I have worked in four different states all over the country and have spent a lot of time in various cities observing how podiatrists practice, and for the most part I’m pretty consistent with the mainstream of our profession. But the one way in which I seem to differ is my rather heavy use of the popliteal block. Despite its proven utility, the popliteal block is rarely utilized by most of our profession. For those of you who use this regional method of anesthetic blockade, what I’m going to discuss will be old hat, but for those of you who don’t, I hope to spur your interest. What does the evidence say about using popliteal blocks? Should they be used more than they currently are?

First, a little background about the popliteal (or “pop”) block. In reality, this is a regional blockade of the sciatic nerve just before it becomes the popliteal nerve in the posterior knee. This block is performed most commonly by anesthesiologists, and in my experience, their ability to perform this procedure varies by physician, with the younger ones more likely to successfully complete the block in less time. It takes on average 30 minutes for the anesthesiologist to complete the procedure, but with practice, it can be done in 15 minutes. I worked with a couple of excellent cRNAs in Oregon who were able to do the block in 15 minutes. The length of time it takes is most likely the reason it is not performed all that often, and there is no reason why podiatrists can’t do this.

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“It takes an anesthesiologist on average of 30 minutes to complete a Popliteal Block, and this is the most likely reason it is not performed that often. But with practice, it can be done consistently in 15 minutes.”

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Patients can be either supine or prone. An ultrasound is commonly used to localize the neurovascular bundle about seven cm above a line drawn proximal to the popliteal crease almost in the midline of the leg. A catheter, with attached nerve stimulator, is introduced into the appropriate area and a long-acting anesthetic is injected, most commonly ropivacaine. An additional option is to use an in-dwelling catheter, which attaches to a bulb that provides continuous anesthesia for a three-day period. I have had little success with the use of in-dwelling catheters, and the single shot method seems to work best.

An important point to remember is blocking the sciatic nerve does not anesthetize the saphenous nerve, since this is a branch from the femoral nerve. Thus, a portion of the medial side of the foot will remain sensate. Not so great for medial approaches to procedures like flatfoot reconstructions. One should request a popliteal and saphenous nerve block for full lower extremity anesthesia. Additionally, patients should be advised that they must remain non-weightbearing for 24 hours after the block and should not be surprised if they cannot move their foot or toes until the anesthetic wears off (muscle blockade occurs in addition to sensory).

My patients typically receive a minimum of 12 hours and maximum of 30 hours of complete anesthesia with this technique. What has been particularly gratifying is, despite the limited initial anesthesia, these patients have a clear decrease in overall postoperative pain during their entire recovery, much better than local anesthesia about the foot or ankle. This is the true reason why I spend the time to have this block performed preoperatively. For those who are interested in more detail, Donohue and colleagues wrote an informative review of this nerve block¹.

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“My patients typically receive a minimum of 12 hours and maximum of 30 hours of complete anesthesia with this technique, as well as a clear overall decrease in postoperative pain during their entire recovery”

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How does the popliteal block stack up to our common methods? First, I suggest giving patients any nerve block before the incision rather than after. Yes, it’s less convenient, but there are real physiological reasons to do pre-incisional anesthesia – and we’ll get to that in next week’s issue!

The Evidence

In 2005, Migues and colleagues performed a prospective randomized study of 51 patients undergoing forefoot surgery². Patients were randomly allotted to either a local foot anesthesia (26 patients receiving combined tibial and common peroneal nerve block) or popliteal nerve block (25 patients). The saphenous nerve was also blocked in those cases using a tourniquet. The majority of patients were female with an average age between 56 and 61 years, with average tourniquet and surgical times just under an hour. The authors were attempting to determine superiority of one technique over the other by looking at three primary outcomes: quality of anesthesia (if the studied block was the only method necessary), post-op analgesia, and incidence of complications.

They found each method to be the sole method of blockade in 24 of 26 patients in the foot block group and 24 of 25 patients in the popliteal group. It took an average of 14.3 minutes to complete the block for the foot group and 19.2 minutes in the popliteal group. The average latency of the blocks (time to anesthesia onset) was 8.6 minutes for the foot group and 10.48 minutes for the popliteal group. Both groups had equal average patient satisfaction of about 96%. Post-op visual analogue scales at 6, 12, 18, and 24 hours was statistically insignificant with average anesthesia time of 10.96 hours in the foot group and 14.32 hours in the popliteal group. There were no complications from either of the block methods. The researchers concluded both procedures were equally safe and efficacious.

I have one major problem with this study’s methodology that affects the generalizability of the results. The researchers performed the tibial and common peroneal nerve block in a way that deviates from general practice, and they did not compare to any other types of blocks such as Mayo, ray, digital, or ankle blocks (all of which are more commonly used in foot and ankle surgery). Additionally, they used a nerve stimulator to perform the tibial/common peroneal block, which is almost never done in common practice.

Elkassabany, Cai, Mehta, et al, performed a prospective cohort study of 93 patients undergoing popliteal and saphenous nerve blocks for operative repair of tibia and ankle fractures³. The method of regional anesthesia was not discussed in detail other than to relate that it was performed post-operatively. Fifty-nine patients underwent regional block while 34 did not. Patient scores showed greater satisfaction with the regional block (average 9/10) versus general anesthesia (average 7/10). Patients without the popliteal/saphenous block experienced longer periods of severe pain, significantly higher pain levels, and increased use of PCA (patient controlled analgesia) pumps at 24 and 48 hours.

The major issue with this study was use of the regional block postoperatively, which does affect postoperative pain levels. However, despite this, the results are encouraging.

I should note at this point that there is a lot of research that has been done on the popliteal/saphenous block, including the use of continuous anesthesia with in-dwelling catheters, amounts of anesthetic volume to be injected, complications, and augmentation with adjuvant medications such as dexamethasone. These are beyond the scope of this discussion, but I suggest taking the time to familiarize yourself with other studies if you haven’t tried this anesthetic method. The research topics I have not been able to find is whether or not the popliteal/saphenous regional block affects longer-term pain (48 hours to 8 weeks) after foot and ankle surgery and how it compares with typical podiatric nerve blocks. From my personal experience, this regional block decreases overall pain in many patients during the entire postoperative recovery period.

To wrap up this discussion, here are some suggestions for those who haven’t used the popliteal block yet:

The popliteal block is a highly effective anesthetic choice and should definitely be used by more foot and ankle surgeons. If you’re not currently using it consider giving it a try.