University of Twente Student Theses


Development of a personalized allograft bone tissue implant for treatment of pediatric hip dysplasia patients

Nijendijk, Bob (2020) Development of a personalized allograft bone tissue implant for treatment of pediatric hip dysplasia patients.

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Abstract:Introduction: Developmental dysplasia of the hip is a deformity of the socket of the hip joint, which can lead to early osteoarthritis and dislocation and deformation of the femoral head. The shelf acetabuloplasty is a surgical procedure in which a strip of bone is inserted in the hemipelvis, just above the joint capsule, to increase coverage of the femoral head. The bone strip has to be cut to size during surgery, sometimes resulting in femoroacetabular impingement or insufficient increase in coverage. A personalized implant, designed and produces pre-operatively, may reduce these risks. However, commonly used materials for implants such as titanium are not suitable for pediatric patients, since they do not grow with the patient. Instead, a suitable solution is a personalized bone tissue implant, manufactured through rapid prototyping. Method: A design study was set up, in which the demands that a personalized hip implant must meet were investigated through literature and experts. A prototype study was performed, in which a workflow to manufacture a personalized bone tissue implant was developed and investigated. Using CT images implants were designed which could then be manufactured from a 3D printed model, dried bone and fresh frozen bone tissue through CNC-milling. Bone density and geometry comparisons were performed to validate the shape of the implants. A shelf acetabuloplasty was performed on a cadaver with the fresh frozen implant. Results: The best suited source material for the implant is a hemipelvis, with an acetabulum with a larger diameter than the hemipelvis of the patient. The acetabular rim can be used as body of the implant and made to fit the patient anatomy. A block on the implant ensures correct positioning of the implant in the patient. Using a mold for the donor hemipelvis, the implant can be obtained by milling from a single side. Three prototypes were milled successfully, with only the dried bone fracturing partially during milling. Mean surface distance between design and prototype was below a millimeter. The fresh frozen prototype was successfully implanted on the cadaveric hip, increasing coverage and fitting the hemipelvis and joint capsule, despite positioning not being fully correct. Conclusion: A personalized implant can be manufactured from bone tissue using CNC-milling using the proposed workflow and the first clinical application of an allograft acetabular extension implant may take place in the coming year.
Item Type:Essay (Master)
Faculty:TNW: Science and Technology
Subject:44 medicine
Programme:Technical Medicine MSc (60033)
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