How effective is having spinal fusion with decompressive laminectomy?

Depends on reason: This depends on the reason for this type of surgery, the number of levels involved. , whether this is a repeat surgery, the health and age of the patient, the smoking status of the patient, their weight and nutritional status and other co morbidities or problens like diabetes, thyroid disease, etc.. The bone density can also play a role, ie, osteoporosis.