First sacral nerve and anterior longitudinal ligament anatomy: clinical applications during sacrocolpopexy.

BACKGROUND: The recommended location of graft attachment during sacrocolpopexy is at or below the sacral promontory on the anterior surface of the first sacral vertebra. Graft fixation below the sacral promontory may potentially involve the first sacral nerve. OBJECTIVE: The objectives of this study were to examine the anatomy of the right first sacral nerve relative to the midpoint of the sacral promontory and to evaluate the thickness and ultrastructural composition of the anterior longitudinal ligament at the sacral promontory level. STUDY DESIGN: Anatomic relationships were examined in 18 female cadavers (8 unembalmed and 10 embalmed). The midpoint of the sacral promontory was used as reference for all measurements. The most medial and superior point on the ventral surface of the first sacral foramen was used as a marker for the closest point at which the first sacral nerve could emerge. Distances from midpoint of sacral promontory and the midsacrum to the most medial and superior point of the first sacral foramen were recorded. The right first sacral nerve was dissected and its relationship to the presacral space was noted. The anterior longitudinal ligament thickness was examined at the sacral promontory level in the midsagittal plane. The ultrastructural composition of the ligament was evaluated using transmission electron microscopy. Height of fifth lumbar to first sacral disc was also recorded. Descriptive statistics were used for data analyses. RESULTS: Median age of specimens was 78 years and median body mass index was 20.1 kg/m2. Median vertical distance from midpoint of sacral promontory to the level of the most medial and superior point of the first sacral foramen was 26 (range 22-37) mm. Median horizontal distance from the midsacrum to the first sacral foramen was 19 (range 13-23) mm. In all specimens, the first sacral nerve was located just behind the layer of parietal fascia covering the piriformis muscle, and thus, outside the presacral space. Median anterior longitudinal ligament thickness at the sacral promontory level was 1.9 (range 1.2-2.5) mm. Median fifth lumbar to first sacral disc height was 16 (8.3-17) mm. CONCLUSION: Awareness of the first sacral nerve position, approximately 2.5 cm below the midpoint of the sacral promontory and 2 cm to the right of midline, should help anticipate and avoid somatic nerve injury during sacrocolpopexy. Knowledge of the approximate 2-mm thickness of the anterior longitudinal ligament should help reduce risk of discitis and osteomyelitis, especially when graft is affixed above the level of the sacral promontory.

Mechanoreceptors in intervertebral discs. Morphology, distribution, and neuropeptides.

STUDY DESIGN: The present study investigated the occurrence and morphology of mechanoreceptors in human and bovine intervertebral discs and longitudinal ligaments. OBJECTIVE: To determine the type and frequency of mechanoreceptors present in intervertebral discs and anterior longitudinal ligaments in two patient groups, those with low back pain and those with scoliosis. Bovine coccygeal discs were examined. SUMMARY OF BACKGROUND DATA: Nerves have been described in intervertebral tissues, but there is little information on the endings of these nerves and their receptors, stimulation of which can cause a nerve impulse. METHODS: The presence of mechanoreceptors were investigated by immunolocalization of nerves and neuropeptides. By examining sequential sections, the frequency of receptors was assessed. RESULTS: Immunoreactivity to neural antigens showed mechanoreceptors in the anulus fibrosus and longitudinal ligaments of bovine and human specimens. Their morphology resembled Pacinian corpuscles, Ruffini endings, and, most frequently, Golgi tendon organs. They were found in 50% of discs investigated from patients with low back pain and in 15% of those with scoliosis. CONCLUSIONS: Mechanoreceptors were found in the outer 2-3 lamellae of the human intervertebral disc and anterior longitudinal ligament. Physiologic studies in other tissues indicate that these provide the individual with sensation of posture and movement, and in the case of Golgi tendon organs, of nociception. In addition to providing proprioception, mechanoreceptors are thought to have roles in maintaining muscle tone and reflexes. Their presence in the intervertebral disc and longitudinal ligament can have physiologic and clinical implications.

Topography and distribution of nerve fibers in the posterior longitudinal ligament of the rat: an immunocytochemical and electron-microscopical study.

The distribution and immunocytochemical characterization of nerve fibers and their terminals in the posterior longitudinal ligament of the rat lumbar vertebral column was studied in whole-mount preparations and serial semithin and ultrathin sections. Differences in the localization, distribution pattern and density of peptidergic and catecholaminergic nerve fibers were found in the vertebral and intervertebral regions of the posterior longitudinal ligament. For immunocytochemistry, free floating specimens were incubated with primary antibodies against protein gene product 9.5, substance P, calcitonin gene-related peptide, dopamine-beta-hydroxylase, vasoactive intestinal polypeptide and neuropeptide Y together with the avidin-biotin-peroxidase method. In whole-mount preparations, the neural marker protein gene product 9.5 is immunostained in all unmyelinated nerve fibers in the posterior longitudinal ligament, thus giving a panoramic view of the nerve fiber plexus. The most striking nerve fiber plexus is localized in the intervertebral region. In this region, the posterior longitudinal ligament is rich in capillaries that form a dense plexus within its ventral part and extend to the outer layer of the annulus fibrosus. The peptidergic and catecholaminergic innervation of the posterior longitudinal ligament is discussed in the context of pain syndromes related to the vertebral column and degenerative lumbar spine diseases.