Lumbosacral interspinous ligament rupture associated with acute intrinsic spinal muscle degeneration.

The objective of this study was to demonstrate lumbosacral interspinous ligament rupture, with or without related acute intrinsic spinal muscle degeneration. This study consisted of a prospective imaging analysis of consecutive 100 MRI studies in adult patients (mean age 56 years) presenting with low back pain. Alterations from the normal in the inter- and perispinal structures of the spine and perispinal soft tissues (e.g., spinal ligaments, perispinal muscles) were sought based upon studies on young volunteers without low back pain ( n=10; mean age 23 years). Compared with the group without low back pain, many index cases ( n=71, 71%) demonstrated hyperintensity (i.e., sprain or frank ligamentous rupture) of the interspinous ligament(s) on T2-weighted, fat-suppressed MRI studies at one (20 of 71, 28%) or multiple (51 of 71, 72%) levels. Associated intrinsic spinal muscle (e.g., interspinalis, multifidus muscles) degeneration was observed in a minority of cases overall ( n=7, 7%), but was only seen in association with cases also demonstrating interspinous ligament degeneration/rupture (7 of 71, 10%). Lumbosacral interspinous ligament sprain or frank rupture, as well as related acute-subacute autotraumatic intrinsic spinal muscle rupture/degeneration, may be overlooked by many observers if fat-suppressed, T2-weighted MRI is not acquired. These musculoligamentous alterations are on occasion the only abnormalities recognized on MRI of the lumbosacral spine and may theoretically be sources of low back morbidity that potentially may respond to specific therapy. Because this study was an observational one, based solely upon medical imaging, future research must focus upon the correlation of the relevance of these findings with an age-matched asymptomatic control group and longitudinal clinicoradiologic therapeutic trials.