Precision in spinal screw placement is important but misplacement rates using conventional techniques range from 5-41%. 3D fluoroscopic navigation systems like the O-Arm provide multi-planar imaging, decreased radiation exposure, and improved accuracy over 2D systems. Studies show pedicle screw misplacement rates decrease from 68.1% with conventional fluoroscopy to 84.3% with 2D navigation and 95.5% with 3D navigation. The O-Arm allows for immediate correction of malplaced screws.

2. Introduction
 Precision in pedicle screw placement is of utmost
importance in any spinal fixation procedure
 However, misplacement rates have been reported to
range from 5% to 41% in the lumbar spine and from 3%
to 55% in the thoracic spine when using conventional
techniques
 Esses SI, Sachs BL, Dreyzin V: Complications associated with the
technique of pedicle screw fixation. A selected survey of ABS
members. Spine (Phila Pa 1976) 18:2231–2239, 1993

3. O Arm ......
 2D imaging systems use AP and lateral images
incorporated with pre op CT- less accurate
 3D navigation- of cone-beam CT enabled multiple
fluoroscopic image acquisition by a device that rotated
isocentrically around the patient- more accurate

4.  Reconstructed images from is transferred to an image-
guided system for navigartion.
 As the reference arc is tracked with the patient
imaging, the computer-generated 3D image of the
patient’s operative field is already registered and ready
for use with navigation

5. Advantages of 3D Navigation
system-O Arm
 ability to image multi planar images , multiple levels in a
single sequence
 Efficacy in imaging of the cervico dorsal junction and
upper thoracic spine than conventional flouroscopy
 decreased radiation exposure to the operating room (OR)
staff
 improved accuracy because the patient’s anatomy is
registered in the surgical position
 imaging accuracy in patients who had undergone prior
spine surgeries at the same levels,
 portability of the system

6.  Intra operative 3D imaging-helps in correction of
malplacement of screws and avoidance of second
suregery
 allow the application of minimally invasive approaches
without elevating the risk of implant misplacements,
and can thus help to decrease skeletomuscular surgical
trauma and ultimately the length of the hospital stay
of patients

7. Multi planar imaging
 Axial, sagittal and coronal images
 Multiple level imaging without moving the machine in
a single sequence
 Imaging of the cervico dorsal junction and upper
thoracic spine

8. Imaging for cervico dorsal
junction

9. Imaging for cervico dorsal junction
sag
coronal
axial

10. D7 potts spine – percutaneous
fixation

11. Classification of screw malpositions
in lumbar spine- Learch and
Wiesner
 1.Encroachment If the pedicle cortex could not be
visualised.
 2. Minor penetration When the screw trajectory was
<3 mm outside the pedicular boundaries
 3.Moderate penetration When the screw trajectory was
3–6 mm outside the pedicular boundaries.
 4. Severe penetration When the screw trajectory was
>6 mm outside the pedicular boundaries.
Learch TJ, Massie JB, Pathria MN, Ahlgren BA, Garfin SR
(2004) Assessment of pedicle screw placement utilizing conventional
radiography and computed tomography: a proposed systematic approach to
improve accuracy of interpretation. Spine 29:767–773

12. 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 • M.
Gutberlet
Eur Spine J (2011) 20:875–881 DOI 10.1007/s00586-010-1683-4

13.  Free-hand technique will only be safe and accurate
when it is in the hands of an experienced surgeon.
 The accuracy of screw placement with O-arm can
reach 100%. The learning curve of O-arm is high when
compared to the free-hand technique which has a
steep learning curve

14. Intra op 3D imaging after pedicle
screw placement using O arm
 The intraoperative evaluations of the 3D scan resulted
for 12.5–14.3% of the patients to the continuation and
correction of the surgical measure and to the
avoidance of a secondary revision
 Immediate correction of malplaced screws lowers the
secondary revision rate of the patients and prevents
patients ahead secondary neurovascular problems and
instability or dislocation of the fixateur
 Benefit and accuracy of intraoperative 3D-imaging after pedicle screw placement: a
prospective study in stabilizing thoracolumbar fractures
 Markus Beck Æ Thomas Mittlmeier
 Eur Spine J (2009) 18:1469–1477 DOI 10.1007/s00586-009-1050-5

15.  Though few studies show, no differences between 2D
and 3D fluoroscopic navigation methods in the rate of
pedicle screw misplacement.
 Lee GY, Massicotte EM, Rampersaud YR: Clinical accuracy of cervicothoracic pedicle screw
placement: a comparison of the “open” lamino-foraminotomy and computer-assisted techniques. J
Spinal Disord Tech 20:25–32, 2007
 Lekovic GP, Potts EA, Karahalios DG, Hall G: A comparison of two techniques in image-guided
thoracic pedicle screwnplacement: a retrospective study of 37 patients and 277 pedicle screws. J
Neurosurg Spine 7:393–398, 2007

16. a meta analysis show..
 Using standard insertion techniques,the rate of
misplaced pedicle screws ranges from 14% to 55%, with
as many as 7% of these misplaced screws resulting in
neurological injuries
 Laine T, Lund T, Ylikoski M, Lohikoski J, Schlenzka D: Accuracy of pedicle screw
insertion with and without computer assistance: a randomised controlled clinical study
in 100 consecutive patients. Eur Spine J 9:235–240, 2000

17.  Conventional fluoroscopy, a total of 2532 of 3719 screws
were inserted accurately (68.1% accurate).
 Using 2D fluoroscopic navigation, 1031 of 1223 screws were
inserted accurately (84.3% accurate).
 With 3D fluoroscopic navigation, 4170 of 4368 screws were
inserted accurately (95.5% accurate).

18. Radiation exposure
 effective dose for conventional operations with doses
ranging from 1.5 mSv to 6.9 mSv
 Jones DP, Robertson PA, Lunt B, Jackson SA. Radiation exposure during
fluoroscopically assisted pedicle screw insertion in the lumbar spine.
Spine (Phila Pa 1976) 2000;25:1538–1541.

19. Effective dose of radiation

20. Krause et al 2010..

21.  Perisinakis et al. evaluated the radiogenic risks for
cancer induction after pedicle screw fixation and
found an induction rate of 110 per million.
 3-D navigation can reduce radiogenic risks ---the
preferred approach
 Perisinakis K, Theocharopoulos N, Damilakis J, Katonis P, Papadokostakis G,
Hadjipavlou A, Gourtsoyiannis N. Estimation of patient dose and associated
radiogenic risks from fluoroscopically guided pedicle screw insertion. Spine (Phila
Pa 1976). 2004;29:1555–1560

22. Dis advantages
 Technical difficulties:
 Problems with registration
 Preoperative patient factors -obese and morbidly
obese patients create difficulty with positioning, beam
penetration, and the ability to maneuver imaging
devices around the patients.
 This results in poorer quality images that can make the
registration process inaccurate, as well making the
images difficult to use during surgery.
 Vaidya R, Carp J, Bartol S, Ouellette N, Lee S, Sethi A: Lumbar spine fusion in obese and
morbidly obese patients. Spine (Phila Pa 1976) 34:495–500, 2009

23. Dis advantages
 Steep learning curve
The components of the learning curve
include the ability to direct instruments based on
imaging visualized on a screen, the ability to replicate
in-line maneuvers while placing instrumentation, as
well as adopting and developing proper technique
while using image-guided technology
Complex registration system

24. Increased operative time
Härtl R, Lham K, Wang J, Korge A, Kandziora F: The AOSpine ANEG (Access
and Navigation Expert Group) survey on the use of navigation in spine surgery.
Presented at the Global Spine Congress 2011, Barcelona, Spain, March 23–26,
2011
One study, an RCT, revealed no
difference in total operative time
 Laine T, Lund T, Ylikoski M, Lohikoski J, Schlenzka D: Accuracy of pedicle screw
insertion with and without computer assistance: a randomised controlled clinical study
in 100 consecutive patients. Eur Spine J 9:235–240, 2000

25.  Sterile draping- cumbersome with O arm, at times
getting caught between the shields
 Wrong level surgery-in minimally invasive surgery
without proper anatomical identification
 Maintanence of navigation accuracy
 Complex OR set up

26. OR set up
with O Arm

27. Our experience
 Total number of pedicle screws placed under O arm
guidance were 112 in 20 patients.
 Cervical-1 patients
 Dorsal -6 pts
 Lumbar-13pts
 The average time for surgery 4.6 hours(3-6.4 hrs)
 The mean duration of hospital stay was 4 days.
 None of the patient had breech or screw displacement
because of the precision of intra operative O arm image
guidance.
 All patients had excellent post operative outcome.

28. Percutaneous fixation o D6 fracture

29. Failedback syndrome-
underwent minimally
invasive percutaneous
pedical screw fixation

30. Conclusion
 The system is considered as excellent for ease of use
from our experience. Accurate screw placement
provides better patient safety and reduces incidence of
screw removal and the hospital stay there by early
mobilization and may reduce the cost incurred on the
patient management.