Does the high-intensity zone (HIZ) of lumbar Intervertebral discs always represent an annular fissure?
OBJECTIVE
The aim of this study was to examine high-intensity zone (HIZ) characteristics on both T1- and T2-weighted sagittal magnetic resonance (MR) images, and to reveal their exact nature.


METHODS
Seventy-three patients with low back pain and HIZs (identified on T2-weighted images) were included. Patients, aged 25-80 years (mean 51), were divided into two groups: the 'single-HIZ' group exhibited HIZs only on T2-weighted images, while the 'dual-HIZ' group exhibited HIZs on both T2-weighted and T1-weighted images. Tissue corresponding to the HIZ was harvested from surgery for analysis.


RESULTS
Eighty-two discs were studied, from 39 patients with single HIZs, 30 with dual HIZs, and four with both in the posterior annulus. HIZ volume, volume ratio, and signal intensity on T2-weighted images from the dual-HIZ group were significantly greater. Surgery was able to successfully restore patients' ability in both groups, while conservative treatments were less effective for patients with dual HIZs. Histology revealed outer annular fissures invaded by granulation tissue in the single-HIZ group. In dual-HIZ discs, Von Kossa staining and CT scans showed more calcified or ossified lesions (94.1 vs. 0 %, P<0.001), and chemical analysis showed significantly higher calcium content.


CONCLUSIONS
HIZs on both T2- and T1-weighted images represent calcified tissue, possibly from a vertebral endplate. A new concept of dual HIZ should be defined.


CONCLUSIONS
• Conventional definition of an HIZ refers to T2-weighted images only. • Dual HIZs have greater HIZ volume, volume ratio, and signal intensity. • HIZs on both T2- and T1-weighted images represent calcified tissue. • Conservative treatments are less likely to be effective for patients with dual HIZs.
Department of Orthopaedics, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, No. 3, Qingchun Road East, Hangzhou, 310016, People's Republic of China.
Zhi
Z
Shan
Department of Orthopaedics, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, No. 3, Qingchun Road East, Hangzhou, 310016, People's Republic of China.
Huanhuan
H
Chen
Department of Orthopaedics, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, No. 3, Qingchun Road East, Hangzhou, 310016, People's Republic of China.
Junhui
J
Liu
Department of Orthopaedics, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, No. 3, Qingchun Road East, Hangzhou, 310016, People's Republic of China.
Hong
H
Ren
Department of Orthopaedics, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, No. 3, Qingchun Road East, Hangzhou, 310016, People's Republic of China.
Xuyang
X
Zhang
Department of Orthopaedics, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, No. 3, Qingchun Road East, Hangzhou, 310016, People's Republic of China. zhaodong68@hotmail.com.
Fengdong
F
Zhao
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002114:Calcinosis / Q000150:complications* / Q000000981:diagnostic imaging* / Q000473:pathology; D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000000981:diagnostic imaging / Q000473:pathology; D017116:Low Back Pain / Q000150:complications / Q000473:pathology; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging* / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011843:Radiculopathy / Q000150:complications
Annular fissure; Calcification; Intervertebral disc; MRI; Spine