Biomechanical testing and clinical experience with the OMEGA-21 spinal fixation system

The role of spinal instrumentation is to provide mechanical stability, obtain and maintain anatomic alignment, and promote fusion. The American Society for Testing and Materials (ASTM) introduced guidelines and procedures so that biomechanical properties of different implant designs could be compared in a consistent manner. Combined with biomechanical analyses, clinical evaluation allows the safety and efficacy of a spinal implant system to be determined before construction. The objective of our study was to determine the biomechanical properties and clinical performance of the OMEGA-21 Spinal Fixation System. Static and dynamic (fatigue) biomechanical testing was performed per ASTM guidelines and recommendations on individual components and on the system assembled in a corpectomy model. Clinical and radiographic evaluation of 57 consecutive patients with indications for instrumented spinal arthrodesis of the lower dorsal lumbar and sacral segments of the spine was performed at a mean follow-up of 31.9 months. Static and fatigue testing revealed superior biomechanical properties of the individual components and of the assembled system. The mechanical-strength values of the system were comparable with maximum reported values for existing implant designs. At final clinical follow-up, 86% of patients obtained relief of their symptoms; 84% considered their clinical results to be excellent or good. Ninety-one percent of patients satisfied radiographic criteria for bony fusion. There were 5 implant-related complications: 2 misplaced screws (2 patients), local pain above the implant (2 patients), and 2 broken expansive screws (1 patient). Biomechanical and clinical results indicate that the OMEGA-21 system is feasible and performs well as a spinal instrumentation system for the lower dorsal, lumbar, and sacral spine.