Comparative Study of Anterior vs. Posterior Surgical Treatment for Lumbar Isthmic Spondylolisthesis

Inclusion Criteria: * Aged 18 to 80 years, inclusive * Grade I, II or III (less than 75% slip of the cephalad vertebra compared to the caudal vertebra) isthmic spondylolisthesis at single level between L4 and S1 * Unresponsive to a minimum of 3 months of non-surgical treatment * No previous surgical treatment for isthmic spondylolisthesis * Patients who are medically suitable for surgical management * Patients who have consented for surgical treatment * Willing and able to comply with the Investigational Protocol (IP) * Informed Consent Form (ICF) signed by patient Exclusion Criteria: * Any previous lumbar spine surgery * Patient has significant scoliosis (Cobb angle is greater than 25 degrees) * Subject has cauda equina syndrome defined as neural compression causing neurogenic bowel (rectal incontinence) or bladder (bladder retention or incontinence) dysfunction * Subject is pregnant or of child-bearing potential and not currently on adequate birth control method * Active infection at the surgical site * Recent history (less than 1 year) of chemical substance dependency or significant psychosocial disturbance that may impact the outcome or study participation, in the opinion of the Investigator * Pre-existent neurologic or mental disorder which would preclude accurate evaluation and follow-up (i.e. Alzheimer's disease, Parkinson's disease, unstable psychiatric disorder with hallucinations and/or delusions or schizophrenia * Participation in another clinical trial of drug …