Design: Randomised, participant- and assessor-blinded trial
Population: 94 patients having primary unilateral total knee arthroplasty
Primary outcome: Opioid consumption 24 to 48 hours after surgery
Effect: Median 30 vs 38.8 mg; 95% CI of difference −22.5 to 7.0 mg, p = 0.213

In a participant- and assessor-blinded trial at a US orthopaedic hospital, 94 patients having primary unilateral total knee arthroplasty received a single-injection adductor canal block with 15 mL 0.25% bupivacaine. One group also received 2 mg perineural dexamethasone; the other received a 50-hour ropivacaine catheter infusion at 8 mL/hour. Both had iPACK, periarticular infiltration and oral multimodal analgesia.

Opioid use at 24–48 hours did not differ: median 30 mg with the catheter versus 38.8 mg with the single shot (95% CI of the median difference −22.5 to 7.0; p = 0.21). Recovery room opioids, satisfaction, stay and function were similar. Knee buckling occurred in 7% of catheter patients and none in the single-shot group.

Within a complete multimodal regimen, the catheter adds equipment, nursing time and buckling risk without measurable benefit. A single shot with dexamethasone is enough for most patients.

Use a single-injection adductor canal block with perineural dexamethasone for primary TKA.
Add iPACK and periarticular infiltration as part of the standard regimen.
Reserve catheters for patients with specific reasons, such as chronic opioid use.
Review whether your unit's catheter pathway is adding cost without benefit.

Why it matters

It removes the case for routine knee catheters when the rest of the multimodal regimen is in place.

The statistics, in plain English

The interval for the difference in medians runs from 22.5 mg less to 7 mg more with the catheter, so a modest benefit is not ruled out, but the trial found no evidence of one. The buckling difference (7% vs 0%) is small in numbers but matters for falls.