In order to continue progressing towards outpatient total hip arthroplasty (THA), methods to adequately manage postoperative pain is of paramount importance. The purpose of this study is to quantify the effectiveness of the pericapsular nerve block in total hip arthroplasty in comparison to the fascia iliaca nerve block.

This is a single center, randomized, controlled trial in adult subjects undergoing total hip arthroplasty that will receive one of two different nerve block regimens for pain management as part of standard of care.

Effective pain control after surgery for total hip replacement is a critical element in patient recovery. Particularly, in the first few days, as majority of patients may experience significant pain. Improved pain management after surgery contributes to better healing, faster patient mobility, shortened hospital stays, and reduced healthcare costs. While pain management is an important factor in total hip replacement, pain after surgery has yet to be improved. Inadequate pain control can lead to delayed movement, thereby increasing the risk for complications such as blood clots in the legs (deep venous thrombosis - blood clots in your veins) with some patients developing blood clots in their lungs (pulmonary embolus). In addition to pain medications after surgery, nerve blocks such as the femoral or fascia iliaca, have been used as supporting therapy for pain management after a total hip replacement. While these nerve blocks are used on a regular basis, they do have limitations which can produce inconsistent results for pain control and use of pain medications after surgery. With no clear superior nerve block for total hip replacement, a new nerve block, called the pericapsular nerve group (PENG) block has emerged. It has demonstrated the ability to prolong pain relief and decrease the use of pain medications after surgery. Therefore, a randomized study comparing the PENG block to other blocks established within the anesthesia community (e.g., fascia iliaca block) will allow for providers to understand the capabilities this block has in the setting of a total hip replacement.

In addition to your normal standard clinical care, there will scheduled pre-operative, operative, 2-week, and 4-6 week follow-up visits.

Inclusion Criteria:

• Provision of signed and dated informed consent form
• Stated willingness to comply with all study procedures and availability for the duration of the study
• Planned primary total hip arthroplasty with anterior (Smith-Peterson) approach
• ASA score of 1 to 3
• Indicated for one of the two nerve block groups
• Must be opioid naïve at screening as defined by the FDA - According to the Food and Drug Administration, opioid-tolerant patients were those currently receiving or who had previously received 60 mg PO morphine per day, 25 mcg transdermal fentanyl per hour, 30 mg PO oxycodone per day, 8 mg PO hydromorphone per day, 25 mg PO oxymorphone per day, 60 mg PO hydrocodone per day, or an equivalent dose of another opioid for a duration of one week or longer (16)

Exclusion Criteria:

• Current or previous diagnosis of "chronic pain"
• Opioid tolerant at time of screening (for a week or longer, at least 60 mg of morphine daily, or at least 30 mg of oral oxycodone daily, or at least 8 mg of oral hydromorphone daily or an equianalgesic dose of another opioid.)
• Diagnosis of ankylosing spondylitis
• Allergy to any potential medications utilized in any of the two groups
• Conversion of patient to general anesthesia intraoperatively
• Treatment with another investigational drug or other intervention for pain
• Any condition(s) or diagnosis, both physical or psychological, or physical exam finding in the opinion of the investigator that would precludes participation