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Updated: Jan 15, 2026
Rapid Mix Preparation of Bioinspired Nanoscale Hydroxyapatite for Biomedical Applications
Published on: February 23, 2017
Enhanced mechanical properties of a novel unsintered hydroxyapatite/poly l-lactic acid (u-HA/PLLA) screw with a
Takuya Wakatsuki1, Shinji Imade1, Satoshi Furuya2
1Department of Orthopaedic Surgery, Shimane University Faculty of Medicine, 89-1 Enya, Izumo, Shimane 693-8501, Japan.
Background:
Although bioabsorbable screws offer various advantages, they also have the clinical drawback of low inherent strength. We developed a novel u-HA/PLLA screw with an innovative shape that maintains the screw function while increasing its strength. The aim of this study was to assess the mechanical properties of this novel screw in comparison to the conventional type.
Methods:
Both the novel and conventional screws had a major diameter of 4.5 mm and a pitch of 1.6 mm. The conventional type had a minor diameter of 3.5 mm (with thread depth of 0.5 mm) and utilized a buttress thread design. In contrast, the novel screw had a minor diameter of 3.7 mm (with thread depth of 0.4 mm) and a reverse buttress thread. Three-point bending, shear, and torsion tests were performed to compare the screw strengths (n = 10). In addition, to compare their pullout strengths, the screws were inserted into two types of simulated bone, one mimicking osteoporotic bone and the other healthy bone (n = 10 replicates for each condition).
Results:
The novel screw exhibited 33 % higher three-point bending strength (p < 0.001), 23 % higher shear strength (p < 0.001), and 24 % higher torsion strength (p < 0.001) than the conventional screw. The fourth parameter of mechanical strength, pullout strength, was not significantly different between the screw types, regardless of the bone conditions.
Conclusion:
The novel u-HA/PLLA screw demonstrated superior mechanical strength while maintaining comparable pullout strength versus the conventional type.
