CD16+ Monocyte Subsets in Patients with Total Joint Arthroplasty

Total joint arthroplasty (TJA) is a surgical procedure in which parts of an arthritic or damaged joint are removed and replaced with a metal, plastic or ceramic device called a prosthesis. In the USA, more than 500,000 total joint arthroplasty (TJA) operations. Though the technical advances, many patients still require surgical revision for aseptic loosening (AL) and/or bone loss due to osteolysis.

There are two monocyte populations in human blood: CD14⁺CD16^- classical monocytes and CD14⁺CD16⁺ inflammatory monocytes. CD14⁺CD16⁺ inflammatory monocytes, which account for approximately 10% of the total monocytes, may be expanded in various types of inflammatory conditions. The purpose of this study was to investigate whether the expansion of the CD14⁺CD16⁺monocyte population represented a risk factor of aseptic loosening (AL). 

In this study, peripheral monocytes subsets were measured in revision patients with AL (n = 35) and in patients with stable implants (SI, n = 56). The gene profiles of TNFα, IL-1β, CD16, CD68 and TRAP5B from collected loosening periprosthetic tissues were analyzed. The results showed that there were no significant differences in the CD14⁺CD16⁺ monocyte populations between the SI and AL patients. The CD14⁺CD16⁺ monocytes were marginally higher in revision patients with osteolysis (n = 30), compared to patients without osteolysis (n = 5) though no statistically difference was found. There was an association between the CD14⁺CD16⁺ monocyte subpopulation and the tissue gene profiles, including IL-1β (p = 0.063), CD68 (p = 0.036), and TRAP5B (p = 0.073). 

 In conclusion, it was demonstrated that the expansion of CD14⁺CD16⁺ monocytes reflected, to some extent, the inflammatory status of the loosening periprosthetic tissues. It is unclear if some of those SI patients (no pain and negative radiograph) who have a higher frequency of CD14⁺CD16⁺ monocytes may be at the early stage of AL. Further evaluation of CD14⁺CD16⁺ monocyte population, independently or combined with other factors, will be useful to design a risk profile for AL incidence and progression.

Article by David C. Markel, et al, from USA.

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