A Morphometric Study of the Lumbar Interspinous Space in 100 Stanford University Medical Center Patients

OBJECTIVE: With the increased use of interspinous spacers in the treatment of lumbar stenosis, knowledge of the geometry of the interspinous space is important. To prevent dislodgment of an interspinous spacer, the accurate depth and width of the interspinous space needs to be established to facilitate the best intraoperative selection of correct spacer size. METHODS: To determine the depth and width of the interspinous space, two methods are available which utilize plain film and magnetic resonance imaging (MRI). Data analysis of the interspinous depth and width was undertaken in 100 patients. RESULTS: The standard deviations were variable, since skin thickness (zone 1) was altered by sex and age. The difference in the zone 1 distance between adjacent interspinous processes varied according to gender (p0.05). For zones 6 and 7, the interspinous distances at the narrowest and widest points, respectively, were found to decrease with the aging process, but the decrease was not statistically significant. There were no differences with regard to gender (p>0.05). CONCLUSION: This study provides additional information on the interspinous space. This statistical data are valuable for use in the design of interspinous spacers.

Anatomy of lumbar interspinous ligaments: attachment, thickness, fibre orientation and biomechanical importance / Anatomía de los ligamentos interespinosos lumbares: inserción, grosor, orientación de las fibras e importancia biomecánica

Literature related to the study of interspinous ligament in the lumbar region is sparse. Very few studies have elucidated the fibre orientation of this ligament at different lumbar levels. Male (19) and female (6) cadavers were dissected to expose the interspinous ligaments beneath all the lumbar vertebrae. Fibre attachments and directions were observed at all lumbar interspinous spaces. Thicknesses of the ligaments were measured at all levels. Interspinous ligament fibres were found to be oriented differently in the lumbar inter-spinous spaces. In the upper spaces the fibres were more horizontal. In the spaces beneath L3 and L4, fibres were curved and extended postero-superiorly. Fibres were thicker in the ligaments at the lower spaces in comparison to the upper ones. The mean thicknesses presented as: Upper (0.22 mm); Middle (0.37 mm) and L5-S1 (0.72 mm). Ligaments in the females were slightly thinner in comparison to the males. Fibres of inter-spinous ligaments were also found to attach to the inner aspects of the supraspinous ligament. Ligaments at L5-S1 junction were relatively vertical and stronger. None of the specimen demonstrated absence or cavitations of these ligaments except in a case with bi-laminar ligament at the L3-L4 level. The anatomy of the interspinous ligaments points to their probable role in graded restricting of acute flexion at the lumbar spine.

La literatura relacionada con el estudio del ligamento interespinoso en la región lumbar es escasa. Pocos estudios han permitido comprender la orientación de las fibras de este ligamento en diferentes niveles lumbares. Fueron disecados cadáveres de 19 hombres 6 y mujeres para exponer los ligamentos interespinosos debajo de las vértebras lumbares. La unión de las fibras y su dirección se observó en todos los espacios interespinosos lumbares. El grosor de los ligamentos se midieron en todos los niveles. Las fibras del ligamento interespinoso se encontró orientada de manera diferente en los espacios lumbares interespinosos. En los dos espacios superiores las fibras eran más horizontales. En los dos espacios centrales (por debajo de L3 y L4) las fibras se curvaban y extendían postero-superiormente. Las fibras eran más gruesas en los ligamentos de los espacios inferiores en comparación con los superiores. La media de espesor presentada por región fue: Alta (0,22 mm), Medio (0,37 mm) y L5-S1 (0,72 mm). Los ligamentos en mujeres fueron ligeramente más delgados. También se observó que las fibras de los ligamentos interespinosas se adhieren a las superficies internas del ligamento supraespinoso. La unión de los ligamentos en L5-S1 eran relativamente más verticales y robustas. En ningún caso se observó ausencia o cavitaciones de los ligamentos, excepto en un caso con ligamento bilaminar a nivel L3-L4. La anatomía de los ligamentos interespinosos señala su probable rol en la restricción de la flexión aguda en la columna lumbar.