• LecturehallLower Extremity Peripheral Nerve Pain - Diagnostic Overview
  • Lecture Transcript
  • TAPE STARTS – [00:00]

    Male Speaker: Lower Extremity Peripheral Nerves. Craig Thomajan is here from San Antonio or from Austin, Texas rather. He’s the managing partner of Austin Foot and Ankle Specialists. He is board-certified by the American Board of Podiatric Surgery in Forefoot and Rearfoot, as well as by the American Board of Podiatric Medicine. He’s a Fellow of the Association of Extremity Nerve Surgeons, nationally recognized speaker on these topics and on microsurgical reconstruction of nerves and lower extremity in the Podiatric Practice Management. He’s held board positions on the American Board of Podiatric Medicine, Texas Podiatric Medical Association, and the Association of Extremity Nerve Surgeons.

    We are extremely fortunate to have him here. Thank you.

    Craig Thomajan: How strange to have this lecture right after how not to get to, right? So let’s teach you how to really get to it in a proper way. No, that’s a joke. Please don’t ever do that.

    Okay. Disclosures. I speak for industry, that means that AxoGen is here. They should be here outside, but they’re not. So I apologize for that. But they are responsible for me to be here. Also, I do research for them. We have two clinical trials that are going on right now and I can talk offline for that. And thank you for having me.

    So let’s talk about this overview. So what are we going to learn, really, from this? Let’s highlight the diagnosis and management of conditions that can cause persistent and chronic or severe pain that are amenable to surgical treatment. This is different than just tarsal tunnel and interdigital neuroma. We’re going to some of the really elegant things that we’re doing. But I want you guys to understand the diagnostics are the most important piece to find these patients in your practice.


    We’ll do clinical nerve assessments. We’ll give you some practice management protocols, and then we’ll pre-optimize these patients for surgery in the pre-operative and perioperative management of these same patients.

    So before we can enjoy these fulfilling and often elegant procedures, we have to identify these patients in our clinics, in our office, in some of these examples that I’m going to show you, for instance, here, is the primary tarsal tunnel. On the picture on the right is the primary tarsal tunnel within neuroma-in-continuity, these are intermetatarsal – intermetatarsal neuroma, perineural fibroma.

    Secondary and tertiary procedures from traction neurectomies. So here’s some neuroma on the inferior portion of the foot. So if you’re still practicing traction neurectomy or you’re residents, or fellows or senior attendings, doing these procedures, please, talk to me after the lecture. Let’s not do this anymore. These are often really debilitating patients.

    Revision of tarsal tunnels, and I’m talking about second and third tarsal tunnel procedures. These are revisions above, through, and below the tarsal tunnel. You can see how much scar tissue happens on the picture on the right after just an initial tarsal tunnel release.

    And then, we get into just more delicate procedures. Proximal tibial nerve decompression, Soleal sling, orthostatic nerve decompressions, insertions of peripheral nerve stimulator, external neurolysis, and neuroplasty, from the knee all the way down to the distal end of the toe.

    Here’s traumatized. Sural neuromas. We can do nerve relocations with nerve allograft. We can call it “nerve to nowhere” or translocation with cadaveric allograft nerve that we can graft to the native nerve and run the length up to 7 centimeters. These are neuroma insidious and we can eliminate sensory and touch allodynia with this repaired nerve allograft with the nerve relocation.


    Post-traumatic neuromas and perineural tumors. So here’s a tumor that you can see in the tarsal tunnel. This is ultra-micro to do a fascicular graft resection after that tumor comes out.

    So how do we find these patients in our practice? Consider that about 20% of patients develop chronic pain after any surgery, that’s any surgery from toes to nose and that the sources of these pains can fall into three categories and that can be nerve compression or nerve tethering, injury, or musculoskeletal injury, and inflammation.

    When questioning the source of pain, let’s rule out the conditions that we find on this slide and understand if your patient’s pain is from a physiological response, a noxious stimulus, or truly from a painful neuroma. We all know that feet are very complex. There’s overlapping pain sources and these require patience and a lot of times, we refer them out.

    So we’ve been talking on the last few slides about three categories of pain. These present in patients. But we have to remember trauma, any trauma or surgical trauma especially, a painful neuroma may affect up to 2% to 60% of our patients that are coming back in with a complaint of nerve injury. So we’ll review the adjectives of our patient’s descriptions, the symptoms, and consider this. If symptoms progress more gradually, that may indicate that there’s a nerve compression. And/or consider that if it’s a musculoskeletal pathology, that is usually much less painful than a nerve and that nerve and/or that nerve has undergone a grade IV or higher nerve compression. So residents in the room, that’s probably OTT and OTC test question. We’ll do that in the rumble later, right, who developed that grading system.


    So the importance of diagnostics. To identify and stop that source of nociceptive activation, the pain generator in the lower extremity that’s recognizing and modulating that perception of pain signal within our central nervous system, but will also play an important role in the patients’ experience and a critical role in the management of these patients throughout their lives.

    So once a patient is referred to a specific discipline and not just ours, there’s always a biased within that discipline to look at the patient from that specialist’s perspective. And at times, these patients may be placed in a silo and labelled and this is a common occurrence in our practice when we have those patients that we label as a chronic pain patient. But really, the role of the surgeon in the pain team is to identify peripheral nociceptive and neuropathic sources of pain in the foot, the ankle, the leg, and to eliminate or minimize them. So that said, it’s your expertise in the diagnosis and formulation of treatment plans regarding lower extremity peripheral nerve pathology which is essential.

    So plantar neural anatomy. I mean, we all remember all of this and we should be constantly studying this when we’re looking through skin and trying to determine pathologies. We have to remember – I’m looking for a pointer. Here it is. Right?

    So we can have nerve compression anywhere along the medial to the lateral perspective of the foot, right? We know all these eponyms. Joplin’s, Hauser, Hooter’s, Morton’s, Iselin’s. These are all the eponyms that were described for all of these intermetatarsal space neuromas.

    But we also have to consider that we need to talk bilingually here because of our audience. Are we talking to a podiatry? Are we talking to physical medicine? Are we talking to orthopedic surgeons?


    So when we’re thinking about dermatomes, we also have to be thinking about peripheral nerve innervation.

    Here’s another example of that from the groin all the way down to the distal end of the toe.

    So as a point of clarity, a compression of a nerve can occur at any point along its trajectory from the spinal cord or the dorsal root ganglion down into the foot, ankle, leg, and toes. And that said, there are more than 25 known orthostatic nerve compression tunnels distal to the dorsal root ganglion in the spine. And anywhere along that course from the central nervous system to the distal and the peripheral nervous system, that nerve can become compressed.

    Here’s an example, I mean we live right in this space, right, from the knee down. So all of these are potential orthostatic nerve tunnel compressions and this is where we live. And mostly we see intermetatarsal nerve, we see tarsal tunnel, even common dorsal on the top – come fibular at the top of the foot. Those are always important ones to recognize.

    So our targeted lower extremity neurological exam is going to consist of three components and we’ll first begin with our motor exam.

    So starting at the pelvis, we’re going to work distally and this will allow us to identify any specific nerve roots, lesions, lesion levels and compressions. So we’ll review this very quick but very important upper leg examination first and we’ll start at the iliopsoas, those innovations from T12 to L3. Followed by hip abduction and this is damage to discover any sort of compression or etiology in the lateral femoral cutaneous nerve known as Meralgia Paresthetica. If you have anybody in your practice that’s – you’re seeing that’s a policeman or a construction worker that wears a belt, someone who’s very heavy through their truncal space and leans over a belt, this nerve will become paralyzed and often give a distal sensory finding in the interior femoral cutaneous nerve in the distal thigh.


    You may see these commonly in those patients but always remember that this can happen from trauma too. I’ve seen this in a 12-year-old that slid in the second base.

    Hip abduction may pick up additional etiologies of thigh pains, so think about quadricep tear, think – have a – had a total knee replacement, these are subtle femoral fracture. And these are going to often show damage in the anterior and lateral femoral cutaneous nerves.

    And finally, hip expansion and that’s the inferior gluteal nerve. And that’ll help with – and these are all done statically. You can see in these pictures the patient sitting at the very end of the podiatry chair, their feet are just off the ground, we’re sitting at the stool.

    So if we couple this one minute exam with your history and this physical finding, you may actually pick up a lower back condition which will require further evaluation and advanced imaging and we can say we need a lumbar or sacral MRI or an EMG or send them out to the neurologist or the podiatrist.

    So moving on into the motor exam, the distal one-third of the leg, a memory peg to consider here is that, if there is no weakness during the hip exam but there is a presenting weakness in the foot, I want you all to think about and focus on the common fibular nerve. This controls the superficial and deep fibular nerves and the anterior and lateral musculature of the leg.

    Next we evaluate the extent of hallucis longus and we compare these both at the same time. And if there’s a weakness present that – this may indicate that there’s a common fibular nerve entrapment at the level of the knee.

    Another memory peg here, that L5, right high five with the toes have them up and out. That’ll help remember that dermatomal distribution.


    And then if the patient is complaining of a foot pain, a sprain, a fracture, maybe even a chronic arthritis, consider a nerve involvement in the intermetatarsal nerve, the posterior tibial, the softness, the deep, the intermediate dorsal cutaneous, visceral medial plantar and lateral plantar.

    However, in this, especially here, a nerve root L5 to S2, if there is a decrease in the perineal reaction time and there’s an instability, consider that this may be coming from the S1 nerve root. And that leads to the superficial fibular nerve in the lateral aspect of the fibularis longus.

    And then lastly, we’ll consider a nerve entrapment between the gastroc and the soleus muscle and the fibro osseous tunnel called the Soleal sling, that compresses the proximal tibial nerve. You’ll also want to assess this in patients who come with tarsal tunnel because the compression site might be much more proximal and not distal.

    So reviewing our deep tendon reflexes and DTRs, remember that this is a monosynaptic reflex. It’s one somatic afferent. It’s one motor efferent and it crosses the single synapse. So we don’t need a reflex and it doesn’t need to be a compression. It will just give us the difference between upper and lower.

    Another memory peg for the patella is that it’s L4, quadriceps have four muscles. The old square hammers used to look like – triangles that looked like the number four. I prefer this, it’s a Queen Square hammer. It was developed at the National Hospital for Neurology and Neurosurgery in Queen Square in London. It works really well because it acts as a pendulum, you can really get a very robust deep tendon reflex with that.

    And then another memory peg here, Achilles’ weak spot, right? His Achilles tendon has one. So – and here’s a review of all of our extremity responses and where they correspond to that lumbar designation in the in the lower extremity.

    And then paresis, we talked briefly about that on one of the earlier sessions, any condition or muscular weakness caused by nerve damage, we can pick that up with a positive Babinski as well.


    So concluding our motor exam, let’s continue with a sensory exam and we’ll see if the areas of discomfort for last has not to confound patients and bias our findings. And it will consist of a visual examination, two-point discrimination, palpation and percussion.

    So muscle power, strength testing, provocative maneuvers are important and you must compare them bilaterally. Skin is our predominantly primary indicator of sensory neurological pathology. And we need to record all of these bilaterally and the comparisons that correspond to the same geographic locations.

    Touch allodynia is really a big one especially for our chronic pain patients and our CRPS patients. All of these exams are going to be done by the way, with the patient’s eyes closed. Wartenberg wheel, this little pin wheel if you guys want to play a trick on your residency directors, put this into their Google search without them knowing and then just watch. You’ll figure it out later. Yeah. Don’t do it on your private computer especially if you’re married. That’s a hint. Okay.

    So sensory examination with the Wartenberg wheel, consider using the non-effective limb as to control and we’ll evaluate specific dermatomes, peripheral nerves and we’ll record that sharp and dull discrimination between the two and we’ll appreciate the sensory’s appreciations between that as well.

    We’ll do a two-point discrimination, each of these wheels has a designated size and millimeters. You can see them here. Right, that’s a five, there’s a four, there’s a six. A moving two-point discrimination measures, the innovation density similar to what we do with vibratory, and then a static two-point discrimination measures the innovation density similar to what we do with the Semmes-Weinstein.

    And this is important, it came out of the hand world, but when we’re talking about limb function requiring constant touch and grip and you’re communicating to other specialties, two-point discrimination is really in there wheel house.


    They understand that if you’re – if you have a denervation because of a two-point discrimination, this is really good for workers comp, this is really good for ordering other examinations, third-party examinations and getting them approved.

    We’ll compare the upper and lower extremity. I used the index finger and the thumb on the hand and I compared it with the hallux in the dorsal foot. So a sensory examination is concluded with percussion and provocation at known areas of that neural entrapment. We know where those orthostatic tunnels are from the fibular, as longest muscle at the common fibular, all away down even into the distal ends of the DIPJ’s of the joint. So it’s performed by lightly tapping or percussing over that nerve to elicit a sensation that patients are going to describe as pins and needles, they’ll feel a little electricity traveling down. And this was named for a French neurologist in the 1950s, Jules Tinel. I’m helping you guys in the back for your test tonight.

    So let’s start here at the common fibular nerve. The landmark is going to be right around the fibular neck. There is a fascial band of the fibular as long as where the common fibular nerve penetrates and bifurcates into the deep and superficial nerve. This outmost nerve is found just distal into the head of the gastroc muscle about two fingerbreadths off the tibial.

    The superficial fibular nerve, about 12 centimeters on average above the fibular malleolus and it’s in the lateral compartment of about 70% at the time. The deep fibular nerve is more of a provocative test than not so much because it is deep below the fascial band and that requires just a little more push. And if it’s hot, the patient will always draw it from your finger.


    Sural nerve will start about halfway down the leg, will have the highest confidence right on the lateral aspect of the Achilles tendon, about 12 centimeters, just proximal and lateral to the fibular malleolus but he may also elicit just about one and a half fingerbreadth below the posterior malleolus as well.

    Tibial nerve through the tarsal tunnel, we want to assess above, through and below each tunnel. Posterior tibial, medial and lateral plantar, and medial calcaneal nerve tunnel, and that may have bifurcations up to three. So be very careful and go slow through your tarsal tunnel.

    This neurogenic heal, if you have plantar fascia patients that are not responding to traditional care, make sure that you’re ruling out that they’re – you don’t have a nerve entrapment in there or your calcaneal nerve. It’s a very easy block. I’ll show you how to do it.

    Deep fibular nerve, this is an easy one. It’s probably the one everyone should start out with because it’s the most easy to palpate and to get appositive Tinel sign. It’s right in the interspace between the basis of the first and second metatarsal. The deep fibular nerve runs right with the dorsalis pedis. And if you palpate that just perfectly, you’re going to get a stinging pain down into the first and second toes, the interspace.

    And then lastly, posterior and proximal tibial nerve at the Soleal sling. There is a fiber span of tissue that’s created at the rough aid between the gastroc and the soleus muscle. It travels with that nerve, artery, and vein into that tunnel. So if anything is going to get compressed, it’s going to get compressed there, exertional compartment syndrome, as well it’s going to be big so I’ll have these patients stand, I’ll have them pump their calves single or double, if they can do it. And you place your finger in that crease about 9 centimeters distal to the back of the knee, it will drop them instantly if they’re – if their posterior tibial is entrapped.


    It will also send a residual pain down to the tarsal tunnel and into the plantar foot. So always, again, when you’re assessing your tarsal tunnel patients, make sure that you’re ruling out a posterior tibial nerve entrapment.

    Once you complete your physical exam, we’re going to consider diagnostic blocks. And these are going to be performed on our suspected diagnosis to determine what affects nerve decompression, nerve neuroplasty, neurectomy, or denervation might have on that patient. And when we say that, it’s good to excellent results.

    There is a quote, “Right volume makes up for accuracy.” These are not surgical blocks. These are very elegant 1 cc, low volume, low dose blocks. And it’s important because you have to differentiate between any sort of anomalous or accessory nerve innervations as these nerves are traveling down. These – but we all know bodies don’t read the book. So we’re always going to find these anomalous nerves in patient. And if you have patients with intractable pain, it’s probably because they have an anomalous nerve.

    This lecture was made from a much larger lecture on practice management for nerve as well. But I wanted to offer this pearl because peripheral nerve blocks are really a wonderful way to evaluate and assess these patients and tee them up for surgical management.

    In the office, we’re probably doing 64455 for peripheral nerve injection. We can do that for intermetatarsal neuroma. We can do that for tarsal tunnel, superficial fibular, common fibular, low volume, low dose block, recording what we’re finding. But understand that there is an allowance that you’re allowed, 3 injections per anatomical site every 6 months. So when you’re working these patients up, understand that even with Medicare as your primary, you may have to continue your nerve mapping but you may not be getting paid for the nerve blocks as far as you’re going.


    So just be cautious about that. Not that it’s all about the money, but let’s get paid for what we do. And don’t worry if this is happening from a denial perspective because bill for what you do, and if it denies, understand why you’re denying and don’t waste the time on the appeal.

    Any time that I give a peripheral nerve block, anywhere, I give my patients this Peripheral Nerve Block Sheet. And the response to treatment chart on the back is because patients don’t remember. They have no idea what you told them in the room. They don’t understand why you gave them the block in the first place. But we are using this chart to chart their VAS from day 0 to day 10, and it’s an AM and PM skill. And when they come back, we’ll review this together. And if we’re continuing to nerve map, and we do a second injection or a much more proximal block, then we have now two data points and two charts that we can use so that the patients really understand that they’re actually getting a significant pain reduction.

    So some pearls is that I block as for approximately as possible in the leg first. I do not block the common fibular nerve to diagnose nerve entrapment. I do that through my musculoskeletal testing. I block nerves to differentiate the geographic sensory patterns of innervation and I block above and below the fascial planes to determine if there is a possible variation in that nerve track.

    So what can we find, right? Let’s sum it up. So, yeah, is there a proximal nerve lesion? We evaluated that with our musculoskeletal on lumbar sacral spine. Is there is a specific peripheral nerve trunk that’s giving us? Is there any anatomical variation? And what further testing are we going to do whether in the office or out? So is it going to be an electrophysiology or are we going to use the PSSD? Do we need a lumbar MRI for lumbosacral radiculopathy?


    And do we need work up any of the bloods to make sure it’s not a seronegative or seropositive arthropathy? And who else is on our pain team, right? Do we have our neurology, orthopedics, psychiatry, or medical doctors to help with all of these?

    So in your summary, you’re going to list why you think the specific nerve trunk lesion versus proximal nerve root lesion or is it an idiopathic polyneuropathy? And the information is really beneficial not only for your credibility, but to the referring physician to their PCP, to Workers’ Comp case workers, to adjudicators for denial. And your detailed neurological examination will add credibility not only to your diagnosis, but it will demonstrate your competence and your expertise.

    You also need to consider that the diagnosis just as in aside, of intractable chronic pain or centralization of pain is a diagnosis of exclusion, and it can really only be made out after ruling out treatable conditions of peripheral nerves versus orthopedic conditions. It’s part of a much larger lecture where we talk about how our – how us as surgeons are on the multidisciplinary pain team, and we’re often communicating with physicians who are non-surgeons, and they’re making decisions based on non-surgical criteria.

    So, when we have our paperwork like this, which is after a nerve exam, I’ll fill out these four pages, and this will be part of my electronic health record. I use that to prove to whoever’s looking at this patient how thorough the examination we are. It’s also important for me because I forget, and I need to look back and make sure exactly where it is.

    Additionally, I photograph, you saw in the beginning of those pictures, every patient. So if we’re finding a positive Tinel sign, I’ll write on the patient, and I’ll draw dates, and I’ll draw where the Tinel sign is, if there’s a provocation sign, if there’s anesthesia or perusal.


    I’ll mark it on the patient’s leg and photograph it, and every time we give injections, as those patients are coming back, I’ll review that picture, “Oh, we gave you any SFN. All right, let’s move just two centimeters distal and see if we can localize it even better.”

    So, the last few slides we talked about and understand that pain is a physiological response to a noxious stimulus and it’s intended to trigger protective behaviors in humans, and it’s to limit that tissue damage. And our job is to identify and stop these sources of activation and peripheral nerve pain, but we also need to recognize that we’re absolutely not alone on this, and we should be outsourcing to our pain team.

    So, here’s a list of the cooperative specialist that I use as a part of my pain team, and I form this in my geo-location so that I can find people that are going to be like-minded, that are interested in these pain patients. And you can see that from psychiatrists, to psychologists, to social workers and case workers, we’re on the surgeon for the lower extremity but I have orthopedic colleagues and plastic surgery colleagues that will do everything from the spine up.

    Physical medicine and rehab, podiatrist, they’re really bright and they are non-surgeons. They do a lot of lumbarsacral blocks for me and they do a lot of McKenzie protocol for PT, for me as well. And then physical and occupational therapy is going to be important in these patients as well.

    Okay, what’s next, right? I know it’s a lot and it goes really fast, and I’m sorry that I don’t have more time, but this is to plant a seed for a much bigger lecture and a much bigger course. We’re supposed to be the masters of foot and ankle. We’re supposed to have mastery in all of it from the knee down.

    So part of the anatomy that is often overlooked in our profession is nerve.


    You guys are going to look at x-rays and you’re going to think that everything looks perfect on film, but the patient is still in intractable pain. Well, did you cut through the internervous space? Did you bag a nerve? Was it you or your assistant in the operating room? What happened? Is it a neuroma incontinuity, is it a neuroma in situ, or is it a severed nerve? Understanding how we can figure that out from a diagnostic’s perspective is going to make you just a much better clinician and a better surgeon.

    So, in the last minute or so, what can you do immediately Monday morning? Well, for the established practitioners, I’ve just increased your E&M level by – and I also added diagnostic-anesthetic blocks. So you can have confidence in both of those things from a medical necessity perspective, that the work that you did, you should be paid for.

    You’re going to need to invest in loops. You cannot do this at a macro level. Microsurgical training is expensive and loops are expensive. So the commitment is there.

    So investing loops 3.5 or higher, you need to do some microsurgical training, I did mine at Mayo. It is a wonderful training program, and anybody that can do it, go do it. If you have the opportunity, please. You have to have experience with the technology, the techniques, and the systems, and it doesn’t happen overnight. It’s not something that we can do in a 30-minute evaluation.

    Then, if you want to do this work, you have to consider the delineation of privileges at your hospital as well. So you have to meet with the MAC, or your hospital-based, or your ASC, and have these privileges written into your delineation of privileges.

    And then of course, right, anatomy reviews, cadaver dissections, procedure learning curve, what’s the difference between a neurography, neuroplasty denervation, allograft repair? How do we do inter-operative nerve monitoring? The rabbit hole goes deep and it is a really wonderful and fulfilling part of our profession. So if you have any questions about where we are and what we can do, it’s not just orthotics, and it’s not just biomechanics, and it’s not just bunions.


    We can have all of those things in a really robust practice and find some really fulfilling things because we’re actually changing people’s lives.

    That’s all I got. Thank you very much.

    Tape Ends [0:30:27]