Experimental study of the strength of bone plates made of composite material based on polylactide, tricalcium phosphate and hydroxylapatite

Background. In orthopedics and traumatology, polymer materials that are resorbed and dissolve in biological fluids occupy a significant place as screws and fixation pins, plates and anchors, cages. Most often, implants from L-polylactic acid (PLA) are used. It is possible to increase their quality by including ceramic materials into their composition, in particular tricalcium phosphate (TCF) and hydroxylapatite (HA). However, implants with different percentages and compositions of ceramic material differ in strength and behavior in bone. The purpose was to check the bending strength of plates made of a composite material based on polylactide, tricalcium phosphate and hydroxylapatite for compliance with the calculated indicators under experimental conditions. Materials and methods. Plate samples were made from a material containing 70 % PLA, 20 % TCF and 10 % HA. Using the 3D printing method, plates with a thickness of 8.5, 9.5, and 10.7 mm were produced which, according to the calculated data, correspond to the patient’s weight of 50, 70, and 100 kg, respectively. A total of 3 plates of each size were made. All samples were tested for bending. The load magnitude increased gradually from 100 to 1000 N with a step of 100 N. At each step, the deflection of the sample was recorded. Results. As a result of the research, the deflection was evaluated for samples of plates with different thicknesses made of composite material based on PLA, TCF and HA, depending on the load magnitude. The deflection of the plate samples was checked under loads corresponding to the patient’s weight for which they were calculated — 50, 70 and 100 kg, and the permissible limit of deflection, for which the calculated deflection of the standard titanium plate was chosen. The results showed that the deflection indicators of all samples do not have statistically significant deviations from the permissible limit. For all groups of samples, the p criterion significantly exceeds the critical value of 0.05. Conclusions. Experimental studies on the bending strength of plates made of composite material containing 70 % PLA, 20 % TCF and 10 % HA proved that the deflection of all tested samples correspond to the calculated values, the deviations of the indicators do not exceed the permissible level of 5 %.