Purpose: Associated factors for and the natural course of sacroiliac (SI) joint degeneration in the normal population are unknown. The purpose of this study was to determine associated factors for and the progression rate of SI joint degeneration.
Methods: We enrolled 553 healthy middle-aged subjects who underwent the first and second comprehensive health screening at an interval of 5.9 years (range 3.0-10.7 years). The medical checkup included blood tests and whole-body computed tomography. We investigated associated factors of SI joint degeneration, the relationship of the laterality of degeneration between the SI and L4/5 facet joint, L5/S facet joint, and the natural course of SI joint degeneration over time.
Results: At the first checkup, 70 subjects (12.7%) showed substantial degeneration (type 2 or 3) of the SI joints. Multivariate analysis revealed that female sex; pubic symphysis degeneration, L4/5, and L5/S facet joint degeneration; high body mass index; and several blood parameters were associated factors for SI joint degeneration. Laterality of SI joint degeneration was significantly more frequent than that of L4/5 or L5/S facet joint degeneration. Kaplan-Meier survival analysis revealed that the progression rates of SI joint degeneration from type 0 (no degeneration) or type 1 (slight degeneration) to substantial degeneration amounted to 3.4% and 35.5% after 10 years, respectively.
Conclusion: We found substantial SI joint degeneration in 12.7% of healthy middle-aged subjects and considered it to be part of the normal aging process. There may be individual factors associated with its occurrence. These slides can be retrieved under Electronic Supplementary Material.
Keywords: Ankylosing spondylitis; Computed tomography; Incidence; SpA; Spondyloarthritis.