This study confirms the variety in diagnostic strategies that many clinicians dealing with PTO will recognise from their day-to-day practice. Although the overall response rate of our survey was only 15%, the responders are a typical reflection of those working with this patient group (Table 1). One should also keep in mind that it is only a small percentage of all trauma and orthopaedic surgeons who are involved in osteomyelitis care and that we addressed the whole group. Because it is likely that the responders will have an interest in—and, therefore, deeper knowledge of—PTO compared to non-responders, this study is prone to even underestimate the real variety in diagnostic imaging strategies as the first diagnostic manoeuvres might be initiated by the primary surgeon. We, therefore, regard the contribution from 346 medical practitioners as a substantial response and the outcome of this survey as a relevant finding to report to our peers.
The variation in diagnostic workup of patients with suspected PTO is in concordance with the lacking guidelines on this subject and also with the apparent struggle of various authors to formulate clear and practical recommendations. Termaat et al. published a meta-analysis on optimal imaging modalities for chronic osteomyelitis [18]. They concluded that FDG-PET was the most accurate imaging option to diagnose chronic osteomyelitis, with a sensitivity and specificity of 96 and 91%, respectively. However, the paper was published in 2005 and includes studies published between 1975 and 2003. Considering that current medical technology is developing at an almost exponential rate, it is safe to assume that the diagnostic capacities of the different imaging modalities described are no longer truly represented by the papers analysed for that study (e.g., the commercial system to combine PET with CT (PET/CT) first reached the market in 2001 [26]). The data in that paper should, therefore, be interpreted cautiously. Also based on the best available evidence, but still a result from a consensus meeting, is the report of the European Association of Nuclear Medicine (EANM) published in 2014. In this paper, Jutte et al. proposed a diagnostic flowchart for peripheral bone osteomyelitis, including sternal infections [14]. This flowchart is probably the best available tool for clinicians at the moment, but it is a very broad algorithm with an emphasis on nuclear imaging. In the present study, recommendations of this EANM consensus document were not followed by the majority of responders in any of the scenarios presented.
Part of the variance in diagnostic imaging strategies for PTO can be explained from the imaging techniques locally available to the requesting (or advising) medical practitioner (Table 3). Responders tended to favour an imaging modality when this was available in their hospital. Although this is an understandable pragmatic choice, it may not be the most cost-effective strategy. Having an evidence-based guideline for diagnosing (and excluding) PTO will support a radiology and/or nuclear medicine department in negotiating the purchase of future appropriate medical imaging equipment.
Yet another possible explanation for the variance between the subgroups is that, in The Netherlands, the majority of fractures are treated by trauma surgeons who are trained as general surgeons, as opposed to orthopaedic surgeons (66 versus 34%, respectively, as reported in a recent study on hip fractures [27]). Orthopaedic surgeons are more familiar with the (more researched) concept of prosthetic joint infections (PJI), and some of their choices for diagnosing PTO might be extrapolated from these papers. Dutch trauma surgeons, however, focus solely on fractures and are not influenced by previous knowledge on diagnosing PJI, therefore, they might have a different approach to diagnosing fracture-related infections. The same can be said for radiologists versus nuclear medicine physicians—both are highly trained in medical imaging options for various infectious conditions—but they are likely biased by background knowledge of their own area of expertise. This bias does explain the difference in preferred imaging modalities (e.g., MRI versus FDG-PET/CT) in patients with late-onset PTO.
In addition, surgical clinicians and advising imaging specialists often have a different starting point when additional imaging has to be chosen. The clinical situation plays a crucial role in the decision-making process, and nuclear imaging specialists and radiologists have the disadvantage of not being able to examine patients themselves. In this study, the provided clinical patient scenarios were the same for all participating medical specialists, but the difference in background knowledge might have lead to a different imaging strategy. More in general, failure from the surgeon to communicate the essential clinical details and specific diagnostic question with the advising imaging specialist can result in a less logical imaging advice. Another important factor that needs to be emphasised is that the process of treating fracture-related infections is time-consuming and costly. The best available data for this are derived from studies in patients with a prosthetic joint infection (PJI) and diabetic feet. In infected total hip arthroplasties (THAs), for example, the hospital length of stay has been shown to be 2.2 times longer, with associated overall costs 3.1 times higher compared to non-infected primary THA procedures [28, 29]. Non-medical costs resulting from the inability to work and help required from carers are not known. Any delay in diagnosis will obviously also delay the start of treatment and subsequently the recovery of a patient with PTO, hence overall costs will increase. It is known from other orthopaedic studies that, as a general rule, both patients and cost effectiveness benefit from clinical pathways and guidelines [30, 31]. There is thus a need for a lean and strict algorithm on diagnosing PTO. This will help clinicians choose the most effective diagnostic pathway to reduce the time needed to properly diagnose PTO and subsequently reduce medical costs by avoiding unnecessary imaging requests. Our results lead us to believe that in some cases, a leaner diagnostic pathway could have been followed. For example, for the two patients with a late clinical wound breakdown, therefore, a clear infective component (patients C and D), 44% (patient C, n = 152) and 43% (patient D, n = 149) of all participants would request further imaging, which is mainly indicated to diagnose or exclude an infection (a bone scan, WBC scintigraphy or FDG-PET). Especially for patient D (an obvious infection, no hardware in situ, and all operations performed three decades ago), one could argue that it is more logical to request an imaging modality that will aid in determining the surgical strategy and not only confirm the diagnosis of osteomyelitis. An MRI scan to visualise the extent of the osteomyelitis, and the presence or absence of cloacae, sinuses, subcortical abscesses, and intramedullary sequesters would in this case be a more logical option and is much cheaper and easier to perform than, for example, a WBC scintigraphy or FDG-PET. It is in this perspective interesting to note that an MRI for patient D was selected by only 26% (n = 90) of the responders.
The present study was designed to assess current practice on diagnostic imaging strategies for posttraumatic osteomyelitis in The Netherlands. The results will be used as a baseline for the development of a multicentre prospective trial to eventually provide and implement evidence-based national and international guidelines on diagnosing PTO. These guidelines will hopefully decrease the time to diagnosis in a cost-effective way.
Limitations of this study
This study might be limited due to bias resulting from under-coverage and non-response. Because it is likely that the responders will have an interest in—and, therefore, deeper knowledge of—PTO compared to non-responders, this study is prone to underestime the real variety in diagnostic imaging strategies. A second limitation might be the fact that this study was undertaken in only one European country. However, since no international guidelines on this topic exist, it is likely that the lacking consensus on how to diagnose PTO is an international omission and that our results can be extrapolated to other trauma orthopaedic societies.