Unicompartmental versus Tricompartmental Knee Arthroplasty with Continuous Adductor Canal and Femoral Nerve Blocks Analgesic Requirements and Implications for Discharge Readiness

Abstract Background: The relative analgesic requirements for tricompartmental (TKA) and unicompartmental (UKA) knee arthroplasty and their effects on discharge readiness remain unexamined when continuous adductor canal and femoral nerve blocks are used for analgesia in the immediate postoperative period. Methods: Data were collected from 2 previously-published clinical trials involving subjects undergoing TKA (n=79) or UKA (n=30) randomized to either an adductor canal or femoral perineural catheter and ropivacaine 0.2% infusion for 2 (UKA) or 3 (TKA) days. Originally, we compared each catheter location (adductor vs. femoral) while holding surgical procedure constant (comparing solely TKAs and solely UKAs). We now compare type of surgical procedure (TKA vs UKA) while holding catheter location (adductor vs. femoral) constant. The primary outcome was the time to attain 4 discharge criteria including pain, opioid requirements, and ambulation/mobilization. Results: For adductor canal catheters, UKA patients reached all 4 discharge criteria in 35 [24—43] hours which was significantly faster than those given TKA who took 55 [43—63] hours (difference: 18h; 95%CI 9 to 28 h; P<0.001). The results were similar for femoral catheters: UKA patients reach all four discharge criteria in 40 [27—58] hours which was significantly faster than those given TKA who took 61 [49—69] hours (difference: 20; 95%CI 4 to 30 h; P=0.009). For both catheter locations, pain scores, opioid requirements, and mobilization endpoints were better with UKA than TKA. Conclusion : UKA induces less pain and requires less opioid than TKA, regardless of perineural catheter location. Consequently, patients who have UKA are ready for discharge sooner.