Suggest Treatment Fro Neck And Back Pain After An Accident

My Husband was in a car wreck last week where two where killed and it was a four car wreck and he was the last of the vehicles to get bumped in the wreck. he had just minor neck and back pain and he was fine on friday, saturday and sunday. monday am he got up to get dressed for work and was standing to put his sock on and his back went out and hit the floor and has been unable to walk for two days and the rest of the week he has been able to walk with a walker. hospital released him due to nothing showing up on CT scan or an MRI, any suggestions as to his problem?