Sacroiliac Joint Fusion using the iFuse Titanium Triangular Implant System: Two-Year Clinical Outcome Study

Abstract

Research Question: In treating patients with sacroiliac joint (SIJ) dysfunction, how does SIJ fusion (SIJF) using the iFuse implant system impact longitudinal patient-reported outcomes (PROs) and pain medication use?

Background and Significance: SIJ dysfunction causes severe, debilitating lower back pain that often interferes with patients' daily living activities. It is considered a significant contributor to low back pain in the general population. However, it is amenable to treatment with minimally invasive techniques. Thus, we studied the longitudinal implications associated with SIJF using the iFuse implant system.

Materials and Methods: From October 2012 to December 2019, 230 operations on 212 patients, who had undergone SIJF with the iFuse system, were identified. Demographic and clinical characteristics were analyzed with patient reported outcomes (PROs) including the Oswestry Disability Index (ODI), 5-level EuroQol-5D (EQ-5DL), and Likert scales for satisfaction and likelihood to repeat the operation for the same diagnosis. Oral morphine milligram equivalents (MME) were calculated from patient-reported analgesic use. Univariate linear regression and Least absolute shrinkage and selection operator (LASSO) regression analyses were utilized to identify factors associated with outcomes.

Results: A total of 35 patients (median [range] age, 62 [31-79] years; 25 [71.4%] female) responded to the online survey with outcome data of 3.84 [2.07-8.4] years. Satisfaction was 'very satisfied' in 45.7% of patients and 34.3% of patients were very likely to repeat the operation for the same diagnosis. Post-operative ODI score (33.6% [20.7]) was significantly lower than pre-operative values (49.3% [11.1]; p=0.009). Multivariate predictors of ODI disability score included follow-up time, EQ-5DL level sum score (LSS), and surgery repeat likelihood. EQ-5DL 'mobility' was 2 (range, 1-5), 'self-care' was 1 (range, 1-3), 'usual activities' was 2 (range, 1-5), 'pain discomfort' was 2 (range, 1-4), 'anxiety and depression' was 2 (range, 1-5), and 'health score' was 68 (range, 29-90). Mean EQ-5D LSS in the entire cohort was 0.56 (0.34) and multivariately predicted by ODI disability, Gabapentin daily drug dose (DDD), narcotic use, pre-operative pain duration. Most patients reported having pain for 1-3 years (n=17, 48.6%) while only 3 (8.6%) patients experienced pain for less than a year. Seventeen (48.6%) patients reported taking at least one pain medication and median MME was 0 (range, 0-75). Increased MME was univariately associated with worse VAS overall health scores (B -0.44; 95% CI -0.78,-0.09; p=.02) but not satisfaction nor likelihood to repeat the operation (p>.05). Finally, neither pre-operative ODI disability (B 0.44; 95% CI -1.2, 2.1; p=0.5) nor pre-operative pain duration were associated with MME.

Conclusion: Our data suggests that SIJ fusion is associated with high satisfaction, long-term benefits, and relatively minimal long-term post-operative narcotic use. Pre-operative pain duration did not affect PROs, indicating that positive outcomes are possible regardless of the chronicity of their pain. Pre-operative disability nor chronicity of pain were associated with MME, of which increases resulted in worse health overall. Future multi-center studies are needed to identify pre-operative factors that are associated with these longitudinal effects on patient quality of life and disability following SIJF.