PF Adamo, G Burns PF Adamo, G Burns Montreal, CA, ACVIM June 2009 - - PowerPoint PPT Presentation

CERVICAL ARTHROPLASTY CERVICAL ARTHROPLASTY IN DOGS WITH DISC ASSOCIATED CAUDAL IN DOGS WITH DISC ASSOCIATED CAUDAL CERVICAL SPONDYLOMYELOPATHY AND CERVICAL SPONDYLOMYELOPATHY AND CERVICAL DISC HERNIATION. CERVICAL DISC HERNIATION. PRELIMINARY STUDY IN TWO CASES PRELIMINARY STUDY IN TWO CASES

PF Adamo, G Burns PF Adamo, G Burns

Montreal, CA, ACVIM June 2009

Objectives Objectives

1.

• 1. To evaluate in dogs w cervical disc

To evaluate in dogs w cervical disc diseases the efficacy of an artificial disc diseases the efficacy of an artificial disc designed for the dog cervical spine designed for the dog cervical spine Evaluation Evaluation

a) a) Implant migration Implant migration b) b) Ability to maintain distraction over time Ability to maintain distraction over time c) c) Mobility at the treated vertebral unit Mobility at the treated vertebral unit

Two endplates Stainless steel

• a. In the center of inside surface of each endplate respectively:

i. Concavity and convexity acts like a ball and the socket.

• b. External surface of each endplate:

i. convexity to prevent implant migration

• ii. concentric grooves to allow bone in growth into the implant.

Phase 1: Phase 1: design

design

Patent # US2008/0306597 A1 Patent # US2008/0306597 A1

Two breakable fins attached

to the dorsal portion of each end plate: TO FACILITATE HOLDING AND PLACEMENT OF THE IMPLANT

Breaking point of the fins at the attachment to each end plate. Once the disc is implanted the fins are detached from the prosthesis by twisting each fin along its long axis.

1) 4 Groups of 6 cervical spines 2) Treated Vertebral Space C5-6 3) Prosthesis, Ventral Slot, Pin+PMMA fixation, and normal spine

Axial compression Flexion/Extension Lateral bending Torsion

Phase 2: Phase 2: in vitro

in vitro biomechanical testing biomechanical testing

• In vitro Biomechanical Comparison of Cervical Disc Arthroplasty, Ventral Slot Procedure,

and Smooth Pins with Polymethylmethacrylate Fixation at Treated and Adjacent Canine Cervical Motion Units

Adamo, Kobayashi et al. Vet Surgery 2007

• Overall the artificial disc was better able to

Overall the artificial disc was better able to mimic the behavior of intact spine compared mimic the behavior of intact spine compared with ventral slot and Pin+PMMA groups. with ventral slot and Pin+PMMA groups.

Effect of cervical level on the mechanical properties of each group (1-way-ANOVA) and effect of group at each cervical level (repeated measure ANOVA). Difference significant at a probability level of 95% (p<0.05).

Phase 3: Phase 3: pilot clinical study pilot clinical study

• Two owned client dogs with cervical disc disease

Two owned client dogs with cervical disc disease

• Weight

Weight

• no less then 50 lb (22 kg)

no less then 50 lb (22 kg)

• Diagnosis:

Diagnosis:

• history, clinical signs, confirmed on MRI

history, clinical signs, confirmed on MRI

• MRI: 1.5 T magnet and cervical spine array coil

MRI: 1.5 T magnet and cervical spine array coil

• T1,T2 weighted images, Proton density, Flair

T1,T2 weighted images, Proton density, Flair

• Sagittal and transverse plane + sagittal traction

Sagittal and transverse plane + sagittal traction

• MDB:

MDB:

• CBC, Chemistry panel and Thoracic radiographs

CBC, Chemistry panel and Thoracic radiographs

• Consent form and study participation agreement

Consent form and study participation agreement

Including criteria

Titanium alloy (Ti 6AI-4V ELI)

Treatment Treatment

• Spinal decompression by Ventral slot +

Spinal decompression by Ventral slot + Implantation of the prosthesis Implantation of the prosthesis

• 6 wks neck brace + restricted activity

6 wks neck brace + restricted activity Follow Follow-

• up

up

• Serial X

Serial X-

• rays

rays

• Time 0, 2

Time 0, 2 -

• 6 wks, 3

6 wks, 3 – – 6 months and 1 year 6 months and 1 year

• VD, LL, stress views (traction, dorso/ventral flexion)

VD, LL, stress views (traction, dorso/ventral flexion)

Rescue plan Rescue plan

• migration of device, radiological signs of infection,

migration of device, radiological signs of infection, and persistent neurologic signs, and persistent neurologic signs,

• a course of NSAID +/

a course of NSAID +/-

• antibiotic therapy

antibiotic therapy

• removal of the prosthesis w conversion to standard

removal of the prosthesis w conversion to standard ventral slot if medical management not effective ventral slot if medical management not effective

• Sizes of the prosthesis. 6 different sizes.

Disc A (mm) B (mm) C (mm) D (mm) E (mm) sm 1 9.0 10.5 7.4 6.3 4.5 sm 2 10.5 10.5 7.4 7.0 5.2 sm 3 12 10.5 7.4 7.8 5.9 Med 1 9.0 11.3 8.5 6.3 4.5 Med 2 10.7 11.3 8.5 7.1 5.4 Med 3 12 11.3 8.5 7.8 5.9

A: assembled width; B: outside diameter; C: width of the flat; D: thickness of the convex part; E: thickness of the concave side.

Implant Size Selection:

• Dog 1

Dog 1

• 4 y old M intact Doberman

4 y old M intact Doberman Pincher, 31 kg Pincher, 31 kg

• Acute onset cervical pain &

Acute onset cervical pain & ataxia ataxia

• Neuro

Neuro-

• exam

exam

• Cervical pain, ataxia

Cervical pain, ataxia

• MRI:

MRI:

• Acute myelopathy 2

Acute myelopathy 2ary

ary to

to C6 C6-

• C7 Disc Herniation

C7 Disc Herniation

• Dog 2

Dog 2

• 8 y old MN Labrador Mix, 23 kg

8 y old MN Labrador Mix, 23 kg

• 4 months progressive ataxia/tetraparesis

4 months progressive ataxia/tetraparesis

• Neuro

Neuro-

• exam:

exam:

• Cervical pain, amb. tetraparesis, CP deficits all 4 limbs

Cervical pain, amb. tetraparesis, CP deficits all 4 limbs

• MRI:

MRI:

• Chronic myelopathy 2

Chronic myelopathy 2ary

ary to C5

to C5-

• C6 disc disease

C6 disc disease

• + dorsolateral encroachment of the spinal cord

+ dorsolateral encroachment of the spinal cord

Surgical technique

Ventral slot and spinal decompression

Placement of Caspar cervical retractor

• Maximal distraction
• Milling each vertebral end-plate with burr to

create a concavity shape

• Placement of the prosthesis

Maximal DISTRACTION

Distraction released

Fins are twisted and de-attached from the implant

The Caspar retractor is removed before closure

• time 0: immediate post

time 0: immediate post-

• op
• p

Dog 2 Dog 1

• 2 weeks post

2 weeks post-

• op
• p

Dog 2 Dog 1

Linear traction Neutral Linear traction Neutral

• 3 months post

3 months post-

• op
• p

Dog 2 Dog 1

Neutral Linear traction Linear traction Neutral

• 6 months post

6 months post-

• op
• p

Dog 1

Dorso-flexion Neutral Linear traction

Dog 1

Ventro-Flexion

• 6 months post

6 months post-

• op
• p

Dog 2

Neutral Linear traction Dorso-flexion Ventro-Flexion

Dog 2

• 12 months post

12 months post-

• op
• p

Dog 1

Neutral Linear traction Dorso-flexion Ventro-Flexion

Dog 1

Results Results : clinical outcome : clinical outcome

• Dog 1

Dog 1

• Complete neurologic recovery, with

Complete neurologic recovery, with two occasional episodes of cervical two occasional episodes of cervical pain during the first 2 wks post pain during the first 2 wks post-

• op,
• p,

resolved with NSAID. resolved with NSAID.

• up to 12 month re

up to 12 month re-

• check:

check:

• Neurologic normal

Neurologic normal

• Dog 2

Dog 2

• Improved during the first 2 months

Improved during the first 2 months post post-

• op, less ataxic and less CP
• p, less ataxic and less CP

deficits. deficits.

• 6 month post

6 month post-

• op:
• p:
• mild ataxia without CP deficits except for

mild ataxia without CP deficits except for mild delayed in hopping reaction on left mild delayed in hopping reaction on left front limb front limb

Results: Results: X X-

• Rays

Rays

• Immediate post

Immediate post-

• op X
• p X-
• rays:

rays:

• implant was well seated in the slot providing

implant was well seated in the slot providing good distraction. good distraction.

• In all post

In all post-

• op X
• p X-
• rays:

rays:

• distraction was maintained with no evidence of

distraction was maintained with no evidence of ventral bridging spondylosis at the treated ventral bridging spondylosis at the treated site. site.

• Not migration and not signs of infectious

Not migration and not signs of infectious

• Mild degree of mobility at the treated site 1 year

Mild degree of mobility at the treated site 1 year post post-

• op in Dog 1, which decreased over time
• p in Dog 1, which decreased over time

Conclusions Conclusions

• Cervical arthroplasty was well tolerated in

Cervical arthroplasty was well tolerated in both dogs, maintained distraction and both dogs, maintained distraction and prevented bridging spondylosis. prevented bridging spondylosis.

• Limitations:

Limitations:

• Number of cases treated

Number of cases treated

• Different type of discs cervical diseases treated

Different type of discs cervical diseases treated

• This procedure is promising and warrants

This procedure is promising and warrants further study further study

Latest Updates Latest Updates

New bur custom made to match the convexity shape of the external surface of the implant Barrol-holder for handling the prosthesis during implantation. The two fins have been replaced by two octagonal pins screwed in each shelve of the implant. The pins are easily unscrewed from the prosthesis after implantation

Acknowledgments Acknowledgments

University of University of Wisconsin Wisconsin -

• Madison

Madison

• School of Veterinary Medicine

School of Veterinary Medicine

• Intramural Grant

Intramural Grant

• Dept. of Astrophysics
• Dept. of Astrophysics -
• machinery

machinery shop shop

• First prototype

First prototype

• Dept. of Biomechanical Engineering,
• Dept. of Biomechanical Engineering,

Human Hospital. Human Hospital.

• Biomechanical testing
• Hirohito Kobayashi

Hirohito Kobayashi

• Ray Vanderby

Ray Vanderby

• Biomechanical testing

Biomechanical testing

• Mark Markel

Mark Markel

• Statistical analysis

Statistical analysis

• Bay Area Vet Specialists

Bay Area Vet Specialists

• First clinical study

First clinical study

East Bay Area Veterinary Specialists Sequoia Animal Hospital

• On going clinical study