The Popliteal Fossa Nerve Block: An Underutilized Regional
Technique for Foot and Ankle Surgery
Jefferson Medical College
Originally described by Labat in 1923, the PFNB technique has many desirable characteristics that make it highly suitable for a majority of foot and ankle procedures. The PFNB can serve as the sole anesthetic technique for the surgical procedure and thus avoid the use of other anesthetic techniques and their associated side effects and complications. For example, general anesthesia is often associated with a higher incidence of postoperative nausea/ vomiting and pain. This association warrants concern because these are common reasons for delayed discharge. In addition, since the PFNB does not interfere with whole body physiology, it can be utilized in high-risk patients that might not be ideal candidates for general anesthesia based on their medical co-morbidities.
Furthermore, the PFNB provides excellent surgical operating conditions and allows for rapid recovery in the recovery room. The PFNB anesthetizes the area below the knee and thus a pneumatic calf tourniquet can be utilized. Due to this, operations can be performed in a dry surgical field in anatomic regions at or above or below the ankle. Unlike neuraxial anesthesia (epidural and spinal anesthesia), patients can practice crutch training prior to being discharged because of the preservation of ipsilateral hamstring and contralateral leg strength and thus be discharged earlier.
The PFNB is a safe anesthetic technique when performed under the guidance of a peripheral nerve stimulator (PNS). The safety of the block when performed with the use of a PNS has been demonstrated in two large studies. Of note, patients tolerate the placement of the block extremely well, and experience only a minimal amount of discomfort.
One of the main advantages of the PFNB, is that it blocks afferent sensory impulses from reaching the central nervous system and thus it acts as an extremely effective form of postoperative analgesia. This regional anesthesia technique can have duration of action from 8 to 20 hrs depending on the local anesthetic agents utilized. When a continuous catheter technique is employed, the duration of action can be extended with infusion. In previous research comparing the PFNB to subcutaneous infiltration for postoperative analgesia following foot surgery, the block's duration of action was three times longer. Because of this superior pain control, patients have decreased requirements for systemic opioids in the postoperative period, and thus avoid associated side effects.
In conclusion the PFNB is an safe and efficacious technique for foot and ankle surgery, especially in the ambulatory setting. In addition the level of patient satisfaction and postoperative pain control offered by the technique is excellent. With the growing trend toward outpatient surgery, an anesthetic technique must provide rapid awakening and recovery in the PACU and effective postoperative pain control. The PFNB meets both of these requirements.
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