Information Technology Reference
In-Depth Information
once a decision is made with respect to the size and trajectory of a speci
c implant,
the Fastening Strength provides minimal information, as it is a relative measure
based on which the implant trajectory and size is optimized and its absolute mag-
nitude is meaningless unless compared against other values computed for the same
implant.
Based on the output report, the instrumentation inventory is prepared for the
upcoming procedure. Also, the virtual plan can be saved as either a surface or
volume rendered model either including or excluding the virtual screws that can be
displayed in the procedure room for analysis and review during the intervention. If
a life-size model of the instrumented spine is required by the surgeon prior to the
procedure, the virtual plan is saved as a stereo-lithography (STL)
file and a physical
model can be generated using a 3D printer or a rapid prototyping device.
In the event that a surgical navigation platform is employed to guide the inter-
vention, the virtual plan can be registered to the patient
'
s anatomy in the OR by
using a variety of registration techniques
the most suitable and straight-forward
being a landmark-based rigid body registration for each individual vertebral seg-
ment. This approach will minimize any uncertainties introduced by registering an
entire region of the spine to the patient, provided a slightly different position or
orientation of the patient between the pre-operative scan and intra-operative pro-
cedure. After registration, the drilling tool and pedicle implant can be guided and
inserted according to the prescribed pre-operative plan.
—
4 Platform Evaluation and Validation
4.1 Assessment of 3D Templating Tool
A small retrospective pilot study was conducted to compare the traditional 2D
method of spine surgery planning and the 3D templating method for pedicle screw
placement. A cohort of 10 subjects was identi
ed for the study, each having had a
previous spinal procedure that included the implantation of pedicle screws in two or
more vertebrae. Original preoperative plans were not available so two new plans
were created for each subject based on the CT exams taken prior to the surgery. One
was a plan based on the same type of 2D method used to carry out the original
procedure. A second plan was created using the new 3D templating tools. Each of
two participating surgeons generated separate plans for 5 of the 10 subjects. One
participant was a skilled staff surgeon with 14 years of experience and the other was
a
fifth year resident. Post-surgical CT exams were also extracted from the patient
record to compare both methods of planning with the post-surgical results. Metrics
used in the evaluation included pedicle screw lengths, widths and angles. The pre-
operative 2D planning data, pre-operative 3D planning, and post-operative images
were analyzed by looking at:
