Study design: In vivo 3-dimensional facet joint space width measurement.
Objective: To determine lumbar facet joint space width within clinically relevant topographical zones in vivo and its correlations with age, level, and presence of lower back pain symptoms.
Summary of background data: Facet joint gap narrowing, articular cartilage thinning, and subarticular cortical bone hypertrophy are frequently observed age-related changes. Facet joint space width is a well-defined parameter to evaluate osteoarthritis. To the best of our knowledge, there is no other study that quantifies 3-dimensional facet joint space width distribution in vivo.
Methods: Three-dimensional measurement to quantify facet joint space width distribution based on 5 clinically relevant topographic zones in a cohort of healthy and symptomatic volunteers with low back pain, using subject-based 3-dimensional computed tomographic models with respect to spinal level, subject age, sex, and presence/absence of lower back pain.
Results: Facet joint space width (mean ± SD) was 1.93 ± 0.51 mm for the central zone, 1.75 ± 0.48 mm for the superior zone, 1.63 ± 0.49 mm for the inferior zone, 1.48 ± 0.44 mm for the medial zone, and 1.65 ± 0.48 mm for the lateral zone, respectively. There were no significant differences between right and left facet joints. Male patients showed larger space width than female patients. Overall, space width of symptomatic subjects was significantly narrower than that of the asymptomatic group. Facet joints in the peripheral zones were narrower than in the central zone. Age-group comparisons showed that local narrowing occurring as early as in the third decade at the inferior zone of L5-S1, with all the remaining zones implicated after the fourth decade.
Conclusion: This in vivo study shows variations in facet joint space width narrowing with spinal level and region within the facet joint and in vivo evidence of localized, age-influenced facet cartilage thinning. Techniques developed in this study may be applied in the detection of early osteoarthritis-related changes in the facet joints.