Tenon Medical CATAMARAN™ SI Joint Fusion System CT Scan Study

Inclusion Criteria: * Patient \>18 years of age at time of treatment with the CATAMARAN SI Joint Fusion System * Patient implanted with the CATAMARAN Fixation Device within the last 12 months * Diagnosis of sacroiliac joint disruption or degenerative sacroiliitis * Patient, or authorized representative, signs a written Informed Consent form to participate in the study * Patient is willing and able to complete study follow-up requirements Exclusion Criteria: * Known or suspected active drug or alcohol abuse * Previously diagnosed osteoporosis (defined as prior T-score \<-2.5 or history of osteoporotic fracture) or prior/current use of drug therapy for osteoporosis. * Prior fracture of any bone related to cancer/tumor (i.e., pathologic fracture) * Prior diagnosis of tumor in sacrum or ilium * Unstable fracture of sacrum and or ilium involving the targeted SIJ * Osteomalacia or other metabolic bone disease * Use of medications known to have detrimental effects on bone quality and soft-tissue healing * Patient is pregnant or wishes to become pregnant during the study period * Patient is not likely to comply with the follow-up evaluation schedule * Patient is a prisoner or a ward of the state