Sacroiliac Joint Fusion Intervention For Mobility, Pain Relief, and Lasting Improvement in Functional Recovery "SIMPLIFY"

The purpose of this study is to determine the clinical efficacy of The Trellis SI Joint Fusion System in unilateral sacroiliac (SI) joint fusion surgeries.

Inclusion Criteria: 1. Age ≥ 21 at time of screening; 2. Diagnosis of unilateral sacroiliac (SI) joint dysfunction (degenerative sacroiliitis or sacroiliac disruption) 3. Presence of low back/buttock pain and unresponsive to non-operative treatment for at least 6 months or has the presence of progressive symptoms in the face of conservative treatment; Oswestry Disability Index (ODI) score ≥ 30%; 4. SIJ pain score ≥ 5 on 0-10 numerical rating scale (NRS); 5. Ability and willingness to comply with follow-up regimen; and 6. Written informed consent by the patient Exclusion Criteria: 1. Low back/buttock pain due to other causes including, but not limited to, lumbar disc degeneration, lumbar disc herniation, lumbar spondylolisthesis, lumbar spinal stenosis, lumbar facet degermation, or lumbar vertebral body fracture; 2. Planned bilateral SI joint fixation 3. Received prior SI joint fusion1; 4. Cluneal neuralgia; 5. Inflammatory sacroiliitis (e.g., ankylosing spondylitis, psoriatic arthritis, reactive arthritis, non-radiographical axial spondyloarthritis, inflammatory bowel disease-associated arthritis); 6. Sacroiliac tumor as source of symptoms; 7. Sacroiliac fracture or unresolved trauma as source of symptoms; 8. Anatomic anomalies/defects that in the opinion of the Investigator preclude device placement 9. History of recent (\ 35; 17. Currently pursuing personal litigation (defined as litigation that will likely influence the patient's ability or willingness to accurately report their treatment outcomes) related to the sacroiliac; 18. Currently receiving worker's compensation related to the sacroiliac; 19. Current or recent history of substance abuse (drug or alcohol) per the Investigator's determination; 20. Mental conditions (e.g., schizophrenia, personality disorders) that could interfere with study participation, per the investigator's determination; 21. Use of any investigational drug or medical device within the last 60 days prior to surgery; 22. Tobacco and/or nicotine use within the last 60 days prior to surgery, or tobacco and/or nicotine use during the duration of the study; 23. Currently a prisoner; 1Prior allograft implant is acceptable and not exclusionary