Aging of the elastic and collagen fibers in the human cervical interspinous ligaments.

BACKGROUND CONTEXT: The ligaments consist of collagen bands intermingled with elastic fibers that support hundreds of pounds of stress per square inch. In the spine the basic functional unit comprises vertebrae, intervertebral disc and ligament tissues. The interspinous ligaments with the function of limiting the spine flexion are exposed to a traumatic and degenerative process that promotes pain or instability. It has been shown that aging induces structural changes to capsular, fascial and ligamentous structures, mainly to the elastic and collagen fibers. However, the relative changes with age in elastic and collagen fibers have not been quantified. PURPOSE: Examine the changes in the arrangement and amount of the elastic and collagen fibers of the human cervical interspinous ligament and attempt to correlate them with age. STUDY DESIGN/SETTING: Histomorphometric analysis of ligament samples harvested during surgery. PATIENT SAMPLE: We studied the dorsal portion of this ligament from 17 patients aged 16 to 69 years. OUTCOME MEASURES: Fraction of collagen and elastic fibers with linear regression analysis correlating fraction versus age. METHODS: The elastic and collagen fibers were identified by selective staining methods, and a blinded investigator using an image analysis system performed the histomorphometry. RESULTS: There is an age-related progressive increase in collagen and mature and elaunin elastic fibers responsible to elasticity. However, these elastic fibers showed structural degenerative changes with aging. Furthermore, there is an age-related decrease of oxytalan elastic fibers responsible to resistance. CONCLUSIONS: The aged interspinous ligament showed loss of elasticity that could alter the flexion limiting of the vertebral column.