Irkutsk National Research Technical University, Irkutsk, Russia

A. S. Pyatykh, Associate Professor at the Department of Technology and Equipment of Machine-Building Production, Candidate of Technical Sciences, e-mail: pyatykhas@ex.istu.edu
A. V. Savilov, Associate Professor at the Department of Technology and Equipment of Machine-Building Production, Candidate of Technical Sciences, Associate Professor, e-mail: saw@istu.edu
A. P. Chapyshev, Associate Professor at the Department of Technology and Equipment of Machine-Building Production, Candidate of Technical Sciences, Associate Professor, e-mail: chapsh@mail.ru

Titanium alloy pedicle screws for spine osteosynthesis application must ensure minimum failures in a patient’s system, minimum post-surgery rejections and shorter rehabilitation times. All this could be achieved through a special surface topography of the screw threads, which should help intensify the growth of bone tissue around the screw. This paper gives an overview of the most popular techniques for forming the implant topography. Both advantages and disadvantages are demonstrated. One of the most affordable techniques for obtaining the required topographical properties, as well as for creating a favourable stress state in the surface layers of screws, includes blasting with solid particles (i.e. sandblasting). The paper describes the results of an experimental study that looked at the effect of sandblasting parameters on the surface morphology of titanium implants when the process combines sandblasting with turning. The threaded surface was pre-shaped by turning. The threading speed was taken as a varying parameter. White alumina (Al₂O₃) sand was used for sandblasting. The sample implant was not rotated around its axis in the sand jet in order to further analyze how the angle of the abrasive jet to the target surface could impact the topography. Optical profile meter was used to measure the topography of sandblasted specimens. Changes in the surface morphology were analyzed based on the changed microrelief, as well as some quantitative parameters indicating the resultant roughness depth and shape. The roughness depth was determined based on average roughness height along the traversed length, while the roughness shape – based on dimensionless parameters of roughness profile asymmetry and peakedness. It was found that the surface formed by turning is characterized by monoaxial regularity, i.e. the roughness lines go along the thread gaps. This can affect the implant survival rate. It was found that sandblasting helped achieve a good roughness orientation in all specimens. The authors documented the fact of the asymmetry and peakedness parameters being inherited when sandblasting is combined with turning if the target surface is at right angle to the nozzle axis. The obtained results can be used in actual production environment for manufacturing titanium implants for osteosynthsis.
This research was funded under Grant No. MK-2982.2022.4 by the President of the Russian Federation aimed at supporting young Russian researchers with PhD degrees: Enhanced Efficiency of the Process for Making Medical Implants out of Titanium Alloys.
This research was funded by the Russian Foundation for Innovation Support under Contract No. 3440GS1/57422 dated 18/02/2020 (Code 0057422), Application No. S1-69876, Competition Start-19-1 (Phase 4).

1. Pedicle Screw System Market. Global Industry Analysis 2014–2018 and Opportunity Assessment 2019–2029. 2019 Future Market Insights.
2. Karpov V. N., Mamonov A. M., Spektor V. S. et al. Design of high-load titanium alloy implants: Engineering and production aspects. Titan. 2010. No. 3(29). pp. 43–51.
3. Chechulin B. B., Ushakov S. S., Razuvaeva I. N., Goldfayn V. N. Mechanical engineering and titanium alloys. Leningrad : Mashinostroenie, 1977. 248 p.
4. Varghese V., Kumar G. S., Krishnan V. Effect of various factors on pull out strength of pedicle screw in normal and osteoporotic cancellous bone models. Medical Engineering & Physics. 2017. Vol. 40. pp. 28–38.
5. Liu H. et al. Comparison of the accuracy between robot-assisted and conventional freehand pedicle screw placement: a systematic review and metaanalysis. International Journal of Computer Assisted Radiology and Surgery. 2016. Vol. 11. pp. 2273–2281.
6. Pavlova T. V., Pavlova L. A., Nesterov A. V. et al. A comparative analysis of skull bones during implantation of titanium biocomposites the coating of which contains morphogenetic protein BMP-2. Bulletin of Experimental Biology and Medicine. 2014. Vol. 158, No. 8. pp. 246–249.

7. Pavlova L. A., Krivetskiy L. A., Nesterov V. V. et al. Characteristic of reparative processes when using ВМР-2 containing biocomposites based on nanostructured titanium implants during early stages of regeneration. Sistemnyi analiz i upravlenie v biomeditsinskikh sistemakh. 2010. Vol. 9, No. 1. pp. 200–203.
8. Heinrich A., Dengler K., Koerner T. et al. Laser-modified titanium implants for improved cell adhesion. Medical alphabet. 2010. Vol. 4, No. 16. pp. 47–50.
9. Mishina K. S. Bioactive coatings for orthopedic implants – Latest trends in implant coating technology. Science and Youth: Problems, Search, Solutions : Proceedings of the Russian National Science Conference of Under- and Postgraduates and Young Researchers. Novokuznetsk, 14–16 May 2019. Novokuznetsk : Sibirskiy gosudarstvennyi industrialnyi universitet, 2019. pp. 331–333.
10. Calvarese M. et al. Recent developments and advances of femtosecond laser ablation: Towards image-guided microsurgery probes. TrAC Trends in Analytical Chemistry. 2023. Vol. 167. 117250.
11. Ionin A. A., Kudryashov S. I., Samokhin A. A. Material surface ablation produced by ultrashort laser pulses. Physics-Uspekhi. 2017. Vol. 60, Iss. 2. pp. 149–160.
12. Ashforth S. A. et al. Femtosecond lasers for high-precision orthopedic surgery. Lasers in Medical Science. 2020. Vol. 35. pp. 1263–1270.
13. Li C. L. et al. Orthopedics-related applications of ultrafast laser and its recent advances. Applied Sciences. 2022. Vol. 12, Iss. 8. 3957.
14. Nazarov D. V. et al. Enhanced osseointegrative properties of ultra-finegrained titanium implants modified by chemical etching and atomic layer deposition. ACS Biomaterials Science & Engineering. 2018. Vol. 4, Iss. 9. pp. 3268–3281.
15. Hayles A. et al. Hydrothermally etched titanium: A review on a promising mechano-bactericidal surface for implant applications. Materials Today Chemistry. 2021. Vol. 22. 100622.
16. Chouirfa H. et al. Review of titanium surface modification techniques and coatings for antibacterial applications. Acta Biomaterialia. 2019. Vol. 83. pp. 37–54.
17. Singh G. et al. Impact of post-heat-treatment on the surface-roughness, residual stresses, and micromorphology characteristics of plasma-sprayed pure hydroxyapatite and 7%-Aloxite reinforced hydroxyapatite coatings deposited on titanium alloy-based biomedical implants. Journal of Materials Research and Technology. 2022. Vol. 18. pp. 1358–1380.
18. Bourne R. B. et al. Ingrowth surfaces: plasma spray coating to titanium alloy hip replacements. Clinical Orthopaedics and Related Research (1976–2007). 1994. Vol. 298. pp. 37–46.
19. Veronesi F. et al. Osseointegration is improved by coating titanium implants with a nanostructured thin film with titanium carbide and titanium oxides clustered around graphitic carbon. Materials Science and Engineering: C. 2017. Vol. 70. pp. 264–271.
20. Azizov R. O., Vokhidov A. A., Mirzamidinov I. M., Dadodzhonov M. Steel part surface quality improved by sandblasting. Polytechnical bulletin. Series: Engineering Studies. 2019. No. 1 (45). pp. 103–109.
21. Alontseva D. L., Rusakova A. V., Prokhorenkova N. V. et al. A study of the porosity, roughness and corrosion resistance of biocompatible coatings plasma sprayed onto titanium implants. Bulletin of D. Serikbayev East Kazakhstan Technical University. 2019. No. 2. pp. 70–77.
22. Gittens R. A., Olivares-Navarrete R., Schwartz Z., Boyan B. D. Implant osseointegration and the role of microroughness and nanostructures: lessons for spine implants. Acta Biomaterialia. 2014. Vol. 8, Iss. 10. pp. 3363–3371.
23. Ding Q., Wu Z., Tao K. et al. Environment tolerant, adaptable and stretchable organohydrogels: preparation, optimization, and applications. Materials Horizons. 2022. Vol. 9. pp. 1356–1386.
24. Plotnikov A. L., Sergeev A. S., Zaytseva N. G. Surface roughness resulting from lathe machining of corrosion-resistant steels and development of mathematical models for calculating the preset roughness parameter Ra of the machined surface. Metalloobrabotka. 2015. No. 2(86). pp. 2–6.