16ème Réunion Annuelle du GIEDA INTER RACHIS
12 et 13 décembre 2003
Centre Français du Commerce Extérieur
10 Avenue d’Iéna – 75016 PARIS
Nom :
Campana
Prénom :
Sophie
e.mail : sophie @this.is
TITRE : Human intervertebral disc imaging and mechanical behaviour
AUTEURS : S. Campana1,2, J. A. de Guise1, L. Rillardon2,
E. Charpail2, P. Després1, D. Mitton2, W.
Skalli2
1Laboratoire de Recherche en
Imagerie et Orthopédie, ETS-CHUM, Montréal, Québec, Canada
2Laboratoire de Biomécanique,
ENSAM-CNRS, Paris, France
Texte : INTRODUCTION – Low back pain often originates in
mechanical disorders, such as osteoarthritis or degenerative disc disease. Intervertebral disc (IVD) has no apparent density on plain
radiographs ; therefore, space narrowing and vacuum phenomenon are among the
few clinical indications of disc degeneration. The use of a new low-dose
radiological system based on a gaseous micro-pattern detector technology,
combined with dual-energy imaging, can provide an innovative way to assess disc
diseases and their influence on the mechanical properties. This paper
investigates how analysis of low-dose radiological imaging used in dual-energy
mode, MRI and discograms can contribute to early
diagnosis of IVDs degeneration and appraisal of their
mechanical behaviour. METHODS – Twenty-two fresh lumbar discs (14 L1-L2 and 8
L4-L5, aged 55 to 93) were imaged and mechanically tested within 72 hours after
harvesting. Low-dose radiographs were acquired at several energies, and MRI
sequences (T1W and T2W) as well as discographies were obtained.
Flexion-extension, lateral bending and torsion 10 N.m
moments were applied to the associated functional spinal units (FSU composed of
two vertebrae and intervertebral soft tissue), first
intact and second after posterior arch resection, for range of motion (ROM)
recording. Compression (400N) and creep (10 min) were then performed on each
FSU. Finally, the discs were dissected in their transverse plane for
macroscopic inspection. They were graded according to their degenerative level
using each imaging modality. Osteophytes, Schmorl’s nodes, herniations,
calcifications, frontal dissymmetry, loss of disc height, discographic
tears or ligamentous ossification were recorded as
anomalies. RESULTS AND DISCUSSION – Dual-energy reconstructions were completed
on 10 intervertebral discs, in order to separate bone
and soft tissue contributions ; the average atomic number of disc space could
be extracted. The resulting quantitative chemical information and
contrast-enhanced images allowed a better characterization of disc features and
abnormalities, especially anterior and posterior outlines, density variations
within the disc space, as well as some herniations
when present ; MRI was used to validate the findings. Fused anterior osteophytes lead to an overall loss of mobility ; internal
calcifications reduced the ROM in torsion only. IVDs
with severe annular tears, as revealed by discograms,
exhibited larger ROMs as well as higher compressive hysteresis
and strains than discs with few tears. Dehydrated discs, characterized by a
loss of signal in MRI, showed weakened viscoelastic
properties in creep. CONCLUSION – Dual-energy detected outlines and anomalies
indistinguishable in plain radiographs. Coupled to MRI and discography, it
revealed some of the multi-factorial aspects involved in the mechanical
behaviour of the IVD.
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