The MRI Characterization Of Lumbar Spine Lesions In The Acute Phase Of Ankylosing Spondylitis

Objective:To divide the T12-S1 segment into upper,middle,and lower vertebral units based on the biomechanical characteristics of spinal motion,and to analyze the typical MRI imaging manifestations of lumbar spine lesions in the acute phase of AS and combine them with the Berlin score,to further investigate the distribution pattern,extent of involvement and lesion characteristics of lumbar spine lesions in the acute phase of AS.Methods:According to the inclusion and exclusion criteria of this study,70 patients with a diagnosis of AS admitted to the rheumatology department of our hospital from 2019 to2022 were retrospectively analyzed.All patients underwent lumbar MRI(T1WI,T2 WI,STIR sequence,scan range T12-S1)and laboratory tests(HLA-B27).The T12-S1 segment was divided into upper,middle,and lower vertebral units,where the vertebral unit(VU)was defined as the corresponding segmental disc and its two adjacent hemivertebrae bodies.On the picture archiving and communication system(PACS),the MRI images of the lumbar spine of 70 patients with AS were analyzed by two radiologists with extensive experience in diagnostic imaging of the osteoarticular system using a double-blind method,including the imaging manifestations(angiitis,discitis,and synovial arthritis,etc.)and the distribution characteristics of the corresponding lesions.The analysis included the distribution characteristics and extent of involvement of the corresponding lesions and was determined by consultation between the two in case of disagreement.The Berlin score of the affected vertebral units was evaluated to investigate the differences in Berlin scores between different segmental vertebral units.Spearman’s correlation analysis was used to analyze the correlation between age,disease duration,HLA-B27,and Berlin score in patients enrolled in the acute phase of AS.Results:(1)Seventy patients with acute lumbar spine lesions in AS were enrolled,57 males and 13 females,aged 19 to 88 years,with a mean age of 47.8 ± 14.5 years.64 were HLA-B27-positive and 6 were negative.The MRI scans of the lumbar spine involved a total of 490 vertebral bodies and 420 vertebral units.(2)Among the 70 patients with AS,there were 52 cases of vertebral hornitos,with a positive rate of 74.3%,involving a total of 290 vertebral bodies,of which 182 were involved in the anterior horn only,64 in the posterior horn only,and 44 in the anterior and posterior horn of the vertebral body at the same time;there were 18 cases of intervertebral discitis,with a positive rate of 25.7%,involving a total of 25 intervertebral discs,of which 4 were involved in the central part of the disc,7 were involved in the peripheral part of the disc,and 14 were diffusely involved,with MRI showing varying degrees of narrowing of the intervertebral space,the abnormal high signal in the affected discs on T2 fat suppression images,and hairy edges and Modic degeneration of the adjacent vertebral bodies.(3)Half or more of the vertebral units in the different segmental unit groups had a Berlin score of 1;the overall distribution of Berlin scores in the different segmental units was statistically different(P=0.002),and the involvement of vertebral units with a Berlin score of 2 to 3 was mainly found in the middle and lower segments.The Bonferroni method showed that the lower vertebral units were more likely to have a Berlin score of 3 than the upper and middle vertebral units,and the difference was statistically significant(P < 0.05);less than 10% of the vertebral units in different segments involved the intervertebral disc,and there was no statistical difference in the overall distribution of intervertebral disc involvement in different segments(P = 0.743).(4)There was no statistical correlation between age,disease duration,and Berlin score in the 70 patients with acute lumbar spine lesions in AS(P >0.05);there was a weak correlation between HLA-B27 and Berlin score(P = 0.045,correlation coefficient 0.240).Conclusions:1.Acute lumbar spine lesions in AS are mostly manifested as vertebral hornitos and discitis on MRI and are easily combined with vertebral micro arthritis to show a mixture of two forms of inflammation,and the lesions are characterized by multi-vertebral unit involvement and multifocal distribution.2.The lumbar spine changes in the acute phase of AS tend to involve the vertebral horn,of which the anterior horn of the vertebral body is most commonly involved,and intervertebral discitis can be broadly divided into central,peripheral,and diffuse types according to the site of involvement,of which diffuse disc involvement is most common.3.The overall distribution of the Berlin score differed among the vertebral units in different segments,in which the involvement of vertebral units with a Berlin score of 2-3was mainly concentrated in the middle and lower segments,and the incidence of vertebral units with a Berlin score of 3 was higher in the lower segment compared with the middle segment,suggesting that severe lumbar spine disease changes in the acute phase of AS are likely to involve the lower segment vertebral units(L4-S1).4.There was a weak correlation between HLA-B27 and spinal Berlin score,and no correlation with age and disease duration in AS patients.