Medtronic G8532067 Technical Manual

CENTERPIECE™ 2.0
Plate Fixation System

DIRECTIONS FOR USE M333023W229 Rev. 2.0

MEDTRONIC

Use of the Wide Mouth Plate 18

Use of the Trough Plate 19

Overview 3

Patient Positioning 4

Surgical Exposure 4

Open Door Technique -Open-Side Trough Preparation 5

Open Door Technique -Hinge-Side Trough Preparation 5

Open Door Technique -Opening the Laminoplasty 6

Open Door Technique -Keeping the Door Open 6

A. Using the Open Door Plate 6

B. Using the Graft Plate 7

Use of the Lateral Hole Plate 8

Use of the Wide Mouth Plate 8

Use of the Trough Plate 8

Implant Removal 9

Important Information on the Centerpiece™ Plate Fixation System 10

Implant Removal 20

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OVERVIEW

Cervical laminoplasty can achieve spinal cord decompression commonly due to multisegmental spondylosis and/ or ossification of the
posterior longitudinal ligament (OPLL).
Various techniques have been employed to hold the door open while the host heals the laminar hinge in the expanded position. Ideally, a
method of achieving laminar fixation should be technically intuitive and provide secure maintenance of the lamina in the open position. The
authors describe the use of the novel Centerpiece™ Plate Fixation System designed to accomplish these goals during open door laminoplasty.
The technical issues relevant to performing the laminoplasty and securing the laminae are discussed. Laminoplasty procedures using these
plates will potentially allow the patient to engage in an early, active rehabilitation protocol, and may ultimately lead to better preservation of
motion.

1. Heller JG, Edwards CC II, Murakami H, Rodts GE. Laminoplasty versus laminectomy and fusion for multilevel cervical myelopathy: an
independent matched cohort analysis. Spine. June 15, 2001;26(12):1330-1336.

2. Yonenobu K, Heller JG, Oda T. Posterior Decompression for Myelopathy: Laminoplasty. In: Herkowitz HN, ed. The Cervical Spine
Surgery Atlas. 2nd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2003:203-218.Centerpiece™ Plate Fixation Sys

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The most common reason for failure of laminoplasty has been restenosis due to hinge closure.

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PATIENT POSITIONING

The patient is positioned prone as for most other posterior cervical procedures, with the head secured in a Mayfield three-pin head holder,
preferably in slight flexion. Some cervical flexion helps reduce the overlap of the laminae and facet joints, which facilitates the laminoplasty
itself. A reverse Trendelenburg position may help decrease bleeding from epidural and paravertebral veins.

SURGICAL EXPOSURE

The surgeon performs a midline posterior exposure from the inferior aspect of highest level to be decompressed to the superior aspect of the
lowest level. The lateral dissection follows the subperiosteal plane out to the midportion of the lateral masses. Unlike the exposure required
for a laminectomy and fusion, the muscle origins and insertions over the lateral half of the lateral masses are preserved. Should the levels to
be decompressed involve C3, the insertion of the extensor muscles is only detached from the lower laminar margin of C2 to afford access to
the C2–C3 interlaminar space. The junction of the medial aspect of the lateral mass with the lateral portion of the lamina is identified at each
level planned in the decompression. At this point, it is particularly helpful to correlate the local surface anatomy with the preoperative axial
images.

Helpful Hint

In the event that the posterior decompression should extend to the C2 level, this can be accomplished while respecting the integrity of the C2
posterior arch and the majority of its muscular origins and insertions. A “dome laminectomy” is performed by using a burr and Kerrison to
remove the lower margin of C2, followed by the cancellous bone and ventral cortex.

OPEN DOOR TECHNIQUE

OPEN-SIDE TROUGH PREPARATION

The open-side trough is prepared with a burr along the junction of the lamina and the lateral mass. The Midas Rex™ portfolio of high speed
burrs are available in various diameters and geometries, depending on surgeon preference and presentation of the anatomy. Three layers of
bone must be removed: the dorsal cortex, followed by the cancellous layer and then the ventral cortex. Hemostasis of the bone surfaces can
be achieved with the use of thin bone wax “match sticks” or applying a slurry of a hemostatic device and thrombin solution. The completion
of the bone separation on the open side can be performed with a 1.0mm Kerrison rongeur. At this point, the objective is to ensure that bone
separation has been achieved. Divide the ligamentum flavum as required. A 2.0mm or 3.0mm Kerrison punch may be used to excise the
ligamentum flavum at the inferior and superior most levels.

Helpful Hint

The side of the spinal canal to be opened may be chosen for a number of reasons. Planned foraminal decompression may be more readily
performed on the chosen open door side. If the patient shows radiographic evidence that there is central stenosis or OPLL lesion that is
asymmetric this may help determine which side to choose as the open vs. hinge side. In addition, perioperative CT can help determine the
thickness of "hinged side" bone in order to determine its suitability to undergo plastic deformation. Finally, all things being equal, the choice
may be influenced by the surgeon’s dominant hand. A right-hand-dominant surgeon will probably wish to stand on the patient’s left and
open the left side. The converse would be the case for a left-handed surgeon.

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OPEN DOOR TECHNIQUE

HINGE-SIDE TROUGH PREPARATION

On the hinge side of the laminoplasty another trough is made with the burr of choice. The cranial aspect of the hinge may be the thickest
part. Many surgeons use a "diamond-tipped burr" for formation of the hinge side in particular. This will permit one to assess the stiffness of
the hinge as it is prepared for each lamina. Care must be taken to avoid common errors: placing the trough too medially over the laminae
which may not give an adequate decompression and may not leave enough bone to hold the hinge open with the plate on the lamina side,
removing excessive bone, and/or placing the hinge too lateral which may violate the facet joint and destabilize the motion segment.

After removing the dorsal cortex and cancellous layer, assess the stiffness of the hinge at each level. The laminar hinge should yield slightly
with a moderate bending force. The surgeon should err on the side of leaving more bone, as fine-tuning can be done once every level is at,
or close to, the desired thickness. If the hinge fails to bend despite resection of what seems to be an adequate amount of bone, check to be
sure that the bone was completely divided on the open side.

Helpful Hint

In a situation where a hinge is either too floppy or displaced, the surgeon could opt to use the Trough Plate. This small, angled plate may be
used to secure the hinge when it is thought to be necessary.

OPEN DOOR TECHNIQUE

OPENING THE LAMINOPLASTY

Following the hinge side preparation, divide the ligamentum flavum as required. A 2.0mm or 3.0mm Kerrison punch may be used to excise
the ligamentum flavum at the inferior and superior most levels. Bipolar-electrocautery may assist with hemostasis of the epidural venous
plexus. The laminae are now sequentially opened from one end to another using an upgoing curette under the lamina or a Kocher on the
spinous process. Use an angled probe to ensure that any epidural adhesions have been lysed beneath the laminae before fully opening the
laminoplasty

OPEN DOOR TECHNIQUE

KEEPING THE DOOR OPEN

A. Trialing and Using the Open Door Plate

Plate Positioning

The appropriate size laminoplasty plate for each level is selected using the bone trials. There are two plate holder types: one has a straight tip
that is used with graft plates and the other has an angled tip that attaches to all other plates. Using the appropriate Plate Holder, insert the
selected plate by fitting the cut edge of the lamina into the laminar shelf of the plate. Then seat the lateral portion of the plate onto the edge
of the lateral mass. The ventral prong on the underside of the plate should catch the cut edge of the lateral mass. If necessary, a needle
driver can be used to contour the laminar and lateral mass aspects of the plate to fit the bony anatomy This helps to stabilize the plate’s
position while completing the fixation, as well as reducing any shear loads on the lateral screws.

Helpful Hint

Fully un-thread and depress the spring-loaded plate holder turn knob which will actuate the jaws to capture and provisionally secure the
plate. Ensure that the plate is fully captured by the jaws before releasing the knob. Turn the knob clockwise to lock the holder jaws to the
plate (Figure 11). To detach the plate holder from the plate, fully un-thread the knob by turning it counterclockwise to unlock the holder
jaws. Then fully depress the turn knob to release the plate. Ensure that the knob is fully depressed before detaching the holder to prevent
the prongs from catching on the plate.

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Drill and Screw Insertion

Each of the lateral mass screw pilot holes is made using the appropriate length drill bit based on desired screw length. The drill length should
match the screw length being implanted. Drills are color coded to match the screw color. Alternatively, a pilot divot could be drilled for the
desired points of screw fixation using an optional 1.0mm Midas Rex™ Burr. Preparing the surface of the lamina with a small divot could
prevent skiving during screw insertion.

Optional: The drill bit may be attached to the Universal Handle for manual drilling or attached to a power drill.

Important

Care should be taken if the drill and universal handle are used as skiving could occur resulting in the drill contacting undesired anatomy.

Once the desired screw length has been determined, the screw is attached to the Self-Holding Screwdriver Shaft and Universal Handle with
the help of the screw loading block or screw caddy for non-sterile screws. Ensure that the driver is fully seated on the screw head. Using the

self-holding screwdriver, the self-tapping screws are inserted to anchor the plate to the lateral mass. The plate holder can remain attached to
the plate to counter the screw insertion torque.

Confirmation of screw position can be made using radiographs or intraoperative fluoroscopy.

Note

The 2.0 diameter hole on the screw loading block can be used to check the screw diameter. Only the 2.0 diameter screw can be fully seated
into the diameter hole. The block also has a length verification tool.

Note

The 9mm drill will not have epoxy color-coding.

Important

Fully seat drill in plate and keep drill (or burr) coaxial with plate hole. Do not to apply excessive downward force when creating pilot hole or
divots. When using a lateral hole plate, do not place the plate such that when a screw is inserted it violates the facet joint.

Important

When detaching the driver, pull the driver off the screw while maintaining alignment with the trajectory of the screw placement. Note:
Detaching the driver from the screw off axis with respect to the screw can bind the driver/screw creating interference which can increase the
detachment force.

Important

It is important to match drill length with the screw length. Do not apply excessive torque when using the driver to insert the screw. Damage
to the screw or plate could occur due to excessive torque.

The laminar hole may then be drilled using the same technique as the lateral mass screw holes and then the plate can be secured with a self­tapping screw.

A second screw may be placed in the lamina if desired. In case of dense bone, the lamina may be stabilized with general surgical instruments
and/or the plate holders during screw insertion. This may protect the hinged lamina from screw insertion torque and prevent bone damage.

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Important

Only 3mm or 5mm screws should be used on the laminar shelf. 7mm and 9 mm drills should not be used through the lamina holes of the
plate. Do not insert 7mm and 9mm length screws into the hole above the lamina shelf of the plate as the screws will contact the plate shelf.
Care should be taken to avoid contact.

Note

Ø2.4 screw can be used as a rescue option if any of the initial pilot holes are stripped.

B. Using the Graft Plate

An alternative technique, which allows for the placement of autograft or allograft on the open side of the laminoplasty, can be performed
using the graft plate.

The initial surgical procedure is performed in the same manner as if preparing to use the open door plate as described on page 6. After the
laminoplasty has been “opened,” the appropriate size allograft is selected using the bone trials.

As an example, a 12mm trial corresponds to a 12mm allograft. The allograft is then attached to the graft plate and secured by inserting a
Ø2.4mm x 5mm screw through the predrilled center hole in the allograft. The oval-shaped center screw hole in the graft plate allows for fine
adjustments of the plate on the allograft. Use the graft plate holder to insert the allograft/graft plate construct between the cut edge of the
lamina and the lateral mass. To secure the allograft/graft plate construct to the bone and complete the fixation, drill and insert the self­tapping screws according to the procedural steps described on page 6.

The allograft/graft plate can be used at every level of the laminoplasty or may be used at desired levels in combination with open door plates
per surgeon preference.

USE OF THE

LATERAL HOLE PLATE

In the event the surface area of the lateral mass is either too small in its cranial-caudal dimension, or it has been reduced in the addition of
one or more foraminotomies, one could opt to use the lateral hole plate. The sizing and method of insertion are the same as for the standard
open door and graft plates, except that the orientation of the lateral mass screws is parallel to the long axis of the plate and the graft
plateholder is used exclusively with graft plates. The exposure may need to be widened slightly at any level where the lateral hole plates are
used.

USE OF THE

WIDE MOUTH PLATE

The wide mouth plate may be needed on occasion to accommodate thicker laminae. As an alternative to bending the laminar shelf of the
standard open door plate, one could use the wide mouth plate to allow for easier placement onto the thicker lamina. The sizing and method
of insertion are the same as for the standard open door plate.

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USE OF THE

TROUGH PLATE

The trough plate may be needed on occasion to secure a floppy or displaced hinge which threatens to impinge upon a nerve root or the dura.
In the event it is judged to be necessary, its application begins before opening the laminoplasty. The loose lamina should be grasped and
stabilized with a suitable clamp (e.g., a ligamentum flavum clamp). It is held firmly while the laminar side screw holes are drilled with the
Ø1.2mm x 4.5mm drill bit with depth-stop or Midas™ twist drills. The trough plate is then fastened to the lamina with two 3mm or 5mm
screws. The laminoplasty is then opened as usual. The lateral mass screw holes for the trough plate are then drilled for two additional screws
and two screws are inserted, firmly fixing the hinge in place. The repair is inspected to confirm that the lamina remains elevated away from
the canal and foramen. If there is concern for impingement, the segment may be converted to a laminectomy with laminoplasty continued
at other levels.

IMPLANT

REMOVAL

To remove any of the laminoplasty plates described throughout this technique, engage the screw head with the self-holding screwdriver, and
in a counterclockwise motion, remove the screw from the bone. The plate can then be freely removed from the bone.

Note

Ensure that the screw threads are completely backed out of the bone prior to pulling the screw out to prevent the driver from
unintentionally disengaging from the screw upon removal.

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Important product information on the Centerpiece™
Plate Fixation System

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M333023W229

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