Biomechanical evaluation of a novel tri-blade titanium implantable vertebral augmentation device

Abstract

Background context: Titanium implantable vertebral augmentation device (TIVAD) are regarded as having potential in the treatment of vertebral compression fractures (VCFs). However, improper design in current TIVADs results in the inability to effectively restore VCF height and maintain stability. There is still an unmet clinical need for improvement.

Purpose: The authors tested a newly developed a TIVAD (Tri-blade fixed system) that can provide enough endplate collapse support to restore the vertebral body height in a safe retraction mechanism for VCFs using minimally invasive surgery (MIS).

Study design: The performed biomechanical tests included blade expansion force, lifetime of cement embedded and vertebral height restoration efficiency of porcine osteoporosis VCFs for its feasibility.

Methods: A cylinder with 3 surface cuts that form blades that can be expanded into a conical space was designed (Tri-blade fixed system). The 3 blades can be expanded outward with angles between blades as 105°/ 105°/150° for lower left/lower right/upper arms, respectively that reach 15mm in height and 14.8 mm in width. A frame was specifically designed to measure the contact force using force sensing resistors during blade expansion. The Tri-blade fixed system was embedded into a cement block to perform fatigue testing under 2000N pressure (5*10⁶ cycles) for understanding the device lifetime limitation. The Tri-blade system was then inserted into porcine osteoporosis VCFs to examine the vertebral height restoration efficiency.

Results: The average maximum contact force for the top, bottom left and right blades were 299.0N, 283.5N and 279.3N, respectively with uniformly outward expansion forces. The fatigue test found that there were no obvious cracks or damage to the cement block. The porcine osteoporosis vertebral body at the anterior, middle, and posterior heights can be restored to 21.9%, 12.6% and 6.4%, respectively.

Conclusions: This study developed a novel TIVAD with conical shape that can provide a more stable structure with sufficient/uniform expansion force, passing the fatigue test with bone cement and high effective in vertebral height restoration tests for porcine osteoporosis VCFs.

Clinical significance: The new 3D Tri-blade TIVAD may offer a new treatment option for VCFs.

Keywords: Biomechanics; Cement; Fatigue; Finite element; TIVAD, Vertebral compression fractures.