Lumbar disc prolapse is the most common spinal pathology affecting young age group, particularly between 30 and 50 years old; it accounts for a variety of symptoms including back pain, radicular pain with or without neurological deficit, and eventually patients refractory to conservative management for a minimum of 4 weeks, or having their activities of daily living affected are dealt surgically [10,11,12]. Discectomy performed either through an open approach or by minimally invasive techniques remains the gold standard management solution including hemilaminotomy, flavectomy and discectomy; the success rates of discectomy in the treatment of sciatic pain has been reported to range between 50 and 98% [13,14,15]. Advantages of minimal invasive surgery includes less perioperative pain, early ambulation, shorter hospital stay and early return to work with smaller incision [16,17,18]. Minimally invasive tubular lumbar endoscopic discectomy is a refinement of the standard open microscopic lumbar discectomy technique. Traditional MD surgery requires muscles dissection and retraction which might induce iatrogenic morbidity of the soft tissues in spite of providing greater visualization of dural sac, direct visualization of anatomic structures and obtaining the optimal angle for disc removal; however, ED is associated with tubular retractors which minimizes the tissue injury and ensures that deeper tissues are less exposed to potential pathologic organisms due to restricted surgical field. Despite these claims there is little support in the literature to justify the adoption of ED over standard MD and the issue remains controversial.
It is therefore necessary to discuss the clinical efficacies of both procedures to generate data that might aid surgeons make a better clinical judgement and develop optimal surgical plan. In our study, we tried to evaluate the clinical outcome and efficacy of both microscopic and endoscopic discectomy as minimally invasive approaches for the management of herniated lumbar disc and assess our results in contrast to the literature.
Our study was conducted on 40 patients with symptomatic unilateral lumbar disc prolapse as confirmed on preoperative MRI to whom surgical management was performed through either microscopic or endoscopic approaches then assessed postoperatively.
The mean age of our study cases was 45.7 years; there was a male predominance as of 80% males and 20% female patients.
Follow up assessment for our patients was conducted through the evaluation of the visual analogue score for both back pain and radicular pain, also we used the modified Japanese orthopedic association score evaluation system for lower back pain syndromes.
The mean value of the preoperative VAS for the back pain was recorded 8.6 ± 1.16 for the endoscopic cases and 6.35 ± 1.14 for the microscopic cases, one month postoperatively, there was a statistically highly significant improvement in these mean values being 1.85 ± 1.2 and 2.45 ± 0.51 respectively, yet there was no statistically significant difference on comparing between the two groups; whereas the VAS-B mean values at the end of the postoperative follow up, twelve months after surgery were still showing a statistically highly significant improvement in both groups compared to the preoperative values, they were recorded 1.8 ± 1.32 and 1.2 ± 0.52 respectively denoting a significant postoperative clinical improvement and a favorable surgical outcome, yet there was still no statistically significant difference between both groups.
Our results came in accordance with those stated by Teli et al. , and Asati et al. ; however, other studies as in Anderson  and Arts et al.  described a higher incidence of postoperative low back pain in microscopic discectomy in comparison with the endoscopic approach.
Similarly, the mean values for VAS-S 1 month after surgery showed a statistically significant improvement for both groups when compared to the preoperative values, the MD group mean values improved from 9.75 ± 0.44 pre-operatively to 2.15 ± 0.37, 1 month after surgery, in contrast to 8.58 ± 0.93 and 1.2 ± 1.61 respectively in the ED group. Eventually there was a statistically highly significant improvement of VAS-S values in both groups 1 year after surgery compared to the preoperative mean values, being 0.35 ± 0.49 in the MD group, and 1.8 ± 1.36 in the ED group. No statistically significant difference between both groups were recorded.
In their study comparing the clinical outcome of both endoscopic and microscopic discectomy, Yang et al.  concluded that there were significant intergroup differences in VAS-B recorded values 2 years after surgery being much better among the ED group, the rate of excellent or good outcome was 90.32% with ED group and 78.95% with MD group; they presumed the reason could be because of the lesser surgical trauma in the ED group. However, similar to our study, they found the intergroup differences in VAS-S score mean values two years following surgery to be statistically non significant. Other studies were also in accordance with our results concluding that sciatica in both groups significantly improved and remained satisfactory at the 24-month follow up following surgery [24,25,26].
The mJOA score mean values markedly improved in both groups after surgery, it improved from 8.1 ± 2.1 pre-operatively to 20 ± 2.53 among the MD group 1 month postoperatively, and from 13.4 ± 1.5 to 22.4 ± 2.1 among the ED group, indicating a statistically highly significant improvement; progressive improvement was noted was also noted in both groups 1 year postoperatively where mJOA mean values were recorded 27.35 ± 1.79 and 23.1 ± 1.16 in both groups respectively. These findings point to a significant clinical improvement on comparing between the preoperative and the postoperative results throughout the follow up intervals in both groups. The difference in mJOA score mean values between both groups was statistically non significant. Liu et al.  also noted a significant postoperative improvement in the JOA scores, VAS scores of low back pain and leg pain at the last study follow up when compared to the preoperative correlates in all the study groups, also, there was no statistically significant difference among the study groups in JOA scores, and VAS scores for leg pain.
For our patients who underwent endoscopic discectomy, the mean operative time was 139.3 ± 55.0 min while for those who underwent micro-discectomy it was 65.75 ± 7.99 min, this statistically highly significant difference could be attributed to our progressively growing learning curve and surgical experience regarding the endoscopic approach, since we noticed that in our initial ED cases have recorded a mean operative time of 173 min while in late cases it was about 93 min. Comparing our results with the literature, Muramatsu et al.  recorded a mean operative time of 105.7 min for their ED cases, whereas Asati et al.  reported a significantly shorter operative time being 82.3 min in the ED group compared to our results, in contrast to 71.5 min in the MD group which is close to our study results for the same group. Mayer and Brock  noted a significantly shorter operative time of 40.7 ± 11.3 in the ED group and 58.2 ± 15.2 min in the MD group.
The mean values of intraoperative blood loss in our study subjects also revealed a statistically highly significant difference on comparing between both groups. We recorded 47.25 ± 14.44 ml (ml) in the MD group and 88.8 ± 22.1 ml in the ED group, and despite of this significant difference, yet no patient needed intraoperative blood transfusion in any of the groups which is considered a rare event in lumbar surgery; the average blood loss in endoscopic approach according to Asati et al.  appeared similar to our recorded value being 82.3 ml, while Wu et al.  study results appear significantly less being 44 ml.
Considering the incidence of operative complications, our study concluded there was no statistically significant difference between both groups. Yang et al.  reported a higher incidence of complications with ED than with MD, yet they described this difference to be non significant and similar to our study results, no major complications were reported. In their MD group, there was a single case of a dural tear that was repaired during surgery, five cases in their ED group and one case in the MD group had postoperative paresthesia, but the symptom disappeared within 4 weeks after treatment with oral mecobalamin. Phan et al.  also noted no statistically significant difference in overall complications, dural tears, root injury or wound infection.