Pain Control After Total Knee Arthroplasty: Benefit In Adding Single Shot Adductor Canal Block to Existing Pain Regimen Protocol?

The purpose of this project is to compare the effectiveness of two different but well accepted approaches to nerve blockade in order to improve pain control after total knee arthroplasty. Specifically, this study seeks to identify the if adductor canal blockade provides additional pain relief and decreased morphine consumption when used in addition to a local infiltration of anesthetic (periarticular injection).

Aims:

1. compare pain scores in the post operative period between the two groups.
2. compare morphine equivalent required in the postoperative period
3. compare patient satisfaction with pain control in the post operative period
4. compare physical exam findings such as joint range of motion in the post operative period
5. compare ability to participate with physical therapy in the post operative period

Total knee arthroplasty is associated with intense pain in the post operative period. Pain control is essential in this patient population. Beyond the ethical and humanitarian concerns, pain has been shown in the literature to affect outcomes after total knee replacement. Patients in pain tend to have worse range of motion, decreased participation with physical therapy, increased time to discharge, and downstream medical sequela as well. Pain has been shown to cause or exacerbate delirium in the postoperative period. Patients in pain ambulate less and stay in bed more, therefore increasing the risk of deep vein thrombosis and pulmonary embolism. Patients in pain consume more opioids, which have well known side effects, such as constipation, nausea, vomiting, pruritus, addiction, and altered mental status. Early joint range of motion prevents irreversible joint stiffness and pain, affecting long term outcomes. Pain control in patients undergoing total knee arthroplasty has improved in recent years. The current standard has become a multimodal approach, consisting of preoperative, intraoperative and post operative interventions. The multimodal approach works by preventing or addressing pain at multiple location and targets multiple different pain receptors and pain generators. There has been much attention given to injections and nerve blocks in addition to standard pain medications such as antiinflammatories, acetaminophen, and opioids. There have been many published studies investigating various medication regimens, periarticular injection cocktails, and post operative nerve blocks. These studies have shown that each modality works better than placebo. Several studies have shown that post operative blocks provide additional benefit when used in conjunction with a periarticular injection. These studies were done with femoral nerve catheters and adductor canal catheters that stay in place for several days post operative and require subsequent boluses. No studies in the literature have studied the additional benefit of a single shot adductor canal block. The rationale is that the injection given at the time of surgery should affect the same same local nerves and pain receptors as the adductor canal block, via a different technique. Therefore, the investigators believe the adductor canal block may prove to be of no additional benefit in the investigators patients.

The ultimate goal is identifying the best pain control protocol to decrease pain in the post operative period. Developing this protocol may require the addition or subtraction of various treatment modalities. This study is looking at the adductor canal block, which if found to be unnecessary will prevent patients from receiving unnecessary procedures. If found to be effective at reducing pain, then this study will provide direct evidence for using single shot adductor canal blockade in addition to the periarticular injection.