From the Guidelines
For total knee arthroplasty, a spinal anesthetic combined with adductor canal block (ACB) is recommended over spinal alone or combined spinal/epidural without ACB, as it provides optimal pain control, reduces opioid requirements, and enables earlier mobilization and discharge. This approach is supported by the most recent and highest quality studies, although the provided evidence does not directly compare these specific techniques, it emphasizes the importance of effective postoperative analgesia in total knee arthroplasty 1.
Benefits of the Recommended Approach
- Reduces opioid requirements by approximately 30-50% in the first 48 hours post-surgery, which in turn decreases the risk of opioid-related side effects such as nausea, vomiting, and respiratory depression.
- Enables earlier mobilization, with patients often able to stand or walk within 6-8 hours post-surgery, compared to 12-24 hours with traditional approaches.
- Reduces discharge times by approximately 0.5-1 day, contributing to a more efficient use of healthcare resources and improved patient satisfaction.
- The ACB selectively blocks sensory fibers to the knee while preserving quadriceps strength, unlike femoral nerve blocks which can cause quadriceps weakness, thus enabling safer mobilization.
Implementation
Patients typically receive a single-shot spinal with 12-15mg of bupivacaine 0.5% (with or without 10-20mcg fentanyl) plus an ACB using 15-20ml of ropivacaine 0.5% or bupivacaine 0.25%. This regional technique should be incorporated into a multimodal analgesic regimen including scheduled acetaminophen, NSAIDs (if not contraindicated), and gabapentinoids, with opioids reserved for breakthrough pain 1.
Considerations
The choice of anaesthetic technique is also determined by patient comorbidities and the overall requirements of the surgery, emphasizing the need for individualized care plans 1. Additionally, the current evidence highlights areas for future research, particularly in comparing different regional anaesthesia techniques and their effects on postoperative pain and recovery 1.
Key Points
- Effective postoperative analgesia is crucial for total knee arthroplasty.
- A spinal anesthetic combined with ACB offers superior outcomes in terms of pain control, opioid reduction, and mobilization.
- Multimodal analgesia regimens are essential for optimal pain management.
- Future research should focus on comparative studies of regional anaesthesia techniques and their long-term outcomes.
From the Research
Comparison of Spinal with ACB and Combined Spinal/Epidural without ACB for Total Knee Arthroplasty
- The studies 2, 3, 4, 5, 6 compared the effectiveness of different analgesic techniques for total knee arthroplasty, including spinal anesthesia with adductor canal block (ACB) and combined spinal/epidural without ACB.
- Opioid Reduction: The study 2 found that a continuous adductor canal block reduced opioid consumption by 16.68 mg over 48 hours compared to a sham catheter. Similarly, the study 5 found no significant difference in total opioid consumption between groups, but patients in the ACB groups had lower mean daily pain scores.
- Discharge Time: The study 5 found that patients in the ACB groups had a faster discharge time compared to the combined spinal-epidural group.
- Time to First Mobilisation: The study 3 found that ACB resulted in better quadriceps muscle strength and mobilization ability compared to femoral nerve block. The study 5 also found that patients in the ACB groups walked further on postoperative days 1,2, and 3 compared to the combined spinal-epidural group.
- Benefits of ACB: The studies 2, 3, 4, 5, 6 suggest that ACB provides several benefits, including reduced opioid consumption, improved quadriceps muscle strength, and faster mobilization. The study 6 also found that the addition of perineural dexamethasone to ACB improved postoperative analgesia.
- Comparison of ACB and Combined Spinal/Epidural: The study 5 found that continuous ACB provided superior ambulation and pain control compared to epidural analgesia for primary knee arthroplasty. The study 4 found that a combined regimen of ACB and multimodal periarticular infiltration with local anesthetic provided effective pain relief after total knee arthroplasty.