Clinical study of risk factors and thresholds for contralateral radicular pain following single-level endoscopic lumbar fusion based on imaging parameters

English Keywords:Spinal endoscopy  Lumbar interbody fusion  Lateral recess  Intervertebral foramen  Radiculalgia

English Abstract:

  【Abstract】 Objectives: To investigate the anatomical predictors of contralateral radicular pain after endoscopic lumbar interbody fusion(Endo-LIF) and to analyze the clinically relevant preoperative risk prediction thresholds. Methods: A retrospective analysis was conducted on 45 patients(presenting with unilateral lower-limb symptoms) treated with Endo-LIF for lumbar spinal stenosis at L4-5. The cohort included 15 males and 30 females, aged 35-74 years(45.0±9.5 years). According to the presence or absence of postoperative contralateral leg pain, the patients were divided into a symptomatic group(n=15) and an asymptomatic group(n=30). All patients underwent preoperative high-resolution CT scan. Mimics software was used to measure the total volume of the contralateral bony lateral recess at L4-5, the volumes of its subregions(2a, 2b, 2b-E, 3, and 3-E), and the volume of the contralateral intervertebral foramen. A multivariable binary logistic regression model(Model 1) was established based on the traditional Huaxi classification of the lateral lumbar spinal canal. Subsequently, a modified subregional classification using the medial border of the pedicle as the anatomical boundary to define the 2b-E and 3-E subregions was applied to construct a second multivariable binary logistic regression model(Model 2). Volumetric parameters were compared between the two groups, and binary logistic regression analysis was performed to determine the predictive contributions of lateral recess and foraminal volumes. Receiver operating characteristic(ROC) curve analysis was used to determine the optimal volumetric thresholds for prediction. The associations between imaging-based anatomical parameters and the occurrence of contralateral radicular symptoms after Endo-LIF were investigated to identify independent risk factors and evaluate their predictive values. Results: Compared with the asymptomatic group, the symptomatic group showed significantly smaller total bony lateral recess volume(593.09±303.91mm3 vs 773.19±246.32mm3), intervertebral foramen volume(1085.65±314.14mm3 vs 1440.16±384.30mm3), subregion 2a volume(48.52±33.24mm3 vs 105.42±63.85mm3), subregion 2b volume(222.51±148.22mm3 vs 304.72±112mm3), subregion 2b-E volume(100.34±38.34mm3 vs 212.35±124.98mm3), and sagittal diameter of the lateral recess(5.86±2.24mm vs 7.65±2.83mm), with statistically significant differences(P<0.05). No significant differences were observed in the transverse diameter of the lateral recess or in the volumes of subregions 3 and 3-E(P>0.05). Binary logistic regression analysis revealed that the lateral recess subregion 2a in Model 1(OR=0.975, 95%CI=0.953-0.998, P=0.032), the lateral recess subregion 2b-E in Model 2(OR=0.973, 95%CI=0.952-0.994, P=0.012), and intervertebral foramen volume(OR=0.997, 95%CI=0.994-0.999, P=0.019) were significantly associated with contralateral radicular symptoms after Endo-LIF and were identified as independent risk factors. ROC curve analysis demonstrated that the volume of lateral recess subregion 2a in Model 1 had significant predictive value(AUC=0.789, 95%CI=0.651-0.926, P=0.002), with an optimal cutoff value of 40.88mm3. In Model 2, both the volume of lateral recess subregion 2b-E and the intervertebral foramen volume showed significant predictive value for postoperative radicular symptoms(P<0.05). Among these, the volume of lateral recess subregion 2b-E demonstrated the best predictive performance(AUC=0.818, 95%CI=0.695-0.941, P=0.001), with an optimal cutoff value of 152.27mm3. Compared with the lateral recess subregion 2a in Model 1(AUC=0.789), subregion 2b-E in Model 2(AUC=0.818) demonstrated superior predictive performance for postoperative contralateral radicular symptoms. Conclusions: Preoperative reduction in the volume of the upper lateral recess on the contralateral side(subregions 2a and 2b-E) and the intervertebral foramen was closely associated with the occurrence of contralateral radicular symptoms following Endo-LIF. In logistic regression predictive models based on a modified anatomical subregional classification, the volume of subregion 2b-E demonstrated the highest predictive performance, surpassing that of both the conventional subregional model and the intervertebral foramen volume.