Temperature dependence of the tensile properties of interspinous ligaments of sheep.

The dependence on temperature of the tensile properties of interspinous ligaments was examined to establish whether in vitro studies at room temperature reflect behaviour in vivo at higher temperatures. Specimens consisting of sheep interspinous ligaments attached to their adjacent spinous processes were mounted in specially designed holding devices in an Instron material testing machine; the specimens were immersed in saline and tests were conducted at four temperatures between 19 degrees C and 46 degrees C. Control tests demonstrated the repeated testing to a load up to half the fail load did not affect the response of the ligaments. No difference was found in the mechanical characteristics of the ligaments at the different temperatures but the ligaments expanded at the higher temperatures, resulting in an increase in extension over which they demonstrated an initial low stiffness characteristic. Thus although temperature did not directly affect the response of the ligaments to load, the thermal expansion of the soft tissue elements may have implications for the function and mobility of spinal joints if measured at room rather than body temperature.