Economic evaluations in fracture research an introduction with examples of foot fractures

Introduction: The incidence of foot fractures is increasing. These types of fractures represent the most expensive group of diagnoses in the emergency department. Next to this, the need for economic evaluation studies is growing fast. The aim of this article is to provide healthcare professionals with an introduction to economic evaluation studies in the field of foot fractures. Types of economic evaluation studies: Four types of economic evaluation studies exist: cost-minimization analysis (CMA), cost-benefit analysis (CBA), cost-effectiveness analysis (CEA), and cost-utility analysis (CUA). An economic evaluation study can be either trialor model-based. Cost Assessment: When assessing costs in an economic evaluation study, three steps need to be made: identification of costs, measurement of costs, and valuation of costs. Perspective of analysis: Two main perspectives exist in economic evaluation studies. When using a healthcare perspective, only the potential costs and benefits of an intervention for the healthcare sector are included. The societal perspective includes all potential costs, including societal costs. Synthesis of costs and effects and uncertainty analysis: The level of cost-effectiveness can be objectively expressed using the incremental cost-effectiveness ratio (ICER). This measure can be plotted in a costeffectiveness plane and can be compared with existing regional ceiling ratios. Conclusion: Although this article is not a guideline for economic evaluations, we do want to present five tips to consider when performing an economic evaluation. Firstly, when measuring resource use, consult the Database of Instruments for Resource Use Measurements (DIRUM) to find an appropriate instrument. Secondly, when measuring utility values, use the EuroQol questionnaire if possible. Thirdly, when setting up an economic evaluation study, consult the International Society for Pharmacoeconomics and Outcomes Research (ISPOR) database for the appropriate pharmacoeconomic guidelines. Fourthly, consult international guidelines to decide which study design is most appropriate. Finally, when performing an economic evaluation, consult a heath technology assessment (HTA) specialist from the start to ensure methodological quality. © 2022 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )


Introduction
Fractures of the lower extremities account for approximately one-third of all fractures [1] . Foot fractures such as calcaneal, talar, and midfoot fractures like Chopard and Lisfranc fractures, account for 16.7% of all lower limb fractures [1] . Moreover, foot and the number of economic evaluations being published in medical journals [ 7 , 8 , 10 ]. Although economic evaluation studies are becoming routine in healthcare, they are still quite uncommon in the field of foot fractures, so little is known about their economic impact in clinical practice [ 7 , 11 , 12 ]. However, the incidence of foot fractures is increasing, and so are the associated healthcare costs [7] . In addition, the government, insurers and other payers will be more willing to implement a particular intervention when its costeffectiveness has been clearly established [8] . Therefore, it is relevant to consider the economic aspects of treating these foot fractures.
Evaluation of the economic aspects is conducted in the form of Health Technology Assessment (HTA). HTA is a multidisciplinary, scientific assessment of technologies in healthcare that examines short-and long-term consequences of the use of a healthcare technology [9] . The purpose of HTA is to improve decision-making in order to provide an equitable, efficient, and high-quality healthcare system [9] . Economic evaluation as a field of research considers both the costs and consequences of alternative interventions and evaluates the choice between these treatments [ 13 , 14 ]. The findings can be used as a component in the assessment and improvement of the performance of existing healthcare systems [15] .
The need for more insight into economic aspects of the effectiveness of an intervention in medicine is illustrated by several trends. One of them is that developers of clinical practice guidelines are currently including the cost-effectiveness of interventions when developing a guideline [16] . As these guidelines are partly developed by medical specialists, they need to have sufficient knowledge and skills regarding the interpretation of the results of an economic evaluation. According to Majoie et al., only 40% of healthcare professionals throughout Europe think medical specialists are capable of this, while 96% considered specialists to be in need of more knowledge on cost-effective and sustainable care [17] . A clear understanding of the main principles of economic evaluation might therefore be advantageous for medical specialists. [ 11 , 18-21 ]. Next to this, being a physician requires a certain level of competency in different roles. Knowledge about performing economic evaluations and the interpretation of their roles is relevant within the 'health advocate' and 'academic' roles in the CANadian Medical Educational Directives for Specialists (CANMEDs) framework [22] . This framework consists of 7 competences that describe the different roles in which a medical professional needs to work. The framework was established in Canada, hence the name, but is now widely accepted to be an accurate representation of the different aspects of a medical professional.
Therefore, the aim of this review was to provide physicians with an introduction to these economic evaluations, with specific attention to (traumatic) foot fractures. The present paper first presents an overview of the current literature on economic evaluations in foot fractures. It then focuses on the unique aspects of an economic evaluation compared to an effectiveness study, by presenting a description of different study designs and types of economic evaluations, costs assessment, outcome measurements using Quality Adjusted Life Year(s) (QALY(s)), the perspective of analysis, the synthesis of costs and effects, and uncertainty analysis. The concluding section tries to provide tangible methods to understand the process underlying economic evaluation studies, and therefore lists five practical tips to consider when performing these studies.

Economic evaluation in foot fractures: state of affairs
In preparation for this article, a scoping search was performed using the electronic PubMed database to evaluate the available economic evidence in the field of foot fractures. The complete PubMed search, including both free terms and MEdical Subject Heading (MESH) terms, can be found in the Appendix. The Google Scholar, Cochrane, EMBASE, and Medline databases were searched for additional studies that were not found through the PubMed search. In addition, the reference lists of all fully screened studies were manually searched to identify additional eligible studies, this yielded no extra results. Year of publication for all screened studies ranged from 1973 to 2021. The search is performed by the first author which is a medical doctor and PhD-candidate in trauma surgery, the third author which is a medical student, and by an (anonymous) independent librarian from Maastricht University to prevent any selection bias.
Five studies could be considered appropriate (full) economic evaluations regarding patients with traumatic foot fractures. These were the studies by Brauer et al. [23] , Albright et al. [24] , Li et al. [25] , Clement et al. [26] , and Albin et al. [27] . The most relevant characteristics can be found summarized in Table 1 (See Table 1 ). Other studies were excluded because fewer than five participants were included, because they only focused on diagnostics, because participants were < 18 years, because they were written in a language other than English, or because they were not available after consulting a librarian and trying to reach the authors when the article was not available online. More information about the screening process and the study selection flow-chart can be found in the appendix ( Fig. 4 ).
Some important limitations were found regarding the methodological quality of the included studies. Generally, there were some issues with the contents of the economic evaluation, mostly relating to the different perspectives from which the analyses were conducted. Such a perspective defines which costs are included in the economic evaluation. The main perspectives are the healthcare perspective, which includes only the costs incurred and benefits obtained by the healthcare sector, and the societal perspective, which includes all costs incurred and benefits obtained by society in addition to the costs incurred and benefits obtained by the healthcare sector [ 8 , 20 , 21 ]. The results of studies from different perspectives are not comparable.
Alongside the differing perspectives, each study had some methodological errors. Most of these shortcomings were pointed out in the discussions of the articles in question. Brauer, et al. had some issues with the reliability of the measurement of societal costs. They did use data from a recent clinical trial as a base for their model which is recommendable. They did not collect their data on the costs prospectively in this reference trial which led to wide confidence intervals regarding cost measurement. [23] . Albright, et al. encountered a lack in empirical evidence considering the complications and other factors which could have led to errors in the model used to asses costs. Next to this they only included healthcare costs [24] . Li et al. mainly encountered problems relating to the smaller sample size and the possible single centre bias. Next to this, only the healthcare costs were included [25] . Clement et al. use the societal perspective which is the best possible option, however this also limited impact of the study, since the societal costs (e.g. lost time at work) were difficult to estimate. Furthermore they also encountered a lack of data on the cost of treatment, therefore, the model might not be very accurate [26] . Albin et al. also encountered a lack in data as a baseline for their model [27] .
Overall, none of the selected foot fracture studies were found to present empirical economic evidence or high-quality economic evaluation research concerning the treatment of foot fractures. This was mainly a result of a lack of data that could be used as baseline for the models used in model based studies [ 24 , 26 , 27 ]. The model based study by Brauer et al. based their data on a recent clinical trial, which is more reliable. However, no prospective data on costs was collected in this trial [23] . The first trial-based study had a relatively small sample size and was open to single centre bias [25] . The studies with a societal perspective faced issues with the measurement of societal costs [ 23 , 26 , 27 ]. These limitations could  be avoided by setting up a prospective RCT with an adequate sample size and attaching a economic evaluation to this trial. This way the prospective nature of the trial enables reliable measurement of all costs.

Study design; trial-based versus model-based
There are two basic approaches to economic evaluation, namely trial-based and model-based. In a trial-based economic evaluation, economic data is collected alongside a single clinical study, usually a randomized controlled trial (RCT) [ 8 , 21 ]. In general, this means the trial should collect data regarding costs and outcomes, for example quality-adjusted life years (QALYs) [8] . A QALY measures effects in terms of quality of life (utilities) and survival years (lifeyears gained) [28][29][30] .
A model-based economic evaluation synthesizes existing knowledge and evidence on different treatment strategies in a validated model and predicts the cost-effectiveness of treatments [31] . Model-based economic evaluations are often used when long term evidence is important but not available. These model-based studies should be based on data from all relevant studies with a satisfactory scientific quality. A model is a simplified version of the real-world situation, used to describe essential elements of a real situation, for example, the economic implications of using a specific surgery procedure in Lisfranc fracture dislocations [24] .
Model-based economic evaluations bring all clinical, cost, and quality-of-life data together in one model using epidemiological or decision analyses. This enables the results to be generalized in terms of a larger population, and eventually lifetime costs and outcomes can be estimated. For patients with foot fractures, the injury is often chronic, and therefore long-term outcome costs are essential [ 24 , 27 , 32 , 33 ].

Types of economic evaluation studies
There are four main types of full economic evaluation studies, and the identification of consequences determines which type of full economic evaluation study should be considered: costminimization analysis (CMA), cost-benefit analysis (CBA), costeffectiveness analysis (CEA), or cost-utility analysis (CUA) [20] . A flow chart for several categories of economic evaluation studies visualizes the differences between them ( Fig. 1 ). The gray-shaded boxes in this flow chart are considered full economic evaluation studies.
A subdivision between partial and full economic evaluation can easily be made using three different questions: "Are the costs evaluated in terms of money?", "Are both costs (inputs) and consequences (outputs) of alternatives examined?", and "Is there a comparison of two or more alternatives?" [34] . In economic evaluation studies, the experimental intervention should be compared with a control intervention, preferably involving "standard practice" or the best available alternative [34] . For example, in Lisfranc fractures this could mean primary arthrodesis versus open reduction and internal fixation.
CEA and CUA would appear to be more appropriate methods to use than other full economic evaluations, since these two types measure the effects in non-monetary units and generic outcomes such as QALYs. CEA measures the consequences of programs in terms of the most appropriate non-monetary effects of physical units. For example, the outcome measures used in CEA studies of foot fractures mainly include natural outcomes like healthcare consumption [7] . Another example of a possible outcome is provided by the CEA model of the Centre for Disease Control (CDC), this model shows averted complications can also be used as a outcome value [35] . The most important argument for these clinical measures is the availability of the measurements and their interpretation. A major limitation of CEA with its disease-specific outcome is that it does not permit comparisons with interventions evaluated for other diseases. For example, a foot fracture CEA is not usable for other traumatic fractures.
In CUA, the consequences are measured in terms of preferences of patients for specific health states or specific health outcomes. These consequences are adjusted by health state preference scores or utility weights. The most common measure of consequences in a CUA is the QALY [ 21 , 36 ].
CMA is an analysis in which the effects of several alternative treatments have no differing value [34] . Due to its methodological limitations, CMA is considered outdated within HTA and is not commonly used anymore [37] . It has therefore lost its status as a gold standard [37] . In a CBA, effects are measured in monetary terms. This will often not be possible in healthcare evaluation because effects that occur as a result of treatment are often not measurable in monetary terms [38] . For these reasons it is generally recommended to perform a CEA and/or a CUA to assess the economic value of interventions in general, including those for foot fractures [39] .

Quality adjusted life year
QALY is the one of the most frequently used outcome measures in economic evaluation studies. To many, however, the concept of QALY might seem abstract, which may make the interpretation of its value difficult.
Calculating the number of QALYs requires two inputs. Firstly, the quality of life, expressed in utilities. This value lies between zero or 0 (death) and one or 1 (perfect health). Secondly the amount of time lived at this quality of life level. This value is usually expressed in years. QALY is calculated by multiplying these two input values [ 29 , 30 ]. Therefore, one QALY can mean one extra year lived at maximum quality or two extra years lived at a quality of 0.5.
Since the number of years lived is an objective value, the difficulty in measuring QALY occurs when measuring the utilities. This value can be measured using multiple calculations and estimates [40] . In addition, multiple questionnaires are available to assess quality of life. In practice, most guidelines on economic evaluation recommend using the EuroQoL EQ-5D-5 L (EuroQol 5-Dimensions 5-Levels) [41] . This is a self-administered questionnaire, which contains five dimensions of health-related quality of life, namely mobility, self-care, daily activities, pain/discomfort, and depression/anxiety. Each dimension can be rated at five levels: no problems (5)  summed into a health state. Utility values can be calculated for these health states, using preferences elicited from the general population, which are country-specific [ 41 , 42 ]. The EuroQol EQ-5D-5 L has been validated for use in limb injury and has also been used in foot fracture research [ 43 , 44 ].

Cost assessment
As stated above, all appropriate (full) economic evaluations should assess the costs of the intervention as well as the control treatment. Assessing cost is a multifactorial process and requires some thought. When assessing costs in economic evaluation studies, there are three aspects one needs to consider: Which resource uses are relevant to identify in the context of the disease and the intervention? How can these resource uses be measured? What value (price) should we attach to these resource uses? A more detailed description of these questions is presented below.

Identification of resource uses
All resource uses associated with a particular intervention in a particular disease must be identified. In economic evaluation, three types of costs are generally identified: healthcare costs, patient and family costs, and costs outside the healthcare sector. Healthcare costs include all resource uses in the healthcare sector, including the costs of the specific intervention, as well as all follow-up costs of the treatment of a patient with a fracture of the foot [34] . These costs consist of all medical costs that can be included, for example operative, postoperative (for example hospitalization for recovery), non-operative (for example pre-operative consultations) and medication costs [27] . A few examples from the long list of possible costs are: medication costs, consultations with general practitioners (GPs), medical specialists, occupational physicians, therapists (physical therapists, dieticians, occupational therapists, speech therapists, homeopaths and psychologists), and social workers, as well as emergency department visits, ambulance transportation, homecare (domestic help, help with daily activities, and nursing), admittance to rehabilitation centers and admittance to assisted living facilities. Patient and family costs include all out-of-pocket expenses, such as travel costs, informal care etc. Some resource use falls outside the healthcare sector, for example loss of productivity due to a patient not being able to work during hospitalization [34] . In foot fractures, patients may be unable to walk or stand, resulting in further productivity losses from paid and unpaid work.

Measurement of resource use
To measure the actual use of resources, data can be obtained using combined sources (registrations by professionals and cost questionnaires). Measurements of resources used that relate to the interventions are often based on the time all professionals record as having been spent on the treatment. All use of resources in addition to the intervention can be measured by means of a resource use questionnaire (cost questionnaire), in which volumes of resource utilization are continuously recorded during the followup period. For each study, a cost questionnaire is developed which is especially designed for the study population based on existing questionnaires [45] , and which measures all relevant identified cost aspects. The Database of Instruments for Resource Use Measurements (DIRUM) provides a comprehensive database on appropriate instruments to measure resource use [46] .
A reference case is a set of methodological choices that is recommended by HTA organizations. It provides researchers with a reference regarding the methods for their own economic evaluation studies [47] .
When performing economic evaluation, reference case analyses must be done regardless of the perspective [35] . According to the second panel on Cost-Effectiveness in Health and Medicine these reference case analyses should report their outcomes in terms of QALYs [8] .

Valuation of resources
After identifying the costs and measuring their magnitude, the monetary value of these costs needs to be determined. For this, understanding of the concept of opportunity costs is needed. This concept is built on the idea that money can only be spent once, on one thing. Therefore, the real value of the costs associated with a particular intervention is equal to the value of the potential benefits associated with the best alternative use of the resources. Naturally, once resources are allocated to the intervention, the potential benefits from the next best alternative are no longer an option [ 34 , 48 ].
Calculating these opportunity costs in the field of healthcare, e.g. in foot fracture research, is impossible, partly because the best available alternative is not clearly defined [24] . Often, guideline costs are used to approximate the value of costs in healthcare, because the opportunity costs are impossible to determine accurately. Many countries have national guidelines for approximating these numbers. [49] Perspective of analysis The specific type of economic evaluation partly depends on the perspective from which the economic evaluation is being considered and examined [ 20 , 21 ]. Therefore, the perspective of analysis is essential when performing or interpreting an economic evaluation [ 15 , 50 ]. There are different types of perspectives in economic evaluation, the most relevant and most frequently used ones being the societal and healthcare perspectives.

Societal perspective
The societal perspective would appear to be the main perspective from which to consider an economic evaluation [ 36 , 50 ]. The societal perspective takes all potential costs into account, in other words not only healthcare costs but also costs like transportation, productivity and time lost by the patient and their caregiver, and other non-healthcare costs. This way, researchers can illustrate the impact of the intervention on society [51] . Nevertheless, many published cost-effectiveness analyses have used other perspectives than the societal to define the economic evaluation [36] . The societal perspective is a viewpoint for conducting a cost-effectiveness analysis that incorporates all costs and health effects, regardless of who incurs the costs and who experiences the effects [36] .

Healthcare perspective
The healthcare perspective only includes the potential costs and benefits of an intervention for the healthcare sector. It is a viewpoint for conducting a CEA that only includes formal healthcare sector (medical) costs borne by third-party payers and paid outof-pocket by patients [8] . These third-party and out-of-pocket costs include the current and future costs, related and unrelated to the condition under consideration [ 8 , 50 ]. Results of healthcare perspective studies should be summarized in the conventional form as an incremental cost-effectiveness ratio (ICER) [ 8 , 21 ]. Net monetary benefit or net health benefit, a linear combination of costs and effects expressed in currency, may also be reported in this perspective [8] . Examples of cost-effectiveness ratios in foot fractures are the cost per patient of reaching the minimal clinically important improvement in the quality of life, and the costs per workday gained. Although this perspective is less commonly used, it is standard practice in the United Kingdom [48] .

Relevance of perspectives
Standardizing the methods and components within a perspective is intended to enhance consistency and comparability across economic evaluation studies [8] . When using economic evaluation in foot fracture management, one should be aware of the perspective used, as the results of the study will differ depending on this analytic perspective.
Only the study performed by Albright et al. met the recommendation criteria, as reported by the second panel [ 8 , 24 ]. The study by Albin et al. reported the results from a healthcare and societal perspective [27] . The advantage of adopting this broader perspective is that the data can be disaggregated, and the analysis is conducted from several viewpoints, which is strongly recommended [ 8 , 36 ]. Furthermore, differentiating between the healthcare sector perspective and the societal perspective will provide more clarity to consumers of cost-effectiveness analyses [8] .
Analysts should be transparent about how they conducted the analyses and convey how the results change with alternative assumptions. Sensitivity analysis should describe the assumptions to which the results are sensitive for different perspectives [8] . None of the published foot fracture studies fulfilled all of these criteria.

Synthesis of costs and effects and uncertainty analysis
The ICER is determined based on incremental costs and effects in an intervention group and a control group. Incremental costs can be defined as the mean difference between different treatment groups regarding the total costs. Incremental effectiveness can be defined as the mean difference in outcome measurements between the different treatment options. The cost-effectiveness ratio is expressed in terms of costs per outcome rate, while the cost-utility ratio focuses on the net cost per QALY gained.
The ICER is calculated as follows. ICER = (Ci -Cc) / (Ei -Ec), where Ci is the annual total cost in the intervention group, Cc is the annual total cost in the control group, Ei is the effects at the last follow-up for the intervention group and Ec is the effect at the last follow-up for the control group.  For example, if one wants to determinate the ICER for open reduction and internal fixation (ORIF) in traumatic foot fractures, with primary arthrodesis (PA) as the control treatment, one first has to know the cost per treatment of both ORIF and PA. Then one would have to know how many QALYs are gained in each treatment. In this example, Let us assume that ORIF has an annual cost of €9836 per treatment, and PA has an annual cost of €14,375 per treatment. ORIF produces a gain of 0.7 QALY per treatment, while PA produces a gain of 0.9 QALY per treatment, ( Table 2 ).

ARTICLE IN PRESS
In this case the ICER will be: (9836 -14 375) / (0.7 -0.9) = €22,560/QALY. This figure provides policymakers with a concrete value to assess and compare interventions.
The robustness of the ICER is checked by non-parametric bootstrapping. Bootstrapping is a statistical resampling method that uses random sampling with replacement to assess the accuracy of the given sampling estimates [51] . Bootstrap simulations are also conducted to quantify the uncertainty around the ICER, yielding information about the joint distribution of cost and effect differences.

Cost-effectiveness plane
When applying economic evaluation studies in practical decision-making, the cost-effectiveness ratio is plotted in a costeffectiveness plane, in which the vertical line reflects the difference in costs between alternative interventions and the horizontal line reflects the difference in effectiveness ( Fig. 2 ). In this costeffectiveness plane, there are 3 possibilities. Firstly, an intervention can be expensive and not very effective, in which case the intervention will probably be discarded. Secondly, an intervention can be inexpensive and very effective, in which case the intervention will probably be implemented. Finally, an intervention can be either expensive and very effective or inexpensive and not very effective, in which case a clear cut-off point is needed to decide on implementing or discarding the intervention. This cut-off point depends on the maximum amount of money that society is prepared to pay for a particular gain in effectiveness, which is called the ceiling ratio. Therefore, the bootstrapped ICERs are also depicted in a cost-effectiveness acceptability curve, showing the probability that the intervention is cost-effective when using a range of ceiling ratios ( Fig. 3 ). In the Netherlands, ceiling ratios of € 20,0 0 0, € 50,0 0 0 and € 80,0 0 0 per QALY are used, depending on the burden of disease [ 52 , 53 ] . Similar limits are used in other countries. For example, the United Kingdom sets a limit of £30,0 0 0 per QALY for regular care and £50,0 0 0 per QALY for "end-of-life" care [54] . By contrast, no similar limit officially exists in Germany [55] .
If the example presented before took place in the Netherlands, its ICER would not be sufficiently low ( €22,560/QALY) for the intervention to be considered cost-effective in every scenario, since variable ceiling ratios exist, including one of €20,0 0 0/QALY.

Discussion
Despite the steady increase in the number of economic evaluation studies conducted and the rising demand for these types of studies from policymakers, we only found five full economic evaluation studies regarding traumatic foot fractures. The lack of economic evidence in this area of medicine indicates that there is a need for more attention to be given to economic evaluation. Moreover, all five identified studies were methodologically flawed. The present article partially explored the aspects of these methods which could be improved.
The lack of reliable data in the field of economic evaluation fractures could be explained by the lack of reliable literature to base the models on. Since model based studies are the most common design in this field of research, this problem is significant. Furthermore, both key reporting guidelines provided by the network for Enhancing the QUAlity and Transparency Of health Research (EQUATOR) state the data on which these models are based is a very important part of a well-executed economic evaluation [ 8 , 56 , 57 ]. In the field of for example osteoporosis, economic evaluation studies are more abundant than in the field of foot fractures. In this field sufficient evidence is present on costs measurement and therefore constructing a reliable model is not a limiting issue [58] . In the field of proximal humeral fractures trial based studies with larger sample sizes have proved to be a reliable way of conducting an economic evaluation [59] .
Conducting economic evaluation studies will lead to improved clinical decision-making [35] . This is especially true for economic evaluation studies that are performed from a societal perspective, since those studies include every aspect of the costs associated with a particular intervention. These studies can help shape the future of decision-making in the management of traumatic foot fractures in case there is no preference regarding (functional) outcome parameters, as the cost-effectiveness of a treatment may then be the deciding factor in determining which treatment is superior.
To add to the available empirical evidence in the field of foot fracture research, there is a need for randomized controlled tri-als focusing on the cost-effectiveness, including healthcare, societal and patient costs of different surgical treatments for foot fractures. These costs should be measured using the Institute for Medical Technology Assessment (iMTA) Medical Consumption Questionnaire and the iMTA Productivity Cost Questionnaire, both of which are internationally recognized questionnaires to measure costs in economic evaluations [ 60 , 61 ]. Quality of life can be measured using the EQ-5D [40] . At present, we are performing an RCT measuring the healthcare, patient, and societal costs of Lisfranc fractures.
We consider it very important to provide surgeons and other healthcare providers in the field of traumatic foot fractures with sufficient knowledge about economic evaluation studies to understand their results and the decision-making associated with these results.
Although this article offers no guideline to performing economic evaluation studies, it can serve as a source of basic information on the subject of economic evaluation studies. To add some practical value to this article, we present five tips that can be considered when performing economic evaluation studies in the field of foot fractures. Firstly, when measuring resource use, consult the Database of Instruments for Resource Use Measurements (DIRUM) to find an appropriate instrument [46] . Secondly, when measuring utility values, use the EuroQol questionnaire if possible [41] . Thirdly, when setting up an economic evaluation study, consult the International Society for Pharmacoeconomics and Outcomes Research (ISPOR) database for the appropriate pharmacoeconomic guideline for your country [39] . Fourthly, consult international guidelines to decide which study design is most appropriate. Finally, when performing an economic evaluation, consult an HTA specialist from the start to ensure methodological quality.

Conclusion
In conclusion, we have found that the current literature on economic evaluation studies in fracture research with emphasis on foot fractures is not very extensive and can be improved methodologically. Furthermore, the perspectives of analysis are vitally important to understanding and implementing the results of economic evaluation studies. Finally we find it very important to make this field of research accessible for healthcare providers. We have therefore added 5 tips when performing economic evaluations to our discussion.

Declaration of Competing Interest
All authors declare that they have no conflicts of interest. )) OR (Cost-Effectiveness)) OR (Cost-Effectiveness Analysis)) OR (Cost Comparison)) OR (Costs)) OR (Cost of disease)) OR (Cost Utility analysis)).
Articles were included if they were full economic evaluation studies on surgical management of foot fractures. Studies were excluded when a cost comparison was presented instead of a full economic evaluation, when fewer than 5 participants were included, when they only focused on diagnostics, when participants were < 18 years, when they were written in a language other than English, or when they were not available online or after consulting a librarian and (when possible) trying to reach the authors. Next to these exclusion criteria, the search was not specific for foot fractures and also contained many results for ankle injuries. The search was constructed this way to ensure no possible articles were missed. The articles describing ankle injuries were also excluded.
The selection process of the articles included in this article under the header 'state of affairs' consis ted of a main search in the PubMed database using the above mentioned search strategy. This yielded 130 results which were screened by abstract. Next to this Google Scholar, EMBASE, Medline and Cochrane databases were screened however they did not yield any extra results. The reference lists of the selected articles were screened however they yielded no extra results. In total all 130 results were screened by abstract (if available), the publication years ranged from 1973 to 2021. Of these articles 36 described ankle injuries and were excluded. Furthermore 30 articles made a cost comparison however they did not present a full economic evaluation study. 24 articles only described single interventions (surgical and non-surgical). 14 Articles only described the injury. 8 articles were systematic reviews. 5 articles were not available online nor were they available via the library, all of these dated from before 1995. 4 articles described a study protocol. 4 articles contained economic evaluation of diagnostics. 4 articles described all fractures of the lower extremities. And finally, 1 article was an economic evaluation on non-surgical therapy. 5 studies were screened for their full text, all 5 of these studies were included in this article. The selection process has been visualized in Fig. 4 (See Fig. 4 ).
The search was conducted on the 2nd of November 2021. The search was constructed by The authors NvdB (PhD-candidate at the

ARTICLE IN PRESS
JID: JINJ [m5G; January 13, 2022;16:27 ] department of trauma surgery MUMC + ) and AvdH (5th year medical student at the University of Maastricht) with the help from the library of the University of Maastricht. In case of disagreement author SE could be included however this was not necessary in practice.