Biomechanical comparison between bioabsorbable and medical titanium screws in distal chevron osteotomy of first metatarsal in hallux valgus treatment

• Published in: Journal of the mechanical behavior of biomedical materials Vol. 131; p. 105260
• Main Authors: Liu, Changyi, Huang, Lingshuai, Zhang, Hanyang, Chang, Fei, Li, Shichao, Ma, Songning, Zhang, Yu, Ren, Luquan
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Ltd 01.07.2022
• Subjects: Bioabsorbable screw; Biomechanical testing; Chevron osteotomy; Digital image correlation (DIC); Hallux valgus; Hallux valgus; Digital image correlation (DIC); Bioabsorbable screw; Chevron osteotomy; Biomechanical testing
• ISSN: 1751-6161; 1878-0180; 1878-0180
• DOI: 10.1016/j.jmbbm.2022.105260

Polylactic acid (PLA) composite materials have been used for manufacturing surgical internal fixations owing to their satisfactory mechanical strength and absorbability. This, in turn, reduces the pain and risks associated with the secondary operation on patients. Although the mechanical properties of bioabsorbable materials have been considerably enhanced via modifications and optimization, the strength and stiffness of these materials are considerably inferior to those of metals. Therefore, whether PLA fixation can satisfy the required mechanical properties has been a consistent subject of interest in clinical practice. In this study, the mechanical properties of PLA bioabsorbable (Changchun SinoBiomaterials Co., Ltd., China) and titanium hollow screws (Shanghai Carefix Medical Instrument Co., Ltd., China) were compared in hallux valgus surgery with chevron osteotomy. Three-dimensionally printed osteotomy guides were used for cutting the artificial first metatarsal model (SKU3422, Sawbones) to reduce the errors due to the variations in individual bone densities and osteotomy angles; the cut parts were subsequently fixed with the PLA and titanium alloy screws. A digital image correlation system was used to obtain the full-field strain of the specimen to evaluate the mechanical behaviors under static and fatigue loads. The experimental results demonstrated that, by designing a reasonable osteotomy angle, the compressive strength of the specimen with PLA screws under chevron osteotomy can be as high as that of the specimen with titanium screws. Moreover, their stiffness can reach up to 60%–90% that of titanium screws. After 240,000 cycles of compression, the PLA screws maintained their strength and stiffness. These bioabsorbable fixtures can effectively prevent stress shielding under a suitable osteotomy. Hence, as an optimal substitute for metal fixtures, an increase in clinical applications to surgery is anticipated, along with progressive in-depth research on the biomechanical properties of bioabsorbable materials.