Thoracolumbar Spine Anatomy and Pathology - Facet Joint

L4 L5 Facet Joint and Foramen

Sagittal high power photograph of the L4-L5 facet joint and foramen

Sagittal high power photograph of the L4–L5 facet joint and foramen in a spine that had been positioned in extension in the intact cadaver and frozen in situ to maintain the undistorted soft tissue–bone relationships. The extension was done without any axial loading. The extension position induces a posterior sagittal rotation of L4 on L5. In addition, the slight obliquity of the facet joint induces a slight posterior translation of L4 on L5. The extension also causes the tip of the inferior articular process to come in contact with the pars interarticularis of L5 which also is in contact from inferiorly with the superior articular process (SAP) of S1. The joint capsule is elongated and severely compressed against the pars interarticularis. The degree of angulation is also apparent from the wedge–shaped opening of the superior joint space into which a richly vascularized meniscoid synovial tag of loose areolar is projecting. The ligamentum flavum joint capsule attaches broadly to the anterior surface of the SAP. It is pushed into the subpedicular notch and compresses and flattens the dorsal root ganglion posteriorly. Anterior to the ganglion the separate ventral roots are discernible.

Updated on: 11/05/18

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