Diffusion characteristics of human annulus fibrosus—a study documenting the dependence of annulus fibrosus on end plate for diffusion

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• 作者：J. Naresh-Babu ; MS ; FNB^a ; ^{nareshspine@yahoo.com" class="auth_mail" title="E-mail the corresponding author} ; G. Neelima ; MD^b ; Sk Reshma Begum ; MSc^a ; Voleti Siva-Leela ; MD^a
• 关键词：MRI ; Post-contrast ; Diffusion ; Annulus fibrosus ; Nutrition ; Endplate ; Gadodiamide ; Intervertebral disc ; Nucleus pulposus ; Vertebral body
• 刊名：The Spine Journal
• 出版年：2016
• 出版时间：August 2016
• 年：2016
• 卷：16
• 期：8
• 页码：1007-1014
• 全文大小：1254 K

文摘

Intervertebral disc being avascular depends on nutrition from either the end plate or the annulus fibrosus (AF). The role of the end plate on disc diffusion had been extensively studied. However, diffusion of human AF remains poorly understood because of the lack of reliable techniques to study AF in vivo and non-invasively. The present study for the first time evaluates the 24-hour diffusion characteristics of AF in radial, axial, and circumferential directions.

Purpose

The study aimed to document the 24-hour diffusion characteristics of human AF.

Study Design

This is an in vivo human serial post-contrast magnetic resonance image study.

Methods

Twenty-five discs from five healthy volunteers (age <20 years) were studied. Diffusion over 24 hours following intravenous gadodiamide injection (0.3 mmol/kg) was studied at 10 minutes, and at 2, 4, 6, 12, and 24 hours. Axial images of the cranial, middle, and caudal zones of the discs were obtained. The vertebral body and end plate signal intensities were measured in sagittal sections. Thirty-nine regions of interest (24 in AF, 15 in nucleus pulposus) in each disc were analyzed. The peak enhancement percentage (EP_max) and the time to attain EP_max (T_max) were calculated. Radial (outer vs. inner AF), axial (cranial vs. caudal vs. middle zone), and circumferential diffusions were analyzed. (The study received research grant from AOSpine India for US$6,000).

Results

Annulus fibrosus showed a biphasic pattern of diffusion with a characteristic “double peak.” Early peak was seen at 10 minutes (coinciding with T_max of the vertebral body) and delayed peak was seen at 6 hours (coinciding with T_max of the nucleus pulposus), and characteristically noted after T_max of the end plate (2 hours). The inner AF showed significant regional differences both at the early and delayed peaks, but the outer AF had no regional differences in the early peak. In axial direction, both outer and inner AF showed maximum enhancement percentage in the middle zone, followed by the caudal zone and least in the cranial zone.

Conclusions

Annulus fibrosus characteristically showed a “double-peak” pattern of diffusion. Both the peaks had different characteristics, confirming two different sources of nutrition. The initial peak was contributed by periannular vascularity and the delayed one via the end plate from the vertebral body. The fact that even AF depends on the end plate for nutrition helps us better understand the complex nutritional pathways of intervertebral discs.