Introduction: The anterior column of the spine is crucial for stability. In a dystrophic spine, the loss of multisegmental anterior spinal support can have devastating consequences. Since posterior instrumentation alone cannot take over the weight bearing capacity of the anterior column, structural anterior support must be created. Long bone struts are at risk for failure of engraftment and pseudoarthrosis. Patient-specific anterior support using 3D printing technology may be a better solution in these patients. Research question: Are patient-specific approaches using 3D printing technology a viable treatment option for multilevel anterior spinal support? Material and methods: Five patients received a custom-made anterior paravertebral titanium spinal strut prosthesis; one patient received a 3D shaped structural allograft. Cost assessment was made based on hours spent and production costs. Clinical outcomes were extracted from the medical records. Results: All six implantations went uneventful with adequate fit of the prostheses and allograft. The mean surgery time was 219 min, and mean blood loss was 850 ml. No implant subsidence or loosening occurred during follow-up (0.5–8 years). Complications observed were partial bronchial compression in one patient and a postoperative infection in another. The first cases were most costly due to the hours spent on design and regulatory compliance. These costs declined for subsequent cases. Discussion and conclusion: Custom-made prostheses appear to be a viable treatment option for multi-level anterior spinal support. No implant failure was observed up to 8 years postoperative. Close collaboration between an in-house 3D lab and the surgical team was essential for implementing custom-made prosthesis in clinical care.

The unprecedented properties of meta-biomaterials could pave the way for the development of life-lasting orthopedic implants. Here, we used non-auxetic meta-biomaterials to address the shortcomings of the current treatment options in acetabular revision surgery. Due to the severe bone deficiencies and poor bone quality, it can be very challenging to acquire adequate initial implant stability and long-term fixation. More advanced treatments, such as patient-specific implants, do guarantee the initial stability, but are formidably expensive and may eventually fail due to stress shielding. We, therefore, developed meta-implants furnished with a deformable porous outer layer. Upon implantation, this layer plastically deforms into the defects, thereby improving the initial stability and homogeneously stimulating the surrounding bone. We first studied the space-filling behavior of additively manufactured pure titanium lattices, based on six different unit cells, in a compression test complemented with full-field strain measurements. The diamond, body-centered cubic, and rhombic dodecahedron unit cells were eventually selected for the design of the deformable porous outer layer. Each design came in three different relative density profiles, namely maximum (MAX), functionally graded (FG), and minimum (MIN). After their compression in bone-mimicking molds with simulated acetabular defects, the space-filling behavior of the implants was evaluated using load-displacement curves, micro-CT images, and 3D reconstructions. The meta-implants with an FG diamond infill exhibited the most promising space-filling behavior. However, the required push-in forces exceed the impact forces currently applied in surgery. Future research should, therefore, focus on design optimization, to improve the space-filling behavior and to facilitate the implantation process for orthopedic surgeons. Statement of significance: Ideally, orthopedic implants would last for the entire lifetime of the patient. Unfortunately, they rarely do. Critically sized defects are a common sight in the revision of acetabular cups, and rather difficult to treat. The permanent deformation of lattice structures can be used to create shape-morphing implants that would fill up the defect site, and thereby restore the physiological loading conditions. Bending-dominated structures were incorporated in the porous outer layer of the space-filling meta-implants for their considerable lateral expansion in response to axial compression. A functionally graded density offered structural integrity at the joint while enhancing the deformability at the bone-implant interface. With the use of a more ductile metal, CP-Ti, these meta-implants could be deformed without strut failure.