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Introduction
Accurate position of bone cuts and final
alignment is a key factor for the success of total
knee arthroplasty (TKA). As a seducing
alternative to standard procedure and
navigation, Patient Specific Instrumentation
has been introduced recently as a means of
making accurate bone cuts through custom
cutting blocks constructed based on pre-
operative 3D imaging.
Even if there may be potential causes of error
such as the acquisition of the 3D image, the
interpretation of the 3D image by the surgeon
or the application of the jigs to the bone, there
remains a lack of information regarding the
accuracy of patient specific cutting blocks.
Therefore, the purpose of this investigation
was to evaluate the accuracy and between-
patient reliability of bone cuts and the resultant
alignment produced by one type of Patient
Specific Instrumentation (the Smith and
Nephew VISIONAIRE patient-specific cutting
block system). Our hypothesis was that the
bone cuts induced by the cutting blocks were
accurate to within ±3° or ±2mm of the pre-
operative plan in each plane.
Materialand Methods
The patient specific cutting blocks (PSCB)
used in the study were performed with the
VISIONAIRE system from Smith and Nephew.
A preoperative MRI and a long leg X-ray of the
involved lower limb were performed and the
data sent to Smith and Nephew. The images
were then processed and 3-dimensional models
of the tibia and femur digitally constructed.
The bone models and digital templates of the
prosthesis were uploaded onto a proprietary
software planner. Following surgeon approval
of the surgical template and alignment of
components in multiple planes, rapid-
prototyping computer-assisted design and
computer-assisted manufacturing technology
were used to create the PSCB jigs. TKA was
undertaken according to the surgeon’s standard
technique.
The operated limb was prepared and isolation
drapes applied. Intraoperative alignment data
were collected using the Stryker Precision
navigation system (Stryker Corporation,
Kalamazoo, Michigan) as previously described
[1]. This system allowed for the assessment of
cutting block positioning before the bone cuts.
Accuracy of PSI: control
with navigation
S. Lustig, C. Scholes, S. Oussedik,
M. Coolican, D. Parker