Observe / Operate Congenital Deformity Pedicle Screw Insertion And Salvage Techniques

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10/12 DA10293A, CA9232A

Challenging Pedicle Screw

Insertion/Salvage

Techniques

Suken A. Shah, MD

Alfred I. duPont Hospital for Children

Division Chief, Spine and Scoliosis

Center

Wilmington, Delaware USA

Spinal Deformity Surgery Educational Continuum

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Pedicle Screws in Deformity

Biomechanical screw performance:

Hackenberg L, Spine 2002

O’Brien MF, Spine 2000

Hamill CL, et al, Spine 1996

Three column control of vertebra

Improved coronal, sagittal & rotational correction

Minimal loss of correction over time

Lower pseudarthrosis rates

Lower implant failures

Earlier return to activities

Avoid anterior release, thoracoplasty

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Thoracic Pedicle Screws for AIS

Suk S-I, et al, Spine 1995; 20: 1399-1405

TPS for correction of adolescent idiopathic scoliosis

Coronal correction Rotational correction

Hooks 49% 19%

Screws in a hook pattern 64% 26%

Segmental screws 72% 59%

Less loss of correction at 2 yrs with TPS

No implant failures with TPS

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Thoracic Pedicle Screws in Deformity:

Concerns

Greater risk of misplaced screws

Spinal cord, great vessels, viscera

Truly intraosseous?

Pedicle anatomy and morphology in scoliosis

Thin pedicles

Difficulty of placement

Cost

Outcomes? Vaccaro A, J Bone Joint Surg Am 1995

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Structures at Risk

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Screw Insertion Techniques

Freehand Placement

Pedicle gearshift / Probe

Drill

Fluoroscopic Assisted

Funnel Technique

Intraoperative Navigation

Electronic Conductivity Device

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Freehand Screw Placement

Safety Data:

Kim Y, Lenke L, Bridwell K, et al Spine 2004

Stepwise, consistent and compulsive

Accurate, reliable and safe

Schizas C, Eur Spine J 2007

Safety in upper T spine (T1-T3)

Equivalent to fluoro/navigation techniques

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TPS Accuracy in Deformity

Belmont, Spine 2001 and Kim, Spine 2004

Accuracy in nonscoliotic spines ~ 78-99%

Accuracy in deformity ~ 69-97.8%

Kuklo, Lenke, O’Brien et al, Spine 2005

TPS Accuracy and Efficacy in Curves > 90°

94% of the planned screws were inserted

Accuracy ~ 96.3%, Efficacy ~ 68% correction

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Dry Exposure - Visualization

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Insertion Technique: Starting Point

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Insertion Technique: Starting Point

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Assess Rotation & Adjust Trajectory

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Pedicle Morphology

in the Spine with

Scoliosis

Parent S, et al, Spine 2004; 29: 239-248

Concave pedicles are smaller

Left (concave) Pedicle Width

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Freehand Screw Placement

Outward

gearshift

until the

pedicle base

Inward

gearshift into

vertebral body

after the

pedicle base

Kim YJ, Lenke LG et al, Spine 20047

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Freehand Screw Placement

Kim YJ, Lenke LG et al, Spine 2004

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Difficult Screw Placement

Concavity of curves

Main thoracic

Proximal thoracic

Senaran, Shah et al.

J Spinal Disord 2007

T3,T4 concavity

18% sclerotic, narrow

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Type A Type B Type C Type D

Pedicle Morphology Classification

Type A - “Large Cancellous Channel” (50%)

Type B - “Small Cancellous Channel” (40%)

Type C - “Cortical Channel” (7%)

Type D - “Absent Pedicle Channel” (3%)

Watanabe, Lenke et al IMAST 2007 and under review

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Type A - Pedicle probe is smoothly inserted without difficulty

Type B - Pedicle probe is inserted snugly with increased force

Type C - Pedicle probe cannot be manually inserted but must be

tapped with a mallet down into the body

Type D - Necessitates a “juxtapedicular” pedicle probe insertion

Type A Type B Type C Type D

Insertion Techniques

Watanabe, Lenke et al IMAST 2007 and under review

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13 yo♀ AIS Lenke 3CN

85

75

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13 yo♀ AIS Lenke 3CN

PSF T4-L4

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Severe Kyphoscoliosis

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Difficult Screws

Severe curves

Difficult exposure: bleeding, ribs

Small, narrow, sclerotic pedicles

Osteoporotic bone

Osteotomy stabilization

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Fluoroscopic Assisted Screw Insertion

Shufflebarger, DePuy Spine Technique Guide, 2007

Carbone J, Spine 2003

Rampersaud YR, Spine 2000

Collinear

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Endplates

parallel

Pedicles in

upper half of

vertebral

body

Spinous process equidistant

Proper AP image for Fluoro

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Fluoroscopic Assisted Screw Insertion

Multiplanar fluoro, Iso-C, O-arm

Accuracy 78-93%

Radiation exposure

Wang M et al, Neurosurgery 2004

Kuntz C, J Spinal Disord 2004

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Intraoperative Navigation

Kotani Y et al, Spine 2007: improved accuracy over fluoro

Mirza S et al, Spine 2003: multiple reference markers

Kosmopoulus V et al, Spine 2007: improved accuracy over

other techniques, except in thoracic spine 26

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Intraoperative Navigation

The Challenges

Learning curve (frustration)

Registration of the patient’s anatomy in the OR

Non sterile expert

Still need fluoro or intraop CT

Tools are cumbersome 27

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Electronic Conductivity Device

Breach anticipation

(alert to surgeon)

Immediate redirection

if necessary

Juxtapedicular

technique

Possible bicortical

fixation

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Electronic Conductivity Device

Bolger et al. Eur Spine J, in press

Correctly identified intentional breaches

Betz, Samdani et al. Temple J Orthop Surg 2008

Decreased rate of medial breaches by 8%

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Salvage Techniques / Alternatives

Tendency is to miss lateral and/or inferior

Change Trajectory [anatomic / rotational traj.]

Fluoroscopic Assistance

Drill / smaller or sharper probe

Laminotomy / Funnel Technique

Extra- or Juxtapedicular (lateral) Placement

Intralaminar Screws

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Insertion Technique: Trajectory

Straight Ahead Trajectory

Parallels superior end plate

Allows monoaxial screw

Higher IT and pullout (27%)

Anatomic Trajectory

Along pedicle axis

Requires multi-axial screw

Salvage situation 62%

Lehman RA, Spine 2003

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Salvage Techniques for Screw Placement

Palpate the medial and inferior borders of the pedicle from the

canal and start 2 mm lateral 32

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Salvage Techniques for Screw Placement

Zeiller et al, Neurol India 2005

Palpate the lateral border of the superior articular process /

TP junction

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Cannulated tap developed for screw

insertion in small pedicles

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Extra/Juxtapedicular Techniques

Pullout inferior than transpedicular

But, acceptable (65-80%)

Decent salvage alternative

Maybe the only alternative (Type D pedicle)

White KK, Spine 2006

Yuksel KZ, Spine 2007

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Extra/Juxtapedicular Techniques

Pullout inferior than transpedicular

But, acceptable (65-80%) [rib head]

Decent salvage alternative

Maybe the only alternative (Type D pedicle)

White KK, Spine 2006

Yuksel KZ, Spine 2007

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Funnel Technique

Yingsakmonkol, Karaikovic, and Gaines, J Spinal Disord 2002

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Intralaminar Screw Placement

A curved pedicle probe is directed along the axis

of the lamina with the curved tip aimed dorsally.

(1) The trajectory is kept slightly less than the

down slope of the lamina.

(2) The screw is placed entirely within the

cortical bone.

(3) A- Axis of the lamina, B - ideal trajectory.

Lewis SJ et al, Spine 2009

Biomechanics sound - Cardoso MJ J Neurosurg Spine 2009

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Screw Revision Techniques

Change trajectory

Pedicle dilation

Clements D, pilot data – increased pullout 200Nm

Larger diameter screws better than longer

Polly DW et al, Spine 1998

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Other Alternatives

Hooks (pedicle, laminar, TP)

Cordista A, Spine 2006 “Biomechx of

screws/hooks”

Hook claw config was 88% stronger than TPS

Coe J, Spine 1990 “Infl of BMD on fix. strength”

Laminar hooks found to be the strongest

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Other Alternatives

Sublaminar wires

Cheng I et al Spine 2005 “Wires vs. TPS”

Similar corrections, OR time, fusion length, SRS scores

Wires cheaper

Transverse process wires

Fujita, Spine 2006

Erel, Acta Orthop Scand 2003

New materials

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Other Alternatives

Sublaminar wires

Cheng I et al Spine 2005 “Wires vs. TPS”

Similar corrections, OR time, fusion length, SRS scores

Wires cheaper

Transverse process wires

Fujita, Spine 2006

Erel, Acta Orthop Scand 2003

New materials

Leave it out

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14 yo ♂ AIS

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14 yo ♂ AIS

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14 yo ♂ AIS

• Ant. Tscopic release

•Ponte osteotomies

•Rib head release

•Combination of

techniques for screw

insertion

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Summary

Many screw salvage techniques

Severe deformities

Small, narrow, sclerotic pedicles

Osteoporotic bone

Revision cases / fusion mass

Extra- or juxtapedicular position is acceptable

Fluoroscopy is helpful

Segmental screw fixation is not necessary

Other alternatives are available (hooks, wires)

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Thank you

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