Sublingual sufentanil versus femoral nerve catheter analgesia with ropivacaine after primary total knee arthroplasty: a randomized, prospective, clinical comparative phase IV trial

Background Total knee arthroplasty (TKA) represents one of the most commonly performed orthopedic procedures and requires structured and effective perioperative pain management. Patients typically present with chronic, long-standing pain that substantially impairs quality of life and necessitates surgical joint replacement. Optimal intraoperative and postoperative analgesia is essential to ensure functional recovery and to minimize the risk of persistent postoperative chronic pain. In this context, the present study compares non-invasive sublingual sufentanil (SUF-SL) with invasive ropivacaine-based regional anesthesia administered via a femoral nerve catheter (ROP-RA) for postoperative pain control following TKA. Methods In this randomized, prospective, phase IV clinical trial, 56 patients were assigned to receive either sublingual sufentanil (SUF-SL) (n = 28; patient-controlled administration of 15 µg sufentanil with a lockout interval of 20 minutes) or ropivacaine-based regional anesthesia via a femoral nerve catheter (ROP-RA) (n = 28; ropivacaine 0.2% administered at a continuous infusion rate of 5 mL/h with an additional 5 mL bolus and a lockout interval of 30 minutes) for 72 hours postoperatively. Pain intensity was assessed three times daily during the first five postoperative days using the Numerical Rating Scale (NRS). Daily mean NRS scores were calculated separately for pain at rest and during physical activity. Adverse effects, additional non-opioid analgesic consumption, perioperative time parameters, and length of hospital stay were also recorded. Results Both SUF-SL and ROP-RA significantly reduced postoperative pain after TKA. At rest, NRS scores decreased from 3.66 ± 1.73 to 1.56 ± 1.53 in the SUF-SL group and from 3.09 ± 1.73 to 1.92 ± 1.31 in the ROP-RA group between the day of surgery and postoperative day 5. During exercise, pain scores decreased from 5.64 ± 2.06 to 2.77 ± 1.90 in the SUF-SL group and from 5.64 ± 1.94 to 3.55 ± 2.01 in the ROP-RA group between postoperative days 1 and 5 (all p < 0.001). Both treatment modalities demonstrated similarly low and mild adverse effect profiles, with no significant differences in the consumption of additional non-opioid analgesics. Induction of anesthesia time was approximately 78.6% longer in the ROP-RA group due to femoral catheter placement (p < 0.001). No significant differences were observed in intraoperative time, postoperative recovery time, or length of hospital stay. Conclusion Sublingual sufentanil (SUF-SL) offers an effective, safe, and non-invasive alternative to ropivacaine-based regional anesthesia (ROP-RA) for postoperative pain control after primary total knee arthroplasty and may be integrated into multimodal, patient-centered pain management strategies. From the patient’s perspective, non-invasive analgesic techniques are often preferred, while from a clinical standpoint, sublingual sufentanil demonstrates a reliable efficacy and safety profile.