Comparison of outcomes between conventional lumbar fenestration discectomy and minimally invasive lumbar discectomy: an observational study with a minimum 2-year follow-up

BACKGROUND Different surgical techniques for lumbar discectomy are in vogue. This study compares the outcomes of two techniques for lumbar discectomy, viz. micro lumbar discectomy (LD) and conventional fenestration discectomy. MATERIALS AND METHODS Sixty-six patients who had single-level 'virgin' lumbar disc herniation with unilateral radicular symptoms were included. Of these, 39 had undergone MLD while 27 had undergone fenestration. Outcomes were measured using the visual analogue scale (VAS) for back and leg pain, Japanese Orthopedic Association (JOA) score, Roland-Morris score (RM) improvement and North American Spine Society (NASS) score. All quantitative data were summarised using mean and standard deviation, and qualitative data using proportions. Significance of differences across the two groups in terms of mean scores was assessed using independent sample t test, and the improvement within the same groups was measured using paired t test. Multiple linear regression analysis was done to assess independent predictors of improvement. RESULTS The MLD group showed statistically better outcomes with regard to improvement in JOA score at 6 weeks, 6 months and 2 years. Mean (SD) VAS for lower back ache at 6 weeks, 6 months, and 2 years was better for the MLD group. But the difference noted in VAS for leg pain was not statistically significant across the groups (P = 0.133). The improvement noted in JOA at 2 years postoperatively compared to the preoperative score was 13.67 (2.89) in the MLD group and 12.11 (3.30) in the macrodiscectomy group (P = 0.046).The mean (SD) RM improvement for the MLD group was 79.24% (8.96%) vs 71.72% (16.53), P = 0.02, in the macrodiscectomy group. Mean NASS score for the MLD group was 2.74 vs 2.96 in the conventional group (P = 0.407).The type of surgery was the significant predictor of improvement in JOA score (P = 0.046) even after adjusting for age, sex, level of lesion and the initial JOA score. MLD as the surgical procedure (P = 0.002) and a lower initial JOA score (P = 0.006) were found significantly contributing to the RM improvement. CONCLUSION The study shows that both MLD and fenestration give comparable results at short-term follow-up. There is statistically significant improvement in MLD with regard to improvement in JOA, VAS and RM scores at 2 years. However, the difference is not large and may not be clinically significant.