Cervical Disc Replacement, Cervical Disc Arthroplasty, Adjacent Segment Disease, Recent Advances, Discusses about the cervical disc replacement or arhroplasty for cervical spine disease
requires certain indication such as level from c3-c7, single or maximum 2 level, Mechanical loading of disc cause of degeneration
Treatment: Conservative magment to surgery +/- fusion
fusion associated with ASD, pseudoarthrosis, donor site mobility, restricted motion, altered physiology Depends on implant based parameters:
wear
material
kinetics
Depends on Patient based parameters:
Age, Sex, gender
Weight, BMI
Depends on Surgeon based parametes:
Precision, skill
soft tissue and bone handling
single-level,
myelopathic, or radiculopathic cervical disease
between C3 and C7
All of above in symptomatic patient
failing 6 weeks of conservative management
Osteoporosis
Significant kyphosis
Instability, greater than 50% loss of disc height
Facet arthropathy
Ossification of PLL
Inflammatory arthropathy
Multilevel disease
Translation > 3.5 mm on flexion extension X-rays
ACDF with CDR:
for multilevel cervical Degen Disc Disease(DDD)
Combination of fusion and nonfusion tailored to each level
allowing segmental motion preservation at index levels
minimizing hypermobility at adjacent levels
Composite:
two metal endplates with poly in between, Ball and socket
Viscoelastic:
with or without endplates
Mechanical:
A mechanical artificial disc is usually comprised of two articulating pieces, all of which are the same material (e.g. metal) or a composite metal and ceramic
Doesnot replicate mechanics of spine
Simple design
based on concept of synovial joint arthroplasty(hip, knee)
accelerated dgeneration of surrounding structure:
facets, UV joint, ligaments
Prodisc-C® Cervical Disc:
2 cobalt chromium endplates and
1 ultra-high molecular weight polyethylene inlay
Inlay technically separate from the endplate,
but it locks into the lower metal, function as a single after installation
Upper endplate has a highly polished divot
plastic dome fits and moves
metal surfaces coated with a titanium plasma spray
helps hold the artificial disc in place and promote bony growth.
Endplate sandwiched:
eg: Bryan Cervical disc
polycarbonate urethane nucleus
rests between two titanium alloy “shells”
Saline innucleus adds compression to disc
Prestige cervical disc:
made of a titanium ceramic composite and titanium carbide
“ball and socket” design,
This design and composition make highly durable and give spine outstanding motion at one- and two-disc levels in cervical spine
Endplates each have two low profile keels to help secure it to bone
Artificial disc permits spine to flex, extend, side bend, and rotate while maintaining alignment, height, and curvature
Unconstrained:
Excess ROM, cost of instability
Semiconstrained:
Constrained:
Limits movement via Keel
pressure on Facet joints
Stable
3mm disc space required prior to CDR
Avoid overstuffing of implant:
Facet joint distraction,
2. Introduction:
• Mechanical loading of disc cause of degeneration
• Treatment: Conservative magment to surgery +/- fusion
• fusion associated with ASD, pseudoarthrosis, donor site
mobility, restricted motion,
altered physiology
This is where Cervical Disc Replacement(CDR) comes into play
3. Success of cervical disc replacement
• Depends on implant based parameters:
• wear
• material
• kinetics
• Depends on Patient based parameters:
• Age, Sex, gender
• Weight, BMI
• Depends on Surgeon based parametes:
• Precision, skill
• soft tissue and bone handling
5. Indication:
• single-level,
• myelopathic, or radiculopathic cervical disease
• between C3 and C7
• All of above in symptomatic patient
• failing 6 weeks of conservative management
6. Contraindication
• Osteoporosis
• Significant kyphosis
• Instability, greater than 50% loss of disc height
• Facet arthropathy
• Ossification of PLL
• Inflammatory arthropathy
• Multilevel disease
• Translation > 3.5 mm on flexion extension X-rays
7. Hybrid Surgery
• ACDF with CDR:
• for multilevel cervical Degen Disc
Disease(DDD)
• Combination of fusion and nonfusion
tailored to each level
• allowing segmental motion preservation at
index levels
• minimizing hypermobility at adjacent levels
8. Types of implant: Based on material
• Composite:
• two metal endplates with poly in between, Ball and socket
• Viscoelastic:
• with or without endplates
• Mechanical:
• A mechanical artificial disc is usually comprised of two articulating pieces, all
of which are the same material (e.g. metal) or a composite metal and ceramic
9. Composite:
• Mobi-C:
• cobalt chromium molybdenum alloy
• Endplates coated with a fine layer of
titanium and
hydroxyapatite to promote integration with
bone
• Mobile, polyethylene bearing
• gives device and spine good ROM
SECURE-C Cervical Disc:
• Three separate pieces: a polyethylene inner core
that is inserted between two cobalt chromium
endplates
• permits up to ±15º motion in flexion-extension
(nodding up and down) and up to ±10º motion
in lateral bending (tilting the head from side to
side)
10. Composite
• Prodisc-C® Cervical Disc:
• 2 cobalt chromium endplates and
• 1 ultra-high molecular weight polyethylene inlay
• Inlay technically separate from the endplate,
• but it locks into the lower metal, function as a single
after installation
• Upper endplate has a highly polished divot
• plastic dome fits and moves
• metal surfaces coated with a titanium plasma spray
• helps hold the artificial disc in place and promote bony
growth.
11. Disadvantages of first generation:
• Doesnot replicate mechanics of spine
• Simple design
• based on concept of synovial joint arthroplasty(hip, knee)
• accelerated dgeneration of surrounding structure:
• facets, UV joint, ligaments
In saying so, first generation are the ones still preferred
12. Second generation: Viscoelastic
A) Endplate sandwiched:
• eg: Bryan Cervical disc
• polycarbonate urethane nucleus
• rests between two titanium alloy “shells”
• Saline innucleus adds compression to disc
B) No endplates:
14. Viscoelastic advantages and disadvantages
• Biological fixation
• tries to replicate spine biomechanics
• doesnot cause stress in surrounding structures
• disadvantages:
• no evidence
• poor stability
• failure
• high incidence of periprosthetic infection(C.acne)
15. Mechanical:
• Prestige cervical disc:
• made of a titanium ceramic composite and
titanium carbide
• “ball and socket” design,
• This design and composition make highly durable
and give spine outstanding motion at one- and
two-disc levels in cervical spine
• Endplates each have two low profile keels to help
secure it to bone
• Artificial disc permits spine to flex, extend, side
bend, and rotate while maintaining alignment,
height, and curvature
16. Based on design
• Unconstrained:
• Excess ROM, cost of instability
• Semiconstrained:
• Constrained:
• Limits movement via Keel
• pressure on Facet joints
• Stable
17. Surgical Technique/Pearls:
• 3mm disc space required prior to CDR
• Avoid overstuffing of implant:
• Facet joint distraction, persistant neck pain
• Anterior approach(Smith Robinson)
• Resect ALL to reach spine
• Resect IVD completely
• But do partial foraminotmy, else INSTABILITY
18. Biomechanical parameters related to CDR
• Center of rotation
• Range of motion [ROM = elastic zone
(EZ) + neutral zone (NZ)/quantity]
• stiffness (quality) and hysteresis
(quantity)
The elastic portion of the ROM is the portion nearer to the end range of movement
that is produced against substantial internal resistance. The neutral zone is in the
zone of high spinal flexibility whereas movements in the elastic zone encounter
increased internal resistance to movement.
19. COR of cervical spine
• At certain disc space in subaixal spine:
• (center of superior endplate) of inferior vertebrae in sag plane
• Coupled motion, ROM decreases with age in all 3 plane
• Flexion:
• anterior translation + axial rotation + concurrently lateral bending
• Anderst et al described instant center of rotation (ICR), which
accounts for change in location of COR about each cervical segment
as dynamic motion occurs
20. Overall COmplication
• Excess lordosis- due to fixation in extension
• Excess kyphosis: Due to fixation in flexion
• Facet joint arthropathy, Ligamentous instability
• Prosthesis subsidence into canal
• Ajacent Segment Disease
• Hypertrophic ossification
• Prosthesis related complication:
• Wear, osteolysis, periprosthetic fracture, aseptic loosening, nerve or cord
injury
21. Adjacent segment disease(ASD)
-Complication of ACDF/rigid construct
• now also known as RASP
• Radiological Ajacent Segment pathology
• cases where there is no clinical s/s
• Another entitity is CASP
• CLinical adjacent segment pathology
• associated with S/s
Risk factors for ASD:
• fusion constructs adjacent to C5 through C7
• Preexisting cervical degeneration
• Age less than 60 years at the time of ACDF
Adjacent to cervical fusion, intradiscal pressure increases by approximately 50% in the proximal adjacent level and
125% in the distal adjacent level
