gms | German Medical Science

Objectives: Implant-associated infections are one of the most serious complications of hip replacement surgery. The infection rate between elective and trauma surgery differs significantly, but the reasons for this are still enigmatic. This is the first study to assess the aspect of patient’s immunological competence by investigating the distribution and phenotype of immune cells in a longitudinal study design. We hypothesize that patients’ immunological competence is a key factor in the development of implant-associated infection and responsible for the higher infection rate between elective and trauma surgery.

Methods: In a prospective study design (pre-op, 1 d, 3 d, 7 d post-op), a quantitative analysis of immunological cells of patients undergoing hip arthroplasty were performed. The study group (n=37) was composed of patients undergoing total hip arthroplasty due to osteoarthritis (n=24) and femoral neck fracture (n=15). Flow cytometric analysis of peripheral blood included assessment of monocytes (CD14+), Th subsets Th1 (CCR4- CCR6- CCR10- CXCR3+CCR5+), Th2 (CCR4+ CCR6- CCR3- CXCR3-), Th9 (CCR4- CCR6+), Th17 (CCR4+CCR6+CCR10-CXCR3-), Th22 (CCR4+ CCR6+ CCR10+), Tregs (CD25+ CD127-), and additional cell types (CD19+ CD56+ CD3+ CD8+). Samples were compared using a one-way repeated measures ANOVA with Geisser-Greenhouse correction. The data are presented as the mean ± SEM.

Results and conclusion: Immune cell frequencies showed a temporal pattern in both groups but these tendencies did not reach statistical significance. Neutrophils showed an increase at day 1 and a further drop to the pre-operative level over time. Th22 and Th17 cells decreased immediately after surgery (day 1) and recovered until day 7. Some cell population (Th9, B cells) showed no change between time points and others a steady decrease until the final analysis (Treg, Th22). Already before surgery, both groups showed significant difference in Th17 and Th22 frequencies. There were significant differences between the OA and the fracture group at day 1 for Th17, Th22, neutrophils and at day 3 for Treg, Th2 and monocytes. Further, at day 7 Treg, Th17, Th22 were significantly decreased and neutrophils was significantly higher in the fracture group as shown in Figure 1 [Fig. 1].

Our data indicate that significant differences in immune cell frequencies are already present between these groups and further differences develop after surgery. These results indicate, that immune competence could be an important factor in the development of implant-associated infections. How these quantitative differences translate into a compromised immune competence and result in higher infection rates need to be further evaluated.