***TASK*** the task is to summarize an input biomedical literature in six sentences 
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    Input: Study Design . Retrospective subgroup analysis of prospect ively collected data according to treatment received . Objective . The purpose of this study is to determine whether the duration of symptoms affects outcomes after the treatment of spinal stenosis ( SS ) or degenerative spondylolisthesis ( DS ) . Summary of Background Data . The Spine Outcomes Research Trial ( SPORT ) study was design ed to provide scientific evidence on the effectiveness of spinal surgery versus a variety of nonoperative treatments . Methods . An as-treated analysis was performed on the patients enrolled in SPORT for the treatment of SS or DS .  A comparison was made between patients with SS with 12 or fewer months ' ( n = 405 ) and those with more than 12 months ' ( n = 227 ) duration of symptoms . A comparison was also made between patients with DS with 12 or fewer months ' ( n = 397 ) and those with more than 12 months ' ( n = 204 ) duration of symptoms . Baseline patient characteristics were documented . Primary and secondary outcomes were measured at baseline and at regular follow-up time intervals up to 4 years . The difference in improvement among patients whose surgical or nonsurgical treatment began less than or greater than 12 months after the onset of symptoms was measured . In addition , the difference in improvement with surgical versus nonsurgical treatment ( treatment effect ) was determined at each follow-up period for each group . Results . At final follow-up , there was significantly less improvement in primary outcome measures in SS patients with more than 12 months ' symptom duration . Primary and secondary outcome measures within the DS group did not differ according to symptom duration . There were no statistically significant differences in the treatment effect of surgery in SS or DS patients . Conclusion . Patients with SS with fewer than 12 months of symptoms experienced significantly better outcomes with surgical and nonsurgical treatment relative to those with symptom duration greater than 12 months . There was no difference in the outcome of patients with degenerative spondylolisthesis according to symptom duration Background Decompressive laminotomy is the st and ard surgical procedure in the treatment of patients with canal stenosis related intermittent neurogenic claudication . New techniques , such as interspinous process implants , cl aim a shorter hospital stay , less post-operative pain and equal long-term functional outcome . A comparative ( cost- ) effectiveness study has not been performed yet . This protocol describes the design of a r and omized controlled trial ( RCT ) on ( cost- ) effectiveness of the use of interspinous process implants versus conventional decompression surgery in patients with lumbar spinal stenosis . Methods / Design Patients ( age 40 - 85 ) presenting with intermittent neurogenic claudication due to lumbar spinal stenosis lasting more than 3 months refractory to conservative treatment , are included . R and omization into interspinous implant surgery versus bony decompression surgery will take place in the operating room after induction of anesthesia . The primary outcome measure is the functional assessment of the patient measured by the Zurich Claudication Question naire ( ZCQ ) , at 8 weeks and 1 year after surgery . Other outcome parameters include perceived recovery , leg and back pain , incidence of re-operations , complications , quality of life , medical consumption , absenteeism and costs . The study is a r and omized multi-institutional trial , in which two surgical techniques are compared in a parallel group design . Patients and research nurses are kept blinded of the allocated treatment during the follow-up period of 1 year . Discussion Currently decompressive laminotomy is the golden st and ard in the surgical treatment of lumbar spinal stenosis . Whether surgery with interspinous implants is a reasonable alternative can be determined by this trial . Trial registerDutch Trial register number : Study Design . A prospect i ve study to evaluate the outcomes of 2 different decompressive techniques for lumbar spinal stenosis . Objective . To explore a more effective and less invasive decompression technique without instrument and fusion for lumbar spinal stenosis . Summary of Background Data . The traditional surgical decompression of spinal stenosis involves laminectomy or unilateral laminotomy . Even in unilateral laminotomy cases , 85.3 % had an excellent-to-fair operative result , and the incidence of complications was 9.8 % . Although the addition of instrumentation does not increase the complication rate , but compared to the efficiency , the higher costs was controversial . Minimal invasion and destabilization are recommended . Methods . This prospect i ve study included 152 consecutive patients , sequentially divided into 2 groups ,  underwent Windows technique  ( group A ) and decompressive laminectomy ( group B ) by 2 groups of surgeons . Results . The evaluation of the back pain , leg pain , walking tolerance , and neurologic recovery were performed before surgery and after surgery . In group A , at the final evaluation , the overall results were good to excellent in 89 % ( 68/76 ) of the patients , fair 11 % ( 8/76 ) , and poor 0 % . In group B , at the final evaluation , the overall results were good to excellent in 63 % ( 48/76 ) of the patients , fair 30 % ( 23/76 ) , and poor 7 % ( 5/76 ) . Conclusion . Degenerative spinal stenosis can be decompressed adequately with preserving the posterior elements . The “ Windows technique ” laminoforaminotomy , which obtained satisfactory long-term outcomes with few complications and low cost , can be a st and ard procedure for the surgical treatment of the degenerative spinal stenosis even with slight congenital spinal stenosis Objective To assess whether interspinous process device implantation is more effective in the short term than conventional surgical decompression for patients with intermittent neurogenic claudication due to lumbar spinal stenosis . Design R and omized controlled trial . Setting Five neurosurgical centers ( including one academic and four secondary level care centers ) in the Netherl and s. Participants 203 participants were referred to the Leiden-The Hague Spine Prognostic Study Group between October 2008 and September 2011 ; 159 participants with intermittent neurogenic claudication due to lumbar spinal stenosis at one or two levels with an indication for surgery were r and omized . Interventions 80 participants received an interspinous process device and 79 participants underwent spinal bony decompression . Main outcome measures The primary outcome at short term ( eight weeks ) and long term ( one year ) follow-up was the Zurich Claudication Question naire score . Repeated measurements were made to compare outcomes over time . Results At eight weeks , the success rate according to the Zurich Claudication Question naire for the interspinous process device group ( 63 % , 95 % confidence interval 51 % to 73 % ) was not superior to that for st and ard bony decompression ( 72 % , 60 % to 81 % ) . No differences in disability ( Zurich Claudication Question naire ; P=0.44 ) or other outcomes were observed between groups during the first year . The repeat surgery rate in the interspinous implant group was substantially higher ( n=21 ; 29 % ) than that in the conventional group ( n=6 ; 8 % ) in the early post-surgical period ( P<0.001 ) . Conclusions This double blinded study could not confirm the hypothesized short term advantage of interspinous process device over conventional “ simple ” decompression and even showed a fairly high reoperation rate after interspinous process device implantation . Trial registration Dutch Trial Register NTR1307 Study Design The 2 groups of patients with severe lumbar spinal stenosis were prospect ively compared as a case control study . Objectives This prospect i ve case control study sought to evaluate bilateral microdecompressive laminatomy ( MDL ) for treatment of severe lumbar spinal stenosis . Summary of Background Data Total laminectomy is a general consensus on the therapy of severe spinal stenosis . The authors tried to investigate a new minimal invasive approach . Methods Patients were r and omly divided into 2 groups . In first group , 34 patients underwent total laminectomy ( TL ) for severe lumbar spinal stenosis . In the second group , 37 patients with the same diagnosis underwent bilateral MDL .  The groups were compared for disability , walking distance , degree of postoperative back and leg pain , perioperative complications , and postoperative instability . Radiographic analyses were performed at regular intervals to demonstrate satisfactory decompression . Results Mean follow-up was 5 years . Postoperative computerized tomography and magnetic resonance imaging demonstrated adequate decompressions in both groups . The walking distance , pain control , and disability scores were slightly higher among patients in the MDL group , although these results did not achieve statistical significance . Perioperative complications and postoperative instability were significantly higher in the TL group ( P<0.05 ) . Conclusions Compared with classic approaches , bilateral MDL provides adequate and safe decompression in lumbar spinal stenosis . It significantly reduces clinical symptoms and disability . However , TL shows higher perioperative complications and postoperative instability . To the best of our knowledge , this is the first study to define a bilateral MDL approach to treat the stenotic lumbar spine without a herniated disc Design . A prospect i ve , multicenter observational study . Objectives . 1 ) Identify correlates of the decision to perform arthrodesis in patients undergoing laminectomy for lumbar spinal stenosis . 2 ) Compare symptoms , walking capacity , and satisfaction 6 and 24 months after laminectomy alone and laminectomy with noninstrumented and with instrumented arthrodesis . Background Data . Few prospect i ve studies have compared outcomes of laminectomy alone or laminectomy with noninstrumented or with instrumented arthrodesis in patients with degenerative lumbar spinal stenosis . There is uncertainty regarding the optimal use of arthrodesis and instrumentation . Methods . Two hundred seventy‐two patients under‐going surgery for degenerative lumbar stenosis by eight surgeons at four centers were included in the study cohort . Of these , 37 had noninstrumented and 41 had instrumented arthrodesis .  Logistic regression identified factors associated with arthrodesis . The principal outcomes ‐health status , walking capacity , back and leg pain , and satisfaction with surgery‐were assessed 6 and 24 months postoperatively with univariate and multivariate techniques . Outcomes also were assessed in a restricted cohort of patients with at least 5 mm spondylolisthesis and /or 15 ° scoliosis .  Hospital costs were obtained from a computerized hospital cost accounting system . Results . The major predictor of the decision to perform arthrodesis was the individual surgeon ( P = 0.0001 ) . Noninstrumented arthrodesis was associated with superior relief of low back pain at 6 months ( P = 0.004 ) and 24 months ( P = 0.01 ) . This difference persisted in multivariate analyses , with borderline statistical significance . There were no significant differences in the other outcomes across treatment groups . Mean hospital costs  of laminectomy alone and noninstrumented and instrumented arthrodesis were $ 12,615 , $ 18,495 , and $ 25,914 , respectively ( P = 0.0001 ) . Conclusion . Findings were limited by the small number of participating surgeons , modest sample size that produced P values of borderline significance , and nonr and omized design . With these caveats in mind , the authors conclude : ( 1 ) The individual surgeon was a more important correlate of the decision to perform arthrodesis than clinical variables such as spondylolisthesis . ( 2 ) Noninstrumented arthrodesis result ed in superior relief of back pain after 6 and 24 months . ( 3 ) Instrumented arthrodesis was the most costly option . These results highlight the need for r and omized controlled trials and cost effectiveness analyses of lumbar arthrodesis and instrumentation in patients with degenerative lumbar spinal stenosis We assigned 67 patients with central lumbar stenosis alternately to either multiple laminotomy or total laminectomy . The protocol , however , allowed multiple laminotomy to be changed to total laminectomy if it was thought that the former procedure might not give adequate neural decompression . There were therefore three treatment groups : group I consisting of 26 patients su bmi tted to multiple laminotomy ; group II , 9 patients scheduled for laminotomy but su bmi tted to laminectomy ;  and group III , 32 patients scheduled for , and su bmi tted to , laminectomy .  The mean follow-up was 3.7 years . Bilateral laminotomy at two or three levels required a longer mean operating time than total laminectomy at an equal number of levels . The mean blood loss at surgery and the clinical results did not differ in the three groups . The mean subjective improvement score for low back pain was higher in group I but there was also a higher incidence of neural complications in this group . No patient in group I had postoperative vertebral instability , whereas this occurred in three patients in groups II and III , who had lumbar scoliosis or degenerative spondylolisthesis preoperatively . Multiple laminotomy is recommended for all patients with developmental stenosis and for those with mild to moderate degenerative stenosis or degenerative spondylolisthesis .  Total laminectomy is to be preferred for patients with severe degenerative stenosis or marked degenerative spondylolisthesis 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 
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Non-surgical treatment was generally regarded as ineffective and believed to be less effective than surgical treatment .
Conclusions The current survey demonstrates a wide variety of preferred treatments of symptomatic LSS by Dutch spine surgeons .