Biomechanical Evaluation of a Novel Expandable Vertebral Augmentation System Using Human Cadaveric Vertebrae  
[PERSON]  
1 Department of Orthopedic Surgery, Spine Section, Bone and Joint Research Center, Chang Gung Memorial Hospital, Taoyuan 333, Taiwan 1  
[PERSON]  
1 Department of Orthopedic Surgery, Spine Section, Bone and Joint Research Center, Chang Gung Memorial Hospital, Taoyuan 333, Taiwan 1  
[PERSON]  
1 Department of Orthopedic Surgery, Spine Section, Bone and Joint Research Center, Chang Gung Memorial Hospital, Taoyuan 333, Taiwan 1  
[PERSON]  
2 Department of Mechanical Engineering, Chang Gung University, Taoyuan 333, Taiwan 2  
[PERSON]  
3 Department of Biomedical Engineering, Chang Gung University, Taoyuan 333, Taiwan 3  
[PERSON]  
2 Department of Mechanical Engineering, Chang Gung University, Taoyuan 333, Taiwan 2  
[PERSON]  
1 Department of Orthopedic Surgery, Spine Section, Bone and Joint Research Center, Chang Gung Memorial Hospital, Taoyuan 333, Taiwan 1  
Footnote 1: [[https://www.mdpi.com/journal/applsci](https://www.mdpi.com/journal/applsci)]([https://www.mdpi.com/journal/applsci](https://www.mdpi.com/journal/applsci))  
Footnote 2: [[https://www.mdpi.com/journals/pdf/10/03/10](https://www.mdpi.com/journals/pdf/10/03/10)]([https://www.mdpi.com/journals/pdf/10/03/10](https://www.mdpi.com/journals/pdf/10/03/10))  
When pain persists after conservative treatment for one month, surgical solutions including percutaneous vertebplasty with polymethylmethacrylate (PMMA) cement for pain relief or percutaneous kyrophoplasty for further vertebral height restoration might be considered [6; 7; 8]. There have been three theoretical concerns about potential adverse effects with the use of these procedures: (1) Uncontrolled bone cement leakage over the venous plexus and epidural space, which can result in pulmonary embolism and neurological damage [2; 9]; a cement leakage rate from percutaneous vertebplasty reaching 69.1% was reported for the epidural space, disk space, and paraspinal tissues through defects of the fractured verteb [9; 10]. Percutaneous balloon kyrophplasty was designed to reduce the cement leakage rate during augmentation. Clinical evidence has shown a reduced cement leakage rate for kyrophplasty compared with vertebplasty in osteoporoxide cases, but the resulting devastating symptomatic complications still need to be alerted [9; 10; 11; 12; 13; 14]. (2) Adverse bone union process due to thermal effect may induce inflammatory reaction and inadequate biological scaffold properties [15; 16]. Although new bone formation was observed radiographically in 40% of patients who received vertebplasty in long-term follow-up [17], histological evidence still showed a decreased quantity and quality of callus mineralization surrounding bone cement in vertebplasty groups [18; 19]. (3) Unacceptable sagittal alignment. Balloon kyrophoplasty involves the inflation of a balloon inside the collapsed fractured vertebral body, which restores its height before the fracture is stabilized with cement. However, significantly restored vertebral height loss after balloon deflation worsens the reduction achievement. To maintain the restored vertebral height and reduce the reliance on cement as the major stabilizer, an expandable titanium device, OsseoFix(r) (AlphaTec Spine Inc., Carlsbad, CA, USA), which was accompanied by a mechanical working system that allows progressive and controlled vertebral fracture reduction, was developed [20; 21]. However, the spinal canal compression risk resulting from the retropulsed expansion mechanism limits its clinical application. An expandable titanium alloy (Ti-6 Al-4V) device with an anterior expansion mechanism, EVA(r) (Expandable Vertebral Augment system, Chang Gu Biotechnology Co. Ltd., Taipei city, Taiwan), was developed. It consists of a rigid tube encased by a barrel that can be expanded to a desired expansive range by an externally applied compression force through an operation device.