Fabrication of Musculoskeletal Joints using Biodegradable Polymer Nanocomposites

Fracture fixation components and implants are widely used in orthopedic surgery as well as dentistry. The use of metal stabilizers is very common, which imposes the need for a second surgery to remove the implant from the body. One of the most common implants is the interference screw, which is used in many bone injuries. Therefore, the purpose of this research is to obtain an optimal sample for use as an interference screw, and for this purpose, nanocomposites with different percentages of nanomaterials were made.

This study was conducted as a research study and 9 samples were made and examined. For this purpose, hand injection molding, was designed to prepare screws in laboratory scale, first. For making samples, poly (L) lactic acid, nano hydroxyapatite as reinforce and polyethylene glycol as plasticizer were used. These samples were made by combination of solvent casting and melt processing methods. Adding nano hydroxyapatite and polyethylene glycol together lead to improve tensile and percent elongation of samples. After doing different tests like tensile, rheology, biodegradability and biocompatibility, the optimized sample was chosen. Data were obtained as mean ± standard deviation (MEAN ± SD) and for statistical analysis SPSS software (version 16) was used and one-way analysis of variance (ANOVA) was used, the level of significant differences with P< 0 / 005 was calculated.

It was found that the simultaneous addition of nanohydroxyapatite and polyethylene glycol increased the strength and elongation at break of the samples. The optimal Young's modulus was 589/93 ± 43/912 MPa and the Young's modulus of the polymeric matrix was 615/4± 48/421. Although the polymer matrix has a higher Young's modulus, it is not suitable for use in areas under load due to its inherent fragility and also has low bioactivity. The rate of increase in elongation at break of the optimal sample was 13/39 ± 2/731 and for the polymeric matrix was 11/01± 1/348.

Findings obtained from this study showed that the optimal sample of this study (1051) with 1% hydroxyapatite and 5% polyethylene glycol. Because it has the highest percentage of elongation and the lowest degree of fragility and can be an optimal formula for biodegradable interference screws.