Peri-implant soft tissue colonization after osteosynthesis in asymptomatic patients: a prospective study

Fracture-related infection (FRI) remains a serious complication in orthopedic trauma surgery, with microbiological confirmation based on positive cultures from deep tissue samples. However, the clinical interpretation of positive microbiological findings in asymptomatic patients remains unclear. This prospective study aimed to evaluate the incidence and characteristics of peri-implant soft tissue colonization in patients undergoing routine removal of osteosynthetic material without clinical or radiological signs of FRI. Indications for implant removal surgery included routine removal, prominence of osteosynthetic material, discomfort, removal prior to prosthetic joint implantation or patient request. It is a single-center prospective study. A total of 137 adult patients undergoing implant removal between 01/09/2023 and 30/11/2025 were included. For each patient, five deep tissue samples and the removed implant were collected for microbiological analysis, including sonication fluid culture. Histological evaluation was performed in a subset of cases. Peri-implant colonization was defined as the presence of identical pathogens in at least two tissue samples. All patients underwent routine postoperative clinical follow-up after implant removal surgery. Wound healing and local clinical status were assessed at the time of suture removal, typically 12-14 days postoperatively. In addition, all patients were instructed to return for further clinical evaluation in the event of any wound healing problems, local inflammatory signs or other symptoms involving the operated region. Peri-implant soft tissue colonization was detected in 32.8% of patients, while overall microbiological positivity (including sonication) reached 38.7%. Sonication and tissue cultures demonstrated comparable detection rates, with isolated positivity observed in 5.8% of cases. Histological positivity was rare (2.75%) and showed limited concordance with microbiological findings. Colonization rates varied significantly by anatomical location, with markedly higher prevalence in the shoulder region compared to other sites (70.0 vs. 20.7%, p < 0.001). In multivariable logistic regression analysis, shoulder region location was a strong independent predictor of culture positivity (OR 25.45, 95% CI 8.00-80.65), while male sex was also independently associated with positive cultures (adjusted OR 6.42, 95% Cl 2.11-19.51, p = 0.001). The microbiological spectrum was dominated by low virulence, predominantly polymicrobial flora, with Cutibacterium acnes as the most frequently identified organism. These findings demonstrate that peri-implant colonization is common in clinically asymptomatic patients, particularly in the shoulder region. Shoulder region localization and male sex were independently associated with microbiological positivity. Positive microbiological results should therefore be interpreted with caution and in the context of clinical, radiological and histopathological findings to avoid overdiagnosis of FRI and unnecessary treatment.