Improved Diagnosis of Infection Associated with Osteosynthesis by Use of Sonication of Fracture Fixation Implants

Abstract

Previous studies have shown that sonication fluid cultures from removed orthopedic devices improved the microbiological diagnosis of orthopedic implant-associated infections; however, few of these investigations have applied sonication to the removed fracture fixation devices to evaluate its utility for the diagnosis of osteosynthesis-associated infection (OAI). We compared sonication fluid to conventional tissue cultures from 180 subjects with different sizes of plates and screws (n ‫؍‬ 156), spinal implants (n ‫؍‬ 26), and intramedullary nails (n ‫؍‬ 3), of whom 125 and 55 subjects had OAI and noninfected osteosynthesis (NIO), respectively. The sensitivity for detecting OAI was 90.4% for sonication fluid culture and 56.8% for periprosthetic tissue cultures (P < 0.05), and the specificities were 90.9% and 96.4%, respectively. Sonication fluid culture detected more pathogens than peri-implant tissue culture (113 versus 71; P < 0.001), while polymicrobial infections were diagnosed by sonication fluid cultures and tissue cultures in 20.8% and 8% (P < 0.001), respectively. Microbiological diagnosis was achieved exclusively by sonication fluid cultures for 47 (90.4%) subjects, and among them, 18 (38.3%) had previously received antibiotics, whereas in five (9.6%) infected subjects, tissue culture was positive and the sonication fluid culture was negative. Among 39 (31.2%) OAI cases receiving antibiotics, the identification of the organisms occurred in 38.5% and 82.1% of the tissue and sonication fluid cultures, respectively (P < 0.049). We demonstrated that sonication fluid culture from removed osteosyntheses has the potential for improving the microbiological diagnosis of OAI. Due to the increasing occurrence of trauma and injuries, particularly those associated with road traffic accidents (1), surgical implantation of orthopedic devices for fracture fixations (or osteosynthesis), including intramedullary nails, different size plates, screws, and external fixation pins, have increased. Indeed, the acute management of bone fractures in trauma patients has evolved steadily, and there is an expanded indication for osteosynthesis, with the aim of early stabilization of the fractures. Depending upon the physiological condition of the patient, especially those with unstable polytrauma and significant lower extremity injuries, surgeons must choose the less aggressive external fixation first step for fracture stabilization (2). Once the adequate local wound debridement is ensured, which includes the removal of all dead and infected tissues and the stabilization of the systemic clinical condition of the patient, secondary major osteosynthesis is then performed with either plates and screws or intramedullary nails (3).Following orthopedic surgery, secondary soft tissue and implant-associated bone infections are still the most important negative aspects and limiting factors of success, leading to significant morbidity, including delayed bone union or nonunion, multiple additional debridement, or even amputation. Wound contamin...

Concentration of Sonication Fluid through Centrifugation Is Superior to Membrane Filtration for Microbial Diagnosis of Orthopedic Implant-Associated Infection

“…Previous studies have shown that liquid cultures seem to provide better conditions to sessile bacterial growth than solid media (9,10). As already shown in previous studies addressing OIAI and prosthetic joint infection, Gram-positive bacteria were the most common sessile pathogens isolated in SC (60.6%) and SMF (72.7%), followed by Gram-negative bacilli, which have been increasingly identified among subjects presenting OIAIs (3,11). Our study had limitations, including the small sample size analyzed and the lack of a universally accepted clinical diagnosis of OIAI.…”

“…everal authors have applied a sonication technique as an adjunctive diagnostic tool to increase the identification of causative agents of different orthopedic implant-associated infections (OIAIs) (1)(2)(3). However, sonication may also give false-negative results in at least 10% to 20% of cases when applying only phenotypic methods (4).…”

“…Depending on the size of the retrieved implant and the container used, the total volume of Ringer's solution used to fill the container to partially cover the device may vary from 50 ml (sonication of screws and small plates) to 500 ml (large prosthetic joints). Therefore, many researchers have added an SF concentration step using sample centrifugation (3,(6)(7)(8)(9). Applying filtration to the total volume of SF through known-pore-size membranes and plating these membranes onto solid and in liquid culture media would increase the number of microorganisms identified.…”

“…Colonies of isolated microorganisms growing on plates were quantified (number of CFU/ml SF) and identified, and their susceptibility to antibiotics was tested according to standard microbiological techniques. Due to the addition of centrifugation and membrane filtration concentration steps to the SF culture, a cutoff of 50 CFU/plate was considered positive and used for ideal sensitivity analysis (3,6). Likewise, patients who received antibiotics for at least 24 h in the 14 days prior to surgery were considered positive regardless of their CFU values (1,3).…”

“…Due to the addition of centrifugation and membrane filtration concentration steps to the SF culture, a cutoff of 50 CFU/plate was considered positive and used for ideal sensitivity analysis (3,6). Likewise, patients who received antibiotics for at least 24 h in the 14 days prior to surgery were considered positive regardless of their CFU values (1,3). Characteristics of the subjects were summarized as frequencies and percentages or means (range) and standard deviations.…”