Facet joint asymmetry as a radiologic feature of lumbar intervertebral disc herniation in children and adolescents

STUDY DESIGN: This study compared the incidence of facet joint asymmetry between adult and juvenile patients with lumbar intervertebral disc herniation. OBJECTIVES: To determine the different distribution of the facet joint asymmetry between the adult and juvenile patients. SUMMARY OF BACKGROUND DATA: As early as 1967, it was suggested that asymmetry of the facet joints is correlated with the development of disc herniation. There have been numerous arguments for and against Farfan's hypothesis, however, most studies were carried out on adult patients, and this hypothesis has not been verified in juvenile patients. METHODS: The study group consisted of 29 levels of 25 patients aged 12-20 years (juvenile group) and 50 levels of 33 patients aged 30-49 years (adult group) who underwent posterior discectomy. The shape of facet joints, the facet joint angle, and the moment arm angle and length were measured for each facet joint using computed tomography. Facet joint asymmetry was defined as the difference in facet joint shape or a difference of more than 10 degrees in facet joint angles between the right and left sides. The incidence of facet joint asymmetry and the relationships among the facet joint asymmetry and the location, type of disc herniation, and disc degeneration were examined in juvenile and adult groups. RESULTS: The overall incidence of facet joint asymmetry was significantly higher in the juvenile group (12 levels, 41%) than in the adult group (four levels, 8%; P < 0.01). There were no significant relationships among the facet joint asymmetry, the location, type of disc herniation, and disc degeneration. CONCLUSIONS: This study revealed that the frequency of facet joint asymmetry in the juvenile group was five times higher than that in the adult group. This result indicates that facet joint asymmetry is a radiologic feature of lumbar intervertebral disc herniation in children and adolescents.