Hi Heath,
This is a good question,
EPL dysfunction following a distal radius fracture is most commonly associated with the Listers tubercle being involved in the fracture leaving an abrasive edge for the tendon to pass around. This often leads to tendon rupture over time.
I presume the part of the PIN you have seen swollen is the distal part deep to the compartment 4 tendons.
Swelling of this part of the PIN is associated with dorsal carpus pain, however in my hands I find it a very difficult diagnosis as the distal PIN seems to have a wide variety of sizes when you scan normal volunteers and also the contralateral side. I find this a very difficult ultrasound diagnosis and would be more inclined to be guided by the clinical rather than the sonographic evidence.
I don’t see how EPL function can be linked to the distal PIN as it has already provided the motor function proximal to this level. If it was swollen at the Arcade of Frohse this might make sense. But if this was the case I would expect some clinical weakness of supination, ECU, EDC, EDM and APL function.
What did the muscle belly look like when compared to the other side?
Steve