Peripheral Nerve Blocks in Foot and Ankle Surgery




Postoperative pain is one of the most important factors in regard to patient outcomes. It has been linked with patient satisfaction, length of stay, and overall hospital costs. Peripheral nerve blocks have provided a safe, effective method to control early postoperative pain when symptoms are most severe. Peripheral nerve blocks, whether used intraoperatively or postoperatively, provide an alternative or adjunct to conventional pain management methods for patients who may not tolerate heavy narcotics or general anesthesia, in particular the elderly and those with cardiopulmonary disease.


Key points








  • Increasing outpatient surgery rates necessitates controlling postoperative pain.



  • Regional anesthesia decreases hospital length of stay, hospital-associated costs for patients, and perioperative opioid use.



  • Postoperative pain has been shown to be factor in patient outcomes.



  • Peripheral nerve blocks are a safe alternative to traditional approaches to managing postoperative pain.



  • Safe alternative or adjunct to traditional methods for the elderly and those with cardiopulmonary disease.






Introduction


The advancement of peripheral nerve blocks in foot and ankle surgery has vastly expanded the plethora of choices for pain management in the perioperative period. Without the need for high doses of intravenous pain medication, a larger number of operative procedures can be performed on an outpatient basis, or with shorter observational single-night stays in a hospital setting. These forms of regional anesthesia lead to decreased opioid use and lower reported levels of perioperative pain. This may allow patients the option of recovering comfortably at home while incurring lower surgery-related costs. In addition, there are many patients in whom opioids may pose a risk secondary to other medical comorbidities, including those with decreased cognition, dementia, or a previous history of narcotic dependence.




Introduction


The advancement of peripheral nerve blocks in foot and ankle surgery has vastly expanded the plethora of choices for pain management in the perioperative period. Without the need for high doses of intravenous pain medication, a larger number of operative procedures can be performed on an outpatient basis, or with shorter observational single-night stays in a hospital setting. These forms of regional anesthesia lead to decreased opioid use and lower reported levels of perioperative pain. This may allow patients the option of recovering comfortably at home while incurring lower surgery-related costs. In addition, there are many patients in whom opioids may pose a risk secondary to other medical comorbidities, including those with decreased cognition, dementia, or a previous history of narcotic dependence.




Anatomy


Sensation to the foot and ankle is provided by the branches of the sciatic nerve and the femoral nerve. Particularly, the femoral nerve terminates as the saphenous nerve, providing sensation to the medial foot. The sciatic nerve divides into the tibial nerve and the common peroneal nerve. The tibial nerve provides plantar foot sensation via the medial and lateral plantar nerves. The common peroneal nerve splits into the superficial peroneal nerve, providing sensation to the dorsal foot, and the deep peroneal nerve, providing sensation to the first web space. The sural nerve is generally derived from branches of both the common peroneal and tibial nerves and provides lateral foot sensation. Targeted anesthesia to the foot and ankle can be delivered to a specific dermatomal distribution by perineural injections of local anesthetic. Alternatively, one can target the sciatic nerve proximally in the popliteal fossa to target most of the sensation to the foot. A separate injection can then be used medially to block the saphenous nerve and thereby provide anesthesia to the foot ( Fig. 1 ).




Fig. 1


Lower extremity nerves. DPN, deep peroneal nerve; SPN, superficial peroneal nerve.


Sciatic Nerve


The most commonly used proximal nerve block for foot and ankle surgery is a sciatic nerve block at the level of the popliteal fossa. Generally, the injection is located proximal to the location where the sciatic nerve divides into the tibial nerve and common peroneal nerves. A single injection of anesthetic in this location can provide anesthesia to nearly the entire foot, excluding the medial foot saphenous nerve distribution. In the popliteal fossa, the sciatic nerve lies lateral to the popliteal artery, and is bordered by the heads of the biceps femoris and gastrocnemius on the medial and lateral sides. Success with sciatic nerve blocks has been reported for a wide variety of foot and ankle procedures. Although the sciatic nerve block generally provides adequate anesthesia distally, the common use of thigh tourniquets in foot and ankle surgery may necessitate further anesthesia to avoid thigh discomfort from tourniquet compression. As an alternative, a lower-leg tourniquet around the calf can safely be used and may obviate more proximal anesthesia. Grebing and Coughlin reported the Esmark bandage provided average tourniquet pressures between 222 and 288 with 3 or 4 wraps, respectively. The complication rate of these ankle level tourniquets was .1%. Michelson and colleagues found no postoperative neurovascular deficits in 454 limbs using cast padding and a standard calf tourniquet ( Fig. 2 ).




Fig. 2


Popliteal fossa.


Saphenous Nerve


Conventionally, the saphenous nerve was thought to provide sensation to the medial leg and foot. However, there has been much debate about the true contribution to medial foot and ankle sensation, and this is highly variable. Some investigators suggest that the saphenous nerve does not extend past the midfoot, whereas others have found contributions to the first ray, talonavicular, subtalar, and medial ankle joints. These investigators recommend that a saphenous nerve block should be included as a component of the regional block to provide adequate anesthesia during the perioperative period of procedures involving the forefoot. At the level of the knee joint, the saphenous nerve can be found between the vastus medialis and sartorius myotendinous junctions. A fascial plane separates these muscles that can be used as a landmark for anesthetic injections. Addition of anesthesia to this area in combination with the sciatic block will theoretically block the entire foot. Multiple variations have been reported for the saphenous nerve block, with data to support using trans-sartorial or subsartorial approaches. As the saphenous nerve courses distally to a level approximately 3 cm proximal to the medial malleolus, it divides into anterior and posterior branches, which each further ramify in the medial foot and ankle. An accurate saphenous nerve block at the ankle level generally involves injecting just anterior and proximal to the medial malleolus ( Fig. 3 ).




Fig. 3


Saphenous nerve course at knee.


Ultrasound Versus Nerve Stimulator for Nerve Localization


Nerve blocks may be more safely performed by identifying the nerve before the injection ( Fig. 4 and Table 1 ). Ultrasound guidance has replaced nerve stimulation as the preferred technique for nerve localization for peripheral nerve blocks. A meta-analysis of 23 randomized controlled trials (RCTs) by Munirama and Mcleod showed localization via ultrasound significantly reduced patient-reported procedural pain. Findings also included a decreased amount of anesthetic used and decreased inadvertent vascular punctures with the use of ultrasound. No difference in neurologic side effects was found between the 2 groups. Cao performed a separate meta-analysis of 10 RCTs comparing ultrasound versus nerve stimulation for nerve localization and found higher success and less vascular injuries with ultrasound guidance. There were no significant differences on overall block success rate or procedure time. A more recent report by Gelfand and colleagues reviewed 16 RCTs and found ultrasound guidance was superior in overall block success compared with nerve stimulation in brachial plexus and popliteal sciatic blocks. Although the use of ultrasound is very operator-dependent, multiple studies report the use of ultrasound leads to better accuracy and clinical results when compared with nerve stimulation techniques.




Fig. 4


Distal local nerve block locations.


Table 1

Lower extremity nerves



























Distally Proximally
Sural Between Achilles and peroneal tendons; coursing with lesser saphenous vein Posterior calf between 2 heads of gastrocnemius; coursing with lesser saphenous vein
Tibial Posterior to medial malleolus, posterior to posterior tibial artery; between FDL and FHL Between FDL and FHL in mid-tibia
Deep Peroneal Nerve Between EHL and EDL, coursing with anterior tibial artery On the IOM in anterior compartment of leg
Superficial Peroneal Nerve Splits into dorsal and intermediate dorsal branches at the ankle On the surface of peroneus brevis at midfibula in lateral compartment
Saphenous Courses with saphenous vein and ramifies into anterior and posterior branches just proximal to medial malleolus. Effectively blocked slightly proximal and anterior to medial malleolus Travels distally deep to pes tendons into subcutaneous tissue with the saphenous vein; gives off infrapatellar branch

Abbreviations: EDL, extensor digitorum longus; EHL, extensor hallucis longus; FDL, flexor digitorum longue; FHL, flexor hallucis longus; IOM, interosseous membrane.


Single-shot Versus Continuous Infusion


Reducing postoperative pain can be accomplished by a single injection or a continuous infusion via an indwelling catheter nerve block. The indwelling catheter necessary for a continuous nerve block may carry a small risk of infectious colonization but provides longer term pain relief. Bingham and colleagues reviewed 21 studies and found continuous blocks provided statistically significant better pain control on the first 3 postoperative days. In addition, continuous blocks were associated with fewer opioids, less nausea, and higher patient-satisfaction scores. Ding and colleagues reported that subjects discharged with a continuous infusion nerve pump (Halyard; Irvine, CA, USA) had significantly lower pain scores and narcotic use at 2 and 12 weeks postoperatively compared with subjects who had a single-injection sciatic block after ankle fracture surgery. Another study on a subset of subjects undergoing surgical fixation of calcaneus fractures with postoperative continuous nerve blocks reported adequate pain control and postoperative day 1 discharge, with 63% lower total incurred costs. Although indwelling catheters seem to provide increased duration of pain relief, many studies show effective pain control with single-shot blocks. Grosser and colleagues looked at 25 consecutive subjects with preoperative popliteal blocks and found zero reported pain the in postanesthesia care unit. The average block duration was 14 hours and subject satisfaction at 1 week was 4.8 out of 5. Elliot and colleagues compared continuous versus single-shot blocks after hindfoot surgery and found the visual analog scale ranged from 1.1 to 3.6 in all subjects. The single-shot group did have statistically higher pain scores compared with the continuous group, but overall VAS scores were still low and likely not clinically significant. Single-shot blocks are also faster to perform and eliminate the need for a continuous pump. Ding and colleagues8 found 7 of 23 subjects in the continuous group had some degree of pump malfunction and 1 accidental catheter removal. Overall, the literature shows both options provide effective analgesia with each having its own benefits.




Postoperative care and removal


Although, in some surgical applications, peripheral nerve blocks may allow for more immediate rehabilitation, in foot and ankle surgery, nerve blocks must be used carefully because they may be associated with balance issues and falls. Many foot and ankle procedures are followed by a postoperative regimen of nonweightbearing and limb elevation to minimize soft tissue swelling and promote healing. This postoperative protocol is also beneficial when nerve blocks are used because they eliminate the need for weightbearing on the insensate foot, which minimizes the effects of an insensate foot on balance and gait ( Box 1 ).


Oct 6, 2017 | Posted by in ORTHOPEDIC | Comments Off on Peripheral Nerve Blocks in Foot and Ankle Surgery
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