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RCT
ACE Report #7400

Adductor canal block for management of postoperative pain after revision knee arthroplasty


Study Type:Therapy
OE Level Evidence:2
Journal Level of Evidence:N/A

Adductor canal block for postoperative pain treatment after revision knee arthroplasty: a blinded, randomized, placebo-controlled study

PLoS One. 2014 Nov 11;9(11):e111951

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Synopsis

36 patients scheduled to undergo revision total knee arthroplasty were randomly assigned to adductor canal block with ropivacaine or placebo. The purpose of this study was to evaluate whether an adductor canal block reduced postoperative pain to a significant degree. The primary outcome of interest was VAS pain during knee flexion at 4 hours postoperatively. Results indicated a significantly greater reduction in pain at 4 hours postoperatively in the adductor canal block group than the placebo group. However, due to a large dropout rate, the findings from this trial alone cannot support the use of adductor canal block for the management of postoperative pain after revision total knee arthroplasty.

Publication Funding Details +
Funding:
Non-funded
Conflicts:
None disclosed

Risk of Bias

7/10

Reporting Criteria

19/20

Fragility Index

N/A

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.

4/4

Randomization

3/4

Outcome Measurements

4/4

Inclusion / Exclusion

4/4

Therapy Description

4/4

Statistics

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?

As the number of total knee arthroplasty procedures being performed continues to increase, so too are the number of revision surgeries. Typically, a femoral nerve block is used for postoperative pain management after total knee arthroplasty, but it has been associated with weakness in the quadriceps muscle. Instead, an adductor canal block is a sensory nerve block which allows for the preservation of quadriceps muscle strength and mobilization ability. To the authors’ knowledge, no studies regarding postoperative pain management after revision total knee arthroplasty have been done, necessitating this trial comparing the efficacy of adductor canal block and placebo.

What was the principal research question?

In patients undergoing revision total knee arthroplasty, does an adductor canal block reduce postoperative pain when compared with placebo?

Study Characteristics -
Population:
36 patients, between 40 to 85 years of age, scheduled to undergo revision total knee arthroplasty were included in this trial. (n=30 available for primary endpoint analysis
Intervention:
Adductor canal block: An adductor canal block was performed via a catheter placed below the satorius fascia and lateral to the femoral artery. An initial bolus of 30 ml of 0.75% ropivacaine was administered at the end of surgery, followed by another bolus of 15 ml of 0.75% ropivacaine six hours later. Patients were then treated with continuous infusion of 0.2% ropivacaine at a rate of 8 ml/h. Patient-controlled analgesia (PCA) with intravenous morphine was also used for pain control in patients (2.5mg bolus with a 10min lockout; no background infusion). Patients could also be administered an additional 2.5mg IV morphine and/or 0.5mg IV fentanyl if adequate analgesia was not achieved. (N=14, 11 patients completed final follow-up; Mean age 65 (50-78); Gender 8M/6F)
Comparison:
Placebo: Participants were treated the same as described above, but with placebo saline instead of ropivacaine. PCA was also similarly used in this group. (N=16, 13 patients completed final follow-up; Mean age 67 (42-83); Gender 8M/8F)
Outcomes:
The primary outcome of interest was pain during 45-degree knee flexion at 4 hours postoperative. Other outcomes of interest were pain at rest (1-8 h and at 24 h), cumulative morphine consumption (0-24 h, 0-8 h and 8-24 h), number of vomiting episodes, ondansetron consumption, and degree of nausea and sedation (mean, 1-8 h and 24 h).
Methods:
RCT: Double-blinded (patients & assessors), placebo-controlled
Time:
Outcomes were assessed at 1, 2, 4, 6, 8, and 24 hours postoperatively.

What were the important findings?

  • VAS pain score during flexion of the knee at 4 hours postoperatively was significantly higher in the placebo group than the adductor canal block group (71 +/- 25 mm vs. 52 +/- 22 mm, respectively; p=0.04).
  • There were no between group differences in cumulative morphine consumption from 0-25 h (p=0.48), 0-8 h (p=0.97) and 8-24 h (p=0.95).
  • Both groups experienced a similar number of vomiting episodes, ondansetron consumption, and degree of nausea and sedation at all follow-ups.

What should I remember most?

Adductor canal block significantly reduced VAS pain score at 4 hours postoperatively compared with placebo. Cumulative morphine consumption and adverse events were similar between groups.

How will this affect the care of my patients?

Based on the findings of this trial, adductor canal block was able to provide adequate pain relief after revision total knee arthroplasty, but between group differences only occurred at 4 hours postoperatively. Due to a large number of dropouts, the results from this study are underpowered and should be interpreted with caution. Future studies will need to assess a larger sample size before adductor canal block can be recommended.

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