Basic Research on a Cylindrical Implant Made of Shape-Memory Alloy for the Treatment of Long Bone Fracture

Eiji Kawakita 1, Zhuo Wang 2, Takaya Kato 3, Tadashi Inaba 4, Yuichi Kasai*, 2
1 Department of Orthopaedic Surgery, Saiseikai Matsusaka Hospital, Japan
2 Department of Spinal Surgery and Medical Engineering, Mie University Graduate School of Medicine, Japan
3 Community-University Research Cooperation Center, Mie University, Japan
4 Department of Mechanical Engineering, Mie University, Japan

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© Kawakita et al.; Licensee Bentham Open.

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at the Department of Spinal Surgery and Medical Engineering, Mie University Graduate School of Medicine, 2-174 Edobashi, Tsu, Mie, 514-8507, Japan; Tel: +81-59-231-6024; Fax: +81-59-231-6032; E-mail:


The internal fixing materials made from shape-memory alloys (SMAs) have recently been reported for long bone fracture. We present a new internal fixation technique using a cylindrical SMAs implant in a rat femoral fracture healing. The implant was designed in a shape to circumferentially fix the fractured bone using resilient SMA claws. To evaluate the fixing ability of the implant, three-point bending and rotation tests were performed. Fifteen female Wister rats were treated surgically as an experimental model. All rats were killed at 16 weeks postoperatively, and the radiological and histological evaluations were performed. In biomechanical test, the good fixation ability of the implant was demonstrated. In animal model, no cases of postoperative infection or death were encountered and postoperative gait was stable in all cases. Radiological examination at 16 weeks postoperatively demonstrated the implant firmly fixed to the fractured part, endosteal healing, and no callus formation in all cases. In Histological evaluation, bone union in all cases was characterized by endochondral ossification from within the medullary cavity. In conclusion, our cylindrical SMA implant provided good fixation in biomechanical tests, and achieved bone union in all 15 rats. If a larger size is designed in the future, our implant will be a clinically applicable, useful fixing material for fracture of the human long bones.

Keywords: Bone fusion, experimental study, fracture, implants, internal fixation, shape-memory alloys.