Post-Market Clinical Study on a Modular SI Joint Fusion System

Inclusion Criteria: * Subjects meeting all of the following inclusion criteria by the end of the screening phase should be considered for admission to the study: * Age 18-85\* (\*Over 85 is allowed with H\&P assessment screening upon approval by Medical Monitor); * Absent condition of high-risk surgical candidate (see training manual for definition); * Patient has lower back pain with a confirmed diagnosis of sacroiliac joint disruption or degenerative sacroiliitis for a period of \>6 months and who has not responded to optimal conservative care (PT or prescribed HEP, optimal medical management including NSAIDs); * Diagnosis of sacroiliac joint disruption or degenerative sacroiliitis based on ALL of the following: a. 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), and b. at least three positive findings with provocative maneuvers (FABER, Gaenslen, Thigh Thrust or Posterior Shear, SI Compression, SI Distraction, and Yeoman Test); * Patient has a diagnostic SIJ injection (SIJI) that provided a minimum of 75% relief of primary (index) pain with the diagnostic SIJI on two separate occasions; * Patient meets Medicare and payer requirements for medical necessity, see detailed requirements in training manual; * SI joint disruption: Asymmetric SI joint widening on X-ray or CT scan or degenerative sacroiliitis with radiographic evidence of SIJ degeneration as evidenced on CT or X-ray; * SI joint pain or instability with or without prior lumbar/lumbosacral surgery; * Baseline Oswestry Disability Index (ODI) score of at least 30%; * Baseline SI joint pain score of at least 60 on 0-100mm visual analog scale (or at least a 6 on NRS); * Patient has the necessary mental capacity to participate and is physically able to comply with study protocol requirements; * Failed SIJ fusion revisions can be included if all other inclusion criteria are met; * Patient must be able to communicate with study personnel via phone, text, or email; * PI must confirm women of childbearing years are not pregnant or plan to become pregnant prior to surgery; * Cardiac Clearance for patients with diagnosis of cardiac disease; * Patient has signed study-specific informed consent form. Exclusion Criteria: * Patient will not be entered into the study if they meet one of the following criteria: * Current severe back pain due to other causes, such as lumbar disc degeneration, lumbar disc herniation, lumbar spondylolisthesis, lumbar spinal stenosis, lumbar facet degeneration, lumbar radicular pain that extends beyond the mid-thigh, and lumbar vertebral body fracture; * SIJ pain secondary to inflammatory conditions or other known sacroiliac pathology such as: Sacral dysplasia, Inflammatory sacroiliitis (e.g., ankylosing spondylitis or other HLA-associated spondylo-arthropathy), Tumor or infection in the SI joint, Acute fracture or Crystal arthropathy; * History of recent (\<1 year) major trauma to pelvis (MVA or significant accident that results in acute injury to pelvis requiring hospitalization or surgery); * Previously diagnosed osteoporosis (defined as prior T-score \<-2.5 or history of osteoporotic fracture). If patient meets the osteoporosis screening criteria identified by the National Osteoporosis Foundation, they should be screened for osteoporosis with DEXA; * Autoimmune - patient who is currently not maintained on a medication regimen for treatment, and not stable (\<6 months without exacerbation); * Any condition or anatomy that makes treatment with the TransLoc 3D Sacroiliac Joint Fusion System infeasible; * Current local or systemic infection that raises the risk of surgery; * Patient currently receiving disability remuneration, and/or involved in injury litigation; * Patient is undergoing treatment under Workman's Compensation under a claim or injury greater than 1 year; * Patient is participating in an investigational study or has been involved in an investigational study within 3 months prior to evaluation for participation; * Known to be pregnant, suspected pregnant, or planning to be pregnant prior to SIJ surgery; * Patient is a prisoner or a ward of the state; * Known or suspected drug or alcohol abuse; * Known allergy to titanium or titanium alloys; * Diagnosed psychiatric disease (e.g., schizophrenia, major depression, personality disorders) that is not well controlled for a minimum of two years and could interfere with study participation.