Evolusion Study Using the Zyga SImmetry Sacroiliac Joint Fusion System

Key Inclusion Criteria: * At least three positive provocative tests for SIJ pain * Non-operative management of SIJ pain for ≥ 6 months prior to surgery * At least one positive diagnostic SIJ injection resulting in a ≥ 50% decrease in pain * VAS back pain score of ≥ 60 mm * The subject is at least 18 years of age Key Exclusion Criteria: * Trauma causing fracture of the sacrum or iliac bones or has had spinal trauma leading to a neurological deficit, or pelvic soft tissue or bony tumors * Pregnant or is planning on becoming pregnant in the next two years * Chemical dependency abuse problems as evidenced by a history of abusing drugs which is documented in their past medical history or is elicited from an interview. * Receiving or seeking worker's compensation, disability remuneration, and/or involved in litigation related to low back or SIJ pain * History of significant emotional or psychosocial disturbance