Characteristics of relief and residual low back pain after discectomy in patients with lumbar disc herniation: analysis using a detailed visual analog scale

Abstract

Background: Several authors have reported favorable results in low back pain (LBP) for patients with lumbar disc herniation (LDH) treated with discectomy. However, detailed changes over time in the characteristics and location of LBP before and after discectomy for LDH remain unclear. To clarify these points, we conducted an observational study to determine the detailed characteristics and location of LBP before and after discectomy for LDH, using a detailed visual analog scale (VAS) bilaterally.

Methods: We included 65 patients with LDH treated by discectomy in this study. A detailed VAS for LBP was administered with the patient under 3 different conditions: in motion, standing, and sitting. Bilateral VAS was also administered (affected versus opposite side) for LBP, lower extremity pain (LEP), and lower extremity numbness (LEN). The Oswestry Disability Index (ODI) was used to quantify clinical status. Changes over time in these VAS and ODI were investigated. Pfirrmann grading and Modic change as seen by magnetic resonance imaging (MRI) were reviewed before and 1 year after discectomy to determine disc and endplate condition.

Results: Before surgery, LBP on the affected side while the patients were in motion was significantly higher than LBP while they were sitting (p = 0.025). This increased LBP on the affected side in motion was improved significantly after discectomy (p < 0.001). By contrast, the residual LBP while sitting at 1 year after surgery was significantly higher than the LBP while they were in motion or standing (p = 0.015). At 1 year following discectomy, residual LBP while sitting was significantly greater in cases showing changes in Pfirrmann grade (p = 0.002) or Modic type (p = 0.025).

Conclusions: Improvement of LBP on the affected side while the patient is in motion suggests that radicular LBP is improved following discectomy by nerve root decompression. Furthermore, residual LBP may reflect increased load and pressure on the disc and endplate in the sitting position.

Keywords: Lumbar disc herniation; Radicular low back pain; Residual low back pain; Visual analog scale.

Fig. 1

VAS scores. a Detailed LBP VAS (0–100 mm) scores. LBP was scored independently under 3 different postural conditions: in-motion, standing, and sitting. b LBP, LEP, and LEN VAS (0–100 mm) scores bilaterally on the approached and opposite sides

Fig. 2

a Changes in LBP during motion and surgical levels. LBP during motion at 1 year after surgery was significantly greater in cases of herniation at the L3/4 level (*one factor ANOVA, F = 11.87, p < 0.001). b Changes in LBP while sitting and surgical levels. LBP while sitting at 1 year after surgery was also significantly greater in cases of L3/4 herniation level (†one factor ANOVA, F = 6.735, p = 0.002)

Fig. 3

a Changes in LBP during motion and surgical procedures. b Changes in LBP while sitting and surgical procedures. C: conventional discectomy, T: microscopic discectomy using a tubular retractor, B: bilateral laminectomy and discectomy. LBP both during motion and while sitting before surgery were significantly greater in group T (*one factor ANOVA, F = 3.246, p = 0.046), and the residual LBP at 3 months after surgery was significantly greater in group T (†one factor ANOVA, F = 7.519, p = 0.001). However, LBP was improved with all 3 surgical procedures and LBP became equally level at 1 year after surgery (one factor ANOVA, F = 0.263, p = 0.770)

Fig. 4

a Relationship between LBP while sitting at 1 year after surgery and Pfirrmann classification changes. PC: Pfirrmann classification changing group, PN: Pfirrmann not changing classification group. Residual LBP while sitting in the PC group was significantly greater than that in the PN group (*student t test, t(60) = 3.138, p = 0.002). b Relationship between LBP while sitting at 1 year after surgery and Modic type changes. MC: Modic type changing group, MN: Modic type not changing group. The residual LBP while sitting in the MC group was significantly greater than that in the MN group (†student t test, t(60) = 2.304, p = 0.025)