Midcalf Continuous Peripheral Nerve Block Anesthesia for Hallux Valgus Surgery

Case Description

A 44-year-old female physician presented for right hallux valgus correction. The patient was scheduled for right modified McBride procedure and right scarf osteotomy. Patient’s medical history was significant only for factor 5—Leiden coagulopathy and aspirin allergy. The patient requested a long-acting analgesia technique, but the restriction of ankle range of motion associated with a cast or cam walker immobilization was a relative contraindication secondary to deep vein thrombosis (DVT) risk associated with factor 5 Leiden coagulopathy. The anesthetic management was planned for propofol sedation along with SPDPT continuous peripheral nerve blocks.

With the patient in supine position, a PLT 1204BT 7-14 MHz probe on Aplio MX 500 (Toshiba America Medical Systems, Inc, Tustin, CA) ultrasound machine was used to trace all 3 nerves from the ankle to the midcalf (Figures 1, 2, and 3). The skin point of puncture was infiltrated with 1 ml of 2% lidocaine. With real-time ultrasound guidance, a 20 Ga. Tuohy needle (Perifix, B. Braun Medical Inc, Bethlehem, PA) was advanced in the proximity of each of the nerves. Once the structures were identified, 5 ml of 0.5% Bupivacaine was injected in close proximity to each nerve. After the injection, 24 gauge pediatric epidural catheters (Perifix One, B. Braun Medical Inc, Bethlehem, PA) were advanced 3 cm past the needle tip in close proximity to the nerves. The patient did not receive any sedatives during the placement of the 3 nerve blocks and tolerated the procedure well. Careful attention was made to allow for adequate exposure of the leg in sterile surgical preparation, as well as use of a sterile ankle tourniquet.

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Figure 1.

Illustration of axial section through the midcalf. 1, transducer position for Figure 2; 2, transducer position for Figure 3; AT, tibialis anterior muscle; ATA, tibialis anterior artery; DPN, peroneus profundus nerve; EDL, extensor digitorum longus; FDL, flexor digitorum longus; Fib, fibula; GCL, gastrocnemius muscle—lateral head; GCM, gastrocnemius muscle—medial head; PB, peroneus brevis muscle; PL, peroneus longus muscle; PT, tibialis posterior muscle; PTA, tibialis posterior artery; Sol, soleus muscle; SPN, peroneus superficialis nerve; Tib, tibia; TN, tibialis nerve.

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Figure 2.

Axial ultrasound image of the lateral midcalf. A, anterior; FDL, flexor digitorum longus; GCM, gastrocnemius muscle—medial head; L, lateral; M, medial; P, posterior; PTA, tibialis posterior artery; Tib, tibia; TN, tibialis nerve.

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Figure 3.

Axial ultrasound image of the medial midcalf. A, anterior; AT, tibialis anterior muscle; ATA, tibialis anterior artery; DPN, peroneus profundus nerve; Fib, fibula; L, lateral; M, medial; P, posterior; PB, peroneus brevis muscle; SPN, peroneus superficialis nerve; Tib, tibia.

After the blocks were in place, the patient was taken to the operating room. The patient received propofol to maintain sedation throughout the entire 1.5 hour procedure along with a single dose of 25 micrograms of fentanyl when the propofol infusion was started. A medial incision was used for medial eminence resection and scarf osteotomy, and a dorsal incision was used for adductor tendon release and modified McBride procedure. The patient was placed in a postoperative dressing, hard shoe, and was non-weight-bearing, as per the protocol of the operative surgeon.

All 3 catheters were then attached to a single On-Q elastomeric pump (Triple-Site, I-flow LLC, Lake Forest, CA) supplying 0.2% Ropivacaine at 2 ml/hr to each catheter. The patient was discharged home after an hour of recovery in the postanesthesia care unit and followed for the next 3 days of her recovery. Wong–Baker VAS analog scale scores and narcotic diary were obtained via phone interview. VAS score was 0 over the first 3 postoperative days and the patient did not require any further narcotic pain medications or NSAIDs while the peripheral nerve block catheters were in place. The patient did not have any motor weakness of the operative extremity and was able to perform unrestricted dorsiflexion and plantarflexion of the ankle. The patient did not experience any falls, difficulty with ambulation during the postoperative period, or DVT.

Discussion

The popliteal nerve block has proven to be a valuable tool for a multimodal postoperative pain control for patients undergoing foot and ankle surgery.^2-5,6,8 To avoid the foot drop, which is 1 of the major side effects of the popliteal nerve block, we approached the tibial nerve at midcalf to preserve the motor branches supplying the gastrocnemius muscle and allowing for extension of the ankle. Approaching the deep peroneal nerve at midcalf preserved the motor branches supplying the tibialis anterior, extensor digitorum longus and extensor hallucis longus muscles that provide dorsiflexion of the ankle. Finally, approaching the superficial peroneal nerve at midcalf spared the peroneus longus and peroneus brevis muscles, allowing for foot eversion. Use of this selective technique provided adequate anesthesia and analgesia without major functional impairment. The concept of selective blockade may offer more physiologic postoperative recovery with particular effect on early physical therapy.

Similar effects can be achieved with an ankle block^1,7 that also accesses the nerves distal to the motor branch takeoffs; however, placing catheters at this level will raise concerns about the sterility of the operative field as the catheters will have to be prepped into it. Placement of the SPDPT catheters at midcalf also allows for ankle tourniquet placement below the block entry points.

Use of 20 Ga needle and 24 Ga catheters was important for these blocks since the nerve diameter at the midcalf is comparable to the 20 Ga needle. Needles of 17 and 18 Ga, ubiquitous in many continuous nerve block sets, would have more than twice the diameter of the nerves and may have been more difficult to control. Further controlled studies are under way to compare the effectiveness and safety of the midcalf block of the SPDPT nerves versus the standard sciatic nerve block at the popliteal fossa.

Summary

We describe a novel technique of continuous SPDPT blocks performed at the midcalf level for operative treatment of hallux valgus. This technique allowed for retention of protective motor function and avoidance of ankle immobilization, while providing excellent continuous pain relief and patient satisfaction. The technique was well tolerated and had minimal additional cost compared to standard continuous analgesia techniques.