- Design
- double-blind randomised controlled trial with saline sham injection, level 1
- Population
- 100 patients undergoing anterior cruciate ligament reconstruction under general anaesthesia
- Primary outcome
- opioid consumption in the first 24 hours after surgery
- Effect
- no significant difference in 24-hour opioid use (P=0.109), pain score (P=0.080), straight leg raise at 3 hours (P=0.671) or one-week knee score (P=0.905)
One hundred patients having anterior cruciate ligament reconstruction under general anaesthesia were randomised double-blind to local infiltration analgesia plus a saline sham injection, or local infiltration analgesia plus a genuine adductor canal block. The primary outcome was opioid consumption in the first 24 hours; secondary outcomes covered pain scores, early quadriceps function, quality of recovery and knee-specific outcome at one week.
Nothing differed. Twenty-four-hour opioid consumption showed no significant difference (P=0.109), nor did visual analogue pain scores at 24 hours (P=0.080), straight leg raise at three hours (P=0.671), Quality of Recovery-15 on day 1 (P=0.649), or Knee Injury and Osteoarthritis Outcome Score at one week (P=0.905). Intraoperative opioid use was also the same (P=0.127).
This is a negative trial that should change a list. An adductor canal block takes theatre time, needs ultrasound and an operator, costs money, and carries a small risk of quadriceps weakness that matters in a knee you are about to rehabilitate. If local infiltration analgesia alone produces the same day-one opioid requirement and the same straight leg raise at three hours, the block is a step that can be removed without anything being lost.
For day-case ACL reconstruction — which is where most of this surgery is going — removing a block shortens the anaesthetic room time and simplifies the pathway. The caveat is that this compared adding a block to good local infiltration, not block against nothing: the infiltration still has to be done properly.
- Drop the routine adductor canal block from anterior cruciate ligament reconstruction where local infiltration analgesia is given well
- Make sure the infiltration technique is standardised before removing the block — the comparator here was not 'no analgesia'
- Reclaim the anaesthetic room time this frees, particularly on day-case lists
- Keep the block available for the patient in whom infiltration is inadequate or contraindicated
- Track 24-hour opioid use locally after the change, so the decision is verified rather than assumed
The statistics, in plain English
Every outcome was non-significant and several were far from the threshold — P=0.905 for knee score at one week, P=0.671 for straight leg raise — which is more persuasive than a single borderline result. With 50 per arm, a small analgesic benefit could still be missed; the pain score at 24 hours (P=0.080) is the one number that hints at a difference the trial was too small to resolve. But a benefit too small for 100 patients to detect is not a benefit worth an extra procedure.
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