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A man presented with “aching” and “burning” pain, persisting for nine years, in his right dorsal foot and lower medial calf. Standing or walking exacerbated the pain. On average, the pain was 2/10 on the 0-10 pain scale (0 = none, 10 = worst imaginable), but would rise to a maximum of 9/10 with activity. Orthotic devices and cortisone injections provided no relief. The patient did not recall any triggering event but noted a sports injury that occurred four years before the onset of the pain. During the incident, he fractured his foot (anterior process of the calcaneus) and felt a "pop" in his leg. He experienced some pain following the event, but felt fully recovered after a month. The patient saw multiple specialists before consulting with our foot and ankle surgeon, and had been recommended an ankle arthrodesis. Of note, the radiographs of the patient acquired prior to our PET/MRI study included only the foot (i.e. the primary location of pain), revealing abnormalities from the unrelated foot fracture.


Figure 1 shows increased 18F-FDG uptake related to chronic foot pain. (A) Coronal view of lower portion of whole-body PET, showing increased radiotracer uptake in the right plantaris muscle belly (red arrow) and in the right foot and ankle (green arrows). (B) Axial 18F-FDG PET (left) in the dorsal part of the ankle/proximal foot shows increased tracer uptake where the patient describes his main symptoms (white arrow). Axial time-reversed FISP (PSIF) MR image (right) at the same level shows this to be in the vicinity of the right deep fibular nerve but appears normal. 

PET MR plantaris.png

Figure 2 shows Figure 2 a ruptured plantaris tendon with hematoma. (A) Axial double-echo in steady state (DESS) MR image, showing the ruptured right plantaris (red arrow) compared to the normal, left plantaris (green arrow). A large, partially liquefied hematoma is located between the soleus muscle and medial gastrocnemius muscle, visible as increased signal on MRI, likely causing mass effect on surrounding structures. (B) 18F-FDG PET/MRI co-registered image, showing that increased radiotracer uptake coincides with the abnormality visible on MRI (white arrow).

PET MR plantaris axial.png


The 18F-FDG PET/MR findings suggest the exacerbated pain during ambulation might be caused by altered mechanics due to fibrosis of the inflamed plantar muscle belly. In addition, increased 18F-FDG uptake was observed in the dorsal surface of the midfoot, where the patient described his main symptoms (Fig 1).  

Upon review of the scan results, the patient noted that the region of his plantaris muscle felt tight. The surgeon suggested tenotomy of the plantaris tendon to mitigate aggravation of pain with activity, as this procedure was low-risk and would sever the connection between ankle movement and the ruptured plantaris muscle. The patient elected to proceed with the surgery. Under local anesthesia with sedation, the plantaris tendon was identified just medial to the Achilles tendon. It was dissected proximally and distally, and a centimeter was excised. A soft wrap was placed, and the patient was allowed to bear weight immediately. The patient was seen two weeks after surgery and reported no significant pain in either his foot or calf. At 3-month follow-up, the patient was free of pain and able to walk without limitations.


Here, we describe a successful application of whole-body 18F-FDG PET/MRI to a case of unsolved chronic foot pain of nine years. Our imaging findings led to the modification of the treatment plan from ankle arthrodesis to a lower risk tenotomy of the plantaris tendon, which achieved pain relief. This case report highlights how our 18F-FDG PET/MRI approach identified the pain generator, allowing for tailored treatment.

The patient was very satisfied with his result stating, "Dear Dr. Biswal, The surgeon performed surgery on my leg to cut the bottom of the plantaris tendon on my right leg. My leg is much better. I would deem it a success. I am stretching on a daily basis. The PET/MRI was the trail blazer that allowed this successful outcome. Thank you for your support through this."

The surgeon was also very pleased: "Patient with foot pain when walking had rattled around for several years.  Orthopedist suggested ankle fusion.  We were at a loss, so had PET MRI.  This showed a very bright plantaris muscle belly.  I figured that maybe plantaris was fibrotic and pulled with ankle movement. So I did a tenotomy of the plantaris tendon such that the ankle movement would not translate to the muscle belly and.....Home run  his pain is GONE!  He can now walk with out limitations. GO TEAM we are doing good stuff!


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