MORPHOLOGIC ANALYSIS OF THE FACET JOINT IN THE IMMATURE LUMBOSACRAL SPINE WITH SPECIAL REFERENCE TO SPONDYLOLYSIS

Study Design. Morphological analysis was performed of the facet joint of the normal and spondylolytic lumbosacral spine in children and adol escents. Objectives. This study was performed to estimate the influenc e of spondylolysis on growth of the neural arch of the lumbosacral spi ne. Summary of Background Data. The development of the facet joint and its relation to spondylolysis have not been documented in the literat ure. Methods. The dimension and orientation of the facet joint at L5/S were measured on radiographs and computed tomography scans from 144 b oys without pars defects and 104 boys with pars defects. The latter gr oup was further investigated according to the stage of pars defects. P atients in both groups were between 9 and 18 years of age. Results. Gr owth of the facet joint in the sagittal and transverse directions and the increase of the transverse angle were remarkable up to approximate ly 13 years of age. Concavity of the facet joints also progressed in c hildren of the same age. The growth of the facet joint in patients wit h spondylolysis was significantly retarded as the pars defects advance d from the progressive to the terminal stage. The joint surface was mo re coronal in orientation and flatter in shape compared with controls. Conclusions. The present results suggest that pars defects occurring in children disturb or retard the growth of the facet joint and that t he morphological characteristics of the joint surfaces in patients wit h spondylolysis are the consequence of these defects.