Thoracic Pedicle Screw

Insertion Technique

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Jack Chen, MD Miami Children’s Hospital

Harry Shufflebarger, MDMiami Children’s Hospital

Michael O’Brien, MDMiami Children’s Hospital

Felix Quevedo, MDMiami Children’s Hospital

C O N S U L T I N G D O C T O R S

SETUP 3

DRILL ING 5

MEASURING LENGTH 10

SCREW PLACEMENT 11

C O N T e N T S

I N T R O D U C T I O N

Placement of Thoracic Pedicle Screws

Pedicle screws have proven to be an excellent bony anchor in the

posterior instrumentation of the spine. Correct placement within the

pedicle is important for a successful procedure, particularly in the

deformed thoracic spine.

The technique to be presented and illustrated was developed at Miami

Children’s Hospital. The technique is manual fluoroscopically assisted.

Over 10,000 thoracic screws have been successfully placed using the

technique.

Approximately 5 seconds of fluoro time is required per screw. Using an

average of 20 screws per case and performing approximately 100

deformity cases a year, over 85 years of surgical experience would be

required to exceed the recommended maximum accumulative radiation

dosage.

The authors are pleased to present this technique for the placement of

pedicle screws in deformity.

Harry Shufflebarger MD

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P E D I C L E S C R E W I N S E R T I O N T E C H N I Q U E

PeDICLe SCRew SeTUP

The first key step of the technique is to obtain a true AP image of the

vertebra that will be instrumented.

An AP of the patient does not result in a true AP image of the vertebra.

The true AP image of the vertebra is obtained after adjusting the C-arm

for kyphosis (lordosis) and rotation.

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Pedicle Screw Set-Up

The first key step of the technique is to obtain a true AP image of the vertebra that will be instrumented.

An AP of the patient does not result in a true AP image of the vetebra.

2

Pedicle Screw Set-Up

The first key step of the technique is to obtain a true AP image of the vertebra that will be instrumented.

An AP of the patient does not result in a true AP image of the vetebra.

3

The true AP image of the vertebra is obtained after adjusting the C-arm for kyphosis (lordosis) and rotation.

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The true AP image of the vertebra is obtained after adjusting the C-arm for kyphosis (lordosis) and rotation.

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The true AP image of the vertebra is obtained after adjusting the C-arm for kyphosis (lordosis) and rotation.

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P E D I C L E S C R E W I N S E R T I O N T E C H N I Q U E

PeDICLe SCRew DRILLING

The second key step is to know the length of the flutes of the drill bit

that will be used.

The length of the flutes on this drill bit measures 35 mm.

Clinical exampleThe image shows the correct starting point at the lateral aspect of the

pedicle. The starting point for the pedicle screw is marked with an awl.

Notice that approximately 20 mm of the drill bit has advanced. At this

length, if the image shows the tip of the drill to be at the medial wall of

the pedicle, it represents the fact that the drill bit is entering the vertebral

body.

The drill is then advanced into the pedicle. Fluoroscopic “spot-checks” are

done during the advancement of the drill. The correct path of the drill bit

is reflected by the combination of the length of the drill bit inserted and

the fluroscopic image of the tip of the drill bit at the medial wall of the

pedicle.

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Pedicle ScrewDrilling

Clinical Example

The image shows the correct starting point at the lateral aspect of the pedicle. The starting point for the pedicle screw is marked with an awl.

The second key step is to know the length of the flutes of the drill bit that will be used.

The length of the flutes on this drill bit measures 35mm.

5

The drill is then advanced into the pedicle. Fluoroscopic “spot-checks” are done during the advancement of the drill. The correct path of the drill bit is reflected by the combination of the length of the drill bit inserted and the fluroscopic image of the tip of the drill bit at the medial wall of the pedicle.

Notice that approximately 20 mm of the drill bit has advanced. At this length, if the image shows the tip of the drill to be at the medial wall of the pedicle, it represents the fact that the drill bit is entering the vertebral body.

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P E D I C L E S C R E W I N S E R T I O N T E C H N I Q U E

PeDICLe SCRew DRILLING (CONT.)

Clinical exampleThe drill bit tip at the starting point.

The drill has advanced approximately 20 mm. As the image shows, the

drill tip is at the medial wall of the pedicle, signifying that the drill is safely

past the length of the pedicle and entering the vertebral body.

However, if the image shows the drill bit to be at the medial pedicle wall,

but the drill has not advanced 20 mm, it reflects that the drill is

proceeding too medially.

The drill should be repositioned so that the image shows the tip is at the

medial pedicle after the drill has advanced at least 20 mm.

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Pedicle ScrewDrilling (continued)

The drill has advanced approximately 20mm. As the image shows, the drill tip is at the medial wall of the pedicle, signifying that the drill is safely past the length of the pedicle and entering the vertebral body.

Clinical Example

The drill bit tip at the starting point.

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Pedicle ScrewDrilling (continued)

The drill has advanced approximately 20mm. As the image shows, the drill tip is at the medial wall of the pedicle, signifying that the drill is safely past the length of the pedicle and entering the vertebral body.

Clinical Example

The drill bit tip at the starting point.

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However, if the image shows the drill bit to be at the medial pedicle wall, but the drill has not advanced 20mm, it reflects that the drill is proceeding too medially.

The drill should be repositioned so that the image shows the tip is at the medial pedicle after the drill has advanced at least 20 mm.

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P E D I C L E S C R E W I N S E R T I O N T E C H N I Q U E

PeDICLe SCRew MeaSURING LeNGTh

A ball tip probe is then inserted to the anterior cortex of the vertebral body.

A distinctive change will be felt as cancellous bone is passed and cortical

bone is encountered. This step measures the length of the screw and

allows for palpation of the drill track.

With the ball tip probe at the anterior cortex, the image will show the tip

of the probe to be at the center of the vertebra.

Ball tip probe at the anterior cortex.

The probe is grasped with a clamp, and the length of the screw is

determined.

PeDICLe SCRew DRILLING (CONT.)

As the drill bit is advanced into the body, the image shows the tip of the

bit past the medial pedicle wall, near the center of the vertebra.

The drill is inserted just past the end of the drill flutes. The drill has been

advanced into the vertebral body.

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Pedicle ScrewDrilling (continued)

As the drill bit is advanced into the body, the image shows the tip of the bit past the medial pedicle wall, near the center of the vertebra.

The drill is inserted just past the end of the drill flutes. The drill has been advanced into the verte-bral body.

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Pedicle ScrewMeasuring Length

A ball tip probe is then inserted to the anterior cortex of the vertebral body. A distinctive change will be felt as cancellous bone is passed and corti-cal bone is encountered. This step measures the length of the screw and allows for palpation of the drill track.

With the ball tip probe at the anterior cortex, the image will show the tip of the probe to be at the center of the vertebra.

Ball tip probe at the anterior cortex.

The probe is grasped with a clamp, and the length of the screw is determined.

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P E D I C L E S C R E W I N S E R T I O N T E C H N I Q U E

Clinical exampleAfter all the screws have been inserted, a lateral image is obtained.

PeDICLe SCRew PLaCeMeNT

The screw length for our model is 35 mm.

As the screw is inserted approximately 20mm, the image should show the

tip of the screw to be at the medial wall of the pedicle.

When the screw has been fully inserted, the image should show the tip of

the screw to be at the center of the vertebral body.

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Pedicle ScrewPlacement

The screw length for our model is 35mm.

As the screw is inserted approximately 20mm, the image should show the tip of the screw to be at the medial wall of the pedicle.

When the screw has been fully inserted, the image should show the tip of the screw to be at the center of the vertebral body.

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Clinical Example

After all the screws have been inserted, a lateral image is obtained.

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NOTeS

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inDiCaTiOnS: The EXPEDIUM® Spine System is intended to provide immobilisation and stabilisation of spinal segments in skeletally mature patients as an adjunct to fusion in the treatment of acute and chronic instabilities or deformities of the thoracic, lumbar and sacral spine. The EXPEDIUM® Spine System metallic components are intended for noncervical pedicle fixation and nonpedicle fixation for fusion for the following indications: degenerative disc disease (defined as back pain of discogenic origin with degeneration of the disc confirmed by history and radiographic studies); spondylolisthesis; trauma (i.e., fracture or dislocation); spinal stenosis; curvatures (i.e., scoliosis, kyphosis, and/or lordosis); tumour, pseudoarthrosis; and failed previous fusion in skeletally mature patients. The EXPEDIUM® PEEK rods are only indicated for fusion procedures for spinal stenosis with instability (no greater than Grade I spondylolisthesis) from L1-S1 in skeletally mature patients.

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