Pain Control After Total Knee Arthroplasty: Is There Benefit In Adding Single Shot Adductor Canal Block to Existing Multimodal Pain Regimen and Periarticular Injection 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.

Inclusion Criteria:

- Patients over the age of 18 scheduled for primary total knee arthroplasty by four
fellowship trained surgeons will be eligible for inclusion.

Exclusion Criteria:

- Patients will be excluded if their medical history presents chronic opioid use
(greater than 3 month use),

- pregnancy,

- history of intolerance to medications in the study, and substantial substance abuse.