Comparison of Unilateral or Bilateral Fixation in the Treatment of LFS

Inclusion criteria: * Signed informed consent. * Patient is willing to be available for each examination scheduled over the study duration. * Lumbar foraminal stenosis diagnosed by patient history, physical examination and image confirmation. * Patient has symptoms referable to the stenosis level (low back pain, leg pain, tingling, numbness or weakness), which are relieved after a selective nerve root block. * Has not responded to conservative treatment for a period of 3 months (e.g. bed rest, physical therapy, medication, manipulations, other). Exclusion Criteria: * Has systemic infection, highly communicable diseases, inflammatory or autoimmune disease (e.g. osteomyelitis, crohn's, rheumatoid arthritis, systemic lupus, gout, HIV/AIDS, active tuberculosis, venereal disease, active hepatitis). * Has presence of active malignancy * Has a history of severe allergy * Has a significant medical history that, in the investigator's opinion, would not make them a good study candidate. * Pregnant, or may become pregnant within follow-up period of study * Has other spinal conditions that will interfere with clinical outcomes (e.g. spinal structural deformities, spinal fractures, ankylosing spondylitis, spinal tuberculosis, spinal infection, spinal tumors, symptomatic cervical spinal disease) * Spondylolisthesis at the target level * Has undergone previous lumbar surgery * Has severe osteoporosis (T-score ≤ -3.5) * BMI \> 35kg/m2 * Has a diagnosis, which requires postoperative medication that interferes with fusion, such as steroids. * Has history of endocrine or metabolic disorder known to affect osteogenesis (e.g. Paget's disease, renal osteodystrophy, Ehlers-Danios syndrome or osteogenesis imperfecta)