Continuous Adductor Canal Block (CACB) vs. Combined Spinal Epidural (CSE) in Total Knee Arthroplasty

Purpose: Compare continuous adductor canal block (CACB) to Combined Spinal Epidural (CSE) for total knee arthroplasty in terms of mobility, post-operative pain, and analgesic use.

Hypothesis: CACB will provide better mobility than CSE post operatively.

Background/Scientific Review:

Total knee arthroplasty (TKA) is associated with varying degrees of pain post operatively ranging from mild to severe despite the use of comprehensive multimodal analgesic regimens1. Optimizing pain relief is vital for functional recovery after total knee arthroplasty2. Peripheral nerve blocks have been commonly used to improve pain relief and reduce opioid requirements. The addition of nerve blocks involving the femoral nerve have been shown to provide superior pain control3 and shortened hospital stay compared to epidural or intravenous patient controlled analgesia alone1. However, femoral nerve blocks can result in quadriceps weakness leading to functional impairment and an increased risk of falling post operatively4. Unlike Femoral Nerve Blocks (FNB), adductor canal blocks (ACB) are predominantly sensory blocks which preserve quadriceps muscle strength and ambulation ability better than FNBs, while providing equivalent pain relief5-9.

Recent randomized studies have also shown ACB to be superior to placebo in the setting of spinal and general intraoperative anesthesia in terms of ambulation, pain control, and opioid consumption10-12. In a recent retrospective cohort study, the addition of ACB to local infiltration analgesia (LIA) was associated with further improvement in early ambulation benchmarks and a higher rate of home discharge compared with only LIA9. While CACB and CSE are used as part of routine care at Rush University Medical Center and around the country, there have been no studies directly comparing CACB to CSE.

Study Design: Department funded, single center, prospective, randomized, parallel outcome based clinical trial. 300 subjects scheduled to undergo primary unilateral TKA will be randomized to receive CSE, CACB + General, or CACB + Spinal as per routine care. Subjects will be enrolled for no more than 6 weeks.

Power Analysis: Sample size calculations were based on the primary aim, of CACB plus Spinal anesthesia versus standard care (combined spinal epidural, CSE) improving ambulation distance at postoperative day 1 (POD1). Based on results from a pilot study we found that the CSE group had at POD1 a mean distance traveled of 159 feet with a standard deviation (SD) of 111 feet, while the CACB + Spinal anesthesia subjects walked over twice the distance on average with a similar SD.

To be conservative we expect both the CACB + Spinal anesthesia and CACB + General Anesthesia groups to walk at least 35% farther on average, or at least equal to CSE group.

Based on a one-way, 3-level AVOVA with the primary contrast of CABC + Spinal versus CSE at a 35% greater ambulation difference, for 90% power, with α of 5%, requires a sample size of 84 subjects per group. Increasing the sample size to 100 will provide for a 16% dropout rate. Total of 300 patients.

Treatment Groups:

1. General Intraoperative Anesthesia with standard post-operative Continuous Adductor Canal Block (0.2% ropivacaine running at 6-8mL/hr) with standard post-operative analgesics.
2. Spinal Intraoperative Anesthesia with standard post-operative Continuous Adductor Canal Block (0.2% ropivacaine running at 6-8mL/hr) with standard post-operative analgesics.
3. Spinal Intraoperative Anesthesia with standard Epidural (0.1% bupivacaine with fentanyl 5 mcg/mL running at 6mL/hr with 1mL q15 bolus) with standard post-operative analgesics.

Demographics/Patient Specifics: Age, Sex, ASA score, Weight, Height, Operative Time, BMI, Walker, Cane, Unassisted Ambulation

Risks/Benefits:

Combined spinal epidural anesthesia, general anesthesia, and continuous adductor canal blocks are part of routine anesthesia care at Rush University Medical Center and around the country. Post-operative analgesia regiments are standard of care.

Risks of general anesthesia include sore throat, nausea/vomiting, potential tooth damage, vocal cord injury, mental confusion, awareness, stroke, death. Risks of regional anesthesia (spinal) include bleeding (spinal hematoma), infection (meningitis), nerve damage, headache, hypotension, difficulty urinating, and seizures. There is no difference between epidural catheter and adductor canal catheter in terms of risks, other than the adductor canal catheter carries no risk of headache. These risks are present regardless of the study since either general or spinal anesthesia is used in all total knee arthroplasty procedures.

The only risk involved in participating in the study is the potential for breach of confidentiality and/or privacy. Below is a description of the procedure for maintaining confidentiality. There is no direct benefit to the participants in this study.

Procedures for Maintaining Confidentiality A breach of confidentiality and/or privacy is a risk of this study. To prevent this, all collected data will be stored electronically in password-protected files to protect patient identity and information. All information will be collected and reviewed by the research team only. Data will be maintained on a password-protected computer that will be accessible only to the study team. No patient identifiers will be maintained in the database.