Facet joint tropism, pelvic incidence and intervertebral height index: associations with facet joint osteoarthritis in lumbar spinal stenosis.

Background Context: Facet joint osteoarthritis (FJOA) is associated with lumbar disc degeneration and has a significant role in the development of lumbar spinal stenosis (LSS). The relationship between various radiographic parameters and the grade of FJOA is not well understood.

Purpose: To explore radiographical parameters associated with FJOA in LSS without lumbar dynamic instability.

Study Design: Retrospective study analysis.

Patient Sample: A total of 122 patients diagnosed with LSS who visited our hospital between January 2015 and July 2022.

Outcome Measures: We evaluated radiographic parameters of patients at L4-5 including lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), grades of FJOA, facet joint orientation (FO), facet joint tropism (FT), intervertebral height index (IHI) and the relative cross-sectional area (RCSA) of paraspinal muscles.

Methods: Patients diagnosed with LSS between January 2015 and July 2022 were enrolled. Demographic characteristics and radiographic parameters were collected. Spinopelvic parameters were measured through the preoperative lateral image of the whole spine, including LL, PI, pelvic tilt, and sacral slope. Lumbar computed tomography scan and magnetic resonance imaging were collected to measure the FO, FT, IHI, and the RCSA of paraspinal muscles respectively. Patients were divided into three groups according to the severity of FJOA graded by the Weishaupt classification: grade 0 and grade 1 were group A, grade 2 were group B, and grade 3 were group C. All variables were compared among the three groups, while the relationship between parameters and grades of FJOA were also analyzed.

Results: A total of 122 patients were included. PI was significantly greater in group C compared to group A (p = 0.025) and group B (p=0.022). FT was significantly greater in group C compared to group A (p<.001) and group B (p<.001). The RCSA of multifidus in group A were significantly greater than that in group B (p=0.02) and C (p=0.002). Additionally, FO in group C were significantly lower than group A (p<.001) and group B (p=0.028). The IHI in group C was significantly lower than group A (p=0.017). The correlation analysis indicated that grades of FJOA was positively related to Age, BMI (body mass index), PI, LL and FT, while negatively related to IHI, FO, RCSA of multifidus and RCSA of psoas major. Furthermore, the logistics regression showed that FT, PI, and IHI were important influence factors for FJOA.

Conclusions: The current study confirmed that FT, PI and IHI were significantly associated with grades of FJOA at L4-5. Additionally, longitudinal studies are needed to understand the causal relationship between these parameters and FJOA.