Lumbar Segmental Instability The Role of Interbody Fusion zRole of Interbody Spacers are to provide a means to stabilize the anterior column zAnterior column stability decreases the motion at unstable segments and unloads the posterior instrumentation zCarson et al showed a seven fold decrease in bending moment with anterior column support

Lumbar Segmental Instability The Role of Interbody Fusion zInterbody fusion can be accomplished thru anterior or posterior approaches zNot a Stand-Alone (requires hardware) zEach has their own advantages and disadvantage zPosterior 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 zPosterior Interbody fusion disadvantages include: graft displacement, neurologic injury, and nonunion zAnterior 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 zAnterior 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 zIndications include the following: spondylolisthesis to stabilize the anterior column, pseudoarthrosis repair, recurrent disc herniations 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 zTypes of Interbody Allograft Spacers available include: femoral rings, cortical dowels, cortical ramps, and composite cortical and cancellous bone spacers zEach 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 zFemoral Ring Allograft Spacers 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 zDisadvantages 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 Cortical Dowels

Lumbar Segmental Instability The Role of Interbody Fusion zCortical 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 zDisadvantages 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 Cortical Ramps

Lumbar Segmental Instability The Role of Interbody Fusion zCortical 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 zDisadvantages 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 Metallic Devices

Lumbar Segmental Instability The Role of Interbody Fusion zAdvantages include being metallic and not dependent on bone availability zAvailable in a vast array of sizes and shapes for the specific needs zGreater structural support zInstantaneous stability while bone graft consolidates zBetter fixation to inner space

Lumbar Segmental Instability The Role of Interbody Fusion zDisadvantages include less bone ingrowth potental zLess surface area for bone ingrowth zNot an end plate sparing: dependent on device and insertion technique zPotential for subsidence zPotential for loss fit and migration zRe-establishment segmental lordosis

Lumbar Segmental Instability The Role of Interbody Fusion Biomaterial Devices Biomaterial Devices

Lumbar Segmental Instability The Role of Interbody Fusion zAdvantages: readily available zCan be fabricated in any size and shape zGood structural stability dependent on composite: ie. PEEK zEnd plate sparring: dependent on device and technique zRe-establish segmental lordosis zGood fixation to inner space

Lumbar Segmental Instability The Role of Interbody Fusion zDisadvantages: less surface area for bone ingrowth zPotential for ingrowth less than cortical ramps zPotential for migration zPotential for subsidence zPotential for reactive changes due to device: ie PEEK or bioabsorbables

Lumbar Segmental Instability The Role of Interbody Fusion zMaintain and/or re-establish segmental lordosis of individual disc spaces zRe-establish disc height zPromote foraminal decompression zEliminate rotation of the graft (fins) zSerrations for fixation and limitation of graft migration zProvide larger surface area for incorporation (serrations and fins)