- Design
- double-blind randomised controlled trial with saline sham; Level I
- Population
- 100 patients undergoing ACL reconstruction under general anaesthesia, 50 per arm
- Primary outcome
- opioid consumption in the first 24 hours after surgery
- Effect
- no difference in 24-hour opioid use (P=0.109), 24-hour pain scores (P=0.0804), straight leg raise at 3 hours (P=0.6711), QoR-15 (P=0.6486) or KOOS at one week (P=0.9054)
One hundred patients having anterior cruciate ligament reconstruction under general anaesthesia were randomised, double-blind, to local infiltration analgesia plus an adductor canal block or local infiltration plus a saline sham. The primary outcome was opioid consumption in the first 24 hours.
Nothing separated. Twenty-four-hour opioid consumption did not differ (P=0.109), nor did visual analogue pain scores at 24 hours (P=0.0804), nor straight leg raise at three hours (P=0.6711), nor Quality of Recovery-15 on day one (P=0.6486), nor the Knee Injury and Osteoarthritis Outcome Score at one week (P=0.9054). Intraoperative opioid use was also the same (P=0.127).
The authors' conclusion - local infiltration alone suffices for routine ACL reconstruction - is a reasonable reading, with one caveat worth stating plainly. Fifty patients per arm is small, and the report gives P values without effect sizes or confidence intervals, so this rules out a large benefit rather than any benefit. That said, two of the comparisons sit close to conventional significance in the direction of the block, and a benefit small enough to hide in 100 patients is a benefit small enough to weigh against block time, an extra consent, and the resource cost. For a busy Indian day-surgery list, where theatre turnover and block room availability are the binding constraints, that trade-off usually favours dropping the block.
- Local infiltration analgesia alone is a defensible default for routine ACL reconstruction
- Keep the adductor canal block for cases where infiltration is inadequate or contraindicated, not as routine
- Where you stop doing the block, audit 24-hour opioid use and unplanned overnight stays so the change is checked rather than assumed
- Note that quadriceps function at three hours was equivalent - the theoretical advantage of the adductor canal block over a femoral block was not at issue here
- Do not extrapolate to knee arthroplasty; this trial was in ACL reconstruction only
Why it matters
It removes a block that has become routine in many units without ever having been tested against the infiltration it is added to.
Don't overread it
One hundred patients with P values and no confidence intervals - this excludes a large analgesic benefit, not a modest one.
The statistics, in plain English
Every comparison here is reported as a P value without a confidence interval, which is the weakness of the paper: a P of 0.109 for opioid consumption tells you the difference was not statistically significant, but not how large a difference has been excluded. With 50 patients per arm, that could be a meaningful benefit that the trial was simply too small to detect. A negative result is only as strong as the size of the effect it can rule out, and this one rules out a large effect rather than a small one.
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