Information Technology Reference
In-Depth Information
1 Introduction
Spinal fusion is a commonly performed procedure for a variety of conditions.
Pedicle screw
fixation for correction of spinal deformity has become the standard of
care for stabilization of the thoracic and lumbar spine. The objective of the pedicle
screw implantation procedure is to install an internal
fixator for stabilization of
injured vertebrae [ 1 ]. Precise screw placement is essential to avoid injury to adja-
cent neural structures. Patients with severe deformity or prior surgery present a
challenge to the accurate placement of pedicle screws. Additionally, minimally
invasive and percutaneous surgical techniques also present a greater challenge to
accurate screw placement and require heavier reliance on intra-operative
uoro-
scopic imaging, which presents an occupational hazard for the surgeon and the
operating-room (OR) staff [ 2 ]. However the techniques currently available for
planning such interventions are sub-optimal. Until recently, such procedures have
been traditionally planned using 2D radiographs, an approach which has proved
inadequate for precise planning due to the complex 3D anatomy of the spinal
column and the close proximity of the nerve bundles, blood vessels and viscera.
The pedicles are anatomically close to the spinal nerve roots, forming the lateral
borders of the vertebral canal and the superior and inferior margins of the inter-
vertebral foramina [ 3 ]. The nerve roots pass directly caudal to the pedicles as they
course through the respective intervertebral foramen [ 4
fl
8 ]. Furthermore, both the
sensory and motor intrathecal nerve roots follow closely the medial aspect of the
pedicles and are located in the anterior-superior one third of the intervertebral
foramen [ 4 , 6 , 7 ]. In addition, anterior to the vertebral bodies lie the aorta and vena
cava, with branching of the common iliac vessels occurring in the lumbar region.
Hence, penetration of the anterior cortex of the vertebral bodies could also lead to
injury of one or more of these vessels. As such, signi
-
cant care must be taken to
avoid the risk of neural or vascular damage during intervention.
According to the Cleary et al. [ 9 ], challenges impeding the development of better
guidance include adequate intra-operative imaging, fusion of images from multiple
modalities, the visualization of oblique paths, percutaneous spine tracking,
mechanical instrument guidance, and software architectures for technology inte-
gration. Intra-operative imaging using a high-performance mobile C-arm prototype
has demonstrated a signi
cant advance in spatial resolution and soft-tissue visi-
bility, with the added bene
fluoroscopy reliance and enabling precise
visualization via up-to-date images [ 10 ]. However, procedure planning must be
conducted in the OR, using the peri-operatively acquired images, therefore adding
to the procedure time.
Considering these limitations, it is critical for the surgeon to have access to
superior images of the patient-speci
t of reducing
fl
c anatomy that display the 3D relationships
among these structures and enable intuitive, ef
cient and risk-free planning. As part
of current clinical practice, 3D imaging scans, such as computed tomography (CT)
and magnetic resonance imaging (MRI) are often ordered prior to spine correction
procedures to help plan the intervention. During the planning process, the axial
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