SALLY studies sacroiliac joint fusion with the iFuse-3D implant.

Participants will all get sacroiliac joint fusion on this study using the iFuse-3D titanium implant, manufactured by SI-BONE, Inc. Participants will be followed for clinical outcomes at pre-planned time points on the trial. Participants will be randomized to CT scan at 6 months or 12 months, and all will also get a CT scan at 5 years, the final visit for the study.

Inclusion Criteria:

1. Patient age 21-70 at time of screening.

2. Patient has suspected SI joint pain for greater than or equal to 6 months inadequately responsive to conservative care.

3. Diagnosis of sacroiliac joint dysfunction on one or two sides to be treated on study that is a direct result of sacroiliac joint disruption and/or degenerative sacroiliitis and is based on ALL of the following:

   1. Patient has pain at or close to the posterior superior iliac spine (PSIS) with possible radiation into buttocks, posterior thigh or groin and can point with a single finger to the location of pain (Fortin Finger Test) (on any targeted side), and
   2. Patient has positive findings on at least 3 physical examination maneuvers that stress the target SI joint(s) and
   3. Patient has block on any study targeted side with improvement in SI joint pain numeric rating scale (NRS) at 30 or 60 minutes of at least 50% after injection of local anesthetic into any affected SI joint with an immediate pre-block NRS of at least 5.

4. Baseline Oswestry Disability Index (ODI) score of at least 30%.

5. Baseline (average over the last week) SI joint pain score of at least 50 on 0-100 mm visual analog scale on any side to be treated under the study.

6. Patient has signed study-specific informed consent form.

7. Patient has the necessary mental capacity to participate and is physically able to comply with study protocol requirements.

8. Patient's insurance coverage for SI joint treatment has been considered and plan is to submit all study-related healthcare to insurance (or it is the patient's responsibility) (any required preauthorization should be completed prior to randomization on study).

9. Investigator believes patient is appropriate candidate for surgery using iFuse-3D Implant.

Exclusion Criteria:

1. Patient has bilateral SI joint symptoms with VAS pain scores ³50 on both sides and patient refuses to undergo bilateral treatment according to the study protocol.

2. Patient is currently pregnant, actively trying to become pregnant or is planning to become pregnant in the next year.

3. Severe back or hip pain due to other causes, such as lumbar disc degeneration, lumbar disc herniation, lumbar spondylolisthesis, lumbar spinal stenosis, lumbar facet degeneration, lumbar vertebral body fracture, piriformis syndrome, femoral acetabular impingement, labral tear or hip osteoarthritis. Patients with low back pain VAS ratings more than 50 should be carefully considered; they should not participate if the investigator believes these non-SIJ conditions would impair improvement from SIJ treatment.

4. SI joint dysfunction due to an alternative explanation such as:

   1. Inflammatory sacroiliitis (e.g., ankylosing spondylitis or other HLA-associated spondyloarthropathy)
   2. Tumor
   3. Infection
   4. Acute or unstable fracture.

5. History of recent (<1 year) major non-pregnancy-related trauma to pelvis.

6. Surgeon believes patient body habitus prevents surgery.

7. Previously diagnosed osteoporosis (defined as prior T-score <-2.5 or history of osteoporotic fracture) or prior/current use of drug therapy for osteoporosis.

8. Prior fracture of any bone related to cancer/tumor (i.e., pathologic fracture).

9. Prior diagnosis of tumor in sacrum or ilium.

10. Unstable fracture of sacrum and or ilium involving the targeted SIJ.

11. Osteomalacia or other metabolic bone disease.

12. Diagnosed or suspected chronic rheumatologic condition (e.g., rheumatoid arthritis, lupus).

13. Any known condition or anatomical deformity or variation that makes treatment with the iFuse-3D Implant infeasible.

14. Any known health condition that could prevent long-term follow-up required in this study.

15. Known allergy to titanium or titanium alloys.

16. Use of medications known to have detrimental effects on bone quality and soft-tissue healing.

17. Current local or systemic infection that raises the risk of surgery.

18. Patient currently receiving or seeking short- or long-term worker's compensation related to the SI joint or low back pain, currently receiving disability remuneration related to SI joint or low back pain, and/or currently involved in injury litigation related to the SI joint or low back pain.

19. Patient is a prisoner or a ward of the state.

20. Patient has known or suspected active drug or alcohol abuse.

21. Patient is unwilling to sign the study-associated opioid contract.

22. Diagnosed uncontrolled psychiatric disease (e.g., schizophrenia, major depression, personality disorders) that could interfere with study participation.

23. Patient is participating in an investigational study or has been involved in an investigational study within 3 months prior to evaluation for participation.

24. Patient has known or suspected fibromyalgia.