I do not know the reason for the back surgery. I suppose due disc pathology or spinal stenosis
in lower level of the back(L4-5 and L5-S1). During surgery there might be touching of surgical instruments of the nerves which leads to edema and more pain which can last up to 3-4 weeks and treated by fysio and pain killers.A more serious situation might be nerve damage
due to edema or trauma to the nerve by the surgeon.To solve this an NMR after a periode of 4 weeks needs to be done.
Important is : do you have loss of power (standing on heel or toes)or sensory disturbance on the frontal or posterior part of your leg.