Medical Student Drexel University College of Medicine, US
Introduction: The lumbar pars interarticularis is a key anatomic element of the posterior lumbar vertebrae. Its definition varies, but it generally defines a segment of the lateral lamina spanning between the superior and inferior facet joints. Defects in the pars can be congenital, traumatic, degenerative, pathologic, or iatrogenic.
Methods: We propose dividing the pars into three separate zones. Each with separate destabilizing effects and unique structural disconnections when defective. This classification will hopefully lead to a better understanding, management, and prevention of pars defects, regardless of cause. Lastly, this conceptualization will help neurosurgeons in the management of pars defects and help define the safe extent of bony removal during spine surgery.
Results: We define Zone 1 of the pars as the superior segment spanning from the lateral lamina to the superomedial interlaminar space. Defects here disconnect the inferior articular process from the remaining lamina and may be due to extensive foraminotomy. Zone 2 describes the middle pars that is continuous with the lamina and spinous process. Defects here are mostly clinically significant in the setting of laminotomy or hemilaminotomy, and when defective disconnects both facets. Zone 3 describes the inferior segment spanning to the inferioromedial interlaminar space. Defects in this zone disconnect the superior articular process from the remaining lamina.
Conclusion : Division of the pars interarticularis into distinct structural and functional zones will allow further characterization and understanding of pathologies of this little discussed anatomical feature.
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