***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    Input: Study Design . A prospect i ve clinical study of M-ULBD of lumbar spinal stenosis ( LSS ) . Objective . In this article , the authors describe the technique of M-ULBD for lumbar spinal stenosis , and reported 2-year follow-up results . Summary of Background Data . Recent reports showed that atrophy of multifidus muscles and chronic low back pain after conventional laminectomy may relate to disturbance of the arterial supply caused by long duration of muscle retraction , extensive muscle stripping , and damage to the dorsal rami of the posterior branches . Methods . A total of 56 patients with LSS were r and omly divided into group A and B. The 27 patients in group A ( 15 males and 12 females ) underwent M-ULBD . The other 29 patients in group B ( 18 males and 11 females ) received conventional laminectomy . Japanese Orthopaedic Association score of low back pain , 10-cm visual analogue scale , creatine phosphokinase 3 days after operation , pre- and postoperative cross-sectional areas of multifidus were used to evaluate the clinical results . Results . There was no significant difference in preoperative data between both groups . A total of 54 patients ( 27 in each group A and B ) completed 2 years of follow-up . The postoperative Japanese Orthopaedic Association and visual analogue scale scores in both groups were improved significantly compared with the corresponding preoperative ones ( P < 0.05 ) . The postoperative creatine phosphokinase , visual analogue scale score of low back pain , and atrophy rate of multifidus CSA in group A are lower than those in group B ( P < 0.05 ) . Dural tear at the contralateral side occurred in 3 cases ( 11.1 % ) in group A and 1 case in group B ( 3.4 % ) . Conclusion . Our 2 years of follow-up shows that this method is efficient for lumbar spinal stenosis treatment ; however , it still needs long-term follow-up and needs to be compared with other modified methods . Level of Evidence : OBJECT The authors studied a consecutive series of patients with spinal stenosis in whom surgery was performed by a single surgeon who used a microscopic tubular retractor system ( METRx-MD ) ;  patients underwent prospect i ve evaluation involving radiography and magnetic resonance ( MR ) imaging . The objective was to assess the feasibility and surgery-related efficacy of performing unilateral-approach bilateral decompression and utilization of METRx-MD instrumentation in patients with spinal stenosis . METHODS Seventeen consecutive patients with spinal stenosis underwent bilateral decompression ; surgery was performed via a unilateral approach using METRx-MD instrumentation . The procedures were performed on an outpatient basis after induction of general anesthesia . Preoperative and 3-month follow-up plain radiographs with flexion-extension views were obtained . Preoperative and postoperative MR imaging was also performed . All studies were assessed by a single radiologist blinded to the clinical results . Twenty-two levels were surgically decompressed . The mean operative time was 90 minutes and the mean blood loss was 28 ml per level . Preoperatively stenosis was severe at 13 levels , moderate/severe at eight , and moderate at one . Postoperatively stenosis was absent at 13 levels , mild at seven , mild/moderate at one , and moderate at one . Preoperatively degenerative spondylolisthesis was documented in eight patients , with flexion-extension radiography revealing motion in three cases . On early ( 3-month ) postoperative x-ray films there was no evidence of progression in any case . Grade I spondylolisthesis developed postoperatively in one patient , who remained asymptomatic . CONCLUSIONS Minimally invasive bilateral decompression and instrumentation-assisted fusion can be successfully performed via a unilateral approach in patients with acquired spinal stenosis ; the procedure can be undertaken on an outpatient basis , with reasonable operative times , minimal blood loss , and acceptable morbidity rates This clinical study prospect ively compares the results of open surgery to minimally invasive fusion for degenerative lumbar spine pathologies . Eighty-two patients were studied ( 41 minimally invasive surgery [ MIS ] spinal fusion , 41 open surgical equivalent ) under a single surgeon ( R. J. Mobbs ) . The two groups were compared using the Oswestry Disability Index , the Short Form-12 version 1 , the Visual Analogue Scale score , the Patient Satisfaction Index , length of hospital stay , time to mobilise , postoperative medication and complications . The MIS cohort was found to have significantly less postoperative pain , and to have met the expectations of a significantly greater proportion of patients than conventional open surgery . The patients who underwent the MIS approach also had significantly shorter length of stay , time to mobilisation , lower opioid use and total complication rates . In our study MIS provided similar efficacy to the conventional open technique , and proved to be superior with regard to patient satisfaction , length of hospital stay , time to mobilise and complication rates BACKGROUND CONTEXT Comparative studies between open and minimally invasive surgical ( MIS )  approaches for the treatment of spinal stenosis have mainly investigated immediate postoperative parameters . PURPOSE We aim ed to compare the postoperative improvements in functional and pain scores between open versus MIS lumbar laminotomy and to describe the complications of each method . STUDY DESIGN / SETTING We conducted as retrospective review of prospect ively collected data . PATIENT SAMPLE We included 113 patients . OUTCOME MEASURES Visual analog scale for back and leg pain , Oswestry Disability Index ( ODI ) , the North American Spine Society score on neurogenic symptoms ( NS ) , and average Short Form Health Survey-36 ( SF-36 ) score . Accidental durotomies and patients with reoperations are presented . METHODS We obtained a list of patients who underwent either MIS or open unilateral one-level lumbar laminotomy for the treatment of neural foraminal or lateral recess stenosis with unilateral leg NS . Outcome measures are presented at 6 and 24 months postoperatively . RESULTS From 2000 to 2008 , 113 patients ( 30 open , 83 MIS ) underwent a one-level lumbar laminotomy and had complete postoperative data available for analysis . Between the approaches , there were no differences in baseline demographic data or functional scores . At 6 and 24 months after surgery , there were no differences in improvement in back or leg pain , or improvement in ODI , NS , or SF-36 scores . The MIS group reported greater satisfaction with treatment at 6 months ( p=.009 ) but not at 24 months . Within the MIS group , three patients ( 3.6 % ) experienced an inadvertent durotomy and two patients ( 2.4 % ) underwent fusion of the operated segment within 24 months . CONCLUSIONS Compared with an open approach , MIS lumbar laminotomy gave no clear advantages in longer term functional or pain scores . The MIS group also had patients with inadvertent durotomies and reoperation within 2 years . In any lumbar decompressive surgery , the purported advantages of an MIS approach should be carefully weighed against potential complications . For a relatively simple surgery such as laminotomy , the open approach remains a safe and straightforward option The aim of our study is to evaluate the results and effectiveness of bilateral decompression via a unilateral approach in the treatment of degenerative lumbar spinal stenosis . We have conducted a prospect i ve study to compare the midterm outcome of unilateral laminotomy with unilateral laminectomy .  One hundred patients with 269 levels of lumbar stenosis without instability were r and omized to two treatment groups : unilateral laminectomy ( Group 1 ) , and laminotomy ( Group 2 ) . Clinical outcomes were assessed with the Oswestry Disability Index ( ODI ) and Short Form–36 Health Survey ( SF-36 ) . Spinal canal size was measured pre- and postoperatively . The spinal canal was increased to 4–6.1-fold ( mean 5.1 ± SD 0.8-fold ) the preoperative size in Group 1 , and 3.3–5.9-fold ( mean 4.7 ± SD 1.1-fold ) the preoperative size in Group 2 . The mean follow-up time was 5.4 years ( range 4–7 years ) . The ODI scores decreased significantly in both early and late follow-up evaluations and the SF-36 scores demonstrated significant improvement in late follow-up results in our series . Analysis of clinical outcome showed no statistical differences between two groups . For degenerative lumbar spinal stenosis unilateral approaches allowed sufficient and safe decompression of the neural structures and adequate preservation of vertebral stability , result ed in a highly significant reduction of symptoms and disability , and improved health-related quality of life OBJECT The object of this study was to assess the feasibility and efficacy of a novel , minimally invasive spinal surgery technique to correct degenerative lumbar spinal stenosis involving a modified unilateral-approach microendoscopic midline decompression . METHODS In this prospect i ve study , 41 patients with lumbar stenosis were r and omly assigned to undergo either a novel , median-approach microendoscopic laminectomy ( 20 patients ) or a conventional laminectomy ( 21 patients ) . Spinal anteroposterior diameter , cross-sectional area , lateral recess distance , spinal stability , postoperative back pain , functional outcomes , and muscle trauma were evaluated . Follow-up ranged from 16 to 24 months , with a mean of 17.8 months for the novel procedure group and 18.6 months for the conventional laminectomy group . RESULTS Compared with patients in the conventional laminectomy group , patients who received the novel procedure had a reduced mean duration of hospital stay , a lower mean creatine phosphokinase muscular-type isoenzyme level , a lower visual analog scale score for back pain at 1-year follow-up , and a faster recovery rate . These patients also had less mean blood loss compared with the conventionally treated group . Satisfactory neurological decompression and symptom relief were achieved in 90 % of these patients . There was no significant clinical difference compared with the conventional laminectomy group 's results . There was no evidence of spinal instability in any patient , and no patient required a follow-up conventional laminectomy . CONCLUSIONS This novel procedure provides effective spinal decompression . Although this method requires more operating time than a conventional method , it requires only minimal muscle trauma and spinal stability maintenance , and allows for early mobilization . This shortens the hospital stay , reduces postoperative back pain , and leads to satisfactory neurological and functional outcomes . Moreover , with the midline approach , decompression was accomplished without compromising the facet joints , even with a narrow width of lamina OBJECT Recently , limited decompression procedures have been proposed in the treatment of lumbar stenosis . The authors undertook a prospect i ve study to compare the safety and outcome of unilateral and bilateral laminotomy with laminectomy . METHODS One hundred twenty consecutive patients with 207 levels of lumbar stenosis without herniated discs or instability were r and omized to three treatment groups ( bilateral laminotomy [ Group 1 ] , unilateral laminotomy [ Group 2 ] , and laminectomy [ Group 3 ] ) . Perioperative parameters and complications were documented . Symptoms and scores , such as visual analog scale ( VAS ) , Rol and -Morris Scale , Short Form-36 ( SF-36 ) , and patient satisfaction were assessed preoperatively and at 3 , 6 , and 12 months after surgery . Adequate decompression was achieved in all patients . The overall complication rate was lowest in patients who had undergone bilateral laminotomy ( Group 1 ) . The minimum follow up of 12 months was obtained in 94 % of patients . Residual pain was lowest in Group 1 ( VAS score 2.3 + /- 2.4 and 4 + /- 1 in Group 3 ; p < 0.05 and 3.6 + /- 2.7 in Group 2 ; p < 0.05 ) . The Rol and -Morris Scale score improved from 17 + /- 4.3 before surgery to 8.1 + /- 7 , 8.5 + /- 7.3 , and 10.9 + /- 7.5 ( Groups 1 - 3 , respectively ; p < 0.001 compared with preoperative ) corresponding to a dramatic increase in walking distance . Examination of SF-36 scores demonstrated marked improvement , most pronounced in Group 1 . The number of repeated operations did not differ among groups . Patient satisfaction was significantly superior in Group 1 , with 3 , 27 , and 26 % of patients unsatisfied ( in Groups 1 , 2 , and 3 , respectively ; p < 0.01 ) . CONCLUSIONS Bilateral and unilateral laminotomy allowed adequate and safe decompression of lumbar stenosis , result ed in a highly significant reduction of symptoms and disability , and improved health-related quality of life . Outcome after unilateral laminotomy was comparable with that after laminectomy . In most outcome parameters , bilateral laminotomy was associated with a significant benefit and thus constitutes a promising treatment alternative OBJECTIVE To assess the feasibility and efficacy of a novel , minimally invasive spinal surgery technique for the correction of lumbar spinal stenosis involving unilateral approach for bilateral decompression . STUDY DESIGN Cross-sectional observational study . PLACE AND DURATION OF STUDY Neurosurgery Department of PGMI , Lady Reading Hospital , Peshawar , from January to December 2010 . METHODOLOGY A total of 60 patients with lumbar stenosis were r and omly assigned to undergo either a conventional laminectomy ( 30 patients , Group A ) , or a unilateral approach ( 30 patients , Group B ) . Clinical outcomes 
    Output:
    
The pooled evidence suggests ULBD may be associated with less blood loss and shorter stay , with similar complication profiles to the open approach .