cervical arthroplasty a non fusion technique for daws in dogs - power point - august, 2015 -...
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ECVS 24th Symposium July 4th 2015 - Berlin, Germany, Europe
Cervical Arthroplasty: A Non-Fusion Technique for Disc Associated
Wobbler Syndrome in dogs
Copy of this presentation: Wobblersyndrome.com
under the menu’ tab: “For Veterinarians”
Filippo Adamo, DVM, Dipl. ECVN East Bay Veterinary Specialists – Walnut Creek, CA
ECVS Surgery Symposium July 2-4, 2015
Disclosure
I designed and developed the medical device included in this presentation.
Currently involved in the distribution trough Applied Veterinary Technology, LLC
Goals:
Preserve motion after neural decompression while providing distraction and stability
Potentials:
May prevent “domino lesions”
Advantages:
Treatment of multiples adjacent & not adjacent spaces
Cervical Disc Arthroplasty (CDA)
Indications:
Disc Associated Wobbler Syndrome
Phase 1.DESIGN
Madison, WI 2003
Phase 2.IN VITRO BIOMECHANICAL STUDY Adamo, Kobayashi et al. Vet Surgery 2007
4 Groups of 6 cervical spines (C5-C6)a) Arthroplasty,
b) Ventral Slot,
c) Pins+PMMA fixation,
d) and normal spine
The artificial disc was better ableto mimic the behavior of intactspine compared with ventral slotand Pin+PMMA groups.
History
Phase 3. Pilot clinical study in 2 client-owned dogs with
DAWS
Titanium alloy
Results Follow up to 3½ years post-op
Both dogs died for unrelated neurological diseases
MRI re-check 2 years post-op No evidence of compression at the treated
and adjacent sites
Conclusions
Cervical arthroplasty was well tolerated and provided excellent outcome in both dogs
Warranted further study: Large number of patients
Longer follow-up
Adamo JAVMA, 239(6), 2011
Cervical Disc Arthroplasty using the Adamo Spinal Disc™ in 33 dogs
affected by Disc Associated Wobbler Syndrome
at Single and Multiple Levels.
In preparation to be Submitted to JAVMA
Study Authors
F Adamo, DECVN
East Bay Vet Specialists – CA
R Da Costa, DACVIM (Neurology)
The Ohio State University – OH
R Kroll, DACVIM (Neurology)
VCA Northwest Vet Specialists – OR
C Giovannella, DACVIM (Neurology)
Gulf Cost Vet Neurology/Neurosurgery – TX
M Podell, DACVIM (Neurology)
Chicago Vet Specialty Group – IL
P Brofman, DACVIM (Neurology)
Veterinary Specialty Care, SC
A Multi-Center Prospective Study
To evaluate:a) the immediate post-operative recoveryb) the short-, intermediate- and long term follow-up
of dogs with one level and multi-level disc-associated-wobbler-syndrome (DAWS) treatedwith cervical disc arthroplasty (CDA).
Objectives
Material & Methods
Implant: Similar to that in the pilot study but with several modifications
1st generation- Ball Titanium
- Dual Ac Etch
2nd generation- Ball in PEEK
- Thinner size
- Dual Ac. Etch
3rd generation- Hydroxyapatite Coating
Calcium Phosphate complex
Porosity
Osteoconduction
8.5 mm
Spinal Disc 2nd & 3rd Gen.
Internal surfaces
Convexity is PEEK
(PolyEther Ether Ketone)
Thermoplastic polymer
Decreases friction
Prevent metallic debris
from a metal to metal joint
Concavity is titanium
Ball and socket
Patent: US 8,496,707 B2
External surface
Convex To resemble natural
concavity of vertebral end plates
Spinal Disc 2nd & 3rd Gen.
Concentric grooves + Central notch To provide “grip” & to prevent implant migration
Implant Design Modification
7 different disc sizes
Set of dedicated tools
Threaded pins
• to hold the assembled prosthesis
Dedicated tools
Thick end
Parallel channels to hold the assembled prosthesis during implantation
Thin end
Slotted to remove the pins after implantation
Barrel Holder – Double function
Dedicated tools
Sizing Probes
• Resemble at each end the shape of either mthe S, M, or W disc size
•To probe/test the disc space during nburring, before final disc implantation
Dedicated tools
Small burr
• To clean end-plates and begin creating concavity
Large burr
• matches the external disc convexity
• To facilitate implant accommodation by the disc space
Large burrSmall burr
Two dedicated burrs
Dedicated tools
20 degree angle attachment for the Surgairtome
To facilitate working at an angle parallel to the disc space during burring
Particularly useful at C6-C7 (and C7-T1 !!)
Dedicated tools
Caspar Cervical Distractor
• To maintain vertebral distraction during implantation
• To allow visualization through the disc space to the dorsal longitudinal ligament
Dedicated tools
Disc space prepared for the implant
Vertebral end plate
Dorsal Long. Lig.
CDA video clip – Implant Placement
Sample population: First 33 clients-owned dogs w/ over 2
mo. history of DAWS
Diagnosed by MRI or CT myelo
Weight over 23 kg, but one (12.2 Kg)
Neurologically and radiologically evaluated
Prior to surgery
Shortly after surgery
within 24 hrs
At 2 wks & 3, 6, 12 & 24 mo. after surgery
Including Criteria
Total = 50 disc sites treated
Single, two and three level lesions
Neurological Assessment
Grade 0 to 6
De Decker, et al. JAVMA 2012; 240:848–857
C3C4
C5C6
Material and Methods
0: No apparent neurological deficits
1: Cervical hyperesthesia w/o deficits
2:: Hind limb ataxia w/o visible paresis
3: Hind limb ataxia with paresis &
no appreciable forelimb ataxia
4:: Ambulatory tetraparesis: broad-
based ataxia hind limbs & choppy
gait forelimbs (“two engine gait”)
5:: Non-ambulatory tetraparesis: able
to stand/walk few steps before collapse
6: Tetraplegia
Optimal
Implant well centered in the disc space on lateral & VD views
Sub-optimal
Off midline on VD
Inadequate
Not seated in center of the disc space on lateral view
Inadequate position
Implant Position
Relative Distraction ratio (RDR): Ratio between post-op and pre-op
width at the treated space
Adequate / Ideal*
RDR > 1.7 and < 2
* Equivalent to a
distraction of 2-3 mm
Under distraction
RDR < 1.7
Over-distraction
RDR > 2
Distraction
C7C6
C5
C7C6
C5
Pre-op
Post-op
Ventro-flexion
Dorsi-flexion
Neutral
Mobility
Distance between dorsal and ventral edge of the 2 faces of the implant in neutral and stressed views
Present
Not detectable
2 years post-op when possible
As needed, in the event of recurrence of clinical signs
MRI re-evaluation
Results
Breeds: 17 Doberman Pinchers (50%)
3 Dalmatians
2 Labrador
2 Bernese Mountain dog
1 Standard Poodle
1 Weimeraner
1 Boxer
1 Greyhound
5 Mix
Sex: 21 M; 12 F
Age: 4 - 13 y; Mean 8.3 y
27% over 10 y old
Single level: 19 dogs
C6-C7 (13 dogs)
C5-C6 (5 dogs)
C3–C4 (1 dog)
Two levels: 10 dogs
C5-C6 & C6-C7 (8 dogs)
C4-C5 & C5-C6 (1 dog)
C3-C4 & C5-C6 (1 dog)
Lesion Localization
Three levels: 3 dogs
C3-C4, C5-C6 & C6-C7 (2 dogs)
C2-C3, C5-C6 & C6-C7 (1 dog)
TOTAL: 50 Spaces treated
C6C7
C3 C4
C5C6
C3C4
C5
C6
Inadequate position
Immediate Post-op Radiographs
Implant position:
• Optimal (42 sites)
• Sub-optimal (7 sites)• Off midline on VD
• Inadequate (1 sites)• Improper technique Excessive burring of caudal
endplate immediate subsidence
Caudal subsidence
Distraction:
• Over-distraction (15 sites)• Mostly with 1st generation (thicker)
implant
• Adequate distraction (34 sites)• Mostly with 2nd & 3rd generation
(thinner) implant
• Under-distraction: (1 site)• Improper technique
Excessive burring of caudal endplate – immediate subsidence
Immediate Post-op Radiographs
Distraction:
Minor Subsidence: Distraction lost
compared to immediate post-op, but maintainedwhen compared to pre-op
All sites
More pronounced with 1st generation (thicker) implant
Less pronounced with 2nd and 3rd generation (thinner) implant
Severe Subsidence Distraction lost compared to pre-op
7/50 sites (14%)
Serial Radiographic Assessment
Mobility Decreased or not detectable over time in the
majority of patients. Maintained at 2 wks post-op in 88% of 24 dogs examined
Maintained at 6 mo post-op in 23% of 14 dogs examined
Maintained at 9 mo post op in one dog
Maintained at 3 years post-op in one dog
♬ In 7 dogs where dynamic study was performed immediately after surgery: mobility although expected was not detectable in 5 out of 10 treated spaces
in 3 dogs was later detectable on the serial follow-ups.
No Implant migration
No Implant infection
Serial Radiographic Assessment
Ventro-flexion
Dorsi-flexion
3 dogs: 7-24 mo post-op
Osteophites or Heterotopic Ossification.
Didn’t affect the clinical status
1st and 2nd generation implant
3 dogs: 24-36 mo post-op
No signs of disc degeneration or compression at treated and adjacent sites
1 dog: 6 wks post-op
Spinal compression secondary to immediate subsidence
Improper technique
Improved with single dorsal decompression
MRI Re-assessment: 7 dogs
C3-C4 C5-C6
C5 C6 C7
C5-C6 6 wks post – op
C6 C7*
In all dogs the implant didn’t affect the spinal cord visibility
Post-op recovery time
Immediate in all dogs
Neurological status unchanged compared to pre-op status in all dogs
Post-op hospitalization time *
5 dogs: Discharged same day
26 dogs: 1- 3 days
2 dogs: 4 - 5 days
Based on the severity of the neurological status pre-surgery
Clinical Assessment
Follow-up: Mean 24 mo, (range 2 wks - 42 mo)
21 dogs still alive
12 dogs deceased
9 for non-neurological diseases
3 euthanasia: insufficient improvement or complications
Patient Outcome 91% have shown improvement of at least 1+
neurological grade Satisfactory to Excellent: 30 dogs
Unsatisfactory: 1 dog
Poor: 2 dogs
Better Outcome: mild and short duration of signs on presentation
Worse Outcome: chronic non-ambulatory tetraparesis + extensor rigidity of front legs not resolving under general anesthesia
No Domino lesions during the observation period
Patch: 6 y old MN Dalmatian 6 mo ambulatory tetraparesis
worsening 2 mo prior to presentation
Complications and Poor Outcome
Complications
Vertebral fissure fracture during distraction: 2 dogs
Improper Caspar pins placement
+/- excessive distraction with Caspar Distractor
Did not affect the outcome
Immediate subsidence: 1 dog
Improper technique: over-burring.
Surgical revision with dorsal laminectomy
Regained improvement
Subsidence: 7/50 disc spaces
Too thick and too narrow discs
Except for 1 dog, did not affect the outcome
Improper technique
Complications
Vertebral Axial Compression fracture: 1 dog
Nikkie Sheltie Mix, F, 12.4 y old,
29 lb = 12.2 kg
History: 4 years ambulatory ataxia,
6 month prior to referral non ambulatory tetraparesis withextensor rigidity all 4 legs, not resolving under anesthesia
Overdistraction RDR 3.2 (normal > 1.7 and < 2)
2 weeks post-op: Declined to non-ambulatory tetraparesis; Intense cervical pain; Suspected Axial compression fracture C6 + Ventral implant
migration Euthanasia - no histopathology
2 weeks post-op
Pre-op
Immediate Post-op
C5 C6 C7
• What went wrong?• Dog’s size too small: 12.2 Kg• Over-distraction
Poor patient selection
Poor Outcome2 dogs
Chow Mix, F, 13.5 y old
Doby, M, 12 y old
History
8-14 months progressive non ambulatory tetraparesis
Severe extensor rigidity all 4 legs, not resolving under anesthesia
Outcome:
Dog 1 (Chow): Euthanized 8 mo. after surgery d/t insufficient
improvement
Dog 2 (Doby): Neuro score improved only from 6 to 5
• What went wrong?• Neurological signs too severe • Irreversible spinal cord damage
Poor patient selection
Pierce Simon
Advantages of CDA
Less invasive than traditional surgeries
Rapid post-surgical recovery
Can be performed on a out-patient basis
Treatment of multiple lesions at adjacent or non-adjacent sites
Prophylactically for “Incipient lesions”
May prevent “Domino lesions”
Spinal cord decompression & “dynamic stabilization”
C7C6
C5
Immediate relief of radicular pain and vascular compression at the intervertebral foramina
Enable MRI re-assessment
for complications
for long term re-assessment of domino lesions
Other Benefits
C6 C7*
Disadvantages – Limitations
Concurrent Dorsal spinal compression
The possible decrease of distraction may exacerbate the dorsal compression
It might be necessary to combine CDA with dorsal decompression at the affected site
Not good candidate for CDA
< 23 Kg
Too advanced neurological status
Severe front legs extensor rigidity not resolving under general anesthesia
Conclusions
CDA using this prosthesis appears to be safe and effective
Suitable for medium and large breed dogs
Rapid post-surgical recovery
Ideal for treating multiple levels
Not technically difficult and easy to master
May prevent “Domino Lesions”
Case selection, Early Intervention and Correct execution of the surgical technique may be critical factors for the outcome
“Case selection is King, …. technique is the Prince”
number 6 of the most commonly cited attributes of a “great” surgeon!
Dr. Zelman column
Currently in use
4th Generation Spinal Disc™
Thinner implants: 8.3mm
To avoid over-distraction
To allow implant positioning along the natural angle of disc space
Additional wider & taller sizes
S1, M1, M2, WT1, WT2, + WL1 & WL2
To increase contact surface implant/vertebral endplate To decreasesubsidence
Two External Layers of Coating:
Commercial Pure Titanium (CPTi):
To create sponge porosity
HA
To promote bone/implant incorporation
CPTi + HA
Future Directions
5th Generation Spinal Disc™
3 mo. post-op
4th practical CDA Course
November 5, 2015
Las Vegas, Oquendo Center
Program: Wobblersyndrome.com
Event Coordinator:
Nancy Kroll: [email protected]
Questions
Contact:
Filippo Adamo, DVM, DECVN
East Bay Veterinary Specialists
Walnut Creek – California
Phone: 925.937.5000
Wobblersyndrome.com