Hi cafra23
This sounds a complex case. Anything you could do to lead to a better diagnosis would be helpful. Based on your description I am not really sure what to make of it. Here are some suggestions you could consider:
You have described the sensory loss in some detail but I wonder if it might be worth having another look - try to map out the sensory loss to differentiate 1) dermatomal distribution or 2) peripheral nerve distribution or 3) neither pattern.
To have such a widely distributed motor deficit suggests something fairly proximal. I am sure the CT/MRI included the spine and leg but did it include the brain? Have you checked for upper motor neurone signs, just in case? The neurologist might already have done this but it might be worth just checking.
How much detail do you know about the nerve conduction study? Is there a clear picture over which nerves are "sluggish"
Could he have a functional (hysterical) component (somatoform disorder) to the problem? He is obviously truly injured but perhaps there could be a functional component that may account for the profound muscle weakness. Clinically this is not that uncommon following trauma - for example the spinal units get quite a few cases. This could possibly explain the active dorsiflexion in stair climbing but not on instruction.
Has the swelling over the trochanter been imaged? - ultrasonography might be relevant. However sounds like a red herring in terms of his paralysis.
As for the problem with the passive dorsiflexion it would be interesting to try to differentiate if this could be a mechanical problem of the ankle joint due to trauma or if it could be part of a somatoform problem. If you could stick an EMG on the tib anterior muscle belly to see what is happening - I am wondering if it might be working hard but he can't "switch it off".
All the best with sorting this guy out. Keep us posted how you get on.