Why do you think that it may be nerve damage when your vets think that your horse has a fractured pelvis? Or are the vets exploring other/additional possible diagnoses?
Are you still having the physio out? Did the vets suggest that a physio look at the horse? In the case of a possible pelvic fracture, the horse should be kept as quiet and as comfortable as possible, and not prodded or poked for many weeks.
Not an expert by any means.
Had a horse that developed stringhalt that also showed nerve damage in hind leg.
From my research at the time it appeared to be linked to damage to the pelvic/sacro region where the nerve bundle originated from.
So unless you have direct trauma to a limb to cause the localised issue, I’d imagine more likely that limb neuro issues will originate from higher up - trauma/compression or the like