What Is the Association Between Adding Genicular Nerve Block to Adductor Canal Block and Infiltration Between the Popliteal Artery and Capsule of the Knee and Perioperative Outcomes After Primary TKA?

BACKGROUND: Limited evidence exists on the functional and analgesic efficacy of adding a genicular nerve block to an adductor canal block (ACB) plus infiltration between the popliteal artery and posterior knee capsule (IPACK) for TKA. Filling this knowledge gap would be important because if this approach were to be effective, patients could benefit from an additional opioid-free, motor-sparing analgesic modality. QUESTIONS/PURPOSES: (1) Is the addition of a genicular nerve block to an ACB/IPACK associated with better pain management during hospitalization? (2) Is the addition of a genicular nerve block to an ACB/IPACK associated with better pain management in the postanesthesia care unit (PACU)? (3) Is the addition of a genicular nerve block to an ACB/IPACK associated with earlier time to physical therapy (PT) clearance? (4) Is the addition of a genicular nerve block to an ACB/IPACK associated with lower incidence of opioid refills within 90 days postoperatively? METHODS: This was a retrospective, propensity score-matched cohort study including patients undergoing TKA from January 2021 to December 2024 at a high-volume academic institution specializing in inpatient and outpatient arthroplasty. All adults undergoing primary elective unilateral TKA for primary osteoarthritis with administration of an ACB/IPACK, with or without a genicular nerve block, were assessed for eligibility (n = 20,648). After excluding patients with American Society of Anesthesiologists physical status of > III; patients receiving general anesthesia, additional peripheral nerve blocks, or acupuncture; and patients discharged to a facility, a total of 10,156 patients undergoing inpatient TKA and 2814 patients undergoing outpatient TKA were considered eligible for propensity score matching. After a 1:1 propensity score match on baseline demographic characteristics, psychosocial factors, active opioid prior to admission, perioperative and anesthesia details, and first PT visit pass or fail, 2803 and 1102 patients from each group were analyzed for inpatient and outpatient TKAs. The median (IQR) age was 71 years (64 to 76) for inpatient TKAs and 65 years (60 to 71) for outpatient TKAs; 64% and 48% were female, respectively, and no differences among groups within the same setting were observed after matching. Aside for the comparison of interest, the same standardized perioperative pain management protocol was followed for all patients. For our first aim and second aim, we evaluated median and highest pain scores and opioid consumption. For our third aim, we assessed PT clearance, and for our fourth aim, we assessed incidence of opioid refills within 90 days. A difference in pain of ≥ 2 on the numeric rating scale (NRS) and a difference in opioid consumption of ≥ 10 oral morphine milligram equivalents (OMEs) were considered clinically meaningful. For the inpatient setting, a 4-hour median difference in time to PT clearance was considered clinically meaningful, and for the outpatient setting, any statistically significant difference with a median time to PT clearance of < 12 hours for either group was considered clinically meaningful. RESULTS: During hospitalization, we found no difference between the intervention and control group in terms of highest pain and median pain. In terms of total opioid consumption, we found no clinically important difference between the intervention group and control group (median [IQR] NRS score 55 [30 to 82] versus 52 [30 to 80]; p = 0.001) in the inpatient setting and no difference in the outpatient setting. In the PACU, we found no difference in terms of highest pain and median pain in the inpatient setting and no clinically important difference for highest pain (median [IQR] NRS score 7 [5 to 8] versus 7 [6 to 8]; p = 0.03) in the outpatient setting. In the inpatient setting, no clinically important difference was observed between the intervention and control group for opioid consumption (median [IQR] OMEs 53 [30 to 82] versus 48 [25 to 75]; p < 0.001); no difference was observed in the outpatient setting. We found no clinically meaningful difference between the intervention group and control group in terms of time to PT clearance in the inpatient setting (median [IQR] 21 hours [18 to 25] versus 22 hours [19 to 41]; p < 0.001) and the outpatient setting (median [IQR] 13 hours [4 to 16] versus 14 hours [4 to 16]; p = 0.001). We found no difference in terms of incidence of opioid refills within 90 days. CONCLUSION: The associations we found do not justify the addition of a genicular nerve block in patients undergoing inpatient and outpatient TKA with a comprehensive multimodal analgesia protocol given the modest, at best, effect size observed, its potential financial cost and time cost, and risk for adverse events. Our study suggested that there are subpopulations in the general TKA population that could potentially benefit from the addition of genicular nerve block, but until future evidence identifies these subpopulations, our data suggest that the addition of a genicular nerve block was not associated with any clinically meaningful benefit in the general TKA population. LEVEL OF EVIDENCE: Level III, therapeutic study.