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Nomenclature and Classification of lumbar disc pathology.4 January at 23:39 from atlas
Nomenclature and Classification of lumbar disc pathology.Share4 January at 23:12 from atlas
In 1995, a multi-disciplinary task force from the North American Spine Society (NASS) addressed deficiencies in standardisation and current practice of the language defining conditions of the lumbar disc, and was published as a work of NASS and the American Academy of Orthopaedic Surgeons(AAOS).( David F. Fardon ,Clinical Task Force and Pierre C. Milette,Chairperson ,Imaging Task Force), the Combined Task Force(CTC).
The CTC (Spine Volume 26, Number 5,pp E93-E113)defined lumbar disc appearances as :
(i) Normal: normal aging, scoliosis, spondylolisthesis could be normal and the binocular appearance of the adult nucleus from the development of a central horizontal band of fibrous tissue to be considered a normal sign of maturation.
(ii) Congenital/Developmental variation.
Adaptation to abnormal growth secondary to scoliosis or spondylolisthesis.
(iii) Degenerative/ Traumatic.
N.B. The CTC emphasised that 'traumatic does not imply that trauma is necessarily a factor or that degenerative changes are necessarily pathologic as opposed to normal aging process'.
Annular Tears(properly called annular fissures)Separations between annular fibres, avulsion of fibres from VB insertions, or radial/TV or concentric breaks. The terms 'tear' or 'fissure' describe the spectrum of such lesions and do not imply that 'the lesion is consequent to trauma'.
Degeneration: Desiccation, fibrosis,narrowing of the disc space, diffuse bulging of the annulus beyond the disc space, extensive fissuring('i.e. numerous annular tears'),mucinous degeneration of the annulus,defects and sclerosis of the endplates and osteophytes at the vertebral apophyses.A disc demonstrating one or more of these degenerative changes can be subclasssified : (a)spondylosis deformans-possibly normal ageing process ,or(b) intervertebral osteochondrosis-possibly the consequence of more clearly pathologic process, with more changes including end plate sclerosis).
Herniation:Is defined as localised displacement of disc material beyond the limits of the IV disc.The material may be nucleus, cartilage,fragmented apophyseal bone, annular tissue,or any combination thereof.
(i) Focal herniation:by convention, a 'focal herniation' involves < than 25%(90 degrees) of the disc circumference.
(ii) Broad -based herniation: by convention ,25-50% (90 to 180 degrees) of the disc circumference
Symmetrical bulging disc:50-100% (180-360 degrees) of disc tissue beyond the edges of the ring apophyses,and is NOT considered a form of herniationThese may be asymmetrical bulging discs , seen with scoliosis and again , not a form of herniation.
CTC POSITION ON NORMAL AGING.
With normal ageing fibrous tissue replaces nuclear mucoid matrix ,but the disc height is preserved and the disc margins remain regular.Radial tears are found in a minority of post mortems >40 years ,thus probably not 'normal'.Slight remodelling can occur due to osteoporosis.Small amounts of gas can be detected in elderly individuals at the annular-apophyseal enthuses,probably in small transverse annular tears,and possibly signifying early spondylosis deformans.A large amount of gas in the central disc space is always pathological and is a feature of intervertebral osteochondrosis.Anterior and lateral osteophytes have been found in 100% of skeletons of individuals over 40 years of age, so are consequences of normal ageing.Posterior osteophytes are found in a minority of skeletons over 80 years of age,and are not inevitable age accompaniments.End plate erosions with osteosclerosis and chronic reactive bone marrow changes also appear to be pathologic. Slight to moderate decrease in central disc intensity on T2 weighted MRIs can be a non pathologic age-related observation, but it should be uniform among the individual's regional discs.
CTC POSITION ON 'HERNIATED DISC'.
(1).'localised displacement of nucleus,cartilage,fragmented apophyseal bone , or fragmented annular tissue beyond the intervertebral disc space,defined by the vertebral bony endplates and the edges of the vertebral ring apophyses, exclusive of osteophytic formations.'
(2).'Generalised ,meaning greater than 50% (180-360 degrees) displacement of disc material beyond the ring apophyses ,or adaptive changes with scoliosis or spondylolisthesis are NOT HERNIATIONS.They are BULGES.
(3) 'The term protrusion has been used by many authors..non-specific..similar to the term prolapse..'herniated disc is the best general term to denote displacement of disc material, over protrusion, protruded disc,prolapse or extruded (sic) '
(4) Disc herniations may be further specifically described as 'contained'(displaced portion is covered by outer annulus) or 'uncontained',when absent of any such covering.
CTC POSITION ON '50% CUT-OFF.
'The 50% cut off line is established by way of convention to lend to precision in terminology and does not demarcate aetiology,relation to symptoms,or treatment indications''.
CTC POSITION ON 'BULGES'
'(1)refers to an apparent generalised extension of disc tissues beyond the edges of the apophyses...in 50% or greater disc circumference and a relatively short distance ,usually < 3mm,beyond the edges of the apophyses.'
(2) Bulge is sometimes a normal variant(usually at L5/S1),can result from advanced disc degeneration or from VB remodelling as a consequence of osteoporosis,trauma or adjacent structural deformity.,from ligamentous laxity in response to loading or angular motion or can be an 'illusion' caused by a central sub ligamentous disc protrusion.
(3) 'Bulging is by definition not a herniation'.'The term 'bulging' does not imply any knowledge of aetiology,prognosis ,or need for treatment or necessarily imply the presence of symptoms.'
Reference : Recommendations of the Combined task Forces of the North American Spine Society,American Society of Spine radiology,and the American Society of Neuroradiology.: Nomenclature and Classification of Lumbar Disc Pathology. David F. Fardon and Pierre C. Milette (SPINE Volume 26,Number 5,pp E93-E113)
LUMBAR DISC NOMENCLATURE : version 2 provided an update to these guidelines and was published in 2014 by Fardon et al.This is the current edition.
In 201 Herniation 0-50% ('focal '0-25% and 'broad based' 25 -50%) and Bulge 50-100% (symmetric or asymmetric).
In 2014 the Guidelines regard (A) Bulge (general displacement of annulus >25% circumference and generally <3mm beyond edges apophyses) and (B) Herniation is localised displacement <25% (Subgroup Herniations are :Protrusion:largest diameter extension < base herniation) and Extrusion(diameter extension > base diameter).
So there are precise morphological definitions of Bulges, Herniations, Protrusions and Extrusions.Sequestrations are also type of Herniation in which there is no visible continuity with the parent disc.
The text NeuroImaging Part II also refers to these definitions (Version 2 Lumbar Combined task Force Fardon et al 2014) ( Table 39,page 793,R.Gilberto Gonzalaez and Joseph Masedev).
The Combined task force comprises the North American Spine Society(NASS), American Society of Spine Radiology(ASSR) and American Society of zneuroradiology(ASNR).
The use of standardised nomenclature is intended to maintain consistency and accuracy in normal and abnormal lumbar disc descriptions. The Combined task force emphasises that terms such as annular fissure, annular tear, disc protrusion/herniation/prolapse do NOT denote or imply a traumatic or non-traumatic causation.This appears in all the publications.
Patients are advised to follow the advice of their treating medical practitioner at all times.
Dr Michael Coroneos is a senior Brisbane neurosurgeon.
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