***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 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background and Objectives Femoral nerve block ( FNB ) , a commonly used postoperative pain treatment after total knee arthroplasty ( TKA ) , reduces quadriceps muscle strength essential for mobilization . In contrast , adductor canal block ( ACB ) is predominately a sensory nerve block . We hypothesized that ACB preserves quadriceps muscle strength as compared with FNB ( primary end point ) in patients after TKA . Secondary end points were effects on morphine consumption , pain , adductor muscle strength , morphine-related complications , and mobilization ability . Methods We performed a double-blind , r and omized , controlled study of patients scheduled for TKA with spinal anesthesia . The patients were r and omized to receive either a continuous ACB or an FNB via a catheter ( 30-mL 0.5 % ropivacaine given initially , followed by a continuous infusion of 0.2 % ropivacaine , 8 mL/h for 24 hours ) . Muscle strength was assessed with a h and held dynamometer , and we used the percentile change from baseline for comparisons . The trial was registered at clinical trials.gov ( Identifier : NCT01470391 ) . Results We enrolled 54 patients , of which 48 were analyzed .  Quadriceps strength as a percentage of baseline was significantly higher in the ACB group compared with the FNB group : ( median [ range ] ) 52 % [ 31–71 ] versus 18 % [ 4–48 ] , ( 95 % confidence interval , 8–41 ; P = 0.004 ) . There was no difference between the groups regarding morphine consumption ( P = 0.94 ) , pain at rest ( P = 0.21 ) , pain during flexion of the knee ( P = 0.16 ) , or adductor muscle strength ( P = 0.39 ) ; neither was there a difference in morphine-related adverse effects or mobilization ability ( P > 0.05 ) . Conclusions Adductor canal block preserved quadriceps muscle strength better than FNB , without a significant difference in postoperative pain Background : The authors hypothesized that the adductor canal block ( ACB ) , a predominant sensory blockade , reduces quadriceps strength compared with placebo ( primary endpoint , area under the curve , 0.5–6 h ) , but less than the femoral nerve block ( FNB ; secondary endpoint ) . Other secondary endpoints were adductor strength and ability to ambulate . Methods : The authors enrolled healthy young men into this double blind , placebo-controlled , r and omized , crossover study . On two separate study days , subjects received either ACB or FNB with ropivacaine , and placebo in the opposite limb . Strength was assessed as maximum voluntary isometric contraction for quadriceps and adductor muscles . In addition , subjects performed three st and ardized ambulation tests . Clinical trials.gov Identifier : NCT01449097 . Results : Twelve subjects were r and omized , 11 analyzed .  Quadriceps strength ( area under the curve , 0.5–6 h ) was significantly reduced when comparing ACB with placebo ( 5.0 ± 1.0 vs. 5.9 ± 0.6 , P = 0.02 , CI : −1.5 to −0.2 ) , FNB with placebo ( P = 0.0004 ) , and when comparing FNB with ACB ( P = 0.002 ) . The mean reduction from baseline was 8 % with ACB and 49 % with FNB . The only statistically significant difference in adductor strength was between placebo and FNB ( P = 0.007 ) . Performance in all mobilization tests was reduced after an FNB compared with an ACB ( P < 0.05 ) . Conclusions : As compared with placebo ACB statistically significantly reduced quadriceps strength , but the reduction was only 8 % from baseline . ACB preserved quadriceps strength and ability to ambulate better than FNB did . Future studies are needed to compare the analgesic effect of the ACB with the FNB in a clinical setting Purpose Providing effective analgesia for total knee arthroplasty ( TKA ) patients remains challenging . Femoral nerve block ( FNB ) offers targeted pain control ; however , its effect on motor function , related fall risk and impact on rehabilitation has been the source of controversy . Adductor canal block ( ACB ) potentially spares motor fibres of the femoral nerve , but the comparative effect of the two approaches has not yet been well defined due to considerable variability in pain perception . Our study compares both single-shot FNB and ACB , side to side , in the same patients undergoing bilateral TKA . Methods Sixty patients scheduled for bilateral TKA were r and omised to receive ultrasound-guided FNB on one leg and ACB on the other , in addition to combined spinal epidural anaesthesia . The primary outcome was comparative postoperative pain in either extremity at six to eight , 24 and 48 hours postoperatively . Secondary comparative outcomes included motor strength ( manually and via dynamometer ) , physical therapy milestones and patient satisfaction . Results While pain levels were lowest at six to eight hours postoperatively and increased thereafter ( P < 0.001 ) , no significant differences were seen between extremities at any time point with regard to pain in the quantitative comparison using visual analogue scale ( VAS ) scores ( P = 0.4154 ) , motor strength ( P = 0.7548 ) , physical therapy milestones or patient satisfaction . However , in the qualitative comparison , a significant proportion of patients reported the leg receiving ACB to be more painful than that receiving FNB at 24 h [ 50.9 % ( n = 30 ) vs 25.42 % ( n = 15 ) , P = 0.0168 ) ] . Conclusions Although we could not confirm a benefit in motor function between ACB and FNB , given the equivalent analgesic potency combined with its potentially lower overall impact if neuropraxia should occur , ACB may represent an attractive alternative to FNB Background There are several methods for postoperative analgesia for knee surgery . The commonly utilized method is multimodal analgesia based on continuous femoral nerve block . The aim of this study was to investigate the application of continuous adductor canal block for analgesia after total knee replacement and compare this method with continuous femoral nerve block . Methods Sixty patients scheduled for total knee replacement from June 2013 to March 2014 were r and omly divided into a femoral group and an adductor group . Catheters were placed under the guidance of nerve stimulation in the femoral group and under the guidance of ultrasound in the adductor group . Operations were performed under combined spinal and epidural anesthesia . After the operations , 0.2 % ropivacaine was given at a speed of 5 ml/h through catheters in all patients . Visual analogue scale ( VAS ) pain scores at rest and while moving were noted at 4 , 24 , and 48 hours after the operation , and quadriceps strength was also assessed at these time‐points . Secondary parameters such as doses of complementary analgesics and side effects were also recorded . Results There were no significant differences between the groups in VAS pain scores at rest or while moving , at 4 , 24 , or 48 hours after the operation ( P > 0.05 ) . At these time‐points , mean quadriceps strengths in the adductor group were 3.0 ( 2.75‐3.0 ) , 3.0 ( 3.0‐4.0 ) , and 4.0 ( 3.0‐4.0 ) , respectively , all of which were significantly stronger than the corresponding means in the femoral group , which were 2.0 ( 2.0‐3.0 ) , 2.0 ( 2.0‐3.0 ) , and 3.0 ( 2.0‐4.0 ) , respectively ( P < 0.05 ) . There were no significant differences between the groups in doses of complementary analgesics or side effects ( P > 0.05 ) . X‐ray images of some patients showed that local anesthetic administered into the adductor canal could diffuse upward and reach the femoral triangle . Conclusions Continuous adductor canal block with 0.2 % ropivacaine could be used effectively for analgesia after total knee replacement . Compared with continuous femoral nerve block , this analgesic method has similar analgesic effects and is associated with less weakness of quadriceps muscle Background : This prospect i ve double-blinded , r and omized controlled trial compared adductor canal block ( ACB ) with femoral nerve block ( FNB ) in patients undergoing total knee arthroplasty . The authors hypothesized that ACB , compared with FNB , would exhibit less quadriceps weakness and demonstrate noninferior pain score and opioid consumption at 6 to 8 h postanesthesia . Methods : Patients received an ACB or FNB as a component of a multimodal analgesic . Quadriceps strength , pain score , and opioid consumption were assessed on both legs preoperatively and at 6 to 8 , 24 , and 48 h postanesthesia administration . In a joint hypothesis test , noninferiority was first evaluated on the primary outcomes of strength , pain score , and opioid consumption at 6 to 8 h ; superiority on each outcome at 6 to 8 h was then assessed only if noninferiority was established . Results : Forty-six patients received ACB ; 47 patients received FNB .  At 6 to 8 h postanesthesia , ACB patients had significantly higher median dynamometer readings versus FNB patients ( median [ interquartile range ] , 6.1 kgf [ 3.5 , 10.9 ] ( ACB ) vs. 0 kgf [ 0.0 , 3.9 ] ( FNB ) ; P < 0.0001 ) , but was not inferior to FNB with regard to Numeric Rating Scale pain scores ( 1.0 [ 0.0 , 3.5 ] ACB vs. 0.0 [ 0.0 , 1.0 ] FNB ; P = 0.019 ) , or to opioid consumption ( 32.2 [ 22.4 , 47.5 ] ACB vs. 26.6 [ 19.6 , 49.0 ] ; P = 0.0115 ) . At 24 and 48 h postanesthesia , there was no significant statistical difference in dynamometer results , pain scores , or opioid use between the two groups . Conclusion : At 6 to 8 h postanesthesia , the ACB , compared with the FNB , exhibited early relative sparing of quadriceps strength and was not inferior in both providing analgesia or opioid intake Background Femoral continuous peripheral nerve blocks ( CPNBs ) provide effective analgesia after TKA but have been associated with quadriceps weakness and delayed ambulation . A promising alternative is adductor canal CPNB that delivers a primarily sensory blockade ; however , the differential effects of these two techniques on functional outcomes after TKA are not well established . Questions / purpose sWe determined whether , after TKA , patients with adductor canal CPNB versus patients with femoral CPNB  demonstrated ( 1 ) greater total ambulation distance on Postoperative Day ( POD ) 1 and 2 and ( 2 ) decreased daily opioid consumption , pain scores , and hospital length of stay . Methods Between October 2011 and October 2012 , 180 patients underwent primary TKA at our practice site , of whom 93 % ( n = 168 ) had CPNBs .  In this sequential series , the first 102 patients had femoral CPNBs  , and the next 66 had adductor canal CPNBs . The change result ed from a modification to our clinical pathway , which involved only a change to the block . An evaluator not involved in the patients ’ care review ed their medical records to record the parameters noted above . Results Ambulation distances were higher in the adductor canal group than in the femoral group on POD 1 ( median [ 10th–90th percentiles ] : 37 m [ 0–90 m ] versus 6 m [ 0–51 m ] ; p < 0.001 ) and POD 2 ( 60 m [ 0–120 m ] versus 21 m [ 0–78 m ] ; p = 0.003 ) . Adjusted linear regression confirmed the association between adductor canal catheter use and ambulation distance on POD 1 ( B = 23 ; 95 % CI = 14–33 ; p < 0.001 ) and POD 2 ( B = 19 ; 95 % CI = 5–33 ; p = 0.008 ) . Pain scores , daily opioid consumption , and hospital length of stay were similar between groups . Conclusions Adductor canal CPNB may promote greater early postoperative ambulation compared to femoral CPNB after TKA without a reduction in analgesia . Future r and omized studies are needed to vali date our major findings .Level of Evidence Level III , therapeutic study . See Instructions for Authors for a complete description of levels of evidence Background and Objectives The benefit of adding sciatic nerve block ( SNB ) to femoral nerve block to improve analgesia after total knee arthroplasty ( TKA ) is uncertain . We hypothesized that the effective duration of single-injection SNB is too short to improve postoperative analgesia and that this contributes to conflicting results on the efficacy of SNB after TKA . We evaluated this hypothesis in a prospect i ve double-blind r and omized controlled trial . Methods Sixty patients undergoing TKA were r and omly allocated to a continuous SNB group or a single-injection SNB group . All patients received femoral nerve block ( 0.5 % ropivacaine 20 mL ) and SNB ( 0.2 % ropivacaine 20 mL ) and catheters were inserted into both peripheral nerve block sites before surgery . Both groups received continuous femoral nerve block and patient-controlled intravenous analges 
    Output:
    
There were no significant differences in VAS score with rest or mobilization at 4 , 24 , and 48 h between ACB  group and FNB group .
There were also no significant differences in the strength of quadriceps and adductor , the length of hospital stay , and complications of vomiting and nausea .
Present meta- analysis indicated that ACB shows no superiority than FNB group .
Both of them can reduce the pain score after TKA .