Ultrasound-guided single injection versus continuous sciatic nerve blockade on pain management and mobilisation after total knee arthroplasty (CoSinUS trial): A randomised, triple-blinded controlled trial.

BACKGROUND: Combining continuous femoral nerve blockade with single injection sciatic nerve blockade is standard peripheral nerve block practice for total knee arthroplasty (TKA) during the first 24 postoperative hours.

OBJECTIVES: To assess the analgesic benefits and mobilisation capability of continuous sciatic blockade in conjunction with continuous femoral nerve blockade for 72 h after arthroplasty.

DESIGN: Randomised, triple-blinded controlled trial.

SETTING: Single-Centre, German University Hospital.

PATIENTS: In total, 50 patients receiving continuous femoral nerve blockade (5 ml h ropivacaine 0.2%) for TKA under general anaesthesia.

INTERVENTIONS: Patients were randomised to receive a sciatic nerve catheter with an initial dose of 10 ml ropivacaine 0.2% followed by either continuous double-blinded application of 5 ml h ropivacaine 0.2% (CO) or 5 ml h saline infusion (SIN).

MAIN OUTCOME: Measures primary endpoint: cumulative morphine consumption until 48 h postoperatively. Further endpoints included morphine consumption, pain scores, mobilisation, dynamometry until postoperative day 3.

RESULTS: Median [25th to 75th percentiles] cumulative morphine consumption at postoperative day 2 differed significantly between groups (CO 15 mg [11 to 25] versus SIN, 43 mg [27 to 67.5, P < 0.0001) in the 48 patients in the final analysis. Overall pain scores were comparable at rest and during stress at each time point. However, significantly higher pain scores of the popliteal fossa were observed in the SIN group. Mobilisation was comparable between groups.

CONCLUSION: This trial demonstrates the superior analgesic effects of continuous sciatic nerve block compared with a single injection in combination with continuous femoral blockade during the first 72 h after TKA. However, mobilisation capability was impaired in both groups. Improved pain control from two catheters needs to be balanced against the potential risks of impaired mobilisation and patient falls.

TRIAL REGISTRATION: DRKS - German clinical trials register (no: DRKS00010152).