***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 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 and Objectives Adductor canal block ( ACB ) has been suggested as an analgesic alternative to femoral nerve block ( FNB ) for procedures on the knee , but its effect on quadriceps motor function is unclear . We performed a r and omized , blinded study to compare quadriceps strength following adductor canal versus FNB in volunteers . Our hypothesis was that quadriceps strength would be preserved following ACB , but not FNB . Secondary outcomes included relative preservation of hip adduction and degree of balance impairment . Methods The ACB was performed in one leg and the  FNB  in the contralateral leg in 16 volunteers using a r and omized block sequence . For all blocks , 15 mL of 3 % chloroprocaine was injected under ultrasonographic guidance . Maximal voluntary isometric contraction of knee extension and hip adduction was measured at baseline and at 30 and 60 minutes after block . After 60-minute assessment s were complete , the second block was placed . A test of balance ( Berg Balance Scale ) was performed 30 minutes after the first block only . Results Quadriceps strength and balance scores were similar to baseline following ACB . Following FNB , there was a significant reduction in quadriceps strength ( 95.1 % ± 17.1 % vs 11.1 % ± 14.0 % ; P < 0.0001 ) and balance scores ( 56 ± 0 vs 37 ± 17.2 ; P = 0.02 ) compared with baseline . There was no difference in hip adductor strength ( 97.0 % ± 10.8 % vs 91.8 % ± 9.6 % ; P = 0.17 ) . Conclusions Compared with FNB , ACB results in significant quadriceps motor sparing and significantly preserved balance The purpose of this study was to evaluate the functional outcomes of persons who underwent simultaneous bilateral total knee arthroplasty ( TKA )  compared to subjects who underwent unilateral TKA and a healthy control group . Fifteen subjects who underwent primary bilateral TKA and 15 sex , age , and body mass index-matched subjects who underwent primary unilateral TKA were observed prospect ively for 2 years . Subjects in both surgical groups showed significant improvement in Knee Outcome Scores , Short Form 36 physical component scores , Timed Up and Go , and stair-climbing tasks ( P < or= .004 ) . No differences in final outcomes were found between surgical groups . In addition , most 2-year clinical measures were no different between the surgical and control groups . Subjects medically appropriate for bilateral TKA should be afforded this option UNLABELLED Total knee arthroplasty is associated with intense , early post-operative pain . Femoral nerve block is known to provide optimal pain relief but reduces the strength of the quadriceps muscle and associated with the risk of falling . Adductor canal block is almost pure sensory blockade with minimal effect on quadriceps muscle strength . We prospect ively r and omized 100 patients in two groups ' continuous adductor and femoral block group .  Ambulation ability ( Timed up go , 10-m walk , 30 s chair test ) , time to active SLR , quadsticks , staircase competency , ambulation distance was significantly better ( P value < 0.001 ) in adductor canal group whereas pain scores , opioid consumption showed no significant difference . Adductor canal block provided better ambulation and early functional recovery but without superior analgesia than femoral nerve block post TKA . LEVEL OF EVIDENCE Level III , therapeutic study 
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Dear editors : We read with interest the manuscript by Li et al. [ 1 ]  Adductor canal block provides better performance after total knee arthroplasty compared with femoral nerve block : a systematic review and meta- analysis ; however , the authors concluded that the meta- analysis suggested that ACB provide better ambulation ability , faster functional recovery , and better pain control at rest after TKA compared to FNB .