A newly developed 3D-printed porous titanium vertebral body implant for osteoporotic vertebral compression fractures

Abstract

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.