Short summary

Periprosthetic joint infection (PJI) is a feared complication of total joint arthroplasty. The microbiology agent causing these infections is challenging to diagnose. Sonication (SFC) is an ultrasound bath that takes apart biofilm and detaches microbiology from an object. Because of this, SFC is thought to have an improved ability to diagnose infections growing inside a biofilm on prostheses, which PJI does. This Study is a follow-up to a PhD study on sonication from 2012-2013.

Rationale

Periprosthetic Joint Infection (PJI) is a rare yet severe complication for patients undergoing total hip and knee arthroplasty (THA and TKA). The prevalence of PJI is around 1% within the first year after THA, and it is associated with high morbidity. The growing population and prolonged expected lifetime result in a rise in the number of arthroplasty patients and PJI every year.

PJI is divided into acute and subacute or indolent infections. Bacteria are thought to be either in a planktonic state or multicellular aggregates. The multicellular aggregates consist of a mix of host cells, the bacteria, and their extracellular polymeric substance. which together forms a microenvironment for the infection. The concentrations of metabolic substrates, such as oxygen and glucose, decrease from the exterior to the interior of the aggregates while concentrations of metabolic products increases from the exterior to the interior. This microenvironment is believed to be the cause of the indolent infections, because the low substrate and high product might foster conditions where bacteria grows slower, while immune cells and antibiotics are hindered in killing bacteria due hypoxia and low metabolic activity of the bacteria. These multicellular aggregates is also known as biofilm and can attach to an implant such as a hip or knee prosthesis.

When trying to diagnose these indolent infections, culturing in vitro, can be challenging as the low metabolic state as mentioned above hampers growth making it difficult to differentiate from aseptic loosening.() Sonication fluid culturing (SFC) targets biofilm and has shown increased sensitivity for diagnosing PJI in some studies. These studies compare SFC to tissue sampling culturing (TSC) and show a sensitivity between 73-90% and a specificity of 90-95%. In the same studies, TSC had a lower sensitivity and specificity of 61-71% and 93-95%. When combining the two methods, a higher sensitivity was shown compared to any of the two methods alone.

In Denmark, 3-5 TSCs are used for microbiology, and SFC is not widely used in diagnosing PJI. (13) A danish study from 2019 investigating the risk of 2nd revision after revision of presumed aseptic loosening with one single or mixed unexpected positive TSC found an increased risk for 2nd revision compared to negative TSC. The study stated that better strategies for diagnosing PJI is needed and mention sonication as a likely strategy.

Even though SFC may contribute to better diagnosing PJI, no studies on the long-term outcome after revision where SFC was performed are published.

Aim We aim to investigate the effect of SFC added to TSC in diagnosing PJI after revision of THA or TKA on complications, implant survivorship and mortality. Secondly we aim to identify concordance and discordance between SFC and TSC.

Description of the cohort

A predefined cohort consist of 211 patients who have undergone revision of THA/TKA at the orthopaedic departments at Vejle Hospital and Odense University Hospital during a one-year study period from November 1, 2012, to October 31, 2013. The inclusion criterion was a revision of THA and TKA of any indication.

Data and biological material

Operation data from revisions of TKA and THA completed between 01-09-2012 until 30-05-2023 including debridement, antibiotics, and implant retention (DAIR), resection arthroplasty (Girdlestone), arthrodesis, amputation.

Futher more datas on sepsis, long-term antibiotic treatment and death.

Data will be collected from patient's medical files, from the Danish Hip Arthroplasty Register and the Danish Knee Arthroplasty Register and the Danish National Patient Register.

Collaborating researchers and departments

Department of Orthopaedic Surgery, Lillebaelt Hospital - Vejle,

• Claus Varnum, Associate Professor, PhD

Department of Orthopaedic Surgery, Aarhus University Hospital

• Christen Ravn, PhD

Department of Orthopaedic Surgery, Bispebjerg Hospital and Frederiksberg Hospital,

• Søren Overgaard Professor, DMSc