R_Bibb_Medical_Modelling_The_Application_of_Adv.pdf
R_Bibb_Medical_Modelling_The_Application_of_Adv.pdf
R_Bibb_Medical_Modelling_The_Application_of_Adv.pdf
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
6.4.3 Materials and methods<br />
Case studies 137<br />
<strong>The</strong> patient was a 60 year old lady with a long history <strong>of</strong> rheumatoid arthritis<br />
which fi rst presented at the age <strong>of</strong> 15 with deformity <strong>of</strong> the fi ngers. She<br />
had a Benjamin’s double osteotomy (see medical explanatory note 8.2.4)<br />
<strong>of</strong> the left knee at 27 because <strong>of</strong> the potential for subluxation (dislocation<br />
<strong>of</strong> the knee cap), and a synovectomy (surgery to remove infl amed joint<br />
tissue) <strong>of</strong> the right knee at 35. <strong>The</strong> left knee progressively became more<br />
varus (abnormally positioned towards the midline) and unstable and she<br />
had presented at the age <strong>of</strong> 59, wheelchair bound with a grossly unstable<br />
and deformed left knee. She was considered for total knee replacement<br />
and, due to the gross deformity <strong>of</strong> the joint, a CT scan was carried out. <strong>The</strong><br />
scan was carried out in the horizontal plane with her tibial axis aligned at<br />
right angles to the scanning plane on the machine’s couch with s<strong>of</strong>t fi rm<br />
padding (the tibia is the shin bone). Slices in the horizontal plane at 1.5 mm<br />
intervals were taken to 30 mm below the joint line, producing 20 sections.<br />
<strong>The</strong> data was stored onto a magnetic/optical disc in DICOM format for<br />
processing and converting into the appropriate fi le system to produce a 3D<br />
model in the computer and consequently a solid model to scale. <strong>The</strong> whole<br />
process to generate the solid model is shown in Fig. 6.21.<br />
<strong>The</strong> model <strong>of</strong> the knee was created using stereolithography apparatus<br />
(SLA ® – 3D Systems Inc., 26081 Avenue Mall, Valencia, CA 91355, USA).<br />
Patient’s knee aligned on the CT table with tibial axis in<br />
plane <strong>of</strong> the table axis<br />
CT <strong>of</strong> the knee and data stored on an<br />
optical disc in DICOM format<br />
Data converted to SLA data<br />
Shape reconstructed in the computer<br />
3D solid model produced <strong>of</strong> the proximal tibia to the<br />
level <strong>of</strong> the intended ‘cut’ constructed by rapid prototyping<br />
methods<br />
Surgeon examines reconstructed model to ascertain<br />
quality and geometry <strong>of</strong> the cortical bone shape to<br />
determine level <strong>of</strong> cut for optimal prosthesis support<br />
6.21 Work fl ow.
Change language