The Distribution And Turnover Of Modic Changes Of Lumbar Endplate In Patients Suffering From Low Back Pain Or Radiculopathy

BackgroundAlthough low back pain is seen very often, the cause of it is rather complicated that is closely related with the degenerative changes of spine. Along with the deepening of MRI application and study on spine degenerative changes, Modic changes of lumbar endplate have gained more and more attention. DeRoos and Modic described Modic changes as: different types were categorized according to T1-weighted phase, and T2-weighted phase. Namely, type 0: normal, no Modic changes. Type I : endplate and adjacent bones on T1-weighted phase are low signals, while relatively normal endplate on T2-weighted phase is high signals. On histology, itshows edema which is related to cartilage endplate fracture and increased vascularization of subchondral bone marrow. Some think it is caused by micro fracture. Type II: the signals of relatively normal marrow on T1-weighted phase increase especially, as well as on T2-weighted phase. On histology, it means fatty degeneration of bone marrow, which is considered as avascular necrosis of bone marrow. Type III : the signals on both T1-weighted phase and T2-weighted phase decrease. Such changes are correspondent to plain film compact bone sclerosis, because marrow fat has been replaced by sclerosing bone.The exact cause of Modic changes has not become clear yet. The "internal disc disruption, IDD" theory proposes that repeated disc traumas could give birth to internal inflammatory chemicals of nucleus pulposus. These poisonous chemicals could induce local inflammatory response through diffusion of vertebral endplates, which results in the decreased signal on T1-weighted phase and increased signal on T2-weighted phase on MRI , and causes pain.Other scholars think that the major cause of Modic changes is micro endplate injury due to repeated mechanical load. Vertebral bone and cartilage endplate under the samepressure as disc, the region neighboring the disc is usually weaker than the disc itself and prone to micro fracture. If that happens recently, it may show low T1 signal and high T2 signal on MRI. If the disc lost its shock absorbing function because of dehydration, this phenomenon will be exacerbated. Natarajan used finite element models to analyze different assumptions of disc degeneration, and found that mechanical injury of vertebral segments always started with the separation of cartilage endplate from osteoarthritis endplate. This theory is in line with the early micro study of Vernon-Roberts. The latter found since middle-age, cracks and tears appeared near endplate and parallel to it. Meanwhile, as proved by Tanaka' s autopsy research, endplates first separated from centrum, then the disc and attached annulus fibrosus slipped together. Among the 120 cases of disc herniation, about half of the herniated tissues contained endplate fragments.Foreign studies indicated that 20-50% of people had Modic changes; the older, the more. But the samples were relatively small and the alternation of different types of Modic changes was not clear.ObjectiveTo evaluate the distribution of Modic changes of lumbar endplate in patients suffering from low back pain or radiculopathy and analyze their turnover. MethodsFrom January 2005 to October 2006, 2315 cases of patients suffering from low back pain were examined by X film and MRI scan. According to the results of MRI scan, the feature of distribution of Modic changes of lumbar endplate was analyzed retrospectively. The patients with Modic changes were treated with operative and non-operative ways respectively, being followed up from 6 to 25 months, and their turnover was analyzed. ResultsAmong 11575 intervertebral discs of 2315 cases of patients, 534 (23. 1%) patients and 606 (5. 24%) intervertebral discs were involved with Modic changes. Among them, 104 (4. 5%) cases and 127 (1. 1%) discs were type I ; 420 (18. 2%) cases and 479 (4. 14%) discs were type II; 10 (0.45%) cases and 11 (0.1%) discs were type III. According to the segment, L5-S1:296 (2.56%), L4-5:201 (1.74%), L3-4:65 (0.56%), L2-3:30 (0.26%), L1-2:14 (0. 12%). Modic changes occurred similar in female and male.,and were distributed mainly in the range of 40 to 60 years old. During the 6 to 25 months of follow up, there were 34 Modic I patients, 63 Modic II patients and 7 Modic III patients with complete medical records. Among the 12 operative ModicI patients, 1 returned to normal, 7 remained Modic I, and 4 changed to Modic II; among the 22 non-operative Modic I patients, 21 remained Modic I , and 1 changed to Modic II. Among the 21 operative Modic II patients, 3 returned to normal, 17 remained Modic II, and 1 changed to Modic III; among the 42 non-operative Modic II patients, 1 returned to normal, 40 remained Modic II, and 1 changed to Modic III. Among both operative and non-operative Modic III patients, they all remained Modic III. ConclusionsModic changes of lumbar endplate mainly occurred in L5S1 and L45 segment, and most of them were type II, followed by typeI and type III respectively. Some cases of type I can change to type II, while fewer changes happened to type II, and type III basically remained the same. Operation can facilitate the changes from type I and type II to normal, as well as type I to type II.