Introduction:
Fracture-related infections (FRI) and periprosthetic joint infections (PJI) represent a major challenge in orthopedic surgery. Incidence of both entities is annually growing. Comorbidities play an important role as an influencing factor for infection and thus, for prevention and treatment strategies. The aims of this study were (1) to analyze the frequency of comorbidities in FRI and PJI patients and (2) to evaluate comorbidities as causative risk factor for PJI and FRI.

Methods:
This retrospective cohort study analysed all ICD-10 codes, which were coded as secondary diagnosis in all in hospital-treated FRI and PJI in the year 2019 in Germany provided by the Federal Statistical Office of Germany (Destatis). Prevalence of comorbidities was compared with the prevalence in the general population.

Results:
In the year 2019, 7158 FRIs and 16,174 PJIs were registered in Germany, with 68,304 comorbidities in FRI (mean: 9.5 per case) and 188,684 in PJI (mean: 11.7 per case). Major localization for FRI were infections in the lower leg (55.4%) and
forearm (9.2%), while PJI were located mostly at hip (47.4%) and knee joints (45.5%). Mainly arterial hypertension (FRI: n = 3645; 50.9%—PJI: n = 11360; 70.2%), diabetes mellitus type II (FRI: n = 1483; 20.7%—PJI: n = 3999; 24.7%), obesity (FRI: n = 749; 10.5%—PJI: n = 3434; 21.2%) and chronic kidney
failure (FRI: n = 877; 12.3%—PJI: n = 3341; 20.7%) were documented. Compared with the general population, an increased risk for PJI and FRI was reported in patients with diabetes mellitus (PJI: 2.988; FRI: 2.339), arterial hypertension (PJI: 5.059; FRI: 2.116) and heart failure (PJI: 6.513; FRI: 3.801).

Conclusion:
Patients with endocrinological and cardiovascular diseases, in particular associated with the metabolic syndrome, demonstrate an increased risk for orthopedic implant related infections. Based on the present results, further infection prevention and treatment strategies should be evaluated.