Ch 31 Cervical vertebral column Flashcards
What CN deficits can be seen with a C1-C5 lesion?
Positional strabysmus and/or facial hyperaesthesia with C1-C3
v. rare!
What is Horners Syndrome?
What spinal cord segment can cause this?
What is the path of the sympathetic nerves?
Horners syndrome is loos of sympathetic innervation to the eye causing miosis, ptosis, enophthalmos and elevation of the third eyelid
T1-T3
Hypothalamus -> descends sp. cord in lateral tectotegmental tracts
Why do dogs with cervical lesions often present with more pronounced motor dysfunction in the pelvic limbs?
The descending UMN tracts to the pelvic limbs are more peripherally located within the spinal cord
C1-C5 CS
C6-T2
difference in stride length between the thoracic and pelvic limbs is sometimes called a two-engine gait.
Ventral Approach to the Cervical Vertebral Column
paramedian
right sternocephalicus muscle is separated from the right sternohyoideus muscle (Figure 31.3). The sternohyoideus muscles are then retracted to the left with the trachea, esophagus, and carotid sheath.
protect the trachea, right recurrent laryngeal nerve, and the contents of the right carotid sheath
decreasing the likelihood of hemorrhage from the right caudal thyroid artery.
exposure of the longus colli muscles (D) and the longus capitis muscles
right carotid sheath
he vagosympathetic trunk, carotid artery, and internal jugular vein
Ventral Approach to the Atlantoaxial Articulation
What are the benefits of the right parasagittal?
What surgical landmark can be used for ventral C1-C2
right-sided parasagittal approach
advantages: improved exposure of the joint avoidance of dissection thyroid gland, trachea, and recurrent laryngeal nerve.
improved ability to drill or drive a Kirschner wire across the right C1-C2 articulation without the larynx and trachea directly adjacent
mandible to a point at least 5 cm caudal to the caudal edge of the thyroid cartilage
right sternothyroideus and sternocephalicus muscles and the right carotid sheath are then exposed and separated, exposing the paired longus colli muscles and cervical vertebrae
retraction of the right carotid sheath to the left side
locating a pointed ventral prominence, the ventral tubercle, on the caudal aspect of C1
Lateral Approach to the Cervical Vertebral Column
lateral or foraminal IVDE, as well as nerve sheath neoplasms
Articular processes of C3-C6 are palpated to serve as a landmark
Platysma
Blunt seperation through brachiocephalicus
Splenius
Serratus vantralis
Plane of dissection between longissimus capitus and complexus muscles to expose articular facet
Dorsal branch of the spinal nerve needs to be sacrificed, the tendinous attachments of the complexus and multifidus are then detached from the articular process
Longissimus capitus sharply dissected from transverse process and reflected ventrally to fully expose the joints
C5-C7 requires seperation of brachiocephalicus from trapezium (not dissection through). The superficial cervical artery and vein will be located between these muscles and is ligated
Lateral Approach to the Brachial Plexus
What muscle do the spinal nerves of the brachial plexus lie deep to?
Scalenus muscle
Atlantoaxial Instability
leads to compression and contusion of the cervical spinal cord, resulting from displacement of the vertebrae (subluxation) into the vertebral canal;
atlantoaxial subluxation results from a ligamentous and/or osseous abnormality
AA anatomy
neurovascular paths?
Movement at this joint is mainly rotational,
First cervical spinal nerve and its associated vasculature pass through the lateral vertebral foramen
he vertebral artery enters the vertebral canal through the lateral vertebral foramen, after first having run through the transverse foramen of the atlas
How many pairs of foramina does the atlas have?
Two
- Transverse foramen - passes obliquely through transverse process
- Lateral vertebral foramen - perforates the craniodorsal part of the vertebral dorsal arch. First cervical spinal nerve and its associated vasculature run through here
How many bony elements for the atlas and axis develop from?
How long does it take for fusion?
Atlas - 3 boney elements
Axis - 7 boney elements (pair of arches, 3 parts of the body, the dens, apical elements of the dens)
Fusion of dorsal atlas by 106d, ventral suture by 115d
Fusion of all parts of axis from 30 - 396d
List the stabilising ligaments of the AA joint
dens = Odontoid process
Transverse ligament - holds the dens within the ventral aspect of the vertebral foramen. Prevents dorsal movement which allowing rotation
Apical ligament - attachs dens to basioccipital bone
Bilateral alar ligaments - Attach dens to the occipital condyles
Dorsal atlantoaxial ligament - Joins dorsal arch of atlas to craniodorsal spine of axis
Alar ligaments provide the most important stabilisation against VD shearing forces
List possible congenital or developmental abnormalities of the AA joint
Traumatic atlantoaxial subluxation can occur in dogs of any breed
Dysplasia (34%)
Hypoplasia or aplasia (46%)
Dorsal angulation of the dens
Seperation of the dens
Absense of the transverse ligament
Incomplete ossification of the atlas
Block vertebrae
Spinal cord trauma secondary to an acute episode of subluxation has the same underlying pathophysiology as that related to acute disc extrusion and acute vertebral fracture-luxation.
tear ligaments of fracture dens
What percentage of dogs with AA sublux will have a normal dens?
24%
What breeds are predisposed to congenital abnormalities predisposing to AA instability?
Yorkies
Chihuahuas
Min Poodles
Poms
Pekingese
Standard Poodles! - inherited ansense/hypoplasia of the dens
What is predictive of AA instability on a plain lateral radiograph?
An angle between the atlas and axis of less than 162 degrees
CT and MRI
CT can assist with identification of dens conformation or the presence of a fracture of the dens or vertebra, as well as with deciding on appropriate size of implants and surgical implant placement
MRI can provide additional information regarding spinal cord pathology such as hemorrhage or edema and syringohydromyelia, which might be important for prognosis . Additionally, MRI enables visualization of the ligamentous and supporting structures
AA Tx: conservative
what?
how long?
how sccessful?
abilize the atlantoaxial articulation while the ligamentous structures heal
strict cage confinement for 6 weeks, analgesia
external coaptation ideally using a rigid cervical brace.
splint must immobilize the occipitoatlantoaxial articulation > must come over the head rostral to the ears and extend caudal to the level of the cranial aspect of the thorax.
Complications
recurrence of disease
corneal ulcers,
migration of the splint
moist dermatitis and decubital ulcers, hyperthermia,
respiratory compromise
otitis externa,
nonsurgical or conservative approaches are likely to result in recurrent or progressive clinical signs.
AA surgery
dorsal - what not achieved
ventral -advanatges?
goal = align and stabilize AA, prevent further spinal cord damage
Dorsal
Osseous fusion generally is not achieved > cannot resist movement in directions other than flexion
continuous movement, more likely failure of implants is associated with recurrence of clinical signs
Ventral
advantage of creating a bony ankylosis providing permanent joint fusion
odontoidectomy can be performed if required
What is a contraindication for dorsal stabilisation of AA sublux?
What are the advantages of ventral stabilisation?
Dorsal deviation of the dens
Dorsal techniques for AA stabilisation (5) and their associated long term success rates
Atlantoaxial wiring/dorsal loop wiring - 52%
loop needs to be folded back toward the axis, and at this time risk for iatrogenic trauma to the spinal cord
Double stranded cross-suturing (less than 2kg) - 50%
nuchal ligament technique - 75%
Dorsal cross-pinning
Kishigami AA tension band - 75%
What is this device?
What are its advantages?
Kishigami tension band for dorsal stabilisation of AA sublux
Reduced risk of damaging the spinal cord as it does not need to be passed under the dorsal arch
List the ventral stabilisation techniques for AA subluxation and their associated long-term success rates (4)
articular cartilage can be scarified. This can encourage bony ankylosis
Transarticular screws or pins - 47%
Pins and PMMA - 94% (long-term complications 34%)
Screws and PMMA (placed 30-40 degrees)
Ventral plating (mini H-plate 2.0mm, 5-hole butterfly plate 1.5mm)
What is the mean optimal AA insertion angle of transarticular screw/pin insertions?
What was the mean corridor length and width?
40+/-1 degree in medial to lateral direction
20+/-1 degree in VD direction from ventral aspect of vertebral foramen of the axis
Mean corridor length 7mm, width 3-5mm
AIming in a craniolateral direction
What is the overall rate of complications for dorsal and vental stabilisation of AA sublux?
Dorsal 71%
Ventral 53%
Implant failure of the transarticular pins most common complications. Implant failure 48% dorsal vs 44% ventral, may or may not require re-op
Fracture of the Atlas or Axis
The dorsal arch of the atlas can fracture following a dorsal stabilization techniqu
Episodic pain has been reported in dogs for several months to life postoperatively
Improper pin placement with inadequate bone purchase is the main cause of implant migration. Implant failure can be an incidental finding at recheck
post-op
nsaid, monitor, restrict 4-8wks
another surgery may not be necessary, > strong fibrous or osseous union.
What are the known risk factors effecting surgical outcome for AA stabilisation
Ageof onset: Dogs under 24m had greater odds of successful outcome
Durationand severity of clinical signs: Under 10m associated with greater odds of successful outcome
AA Px
conservative?
mortality rate?
conservative: good long-term outcome has been documented in 10 of 26 (38%) cases
perioperative mortality rate: 4% and 30% of dogs
Biomechanical evaluation of two dorsal and two ventral stabilization techniques for atlantoaxial joint instability in toy-breed dogs
Progin 2021
4 techniques (dorsal wire, modified dorsal clamp kishigami, ventral transarticular pin, and augmented ventral transarticular pin fixation). experimental (13 skull)
The AAJs with dorsal wire, ventral transarticular pin, and augmented ventral transarticular pin fixations had similar biomechanical properties, but not clamp.
load cycling and clinical studies are needed
Atlanto-axial ventral stabilisation using 3D-printed patient-specific drill guides for placement of bicortical screws in dogs
Toni 2020
To report outcome and complications following atlanto-axial stabilisation by polymethylmethacrylate applied to screws placed using 3D-printed patient-specific drill guides.
Materials and Methods: Case series
Of 61 bicortical screws placed, 57 (93%) were fully contained
rate of vertebral canal screw penetration of 7% in this
study compares favourably to previously reported values of 21%
and 9% using similar patient-specific guides
stainless steel screws resulting in greater CT artefact then would have occurred with titanium screws
Computed Tomography and Biomechanical
Comparison between Trans-Articular Screw
Fixation and 2 Polymethylmethacrylate Cemented
Constructs for Ventral Atlantoaxial Stabilization
Guillaume Leblond 2018
cadavers
The CT data revealed that TSF achieved significantly better apposition than
cemented constructs
4.4% were graded as dangerous and
86.8% as optimal.
Determination of cutoff values on computed tomography
and magnetic resonance images for the diagnosis of
atlantoaxial instability in small-breed dogs
Bastien Planchamp 2022
Study design: Retrospective multicenter study.
Sample population: Client-owned dogs (n = 123) and 28 cadavers.
ventral compression index (VCI f ≥0.16 in extended and ≥0.2 in flexed
head positions were diagnostic for AAI (sensitivity of 100% and 100%, specificity of 94.54% and 96.67%, respectively).
The location of the endotracheal tube tie can influence interpretation of MR images of the craniocervical region of small breed dogs
Dorsal compression of the cervical spinal cord can be identified by examining the cervical subarachnoid space at the atlantoaxial (AA) or atlantooccipital region using MRI. Dorsal compressive lesions have been described with various terms, such as AA constrictive lesions, dural fibrous bands, or AA bands,
These dorsal compressive lesions, identified
with MRI, are a significant predictor of craniocervical junction
abnormalities, such as atlantooccipital and AA instability,
atlantooccipital overlap,
In what percentage of dogs does the C5 spinal cord segment contribute to the brachial plexus?
24%
What nerves are branches of the brachial plexus? (8)
Brachiocephalic
Suprascapular
Subscapular
Axillary
Musculocutaneous
Radial
Median
Ulnar
Dorsal thoracic
Lateral thoracic
Long thoracic
Pectoral
Muscular branches
List the 6 classes of nerve trauma
Class 1: Neurapraxia - interruption of the function and conduction of a nerve without structural changes. Reversible, up to 6 weeks to improve
Class 2: Axonotmesis - crush or percussion injuries causing Wallerian degeneration. Internal architecture of the nerve, including the endoneurium and Schwann sheath is well preserved. Recovery expected but can take several weeks
Class 3: Neurotmesis - Disruption of axons and endoneurium but fascicular orientation is maintained by intact perineurium
Class 4: Neurotmesis - Disrupted perineurium
Class 5: Neurotmesis - Entire nerve severed
Class 6: COmbines several of the previouse degree of injury per fascicle
neurotmesis: Full recovery usually not seen and accompanied by scar.
nerve roots lack an epineurium, traction of the thoracic limb or severe abduction of the scapula can result in stretching or avulsion of these nerve roots, usually within the dura
dorsal root = sensory input into the spinal cord
ventral root = motor function and autonomic innervation.
myelin sheath for each myelinated axon is formed by Schwann cell plasma membranes wrapping around the axon like an “onion peel.”
The Schwann cells are separated by junctions called nodes of Ranvier, which assist in the rapid conduction of action potentials along the axon.
Endoneurium surrounds each axon
Groups of axons are surrounded by perineurium
tissue around the entire nerve, called the epineurium
What are the 3 forms of brachial plexua injury and their common associated signs?
Unless avulsion confirmed, traction trauma to this region is appropriate
Injury of the cranial portion (C5-C7) - Effects musculocutaneous, axillary, subscapular and suprascapular nerves. Loss of shoulder movement and elbow flexion, shoulder atrophy
Injury to the caudal potion (C8-T2)- Radial, median and ulnar nerves. Cannot extened elbow and thererfore cannot weight bear. Radial nerve involved in 92% of dogs. Can sometimes see Horners syndrome and loss of cutaneous trunci
Complete injury (C6-T2) - Drags leg knuckles, shoulder more ventral, hypotonic and atrophy
If the injury is severe > damage the spinal cord
- ipsilateral pelvic limb general proprioceptive ataxia
- UMN paresis or plegia.
WHat is indicative of a poor prognosis on EMG?
Early decreased radial nerve conduction velocity indicates a poor prognosis
Electromyography allows detection of abnormal spontaneous electrical activity indicative of denervated muscles 1 week to 10 days after injury
surgical techniques for brachial plexus repair
Neurotization (nerve transfer) - Can be neuroneural or neuromuscular using 9-0 monofilament nylon
Reimplantation via hemilaminectomy, durotomy, incision into pia mater and spinal cord
Successful neurotization in cats using right lateral thoracic and thoracodorsal nerve to reinnervate the left transected musculocutaneous nerve
adult dog, this axonal regrowth can reach at least 10 to 15 cm within a 4-month period
Brachial avulsion Px
grave if radial nerve avulsion occurs
Carpal arthrodesis or tendon transposition > triceps innervation is required to be able to bear weight through the elbow
given at least 4 to 6 weeks before a grave prognosis
Limb amputation should be discussed if self-mutilation becomes apparent and is not responsive
What percentage of IVDH are cervical?
What type?
breed?
pathophysiology of spinal cord concussion and compression
14-25%
most type I extrusion
smll.chondrodys breeds
or
Labs, doberman, dalmation
most common sites of cervical disc herniation in chondrodystrophic dogs?
80% C2-C4
44-59% C2-C3
Caudal disc spaces are more common in Yorkies and Chihuahuas as well as large breeds
IVD anatomy
where widest IVD?
What is AF function?
AF thickest where?
how AF connect to bone?
AF = bands of parallel fibers that run obliquely, near IVD become cartil
every intervertebral space (except between C1 and C2), uniting the bodies of adjacent vertebrae to form amphiarthrodial joints
the widest cervical intervertebral spaces are C4-C5 and C5-C6; the narrowest is C2-C3.
AF > provide a means for transmission of stresses and strains required by all lateral and upward movements.
one and a half to three times thicker ventrally than dorsally
hyaline cartilaginous end plates cover the epiphyses of the vertebral bodies > attached to annular lamellae, a continuation of the Sharpey fibers
vertebral ligaments (4)
internal vertebral venous plexus along the floor of the vertebral canal
Dorsal longitudinal
(dorsal to AF)
thickest in the cervical vertebral column, offering greater resistance to dorsal herniation of nucleus pulposus material
ventral longitudinal
epidural space ventral
yellow (ligamentum flava)
interspinous and supraspinous
differentials (9)
FCE
AA
CSM
MUO
Noeplasia
Fracture/luxation
Disco
cyst
syringohydromyelia
cervical IVD CS
what % have LMN C1-5?
45% acute, hyperaethesia 90%, 60% minimal signs (dt larger canal)
nerve root signature
34% LMN cor C1-5 in msall dogs
respiratory comromise > paresis/paralysis of resp. muscles causes hypoventilation
cervical IVD dx
- CSF
- rads: rule out disco/#/malformation. Narrow IVd/mineralisation (25% accuracy)
- myelogram CT: heterogenous, hyperattenuating extradural mass with loss of epidural fat. possible compression inversely proprtional to ppst-op neuro status
- MRI: nonivasive, high res image with increase localisation accuracy compared to CT. degree of compresion not prognostic. Hypointense on T2W
ID hydrated IVD (hyperintense, seagull)
conservative TX cervical IVD
aim?
what % reccur
Levin 2007
enables resolution of the inflammation and stabilization of the ruptured intervertebral disc by fibrosis, preventing further herniation
4-6 weeks rest
meds
36% recurrence
What is chemonucleolysis?
Intradiscal injection of chondroitinase ABC to treat disc herniation. 92% of dogs improved with 77% having excellent improvement
indications for cervical IVD sx
severity or progressive
fail to respond to medical
unremitting pain
finances
pros’ and cons of ventral approach
Pros
- remove disc easier
- minimal muscle dissection
- prophylactic fenesrtation
cons
- haemorrhage
- poor field of view
- reduced exposure for lateral/foramen disc
pros of dorsal approach
pros
- provide increased decompression
- better lateral access
V-slot
maximum sizes of a ventral slot window?
haemostasis?
Roerig 2013
modified paramedian approach: protect trachea, sheath and recurrent n. and reduce bleed from thyroid a.
33% length of vertebral body
50% width (but preferably 33%)
excessive may lead to instability ad subluxation
haemorrhage: cool avage, wax, gelatin sponge, macerated muscle
most residual compression post CT
What are the advantages of a slanted slot?
What are the recommened window sizes?
Provides access at the site of herniation without removing a large portion of the annulus, thereby preserving more stability
Window: 20% width and 20-25% length
What are the reported complication rates of v-slot?
10% 0verall (7)
what spaces phrenic n originate?
9.9% complications, 6.4% of which are major
Mean mortality 3-8%
Respiratory compromise (phrenic nerve C5-C7) > hypovent + aspiration
Cardiac dysrhythmmias (VPC) dt near sheath
Haemorrhage (18.9%)
Neuro deterioration > excessive manipulation, horners, layngeal paralysis
Instability (8% when width 50%)
seroma
dorsal laminectomy
hemilainectomy
dorsal
multifidus elevated, pinous and yellow lig removaed
laminectomy extended 75% not include articular process
Hemi
indicated in lateral disc
fenestration
AIkawa 2012
Harris 2020
prophylactic rather than sole Tx
A: shoud prevent further extrusion therefore reduce recurrence
H: 30% new disc materila into canal in TL - unable to check if V-slot
may exacerbate bulging in Type II
collapse of sublux (major controbutor to stability > not recommended if >30kg
What has been shown to be associated with prognosis for cervical IVDH?
more recent brazil study
Site: caudal to C3-C4 have poorer prognosis (likely included Wobblers)
single vs lutli vlsot not affect outcome (Gou 2020)
Degree of injury: LMN dysfunction, presence of VMF not predicitive
non-ambulatory ~70% recovery
Duration of disease: Able to walk within 96hr are likely to make a full recovery, dogs that do not walk within 2 weeks are likely to have residual deficits
Type of Tx:
36% recurrency with conservative vs 5-10% surgical
brazil: 10% recurrence
v-slot 90% full recovery 1m and 98%
(60% caudal in large breed)
hemilam 80% at 12m, outcome better with Type I small breed than type II large breed
hihger complication with v-slot but longer recovery wtih slanted slot, Hansen type II good and excellent in 47% and 32%
Anatomical features of the canine C2-C3 spinal cord vascular environment
Mathieu Taroni
Interarcuate branch (IAB) is a vascular structure, particularly developed in C2-3 intervertebral space, forming a dorsal bridge that connects ventral venous plexi in the vertebral canal
when performing a laminectomy or hemilaminectomy, precise knowledge of those vascular structures is critical to prevent hemorrhage
On the basis of the results of the present study, we concluded that distraction-fusion of the C5-C6 vertebrae did not alter the IDP in the C6-7 (caudally adjacent) IVD in ex vivo cadaveric canine C4-T1 vertebral specimens without evidence of IVD degeneration.
Although the limitations of this study precluded us from drawing any definitive conclusions regarding the complex pathogenesis of ASDis, IDP does not appear to play a major role in the early phase of the disease process while the IVD has no degenerative changes.
Because degeneration alters the ability of nucleus pulposus to absorb forces, it is possible that the IDP in IVDs adjacent to vertebral distraction-fusion sites may increase in vivo as disk degeneration progresses.
Ventral Slot Surgery to Manage Cervical Intervertebral Disc Disease in Three Cats
Crawford
incidence IVDD in cats 0.12 to 0.24%, compared with 2% in dogs
Hansen type I disc disease and
protrusions (Hansen type II
Methods retrospective case series n=3
Results A routine ventral slot surgery without complication,
neurological improvement in all
Clinical Significance Ventral slot surgery good long-term outcome in for
feline cervical intervertebral disc herniation. To avoid excessively wide slot > careful surgical planning was
performed with preoperative measurement of the desired maximum slot dimensions
Cherrone 2004.
A retrospective comparison of cervical intervertebral disk disease in nonchondrodystrophic large dogs versus small dogs.
Rossmeisl 2013
Acute adverse events associated with ventral slot decompression
in 546 dogs with cervical
Accuracy of a patient-specific 3D printed drill guide for placement
of cervical transpedicular screws
Sinead E. Hamilton-Bennet
Prospective case-series.
Sample Population: Thirty-two cervical pedicle screws (CPS) placed in 3 large
breed dogs.
The majority (29/32) of these screws were
placed without evidence of vertebral canal breach (grade 0), whereas a vertebral canal
breach <2 mm (grade 1) was detected in 3/32 screws.
In a cadaveric study comparing the biomechanics of
bicortical pins and monocortical screws with PMMA placed
free-hand in the canine cervical vertebral column, 100% of
bicortical pins violated the vertebral canal compared with a
much lower incidence after monocortical screw fixation.32
The angles for ideal screw insertion are of limited use in
dogs, because of conflicting reports, inter- and intra-breed
anatomical variations, and rotational effects of both surgical
positioning and intraoperative probing or screwing on vertebral
alignment.14,33,34 Consequently, free-hand CPS placement
in dogs is not recommended.14,33
Non-ambulatory dogs with cervical intervertebral disc herniation:
single versus multiple ventral slot decompression
Guo 2020
Retrospective cohort study.
single (123) or multiple (62) VSD
proportion of non-ambulatory dogs with IVDH was 35.3%.
After surgery, 96.2% of the dogs reached ambulatory status.
no difference in the time to reach ambulation after surgery between dogs that underwent single and multiple VSD.
Conclusions good postoperative outcome, and their short-term functional recovery was equal to that of dogs undergoing single ventral slot
compression.
Vertebral fixation does not affect recovery or recurrence
of cervical intervertebral disc herniation in small dogs (< 15 kg)
Kikuchi 2023
Small dogs (n = 303)
recovery and recurrence during the 30-month postoperative
Thirteen cases had recurrent signs of C-IVDH within 30 months of the initial surgery. The recurrence rates were 4.7% (n = 7) in the VF group and 4.3% (6) in the nVF group.
CLINICAL RELEVANCE
In small dogs weighing < 15 kg, there was no difference in postoperative recovery and recurrence rates after VSD with or without concomitant VF. Therefore, in small dogs with C-IVDH, even if the slot volume is increased to remove sufficient disc material during VSD, a good prognosis can be achieved with or without VF.
Video telescope operating monitor–assisted surgery
is equivalent to conventional surgery in treatment
of cervical intervertebral disc herniation in dogs
** Frankar 2023**
ANIMALS
39 dogs with cervical intervertebral disc disease.
METHODS
Prospective study. Dogs were prospectively nonrandomly assigned
No significant differences were noted between the 2 groups regarding the decompression ratio (P = .85), vertebral length body ratio (P = .13), ventral slot width ratio (P = .39), residual disc material (P = .30), and sinus bleeding (P = .12).
No significant differences were found between the 2 groups regarding postoperative neurologic grade (P = .17).
Accuracy of a 3-dimensionally printed custom endoscopy
port for minimally invasive ventral slot decompression in
dogs: A cadaveric study
Kang 2022
Cadaveric study.
Animals: Fifteen
Conclusion: Screw positioning and creation of ventral slots were accurately
performed using the 3DEP by both inexperienced and experienced surgeons.
Clinical significance: The use of a 3DEP for minimally invasive cervical ventral
slot decompression may be an alternative to the conventional ventral slot
in dogs. Additional studies are needed to evaluate efficacy and safety.
Recurrence of signs consistent with
cervical intervertebral disc extrusion in
dogs
Argent 2022
Objectives: Report the rate of recurrent clinical signs following successful treatment of cervical IVDD, and explore the association between treatment method and recurrence.
Materials and Methods: Medical records of dogs with MRI- or CT-confirmed
Recurrence was considered
presumed if based on clinical signs or confirmed if based on repeat cross-sectional imaging
Clinical Significance: Following successful initial medical or surgical treatment, clinical signs consistent
with recurrent cervical disc extrusion occurred with similar frequency. Medically treated cases tended
to have recurrence at the same site as initial presentation, whereas surgical treatment prevented this.
Recurrence usually occurred within 2 years. The retrospective study design, small number of recurrences
and lack of imaging confirmation of every recurrence should be considered when interpreting
the results.
What anatomical differences explain the predisposition of wobblers in large dogs
strutures involed: vertebra, disc, ligament
The vertebral height of the cranial aspect of the foramen in significantly smaller than small dogs, resulting in a funnel shaped vertebral foramen
therefore cerase threshold of cumulative effects of structures encraoching on spinal cord
dober/g.dane have stenotic in caudal
What three factors explain the pathophy of DACSM?
complex as many aspects unclear (doberman without CS)
Vertebral canal stenosis = key static lesion
Pornounced torsion of the caudal cervical column leading to IVD degeneration (caudal cervical spine has three times more torsion than cranial)
Protrusion of larger volume intervertebral discs
C6-C7, C5-C6 in 90%
leads to compression of spinal cord
middle age, large breeed
What causes osseous compression in CSM?
causing severe formaen stenosis dt joint OA and :
Proliferation of the laminae dorsally
Articular processes dorsolaterally
Pedicles laterally
+/-
disc, lig.flavem hypertrophy
c4-c7 in 80%
young, giant breed
What molecular mechanisms play a role in CSM?
Apoptosis of oligodendrocytes interfering with remyelination
Significant reduction in monocyte chemoattractant protein/chemokine ligand 2 (MCP-1/CCL2) concentrations -
Elevation of IL6 - implicated in generation and propagation of chronic inflammation
What are the rates of single lesions vs multiple lesions in CSM?
Large breeds: 50/50
Giant breeds: 20% single site, 80% multiple
What is the rate of post-myelogram seizures in Dobermans?
25%
dynamic vs instability
concept explains developemnt of CS based on experimental studies + proposed key mechanism in humans
worsen or improve depending on position og vertebral column > cord more compressed with flexed or extnded
> extension: 25% reduction of C4-7 diameter in dogs
thus, combo of static and dynamic factors > no evidence that instability plays a role in most cases
instability def
instability = loss of ability of vertebral column to maintain normal amounts of displacment under physioloical loads
Dx CSM
rads: not confirm
CT
good bone resolution, rapid, sedation
may miss main compression site or not ID mutple due to decreased contrast resolution
invasive with myelogram
more useful for OACSM
MRI
best
access spinal cord pathology
inc. accurtae predict site/severity/nature of compression (de caost 2006)
cord atrophy = poorer prognosis
tractography to assess for dynamic component (traction, flex/extend)
*concept of dynamic lesions subjectove and assessment method have not be standadarised (da costa 2000)
Vwf dz
DCM
vwf helps platelt adhesion tp subendothelium, platelet aggregation and bind FVIII > deficiency reduced aggregation and primary haemostatic dz
congenital or 3 types, tupe I most common in doberman where reduced [ ] of all multimers
Dx: vwf antigen assay (eliza) sensitive + MBMT/genetic test
Tx cryopreciptate w Vwf (effective within 30min, last 4hr)/FFp/desmopressin
DCM: can be occult, therefore ECG + echo recommended
What is the rate of improvement in conservative vs surgical treatment of CSM
lack of concensus re best approahc, prob reflect limited understanding of dz mechanism and natural progression
Conservative:
- 54% improved
- 27% static
Surgery
- 81% improvement
consrvative Tx
de costa: 20% worse vs 80% improve with sx
53% euthanised regardless if medical or sx
non-diff in survival time (prob because slow progression) DACSM 1 yr MRI, OACSM 2yr MRI
Tx: ex restrict/physio/nsaid or CCS
How are corticosteroids helpful in conservative management of CSM?
Decrease vasogenic oedema
Protection from glutamate toxicity
Reduction of apoptosis
Sx CSM > GOALs (8)
decision made on severity/pain/compression/owner/other dz and fail medical
many sx, reflects not one more superior than the other
- decompress and reduce recurrence
- patient specific
- consdier if >1 site
- dynmic?
- prosepctive studies to compare tehcniques > most literature based on surgeon preference
- current evidence does not support instability as a factor
- distraction-stabilise eliminate dynamic whch is prob presetn in all forms
- pros/cons of surgery
DACSM sx
subjective if dynamic or static
outcomes generally siimlar accross tehcniques
disc: static (vslot) dymanic - D-S
osseous: static (dorsal/hemi) +/- stabilise
List the direct decompressive techniques for treatment of CSM
Ventral slot (72%)
Inverted cone
Dorsal laminectomy (79-95%, 30% recurrence) increase obidity
Hemilaminectomy
List the indirect decompression-distraction techniques for treatment of CSM
Pins and PMMA (73%)
Screw Bar-PMMA
PMMA plug (82%, long term 62%)
Locking plate (73%)
Distractible titanium cage
polyetheretherketone (PEEK) cage with locking plates
Traction screw with locking plates
Direct decompression (4)
single static ventral +/- dynmaic
review short term uscess 80%, recurrenc2 20%
difference between tehcnique outcomes??
Indirect (6)
all have problems
goals = adeute distraction and maintian longterm wit osseous fusion
most coomon complications = implant fail before fusion
ideally use distractor rather than manual
1. PMMA + Pins
single, increased failure if 2
v-slot then threaded positive profile pins, bone graft
angles: 35 C5-6, 45 C7
monocoruical screw performed similar biomehcnically
> reduced PMMA amount to reduce oeisiohageal irritation
> modifications: corticcancellous bone to distract + u-shape wire spacer
71% sucess long term
penetration risk 25-57%
6. disc arthroplasty
in humans no consensus
aim to preserve all motion to reduce ASS (no fusion)
probs:
long-term lacking, high subsidence rate + still reduce IVD mobility
What is a motion-preWhat is a motion-preserving technique for treating CSM?
What are the benefits?serving technique for treating CSM?
What are the benefits?
A technique to distract the spine while preserving moton
- Allows direct decompression
- Allows reestabishment of normal disc space with preserved motion to decrease risk of domino effect (adjacent segment disease)
–
What are some key points in the application of a PMMA plug?
How can you reduce the rates of migration?
Discectomy, leaving approx 3-5mm of dorsal annulus intact
Anchor holes in the adjacent vertebral end plates
Bone graft into ventral disc space once PMMA has hardened
A retention screw can help to prevent migration
What complications are possible with CSM treatment? (8)
15% complication rate
- Neuro deterioration (70% after continuous dorsal laminectomy, up to 42% with ventral techniques)
- Improper implant placement (25-57%) > check with CT
- Domino effect (20%) da costa 2007
with distract-stable - laminectomy membrane
- Implant failure (7.5-30%)
- Collapse of IVD
- Insufficient decompression 6/7 dobberman on PM
- Recurrence 24% (jeffery 2001)
- mortality 0-6%
What MRI findins are associated with a poorer outcome for CSM?
Spinal cord hyperintensity on T2W with concurrent hypointensity on T1W images
CSM prognosis
Post-op: cage/analgesia/ice
restrict exercise 2-3 months
physio
non-ambul (nursing/ucath/turn)
70-90% improve despite technique chosen in short term
medical success in 50%
no other factors affect outcome: duration, non-ambl
Sx may not alter longterm outcome, though does appear to consistently improve outcome
MST 36mth (de costa) if med or sx - prob due to progressive nature of the dz despite Tx (therefore deterioeation not necessarily due to sx fail)
*more studies required on long-term, with increased power and more objective
caution interpreting results of any Tx
What are extradural synovial cysts?
Cysts originating from the zygapophyseal joints of the vertebral articulations and are located extradurally.
Divided histologically into
- synovial cysts (epithelial lining)
- ganglion cysts (mucinous degeneration or articular cartilage)
What is the main predisposing factor of extradural synovial cysts?
Degenerative changes of the zygapophyseal joint
What are the treatment options for extradural synovial cysts?
Dorsal laminectomy
Hemilaminectomy
Percutaneous cyst rupture with corticosteroid injection (humans)
Must remove enture cyst and periarticular soft tissues to minimize risk of recurrence
CS cysts
Thoracolumbar synovial cysts: These cysts are seen in middle-aged and older large-breed dogs and usually cause unilateral spinal cord compression.
caudal lumbar vertebral column/lumbosacral synovial cysts: Affected dogs are typically large-breed, middle-aged or older dogs, although lumbar cysts have also been reported in a 2-year-old Boxer.87,231 Clinical signs include pelvic limb lameness or weakness
cyst Dx
how look on MRI?
A presumptive diagnosis of extradural synovial cysts can be achieved via imaging, with MRI being the imaging modality of choice.
well-circumscribed extradural mass(es) on one or both sides of the vertebral foramen.
hyperintense in T2W
hypointensity, isointensity, or hyperintensity in T1W (depending on cyst contents)
CSM: traction resposnive
what did da costa study say? 3 problems?
dynamic
compression that improves with with traction
usually due to releif of compresion by AP or ligament, therefore inctease dural tube diameter
expect to benefit from distraction-stabilisation sx
de costa: MRI suggest that almost any compression whether static or dynamic will improve with traction
>not based on evidence-based criteria
>traction not standardised
>cocept highly subjective according to current literature
Surgical management and long-term outcome of dogs with cervical
spondylomyelopathy with an anchored intervertebral titanium device
King 2020
50% subsidence
90% initially, but then 70% longer term, with 2 euthed
10 dogs with (DACSM) and 1 dog with osseous-associated
Design Retrospective case series.
myelography with or without advanced imaging , Sx with C-LOX implant.
Long-term follow-up was available in 8/11 with owner questionnaire. 2 euth.
Seven (70%) dogs with DACSM
improved neurologically but had persistent neurological dysfunction
Postoperative radiographs revealed cage subsidence in
5 (50%) dogs, and loosening of a single cranial or caudal vertebral
body screw in 4 (40%) dogs with DACSM.
Five major complications occurred in 4 (40%) patients
Adjacent segment disease
occurred in three dogs (30%) with DACSM
conclusion: comparable to previously
described distraction–stabilisation techniques.
Association of neurologic signs with high-field MRI findings
in 100 dogs with osseous-associated cervical spondylomyelopathy
Marília de Albuquerque Bonelli 2021
prospective study found durastion/worsneing over 1.9 months > not confirmed in this study
retrosepctive study
weremale (75%) with chronic presentation (89%), more than one site
of spinal cord compression (78%) and foraminal stenosis (91%).
Dogs with multiples sites of spinal cord compression were more likely to have severe spinal cord compression
There was correlation (weak) between neurologic grade and severity of spinal cord compression
disc degeneration was seen in 80%
of dogs.
extradural intraspinal cysts (25%) > partially responsible for spinal cord
and/or nerve root compression
majority of dogs with severe spinal cord compression and T2Wspinal cord hyperintensity were younger than 3 years of age.
> older dogs not have more severe imaging changes or clinical signs
Comparison of Cervical Stabilization with
Transpedicular Pins and Polymethylmethacrylate
versus Transvertebral Body Polyaxial Screws with or
without an Interbody Distractor in Dogs
Marinho 2022
compare the biomechanical properties of
caudal cervical vertebral stabilization using bicortical transpedicular pins with polymethylmethacrylate
(PMMA) versus transvertebral body polyaxial screws and connecting
rods with or without an interbody distractor.
Study Design Ten canine cervical vertebral columns
Stabilization obtained with transvertebral body polyaxial screws was
comparable to that from the well-established bicortical pins/PMMA construct. Association
of an intervertebral distractor did not change AROM of the polyaxial screw
constructs.
Instrumented cervical fusion in nine dogs with caudal
cervical spondylomyelopathy
Bok 2019
Dogs have a
natural lordotic position that increases the risk of ventral extrusion
of intervertebral implants from shearing forces, and ventral
fixation and stabilization are often required to prevent
ventral dislodging of the intervertebral implants.
Study design: Short case series.
Animals: Nine large-breed dogs.
Methods: Medical records of dogs treated
surgery objective was spinal distraction by implantation of a
SynCage and fixation with two Unilock plates
According to CT, the volume of bone (mean ± SD) through the cage was 79.5% ± 14.3% Subsidence was seen in one of nine dogs.
Implant failure was evident in four dogs, and plates were removed in two dogs.
In seven of nine dogs, infraclinical pathology was observed in adjacent segment
survival 9-51 months (average 27mths) > several dies from other dz
Short-Term Clinical and Radiographical Outcome
after Application of Anchored Intervertebral
Spacers in Dogs with Disc-Associated Cervical
Spondylomyelopathy
Deborah Rohner1
Objectives the short-term outcome of (C-LOX) for the treatment of disc (DA-CSM) in dogs
Materials and Methods Neurological signs, as well as diagnostic imaging performed pre-, immediately postoperatively, and after 6 weeks and 3 months were assessed.
Results Thirty-seven cases. Outcome at 3monthswas available in 25 dogs; improvement of neurological status was documented in 25/25 cases.
The most common postoperative complication was screw loosening and/or breakage (n 22), followed by subsidence (n ¼ 15). Four dogs required revision surgery.
Clinical Significance
short-term clinical improvement in 33/37 treated cases. The high incidence of screw loosening > new
locking system was required. The C-LOX device seems to be a
valuable alternative
The absence of a control group > impossible to directly compare the C-LOX implant to other existing distraction–fusion techniques
Jeffery and colleagues found an 80%
short-term success of DA-CSM surgery in their meta-analysis,
butapproximately 20%recurrence inlong-termfollow-up.15,29
Ultrasound-guided paravertebral perineural
glucocorticoid injection for signs of refractory
cervical pain associated with foraminal intervertebral
disk protrusion in four dogs
Wolf 2021
1mg/kg injections - successful in 3 of 4 dogs. Dog which was unsuccessful was unclear if disc protrusion was the cause of the lameness. Successful cases required 2-3 injections prior to long term resolution of signs
Biomechanical effects of a titanium intervertebral cage as a
stand-alone device, and in combination with locking plates
in the canine caudal cervical spine
Rick Beishuizen
evaluate the change in ex vivo biomechanical properties of the
canine cervical spine, due to an intervertebral cage, both as a stand-alone
device and in combination with plates
Although the anchorless stand-alone device has
successfully and safely been used in vivo in a limited
number of clinical cases, more research is necessary
regarding the in vivo biomechanical consequences in the
long term, the risk of cage migration, non-union and subsidence
in the long term, and the biomechanical effects
of bony ingrowth through the cage.
Cervical Distraction-Stabilization Using an Intervertebral Spacer Screw and String-of Pearl (SOP™) Plates in 16 Dogs With Disc-Associated Wobbler Syndrome
Solano 2015
Application of the FITS device in combination with 2 ventral SOP™ locking plates and autogenous cancellous bone graft was associated with excellent outcomes in dogs treated for DAWS in this small case series
Fifteen of the 16 dogs had significantly improved neurologic status (P =.01) at 6 weeks. Seven of the 16 dogs were examined at 24-36 months with 6 considered normal and 1 had mild ataxia. Postoperative radiographic intervertebral distraction was significant (P = .01). Radiographic bridging was recorded in 10/16 dogs at 6 weeks and in 7 dogs available for follow-up at 5-36 months. Computed tomography in 3 dogs at 24-36 months and postmortem with histology in 1 dog confirmed bone-bridging. Complications were not considered clinically significant and included implant loosening (2 dogs, both single plates) and minor end-plate subsidence (8 dogs).
