The rate of subsidence for lumbar fusion surgery is variable from 7- 89%. Subsidance can affect the outcome of surgery by compramising alignment, foraminal height and stability. Modic changes have been shown to affect the stiffness and strength of the vertebral end plate and shown to affect both fusion rates and clinical outcome. Ongoing laboratory investigations into the material properties of the degenerate lumbar spine show modic changes affect the end plate and trabecular bone mechanics. This study aims to bridge this basic science research into clinical practice. A retrospective analysis of all patients in two tertiary spinal centres who have undergone lumbar interbody fusion with the implantation of a ‘cage’ over the past 6 years were analysed by two independent spinal surgeons. Pre-operative MRI findings were correlated with post-operative interbody cage subsidence after 1 year.Background
Methods
The vertebral endplate (VEP) is characterised as a bilayer of cartilage and bone, acting as a boundary between the disc and the vertebra. The disc being the largest avascular tissue in the body, relies primarily on the nutritional pathways from the vascular network in the adjacent VEP. Disruption of this nutrient supply has been identified as a major contributor to disc degeneration, yet the 3D topology of the network is poorly understood. The aim of this work is the characterisation of this vascular network to further understand the physiology of the vascular network and the correlation between disc degeneration and nutrient supply. Caudal and cranial VEP sections were sampled from lumbar ovine spines and imaged using high-resolution micro-computed tomography (micro-CT) at 4.92 µm pixel size. The diameter, length, orientation and depth from the VEP surface were measured for individual canals using 3D canal centreline models using ScanIP. The results showed higher concentration of canals in the central regions of the VEP and in caudal VEP to the disc. Large transverse canals were identified running parallel to the VEP surface connected to both the disc and the vertebra, and depth-dependence of the length and diameter of the canals was recorded.Aim of Study and Background
Methods and Results
