Chip Anderson: A 36-Year-Old Maintenance Man With Numbness and Paresthesias in the Sole of the Foot





Learning Objectives





  • Learn the common causes of foot pain.



  • Learn the common causes of foot numbness.



  • Develop an understanding of the unique relationship of the posterior tibial nerve to the flexor retinaculum and bones of the foot.



  • Develop an understanding of the anatomy of the posterior tibial nerve.



  • Develop an understanding of the causes of posterior tarsal tunnel syndrome.



  • Develop an understanding of the differential diagnosis of posterior tarsal tunnel syndrome.



  • Learn the clinical presentation of posterior tarsal tunnel syndrome.



  • Learn how to examine the ankle and foot.



  • Learn how to examine the posterior tibial nerve.



  • Learn how to use physical examination to identify posterior tarsal tunnel syndrome.



  • Develop an understanding of the treatment options for posterior tarsal tunnel syndrome.



Chip Andersen







Chip Anderson is a 36-year-old maintenance man whom I have seen over the last several years. He came to the office today exclaiming, “Doctor, this time, I damn near got myself killed! I knew better, but I was in a hurry to get to lunch. I was hanging an emergency light on the stairs and didn’t want to take time to go back to the shop and get the correct ladder. My gramps always said, ‘haste makes waste’; now I know what he was talking about. The ladder slipped, and I tried to catch myself, but in the process I dislocated my ankle. Really stupid, huh? I definitely knew better. My ankle is getting better, but now I’ve got a numb foot and an irritating pins-and-needles sensation that shoots into the sole of my foot. I did my therapy just like I was supposed to, but it isn’t getting better.” I wouldn’t say that Chip is accident prone, but he has certainly had his share of on-the-job injuries: smashed fingers, lacerations, corneal abrasions. I had also seen him for the usual upper respiratory tract infections.


I asked Chip if he had experienced any foot or toe weakness, and he replied, “Doc, it’s funny that you asked. When I first got out of my cast, I thought it was just that my right foot was weak. And although I feel like I’m getting stronger every day, my foot feels like it’s unstable. Kind of like it’s squishy or flat—like I’m a cartoon character. It just doesn’t feel right. The other thing is, the toes on the right don’t seem to want to flex. After a day at work, especially if I’m on the stepladder a lot, I’ve been noticing that the bottom of my foot is really numb, and the pins-and-needles sensation is really aggravating.” Chip was certainly a talker. “Let me ask you a few more questions, Chip, and examine you so we can figure out what’s going on.”


I asked Chip what he had tried to make it better. He said when he elevates his foot, it seems to make the pain better, and after about 30 to 40 minutes, the numbness gets a bit better. “The melatonin seemed to help some, at least with the sleep. I bet that foot wakes me up 10 times a night. I feel like I need to shake it to get it to wake up.” I asked Chip about any fever, chills, or other constitutional symptoms such as weight loss or night sweats, and he shook his head no. He denied any other antecedent ankle or foot trauma. I took a look at copies of the x-rays that were taken on Chip’s arrival at the emergency room, and I had to agree that he really did a number on his ankle. It was surpising that he was doing as well as he was, given the extent of the trauma ( Fig. 5.1 ).




Fig. 5.1


X-ray of a posteromedial pure ankle dislocation. No fracture is noted.

From Wight L, Owen D, Goldbloom D, et al. Pure ankle dislocation: a systematic review of the literature and estimation of incidence. Injury . 2017;48(10):2027–2034 [Fig. 1]. ISSN 0020-1383, doi.org/10.1016/j.injury.2017.08.011 , www.sciencedirect.com/science/article/pii/S0020138317305259 .


I asked Chip to point with one finger to show me where it hurt the most. He pointed to an area just behind the medial malleolus and said that he felt like the pins-and-needles were coming from “right behind this bone right here.” He then rubbed the bottom of his right foot and said that it was really numb.


On physical examination, Chip was afebrile. His respirations were 18, his pulse was 74 and regular, and his blood pressure was 120/72. Chip’s head, eyes, ears, nose, throat (HEENT) exam was normal, as was his cardiopulmonary examination. His thyroid was normal. His abdominal examination revealed no abnormal mass or organomegaly. There was no costovertebral angle (CVA) tenderness. There was no peripheral edema. His low back examination was unremarkable. Visual inspection of the right ankle revealed a trace of edema, but there was no evidence of infection. The left foot and ankle were unremarkable. There was no rubor or calor. There was no obvious bony defect or tendinitis. There was a positive Tinel sign over the right posterior tibial nerve at the ankle ( Fig. 5.2 ). There was weakness of the toe flexors and I noted some flattening of the arch of the foot, suggesting weakness of the lumbricals on the right. There was decreased sensation in the distribution of the posterior tibial nerve on the right. There was tenderness to palpation of the area behind the medial malleolus on the right. A careful neurologic examination of the upper extremities was normal. I asked Chip to walk down the hall, where I saw that his gait was normal, which was pretty amazing, given the extent of his recent ankle injury.




Fig. 5.2


Positive Tinel sign over the posterior tibial nerve is usually present in patients suffering from posterior tarsal tunnel syndrome.


Key Clinical Points—What’s Important and What’s Not


The History





  • History of ankle injury with a dislocation of the ankle



  • History of onset of numbness of the sole of the right foot with associated paresthesias and numbness radiating into the distribution of the posterior tibial nerve



  • No history of previous significant ankle or foot pain



  • No fever or chills



The Physical Examination





  • Patient is afebrile



  • Positive Tinel sign over the posterior tibial nerve at the ankle (see Fig. 5.2 )



  • Weakness of the toe flexors on the right



  • Some flattening of the arch of the foot on the right, suggesting weakness of the lumbricals



  • Numbness of the sole of the foot in the distribution of the posterior tibial nerve



  • No evidence of infection



Other Findings of Note





  • Normal HEENT examination



  • Normal cardiovascular examination



  • Normal pulmonary examination



  • Normal abdominal examination



  • No peripheral edema



  • Normal upper extremity neurologic examination, motor and sensory examination



What Tests Would You Like to Order?


The following tests were ordered:




  • X-ray of the right ankle



  • Electromyography (EMG) and nerve conduction velocity testing of the right lower extremity



Test Results


X-ray of the right ankle reveals good alignment of the tibiotalar joint without malleolar fractures ( Fig. 5.3 ).


Nov 19, 2022 | Posted by in PAIN MEDICINE | Comments Off on Chip Anderson: A 36-Year-Old Maintenance Man With Numbness and Paresthesias in the Sole of the Foot
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