Predictive Factors for Residual Low Back Pain Following Percutaneous Endoscopic Lumbar Discectomy in Patients with Lumbar Disc Herniation

Abstract

BACKGROUND Percutaneous endoscopic lumbar discectomy (PELD) is a mature and popular surgery for treatment of lumbar disc herniation (LDH). The main objective of our study was to identify risk factors for residual low back pain after PELD and to improve postoperative management. MATERIAL AND METHODS We retrospectively analyzed the clinical and imaging data of 251 patients who underwent PELD for LDH. We defined residual LBP as visual analog scale (VAS) score for LBP ≥3 at 2 years postoperatively, and severe LBP was defined as VAS for LBP ≥7.5. The clinical and imaging data were analyzed by comparing patients with VAS scores ≥3 and <3, and univariate analysis and multivariable logistic regression analysis were applied to predict the risk factors for residual LBP. RESULTS There were 56 (22.3%) patients with LBP VAS ≥3 at 2 years postoperatively. Multivariable logistic regression analysis demonstrated that severe baseline VAS for LBP (P<0.001), MCs type I (P=0.006), and severe fatty infiltration of the paravertebral muscles (P<0.001) were independent risk factors for residual LBP after PELD. CONCLUSIONS In patients with LDH, MCs type I, severe baseline LBP, and fatty infiltration of the paravertebral muscles were predictive factors for residual LBP after PELD. Our study suggests that spine surgeons should pay more attention to these imaging parameters, which may be a helpful indicator for the choice of surgical modality.

Figure 1

Flow chart showing the inclusion and exclusion of patients. MRI – magnetic resonance imaging; LDH – lumbar disc herniation.

Figure 2

Measurement of the DHI: The height of the anterior a), middle b), and posterior c) intervertebral space and the sagittal diameter of the overlying vertebral body d) were measured. DHI=[(a+b+c)/3]/d.

Figure 3

Measurement of the sROM: The sROM can be calculated by the difference between flexion (A) and extension (B) angles, which was measured in relation to the lines of the superior and inferior endplate of the surgical segment. The sROM is 4.0 degrees at L4–L5 in this patient.

Figure 4

(A, B) The cross-sectional area (CSA) of the paraspinal muscles was measured by drawing the outline of the myofascial boundary as the regions of interest (ROI) at the L4–L5 disc level on axial T2-weighted MRI. The total muscle CSA includes the area of multifidus (MF), erector spinae (ES), and psoas (PS). The fatty infiltration of paraspinal muscles was measured via a threshold method.

Figure 5

The imaging presentations of the three types of Modic changes on MRI, the red arrow indicates where the signal changes. (A) MCs Type I, hypointense on T1WI and hyperintense on T2WI. (B) MCs Type II, hyperintense on T1WI and T2WI. (C) MCs Type III, hypointense on T1WI and T2WI.