p26. comparison of range of motion following cervical spine decompression surgical procedures and...

113SProceedings of the NASS 23rd Annual Meeting / The Spine Journal 8 (2008) 1S–191S

FDA DEVICE/DRUG STATUS: This abstract does not discuss or include

any applicable devices or drugs.

doi:10.1016/j.spinee.2008.06.265

P24. Radiation Exposure during Orthopaedic CT Scanning

Debdut Biswas, BA1, Jesse Bible, BS1, Michael Bohan, BS2, Peter Whang,

MD1, Jonathan Grauer, MD1; 1Yale University School of Medicine,

Department of Orthopaedics and Rehabilitation, New Haven, CT, USA;2Yale-New Haven Hospital, Department of Radiological Physics, New

Haven, CT, USA

BACKGROUND CONTEXT: Computerized Tomography (CT) scans are

routinely obtained in the evaluation of complex orthopaedic injuries. As

CT exposes patients to the highest doses of ionizing radiation of the med-

ical imaging procedures, there has been increasing concern over this

exposure.

PURPOSE: Several investigations have reported the effective dose of com-

monly performed CTexaminations (Head, Chest, Abdomen, and Pelvis), but

no studies have evaluated the radiation related risks of orthopaedic CT scans.

The purpose of this study was to report the effective radiation dose of CT

scans commonly performed in the evaluation of orthopaedic injuries.

STUDY DESIGN/ SETTING: CT scans of the extremities and spine were

retrospectively reviewed from our institution’s digital imaging archive. The

CT dose index by volume (CTDIvol) was recorded from the dose report for

each examination and was used to calculate the effective dose for each

scan.

PATIENT SAMPLE: Our institution’s digital imaging archive was retro-

spectively reviewed for helical CT scans of adults of the upper and lower

extremities and spine (cervical, thoracic, and lumbar). CT scans of the

chest, abdomen, and pelvis were also included to compare our calculations

to prior studies. The scans were performed on GE Lightspeed 16, Light-

speed Qx/I, Lightspeed VCT scanners.

OUTCOME MEASURES: In the assessment of radiation related risk

from CT, the effective dose (ED) is a useful value that accounts for the

radiosensitivity of specific organs and provides an estimate of the overall

radiation-related risk to the patient. The effective dose of radiation was re-

ported for CT scans of the upper and lower extremities and the cervical and

thoracolumbar spine.

METHODS: The CT dose index by volume (CTDIvol), dose-length prod-

uct (DLP), current-rotation time (mAs), and voltage (kVp) were reported

for each scan. Using the CTDIvol and scan intervals, organ doses and ef-

fective dose calculations were performed according to Monte Carlo tech-

niques and on methods specified in the United Kingdom’s National

Radiological Protection Board’s (NRPB) SR250 publication.

RESULTS: The effective dose estimations for chest, abdomen, and pelvis

scans (5.03, 5.01, and 4.20 mSv, respectively) were similar to those reported

in prior studies. In our study, the ED was particularly high in CT scans of the

spine. The ED of a cervical spine CTwas 3.69 mSv, and the dose of a thoracic

spine CT scan was significantly higher than a chest CT (18.15 vs. 5.03 mSv,

P!0.0001) while a lumbar spine CTwas significantly higher than an abdom-

inal CT (19.60 vs. 5.01 mSv, P!0.000001). In the upper extremity, the ED of

a shoulder CT (1.51mSv) was higher than than the dose of an elbow scan

(0.18mSv) and significantly higher than the dose of a CT of the wrist (0.02

mSv, P50.03). In the lower extremity, the ED of a hip scan (2.91 mSv)

was significantly higher than than dosages of knee (0.18 mSv,

P!0.0000001) and ankle scans (0.04mSv, P!0.0000001).

CONCLUSIONS: The use of CT in orthopaedics allows for the visualiza-

tion of complex fractures and dislocations in the extremities and spine. The

radiation related risks for CT scans of the distal extremities should not be

overemphasized, particularly when the diagnostic information may affect

clinical management. The orthopaedic surgeon, however, should more

carefully consider the benefits of CT scans of the shoulders, spine, hips

and pelvis, since these examinations may be associated with a higher radi-

ation related risk.



doi:10.1016/j.spinee.2008.06.266

P25. Comparison Between Multi-level Oblique Corpectomy with or

without Image-guided Navigation for Multi-segmental Cervical

Spondylotic Myelopathy

Ho-Yeon Lee, MD, PhD, Sang-Ho Lee, MD, PhD, Hyeong-Kweon Son,

MD, June Ho Lee, MD, Oon Ki Baek, MD, PhD, Tae Joon Ahn, MD, Chan

Shik Shim, MD, PhD; Wooridul Spine Hospital, Seoul, South Korea

BACKGROUND CONTEXT: MOC is a technique in treatment of multi-

segmental cervical spondylotic myelopathy including extensive ossified

posterior longitudinal ligament. But oblique angle is not familiar with

surgeons and no anatomic landmark is present on posterior portion of ver-

tebral body. To overcome these difficulties, authors used intra-operative

C-arm-based IGN (ION, Medtronic Sofamor Danek, Memphis, TN).

PURPOSE: To evaluate the efficacy of image-guided navigation (IGN) in

multilevel oblique corpectomy (MOC).

STUDY DESIGN/ SETTING: A retrospective review of cases.

PATIENT SAMPLE: Since the application of IGN on MOC, 22 patients

have had post-operative MR images; among them, eleven patients under-

went MOC with IGN.

OUTCOME MEASURES: Clinical outcomes were measured preopera-

tively and on the 5th day after operation by the scoring system of Japanese

Orthopaedic Association (JOA) with several perioperative parameters. The

completeness of MOC was measured at the most compressive level; sum

of bilateral remaining posterior body minus remaining approach side an-

terior body in millimeter. Result was considered better when the value is

smaller.

METHODS: In eleven IGN group, total 39 levels were operated. IGN was

applied after exposure of cervical spine. Drilling and IGN probe checking

were repeated during bony dissection to confirm the depth and angle.

RESULTS: Mean completeness of MOC was 0.89mm in navigation

group, 5.9mm in control group. Mean change of JOA score is 4.27 and

2.91 respectively. In control group, two patients underwent re-exploration

due to remaining OPLL. Even extra time was spent to set up the naviga-

tion, mean operative time was shorter in the study group (248min vs.

259min). Treated levels were 3.55 and 3.36 respectively.

CONCLUSIONS: With image-guided navigation, authors could achieve

faster and more complete MOC.



doi:10.1016/j.spinee.2008.06.267

P26. Comparison of Range of Motion Following Cervical Spine

Decompression Surgical Procedures and the Effect on Patient

Satisfaction

Kevin Bell, MS1, Charise Shively, BS2, Erik Frazier, MS2,

Robert Hartman3, Joon Y. Lee, MD2, James Kang, MD2,

William Donaldson, III, MD2; 1Pittsburgh, PA, USA; 2University of

Pittsburgh, Pittsburgh, PA, USA; 3Pittsburgh, PA, USA

BACKGROUND CONTEXT: Operative treatment options for cervical

decompression include anterior and/or posterior procedures aimed at ex-

pansion of the spinal canal. Direct comparison of the postoperative success

of these treatments using cervical range of motion (CROM) and the Neck

Disability Index (NDI) will provide objective data adding to the clinical

knowledge base.

PURPOSE: The purpose of this research study is to compare CROM and

NDI scores for the decompressive surgical treatments to an age-matched,

114S Proceedings of the NASS 23rd Annual Meeting / The Spine Journal 8 (2008) 1S–191S

healthy cohort and to elucidate differences in CROM between procedures

as a function of postoperative time and number of fused levels.

STUDY DESIGN/ SETTING: Case-controlled prospective clinical study

with age-matched cohort.

PATIENT SAMPLE: N569 subjects (ages 40–65), n512 baseline subjects

and n557 surgical subjects: anterior cervical decompression and fusion

(ACDF, n529), posterior laminectomy and fusion (PLF, n511), combined

anterior and posterior decompression and fusion (A&P, n512), and uninstru-

mented laminoplasty (LP, n55).

OUTCOME MEASURES: Cervical Range of Motion (CROM) measure-

ments and the Neck Disability Index (NDI) survey were recorded.

METHODS: The Nest of Birds electromagnetic tracking (Ascension

Technology), controlled by VR goggles (i-O Display Systems), was used

to record 6-DOF CROM. The subjects executed five consecutive cycles

of flexion/extension (FE), axial rotation (AR), lateral bending (LB), and

circumduction. A Student’s t-test (p5.05) was used for statistical analysis.

RESULTS: Four-level surgical subject (ACDF, PLF, A&P, and LP) mea-

surements (Fig A) showed a trend of decreased primary CROM compared

to baseline; however, at all levels, ACDF and LP procedures preserved

CROM at 6–12 months (Fig B). In both data sets (number of levels and

time course), primary CROM for PLF and A&P patients was significantly

decreased. Additionally, A&P patients reported the highest NDI scores

(moderate to severe disability) postoperatively.

Figure

CONCLUSIONS: The results indicate that ACDF and LP preserve motion

(compared to PLF or A&P) with the majority reporting low neck disability

in the NDI–whereby providing additional justification for implementation

of these procedures when clinically applicable. However, insights into the

long-term outcomes of these procedures and their effects on adjacent level

kinematics cannot be addressed because only global motions were re-

corded at relatively short postoperative follow-up.



doi:10.1016/j.spinee.2008.06.269

P27. Comparison of Cage Designs for Transforaminal Lumbar

Woojin Cho, MD, PhD1, Chunhui Wu, PhD2, Amir Mehbod, MD2,

Ensor Transfeldt, MD2; 1Twin Cities Spine Center, Chesterfield, MO, USA;2Twin Cities Spine Center, Minneapolis, MN, USA

BACKGROUND CONTEXT: Prior biomechanical studies of transfora-

minal lumbar interbody fusion were primarily focused on various posterior

instrumentation options, comparison with other fusion techniques, and

cage positioning inside disc space. Few studies investigated the biome-

chanics of various cage designs, especially the ones that are used widely

today.

PURPOSE: The objective of this study is to compare three popular cage

designs in terms of construct stability, and potential cage migration and

subsidence after cyclic loading.

STUDY DESIGN/ SETTING: Biomechanical Comparative Study

PATIENT SAMPLE: Twelve lumbar motion segments were used in this

study.

OUTCOME MEASURES: one way ANOVA and Mann-Whitney nopara-

metric test.

METHODS: The experimental procedure was performed in two steps:

multidirectional flexibility test and cyclic test. In the multidirectional flex-

ibility test, all twelve specimens were tested following intact and five dif-

ferent cages: (Medtronic Capstone, Stryker AVS TL and PL in various

lengths). The straight cages have biconvex (Capstone) or flat inferior

and superior surfaces (AVS PL) and are typically placed in an oblique an-

gle. The AVS TL cage has a banana shape and is often placed in the an-

terior portion of the disc space. In the cyclic test, the twelve specimens

were randomly divided into two groups for Capstone and AVS TL cages.

Three thousand cycles in axial torsion, lateral bending and flexion exten-

sion were applied sequentially and cage migration was measured using x-

rays.

RESULTS: On average, the cage and posterior fixation reduced the range

of motion of the intact condition by 40%, 69% and 75% in axial torsion,

lateral bending and flexion extension respectively. There was no statistical

difference in construct stability among all five cages. The cage migration

(biconvex versus flat) under cyclic loading was less than 0.2mm and no

statistical difference was found. No cage subsidence was observed after

dissection.

CONCLUSIONS: The experimental results suggest that the geometry of

cages, including shape (banana or straight), length, and surface profile (bi-

convex or flat), does not affect construct stability when the cages are used

in conjunction with posterior fixation. With posterior fixation and surface

serration, cage migration and subsidence was minimal under cyclic loading

for both biconvex and flat cages.



doi:10.1016/j.spinee.2008.06.270

P28. Pedicle Screw Trajectory is Improved with Tapping in Thoracic

Spines

Serkan Erkan, MD1, Brian Hsu, MD2, Chunhui Wu, PhD3, Amir Mehbod,

MD3, John Perl, II, MD4, Ensor Transfeldt, MD3; 1Minneapolis, MN, USA;2Sydney, Australian Capital Territory, Australia; 3Twin Cities Spine Center,

Minneapolis, MN, USA; 4Abbott Northwestern Hospital, Minneapolis, MN,

USA

BACKGROUND CONTEXT: Pedicle screws are placed with the guid-

ance of pilot holes. The correct trajectory of pilot holes is verified by visual

inspection, palpation with a pedicle probe, or radiographs. However, a pilot

hole alone does not insure the screw will follow the pilot hole trajectory.

No studies have characterized the risk of misalignment of a pedicle screw

with respect to its pilot hole trajectory.

PURPOSE: The objective of this study is to quantify the misalignment be-

tween pedicle screws and pilot holes with or without tapping.

p26. comparison of range of motion following cervical spine decompression surgical procedures and...

Documents