Choosing an Interbody Cage Steven R. Garfin, MD Distinguished - - PowerPoint PPT Presentation

Choosing an Interbody Cage

Steven R. Garfin, MD Distinguished Professor and Chair Department of Orthopaedic Surgery UC San Diego

Disclosures

• AO Spine
• Benvenue Medical
• EBI
• Globus Medical
• Intrinsic Therapeutics
• Johnson & Johnson,

DePuy Spine

• Magnifi Group
• Medtronic
• NuVasive, Inc.
• SI Bone, Inc.
• Spinal Kinetics
• Vertiflex

How to choose an interbody graft?

• ALIF
• TLIF
• PLIF
• LLIF
• Expandable

What are the goals of surgery??

Interbody Fusion

• Helps stabilize anterior column / motion segment
• Enhances fusion rate
• Improvement in sagittal and coronal alignment
• Restoration/improvement in disc height
• Allows for indirect decompression of foraminal stenosis

by increasing disc/foraminal site

Interbody Indications

• Risk factors for non-union

– Smoking, obesity, diabetes, etc.

• Dynamic, (symptomatic), instability
• Failed posterior fusion
• Deformity Correction

Anterior Lumbar Interbody Fusion

• Fusion for discogenic back pain
• Particularly L5-S1 DDD, maybe L4-5
• Allows direct midline view for endplate prep disc

space

• Allows large implant size and surface area 

anatomical correction and fusion success

• Failed interbody fusion (LLIF, TLIF, TLIF)
• Complications include:

– Vascular and visceral injury – Retrograde ejaculation – Difficulty accessing disc space / mobilizing vessels (and have to abandon)

ALIF Cages

• Tricortical iliac crest graft
• Ring allografts
• PEEK
• PEEK + Vertebral body screws/”wings”
• Titanium

– Polished – Plasma spray – 3D modeling with large/small pores

Transforaminal Lumbar Interbody Fusion

• TLIF is pedicle based approach  requires facetectomy, partial lami, and

some dural retraction

• PLIF requires + neural retraction (not needed with TLIF)  nerve root

injury, dural tears and some epidural fibrosis

• TLIF can preserve midline structures (intra/supraspinous ligaments)
• Direct decompression
• Smaller footprint than with other cages
• May achieve less lordosis than LLIF/ALIF
• ? Safety at higher lumbar levels ?

Lateral Lumbar Interbody Fusion

(To me - the Work Horse)

• Indirect decompression
• Large footprint
• Endplate to endplate support (more than
• thers)
• Common complications

– Anterior thigh dysesthesias/weakness in 20- 30% – Inability to access disc space (nerve root)

LLIF Limitations

• Anatomy – psoas, iliac crest, lumbar plexus
• Large, central HNP can be difficult to address
• Learning curve
• L5-S1
• Sometimes L4-5 spondy

Incidence of thigh pain by year

• Reduction of Vertebral bodies

utilizing ligamentotaxis of ALL and PLL

• Central and Foraminal

Decompression

LLIF Advantages & Results: Indirect Decompression

• Radiographic assessment of LLIF ability to indirectly

decompress neural elements

• 42% average disc height increase
• 13.5% foraminal height increase
• 25% foraminal area increase
• 33% central canal area increase
• Indirect decompression limited if there is congenital

stenosis or cage subsidence

Graft Subsidence is a Concern

• 24 disc spaces (48 endplates)
• 6 disc spaces for each procedure – ALIF, PLIF, TLIF and XLIF
• ALIF -- least amount of relative endplate prep (35% of disc space)
• TLIF -- endplate damage highest (48% of specimens)
• XLIF -- greatest endplate preparation (60%of disc space) with least damage

Euro Spine 2015

• Placement of large cage across apophyseal rings

(cortical bone)

Lateral Access Cages Dimensions 18-22mm AP 45-60mm wide PLI F/ TLI F Dimensions 25-35mm AP 10-12mm wide ALI F Dimensions 21-24mm AP 32-36mm wide

≥30% endplate cage coverage = decreased subsidence

22% Subsidence7

TLIF / PLIF

2% Subsidence8

LLIF (22mm)

Lower Subsidence Rates with LLIF vs PLIF/TLIF

Spine 2017

• Randomized cadaveric study of 40 lumbar vertebras
• 4 groups
• (A)

Endplate decortication with short cage Short cage does not extend across apophyseal ring

• (B)

Endplate decortication with long cage Long cage spanning apophyseal ring

• Long cages spanning endplates

provides more strength in compression with less subsidence

• Spanning ring apophysis

increases load to failure by 40% with intact endplates and 30% with decorticated endplates

• Good endplate prep and longer

cages paramount in

• steoporotic patients to

decrease subsidence

How do the different grafts affect lordosis?

International Journal of Spine Surgery, 2016

• Retrospective, comparative radiographic

analysis of LLIF, ALIF and TLIF

• Compared standing pre- and 6wks post op

x-rays

• Looked at segmental lordosis at operative

level and regional lordosis (L1-S1) and anterior and posterior disc heights

• 121 pts  176 levels

– LLIF – 35pts, 54 levels – ALIF – 36 pts, 57 levels – TLIF – 50 pts, 65 levels

ALIF results in the greatest single level lordosis change – but not statistically significant compared to LLIF/TLIF

Coronal and Sagittal Plane alignment after LLIF

Significantly ↑↑ coronal alignment: segmental, regional, and globally ↑↑ regional lordosis/global sagittal alignment with OPEN techniques (not necessarily with Percutaneous or MIS techniques Significantly more segmental and regional lordosis of L- spine when osteotomies are performed

Acosta et al Lee, Kim, et al

Deformity Correction using LLIF

• Best Group:
• significantly less post-op SVA

(3.4 vs 6.9 cm, p = 0.043)

• significantly less post-op PI-LL mismatch than

the worst group. (10.4° vs 19.4°, p = 0.027)

International Spine Study Group JNSurg 2016

LLIF in Adult Degenerative Scoliosis

• 24 month f/u prospective study
• In hypolordosis pts: LL 28°  34° at 24 months (P < 0.001).
• Overall Cobb angle corrected 21°  15°,

Phillips, Isaacs, et al. Spine 2010

Akbarnia et al (IMAST, 2010)

• 2 yr f/u,
• Ave cobb: 47°  17°
• ↑↑in SRS-22, VAS & ODI
• Coronal L4 tilt: 23°  10°
• 45% coronal correction w lateral IB alone

70% w posterior instrumentation

Implant Materials

• PEEK

– Modulus close to bone – Radiolucent – Hydrophobic polymer – Does not allow for cell adhesion – Good x-rays/MRI

• Titanium

– Modulus higher than bone

• Stress shielding, altered load

– Surface allows for bone on- growth (particularly porous coated)

• Enhanced cell adhesion

– Some artifact on MRI

• 2 level ALIF performed in 9

sheep  performed initial biomechanical studies to establish initial stability of graft

• At 26wks – no difference in

the amount of fusion mass (sheep sacrificed)

Comparison of in vitro and in vivo biomechanics, fusion and bone apposition of PEEK and Ti at 26 weeks

Pelletier, Punjabi, et al. JSD 2013

Ti

Peek

• Ti/plasma coated = 42% of implant surface had bone contact
• PEEK = 12% of implant surface had bone contact

• J. Clin Neuro

No statistical difference in fusion rates btw PEEK vs titanium Titanium has higher incidence of graft subsidence

Expandable Cages

• Original designs

– Fill cage with graft material – After expansion what happens to graft

• Spreads up with expansion (leaving gap in middle)
• Stays put (leaving gap at ends)

– New designs

• Fill cage after expansion
• Fill around cage

My Preference for Technique

• ALIF

– L5-S1 – L4-5 only when also doing L5-S1 – Revision

• XLIF

– Thoracic to L4-5, if anatomy permits

• TLIF

– Lower lumbar (L3-4, L4-5 or L5-S1), if not able to get there via XLIF or ALIF

• Expandable Cages

– For MIS post-lat/lateral corpectomies

Conclusions

• End plate preparation is key!!

– Technology doesn’t make up for good surgical technique

• Which interbody technique best?

– Each has its own unique complications/advantages – Get some correction of sagittal alignment with each method

• What do you need to achieve?

– Alignment – Fusion – Both

• What device/approach?

Opportunity for studies

Thank Thank You You