O -arm in spine surgery

O-arm in spine surgery

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

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

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

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

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

Multi planar imaging Axial, sagittal and coronal imagesMultiple level imaging without moving the

machine in a single sequenceImaging of the cervico dorsal junction and

upper thoracic spine

Imaging for cervico dorsal junction

Imaging for cervico dorsal junction

sag

coronal

axial

D7 potts spine – percutaneous fixation

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 boundaries3.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

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

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

Intra op 3D imaging after pedicle screw placement using O armThe 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

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

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

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).

Radiation exposureeffective 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.

Effective dose of radiation

Krause et al 2010..

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

Dis advantagesTechnical difficulties: Problems with registrationPreoperative 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

Dis advantagesSteep 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

Increased operative timeHärtl 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

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 accuracyComplex OR set up

OR set up with O Arm

Our experienceTotal number of pedicle screws placed under O

arm guidance were 112 in 20 patients.Cervical-1 patientsDorsal -6 ptsLumbar-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.

Percutaneous fixation o D6 fracture

Failedback syndrome- underwent minimally invasive percutaneous pedical screw fixation

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.