Multimodal Pain Management With Adductor Canal Block Decreases Opioid Consumption Following Total Knee Arthroplasty

In the control group, older patients tended to receive less opioids. This is likely due to physiologic changes in opioid metabolism associated with aging, including decreased renal and hepatic opioid metabolism and alterations in overall body composition that increase relative potency and duration of action of opioids in a geriatric population.^25,26 No difference in opioid use by age was found for the protocol group.

Patients in the protocol group demonstrated significantly greater maximal knee extension on POD 1 compared with the control group. No difference in maximal flexion was found. This difference in extension may partially be explained by the use of an ACB. One benefit of ACB is greater quadriceps strength and fewer near-fall events when compared with FNB.^15,19

Our results corroborate the findings of similar studies. A randomized controlled trial comparing a multimodal analgesic regimen with a periarticular injection without a postoperative ACB to a hydromorphone PCA revealed a significant decrease in opioid use in the multimodal analgesic group.²⁷ Along with lower opioid requirements, the multimodal analgesic group had lower visual analog scale pain scores, fewer AEs, faster progression to physical therapy milestones, and higher satisfaction.²⁷ Recent guidelines from the French Society of Anaesthesia and Intensive Care Medicine recommend against the use of gabapentin as a method of postoperative pain control. However, this specifically refers to the preoperative administration of gabapentin. This same set of guidelines later cites a high level of evidence suggesting patients undergoing arthroplasty benefit more from gabapentinoids.²⁸ Multiple analgesic protocols that include gabapentin as a part of a multimodal approach have been shown to have positive results.^13,29

In our study, patients receiving the multimodal analgesic regimen were significantly more likely to be discharged home rather than to postacute care facilities, which have been associated with increased rates of major complications, 30-day readmission, and 30-day reoperation.^30,31 In addition, discharge to an inpatient rehabilitation or skilled nursing facility has not been found to result in higher functional outcomes, despite $3.2 billion spent yearly on rehabilitation services after primary TKA.^32,33

A component of our described analgesic protocol included spinal anesthesia intraoperatively. The differences between groups regarding anesthesia type can be attributed to this protocol change. A significantly greater percentage of patients in the protocol group received spinal anesthesia, while more patients in the control group received general anesthesia. While patients who received spinal anesthesia may have enhanced analgesia in the immediate postoperative period, no differences in opioid outcomes were seen based on anesthesia type. Known benefits of intraoperative spinal anesthesia include decreased perioperative blood loss and a smaller decrease in hemoglobin postoperatively, as well as lower rates of in-hospital complications, including pulmonary embolism, pneumonia, cerebrovascular events, and acute renal failure.³⁴

Limitations

A number of limitations of this study should be noted. One was a protocol change regarding length of stay, which occurred during the study period and resulted in a significantly shorter length of stay in the protocol group. As a result, opioid use data were analyzed only through midnight at the end of POD 1. Patients who were discharged on POD 1 did not have opioid use data available for the full duration of the first POD, which may exaggerate the decrease in opioid requirements, as opioids used after discharge but prior to midnight on POD 1 were not recorded. However, opioids taken at home are oral with a low MME compared with IV opioids received by hospitalized patients in the control group. In addition, if taken as prescribed, patients at home would only have enough time to take a few doses of opioids prior to the midnight cutoff. We do not believe this difference in time of opioid use meaningfully affected the data. An additional limitation includes the variability between periarticular injections between surgeons. While the percentage of patients that received injections from surgeon 1 vs surgeon 2 were similar, it cannot be ruled out as a potential confounding factor. Other limitations include a lack of pain scores to compare subjective pain ratings, the retrospective nature of the study, and a largely homogenous male VA population.

Conclusions

Ease of access to opioids is a risk factor for opioid abuse, which itself is a risk factor for subsequent heroin use.^1,2 The CDC and AAOS have thus published recommendations regarding opioid prescribing practices to decrease opioid use and abuse.^5,6 Our described protocol, which aligns with these recommendations, resulted in a significant decrease in IV opioid requirement, total opioid requirement, and lower rates of opioid prescriptions provided at the first postoperative visit. These promising findings demonstrate a lower percentage of patients on long-term opioids after TKA and a significantly decreased cumulative opioid exposure.