In this study, we found no significant difference between the two groups regarding the age and gender (Tables 1,2, and 3).
There were significant differences between means of post-operative VAS for back pain between these two groups after one weeks (t = 13.28, P = < 0.001٭) and after 3 months (t = 10.54, P = < 0.001٭), while non-significant differences between two groups after six months of operation (t = 0.00, P = 1.000) and twelve months (t=-1.523.00, P = 0.134)(Fig. 1). This can explain how Microdiscectomy is minimal invasive technique with less tissue damage than open discectomy so the back pain was less in group B in early stages due to less interference with soft and bony tissues.
There were no significant differences between means of post-operative VAS for leg pain between these two groups after one weeks (t = 1.046, P = 0.3) and after 3 months (t = 0.766, P = 0.447) and even 6 months and 12 months (Fig. 2). This will explain that both techniques (open and Microdiscectomy) are effective in decompression of the nerve root and removal the herniated disc fragments.
When we compare the ODI preoperatively and postoperatively through all periods of assessment in both groups A and B, there is significant deference which means that both methods of treatment is effective in achieving excellent functional improvement for patients with symptomatic lumbar disc herniation with no response to conservative treatment. (Figs. 3 and 4),
There were significant differences between means of length of hospital stay and time of returning to sedentary daily activity between these two groups after one weeks (Table 4) with better results in group B because of minimal tissue damage in Microdiscectomy and less pain postoperatively so the patients can discharged home early and can return to daily activity sooner.
There were significant differences between means of VAS for back pain and leg pain in pre-operative and post-operative assessments in four time periods for both groups A and B (Tables 5,6,7, and 8) and these results also showed the effect of both treatment methods as standard for lumbar disc herniation.
Katayama et al. [8] concluded that there is no significant difference between the two groups (conventional and microsurgical techniques) in outcomes based on Japanese Orthopaedic Association (JOA) score and VAS for leg pain as in our study. A statistically significant difference was noted regarding VAS for back pain in the Katayama study, which also has been found in our study.
Huang et al. [9] found a smaller blood loss in the group of patients treated endoscopically when compared to those treated with the classic technique as we found in microdiscectomy, minimal soft tissue dissection and less blood loss.
Kelly et al. [10] concluded that patients undergoing microdiscectomy had less tissue trauma when compared with those who underwent the classic technique; however, no difference could be noted in the clinical response.
Acharya et al. [11] have found good results in 96.5% of patients with minimally invasive lumbar discectomy in primary cases. However, there is no control group for this study.
Findlay et al. [12] retrospectively reviewed a cohort of 88 patients and reported the outcome of microlumbar discectomy at 10 years. They reported an initial success rate of 91% which declined to 83% in 10-year follow-up.
In a controlled randomised trial, Henrikson et al. [13] concluded that there is no significant advantage in postoperative outcomes and duration of hospital stay between conventional fenestration discectomy and microlumbar discectomy. Porchet et al. [14] in an observational study have concluded that there is no difference between the two techniques when patient response outcomes were studied.
Tureyen [15] compared the outcome of single-sided, single-level, first-time lumbar disc herniation treated with and without the help of a microscope in 114 patients followed up for 1 year. They found that MLD had 90% success rate while conventional surgery had 89% success rate.
Majeed et al. [16] showed that both Minimally invasive lumbar discectomy (MLD) and fenestration give comparable results at short-term follow-up. There is a statistically significant improvement in MLD with regard to improvement in JOA, VAS and Roland-Morris (RM) scores at 2 years. However, the difference is not large and may not be clinically significant.
Righesso and colleagues [17] and Ryang et al. [18] reported the results of 2 prospective randomized trials of minimally invasive versus open microdiscectomy in patients with first-time lumbar radiculopathy caused by disc herniation. In both studies the investigators identified no differences in clinical outcome between the groups at a mean follow-up of 16 months as determined by Visual Analog Scale, Oswestry Disability Index, and Short Form- 36 score. It should be noted that a power analysis was not included in either study, and it is possible that these studies were underpowered to identify small differences between groups.
German et al.[19] concluded in their retrospective study, that patients who underwent minimally invasive discectomy were found to have similar perioperative results as those who underwent open microsurgical discectomy. The differences, although statistically significant, are of modest clinical significance.