Hansen Type II Intervertebral Disc Diseaseoldwebsite.anzcvs.org.au/surgery_assets... ·...

ANZCVS Residents Forum 2014

Hansen Type II Intervertebral Disc Disease

Daniel R James BVSc(Hons) MANZCVS(Radiology/ Surgery)


Content:

► Predominantly T-L ►Brief anatomy ► Limited pathophysiology ►Treatment:

▪ Surgery ►Decompression ►Stabilisation

▪ Medical ► Prognosis

► Foraminal nerve root compression

►Regenerative therapies ►CSSM ► L-S Dz

Not covered:


Definitions:►Hansen described the pathology of DISC DISPLACEMENTS ▪ Extrusion = Hansen type I !!!

▪ Protrusion = Hansen type II


Definitions:

►Hansen classifications are not a description of the type of degeneration !

▪ But: ►While extrusion of normal, fibroid metaplastic or

chondroid metaplastic disc can occur ►Clinical protrusion is typically a feature of discs

affected by fibroid metaplasia


Anatomy

• Annulus (anulus) Fibrosus is 1.5 to 3 times thicker ventrally than dorsally !

• Only outer layers of densely packed collagen have vascular supply !

• Innervation confined to the periphery of the annulus and relatively sparse.

• Shown to originate from Dorsal ganglia up to 2 segments cranially and caudally • Dorsal longitudinal ligament well innervated

Brisson VCNA 2010


Disc Degeneration

►Fibrous metaplasia is a “normal” aging-associated change ▪ Fibrous collagenisation of the nucleus pulposis

►Becomes less distinct from the annulus ►Less fluid/ more solid

▪ Concurrent degeneration AF as it bears more load ►Bulging of NP in weakened/ fissuring AF ►Ultimately dorsal protrusion


Disc Degeneration -theories from humans

►Disc degeneration due to increased movement/ excessive loading ▪ Hypermobility

►Pain/ tissue stiffening ▪ Altered muscle activation/ changed physiologic loading

► Increased axial and shear loading

▪ Hypomobility later in course ►Reparative function limited by loss of

diffusional capacity from vertebral endplate


Disc Degeneration

►Abnormal postures (Kyphosis) suggest process similar in veterinary patients !

►Endplate changes identified on MR in dogs Besalti

JAVMA 2006

Bray JAAHA 1998

Surgeons summary

►Focal extension of AF & NP into the canal ►Outer AF and DLL usually intact ▪ Can rupture and extrude

►Smooth, firm, round and rarely adherent


Hansen II Disc disease►Compression not Contusion

►Can have a dynamic nature due to instability

▪ Much less research ▪ Axonal loss/ wallerian degeneration


Hansen II Disc disease►Large non-chondrodystrophic dogs?

▪ Reports of 41 to 92% of dogs> 20kg actually presenting for type I IVDD Kranenburg Vet Journal 2013 Cudia JAAHA 1997

▪ 24/42 non-chondrodystrophic dogs with MRI evidence of protrusion/ bulging actually clinical for an extrusion Besalti JAVMA 2006

▪ Cervical Hansen I also reported to be most common in cervical region of med-large dogs


Hansen II Disc disease!

► Large, non-chondrodystrophic dogs ▪ GSD over-represented Downes JSAP 2009

► Also the most reported large breed for Hansen I ▪ Non chondrodystrophic dogs 7.3 times more likely Kranenburg Vet Journal 2013 !

► Peaking at 6-8 years !

► Males Downes JSAP 2009, Macais 2002 Or not Kranenburg Vet Journal 2013 !!

► T13-L1 most common site (similar Hansen I) Downes JSAP 2009

!► L-S probably the only site where II>I


Clinical signs• Insidious onset over weeks to months

•Step-like acute worsening !

• Clinical signs reflect anatomic location •Grey + white matter involvement !

• Frequently not in overt pain and may show no painful response to palpation in the chronic stage

•Despite inflammation of disc, facets, compression of innervated structures etc •Unless nerve root compression !

• Ambulatory paraparesis most common presentation

Macias JSAP 2002


Differential Diagnoses!

►Other Compressive ▪Neoplasia !

►Degenerative ▪Degenerative myelopathy


Diagnostics

Macias JSAP 2002


Diagnostics-spondylosis


Diagnostics-spondylosis►Small ventral herniations along VLL

implicated in the formation of osteophyte Romatowski Compendium 1986

►Spondylosis evident in 12/28 cases Downes JSAP 2009

►No differences between dogs with IVDD and dogs with non-IVDD neurologic disease Levine JAVMA 2006

►Dogs with type II IVDD had greater severity of spondylosis than type I Levine JAVMA 2006

►Doesn’t develop at a higher incidence at sites of disc protrusion Levine JAVMA 2006


Diagnostics

►11/28 cases had a further protrusion identified Downes JSAP 2009

►Narrow disc space 14/28 Downes JSAP 2009 ►No apparent Radiograph findings 6/28 Downes JSAP 2009


Diagnostics

►Grading of disc degeneration observed on MRI correlates well with histo but limited use clinically Kranenburg Vet Journal 2013, Bergknut AJVR 2011

►CT without myelography was able to identify protrusion in 0/16 cases Dennison VRU 2010


Diagnostics

►Attributing significance to a lesion? ▪ 47% of large breed, H II cases had multiple

protrusions on myelography Macias JSAP 2002

▪ Bulging or protrusion on MRI can be associated with no clinical signs Besalti JAVMA 2006


Diagnostics

►Not likely to have T2 hyperintensity on MR as no contusion

►Gliosis identifiable on MR but very advanced finding


Diagnostics

►Therapeutic pred trial ▪ DM will not respond

►Genetic testing for DM


Treatment

►Medical ▪ Corticosteroids

►Anti-inflammatory doses ►Decrease vascular permeability

▪ Decrease oedema ► Alleviate some component of compression

►Potential for muscle wastage and weight gain ▪ worsening paresis


Treatment

►Surgical ▪ Clear rationale of decompression ▪ Decision complicated by age and uncertain

progress of disease ▪ Outcome frequently gratifying


Treatment

►Surgical !

▪ Decompression !

▪ Stabilisation


Goals of stabilisationMcKee JSAP 2008

1. Prevent further protrusion discs 2. Prevent any dynamic (bending and rotation) component of spinal cord

compression 3. Promote long-term intervertebral disc atrophy.


Stabilisation Watine JSAP 2006

►Dorsal implantation corridors of the last four thoracic vertebrae are narrow ▪ 63 % (of 40) thoracic vertebrae, the right

azygos vein < 1 mm from the vertebral body\ ► Screws angle 40-55 degrees from vertical


Hemilaminectomy, Stabilisation +/- annulectomy Downes JSAP 2009

!►Mostly DCPs placed at tubercle of rib or junction of

pedicle and transverse process. (some bilateral SOP, some pin/PMMA)

►Annulectomy not performed if risk perceived too great (7/31)



!► 9/28 had VV Sinus lacerated intra-op ► 17/28 deteriorated at 24hr post op ▪ Subsequently 12/16 improved

► 14/24 improved by 2-4 weeks post op (2 worse) ► 7 examined 3-52 months, 6 improved ► 17 phoned, 15 improved ► 5/5 non ambulatory dogs became ambulatory ► 21/24 improved long term, 13 “normal”



!► 7/7 dogs without annulectomy improved ▪ Stabilisation-> annular atrophy?

!► 2 dogs deteriorated after developing new

protrusions (one at adjacent site) ▪ no fusion seen on any follow up imaging, ▪ no protrusion at original site


Lateral Corpectomy Flegel VS 2011, MOISSONNIER VS 2004

!► 1/2 vertebral body’s height for the ventral margin

► 1/2–2/3 vertebral body’s width for the depth margin

1/4 cranial vertebral body’s length for the cranial and caudal margins


Lateral Corpectomy MOISSONNIER VS 2004

►None of the dogs had transient worsening of their neurologic status

►All dogs improved by 1-4 grades ► 11/15 dogs were free of disease at the end of the

survey ▪ 7/15 judged H II


Lateral Corpectomy Salger VS 2014

►Complications: ▪ Hemorrhage from the venous vertebral sinus

(18,25%)

▪ Injury of nerve roots (6, 8.3%).

► Dogs having improved MFS: ▪ after surgery 44.4%, 18.7% were worse ▪ at discharge 75.9%, ▪ at reexamination 100%

► Prognosis is associated with presurgical neurologic condition *no differentiation between chronic HI and HII


Corpectomy and stability

►Significant increases in ROM during flexion/extension and lateral bending when PLC was performed Vizca´ıno Reve´ s VS 2012

►Instability enhanced when a hemilaminectomy is added but not when a mini hemi is performed Vizca´ıno Reve´ s VS 2012 de Vicente VCOT 2013

“the use of both techniques in the same intervertebral space without further spinal stabilization is discouraged”


Prognosis

Conventional wisdom: !->Significantly worse than dogs with extrusions Macias JSAP 2002

22% considered to have a positive outcome


Prognosis

►Nearly half of the dogs treated non-surgically deteriorated <1 year, leading to euthanasia.

►No long-term deterioration in dogs treated surgically although neurological deficits may remain.

•Conventional wisdom: ->Significantly worse than dogs with extrusions Macias JSAP 2002

22% considered to have a positive outcome


Prognosis- Cervical Hemilaminectomy Schmied JAAH A 2011

Hansen Type II disc protrusion •excellent in 47% •good outcome was seen and 32% of case. •Outcome was significantly better for small breed dogs

!•Hansen Type I outcome>Hansen Type II

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