Preoperative contrast-enhanced ultrasound (CEUS) of long bone nonunions reliably predicts microbiology of tissue culture samples but not of implant-sonication

Low-grade infections in nonunion of the femur and tibia without clinical suspicion of infection - Incidence, microbiology, treatment, and outcome

Treatment algorithms for fracture nonunion depend on the presence or absence of bacterial infection. However, it is often impossible to identify infection preoperatively. While some infections may present with clinical signs of infection, low-grade infections lack infection signs and have a clinical presentation similar to aseptic nonunion. The clinical relevance of low-grade infection in nonunion is not entirely clear. Therefore, the aim of this study was to evaluate the role of low-grade infection in the development and management of lower extremity nonunion. A prospective multicenter clinical study enrolled patients with femoral or tibial shaft nonunion and regular healed fractures, scheduled for nonunion revision and routine implant removal, respectively. Preoperatively, serum markers including C-reactive protein (CRP), leukocytes, and procalcitonin were determined, clinical infection signs were recorded, and a suspected septic or aseptic diagnosis was made prior to surgery and further diagnostics. Tissue samples were collected for microbiology and histopathology, and osteosynthesis material for sonication. Nonunion patients were followed for twelve months, during which the definitive diagnosis of "septic" or "aseptic" nonunion was made according to diagnostic criteria for fracture-related infection. One hundred and ten patients with nonunion and 34 patients with regular healed fractures were included. Sixty-two nonunion patients were diagnosed as aseptic, 22 with expected and confirmed infection, and 23 with unexpected low-grade infection. Three patients had an unclear diagnosis. Low-grade infection was detected in 28 % of presumed aseptic nonunion patients. Sensitivity and specificity for the suspected diagnosis were 49 % and 95 %, respectively. The suspected diagnosis had a significant impact on revision strategy. All medians of the preoperative blood values were within the reference ranges except for CRP, which was slightly elevated in the expected and confirmed infected nonunion group. Expected and confirmed septic nonunion and unexpected low-grade infected nonunion demonstrated a similar bacterial spectrum. While 10 % of patients with aseptic nonunion required follow-up surgeries, re-operation rates were higher in patients with low-grade infection and expected and confirmed infection at 30 % and 64 %, respectively. Patients with low-grade infections were treated less frequently with systemic antibiotics and for a shorter duration than patients with expected and confirmed infections, with no significant difference in healing rate which was 83 % in low-grade and 62 % in expected and confirmed infections. The healing rate of aseptic nonunion was 90 %. A limitation of this study is the limited number of tissue samples for microbiological and histopathological diagnostics in the suspected aseptic nonunion cohort, which may have led to an underestimation of the low-grade infection rate. Our findings suggest that unexpected low-grade infection is frequently associated with nonunion. While expected and confirmed infected nonunion differs significantly from aseptic nonunion, low-grade infected nonunion is very similar to aseptic nonunion, except for intraoperative bacterial detection. In addition to antibiotic therapy, surgical nonunion revision with implant exchange and debridement appears to be highly effective in achieving consolidation of low-grade infected nonunion.

Update of Contrast-enhanced Ultrasound in Musculoskeletal Medicine: Clinical Perspectives - A Review

Contrast-enhanced ultrasound (CEUS) uses an intravascular contrast agent to enhance blood flow signals and assess microcirculation in different parts of the human body. Over the past decade, CEUS has become more widely applied in musculoskeletal (MSK) medicine, and the current review aims to systematically summarize current research on the application of CEUS in the MSK field, focusing on 67 articles published between January 2001 and June 2021 in online databases including PubMed, Scopus, and Embase. CEUS has been widely used for the clinical assessment of muscle microcirculation, tendinopathy, fracture nonunions, sports-related injuries, arthritis, peripheral nerves, and tumors, and can serve as an objective and quantitative evaluation tool for prognosis and outcome prediction. Optimal CEUS parameters and diagnostic cut off values for each disease category remain to be confirmed.