Lumbar facet anatomy changes in spondylolysis: a comparative skeletal study

Area of Science:

• Orthopedics
• Biomechanics
• Human Osteology

Background:

• Spondylolysis (SP) is a stress fracture of the pars interarticularis.
• The exact mechanism and predisposing morphological factors for SP remain debated.
• Understanding lumbar spine architecture is crucial for identifying individuals at risk.

Purpose of the Study:

• To investigate the association between spondylolysis (SP) and the morphological characteristics of lumbar articular facets and the inter-facet region.
• To identify specific anatomical features that may predispose individuals to SP.
• To elucidate the relationship between L4 vertebral morphology and L5 spondylolysis.

Main Methods:

• 3D measurements of lumbar articular facets and inter-facet distances (L1-L5) using a Microscribe apparatus.
• Comparative analysis of 120 normal male spines versus 115 male spines with bilateral L5 spondylolysis (SP).
• Statistical analysis using Analysis of Variance (ANOVA) to compare morphological differences.

Main Results:

• Individuals with SP exhibited significantly wider inter-facet widths and shorter inter-facet heights at L4.
• L4 vertebrae in SP individuals showed significantly shorter and narrower articular facets compared to controls.
• A specific L4 inferior inter-facet width to L5 superior inter-facet width ratio was observed in SP cases.
• Flatter right inferior articular facets were a consistent finding across all lumbar vertebrae in individuals with SP.

Conclusions:

• Specific morphological characteristics of the L4 vertebra are associated with an increased risk of developing spondylolysis (SP) at L5.
• Individuals with L4 vertebral anomalies, such as wider inter-facet dimensions and flatter facets, are predisposed to fatigue fractures.
• These findings highlight the importance of vertebral architecture in the pathogenesis of spondylolysis.