Sacroiliac Joint Fusion Using the iFuse Titanium Triangular Implant System: Longitudinal Outcomes Study

Introduction: Sacroiliac (SI) joint dysfunction causes severe, debilitating lower back pain that often interferes with activities of daily living. It is considered a significant contributor to low back pain in the general population and is amenable to treatment with minimally invasive techniques. This study aimed to characterize the patients who underwent elective SI joint fusion and evaluate the associated long-term outcomes. Methods: From October 2012 to October 2019, 230 eligible cases were identified. Demographic and medical history was collected retrospectively via chart review, while patient-reported measures were collected prospectively via electronic survey. The Oswestry Disability Index (ODI), 5-level EuroQol-5D (EQ-5DL), visual analog scale (VAS) for health, and Likert scales for satisfaction and repeat likelihood were utilized to evaluate long-term outcomes. Patient-reported medications were utilized to calculate opioid oral morphine milligram equivalents (OMME). Results: Twenty-nine patients (M=9; F=20) with a mean age of 61.07 years (SD 12.23, range 31-79) and outcome data, on average, 5.06 years (1.91, 2.66 - 8.38) from surgery were included. Prior to surgery, 12% of patients had pain for less than 1 year, 35% for 1-2 years, 15% for 2-3 years, 19% for 3-5 years, and 19% for more than 5 years. 50% of patients were very satisfied with their surgery, 27% were satisfied, 15% were neutral, only 8% were dissatisfied, and no patients were very dissatisfied. Overall, 38% of patients were very likely to repeat the surgery for the same diagnosis, while only 19% were very unlikely to do so. Mean total ODI score was 16.52 (10.65, 0-72), EQ-5DL mobility was 2.21 (1.14, 1-5), EQ-5DL self-care was 1.42 (0.65, 1-3), EQ-5DL usual activities was 2.38 (1.13, 1-5), EQ-5DL pain discomfort was 2.50 (1.10, 1-4), EQ-5DL anxiety and depression was 2.00 (1.10, 1-5), and VAS health score was 65.08 (17.97, 29-90). ODI total percentage was strongly correlated with VAS health scores (r = -0.6059, p=0.0017). The mean OMME was 5.65 (13.25, 0-50), which was correlated with ODI pain intensity (r=0.2159, p=0.0065), ODI total percentage (r=0.4478, p=0.0248), and VAS health scores (r=-0.4920, p=0.0148). Lastly, pre-operative duration of pain was not significantly associated with ODI scores or VAS health scores. Conclusion: Our data suggest that patients who electively undergo SI joint fusion using the iFuse implant system are mostly satisfied with the operation and likely to repeat it for the same diagnosis. Furthermore, the operation is associated with long-term benefits demonstrated by the mean time since surgery for the entire cohort and their associated ODI, VAS health, and EQ-5DL scores. Lastly, pre-operative pain duration did not significantly affect the patient-reported outcomes, indicating that patients can expect positive outcomes, regardless of the chronicity of their pain prior to the operation. Future studies should focus on predictive factors of these longitudinal measures of patient quality of life, disability, pain features, and return to activity following SI joint fusion.