The incidence of osteoporotic vertebral compression fractures (VCFs) is rapidly increasing, necessitating the identification of the most appropriate treatment method. The well-established first and second generation surgical procedures are not capable of giving optimal outcomes. Moreover, my literature study has shown little to no improvements for four of the most prevailing third generation procedures. As a consequence, the med-tech company Amber Implants B.V. developed a new 3D-printed porous titanium implant that has the potential to resolve difficulties and drawbacks that were identified for all former procedures. Nonetheless, the performance of this implant has never been tested before. Thus, the aim of this study was to pre-clinically evaluate the biomechanical properties regarding the spinal deformities for this implant. For the quantification, the prevention of spinal deformities was subdivided into the anterior height restoration and the kyphotic angle correction. The pre-clinical evaluation was conducted on isolated vertebrae originating from three human cadaver specimens. First, the most abundant type of all osteoporotic VCFs, a wedge fracture, was generated on the vertebrae with 40% anterior height decrease. Thereafter, vertebral restoration was performed with the implants. Besides, vertebral restoration with the second generation surgical procedure, the Balloon Kyphoplasty procedure (BKP), was performed likewise to serve as a comparative. After vertebral restoration, half of the implant group and the total BKP group were tested in a cyclic loading test that mimicked the activity during the first week after surgical VCF repair, i.e. 10.000 cycles with loads ranging from 100N to 600N. The other half of the implant group was tested under higher loading conditions, i.e. 10.000 cycles with loads ranging from 100N to 1000N. At each test stage the spinal deformities, which were subdivided into the anterior height and the kyphotic angle, were evaluated from micro-CT (μCT) data. Eventually, the μCT scans were compared in order to quantify the implant's performance. The anterior height restoration after vertebral restoration with the implant was outstanding compared to the BKP procedure. Thereby, a statistical significance difference (p<0.05) was not only observed for the anterior height restoration, but also for the central and posterior height restorations, between the two surgical procedures. Additionally, the kyphotic angle correction of the implant procedure outperformed the outcomes observed for the BKP. Nonetheless, after cyclic loading various drawbacks for the implants were observed, resulting in substantial decreases in outcomes for the height restoration and the kyphotic angle correction. Regarding the height decrease, most was found in the trabecular bone inferior to the implant. Presumably, the plastic deformation was induced by high local stresses as a result of the minimal contact area between the implant and the trabecular bone. Complementary, the rotation of the implant was observed to effect the implant's performance. Ultimately, it was concluded that the implant in its current design could not compete with the BKP procedure, neither with the third generation surgical repair procedures for an osteoporotic VCF such as Vertebral Body Stenting (VBS) and SpineJack. Nevertheless, the outcomes after vertebral restoration were promising. Therefore, it was assumed that the implant has a decent chance of succeeding after implementing some adjustments on the implant's geometry and the corresponding surgical tools.

Restoration of the normal mandibular form and function is attempted with reconstructive surgery. The current standard procedure to restore continuity defects of the mandible involves free tissue transfer with an autologous bone flap. Even though the success rates are high, several critical drawbacks have been associated with this procedure, including severe donor site morbidity, long hospital stay and re­covery process, need for high surgical expertise, insufficient bone graft height, and mechanical failure of the plating system. A systematic approach for the designing and testing of patient­-specific implants used as an alternative to the free flap procedure appears to be still lacking. The goal of this thesis project was to develop a semi­automatic workflow for designing patient­ specific mandibular reconstruction implants and assess the effect of topology optimization on the biome­chanical performance of the implant using the finite element analysis (FEA) and experimental validation. Using the proposed workflow, a fully porous implant (lattice implant) and a topology optimized implant (TO implant) were designed according to the anatomy of a synthetic mandible analog subjected to lateral resection, and were additively manufactured using selective laser melting. Both implants were designed in the shape of a cage to allow for the insertion of a bone graft and the integration of dental implants. The mechanical performance of the reconstructed mandibles was predicted with computa­tional FEA and evaluated through quasi­-static and cyclic experimental testing. Digital image correlation was used to validate the finite element model through principal strain field comparison. An excellent fit between the implants and mandibles was established, indicating the capability of the workflow to develop customized implants with accurate dimensions. The results obtained with FEA were in agreement with the DIC measurements and quasi-­static testing results. No significant differences (P < 0.01) in mean stiffness, mean ultimate load, and mean ultimate displacement were found between the non-­implanted control mandibles, lattice­-implanted mandibles, and TO-­implanted mandibles during quasi-­static testing. No implant failure was observed during static nor cyclic testing at loads substantially higher than the average maximum biting force of healthy individuals, indicating the high resistance of the implant designs to mechanical failure. Yet, the lattice implant would likely be preferred over the TO implant for clinical application due to its lower weight (16.5%), higher porosity (17.4%), and shorter workflow time (633.3%). The workflow proposed in this study may offer surgeons and medical engineers the tools to sys­tematically design and evaluate patient­-specific reconstruction implants. This would result in more cost­-effective and time­-effective pre-­surgical planning and result in implant designs that can minimize morbidity and maximize aesthetic and functional outcomes.