Posterior-Inferior Intra-articular Cortical Piercing Titanium Implant for Sacroiliac Joint Fusion: Evaluation of Safety and Effectiveness Outcomes

Inclusion Criteria: 1. Age \> 21 years. 2. Patient has chronic lower back pain (≥6 months) refractory to non-surgical care. 3. Diagnosis of sacroiliac joint dysfunction (degenerative sacroiliitis or SIJ disruption) and scheduled to be treated with INTRA Ti. 4. Patient has SIJ pain of at least 5 on a 0-10 numeric rating scale (NRS) prior to procedure. 5. Participant has signed study-specific informed consent form. Exclusion Criteria: 1. ASA score 4 or 5. 2. Severe back pain due to other causes, such as lumbar disc degeneration, lumbar disc herniation, lumbar spondylolisthesis, lumbar spinal stenosis, lumbar facet degeneration, and lumbar vertebral body fracture. 3. Other known sacroiliac pathology such as: inflammatory sacroiliitis (e.g., ankylosing spondylitis or other HLA-associated spondyloarthropathy), tumor, infection, acute fracture. 4. Current diagnosis of cluneal neuralgia. 5. Previous SIJ implant placement, including allograft, on the treated (index) side. 6. Anatomic anomalies/defects that would preclude safe and/or biomechanically acceptable device placement. 7. History of recent (\<1 year) major trauma to pelvis. 8. Previously diagnosed or suspected severe osteoporosis (defined as prior T-score \< -2.5 or history of osteoporotic fracture). 9. Chronic rheumatologic condition (e.g., rheumatoid arthritis). 10. Current diagnosis of fibromyalgia. 11. Known allergy to titanium or titanium alloys. 12. Current local or systemic infection that raises the risk of surgery. 13. Patient currently receiving or seeking worker's compensation, disability remuneration, and/or involved in injury litigation. 14. Currently pregnant or planning pregnancy in the next 2 years (self-reported). 15. Patient is a prisoner or a ward of the state. 16. Known or suspected active drug or alcohol abuse, including opioids 17. Diagnosed psychiatric disease (e.g., schizophrenia, major depression, personality disorders) that could interfere with study participation.