Correct combination
Case 102
【Discussion】
Vertebral endplate is completed from epiphysis at age of around 18 or greater (1 - 7). It is composed of cartilage component and osseous component with hematopoietic bone marrow. Vascular sinusoids in the bone marrow are adjacent to the endplate. Annual fibers of disc insert the endplate. The cartilage of endplate functions remodeling of the bone and the small vessels of endplate exchange water, minerals and nutrient between the vertebral bone marrow and disc. Calcification of endplate cartilage result in impeding remodeling and this circulation system.
Modic classification of endplate change on MRI is widely accepted between orthopedists and radiologists (Table 1). Namely, Modic type I represent low signal intensity on T1WI and high signal intensity on T2WI, implying bone marrow edema or inflammation (8, 9). Modic type I is reported to be caused by the link of injury, inflammation and/or infection, inducing chronic lumbago (8, 9). In Case 1 and Case 6, this active pattern was found (Figs 1 and 6, yellow arrow).
Modic type II represent high signal intensity on T1WI and high signal intensity on T2WI, implying fatty change of bone marrow as a result of bone marrow ischemia (8, 9). In Case 2 and Case 3 showing this pattern, fat suppression MRI shows fat suppression effect on MRI in Case 2 but not in Case 3 which probably bloody component. Then, Modic type II is considered to be caused not only by fatty replacement but also hemorrhage occupy.
Modic type III represent low signal intensity on T1WI and low signal intensity on T2WI, implying subchondral sclerosis of fibrosis and/or calcification (8, 9), as a result of endplate damages, which impede the nutrient circulation to the disc and bone remodeling. In Case 1 and Case 6, this pattern was found (Figs 1 and 6, red arrow). In clinical reality as shown on Figs 1 and 6, lumbar endplate changes often occur associated with various Modic types.
Schmorl nodule is referred as intravertebral disc herniation, which is formed by disk protrusion to the vertebral body through the vertebral endplate. The endplate is often destructed at the site of Schmorl nodule, indicating contact to bone marrow and inducing inflammation. Silent Schmorl nodules are common and usually asymptomatic, while acute Schmorl nodules which are symptomatic such as lumbago, are uncommon. It is believed that localized weakness of endplate is caused by apoptosis of cartilage cells due to aging (or trauma), protrudes to vertebral body via endplate, leading to Schmorl nodule (8, 9). Meanwhile, as the ages advance, the more often the disk becomes flat and inflexible, inducing osteosclerosis of endplate for supporting body weight (1, 3, 4). The vice cycle begins, the small vessels within the endplate become occluded due to osteosclerosis, which impede the exchange of vital nutrients between endplate and disk. In Case 5, MRI showed fluid retention surrounding Schmorl nodule, suspicious of active inflammation.
【Summary】
We present six cases with vertebral endplate disorder, Modic type I, II and III, Schmorl nodule and compression fracture. We should keep in mind that signal patterns; Modic I, low signal intensity on T1WI and high signal intensity on T2WI, implying bone marrow edema or inflammation; Modic type II, high signal intensity on T1WI and high signal intensity on T2WI, implying fatty change of bone marrow or hemorrhage; Modic type III, low signal intensity on T1WI and low signal intensity on T2WI, implying subchondral sclerosis of fibrosis and/or calcification. Further, vertebral endplate composes of cartilage component and osseous component and functions remodeling of the bone and the small vessels of endplate exchange water, minerals and nutrient between the vertebral bone marrow and disc. Scmorl nodule and subchondral osteosclerosis are caused by trauma, inflammation and/or infection and they possibly impede these functions.
【References】
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