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)