I assume that you had a disc herniation at L4-5 which caused both numbness as well as muscle weakness of the L5 nerve distribution which lead to your surgery. If your spasms are in this same leg, the cause could be nerve root chronic injury with chronic muscle weakness. If I am correct, the weakened muscle will cramp if overloaded. Muscles can also cramp without nerve injury due to metabolic changes and vascular insufficiency.
Dr. Corenman
PLEASE REMEMBER, THIS FORUM IS MEANT TO PROVIDE GENERAL INFORMATION ON SPINE ANATOMY, CONDITIONS AND TREATMENTS. TO GET AN ACCURATE DIAGNOSIS, YOU MUST VISIT A QUALIFIED PROFESSIONAL IN PERSON.
Donald Corenman, MD, DC is a highly-regarded spine surgeon, considered an expert in the area of neck and back pain. Trained as both a Medical Doctor and Doctor of Chiropractic, Dr. Corenman earned academic appointments as Clinical Assistant Professor and Assistant Professor of Orthopaedic Surgery at the University of Colorado Health Sciences Center, and his research on spine surgery and rehabilitation has resulted in the publication of multiple peer-reviewed articles and two books.