A morphological study of the fibrous capsule of the human lumbar facet joint

Study Design. Macroscopic and microscopic investigations of the human lumbar facet joint capsule were undertaken. Objective. To describe the morphologic characteristics of the fibrous capsule of the lumbar facet joints. Summary of Background Data. Previous biomechanical and neurophysiologic studies by the authors have shown that the lumbar facet joint capsule may be a source of low back pain. Methods. Macroscopic investigation was performed on the facet joint capsules dissected from five fresh adult cadavers. For microscopic studies, facet joint capsules obtained from cadaver dissection and spinal surgeries were stained by the hematoxylin and eosin method and the Elastica-Van Gieson method. Results. The outer layer of the fibrous capsule is a dense regular connective tissue that is composed of parallel bundles of collagenous fibers. The inner layer of the fibrous capsule consists of bundles of elastic fibers, similar to the ligamentum flavum. In the superior and middle part of the joint, the fibers run in the medial to lateral direction, crossing over the joint gap. In the inferior part of the joint, the fibers are relatively long and run in a superior-medial to inferior-lateral direction, covering the inferior articular recess. They are thicker than the layer in the superior and middle parts of the joint. Conclusions. Anatomical and histologic features of the lumbar facet joint capsule are different between its outer layer and inner layer. This complex of morphologic factors can affect the biomechanics and neurophysiology of the lumbar facet joint.