The American Academy of Orthopaedic Surgeons describes total hip replacement as a highly successful surgical intervention, where bone parts of the femur and pelvis are removed and replaced with metal, plastic, or ceramic implants [1]. In this context, tribological studies of the interactions of surfaces in contact under relative motion in biological systems are of interest [2], where joint and implant surfaces experience friction and produce particles (wear) that might be released into the underlying tissue. To reduce material loss, a layer of lubricant can be applied to prevent direct contact [3]. Since hip replacements can last up to 20 years or longer, implants generate damage to adjacent tissues and impaired lubrication loosens the implant [4]. This forces patients with arthroplasties to get revision surgery to change for a new replacement [5]. Furthermore, the longevity of the hip prosthesis might be decreased due to factors such as mechanical instability, or wear [6,7].

At present, according to the information provided by the ESSALUD in Peru on the number of hip replacements and revisions between 2012-2021, the replacement procedure has been increasing until 2019 (1,704 total hip replacements). A similar behavior has been observed in other countries such as the United States, where 2.2 million total hip replacements were recorded between 2012-2020 [1]. The “Organization for Economic Cooperation and Development” reports that Germany leads in the number of hip replacements with 309 surgeries per 100,000 population in 2017, similar to Switzerland, which accounts for 307 [8].

In this scenario, MAX phases (M_n+1AX_n), which are a class of of ternary carbide and nitride with a lamellar crystalline structure, can be used as alternative solid lubricant coatings [9]. In the current work, the tribological behavior of Ti₂AlC and Ti₃AlC₂ coatings on surgical steel AISI 304 and silicon was investigated. Furthermore, their potential application as solid lubricants for future use as a hip prosthesis femoral head coating was assessed. In this regard, silicon has been used as a reference substrate with known properties [10], while AISI 304 has been considered as one possible material for hip implants. Different test speeds (2 and 10 mm/s) and normal forces (0.16 to 1.6 N) were applied (Figure 1). In the tribological experiments with silicon, a decrease of up to 75.0% of the friction coefficient was obtained for Ti₂AlC. For the AISI 304 sample, the Ti₃AlC₂ coating showed a better behavior leading to a decrease of the coefficient of friction of up to 82.5%. In all cases, a reduced wear volume was qualitatively observed. Therefore, it can be concluded that MAX phases are a suitable solid lubricant for an artificial femoral head, which could be potentially used in other joints of the human body.

[1] AAOS; Annual Report AJRR 2021, 2021, ed. 8, pp. 2-3, 22-64 .
[2] J. P. Kretzer, “Biotribology of Total Hip Replacement: The Metal-on-Metal Articulation,” Biotribology, 2013, pp. 1–49.
[3] I. Hutchings and P. Shipway; Friction and wear of engineering materials, 2017, pp. 37-77.
[4] G. Bergmann, F. Graichen, A. Rohlmann, N. Verdonschot, and G. H. van Lenthe;  “Frictional heating of total hip implants, Part 1: measurements in patients” Journal of Biomechanics, 2001, vol. 34, pp. 421–428..
[5] M. Darwich, Ayham; Nazha, Hasan; Daoud, “Effect of Coating Materials on the Fatigue Behavior of Hip Implants: A Three-dimensional Finite Element Analysis,” 2020.
[6] L. E. Bayliss et al., “The effect of patient age at intervention on risk of implant revision after total replacement of the hip or knee: a population-based cohort study", 2017, vol. 389, no. 10077, pp. 1424–1430.
[7] N. D. Quinlan, B. C. Werner, T. E. Brown, and J. A. Browne, “Risk of Prosthetic Joint Infection Increases Following Early Aseptic Revision Surgery of Total Hip and Knee Arthroplasty,” 2020, vol. 35, no. 12, pp. 3661–3667.
[8]  C. Pabinger, H. Lothaller, N. Portner, and A. Geissler;  “Projections of hip arthroplasty in OECD countries up to 2050” HIP International, 2018, vol. 28, pp. 498–506.
[9] P. Eklund, M. Beckers, U. Jansson, H. Högberg, and L. Hultman;  “The Mn + 1AXn phases: Materials science and thin-film processing” Thin Solid Films, 2010, vol. 518, pp. 1851–1878.
[10] C. Torres et al., “Development of the phase composition and the properties of Ti2AlC and Ti3AlC2 MAX-phase thin films – A multilayer approach towards high phase purity,” 2021, vol. 537, p. 147864.