lumbar degenerative spondylolisthesis ( lds ) is an acquired slippage of one lumbar vertebra on the lower one as the result of degenerative instability , in the absence of a defect in the pars interarticularis . the disease is frequently seen in middle and old aged female and patients may have no clinical symptoms . most of the time , the symptomatic patients respond well to non - surgical treatments such as lifestyle modification ( reducing environmental pain generators ) , medication , physical therapy , weight reduction , multidisciplinary pain clinics or epidural injection . in refractory cases with intolerable symptoms ( a dramatic decline in quality of life , unresponsive to a reasonable trial of > 3 months conservative treatment , rest pain , progressive neurologic deficit , or sphincter disturbances ) surgery , 70 - 80% of the surgically treated patients have a satisfactory outcome , but due to the continuing degenerative process the results get worse over time . poor prognostic factors commonly quoted for the patients with surgical treatment , include age > 65 years , chronicity of symptoms > 24 months , instrumentation > 4 levels , inability to restore sagittal balance , comorbidities > 4 , preoperative back pain more than leg pain , posterolateral fusion versus 360 degrees , intermittent claudication more than several hundred meters , previous surgery , andinability to fuse . these include indirect reduction alone , decompression alone , decompression plus lumbar fusion with or without instrumentation , decompression and slip reduction plus instrumented fusion . in this study , we aimed to evaluate the surgical outcome of degenerative spondylolisthesis with neural decompression , pedicular screw fixation , and posterolateral fusion . after local institutional review board approval ( code number 88194 ) and based on standard error calculation , this study was carried out on 45 surgically operated patients with refractory lds from august 2008 to january 2011 . our inclusion criteria were lds unresponsive to more than three months aggressive conservative treatment , progressive neurologic deficit ( especially motor deficit ) and a careful clinical and radiological evaluation that confirmed patients complains were due to the lds . we excluded those patients with associated significant comorbidities ( like psychoneurotic disorders , advanced diabetes mellitus , severe untreated hip , or knee osteoarthritis , etc . ) , previous lumbar spine surgery , underlying lumbar congenital or traumatic lesion , and a follow - up period of less than two years . preoperatively , routine standing anteroposterior and lateral views of the lumbosacral spine and magnetic resonance imaging scan were obtained from all patients . this method describes the degree of slip as a percentage of the anteroposterior diameter of the top of the lower vertebra . one of the advantages of this method is its percentage expression ; therefore , differences in radiological magnification and patient s body size do not distort the results . correction rate was calculated as below : slip correction rate ( % ) = ( ( preoperative  postoperative slip percentage)/preoperative slip percentage)100 ) . the patients pain and disability were assessed by a 0 - 10 numerical rating scale ( vas and odi ) questionnaire version 2.1 . the surgical procedure was explained in simple terms to patients and they signed the informed consents . all the surgical procedures were performed by a single surgical team and in the same manner . initially , efficient neural decompression , pedicular screw insertion , and posterolateral spondylodesis were carried out as routinely performed and then vertebral reduction tried . throughout these years , we used a mixture of local bone graft besides matchstick allograft ( 10 pieces 5535 millimeters of freeze dried cortical cancellous matchstick , tissue regeneration corporation ( trc ) , kish , iran ) to achieve posterolateral fusion . at the time of screw insertion , depending on the amount of replacement needed , therefore , with tightening of the proximal screws , the slipped vertebra will come back to the original place . to do this , we first tightened both distal screws ( usually l5 vertebral pedicular screws ) to the longitudinal rods . then , we applied mild distracting force between proximal and distal screws to facilitate the reduction maneuver and later we tightened the proximal screws to draw back the slipped vertebra ( figure 1 ) . 49-year - old man with l4-l5 lds presented with debilitating claudication and pain . one or two days after surgery , the patients began to walk with a rigid lumbosacral orthosis and slip percentages were calculated again . postoperatively , they are followed - up by x - ray and physical examination at 6 weeks and 3 , 6 , 12 months , and then annually . at annual visits , the questionnaires were completed again . to confirm osseous union , we relied on observing the bony bridge between transverse processes on plain anteroposterior and ferguson radiographs . statistical package for the social sciences ( spss ) software version 16 was used for statistical analysis , data management , and documentation . the pearson correlation coefficient was used to measure the linear dependence between the amount of vertebral reduction and clinical ( odi ) improvement . initially , efficient neural decompression , pedicular screw insertion , and posterolateral spondylodesis were carried out as routinely performed and then vertebral reduction tried . throughout these years , we used a mixture of local bone graft besides matchstick allograft ( 10 pieces 5535 millimeters of freeze dried cortical cancellous matchstick , tissue regeneration corporation ( trc ) , kish , iran ) to achieve posterolateral fusion . at the time of screw insertion , depending on the amount of replacement needed , therefore , with tightening of the proximal screws , the slipped vertebra will come back to the original place . to do this , we first tightened both distal screws ( usually l5 vertebral pedicular screws ) to the longitudinal rods . then , we applied mild distracting force between proximal and distal screws to facilitate the reduction maneuver and later we tightened the proximal screws to draw back the slipped vertebra ( figure 1 ) . 49-year - old man with l4-l5 lds presented with debilitating claudication and pain . one or two days after surgery , the patients began to walk with a rigid lumbosacral orthosis and slip percentages were calculated again . postoperatively , they are followed - up by x - ray and physical examination at 6 weeks and 3 , 6 , 12 months , and then annually . at annual visits , the questionnaires were completed again . to confirm osseous union , we relied on observing the bony bridge between transverse processes on plain anteroposterior and ferguson radiographs . statistical package for the social sciences ( spss ) software version 16 was used for statistical analysis , data management , and documentation . the pearson correlation coefficient was used to measure the linear dependence between the amount of vertebral reduction and clinical ( odi ) improvement . we evaluated 45 patients that included 37 ( 82.2% ) women and 8 ( 17.8% ) men . the mean age of the patients at surgery and the mean follow - up period were 58.33.5 years ( ranged 43 - 76 ) and 31.24.8 months ( ranged 24 - 52 ) , respectively . the distribution of the spondylolisthesis levels in our patients was as follows : l4 - 5 ( 35 cases , 75.5% ) , l5-s1 ( 3 cases , 6.7% ) , l3 - 4 ( 3 cases , 6.7% ) , l3-l4-l5 ( 3 cases , 6.7% ) , l2-l3 ( 1 case , 2.2% ) , and l4-l5-s1 ( 1 case , 2.2% ) . the mean pre- and postoperative clinical and radiological indices ( at the last follow - up visit ) are shown in table 1 . the mean slip correction rate was 52.211.6% ( ranged 21 - 95% ) with a mean loss of correction of 4.81.1% ( ranged 0 - 11% ) . slip reduction of more than 5% was obtained in 39 cases ( 86.7% ) , ranged 0 to 31% . pre- and postoperative radiological and clinical characteristics of our patients odi : oswestry disability index , vas : visual analogue scale , comparison based on paired t - test pearson correlation between the amount of vertebral reduction and odi improvement was not statistically significant ( r=0.15 , p=0.322 ) . although regarding to positive r  , one may initially conclude that with more obtaining of vertebral reduction , the more improvement in odi can be achieved ; this correlation was not significant statistically . we did not encounter any significant intraoperative complications , but we had two superficial postoperative wound infections ( 4.4% ) , both in diabetic patients and both responded efficiently to local wound care , antibiotics , and blood sugar control . postoperative implant failure ( screw breakage at the distal level ) was seen in only one patient due to asymptomatic pseudoarthrosis . none of the patients required reoperation . our findings confirm vertebral reduction , neural decompression , posterolateral fusion , and instrumentation with pedicular screws and rods in surgical treatment of patients with refractory lds has resulted in a significant improvement in pain and disability . although vertebral reduction was associated with improved function , we can not find a significant correlation between these two indices statistically . we had carried out a relatively similar study on 23 patients with lds in 2008 and followed them up for an average period of 29 months . in that study , we treated them without any attempt on vertebral reduction . other details of the research were completely alike and odi improved from preoperative 72.2% to 14.4% at the last postoperative visit . in comparison with that study , in the present research ( the same surgical techniques , but with the accomplishment of vertebral reduction ) odi improved from 71.6% to 28.7% . it seems that reduction maneuver in the present study could not lead to significantly better functional outcomes . in another retrospective study conducted by han et al . , they evaluated the clinical outcomes and loss of correction in 37 patients with low grade lds with a mean follow - up period of 36.4 months . for assessing pain and disability improvement , they also used vas and odi , but they also used computerized tomography beside a plain radiograph to appraise fusion status and loss of correction . in their study , they achieved a postoperative reduction rate of 76.4% , although in 34 cases ( 91.9% ) , 5.8% of correction was lost . at the last follow - up visit , odi and their complications included superimposed degenerative scoliosis ( 2 cases ) , upper adjacent segment retrolisthesis ( 1 case ) , screw breakage ( 1 case ) , and postoperative infection ( 1 case ) . in contrast to our study , they could gain more reduction rate , but their loss of correction was also higher . these authors finally recommended reduction , decompression , and posterolateral instrumented fusion , although limited loss of correction commonly occurs . he believed that this indirect force facilitated vertebral reduction . in a study on 32 patients , he and his colleagues momentarily instrumented the upper adjacent vertebra to apply distraction on the instrumented vertebrae and then lumbar interbody fusion was also performed . at the last follow - up visit ( averaged 32 months ) , they reported 81% reduction rate , 100% bony union , and significant improvement in quality of life ( assessed by short form 36 questionnaire ) . bednar in 2002 reported the surgical outcome of lds in 56 patients treated by instrumented fusion and slip reduction without associated laminectomy . they attained clinical and imaging outcomes comparable to previous outcomes published in the literature had been achieved by in situ fusion and laminectomy . the author concluded that laminectomy may not be required in surgical treatment of lds . in the present study , laminectomy was performed routinely , but we also could not find a significant advantage for slip reduction in lds surgery . in 2006 , all the patients were treated by decompression , posterolateral fusion , and stabilization and followed up for more than two years . functional outcomes of surgery between the patients with bony union and pseudoarthrotic cases were similar and they recommended instrumented spondylodesis in the surgical treatment of these patients . there are many controversies about vertebral reduction , spinal sagittal rebalancing , and their relationship with surgical outcome of the patients . overall , most authors seem to agree with re - establishment of the normal anatomy . in this regard , kawakami et al . conducted a study about the effects of lumbar sagittal balance on clinical outcome of surgery in lds . they used l1 axis s1 distance as a radiologic index for evaluating the sagittal balance . they retrospectively assessed 47 patients with a mean follow - up period of 3.6 years and they finally concluded that in the patients with a l1 axis s1 distance more than 35 mm , a reduction of the vertebral slip may advance functional outcome of surgery . in the study we conducted , we could not gain a strong relationship between vertebral reduction and surgical results , although we did not have any neural injury as well . we did not use postoperative computerized tomography for careful evaluation of the fusion mass , although the osseous union is not meant to cure . it would have been better that we could compare two separate groups with and without slip reduction and follow them up for a longer period . the strengths of our study were its acceptable number of patients and follow - up assessment . in the future , it is strongly recommended that a randomized control trial study should be conducted . in conclusion , although spinal decompression with fusion and posterior instrumentation in surgical treatment of the patients with lds result in satisfactory outcome , vertebral reduction can not significantly enhance the clinical improvement .
background : lumbar degenerative spondylolisthesis ( lds ) is a degenerative slippage of the lumbar vertebrae . 
 we aimed to evaluate the surgical outcome of degenerative spondylolisthesis with neural decompression , pedicular screw fixation , reduction , and posterolateral fusion.methods:this before - after study was carried out on 45 patients ( 37 female and 8 male ) with lds operated from august 2008 to january 2011 . 
 the patients pain and disability were assessed by visual analogue scale ( vas ) and oswestry disability index ( odi ) questionnaire . in surgery , we applied distraction force to facilitate slip reduction . 
 all the intra- and postoperative complications were recorded . 
 the paired t - test and pearson correlation coefficient were used for statistical analysis.results:the mean age of patients and mean follow - up period were 58.33.5 years and 31.24.8 months , respectively . the mean slip correction rate was 52.2% with a mean correction loss of 4.8% . 
 preoperative vas and odi improved from 8.8 and 71.6 to postoperative 2.1 and 28.7 , respectively . 
 clinical improvement was more prominent in more reduced patients , but pearson coefficient could not find a significant correlation.conclusion:although spinal decompression with fusion and posterior instrumentation in surgical treatment of the patients with lds result in satisfactory outcome , vertebral reduction can not significantly enhance the clinical improvement .