Total knee arthroplasty is one of the most common surgical procedures performed in the United States today. Early ambulation, which can only be achieved with adequate post-operative analgesia, is a crucial end-point that contributes to improved functional outcomes and decreases the risk of major post-operative complications. At present, a clear superior mode of pain control does not exist.

 

This retrospective study demonstrates that ITM provides effective analgesia after primary TKA under spinal anesthesia. Despite the known risks of ITM, especially in elderly adults, our study demonstrated no increased risk of PONV, pruritus, respiratory depression and urinary retention with use of 150 mcg of ITM with spinal anesthesia. For our primary efficacy outcome, we found evidence that ITM provided both clinically important and statistically significant analgesia in PACU and at 6 -12 hours when compared to control. We used oral morphine equivalent (OME) as more objective measure for analgesia efficacy. The effect was consistent with lower pain scores in ITM group at earlier time-points. We demonstrated that post operative analgesia was better controlled in the immediate post operative period in the ITM group compared with the control group. The superior analgesia provided by ITM questions the utility of continuous adductor canal block compared to single shot block. There are two major limitations to this study, however, which include the small sample size (n=25) and that this study does not investigate iPACK block plus adductor canal as a comparator group. Future investigation comparing adductor canal block ITM vs iPACK would be beneficial. At our institute, most of our primary TKA patients are discharged the day after surgery and early ambulation is encouraged for better outcomes. The ITM group showed increased ambulation distance when compared to the control group. This may be attributed to better pain control in ITM group with less opioid consumption in first 24 hours