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Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_4 | Pages 3 - 3
1 Jan 2013
Stefanakis M Luo J Truss A Finan C Dolan P Adams M
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Introduction

Delamination of the annulus fibrosus is an early feature of disc degeneration, and it allows individual lamellae to collapse into the nucleus, or to bulge radially outwards. We hypothesise that delamination is driven by high gradients of compressive stress in the annulus.

Methods

102 thoracolumbar motion segments (T8-9 to L5-S1) were dissected from 42 cadavers aged 19–92 yrs. Each specimen was subjected to 1 kN compression, while intradiscal compressive stresses were measured by pulling a pressure transducer along the disc's mid-sagittal diameter. Stress gradients were measured, in the anterior and posterior annulus, as the average rate of increase in compressive stress (MPa/mm) between the nucleus and the region of maximum stress in the annulus. Average nucleus pressure was also recorded. Disc degeneration was assessed macroscopically on a scale of 1–4.