at both 1-day and 5-day follow-ups (P < 0.05). He et al. reported that obese patients often exhibit metabolic dysfunction, which includes elevated adipokines and hyperglycemia. These factors may contribute to increased oxidative stress, which in turn activates inflammatory and coagulation pathways, making obese individuals more susceptible to perioperative complication (24). Obesity is not a limiting factor in surgical consideration, although obesity is associated with poorer surgery outcome. It was reported that obese population achieve considerable reduction in weight following decompression surgery for LCS, which further results in reduction in the risk of metabolic diseases (25). Besides, percutaneous endoscopic lumbar discectomy (PELD) maybe a better surgical approach for obese adolescents. A study found that PELD achieves similar outcomes in obese and normal adolescent patient with lumbar disc herniation (26). It is recommended that the patients with obesity undergo a longer rehabilitation training period and strengthen weight management after lumbar surgery.

In conclusion, obese patients may experience unfavorable functional outcomes after lumbar decompression surgery compared to those with a normal weight. The presence of excess body fat and an elevated proinflammatory state may lead to a higher incidence of perioperative complications in obese individuals. Additionally, the increased mechanical stress on the spine and insufficient lumbar support could contribute to a reduced walking capacity. Clinically, it is crucial to provide extra care for obese patients, focusing on effective wound management and encouraging weight loss as part of their overall treatment plan.