A 62-year-old woman with end-stage tricompartmental knee osteoarthritis presented for right total knee arthroplasty (TKA). She had a history of alcohol use disorder, with 4 years of sustained sobriety. She was also obese and had gout. She expressed a strong desire to avoid opioid analgesics post-operatively due to a concern for relapse into substance misuse.
In order to accommodate this wish while also providing adequate analgesia, we implemented spinal anesthesia and a strategy of multimodal analgesia, including peripheral nerve blocks to provide analgesia for both the front and back of the knee. The nerve blocks included an adductor canal block in combination with an infiltration of local anesthetic between the popliteal artery and capsule of the knee (IPACK) block, which together have been shown to reduce opioid use and enhance physical therapy performance after TKA .
Spinal anesthesia was performed using 1.5% mepivacaine 4 mL, along with moderate sedation with midazolam and propofol infusion titrated for effect. The IPACK and adductor canal blocks were performed under ultrasound guidance.
For the IPACK, a mixture of 0.25% bupivacaine 30 mL and preservative-free dexamethasone 3 mg was injected along the posterior aspect of the distal femur in order to block the sensory innervation provided by the medial and lateral genicular nerves.
The adductor canal block was achieved by initially injecting 0.5% bupivacaine 20 mL into the adductor canal, with assurance of good perivascular spread around the superficial femoral artery. The adductor canal catheter was then placed through the same needle (Fig. 1), and location was confirmed under ultrasound guidance with injection of 1–2 mL of air.
Figure 1: Placement of an adductor canal catheter along the medial aspect of the mid-thigh, with sterile occlusive dressing (Tegaderm™).
The TKA was completed uneventfully, and the adductor canal infusion catheter was left in place for 48 hours. The patient’s postoperative pain regimen included adductor canal catheter infusion of 0.2% ropivacaine at 8 mL per hour; acetaminophen 1000 mg IV every 6 hours for 24 hours, followed by 500 mg PO every 6 hours; and tramadol 50 mg as needed.
The patient ambulated on the day of surgery and advanced well with physical therapy, achieving good pain control with acetaminophen 500 mg every 6 hours. On postoperative day 1, the patient rated her pain on average 4/10 and elected not to take tramadol. The next day, she rated her pain 3/10 after taking a single dose of tramadol 50 mg. Her adductor canal catheter was removed on post-operative day 2, and she had a smooth transition to her oral pain regimen. She was discharged home on postoperative day 3 with prescriptions for acetaminophen and tramadol as needed.
At the patient’s 6-week follow-up appointment, she had 0–100° range of knee motion and could walk up to one-fourth mile at a time; she was very pleased with acetaminophen as her sole analgesic and did not require tramadol at home. At her 3-month follow up, she continued to progress well, with range of motion now up to 105°, taking only acetaminophen as needed. Considering her satisfactory postoperative progress, the surgeon prescribed continued physical therapy and a routine follow-up evaluation at 12 months after surgery.
Long-term rates of relapse after remission from alcohol use disorders are estimated to be between 22 to 86%, depending on individual risk factors . Increased stress response in the perioperative period can be devastating in elevating that risk [1, 7]. While the degree of this effect has not been determined, adequate analgesia may reduce the stress response to surgery and mitigate the risk of relapse.
Those with prior history of alcohol use disorders are at an elevated risk of developing other substance use disorders . This risk is likely multifactorial, with neurochemical, psychiatric, and genetic components . Minimizing exposure to addictive medications perioperatively via a multimodal pain-management approach of regional anesthesia and nonopioid analgesics may be beneficial in reducing the risk of substance use disorders after surgery.
However, extending regional anesthetics for prolonged postoperative pain control, when patients likely require opioid analgesia, can be difficult. Our use of a combined adductor canal and IPACK block using dexamethasone is one of many techniques for extending analgesia after TKA . Compared to traditional epidural-based analgesics, a postoperative peripheral nerve catheter infusion, such as the adductor canal block used in this case, may provide prolonged postoperative pain control.
An adductor canal block, when the catheter is properly inserted, blocks the saphenous nerve, distal branches of nerves to vastus medialis, and potentially branches of the obturator nerve . It is less likely than a femoral nerve block to cause motor blockade of the quadriceps and thus facilitates early mobilization and physical therapy, especially when combined with an IPACK block, which blocks the sciatic contribution to knee sensation without causing hamstring weakness or foot drop [9, 10]. Much work has been done on different techniques involving various blocks, catheters, adjuvants, and extended-release formulations of local anesthetics; however, the optimal regimen for analgesia after TKA has yet to be agreed upon . The current practice is largely institution dependent.