Page 139 - Demo

Patient Specific Instrumentation in ACL reconstruction1377Using this technique, a point on the lateral side of the lateral femoral condyle was selected and marked by a circle of 2 mm in diameter. This point was referred to as the “entry point.” The entry point, ACL origin point, and the segmented femur were exported as Standard Tessellation Language (STL) models.Development of a patient specific guide. The STL models were processed by an orthopedic engineer to create a patient specific drill guide. A negative mold of the lateral wall of the intercondylar notch was created: a box was fitted in the intercondylar notch and a Boolean operation was performed, subtracting the femoral model from the box. The drill guide was designed as an adaptation to the outside-in GraftLink® technique by Arthrex using the FlipCutter® (Arthrex Inc., Naples, FL, US) as described by Lubowitz.15 The original femoral aiming guide on the Arthrex instrument was replaced by a 3D printed guide that fits the intercondylar notch, see Figure 3. The position of the femoral guide in combination with the 3D printed guide was designed to create a drill trajectory between the ‘entry point’ and ‘ACL origin point,’ within “Kang’s cone” see fig 3. The patient specific guides were printed using a Selective Laser Sintering (SLS) printer with polyamide 12 powder (ISO 13485 certified). Polyamide 12 has an elasticity of 1650 MPa, a tensile strength of 48 MPa and was printed with a layer thickness of 0.1-0.12 mm. The material is suitable for routine steam heat sterilization by the autoclave.Cadaver Experiment.Two male and two female cadaveric specimens were used. Average age at time of death was 88 years. Two left knees and two right knees were used. The cadavers were fixed in a custom-made leg holder. Both the femur and tibia were fixed by a clamp connected to a hinge which allowed for flexion/extension and internal/external rotation of the knee. Skin and subcutaneous tissue were dissected off. The extensor mechanism including the patella, Hoffa’s fat pad and the anterior capsule was removed. After resection of the ACL, the patient specific hooks were introduced in the notch and Mark Zee.indd 137 03-01-2024 08:56