surgery is offered to patients with persistent leg pain that is refractory to conservative treatment . the open surgical technique has been described since the early 20 century . since its introduction , newer techniques were developed with the objective of achieving less tissue trauma in a fast and efficient way . with the introduction of the microscope it did not prolong the operation time , and the overall rate of complications was not increased . md gained progressive popularity , as it achieved an equivalent success rate to open discectomy . in the recent times , the evolving enthusiasm surrounding minimally invasive techniques in spinal surgery resulted in the evolution of various percutaneous procedures . subsequently , other minimally invasive techniques involved . in 1997 , foley and smith introduced the minimally invasive technique of transmuscular tubular discectomy ( td ) which is a procedure that combines spinal endoscopy and the techniques used in md . the advantages of minimally invasive techniques include smaller incision , less perioperative pain , early ambulation , short hospital stay , and early return to work . however , td has a steep learning curve in which proper placement of dilators , recognition of anatomy and the use of instruments through the tubular retractors are some of the challenges that must be overcome . the aim of this study was to compare the outcomes including clinical effectiveness , complication rate , and return to work in patients undergoing td with those undergoing conventional md . we also aim to evaluate , analyze , and quantify the learning curve , complication rates and clinical results of endoscopic spine surgery . patients between the ages of 18 and 75 years with sciatica due to single level lumbar disc herniation , lasting more than 68 weeks and refractory to conservative treatment were included in the study . exclusion criteria were patients with congenital narrow canal , multilevel disc herniations , cauda equina syndrome , spondylolisthesis , central canal stenosis , pregnancy , and severe somatic or psychiatric diseases . a retrospective review of records of patients admitted and operated at indian spinal injuries centre which is a tertiary level center between july 2009 and june 2012 revealed 148 cases which could be included in the study . of these , 46 were md cases and 102 td cases . to evaluate the learning curve , td cases were further divided into two groups : group 1 - those undergoing td between july 2009 and december 2010 ( n = 48 ) initial td cases , group 2 - those undergoing td between january 2011 and june 2012 ( n = 54 ) subsequent td cases . md and td were performed by two different surgeons who had several years experience with the open discectomy technique before the study . in brief , patients in the md group underwent a standard midline incision of 34 cm in length and a muscle - stripping approach on the side of the disc herniation . the herniated disc was removed by the aid of microscope magnification [ figure 1 ] . in contrast , the patients in the td group underwent a paramedian incision 1.8 cm in length with a transmuscular approach to the interspace using serial soft - tissue dilators . a tubular retractor was then inserted to maintain surgical access [ figure 2 ] . in both procedures , patients were mobilized the next day and asked to resume their daily routine activities gradually over the next 23 weeks . follow - up data were obtained during follow - up outpatient department visits , physiotherapy records , and telephonic interviews . the variables that were analyzed included the level and side of the procedure , length of stay , estimated blood loss , and operating time . the variables that were recorded for complications included cerebrospinal fluid ( csf ) leak , residual disc requiring reoperations , infection , and neurological injury . residual or retained disc was defined as clinically symptomatic prolapsed disc fragment immediately following lumbar discectomy . clinical outcomes were evaluated by visual analog scale ( vas ) scores for leg and back pain , oswestry disability index ( odi ) scores and modified macnab criteria . back and leg vas and odi scores before surgery ( preoperative ) , at the first follow - up after 7 days from surgery ( postoperative ) , and subsequently at recent follow - up were noted and tabulated in excel sheet . statistical calculations were performed using the student 's t - test for continuous variables and fisher 's exact test for noncontinuous variables . the p values were calculated for statistical significance , and a threshold of p < 0.05 was used to determine statistical significance . table 1 depicts the demographic data of the three groups . demographic profile of the patients in meanstandard deviation mean age in md group was 41.7 years while it was 43 in group 1 and 40.6 in group 2 , respectively . males constituted 63.04% , 68.75% , and 57.4% in md , groups 1 and 2 , respectively . there was no statistical difference in age ( student 's t - test ) and gender ( chi - square test ) between the three groups . the mean follow - up for md group was 19 months , for group 1 was 14 months and for group 2 was 12 months , respectively . prolapsed intervertebral disc at l5-s1 was the predominant level and was present in 52.17% in md , 52.08% in group 1 , and 53.7% in group 2 , respectively . disc fragment prolapse was on the left side in 52.17% of md group , 54.17% of group 1 and 48.14% of group 2 patients . there was no significant difference in level and side of disc prolapse between the three groups according to the chi - square test . duration of pain averaged 17 , 27 , and 23 weeks in md , group 1 , and 2 , respectively . there was a significant improvement in leg pain as measured by vas and odi scores between pre- and post - operative levels in 1 week in the three groups ( p  0.001 ) , but there was no difference in values in between the groups . 82.6% , 54.16% , and 66.66% of patients suffered from back pain in md , groups 1 and 2 , respectively . there was significant improvement in vas scores for back pain in all the three groups at 1 week ( p  0.001 ) . the improvement in td group was more than the md group at 1 week postoperative but it was not statistically significant ( p = 0.614 ) . odi scores shared a similar trend in all the three groups at 1 week postoperatively . modified macnab criteria at first postoperative week also revealed excellent results in 63% , 72.9% , and 79.6% in md , group 1 and 2 , respectively . there was no significant difference while comparing the values between the groups ( p = 0.683 ) . clinical outcomes of patients regarding visual analog scale and oswestry disability index scores average surgical time was significantly shorter in md group ( 91 min ) as compared to early td cases ( 125 min ) but decreased over time , i.e. 108 min in late td group ( p  0.001 ) . average blood loss was significantly higher ( 148 ml ) in md group as compared to 57 ml in group 1 and 41 ml in group 2 respectively ( p  0.001 ) . length of incision as measured from the surgical scar was 1.8 cm in td while it was 3.5 cm in md group . in last 10 of our patients , we calculated prospectively number of c - ram shoots which came to be significantly lower in md group ( 3.39 ) as compared to td group ( 12.48 ) ( p  0.001 ) . average hospital stay in late td ( 1.74 days ) which was significantly less than md group ( 2.81 days ) ( p  0.001 ) . likewise , md patients took 6.96 weeks to return to activity which was higher than early td patients ( 6 weeks ) ( p = 0.156 ) and which significantly decreased to 3.95 weeks in late td group ( p  0.001 ) [ table 3 ] . perioperative factors in meanstandard deviation and comparison between the groups main peroperative complication was dural tear . there were 3 cases ( 6.5% ) of dural tear in md group and five cases ( 10.4% ) in group 1 which decreased to 4 cases ( 7.4% ) in group 2 . residual disc requiring reoperation was seen mainly in group 1 ( 4 [ 8.3% ] ) which decreased to 1 patient ( 1.85% ) in group 2 . there were 2 cases ( 4.3% ) of residual disc in md group ( p = 0.46 ) . there was one case of nerve root injury which led to postoperative extensor hallicus longus ( ehl ) weakness in group 2 , which recovered completely in 2 months . there was no case of wound hematoma or urinary tract infection in any of the groups [ table 4 ] . table 1 depicts the demographic data of the three groups . demographic profile of the patients in meanstandard deviation mean age in md group was 41.7 years while it was 43 in group 1 and 40.6 in group 2 , respectively . males constituted 63.04% , 68.75% , and 57.4% in md , groups 1 and 2 , respectively . there was no statistical difference in age ( student 's t - test ) and gender ( chi - square test ) between the three groups . the mean follow - up for md group was 19 months , for group 1 was 14 months and for group 2 was 12 months , respectively . prolapsed intervertebral disc at l5-s1 was the predominant level and was present in 52.17% in md , 52.08% in group 1 , and 53.7% in group 2 , respectively . disc fragment prolapse was on the left side in 52.17% of md group , 54.17% of group 1 and 48.14% of group 2 patients . there was no significant difference in level and side of disc prolapse between the three groups according to the chi - square test . duration of pain averaged 17 , 27 , and 23 weeks in md , group 1 , and 2 , respectively . table 2 depicts improvement in vas and odi scores in all the three groups . there was a significant improvement in leg pain as measured by vas and odi scores between pre- and post - operative levels in 1 week in the three groups ( p  0.001 ) , but there was no difference in values in between the groups . 82.6% , 54.16% , and 66.66% of patients suffered from back pain in md , groups 1 and 2 , respectively . there was significant improvement in vas scores for back pain in all the three groups at 1 week ( p  0.001 ) . the improvement in td group was more than the md group at 1 week postoperative but it was not statistically significant ( p = 0.614 ) . odi scores shared a similar trend in all the three groups at 1 week postoperatively . modified macnab criteria at first postoperative week also revealed excellent results in 63% , 72.9% , and 79.6% in md , group 1 and 2 , respectively . there was no significant difference while comparing the values between the groups ( p = 0.683 ) . average surgical time was significantly shorter in md group ( 91 min ) as compared to early td cases ( 125 min ) but decreased over time , i.e. 108 min in late td group ( p  0.001 ) . average blood loss was significantly higher ( 148 ml ) in md group as compared to 57 ml in group 1 and 41 ml in group 2 respectively ( p  0.001 ) . length of incision as measured from the surgical scar was 1.8 cm in td while it was 3.5 cm in md group . in last 10 of our patients , we calculated prospectively number of c - ram shoots which came to be significantly lower in md group ( 3.39 ) as compared to td group ( 12.48 ) ( p  0.001 ) . average hospital stay in late td ( 1.74 days ) which was significantly less than md group ( 2.81 days ) ( p  0.001 ) . , md patients took 6.96 weeks to return to activity which was higher than early td patients ( 6 weeks ) ( p = 0.156 ) and which significantly decreased to 3.95 weeks in late td group ( p  0.001 ) [ table 3 ] . there were 3 cases ( 6.5% ) of dural tear in md group and five cases ( 10.4% ) in group 1 which decreased to 4 cases ( 7.4% ) in group 2 . residual disc requiring reoperation was seen mainly in group 1 ( 4 [ 8.3% ] ) which decreased to 1 patient ( 1.85% ) in group 2 . there were 2 cases ( 4.3% ) of residual disc in md group ( p = 0.46 ) . there was one case of nerve root injury which led to postoperative extensor hallicus longus ( ehl ) weakness in group 2 , which recovered completely in 2 months . there was no case of wound hematoma or urinary tract infection in any of the groups [ table 4 ] . various studies have reported on outcomes of md and td and proved them to be better to open discectomy but only few have compared outcomes of md with td . although randomized controlled trials are considered as the strongest evidence , they also have some shortcomings . first , they often involve only a limited section of the typical patient population suffering from the condition and hence have questionable external validity . second , many a times patients are operated only to complete the trial quickly , and all prerequisites are not met . although this study is a retrospective one , it includes data collected at the time of admission , discharge , and recent follow - up . we observed significant difference in operative time , blood loss and number of iitv shoots between each group utilizing bonferroni multiple comparison test . there was significant difference between early and late tubular groups , signifying the learning curve . the study proved equal efficacy of both procedures in reducing leg pain as highlighted by other studies . . the reason could be less tissue trauma due to dilation and thus preservation of the paraspinous muscles . however , some other studies differ on this fact . arts and anderson described increased back pain in td as compared to md group . teli et al . did not find any difference in postoperative back pain between micro , microendoscopic , and open discectomy . return to work was faster in td group , and the value became significant as our experience in the technique increased . hospital stay in td group was also less as compared to md and value was significant between late td and md cases . ( 2.3 days in td vs. 2.1 days in md ) , and was equal in the study by mark . in various reports , prolonged hospital stay in md group can be attributed to ( 1 ) delayed postoperative recovery due to increased back pain ( 2 ) increased blood loss requiring negative suction drain due to which patient had to be kept in hospital for 23 days . the same explanation can be given for delayed return to work in md patients . as we had higher incidence of dural tears and residual disc in early cases of td furthermore , in our earlier cases , we might not have been confident of allowing the patients to return to their activities early . peroperative complication , the majority of which constituted dural tears ( 7.4% in td vs. 6.5% in md ) , and postoperative complications , mainly residual disc were more in td ( 8.3% ) but decreased as we gained experience ( 1.85% in td vs. 4.3% in md ) . various studies have reported the occurrence of dural tear in 420% in td while the incidence in md is less as compared to td cases . we also encountered higher number of residual disc requiring revision surgeries and dural tears in our earlier cases , but as the experience of tubular endoscopic discectomy went through , the percentage started decreasing . the management of dural tears , on the other hand , is simple in td cases as they did not require any closure or application of fibrin glue . soon after the tubular retractor is removed ( within 510 min ) , the tissues fall back , and the small gap is closed so well that there is no space for csf to accumulate . it is now clear from the discussion that td is better than md , but it should be kept in mind that td techniques involve overcoming a steep learning curve . in this study , we have tried to analyze our learning curve by comparing our first 48 cases with the late 54 cases . wang et al . came to the conclusion that 15 cases are required to achieve the learning curve in endoscopic discectomy . however , mcloughin in his study had only evaluated operating time and wang observed the operating time and complications . in our study , we have compared operating time , blood loss , hospital stay , return to work , peroperative , and postoperative complications between early and late groups of td . there was significant reduction in operative time ( < 0.001 ) , blood loss ( < 0.001 ) , and return to work ( 0.001 ) . the reduction in hospital stay ( 0.013 ) and complication rate ( 0.731 ) was not significant . the incidence of residual disc decreased with experience ( 0.13 ) . in our initial cases , we had four cases of residual disc , out of which two were managed by open discectomy , one treated conservatively , and one was treated by redo endoscopic discectomy . in our late cases , i.e. group 2 , we had only one case of residual disc prolapse which was treated conservatively . the field of view through the endoscope is limited which makes it difficult to expose and decompress the nerve root . as we gained experience , even residual discs , initially operated by open or endoscopic discectomy were managed through tubular access . some of the limitations of our study are : ( 1 ) md and td were performed by two different surgeons , thus introducing a bias in the study , ( 2 ) it was a retrospective study , and ( 3 ) number of cases in two groups are different . some key points for safe and successful completion of microendoscopic discectomy are : ( 1 ) correct placement of the k - wire at facet lamina junction , ( 2 ) introduction of the blunt end of the k - wire , ( 3 ) never descend the wire below the level of the lamina , ( 4 ) placement of the tubular retractor under continuous lateral fluoroscopy , ( 5 ) reassessment of the position of the retractor on anteroposterior fluoroscopy , ( 6 ) careful identification of anatomical structures so that facet capsule is not violated hence preventing iatrogenic instability , and ( 7 ) use of burr to remove the part of lamina and facet so as to reach to the culprit disc ( 8) safe detachment of the flavum from the underlying dura through a ball tipped probe ( 9 ) maintenance of effective hemostasis with the help of bipolar cautery . although randomized controlled trials are considered as the strongest evidence , they also have some shortcomings . first , they often involve only a limited section of the typical patient population suffering from the condition and hence have questionable external validity . second , many a times patients are operated only to complete the trial quickly , and all prerequisites are not met . although this study is a retrospective one , it includes data collected at the time of admission , discharge , and recent follow - up . we observed significant difference in operative time , blood loss and number of iitv shoots between each group utilizing bonferroni multiple comparison test . there was significant difference between early and late tubular groups , signifying the learning curve . the study proved equal efficacy of both procedures in reducing leg pain as highlighted by other studies . . the reason could be less tissue trauma due to dilation and thus preservation of the paraspinous muscles . teli et al . did not find any difference in postoperative back pain between micro , microendoscopic , and open discectomy . return to work was faster in td group , and the value became significant as our experience in the technique increased . hospital stay in td group was also less as compared to md and value was significant between late td and md cases . ( 2.3 days in td vs. 2.1 days in md ) , and was equal in the study by mark . in various reports , prolonged hospital stay in md group can be attributed to ( 1 ) delayed postoperative recovery due to increased back pain ( 2 ) increased blood loss requiring negative suction drain due to which patient had to be kept in hospital for 23 days . the same explanation can be given for delayed return to work in md patients . as we had higher incidence of dural tears and residual disc in early cases of td furthermore , in our earlier cases , we might not have been confident of allowing the patients to return to their activities early . peroperative complication , the majority of which constituted dural tears ( 7.4% in td vs. 6.5% in md ) , and postoperative complications , mainly residual disc were more in td ( 8.3% ) but decreased as we gained experience ( 1.85% in td vs. 4.3% in md ) . various studies have reported the occurrence of dural tear in 420% in td while the incidence in md is less as compared to td cases . we also encountered higher number of residual disc requiring revision surgeries and dural tears in our earlier cases , but as the experience of tubular endoscopic discectomy went through , the percentage started decreasing . the management of dural tears , on the other hand , is simple in td cases as they did not require any closure or application of fibrin glue . soon after the tubular retractor is removed ( within 510 min ) , the tissues fall back , and the small gap is closed so well that there is no space for csf to accumulate . it is now clear from the discussion that td is better than md , but it should be kept in mind that td techniques involve overcoming a steep learning curve . in this study , we have tried to analyze our learning curve by comparing our first 48 cases with the late 54 cases . wang et al . came to the conclusion that 15 cases are required to achieve the learning curve in endoscopic discectomy . however , mcloughin in his study had only evaluated operating time and wang observed the operating time and complications . in our study , we have compared operating time , blood loss , hospital stay , return to work , peroperative , and postoperative complications between early and late groups of td . there was significant reduction in operative time ( < 0.001 ) , blood loss ( < 0.001 ) , and return to work ( 0.001 ) . the reduction in hospital stay ( 0.013 ) and complication rate ( 0.731 ) was not significant . the incidence of residual disc decreased with experience ( 0.13 ) . in our initial cases , we had four cases of residual disc , out of which two were managed by open discectomy , one treated conservatively , and one was treated by redo endoscopic discectomy . in our late cases , i.e. group 2 , we had only one case of residual disc prolapse which was treated conservatively . the field of view through the endoscope is limited which makes it difficult to expose and decompress the nerve root . as we gained experience , even residual discs , initially operated by open or endoscopic discectomy were managed through tubular access . some of the limitations of our study are : ( 1 ) md and td were performed by two different surgeons , thus introducing a bias in the study , ( 2 ) it was a retrospective study , and ( 3 ) number of cases in two groups are different . some key points for safe and successful completion of microendoscopic discectomy are : ( 1 ) correct placement of the k - wire at facet lamina junction , ( 2 ) introduction of the blunt end of the k - wire , ( 3 ) never descend the wire below the level of the lamina , ( 4 ) placement of the tubular retractor under continuous lateral fluoroscopy , ( 5 ) reassessment of the position of the retractor on anteroposterior fluoroscopy , ( 6 ) careful identification of anatomical structures so that facet capsule is not violated hence preventing iatrogenic instability , and ( 7 ) use of burr to remove the part of lamina and facet so as to reach to the culprit disc ( 8) safe detachment of the flavum from the underlying dura through a ball tipped probe ( 9 ) maintenance of effective hemostasis with the help of bipolar cautery . the technique of td for symptomatic lumbar radiculopathy is a safe and an effective procedure and is better than md in terms of reduced postoperative back pain , blood loss , shortened hospital stay , and faster return to work . there is , however , a significant experience - related learning curve in terms of complication rate and operative time . to avoid these complications , it is recommended to have extensive experience in conventional open procedure before attempting this technique . meticulous attention must be paid toward accurate anatomic positioning , careful dissection , and manipulation of the nerve root and disc material , and hemostasis . despite the learning curve , td has been shown to be an effective option in the treatment of lumbar disc herniation in the appropriately selected patient .
objectives : various types of minimally invasive techniques have been developed for the treatment of lumbar disc herniation . 
 the original laminectomy was refined into microdiscectomy ( md ) . 
 md is the gold standard in management of lumbar disc herniation and is used as a yardstick for comparison with newer procedures such as tubular discectomy . 
 so far , no studies have been reported in indian population comparing tubular discectomy and microdiscectomy . 
 the aim of this study was to compare immediate postoperative and 1-year outcome of patients undergoing tubular discectomy with those undergoing md and to evaluate the learning curve as well as complication rates of tubular discectomy.materials and methods : forty - six patients of md and 102 ( 48 early and 54 late ) patients of tubular discectomy ( td ) were operated at indian spinal injuries centre , which is a tertiary level center between july 2009 and january 2012 . 
 they were studied for the following data : baseline characteristics , visual analog scale ( vas ) for leg pain and back pain , oswestry disability index ( odi ) scores , length of hospital stay , time taken to return to work , duration of surgery , intra- and post - operative complications , and reoperation rates.results:the vas score for leg pain , back pain , and odi scores showed improvement in both groups during the 1st year after surgery . 
 time taken to return to work and mean hospital stay was shorter in case of td as compared to md group . 
 the mean duration of surgery was 34 min shorter for conventional md . 
 the incidence of dural tear was 6.5% in md group and 10.4% in early td and decreased to 7.4% in late td group.conclusion:this study revealed that rate of recovery is significantly faster for td as compared to conventional md . 
 in contrast , we encountered fewer complications in md approach as compared to td which although were not statistically significant and which also decreased as we gained experience .