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Clinical Evidence eGuide

O-arm® Imaging System

Innovating for life.

Version 1.0 (January 2012)

Medtronic Navigation

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Louisville, CO 80027 USA

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Clinical Evidence eGuide O-arm® Imaging System

Purpose

Clariﬁcations

Table of Contents

Purpose

This guide is to be used as an education tool. The purpose is to provide health care

providers with a reference tool of peer-reviewed articles that discuss the use the

O-arm® imaging system in surgery.

Medtronic Navigation conducted a literature search of published articles across

many scientiﬁc journals. All articles found that reference the O-arm ® imaging system

were selected to be included in this guide.

HOME

Clarications

Medtronic Navigation wishes to clarify the following points:

(1) The O-arm® Intraoperative Imaging System is a Class II Medical Device in the US

and has been cleared for marketing under a 510(k) submission by the FDA. This

type of clearance means that FDA has concurred with the manufacturer’s asser-

tion that the device is substantially equivalent to other devices legally marketed

in the US.

(2) The O-arm® Intraoperative Imaging System is cleared as a Mobile X-ray System

under 21 CFR 892.1720 and as a Solid State X-ray Imager under 21 CFR 892.1650.

Medtronic Navigation makes no claim that the O-arm® system complies with the

necessary performance standards to be called a Computed Tomography X-Ray

System under 21 CFR 892.1750.

(3) The cleared Indications for Use statement for the O-arm® Imaging System is: The

O-arm® Imaging System is a mobile x-ray system designed for 2D ﬂuoroscopic

and 3D imaging and is intended to be used where a physician beneﬁts from 2D

and 3D information of anatomic structures and objects with high x-ray attenua-

tion such as bony anatomy and metallic objects. The O-arm® imaging System is

compatible with certain Image Guided Surgery Systems.

HOME

Table of Contents

SPINE AND ORTHOPEDICS

CRANIAL AND ENT

ONCOLOGY

IMAGING TECHNOLOGY

HOME

Table of contents - Spine and Orthopedics

Lead Author Year Abbreviated Title Journal

Schils 2011 O-Arm–Guided Balloon Kyphoplasty: Prospective Single-Center Case Series of 54

Consecutive Patients Neurosurgery

Oertel 2011 Clinical and methodological precision of spinal navigation assisted by 3

intraoperative O-arm radiographic imaging Neurosurgery Spine

Silbermann 2011

Computer tomography assessment of pedicle screw placement in lumbar

and sacral spine: comparison between free-hand and O-arm based navigation

techniques

Eur Spine J

Wood 2011 A comparison of CT-based navigation techniques for minimally invasive lumbar

pedicle screw placement.

Spinal Disorders

& Techniques

Ishikawa 2011 Intraoperative, full-rotation, three-dimensional image (O-arm)–based navigation

system for cervical pedicle screw insertion- Clinical Article

Journal of Neurosurgery:

Spine

Sclafani 2011

Use of a quantitative pedicle screw accuracy system to assess new technology:

Initial studies on O-arm navigation and its eﬀect on the learning curve of

percutaneous pedicle screw insertion.

SAS Journal

Garrido 2011 Navigated placement of iliac bolts: description of a new technique. Spine J

Moﬁdi 2011 Use of Intraoperative Computed Tomography Scanning in Determining the

Magnitude of Arthroscopic Osteochondroplasty Arthroscopy

Gonschorek S 2011 O-arm based spinal navigation and intraoperative 3D-imaging: ﬁrst experiences European Journal of Trauma

and Emergency Surgery

Ailawadhi 2011 Use of O-arm for spinal surgery in academic institution in India: Experience from

JPN apex trauma centre Neurology India

Please tap any title to view article

TABLE OF CONTENTS

MAIN

Table of contents - Spine and Orthopedics

Lead Author Year Abbreviated Title Journal

Costa 2011 Evaluation of the rate of decompression in anterior cervical corpectomy using an

intra-operative computerized tomography scan (O-arm system) European Spine Journal

Santos 2011 The Accuracy of Intraoperative O-arm Images for the Assessment of Pedicle

Screw Postion. Spine J

Schils F. 2011 O-arm guided balloon kyphoplasty: preliminary experience of 16 consecutive

patients. Acta Neurochirugica

Santos 2011 Validity of surgeon perception of navigated pedicle screw position: a cadaveric

study Spine J

Kim 2011 Modiﬁed transcorporeal anterior cervical microforaminotomy assisted by O-arm-

based navigation: a technical case report. European Spine Journal

Nottmeier EW 2010 Image-guided placement of occipitocervical instrumentation using a reference

arc attached to the headholder. Neurosurgery

Nottmeier EW 2010 Three-dimensional image-guided placement of S2 alar screws to adjunct or

salvage lumbosacral ﬁxation. Spine J

Kim 2010 Pedicle screw ﬁxation under navigation guidance based on O-arm

The Internet Journal of Minimally

Invasive Spinal Technology

Wood 2010 Improving accuracy and reducing radiation exposure in minimally invasive

lumbar interbody fusion. Neurosurgery Spine

Park 2010 Minimally invasive pedicle screw ﬁxation utilizing O-arm ﬂuoroscopy with

computer-assisted navigation: Feasability, technique, and preliminary results. Surg Neurol Int.

Please tap any title to view article

TABLE OF CONTENTS

MAIN

Table of contents - Spine and Orthopedics

Lead Author Year Abbreviated Title Journal

Kim 2010 An assistive image-guided surgical robot system using O-arm ﬂuoroscopy for

pedicle screw insertion: preliminary and cadaveric study. Neurosurgery

Brennen 2008 Minimally invasive image-guided direct repair of bilateral L-5 pars

interarticularis defects. Neurosurgery Focus

Metz, LN 2008 Computer-Assisted Surgical Planning and Image-Guided Surgical Navigation in

Refractory Adult Scoliosis Surgery: Case Report and Review of the Literature Spine J

Please tap any title to view article

TABLE OF CONTENTS

MAIN

Table of contents - Cranial and ENT

Lead Author Year Abbreviated Title Journal

Shahlaie K 2011 Intraoperative computed tomography for deep brain stimulation surgery:

technique and accuracy assessment Neurosurgery

Smith 2011 Frameless deep brain stimulation using intraoperative O-arm technology Neurosurgery

Conley 2011 Comparison of Intraoperative Portable CT Scanners in Skull Base and Endoscopic

Sinus Surgery: Single Center Case Series Skull Base

Leung 2011 Advancements in computed tomography management of chronic rhinosinusitis American Journal of

Rhinology & Allergy

Caire F 2010 Intraoperative use of the Medtronic O-arm for deep brain stimulation procedures.

Stereotact Funct

Neurosurgy

Bloom 2009 Real-Time Intraoperative Computed Tomography to Assist Cochlear Implant

Placement in the Malformed Inner Ear: Otology & Neurotology Otology & Neurotology

Please tap any title to view article

TABLE OF CONTENTS

MAIN

Table of contents - Oncology

Lead Author Year Abbreviated Title Journal

Wu 2011 Intraoperative Navigation for Minimally Invasive Resection of Periarticular and

Pelvic Tumors. Orthopedics

Zelefsky 2010 Real-time intraoperative computed tomography assessment of quality of

permanent interstitial seed implantation for prostate cancer. Urology

Please tap any title to view article

TABLE OF CONTENTS

MAIN

Table of contents - Imaging Technology

Lead Author Year Abbreviated Title Journal

Abul Kasim 2011 Optimization of Radiation Exposure and Image Quality of the Cone-beam O-arm

Intraoperative Imaging System in Spinal Surgery.

Journal of Spinal

Disorders and Techniques

Park 2011 The perspectives of users and developers in designing and developing O-arm

imaging system

Journal of X-ray Science

and Technology

Park 2011 Comparison of operator radiation exposure between C-arm and O-arm

ﬂuoroscopy for orthopaedic surgery

Radiation Protection

Dosimetry

Zhang 2009 Dosimetric characterization of a cone-beam O-arm imaging system. Journal of X-ray Science

and Technology

Please tap any title to view article

TABLE OF CONTENTS

MAIN

O-arm–Guided Balloon Kyphoplasty: Prospective Single-Center Case

Series of 54 Consecutive Patients

Schils, Frédéric MD

Department of Neurosurgery, Clinique Saint Joseph, Liège, Belgium

Neurosurgery June 2011

Background:

Balloon kyphoplasty is widely used to treat vertebral compression

fractures. Procedure outcome and safety are directly linked to

precise radiological imaging requiring 1 or 2 C arms to allow

correct visualization throughout the procedure. This minimally

invasive spinal surgery is associated with radiation exposure for

both patient and surgeon. In our center, we switched from using

a C-arm to an O-arm image guidance system to perform balloon

kyphoplasty. Our preliminary experience is reported in Acta

Neurochirurgica, and the encouraging results led us to study this

subject more extensively. This article presents our complete results.

To the best of our knowledge, there is no comparable clinical series

describing O-arm use in kyphoplasty procedures published in the

literature.

Objective:

To report our complete results of using the O-arm guidance system

to perform balloon kyphoplasty.

Methods:

We prospectively evaluated O-arm-guided kyphoplasty procedure in

54 consecutive patients and measured x-ray exposure and ﬂuoros-

copy time.

Results:

The mean surgical time for the procedure was 38 minutes with

a mean ﬂuoroscopy procedure time of 3.1 minutes. The mean

ﬂuoroscopy time by level was 2.5 minutes. Mean irradiation dose

by procedure was 220 mGy and by level was 166 mGy. There was a

signiﬁcant reduction in ﬂuoroscopy time and x-ray exposure from

5.1 minutes with classic C-arm use to 3.1 minutes when with O-arm

use without additional time required for positioning the system.

Conclusion:

With this new intraoperative system, the overall surgical and

ﬂuoroscopy times can be further reduced in the near future.

Abstract

TABLE OF CONTENTS

SPINE & ORTHO

FORWARD

Clinical and methodological precision of spinal navigation assisted

by 3D intraoperative O-arm radiographic imaging

Matthias F. Oertel, M.D, et al

Department of Neurosurgery, University Hospital Giessen and Marburg GmbH,

Giessen, Germany

Spine J. 2011 April

Objective:

In recent years, the importance of intraoperative navigation in

neurosurgery has been increasing. Multiple studies have proven

the advantages and safety of computer-assisted spinal neurosur-

gery. The use of intraoperative 3D radiographic imaging to acquire

image information for navigational purposes has several advantag-

es and should increase the accuracy and safety of screw guidance

with navigation. The aim of this study was to evaluate the clinical

and methodological precision of navigated spine surgery in

combination with the O-arm multidimensional imaging system.

Methods:

Thoracic, lumbar, and sacral pedicle screws that were placed

with the help of the combination of the O-arm and StealthStation

TREON plus navigation systems were analyzed. To evaluate clinical

precision, 278 polyaxial pedicle screws in 139 vertebrae were

reviewed for medial or caudal perforations on coronal projection.

For the evaluation of the methodological accuracy, virtual and intra-

operative images were compared, and the angulation of the pedicle

screw to the midsagittal line was measured.

Results:

Pedicle perforations were recorded in 3.2% of pedicle screws. None

of the perforated pedicle screws damaged a nerve root. The diﬀer-

ence in angulation between the actual and virtual pedicle screws

was 2.8° ± 1.9°.

Conclusion:

The use of the StealthStation TREON plus navigation system in

combination with the O-arm system showed the highest accuracy

for spinal navigation compared with other studies that used

traditional image acquisition and registration for navigation.

Abstract

TABLE OF CONTENTS

SPINE & ORTHO

FORWARD

BACK

Computer tomography assessment of pedicle screw placement in

lumbar and sacral spine: comparison between free-hand and O-arm®

based navigation techniques

J. Silbermann, F. Riese, Y. Allam, T. Reichert, H. Koeppert and M. Gutberlet

Department of Spine Surgery, Park-Krankenhaus, Leipzig, Germany

Eur Spine J (2011)

Transpedicular screw ﬁxation has been accepted worldwide since

Harrington et al. ﬁrst placed pedicle screws through the isthmus. In

vivo and in vitro studies indicated that pedicle screw insertion

accuracy could be signiﬁcantly improved with image-assisted

systems compared with conventional approaches. The O-arm is a

new generation intraoperative imaging system designed without

compromise to address the needs of a modern OR like no other

system currently available. The aim of our study was to check the

accuracy of O-arm based and S7-navigated pedicle screw implants

in comparison to free-hand technique described by Roy-Camille at

the lumbar and sacral spine using CT scans.

The material of this study was divided into two groups, free-hand

group (group I) (30 patients; 152 screws) and O-arm group (37

patients; 187 screws). The patients were operated upon from

January to September 2009. Screw implantation was performed

during PLIF or TLIF mainly for spondylolisthesis, osteochondritis

and post-laminectomy syndrome.

The accuracy rate in our work was 94.1% in the free-hand group

compared to 99% in the O-arm navigated group. Thus it was

concluded that free-hand technique will only be safe and accurate

when it is in the hands of an experienced surgeon and the accuracy

of screw placement with O-arm can reach 100%.

Abstract

TABLE OF CONTENTS

SPINE & ORTHO

FORWARD

BACK

A Comparison of CT-based Navigation Techniques for Minimally

Invasive Lumbar Pedicle Screw Placement

Wood, Martin FRACS, MBChB* Mannion, Richard PhD, FRCS

The Mater Private Hospital Brisbane, Queensland, Australia.

Journal of Spinal Disorders

& Techniques, February 2011

Study Design:

A comparison of 2 surgical techniques.

Objective:

To determine the relative accuracy of minimally invasive lumbar

pedicle screw placement using 2 diﬀerent CT-based image-guided

techniques.

Summary of Background:

Three-dimensional intraoperative ﬂuoroscopy systems have

recently become available that provide the ability to use CT-quality

images for navigation during image-guided minimally invasive

spinal surgery. However, the cost of this equipment may negate

any potential beneﬁt in navigational accuracy. We therefore assess

the accuracy of pedicle screw placement using an intraoperative

3-dimensional ﬂuoroscope for guidance compared with a technique

using preoperative CT images merged to intraoperative 2-dimen-

sional ﬂuoroscopy.

Methods:

Sixty-seven patients undergoing minimally invasive placement

of lumbar pedicle screws (296 screws) using a navigated, image-

guided technique were studied and the accuracy of pedicle screw

placement assessed. Electromyography (EMG) monitoring of lumbar

nerve roots was used in all.

Group 1: 24 patients in whom a preoperative CT scan was merged

with intraoperative 2-dimensional ﬂuoroscopy images on the

image-guidance system. Group 2: 43 patients using intraoperative

3-dimensional ﬂuoroscopy images as the source for the image guid-

ance system. The frequencies of pedicle breach and EMG warnings

(indicating potentially unsafe screw placement) in each group were

recorded.

Results:

The rate of pedicle screw misplacement was 6.4% in group 1vs 1.6%

in group 2 (P=0.03). There were no cases of neurologic injury from

suboptimal placement of screws. Additionally, the incidence of EMG

warnings was signiﬁcantly lower in group 2 (3.7% vs. 10% (P=0.03).

Conclusion:

The use of an intraoperative 3-dimensional ﬂuoroscopy system with

an image-guidance system results in greater accuracy of pedicle

screw placement than the use of preoperative CT scans, although

potentially dangerous placement of pedicle screws can be prevent-

ed by the use of EMG monitoring of lumbar nerve roots.

Abstract

TABLE OF CONTENTS

SPINE & ORTHO

FORWARD

BACK

Object:

The aim of this study was to retrospectively evaluate the reliability

and accuracy of cervical pedicle screw (CPS) placement using an

intraoperative, full-rotation, 3D image (O-arm)–based navigation

system and to assess the advantages and disadvantages of the

system.

Methods:

The study involved 21 consecutive patients undergoing posterior

stabilization surgery of the cervical spine between April and Decem-

ber 2009. The patients, in whom 108 CPSs had been inserted, un-

derwent screw placement based on intraoperative 3D imaging and

navigation using the O-arm system. Cervical pedicle screw positions

were classiﬁed into 4 grades, according to pedicle-wall perforations,

by using postoperative CT.

Results:

Of the 108 CPSs, 96 (88.9%) were classiﬁed as Grade 0 (no perfora-

tion), 9 (8.3%) as Grade 1 (perforations < 2 mm, CPS exposed, and <

50% of screw diameter outside the pedicle), and 3 (2.8%) as Grade

2 (perforations between ≥ 2 and < 4 mm, CPS breached the pedicle

wall, and > 50% of screw diameter outside the pedicle).

No screw was classiﬁed as Grade 3 (perforation > 4 mm, complete

perforation). No neurovascular complications occurred because of

CPS placement.

Conclusion:

The O-arm oﬀers high-resolution 2D or 3D images, facilitates accu-

rate and safe CPS insertion with high-quality navigation, and pro-

vides other substantial beneﬁts for cervical spinal instrumentation.

Even with current optimized technology, however, CPS perforation

cannot be completely prevented, with 8.3% instances of minor

violations, which do not cause signiﬁcant complications, and 2.8%

instances of major pedicle violations, which may cause catastrophic

complications. Therefore, a combination of intraoperative 3D im-

age–based navigation with other techniques may result in more

accurate CPS placement.

Abstract

Intraoperative, full-rotation, three-dimensional image (O-arm)–based

navigation system for cervical pedicle screw insertion- Clinical Article

Yoshimoto Ishikawa et al. Department of Orthopedic Surgery, Spine Center, Konan

Kosei Hospital, Takaya Chou, Konan City, Japan

Journal of Neurosurgery: Spine , Nov 2011

TABLE OF CONTENTS

SPINE & ORTHO

FORWARD

BACK

Use of a quantitative pedicle screw accuracy system to assess new

technology: Initial studies on O-arm navigation and its eect on the

learning curve of percutaneous pedicle screw insertion.

Joseph A. Sclafani, MD et al. Department of Orthopaedic Surgery, University of

California, San Diego, Center for Minimally Invasive Surgery at Alvarado Hospital CA,

San Diego.

SAS Journal, September 2011

Background:

A quantitative screw accuracy system is proposed that allows for

high-ﬁdelity discrimination between various methods of pedicle

screw insertion. Our purpose was to study the utility of a quantita-

tive screw accuracy scoring system to assess new imaging technolo-

gies and their eﬀects on the minimally invasive spine learning curve.

Methods:

By use of a hypothetical “perfect screw,” a scoring system is proposed

that may be used to compare the position of a small number of

screws inserted according to a desired optimal position. This study

incorporates a retrospective review of imaging studies for 10 pa-

tients who underwent percutaneous pedicle screw placement with

either navigation-assisted O-arm imaging or navigation-assisted

C-arm imaging. For the learning-curve portion of the study, 2 cadav-

eric adult torsos were used for instrumentation. Computed tomog-

raphy imaging studies were used in both studies to assess screw

position in the pedicle and vertebral body in relation to an optimal

screw by use of a quantitative scoring system to rate accuracy.

Results:

The quantitative scoring system allowed a statistically signiﬁcant

accuracy diﬀerence to be ascertained between 2 diﬀerent technolo-

gies using fewer data points than previously published methods.

When this screw scoring system is applied to minimally invasive

percutaneous pedicle screw insertion, an optimal screw position

can be achieved with greater accuracy through navigation-assisted

technology (O-arm with computer-assisted navigation). When the

O-arm with computer-assisted navigation was used by a novice

surgeon learning the technique of percutaneous screw insertion,

screws were inserted in a shorter period without loss of accuracy. In

contrast, use of the traditional C-arm ﬂuoroscopy leads to a loss of

accuracy with faster insertion times. Increased accuracy can be seen

clinically when compared with ﬂuoroscopic navigation.

Conclusion:

The use of a quantitative scoring system allows for rapid assessment

of screw accuracy. As additional technologies and new teaching

techniques for pedicle screw insertion are developed, this

scoring system may be useful as an early assessment tool.

Abstract

TABLE OF CONTENTS

SPINE & ORTHO

FORWARD

BACK

Navigated placement of iliac bolts: description of a new technique.

Garrido BJ, Wood KE. Lake Norman Orthopedic Spine Center, 170 Medical Park Rd,

Suite 102, Mooresville, NC 28117

Spine J. 2011 April

Background Context:

Image navigation has improved the safety and ability to perform

complex spinal procedures where visibility is not optimal or

anatomic deformity is present. Numerous published studies are

available demonstrating its eﬀectiveness in improved pedicle screw

placement in complex multiplanar deformities. Studies have also

demonstrated image navigation technology versatility; however,

stabilization of the lumbopelvic junction with navigated iliac bolt

ﬁxation has not been reported.

Purpose:

To describe an innovative versatile application of image navigation

technology in spine surgery. We examine the safety, accuracy, and

eﬀectiveness of navigated iliac bolt placement while minimizing

challenges associated with current techniques.

Study Design: Patient Sample:

Five patients requiring lumbopelvic ﬁxation for multiple indications,

including lumbosacral pseudoarthrosis, complex sacral fracture

patterns, compromised revision sacral ﬁxation, and as an adjunct

to degenerative deformity with multilevel fusion, underwent

navigated iliac bolt placement.

Outcome Measures:

Accurate placement was veriﬁed using intraoperative computed

tomography (CT) imaging using O-ARM (Medtronic, Inc.) after

placement.

Methods:

Five patients requiring lumbopelvic ﬁxation have undergone

navigated iliac bolt placement using Medtronic Stealth Station

Treon in conjunction with the O-ARM (Medtronic, Inc.). A right

percutaneous posterior superior iliac spine (PSIS) reference frame

was placed at the superior lateral margin of the PSIS, and bilateral

iliac bolts were placed via navigation using both the anatomic and

traditional surgical techniques. Both techniques were performed

without direct notch palpation and minimal soft-tissue exposure.

Postplacement intraoperative CT imaging was obtained to conﬁrm

position and trajectory of the bolts using O-ARM (Medtronic, Inc.).

Results:

Ten iliac bolts were successfully placed in ﬁve patients. Intraopera-

tive CT demonstrated ideal iliac screw bone placement projecting

within 2 cm over sciatic notch, between pelvic tables. With image

navigation, both anatomic and traditional iliac bolt placement tech-

niques were performed with less surgical exposure, no radiation

exposure, and complete accuracy using image navigation tech-

niques with a percutaneous reference frame. The percutaneous

reference frame placed in the superior lateral PSIS did not cause

any interference with our navigated trajectory or bolt.

Conclusion:

Image-navigated iliac ﬁxation allows for safe and accurate placement

of bilateral iliac bolts without PSIS percutaneous reference frame

interference. Image guidance eliminates ﬂuoroscopic radiation

exposure and extensive soft-tissue dissection and facilitates both

traditional and anatomic iliac bolt placement techniques.

Abstract

TABLE OF CONTENTS

SPINE & ORTHO

FORWARD

BACK

Use of intraoperative computed tomography scanning in

determining the magnitude of arthroscopic osteochondroplasty

Moﬁdi A, Shields JS, Tan JS, Poehling GG, Stubbs AJ.

Arthroscopy. 2011 Jul

Femoroacetabular impingement has recently become a recognized

cause of disability and hip arthritis. Hip arthroscopy and femoro-

acetabular reshaping have been performed to treat this condition.

Quantiﬁcation of the excess femoral and acetabular bone requiring

resection has been challenging with the less invasive arthroscopic

technique. We describe the use of intraoperative computed tomog-

raphy assessing osteochondroplasty during arthroscopic surgery to

treat cam- and pincer-type femoroacetabular impingement. We also

describe the technical steps and present the important radiologic

ﬁndings we have been able to visualize.

We found intraoperative computed tomography scanning to be a

reliable and reproducible method of assessing the quality of femo-

roacetabular impingement surgery. We believe that femoroacetabu-

lar impingement surgery can be assessed intraoperatively by use of

computed tomography scanning where corrections can be made if

necessary.

Abstract

TABLE OF CONTENTS

SPINE & ORTHO

FORWARD

BACK

O-arm based spinal navigation and intraoperative 3D-imaging:

rst experiences

Gonschorek S. Hauck U. Spiegl T. Weis

Department of Spinal Surgery, Trauma Center, BGU-Murnau, Germany

Eur J Trauma Emerg Surg, March 2011

Since the ﬁrst use of instrument-tracking techniques in the early

1990s, image-guided technologies became a leading topic in all

branches of spine surgery. Today, navigation is a idely available tool

in spine surgery and has become a part of clinical routine in many

centers for a large variety of indications. Spinal navigation may not

only contribute to more precision during surgery, but it may also

reduce radiation exposure and ﬁuoroscopy time, with advantages

not only for the patient but also for the operating room personnel.

Diﬀerent registration algorithms have been developed diﬀering

in terms of the type of image data used by the navigation system

(preoperatively acquired computed tomography [CT] images, intra-

operatively acquired ﬁuoroscopy images) and the way virtual and

physical reality is matched.

There is a tendency toward a higher accuracy for 3D ﬁuoroscopy-

based Registration algorithms. The 0-arm represents a new ﬁat-

panel technology with the source and detector moving in a 360 arc

around the patient. In combination with the Stealth station system,

navigation may start immediately after automated registration with

already referenced instruments. After instrumentation, an additional

scan may conﬁrm intraoperatively the correct positioning of the

instrumenttation. The ﬁrst experiences with the system are

described in this paper.

Abstract

TABLE OF CONTENTS

SPINE & ORTHO

FORWARD

BACK

There is a relatively high incidence of screw misplacement during

spinal instrumentation due to distortion of normal anatomy

following spinal trauma. The O-arm® is the next-generation spinal

navigation tool that provides intraoperative 3-D imaging for

complex spine surgeries. In this prospective study over 1-month

period, 25 patients (mean age 29.16 years (range 7-58 years), 22

(88%) males) with spinal injury who underwent spinal instrumenta-

tion under O-arm® guidance were included.

Fall from height (64%) was the most common etiology seen in 16

patients. The majority (68%) had dorsolumbar fractures. Spinal canal

compromise was seen in 21 patients (84%). Ten patients (40%) had

American Spinal Injury Association (ASIA) grade A injuries, two pa-

tients (8%) had grade B, ﬁve patients (20%) had grade C, four

patients (16%) each had grade D, and grade E injuries.

A total of 140 screws were inserted under O-arm guidance. Of these,

113 (81%) were dorsolumbar pedicle screws, 2 were odontoid

screws, 12 were anterior cervical screws, and 12 screws (48%) were

lateral mass screws. Mean duration of surgery was 4.5 h with a mean

blood loss of 674 mL. The mean postoperative stay was 6.3 days.

None of the patients had screw misplacement ort canal breach. No

patient deteriorated in ASIA grade postoperatively. The system was

rated as excellent for ease of use by all faculty using the system.

Accurate screw placement provides better patient safety and

reduces the in hospital stay thereby leading early patient mobiliza-

tion and may reduce the cost incurred in patient management.

Abstract

Use of O-arm for spinal surgery in academic institution in India:

Experience from JPN apex trauma centre

Pankaj Ailawadhi et al

Department of Neurosurgery, JPN Apex Trauma Centre, All India Institute of Medical

Sciences, New Delhi, India

Neurology India 2011

TABLE OF CONTENTS

SPINE & ORTHO

FORWARD

BACK

Evaluation of the rate of decompression in anterior cervical

corpectomy using an intra-operative computerized tomography scan

(O-arm® system)

Francesco Costa et al

Neurosurgery Department- Istituto Clinico Humanitas,

Istituto IRCCS Galeazzi Milan, Italy

European Spine Journal 2011

Object:

The purpose of this study was to evaluate the eﬃcacy of intra-

operative computerized tomography (CT) scanning in the analysis

of bone removal accuracy during anterior cervical corpectomy, in

order to allow any necessary immediate correction in the event of

inadequate bone removal.

Methods:

From September 2009 to December 2010 we performed an intra-

operative (CT) scan using the O-Arm™ Image system to assess the

rate of central and lateral decompression in all patients treated for

cervical spondylotic myelopathy by anterior cervical corpectomy

and fusion.

Results:

Out of a population of 187 patients admitted to our department,

with a diagnosis of myelopathy due to spondylotic degenerative

cervical stenosis, 15 patients underwent a surgical treatment with

anterior cervical corpectomy and fusion. There were nine males

(60%) and six females (40%); the mean age was 52.4 years, ranging

from 41 to 57 years.

The pre-operative radiologic investigations (MRI and CT scans)

revealed in the nine patients (60%) the extent of the compression to

one vertebral body (C4 one case, C5 four cases, C6 four cases), while

in the six cases (40%) the compression regarded two vertebral body

(C3 and C4 one case, C4 and C5 two cases, C5 and C6 three cases).

During surgery, when the decompression was judged completely,

a CT scan was performed: in 11 cases (73.3%) the decompression

was considered adequate, while in four cases (26.7%) it was deemed

insuﬃcient and the surgical strategy was changed in order to opti-

mize the bone removal. In these cases an additional scan was taken

to prove the eﬃcacy of decompression, achieved in all patients.

Conclusion:

Intra-operative CT scan performed during cervical corpectomy is a

really useful tool in helping to ensure complete bone removal and

the adequacy of surgery. The O-arm™ Image system grants optimal

image quality, allowing correctly assessing the rate of decompres-

sion and, in any case of doubt, allows an intra-operative evaluation

of the ﬁnal correct positioning of the graft.

Abstract

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e Accuracy of Intraoperative O-arm Images for the

Assessment of Pedicle Screw Position.

Santos ER, Ledonio CG, Castro CA, Truong WH, Sembrano JN.

Department of Orthopaedics, University of Minnesota

Spine 2011 Jun

Study Design: Human cadaveric study

Objective: The objective of the study was to determine the

accuracy of intraoperative O-arm images in determining pedicle

screw position using open dissection as the gold standard.

Summary of Background Data: Pedicle screws are widely

used in the treatment of various spinal disorders. Post-operative CT

scans are the imaging gold standard to detect pedicle screw mal-

position. However, a second procedure is necessary if such malpo-

sitioned screws have to be revised. The O-arm is an intraoperative

scanner that allows revision of a screw without having to return the

patient to the OR for a separate procedure. No previous studies have

looked at the accuracy of intraoperative O-arm images in

determining pedicle screw position.

Methods: This factorial validation study utilized 9 cadavers in a

comparison of intraoperative O-arm images and the dissection gold

standard. Four hundred sixteen screws were inserted using three-

dimensional image (O-arm) guidance from C2 to S1. The screw

positions were randomized into three groups:

“IN” (fully contained within the pedicle), “OUT-lateral” or “OUT-

medial”. After screw insertion, O-arm images were obtained and

reviewed in a blinded fashion by three independent observers.

Dissection identiﬁed the true position of the screws. Speciﬁcity,

sensitivity, positive predictive value (PPV) and negative predictive

value (NPV) were calculated using dissection results as the gold

standard. The interobserver reliability was also determined.

Results: The overall accuracy, speciﬁcity, sensitivity, PPV, and NPV

of O-arm images for the thoracic and lumbar spine were 73%, 76%,

71%, 74%, and 72%, respectively. Accuracy of surgeon perception in

the cervical spine was signiﬁcantly less than in the thoracic and

lumbosacral spine. There was substantial interobserver agreement

between the three readers.

Conclusion: Intraoperative O-arm images accurately detect

signiﬁcant pedicle screw violations in the thoracic and lumbosacral

spine, but are less accurate for the cervical spine.

Abstract

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O-arm guided balloon kyphoplasty: preliminary experience

of 16 consecutive patients

Schils F.

Department of Neurosurgery, Clinique Saint Joseph, Liège, Belgium

Acta Neurochir Suppl. 2011

Balloon kyphoplasty is now widely used for the treatment of

vertebral compression fractures. Excellent pain relief is achieved

with cement injection, but the safety of the procedure relys on

excellent radiological exposure. The balloon kyphoplasty technique

is usually performed using one or two C-Arm devices to allow

correct antero-posterior (AP) and lateral view throughout the

surgical procedure. By deﬁnition, this minimal invasive spine

surgery is associated with radiation exposure for both the patient

and the surgeon. In our center, we recently moved from this way

of proceeding to the use of an O-Arm image guidance system to

perform cement augmentation in vertebral fractures.

To our knowledge, there is no clinical series describing the O-arm

use in a balloon kyphoplasty procedure published in the scientiﬁc

literature. We prospectively evaluate on 16 consecutive patients,

the feasibility of the O-Arm guided kyphoplasty procedure with the

original, usual tools, and we measured the ﬂuoroscopy time and the

X-ray exposure. We didn’t experience any device related problem

and demonstrated a signiﬁcant reduction of X-ray exposure and

time of ﬂuoroscopy. We believe that using this new intraoperative

system, the overall time of surgery and ﬂuoroscopy could still be

reduced in a near future.

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Validity of surgeon perception of navigated pedicle screw position:

a cadaveric study.

Santos ER, Ledonio CG, Castro CA, Truong WH, Sembrano JN.

Department of Orthopaedics, University of Minnesota

Spine 2011 Jul

Study Design:

Human Cadaveric Experimental Study.

Objective:

To determine the validity of surgeon perception of pedicle screw

position inserted using intraoperative three-dimensional (O-arm)

image-guided screw insertion.

Summary of Background Data:

A surgeon’s ability to detect pedicle wall violations intraoperatively

is crucial for optimal pedicle screw placement. Accuracy of use of

a probe or sound to assess pedicle breach is not optimal and may

require experience. Intraoperative navigation has been shown

to improve screw placement accuracy. It has not been shown,

however, whether navigation in combination with screw tract

palpation can further increase the surgeon’s ability to detect a

pedicle breach in pedicle screw placement in the cervical, thoracic,

and lumbosacral spine.

Methods:

Four hundred eighteen screws were inserted using three-dimension-

al image guidance transpedicularly from C2 to S1 in 10 fresh frozen

cadavers. Screw tracts were created using navigation and then

probed. After probing, the surgeon stated whether he perceived

that the screw would be in, out laterally, or out medially. After screw

insertion for all the levels, open dissection was then performed to

determine the actual pedicle screw position. The surgeon’s percep-

tion of screw position was compared to the dissection results.

Results:

The overall speciﬁcity, sensitivity, positive predictive value, and

negative predictive value of the surgeon perception of pedicle

screw position were 87%, 80%, 78% and 88%, respectively. Accuracy

of surgeon perception of pedicle screw position was signiﬁcantly

less than in the cervical spine when compared with thoracic and

lumbosacral spine.

Conclusion:

Surgeon perception of a navigated pedicle screw position is accurate

in the thoracic and lumbar spine. Detection of pedicle screw viola-

tions by surgeon perception in the cervical spine is less accurate

and does not reliably lead to accurate screw placement.

Abstract

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Modied transcorporeal anterior cervical microforaminotomy

assisted by O-arm-based navigation: a technical case report.

Kim JS, Eun SS, Prada N, Choi G, Lee SH.

Wooridul Spine Hospital, 47-4 Chungdam-dong, Gangnam-gu, Seou

Eur Spine J. 2011 Jul

This study was done to present our surgical experience of modi-

ﬁed transcorporeal anterior cervical microforaminotomy (MTACM)

assisted by the O-arm-based navigation system for the treatment

of cervical disc herniation. We present eight patients with foraminal

disc herniations at the C5-C6, C6-C7, and C7-T1 levels. All patients

had unilateral radicular arm pain and motor weakness. The inclusion

criteria for the patients were the presence of single-level unilateral

foraminal cervical disc herniation manifesting persistent radiculopa-

thy despite conservative treatment. Hard disc herniation, down-

migrated disc herniation, concomitant moderate to severe bony spur

and foraminal stenosis were excluded. We performed MTACM to

expose the foraminal area of the cervical disc and removed the

herniated disc fragments successfully using O-arm-based navigation.

Postoperatively, the patients’ symptoms improved and there was no

instability during the follow-up period. MTACM assisted by O-arm-

based navigation is an eﬀective, safe, and precise minimally invasive

procedure that tends to preserve non-degenerated structures as

much as possible while providing a complete removal of ruptured

disc fragments in the cervical spine.

Abstract

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Image-guided placement of occipitocervical instrumentation using a

reference arc attached to the headholder.

Nottmeier EW, Young PM.

Department of Neurosurgery, Mayo Clinic, Jacksonville, FL

Neurosurgery. 2010 Mar

Objective:

To develop a safe and accurate method of image-guided placement

of instrumentation in the upper cervical spine and occiput in which

the reference arc is ﬁxed to the headholder.

Methods:

The authors describe a technique for placing screws at the occipital,

C1, and C2 levels using 3-dimensional image guidance in which

the reference arc is ﬁxed to the headholder. Technical details are

discussed as well as modiﬁcations to the technique to maximize

navigation accuracy and decrease the need for re-registration. One

of 2 paired systems, the BrainLAB Vector Vision system (BrainLAB

Inc., Westchester, IL) used in conjunction with the Arcadis Orbic

Isocentric C-arm (Siemens Medical Solutions, Erlangen, Germany)

or the Stealth Treon system (Medtronic, Littleton, MA) paired with

the O-arm (Medtronic), was used for image guidance in this study. A

total of 18 patients had 82 screws placed at the occipital, C1, or C2

level using this technique. An independent radiologist interpreted

postoperative computed tomographic scans of these patients and

graded the screws for bony breach.

Results:

No complications resulted from the use of image guidance or from

the placement of instrumentation. Postoperative computed tomog-

raphy revealed 1 screw with a minimal breach of the outer lamina

of C2. Another screw was replaced intraoperatively secondary to a

minimal bony breach. No other bony breach occurred.

Conclusion:

This technique allows safe and accurate placement of instrumenta-

tion in the posterior occipitocervical junction using 3-dimensional

image guidance in which the reference arc is attached to the

headholder.

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ree-dimensional image-guided placement of S2 alar screws to

adjunct or salvage lumbosacral xation.

Background Context: Achieving fusion across the lumbosa-

cral junction is challenging because of the unfavorable biomechan-

ics associated with ending a fusion at this level. Bicortical placement

of S1 pedicle screws can increase the construct stability at the

lumbosacral junction; however, construct failure and pseudoarthro-

sis can still result. Iliac screws have been shown to increase the stiﬀ-

ness of lumbosacral constructs, but disadvantages include diﬃculty

in connecting the iliac screw to adjacent sacral screws, painful screw

loosening or prominence requiring removal, and the inability to

place the screws in some patients with previous iliac crest autograft

harvest.

Purpose: The purpose of the study is to describe a technique of S2

alar screw placement using three-dimensional image guidance.

Study Design/Setting:

The study design is a retrospective analysis.

Patient Sample: Twenty patients undergoing lumbosacral fu-

sion had 32 screws placed using this technique.

Outcome Measures: An independent radiologist graded

screw placement and lumbosacral fusion on thin-cut postoperative

computed tomographic (CT) scans.

Methods: Image guidance in this study was accomplished with

the Medtronic Stealth Station Treon (Medtronic Inc., Littleton, MA,

USA) used in conjunction with the O-ARM (Medtronic Inc.).

Indications for placement of S2 alar screws included the following:

to adjunct S1 pedicle screws in multilevel fusion cases; as an adjunct

or alternative to S1 pedicle screws in pseudoarthrosis revision cases

in which the S1 screws had loosened; as an alternative to S1 pedicle

screws in cases where medial trajectory of an S1 pedicle screw was

diﬃcult to obtain because of a low-set lumbosacral junction; and

a combination of the above. The entry point of the screw was typi-

cally chosen lateral and superior to the S2 dorsal foramen with

the trajectory directed anterior, inferior, and lateral. Attempt was

made to place the screw with the tip purchasing, but not penetrat-

ing through, the triangular area of cortical bone that can be found

at the anterior, inferior, and lateral boundary of the sacral ala. An

independent radiologist graded the placement of the screws on the

intraoperative CT scan obtained with the O-ARM or on postopera-

tive CT scans. Lumbosacral fusion was assessed on postoperative CT

scans obtained at follow-up.

Results: No complications occurred in this study as a result of S2

alar screw placement or image guidance. Five screws did penetrate

the anterior cortex of the sacrum, with no clinical consequence.

At the time of abstract submission, 16 patients were able to have

follow-up CT scans, 15 of which were graded as solid fusion at the

lumbosacral junction by the grading radiologist.

Conclusion: Three-dimensional image guidance allows for safe

placement of large S2 sacral alar screws that can provide

additional biomechanical stability to lumbosacral constructs or

serve as an alternate point of sacral ﬁxation when S1 pedicle

screws cannot be salvaged or placed in a medial trajectory.

Abstract

Nottmeier EW, Pirris SM, Balseiro S, Fenton D. Department of Neurosurgery, Mayo Clinic,

Jacksonville, FL - Spine J. 2010 Jul

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Pedicle screw xation under navigation guidance based on O-arm.

Jin-Sung Kim et al.

Department of Neurosurgery, Wooridul Spine Hospital . Korea

The internet Journal of Minimally Invasive Spinal Technology. 2010 Supplement

Objectives:

The purpose of this study is to describe a surgical technique and the

accuracy of pedicle screw ﬁxation under navigation guidance based

on O-arm.

Design:

Prospective study Methods: Instrumentation using transpedicular

screw ﬁxation was performed using navigation guidance based

on O-arm with 19 patients (78 screws). Evaluation of screw place-

ment in every case was done on each instrumented vertebra by

using intraoperative O -arm and plain X-ray. Screw placements were

graded as good if the screws were placed in the central core of the

pedicle and the cancellous portion of the body. Screw placements

were graded as fair if the screws were placed slightly eccentrically,

causing erosion of the pedicle cortex, and with less than a 2-mm

perforation of the pedicular cortex. Screw placements were graded

as poor if the screws were placed eccentrically with large portion of

the screw extending outside the cortical margin of the pedicle and

with more than a 2-mm perforation of the pedicular cortex, causing

erosion of the pedicle cortex, and with less than a 2-mm perforation

of the pedicular cortex.

Results:

1 patient was excluded due to connection error between O-arm and

navigation. A total 72 pedicle screws were placed in 18 patients.

94.4% (68/72) were categorized as good; 5.6% (4/72), fair; and 0%

were poor. All 4 fair screws were placed extending lateral margin

of the pedicle without any neurologic complications. Conclusions:

Aided by navigation guidance based on O-arm, surgeons can more

safely navigate complex anatomy, and more accurately complete

the procedure making this technology particularly helpful for

pedicle screw ﬁxation. This technique also makes complete avoid-

ance of radiation exposure to surgeons while increasing accuracy

and reliability of the surgical procedure for pedicle screw ﬁxation

Abstract

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Improving accuracy and reducing radiation exposure in minimally

invasive lumbar interbody fusion.

Wood MJ, Mannion RJ.

Department of Neurosurgery, The Princess Alexandra Hospital, Brisbane, Australia

J Neurosurg Spine. 2010 May

Objective:

The authors assessed the accuracy of placement of lumbar transpe-

dicular screws by using a computer-assisted, imaged-guided, mini-

mally invasive technique with continuous electromyography (EMG)

monitoring.

Methods:

This was a consecutive case series with prospective assessment of

procedural accuracy. Forty-seven consecutive patients underwent

minimally invasive lumbar interbody fusion and placement of

pedicle screws (PSs). A computer-assisted image guidance system

involving CT-based images was used to guide screw placement,

while EMG continuously monitored the lumbar nerve roots at the

operated levels with a 5-mA stimulus applied through the pedicle

access needle. All patients underwent CT scanning to determine

accuracy of PS placement. All episodes of adjusted screw trajectory

based on positive EMG responses were recorded. Pedicle screw

misplacement was deﬁned as breach of the pedicle cortex by the

screw of more than 2 mm.

Results:

Two hundred twelve PSs were inserted in 47 patients. The screw mis-

placement rate was 4.7%. One patient experienced new postopera-

tive radiculopathy resulting from a sacral screw that was too long,

with lumbosacral trunk impingement. The trajectory of the pedicle

access needle was altered intraoperatively on 20 occasions (9.4% of

the PSs) based on positive EMG responses, suggesting that nerve

root impingement may have resulted from these screws had the

EMG monitoring not been used.

Conclusion:

The combination of computer-assisted navigation combined with

continuous EMG monitoring during pedicle cannulation results in

a low rate of PS misplacement, with avoidance of screw positions

that might cause neural injury. Furthermore, this technique allows

reduction of the radiation exposure for the surgical team without

compromising the accuracy of screw placement.

Abstract

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Minimally invasive pedicle screw xation utilizing O-arm uoroscopy

with computer-assisted navigation: Feasibility, technique, and

preliminary results.

Abstract

Park P, Foley KT, Cowan JA, Marca FL.

Department of Neurosurgery, University of Michigan Health System, Ann Arbor, MI, USA

Surg Neurol Int. 2010 Aug

Background:

Pedicle screw misplacement is relatively common, with reported

rates ranging up to 42%. Although computer-assisted image guid-

ance (CaIG) has been shown to improve accuracy in open spinal

surgery, its use in minimally invasive procedures has not been as

well evaluated. We present our technique and review the results

from a cohort of patients who underwent minimally invasive lumbar

pedicle screw placement utilizing the O-arm imaging unit in

conjunction with the StealthStation Treon System.

Methods:

A retrospective review of patients who underwent minimally

invasive pedicle screw ﬁxation with CaIG was performed. Eleven

consecutive patients were identiﬁed and all were included. Nine

patients underwent a single-level transforaminal lumbar interbody

fusion. Two patients underwent multi-level fusion. Inaccurate

pedicle screw placement was determined by postoperative

computed tomography (CT) and graded as 0-2, 2-4, 4-6, or 6-8 mm.

Results:

A total of 52 screws were placed. Forty screws were inserted in eight

patients who had postoperative CT, and a misplacement rate of

7.5% was noted including one lateral and two medial breaches. All

breaches were graded as 0-2 mm and were asymptomatic. In the

remaining three patients, post-instrumentation O-arm imaging did

not demonstrate pedicle screw misplacement.

Conclusion:

Although this initial study evaluates a relatively small number of

patients, minimally invasive pedicle screw ﬁxation utilizing the

O-arm and StealthStation for CaIG appears to be safe and accurate.

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An assistive image-guided surgical robot system using o-arm uoros-

copy for pedicle screw insertion: preliminary and cadaveric study.

Abstract

Kim S, Chung J, Yi BJ, Kim YS.

Hanyang University, Seoul. Kyushu University, Fukuoka, Japan

Neurosurgery. 2010 Dec

Background:

The biplane ﬂuoroscopy guided robot system (BFRS) was developed

for surgical robotic systems, minimally invasive surgeries, and coop-

erative robotic systems, as well as enhanced surgical planning and

navigation with preoperative and intraoperative image data.

Objective:

To propose a novel surgical robot system for percutaneous

pedicle screw insertion.

Methods:

The BFRS consists of an O-shaped biplane ﬂuoroscope (O-arm),

a surgical planning and operating system, and an assistive robot.

Each part of the BFRS has a role in conducting percutaneous

pedicle screw placements. To evaluate BFRS accuracy, each part

was analyzed, and to assess the safety and feasibility of percutane-

ous pedicle screw insertions with the BFRS, cadaveric studies

involving 14 levels in the thoracic and lumbar spine regions

were conducted on 2 cadavers.

Results:

Errors in each part of the system and within the entire system were

evaluated. The accuracy of generating coordinates using O-arm

images was 0.30 ± 0.15 mm. The robot demonstrated a duplication

value of 4.97 μm RMS and an accuracy of 0.358 mm RMS. Total

system error was 1.38 ± 0.21 mm. The results of the cadaveric stud-

ies show that inserted pedicular screws were adequately located

within the spine with no unexpected malpositioning of the screws.

The axial angle diﬀerence between planned and postoperative data

was 2.45 ± 2.56°, and the sagittal angle diﬀerence was 0.71 ± 1.21°.

Conclusion:

The BFRS might be helpful in improving the accuracy of percuta-

neous pedicular screw insertion procedures. In the future, we will

attempt to improve the accuracy and reliability of the BFRS and to

determine new clinical applications for the BFRS.

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Minimally invasive image-guided direct repair of bilateral L-5 pars

interarticularis defects.

Brennen, R, et al.

Technical Note. Neurosurgery Focus 2008

Objective:

Lower back pain from spondylolysis historically has been treated

with a variety of options ranging from conservative care to open

fusion.

The authors describe the novel technique of minimally invasive

bilateral pars interarticularis screw placement by utilizingintraop-

erative 3D imaging and frameless navigation in a 17-year-old male

athlete. This technique is a modiﬁcation of the open technique ﬁrst

described in 1970 by Buck and has the advantages of minimal

dissection requirements with improved screw trajectory

visualization.

The patient’s postoperative course is discussed, followed by a brief

literature review of pars interarticularis defect treatment.

Conclusion:

We described a modiﬁed form of the Buck screw procedure with

a minimally invasive, image-guided method of pars interarticularis

ﬁxation. The utilization of image guidance simpliﬁes the otherwise

diﬃcult visualization required for pars interarticularis screw place-

ment and allows minimal skin and muscle dissection, which may

translate into a more rapid postoperative recovery. Future applica-

tions of frameless navigation in the spine may allow such

uncommon hardware applications to be both successful

and less invasive.

Abstract

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Computer-Assisted Surgical Planning and Image-Guided Surgical

Navigation in Refractory Adult Scoliosis Surgery: Case Report and

Review of the Literature

Objective:

Objective: In this case report, we present the utility of computer-

assisted surgical planning and image-guided surgical navigation in

the planning and execution of a major osteotomy to correct severe

kyphoscoliosis.

Summary of Background Data:

Computer-assisted surgical planning is useful to appreciate the

three-dimensional nature of scoliotic deformities and allows for

operative maneuvers to be simulated on a computer before their

implementation in the operating room. Imageguided surgical

navigation improves surgical accuracy and can help translate a

virtual surgical plan to the operative setting.

Methods:

We report the case of a 38- year-old woman with severe, congenital

kyphoscoliosis refractory to many previous surgeries, who presents

with moderate progressive myelopathy and severe pain attributable

to a sharp angular deformity at T12. Three-dimensional computed

tomography reconstruction and computer-assisted surgical plan-

ning were used to determine the optimal corrective osteotomy. The

surgical plan was translated to the operating room where a posteri-

or vertebrectomy and instrumented correction were executed with

the aid of image-guided surgical navigation.

Results:

The osteotomy was safely performed resulting in improved

sagittal and coronal alignments, as well as, correction of the sharp

kyphoscoliotic deformity at the thoracolumbar junction. At 6-month

follow-up, the patient’s myelopathy and pain had largely resolved

and she expressed high satisfaction with the procedure.

Conclusion:

We advocate this novel application of virtual surgical planning and

intraoperative surgical navigation to improve the safety and eﬃcacy

of complex spinal deformity corrections.

Abstract

Metz, LN & Burch S.,

Spine Journal 33(9): E287-E292

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Intraoperative computed tomography for deep brain stimulation

surgery: technique and accuracy assessment.

Background:

The eﬃcacy of deep brain stimulation (DBS) is highly dependent on

the accuracy of lead placement.

Objective:

To describe the use of intraoperative computed tomography (iCT)

to conﬁrm lead location before surgical closure and to study the

accuracy of this technique.

Methods:

Fifteen patients underwent awake microelectrode-guided DBS

surgery in a stereotactic frame. A portable iCT scanner (Medtronic

O-arm) was positioned around the patient’s head throughout the

procedure and was used to conﬁrm lead location before ﬁxation

of the lead to the skull. Images were computationally fused with

preoperative magnetic resonance imaging (MRI), and lead tip

coordinates with respect to the midpoint of the anterior commis-

sure-posterior commissure line were measured. Tip coordinates

were compared with those obtained from postoperative MRI.

Results:

iCT was integrated into standard frame-based microelectrode-

guided DBS surgery with a minimal increase in surgical time or

complexity. Technically adequate 2-dimensional and 3-dimensional

images were obtained in all cases. Head positioning and ﬁxation

techniques that allow unobstructed imaging are described. Lead tip

measurements on iCT fused with preoperative MRI were statistically

indistinguishable from those obtained with postoperative MRI.

Conclusion:

iCT can be easily incorporated into standard DBS surgery, replaces

the need for C-arm ﬂuoroscopy, and provides accurate intraopera-

tive 3-dimensional conﬁrmation of electrode tip locations relative

to preoperative images and surgical plans. iCT fused to preoperative

MRI may obviate the need for routine postoperative MRI in DBS

surgery. Technical nuances that must be mastered for the eﬃcient

use of iCT during DBS implantation are described.

Abstract

Shahlaie K, Larson PS, Starr PA.

University of California, San Francisco and San Francisco Veterans Aﬀairs Medical

Center, San Francisco, California, USA

Neurosurgery. 2011 Mar

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Frameless deep brain stimulation using intraoperative

O-arm technology

Abstract

Adam P. Smith, M.D., and Roy A. E. Bakay, M.D.

Department of Neurosurgery, Rush University Medical Center, Chicago, Illinois

J Neurosurg / April 15, 2011

Objectve:

Correct lead location in the desired target has been proven to be

a strong inﬂuential factor for good clinical outcome in deep brain

stimulation (DBS) surgery. Commonly, a surgeon’s ﬁrst reliable

assessment of such location is made on postoperative imaging.

While intraoperative CT (iCT) and intraoperative MR imaging have

been previously described, the authors present a series of frameless

DBS procedures using O-arm iCT.

Methods:

Twelve consecutive patients with 15 leads underwent frameless DBS

placement using electrophysiological testing and O-arm iCT. Initial

target coordinates were made using standard indirect and direct

assessment. Microelectrode recording (MER) with kinesthetic re-

sponses was performed, followed by microstimulation to evaluate

the side-eﬀect proﬁle. Intraoperative 3D CT acquisitions obtained

between each MER pass and after ﬁnal lead placement were fused

with the preoperative MR image to verify intended MER movements

around the target area and to identify the ﬁnal lead location. Tip

coordinates from the initial plan, ﬁnal intended target, and actual

lead location on iCT were later compared with the lead location on

postoperative MR imaging, and euclidean distances were calcu-

lated. The amount of radiation exposure during each procedure was

calculated and compared with the estimated radiation exposure if

iCT was not performed.

Results:

The mean euclidean distances between the coordinates for the

initial plan, ﬁnal intended target, and actual lead on iCT compared

with the lead coordinates on postoperative MR imaging were 3.04 ±

1.45 mm (p = 0.0001), 2.62 ± 1.50 mm (p = 0.0001), and 1.52 ± 1.78

mm (p = 0.0052), respectively. The authors obtained good merging

error during image fusion, and postoperative brain shift was mini-

mal. The actual radiation exposure from iCT was invariably less than

estimates of exposure using standard lateral ﬂuoroscopy and

anteroposterior radiographs (p < 0.0001).

Conclusion:

O-arm iCT may be useful in frameless DBS surgery to approximate

microelectrode or lead locations intraoperatively. Intraoperative

CT, however, may not replace fundamental DBS surgical techniques

such as electrophysiological testing in movement disorder surgery.

Despite the lack of evidence for brain shift from the procedure,

iCT-measured coordinates were statistically diﬀerent from those

obtained postoperatively, probably indicating image merging

inaccuracy and the diﬃculties in accurately denoting lead location.

Therefore, electrophysiological testing may truly be the only means

of precisely knowing the location in 3D space intraoperatively. While

iCT may provide clues to electrode or lead location during the

procedure, its true utility may be in DBS

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Comparison of Intraoperative Portable CT Scanners in Skull Base

and Endoscopic Sinus Surgery: Single Center Case Series

David B. Conley et al.

Northwestern University Feinberg School of Medicine, Chicago

Skull Base 2011

Precise and safe management of complex skull base lesions can be

enhanced by intraoperative computed tomography (CT) scanning.

Surgery in these areas requires real-time feedback of anatomic

landmarks.

Several portable CT scanners are currently available. We present

a comparison of our clinical experience with three portable

scanners in skull base and craniofacial surgery. We present clinical

case series and the participants were from the Northwestern

Memorial Hospital. Three scanners are studied: one conventional

multidetector CT (MDCT), two digital ﬂat panel cone-beam CT

(CBCT) devices.

Technical considerations, ease of use, image characteristics, and

integration with image guidance are presented for each device.

All three scanners provide good quality images. Intraoperative

scanning can be used to update the image guidance system in

real time. The conventional MDCT is unique in its ability to resolve

soft tissue.

The ﬂat panel CBCT scanners generally emit lower levels of radia-

tion and have less metal artifact eﬀect. In this series, intraoperative

CT scanning was technically feasible and deemed useful in surgical

decision-making in 75% of patients.

Intraoperative portable CT scanning has signiﬁcant utility in

complex skull base surgery. This technology informs the surgeon

of the precise extent of dissection and updates intraoperative

stereotactic navigation.

Abstract

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Advancements in computed tomography management of

chronic rhinosinusitis

Leung, Randy et al

American Journal of Rhinology & Allergy, 2011

Background:

Advances in cone beam computed tomography (CBCT) technology

have allowed for reduction in radiation dosages as well as the

miniaturization of CT scanner units. This has given rise to new

applications for CT scanning, including point-of-care (POC) in-

oﬃce and intraoperative applications.

Methods:

A review of recent changes to radiological modalities as applied to

otolaryngology-head and neck surgery was performed. A discussion

of the physics, applications, and role of diagnostic imaging in the

evaluation of chronic rhinosinusitis (CRS) is conducted.

Results:

The adaptation of cone beam technology has allowed for the

practical implementation of CT scanning at the bedside, be it in

the clinic or operating room setting.

Conclusion:

Given their relative low cost, ease of storage, and low-dose

radiation exposure, POC-CT scanners have become an indispens-

able tool in the diagnosis and treatment of CRS. In the setting of

increasing antibiotic costs, overtreatment with antibiotics, and

fewer required return visits, POC-CT challenges the conventional

role of empiric medical therapy before progression to imaging for

the diagnosis of CRS.

Abstract

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CRANIAL & ENT

Intraoperative use of the Medtronic O-arm for deep brain

stimulation procedures.

Caire F, Gantois C, Torny F, Ranoux D, Maubon A, Moreau JJ.

Service de Neurochirurgie, Centre Hospitalier Universitaire de Limoges, Hôpital Du-

puytren, Limoges, France.

Stereotact Funct Neurosurg. 2010

The purpose of this study was to analyze the feasibility and utility

of 3D imaging to help lead positioning during a deep brain stimula-

tion (DBS) procedure. A bilateral subthalamic DBS procedure was

conducted in 2 patients for idiopathic Parkinson’s disease. Subtha-

lamic nucleus targeting was based on preoperative stereotactic MRI.

We used the Medtronic O-arm to perform 2D-imaging control

(frontal and lateral) as well as quick (<30 s) 3D acquisition. This

allowed us to check the positioning of micro-macro electrodes and

deﬁnite electrodes. 3D images were fused with postoperative CT

to assess their accuracy, and with preoperative MRI to visualize the

anatomical location of the electrodes.

3D imaging is a quick and safe method to ensure perioperative

control of lead placement during DBS procedures.

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CRANIAL & ENT

Real-Time Intraoperative Computed Tomography to Assist

Cochlear Implant Placement in the Malformed Inner Ear

Bloom, J, et al.

Otology & Neurotology January 2009

Objective:

Cochlear implantation is increasingly being performed in children

with inner ear malformations. In severe cochleovestibular anoma-

lies, such as severe partitioning defects and common cavity dyspla-

sia, positioning of the electrode array can be hazardous, with

inadvertent placement into the internal auditory canal (IAC) or

carotid canal being well known. We describe a case in which real-

time intraoperative computed tomographic scanning was used to

help achieve proper electrode positioning in a child with a severe

malformation.

Patient:

Child with common cavity malformations undergoing cochlear

implantation. Intervention: Intraoperative computed tomography

used during implantation procedure.

Main Outcome Measure:

Use of technique in determining electrode position.

Results:

A 10-year-old patient with bilateral common cavity malformations

presented with declining performance in a functioning implant

placed 7 years earlier. The family elected implantation of the contra-

lateral ear. Via a posterior labyrinthotomy approach, a straight array

was placed into the common cavity. Intraoperative computed

tomographic scanning was immediately performed on the

operating room table, showing that the array was in the IAC.

A second attempt with a diﬀerent insertion angle also resulted in

IAC placement. In a third attempt, the electrode was advanced as a

loop, grasping the tip through an adjacent second labyrinthotomy.

Computed tomography conﬁrmed good position against the outer

wall of the cavity.

Conclusion:

Real-time intraoperative computed tomography is a new technol-

ogy with many potential applications in surgery. In our patient, it

allowed rapid and accurate determination of electrode position and

helped achieve ideal placement in a severely malformed inner ear.

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CRANIAL & ENT

Intraoperative Navigation for Minimally Invasive Resection of

Periarticular and Pelvic Tumors

Karl Wu, MD; Nicholas P. Webber, MD; Russell A. Ward, MD; Kevin B. Jones, MD;

R. Lor Randall, MD Huntsman Cancer Institute, Utah, USA.

ORTHOPEDICS May 2011

The surgical approach to benign, metastatic, and some low-grade

malignant tumors is often diﬃcult due to their typically precarious

locations. This article presents a series of cases where intraoperative

stealth navigation was used to treat periarticular tumors. The use of

paired point imaging with image fusion has made approaching

tumors through an accurate and minimally invasive technique a

viable option for the treatment of a subset of musculoskeletal tumors.

Conventional resection of periarticular and pelvic tumors of bone

usually requires an extensive surgical approach to adequately

visualize the tumor and protect the nearby neurovascular struc-

tures. When tumors in periarticular locations are encountered, dis-

location of the aﬀected joint may be necessary, putting periarticular

and subchondral bone at risk for osseous necrosis and articular

surfaces at risk of mechanical insult at the time of dislocation. While

arthroscopic techniques may enable a minimally invasive mode of

surgical approach in certain anatomic locations, this is not always

feasible and can add additional operative time and morbidity to

the patient. This article describes 5 cases where locally aggressive

tumors in challenging periarticular anatomic locations were treated

in a minimally invasive manner with the assistance of image fusion

and paired-point registration.

Results:

All of the patients in this case series had an excellent Musculoskeletal

Tumor Society Functional Score (range, 26–29) postoperatively.

Basic demographic data and postoperative results are listed in the

Table. Average follow-up was 8.8 months (range, 6–16 months).

Musculoskeletal Tumor Society Functional Scores were satisfactory

in all patients. Near-complete relief of preoperative symptoms was

obtained in all patients. Excellent 3-D multiplanar visualization

of the tumor was obtained in all patients, and minimal invasive

approaches were completed successfully by using intraoperative

navigation guidance. No surgery-related complications were

encountered during any of the procedures. Average intraoperative

blood loss was 78 mL (range, 10–100 mL). Average operative time

was 92 minutes (range, 65– 125 minutes).

Abstract

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ONCOLOGY

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Real-time intraoperative computed tomography assessment of

quality of permanent interstitial seed implantation for prostate cancer.

Zelefsky MJ, et al.

Brachytherapy Service, Memorial Sloan-Kettering Cancer Center, New York, NY

Urology. 2010 Nov

Objectives:

To evaluate the use of real-time kilovoltage cone-beam computed

tomography (CBCT) during prostate brachytherapy for intraopera-

tive dosimetric assessment and correcting deﬁcient dose regions.

Methods:

A total of 20 patients were evaluated intraoperatively with a mobile

CBCT unit immediately after implantation while still anesthetized.

The source detector system was enclosed in a circular CT-like

geometry with a bore that accommodates patients in the lithotomy

position. After seed deposition, the CBCT scans were obtained. The

dosimetry was evaluated and compared with the standard post-

implantation CT-based assessment. In 8 patients, the deposited

seeds were localized in the intraoperative CBCT frame of reference

and registered to the intraoperative transrectal ultrasound images.

With this information, a second intraoperative plan was generated

to ascertain whether additional seeds were needed to achieve the

planned prescription dose. The ﬁnal dosimetry was compared with

the postimplantation scan assessment.

Results:

The mean diﬀerences between the dosimetric parameters from the

intraoperative CBCT and postimplant CT scans were < .5% for

percentage of volume receiving 100% of the prescription dose,

minimal dose received by 90% of the prostate, and percentage of

volume receiving 150% of the prescription dose. The minimal dose

received by 5% (maximal dose) of the urethra diﬀered by 8% on

average and for the rectum an average diﬀerence of approximately

18% was observed. After fusion of the implanted seed coordinates

from the intraoperative CBCT scans to the intraoperative transrectal

ultrasound images, the dosimetric outcomes were not signiﬁcantly

diﬀerent from the postimplantation CT dosimetric results.

Conclusion:

Intraoperative CT-based dosimetric evaluation of prostate perma-

nent seed implantation before anesthesia reversal is feasible and

might avert misadministration of dose delivery. The dosimetric

measurements using the intraoperative CBCT scans were

dependable and correlated well with the postimplant diagnostic

CT ﬁndings.

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Optimization of Radiation Exposure and Image Quality of the Cone-

beam O-arm Intraoperative Imaging System in Spinal Surgery.

Abstract

Abul-Kasim K, Söderberg M, Selariu E, Gunnarsson M, Kherad M, Ohlin A.

Skåne University Hospital, Lund University, Malmö, Sweden.

J Spinal Disord Tech. 2011 Mar

Study Design:

Retrospective study.

Objectives:

To optimize the radiation doses and image quality for the

cone-beam O-arm surgical imaging system in spinal surgery.

Summary of Background:

Neurovascular compromise has been reported after screw misplace-

ment during thoracic pedicle screw insertion. The use of O-arm with

or without navigation system during spinal surgery has been shown

to lower the rate of screw misplacement. The main drawback of

such imaging surgical systems is the high radiation exposure.

Methods:

Chest phantom and cadaveric pig spine were examined on the

O-arm with diﬀerent scan settings: 2 were recommended by the

O-arm manufacturer (120 kV/320 mAs, and 120 kV/128 mAs), and 3

low-dose settings (80 kV/80 mAs, 80 kV/40 mAs, and 60 kV/40 mAs).

The radiation doses were estimated by Monte Carlo calculations.

Objective evaluation of image quality included interobserver agree-

ment in the measurement of pedicular width in chest phantom and

assessment of screw placement in cadaveric pig spine.

Results:

The eﬀective dose/cm for 120 kV/320 mAs scan was 13, 26, and 69

times higher than those delivered with 80 kV/80 mAs, 80 kV/40 mAs,

and 60 kV/40 mAs scans, respectively. Images with 60 kV/40 mAs

were unreliable. Images with 80 kV/80 mAs were considered reliable

with good interobserver agreement when measuring the pedicular

width (random error 0.38 mm and intraclass correlation coeﬃcient

0.979) and almost perfect agreement when evaluating the screw

placement (κ value 0.86).

Conclusions:

The radiation doses of the O-arm system can be reduced 5 to 13

times without negative impact on image quality with regard to

information required for spinal surgery.

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IMAGING TECHNOLOGY

e perspectives of users and developers in designing and developing

O-arm imaging system

Park MS, Chung CY, Kwon DG, Huh Y, Lee K, Lee KM.

Department of Orthopedic Surgery, Seoul National University Bundang Hospital

J Xray Sci Technol 2011

A questionnaire survey was performed to investigate the diﬀerent knowledge of radiation exposure, awareness and expectation for

O-arm imaging system between the users (orthopaedic surgeons) and the developers (engineers). A total of 93 orthopaedic surgeons

and 19 engineers participated and answered the questionnaire consisting of 18 items designed for this study.

The items were focused on knowlege, awareness, and expectation. Orthopaedic surgeons had higher scores for items of knowledge

domains regarding radiation exposure than the engineers while the engineers were more sensitive to radiation hazards and adopted

higher levels of radiation protection than orthopaedic surgeons in the awareness domain. Most engineers and orthopaedic surgeons

answered that the requirements of diagnostic and intraoperative imaging systems diﬀer.

Image resolution, a low radiation exposure, and the time required for image acquisition was the top three requirements of O-arm selected

by engineers. On the other hand, the top three requirements according to orthopaedic surgeons were; image resolution, expediency, and

spatial occupancy. User requirements need to be reﬂected in developing O-arm along with basic requirements such as image resolution

and low radiation exposure.

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IMAGING TECHNOLOGY

Comparison Of Operator Radiation Exposure Between C-arm And

O-arm Fluoroscopy For Orthopaedic Surgery

Moon Seok Park, Kyoung Min Lee, Boram Lee, et al.

Department of Orthopedic Surgery, Seoul National University Bundang Hospital

Radiation Protection Dosimetry April 2011

The O-arm system has recently been introduced and has the capability of combined two-dimensional (2-D) ﬂuoroscopy imaging and

three-dimensional computed tomography imaging. In this study, an orthopaedic surgical procedure using C-arm and O-arm systems

in their 2-D ﬂuoroscopy modes was simulated and the radiation doses to susceptible organs to which operators can be exposed were

investigated.

The experiments were performed in four conﬁgurations of the location of the X-ray source and detector. Shielding eﬀects on the thyroid

surface and the direct exposure delivered to the surgeon’s hands were also compared. The results obtained show that the O-arm delivered

higher doses to the sensitive organs of the operator in all conﬁgurations. The thyroid shield cut-oﬀ 89 % of the dose in the posteroanterior

conﬁguration of both imaging systems. Thus, the operators need to pay more attention to managing radiation exposure, especially when

using the O-arm system

Abstract

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IMAGING TECHNOLOGY

Dosimetric characterization of a cone-beam O-arm imaging system.

Zhang J, Weir V, Fajardo L, Lin J, Hsiung H, Ritenour ER.

Medical Physics Section, Department of Radiology, University of Minnesota,

Minneapolis, MN

J Xray Sci Technol. 2009

This study compared patient dose and image quality of a mobile

O-arm cone beam imaging system in the 3D scan acquisition mode

to those of a 64 slice Computed Tomography (CT) imaging system.

The investigation included patient dose, scattered radiation, and

image quality measurements. The patient dose was measured using

a 0.6 cc Farmer ion chamber and 30 cm long Computed Tomogra-

phy (CT) head and body polymethylmethacrylate (PMMA) phantoms.

The results show that under identical radiographic techniques (kVp,

mAs, etc.) and with the same scan length, the O-arm in 3D scan

acquisition mode delivers approximately half the radiation dose of

a 64 slice CT scanner. Scattered radiation was measured at several

locations around the O-arm, at 1 m, 2 m and 3 m distances in 3D

CT scan acquisition mode with a RadCal 10 x 5-180 pancake ion

chamber using a 30 cm long CT body phantom as the source of

scatter. Similar measurements were made in a 64 slice CT scanner.

The data demonstrate that scattered radiation from the O-arm

to personnel involved in a clinical procedure is comparable to that

from a 64 slice CT scanner. Image quality was compared by expos-

ing a CATPHAN phantom to comparable doses in both the O-arm

and the CT scanner. The resultant images were then evaluated for

modulation transfer function (MTF), high-contrast spatial resolution,

and low contrast sensitivity for clinical application purpose. The

O-arm shows comparable high contrast to the CT (7 lp/cm vs. 8 lp/

cm). The low contrast in the O-arm is not visible due to ﬁxed pattern

noise. For image guided surgery applications where the location

of a structure is emphasized over a survey of all image details, the

O-arm has some advantages due to wide radiation beam cover-

age and lower patient dose. The image quality of the O-arm needs

signiﬁcant improvement for other clinical applications where high

image quality is desired.

Abstract

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IMAGING TECHNOLOGY

O Arm Clinical Evidence Eguide