CAD design | Acta Medica Marisiensis

Introduction: Developing new surgical procedures and prototyping implants requires a real or adequate virtual testing environment to work in. Due to the unique architecture of the human foot interventions and implants can be tested only on patients and cadavers. We present our own approach for creating the geometrical model based on 3D CT reconstruction.
Material and methods: For the model construction we used the CT data from the foot of a healthy, young patient. The input data consisted from 56 sections from the talar dome to the plantar surface. The slices were segmented, boundary detection was performed, the boundaries were smoothed, NURBS interpolation was performed to obtain 3D surface. The surfaces were closed to solids and the solids edited to obtain the virtual anatomical structures.
Results: Our model is geometrically accurate in the limits of resolution that were given by the CT examination.
Conclusions: Now that we have an available model construction method we can begin enclosing the geometrical model into mathematical environments for finite element analysis. Also, scanning and reconstructing multiple feet with different conditions will help us to understand illnesses and develop new operative techniques and implants.

Background: Infection is the most feared complication in every aspect of bone surgery. Antibiotic impregnated cement spacers and cement beads are widely used since 1972 for treating prosthetic infection. The delivery of a high concentration of antibiotics in a localized area is thought to be safer than systemic administration of intravenous antibiotics in such doses.
Materials and methods: Our clinic has more than 10 years of experience in using preformed and manufactured spacers, mostly hand made. A new method developed by us puts the designing in the preoperative planning phase. Antibiotics are chosen based on the antibiogramm the cement is chemically “configured”. 3D design based on the previous implant or on the bony structure is done; negative molds are manufactured with CNC mill the manufacturing kit is sterilized with ethylene oxide. Intraoperatively the spacer is molded and implanted.
Results and Conclusions: We consider that our method meets almost all the conditions proposed by us. Problems were found with the inconsistent mechanical behavior. More studies are required regarding the mechanical properties of the bone cement in function of antibiotic concentrations and preparation methods.