Improvement in Health State Utility after Sacroiliac Joint Fusion: Comparison to Normal Populations

Study Design Prospective cohort study. Objective The sacroiliac joint (SIJ) is an important cause of lower back pain. The degree to which minimally invasive surgical fusion of the SIJ improves health state utility has not been previously documented. Methods Health state utility values were calculated using the EuroQOL-5D (EQ-5D) and Short Form-36 (SF-36) at baseline and 6 and 12 months after SIJ fusion surgery in subjects participating in a prospective, multicenter clinical trial (n = 172). Values were compared with individuals who participated in a nationally representative cross-sectional survey (National Health Measurement Study [NHMS], n = 3,844). Health utility values in the SIJ cohort were compared with those of the NMHS participants using both weighted linear regression and calculation of "health quantile" (i.e., percentile of health normalized to the NHMS cohort adjusted for age and gender). Results Baseline health state utility was significantly depressed in SIJ patients compared with normal subjects (SF-6D 0.509 versus 0.789, SF-36 physical component summary 31.7 versus 49.2, SF-36 mental component summary 8.5 versus 53.8, EQ-5D 0.433 versus 0.868; all p < 0.0001 after adjustment for age and gender). In the SIJ cohort, all the measures improved by 6 months postoperatively, and improvements were sustained at 12 months. Baseline health quantile was low (fifth percentile) in the SIJ cohort and improved significantly at follow-up. Conclusions Quality of life is markedly impaired in patients with SIJ pain compared with age- and gender-matched cohorts. SIJ fusion in this cohort resulted in a substantial improvement in health state utility, bringing the population back toward the expected levels of overall health. The quantile approach helps to explain the degree to which health is improved compared with age- and gender-matched cohorts.