What Causes Muscle Contraction At The Lumbar Zone?

hi,
my wife had a discal hernia surgery 2 weeks ago.
after 3 days we went home by car about 300 km and she got a little disturbance on the road
arrived at home same night she had a little fever 37,8
the pain begun contro lateral left side , the surgery was right side L4L5
the fever stopped in hospital after 2 antibiotics
the pain is still there after 2 weeks after surgery
she cannot get off the bed
she has a strong muscle contractura athe lombar zone
the rmn shows everything it s ok now after the surgery
what can be the problem\
thanks a lot
Octavian