Machined Allograft Interbody Spacers”
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Transcript Machined Allograft Interbody Spacers”
“Lumbar Segmental Instability”
The Role of Interbody Fusion
Role of Interbody Spacers are to provide
a means to stabilize the anterior column
Anterior column stability decreases the
motion at unstable segments and unloads
the posterior instrumentation
“Carson et al” showed a seven fold
decrease in bending moment with anterior
column support
“Lumbar Segmental Instability”
The Role of Interbody Fusion
Interbody fusion can be accomplished thru
anterior or posterior approaches
Not a Stand-Alone (requires hardware)
Each has their own advantages and
disadvantage
Posterior Interbody Fusions advantages
include: total disc excision, restoration of
disc height, enhanced foraminal
decompression, and high arthrodesis rates
“Lumbar Segmental Instability”
The Role of Interbody Fusion
Posterior Interbody fusion disadvantages
include: graft displacement, neurologic injury,
and nonunion
Anterior Interbody Fusion advantages include:
reduced operative time, reduced blood loss,
maintain posterior structures, complete
discectomy, and avoidance of scarring in the
canal
“Lumbar Segmental Instability”
The Role of Interbody Fusion
Anterior Interbody fusion disadvantages
include: second surgical approach and access
surgeon, potential vascular injury, graft
displacement, and GI and GU injury or
complication
“Lumbar Segmental Instability”
The Role of Interbody Fusion
“Patient Selection for Interbody Fusion”
Indications include the following:
spondylolisthesis to stabilize the anterior
column, pseudoarthrosis repair, recurrent disc
herniation’s and re-operations, fractures for
anterior and middle column reconstruction,
correction of deformity either scoliosis or
degenerative disc disease
“Lumbar Segmental Instability”
The Role of Interbody Fusion
Types of Interbody Allograft Spacers
available include: femoral rings, cortical
dowels, cortical ramps, and composite
cortical and cancellous bone spacers
Each have specific benefits and
disadvantages though
“Lumbar Segmental Instability”
The Role of Interbody Fusion
“Femoral Ring Allografts”
“Lumbar Segmental Instability”
The Role of Interbody Fusion
Femoral Ring Allograft Spacer’s have the
advantages of ready availability, fashion many
grafts from a single femoral shaft, size for
each level as well as shape the graft, and
reconstitute the disc height
Disadvantages include migration, anterior
placement only, less surface area for grafting
around it, small area for autograft, and loss
of full contact
“Lumbar Segmental Instability”
The Role of Interbody Fusion
“Cortical Dowels”
“Lumbar Segmental Instability”
The Role of Interbody Fusion
Cortical Dowels have the advantage of
greater fixation through threads, approach
anterior or posterior, restore disc height,
and better contact with surface of endplates
and bone
Disadvantages include less surface area for
grafting around although better than femoral
rings, limited autograft placement, less
lordotic correction, and potential for loss of
contact (L5S1)
“Lumbar Segmental Instability”
The Role of Interbody Fusion
“Cortical Ramps”
“Lumbar Segmental Instability”
The Role of Interbody Fusion
Cortical Ramps advantages include lordotic
producing, large surface area for bone
grafting, better fixation through serrations,
less migration than femoral ring, and both
anterior or posterior appraoch
Disadvantages include migration, loss of
surface contact, rotation of graft, and less
surface area for incorporation compared to
dowels or rings
“Lumbar Segmental Instability”
The Role of Interbody Fusion
“Metallic Devices”
“Lumbar Segmental Instability”
The Role of Interbody Fusion
Advantages include being metallic and not
dependent on bone availability
Available in a vast array of sizes and
shapes for the specific needs
Greater structural support
Instantaneous stability while bone graft
consolidates
Better fixation to inner space
“Lumbar Segmental Instability”
The Role of Interbody Fusion
Disadvantages include less bone ingrowth
potental
Less surface area for bone ingrowth
Not an end plate sparing: dependent on
device and insertion technique
Potential for subsidence
Potential for loss fit and migration
Re-establishment segmental lordosis
“Lumbar Segmental Instability”
The Role of Interbody Fusion
“Biomaterial Devices”
“Lumbar Segmental Instability”
The Role of Interbody Fusion
Advantages: readily available
Can be fabricated in any size and shape
Good structural stability dependent on
composite: ie. PEEK
End plate sparring: dependent on device
and technique
Re-establish segmental lordosis
Good fixation to inner space
“Lumbar Segmental Instability”
The Role of Interbody Fusion
Disadvantages: less surface area for bone
ingrowth
Potential for ingrowth less than cortical
ramps
Potential for migration
Potential for subsidence
Potential for reactive changes due to
device: ie PEEK or bioabsorbables
“Lumbar Segmental Instability”
The Role of Interbody Fusion
Maintain and/or re-establish segmental
lordosis of individual disc spaces
Re-establish disc height
Promote foraminal decompression
Eliminate rotation of the graft (fins)
Serration’s for fixation and limitation of
graft migration
Provide larger surface area for incorporation
(serration’s and fins)