177. Baxter’s Nerve: The Overlooked Cause of Chronic Medial Heel Pain

In this PT Snacks episode, host Kasey introduces Baxter’s nerve (the first branch of the lateral plantar nerve, also called the inferior/anterior calcaneal nerve) as an under-recognized source of medial plantar heel pain that can mimic plantar fasciitis and may account for up to 20% of chronic heel pain. We review the nerve’s motor and sensory roles, common entrapment zones near the distal tarsal tunnel and medial calcaneal tuberosity, and typical presentation including burning neuropathic pain, possible paresthesia, focal tenderness, and potential abductor digiti minimi weakness or atrophy. This episode outlines key differentials, relevant imaging and testing findings (ultrasound, MRI, EMG/NCS), and a treatment progressions.

00:00 Welcome to PT Snacks
00:14 Baxters Nerve Overview
02:14 Why It Matters
03:03 Anatomy and Entrapment
04:45 Symptoms and Differentials
06:11 Imaging and Testing
07:22 Clinical Exam Clues
09:04 Treatment Options
11:12 Key Takeaways
12:58 Wrap Up and Contact

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Transcript

Hi, welcome to PT Snacks podcast. This is Kasey, your host, and if you're tuning in for the very first time, what you need to know is that this podcast is meant for physical therapists and physical therapist students who are looking to grow your fundamentals in bite-sized segments of time. Now, today. I am excited about this topic 'cause we're gonna be covering something called Baxter's nerve. So just a fun differential diagnosis to have in your back pocket. Does it happen every single day? No, definitely not, but something to get your brain juices flowing a little bit. Before we do that, if you've been finding that this podcast has been really helpful to you and you wanna show some support, there's three main ways that you can one is just to tell a friend that you think would benefit from it, help 'em out. The second one would be to leave a review wherever you listen to this podcast. That really helps the show to be able to reach more people and grow and show those hosting services that they're not just random things that are not active anymore. And then the third one is there is a support the link below in the show notes where you can give whatever you feel comfortable to, that just helps to go towards the costs that are involved with doing this podcast in the first place. 'Cause it does require a little bit of money, even though I like to give out free information. So do what you feel like is right for you, or if you just want to listen, at least take the information and imply it into your clinical practice and grow from it. Don't just passively listen. So let's go ahead and dive into today's topic. So the Baxter's nerve essentially. When we're discussing this, I want you to go ahead and prime your mind to think about the foot specifically. The heel bacter nerve is the first branch of the lateral plantar nerve, so it's also called the inferior calcaneal nerve or anterior calcaneal branch. Personally, I think Baxter's nerve is a lot more of a fun name to call it, but it's a small mixed motor sensory nerve and it helps to provide motor supply mainly to the abductor digit MiniMe or adm and sensory supply to the calcaneal periosteum long plantar ligament and medial calcaneal tuberosity region. So entrapment of this nerve. Baxter's neuropathy is a pretty common and under-recognized source of medial plantar heel pain. A lot of times patients think it's plantar fasciitis and not necessarily always the case. So this can actually account for up to 20% of chronic heel pain being the most common neural. Source of plantar heel pain. So this if your patient is coming in with heel pain would probably be a good one to screen out. Now with nerves, let's think about if it's, there's a nerve entrapment, how do we assess for those versus screening out other things? So we're gonna spend a little time talking about. The nerve itself, and then we can go from there. So the origin of the nerve, it usually branches from the lateral plantar nerve just distal to its origin from the tibial nerve the tarsal tunnel, less commonly does it arise from the tibial nerve itself or from a common trunk with a medial calcaneal nerve. So again, branch off of the lateral plantar nerve. The course that it runs is essentially generally between the abductor hallucis and the quadratus plantae, or plantae, however you wanna say it, in the distal tarsal tunnel. Then it's gonna turn laterally, passes anterior to the medial calcaneal tuberosity. And then courses between the quadratus plantae and the flexor digitorum brevis, finally, where it then reaches and innervates the abductor digit mini. So this might be a good opportunity to review some anatomy of the bottom of the foot or just the foot itself. There are two main entrapment zones that you wanna keep in your mind. So the first one's gonna be more proximal. That's gonna be between the abductor hallucis fascia and the quadratus plantae near the distal tarsal tunnel. Often if there's. Abductor Hal's hypertrophy or flat foot related compression, and then distal. So the second site is gonna often be between the flexor digitorum brevis, and to the medial calcaneal tuberosity. Frequently associated with plantar fascia thickening or calcaneal spur enthosophyte. So what does this patient look like where we're thinking maybe they have Baxter nerve other than they have. Discomfort in their heel. So essentially, usually this is gonna present as medial plantar heel pain. But their pain may be more burning, may sound more neuropathic sometimes with paresthesia along the lateral plantar aspect of the foot. So they may have maximal tenderness just anterior to the medial calcaneal tuberosity or along the medial heel where the nerve is compressed. 'cause you're basically mimicking. What is causing the symptoms with chronic compression? There may be a weakness or a loss of resisted abduction of the fifth toe. Sometimes people are just weak in this anyways. We don't really. See people in the gym working on their digit minimi or you might even notice an atrophy of their abductor digit time mini on exam or imaging, especially if it's unilateral and you're comparing it to the other side. But important things to keep on your differential diagnosis list would be plantar fasciitis, for sure, tarsal tunnel syndrome, achilles tendinopathy, heel pad syndrome, calcaneal stress fracture bursitis, and bone lesions. So definitely wanna make sure that you're getting a good history on what happened leading up to this. What do their symptoms sound like? Does it sound neuropathic? Does it sound fascia related? Does it sound like an overuse thing, et cetera, so that you can use that to guide your actual exam. These patients can also get imaging. So an ultrasound can help to directly visualize Baxter's nerve in the tarsal tunnel and its relationship to the abductor hallucis and the quadr plant time. And that often can be really helpful for if they're gonna get some sort of injection in that area. To make sure that they're in the right spot and to guide them. An MRI can also be helpful to evaluate for if there is Baxter nerve or just to roll out other potential sources of problem. So on an MRI, you can see if there's any fatty atrophy or a volume loss of the addict digit enemy. Which is a hallmark sign of chronic Baxter's neuropathy. You may also see in Ines the fight of the plantar fascia, which is another way of saying like some sort of bony overgrowth or bone spur, something like that. Abductor haliss hypertrophy, soft tissue edema. Or maybe they also have plantar fasciitis, which is not a fun time. You can use nerve conduction studies or EMG to show if there's any denervation of the abductor digit mini, and that can help to support the diagnosis. But the sensitivity of the test might be a little bit limited. And then in your clinical exam, you're looking at how long they've had it. Do they have medial heel pain, neuropathic features for suspicious of something neuropathic? Maybe they've been treated for plenary fasciitis in the past and treatment failed. So you're looking for their history. If we're suspicious of the neuropathy, are there any symptoms indicating a neuropathy such as I mentioned before, where we're noticing some sort of tingling numbness, things like that? Signs of nerve compression. Or if they've had it for a long time, are we noticing any of that atrophy of the abuc or digit minimize, which is where we would see that compression? Where is their pain? Does it act similar to where we know that the course of that nerve runs? Can we add compression to it and bring it on? Can we roll out some other things as well? We can look at if they are tendered to palpation among the medial calcan border, anterior inferior to the tuberosity. We can try and do at tens to see if there's a reproduction of symptoms along the distal tarsal tunnel. And then also testing for abductor, digi minimize weakness or wasting, especially when their symptoms have been there for a while, which in my experience a lot of times. People have had these symptoms for a while 'cause they've usually tried treatment for plantar fasciitis or other things, and they just might not be seeing success with those treatments by that point. Especially consider backstage neuropathy when heel pain persists more than three to six months. Despite them going through the typical plantar fasciitis treatment. And if imaging shows isolated abductor digit atrophy or clear entrapment features, then of course that we're gonna look at that. So in terms of treatment, conservative treatment is gonna be the first line of defense and then maybe. Surgery or something for refractory cases. What we're essentially trying to do is. See if there's some way where we can offload the compression that's happening. So you'll have to look at the patient in front of you and see if there's any factors that you can help. Do they feel better in different shoe wear? Is this a specific type of shoe wear that they notice their pain with or is it across the board? If it's with specific ones, maybe we can put them in shoewear that does not recreate their symptoms and just create more of a healing environment. Are there aspects of where maybe. We can utilize some nerve mobilization techniques for backstage nerve. Thinking about what nerve it stems from. Sometimes even though this is a nerve compression issue sometimes nerve mobilization techniques can help to reduce the sensitivity of the nerve to movement and make its overall sensitivity level a little bit less. Or if there's something contributing to excessive stress in that area. Maybe there's weakness in other places that is transferring force to that area more than it should be. Like maybe they have really weak calves or something like that. That's something that we can also work to try and address to help that patient eventually get to a point where they can do what they wanna do and hopefully not deal with some heel pain. If this is not really working for them, then they may do some image guided injections or pain procedures like I was mentioning with ultrasound. If there's a lot of inflammation, then. Injections can be really helpful for calming down inflammation. If this is really not working at all, they could even do a surgical decompression. So they would basically open the distal tarsal tunnel and do a Baxter's nerve release. Especially if patients are not responding well after three to six months. Or or in some cases if they do an open decompression of the nerve as it crosses the . Abductor Haliss along its course that can also has been found to give pretty good symptomatic relief. But the practical key takeaways that I want you to get from this would be that the backstage nerve can be very clinically important mixed motor sensory nerve of the. Branch of the lateral plantar nerve and can frequently mimic or coexist with plantar fasciitis. So suspicion should be high in chronic medial heel pain, especially when it's being unresponsive to typical plantar fascia focused treatment. Especially if imaging shows any sort of abductor or digi minimize atrophy or a clear distal tarsal, tunnel pathology, MRIs and ultrasounds can be helpful for modern assessment. And generally the progression of treatment is gonna start with conservative to maybe some sort of injection to surgery. You might be doing injection or injection with therapy or eventually maybe some sort of decompression. So the main purpose of this episode is essentially to make you aware of this as a differential diagnosis. In some ways for you to, based on your knowledge of where it runs. And what components it's made up of. Motory and sensory. How if, especially if someone's not responding to your treatment very well, we can screen for this and make sure that this is not also at play or the actual reason why they're having it, and we don't actually have the other thing we thought they did. And then from there, trying to reduce the decompression. Whatever you glean from your exam. That could be leading towards that, whether it's their foot itself, the shoe wear that they're in the stress that's maybe going through that area, how we can. Decrease that, create a healing environment, calm the nerve down and get them back to what they wanna do. So if you have any questions at all, feel free to reach out at PTs next podcast@gmail.com. I will do my best to answer your questions, but other than that, I hope you guys have a great rest of your day and until the next time.