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Volume:5 Issue:4 Number:66 ISSN#:2564-2537
ACE Report #8414

Lower pain with FN Block + SN Block versus FN Block + LIA following TKA

How to Cite

OrthoEvidence. Lower pain with FN Block + SN Block versus FN Block + LIA following TKA. ACE Report. 2016;5(4):66. Available from: https://myorthoevidence.com/AceReport/Report/8414

Study Type:Therapy
OE Level Evidence:1
Journal Level of Evidence:N/A

Femoral nerve block-sciatic nerve block vs. femoral nerve block-local infiltration analgesia for total knee arthroplasty: a randomized controlled trial

BMC Anesthesiol. 2015 Dec 15;15:182

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34 patients scheduled for total knee arthroplasty and receiving continuous femoral nerve block were randomized to be administered a sciatic nerve block (SNB) or local infiltration analgesia (LIA) as part of the postoperative analgesia protocol. The purpose of this study was to evaluate whether there were any significant differences in analgesic efficacy between the two protocols, as assessed by Numeric Rating Scale (NRS) pain scores over the first 24 hours postoperatively. Results demonstrated significantly lower pain scores at 3, 6, and 12 hours postoperatively in the SNB group compared to the LIA group, though the difference in pain score at 24 hours was not statistically significant.

Publication Funding Details +

Risk of Bias


Reporting Criteria


Fragility Index


Was the allocation sequence adequately generated?

Was allocation adequately concealed?

Blinding Treatment Providers: Was knowledge of the allocated interventions adequately prevented?

Blinding Outcome Assessors: Was knowledge of the allocated interventions adequately prevented?

Blinding Patients: Was knowledge of the allocated interventions adequately prevented?

Was loss to follow-up (missing outcome data) infrequent?

Are reports of the study free of suggestion of selective outcome reporting?

Were outcomes objective, patient-important and assessed in a manner to limit bias (ie. duplicate assessors, Independent assessors)?

Was the sample size sufficiently large to assure a balance of prognosis and sufficiently large number of outcome events?

Was investigator expertise/experience with both treatment and control techniques likely the same (ie.were criteria for surgeon participation/expertise provided)?

Yes = 1

Uncertain = 0.5

Not Relevant = 0

No = 0

The Reporting Criteria Assessment evaluates the transparency with which authors report the methodological and trial characteristics of the trial within the publication. The assessment is divided into five categories which are presented below.




Outcome Measurements


Inclusion / Exclusion


Therapy Description



Detsky AS, Naylor CD, O'Rourke K, McGeer AJ, L'Abbé KA. J Clin Epidemiol. 1992;45:255-65

The Fragility Index is a tool that aids in the interpretation of significant findings, providing a measure of strength for a result. The Fragility Index represents the number of consecutive events that need to be added to a dichotomous outcome to make the finding no longer significant. A small number represents a weaker finding and a large number represents a stronger finding.

Why was this study needed now?

Femoral nerve block is a peripheral nerve block that has been used for many years in surgical procedures of the lower limb, such as total knee arthroplasty. More recently, the administration of a sciatic nerve block in addition to femoral nerve block in these procedures has gained attention, along with controversy; there is particular concern regarding motor block, and the possible impact on early mobility and functional recovery, with combined blocks. With the development of local infiltration analgesia as a more recent method of postoperative analgesia in total knee arthroplasty, a comparison of analgesic efficacy between methods, as adjuvants to femoral nerve block, was needed.

What was the principal research question?

In patients undergoing total knee arthroplasty with continuous femoral nerve block, is there any significant difference in pain scores up to 24 hours postoperatively between patients treated with a sciatic nerve block and patients treated with local infiltration analgesia?

Study Characteristics -
34 patients scheduled for unilateral total knee arthroplasty with an American Society of Anaesthesiologists (ASA) physical status of 1-3. Diclofenac 25mg was administered if patients requested analgesics and Numeric Rating Scale (NRS) scores for pain exceeded 3. Pentazocine 15mg intramuscularly was used if diclofenac was unable to maintain pain <3 on the NRS.
LIA group: An ultrasound-guided femoral nerve block was administered with a bolus injection of 20mL 0.375% ropivacaine. Patients were also treated with a local anaesthetic solution containing 100mL 0.2% ropivacaine and 0.5mL (0.5mg) adrenaline; 20mL were injected intracutaneously at the beginning of the procedure; 50mL were used for injection into the vastus intermedius, vastus lateralis, and lateral collateral ligament prior to cementing the prostheses; and 30mL were injected intraarticularly at the end of the procedure. Continuous FNB with 0.2% ropivacaine at 5mL/h was started at the end of the procedure. (n=17, 16 completed; Mean age: 73 +/- 5.9; 3M/13F)
SNB group: Patients were treated with an ultrasound-guided sciatic nerve block with a bolus injection of 20mL 0.375% ropivacaine, after which an ultrasound-guided femoral nerve block was administered with a bolus injection of 20mL 0.375% ropivacaine. Continuous FNB with 0.2% ropivacaine at 5mL/h was started at the end of the procedure. (n=17, 17 completed; Mean age: 72 +/- 10; 2M/15F)
Primary outcome measure was the NRS for pain. Additional outcomes included diclofenac consumption, knee range of motion for flexion and extension, patient satisfaction on a 5-point scale, incidence of postoperative nausea and vomiting, and length of hospital stay.
RCT; single-center, assessor-blind, parallel group
Assessment time points included when patients exited the operating room, and at 3, 6, 12 and 24 hours postoperatively. Patient satisfaction was assessed on the third postoperative day.

What were the important findings?

  • NRS pain scores were significantly lower in the SNB group when compared to the LIA group at 3 (0.06+/-0.24 vs. 2.13 +/- 2.66, respectively; p<0.01), 6 (0.18+/-0.39 vs. 2.5 +/- 2.34, respectively; p<0.01), and 12 (2+/-2.12 vs. 3.5+/-1.83, respectively; p=0.013) hours postoperatively
  • At 24 hours postoperatively, there was no significant difference in NRS pain score between the SNB group (2.47+/-1.59) and the LIA group (3+/-1.86) (p=0.3).
  • There was no significant difference between groups in time to first request of analgesic (p=0.59), or total dose of diclofenac administered (p=0.28). No patient required pentazocine.
  • Postoperative nausea or vomiting occurred in 4 patients of each group (p=0.92). Patient satisfaction on POD3 was similar between groups (p=0.75), and groups demonstrated similar hospital length of stay (p=0.69).
  • There were no significant differences between groups in range of motion (extension p=0.89 and flexion p=0.59) or Knee Society Score (p=0.86)

What should I remember most?

Following total knee arthroplasty with continuous femoral nerve block, pain scores over the first 12 postoperative hours were significantly lower in patients who had been administered a sciatic nerve block when compared to patients who were administered local infiltration analgesia. Pain scores at 24 hours postoperatively were similar between groups. No significant differences between groups were noted in time to first analgesic request, or total dose of diclofenac received.

How will this affect the care of my patients?

The results of this study suggest that sciatic nerve block in addition to femoral nerve block may have greater analgesic efficacy compared to local infiltration analgesia in addition to femoral nerve block, with effects noted over the initial 12 hours after surgery. The authors acknowledge that the current protocol of local infiltration analgesia may not be the most optimal, and that additional randomized controlled trials should be considered to identify which local anaesthetic mixture and administration method offers the maximum analgesic efficacy. Additionally, no mention of motor weakness or falls was recorded, which can a concern with motor blockade as a result of peripheral nerve blocks in the setting of TKA.

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