Object: Degenerative changes of the interspinous ligaments (ISLs) have generally been ignored in previous studies. Factor-related causes, the effects that these changes have on other structures within the spinal functional unit, and their relation to kinematic changes in the spine are lacking. In this study, the authors evaluated the reliability of a proposed MR imaging grading system of ISL degeneration (ISLD). They also investigated the relationship between ISLD and aging, disc/facet joint degeneration, and lumbar segmental motion.
Methods: The authors studied 256 lumbar motion segments from L-2 to S-1 in 64 patients (35 men and 29 women) with a mean age of 46.08 years (range 23–85 years). An MR imaging–based grading system for ISLD was developed and ranged from Grade A (mild) to Grade D (severe). The reliability was tested, and the correlation of the grade with the severity of the disc and facet joint degeneration was examined. The segmental motion of each functional unit was measured using flexion/extension MR imaging, and their relationships with ISL grades were identified.
Results: Grade A was observed in 115 levels (44.9%), Grade B in 105 (41.0%), Grade C in 15 (5.9%), and Grade D in 21 levels (8.2%). The kappa coefficients for intraobserver and interobserver agreements were substantial to excellent (intraobserver [0.871] and interobserver [0.721–0.807]). Grade D was observed primarily in elderly patients. Segmental motion tended to decrease in the most severe grade, with a significant difference in angular mobility. As the severity of ISLD increased, the severity of disc/facet joint degeneration increased (p < 0.001 and p < 0.05, respectively).
Conclusions: The authors proposed a reliable and reproducible grading system that may be used to investigate spinal kinematics in association with ISLD. The authors' findings illustrated the distribution of ISLD grades. The most severe grade occurred primarily in elderly patients. Mobility decreased in the most severe grade; therefore, the stage of ISLD should be taken into consideration when evaluating spinal stability.