JMIR MHEALTH AND UHEALTHDittrich et alOriginal PaperA Possible Mobile Health Solution in Orthopedics and TraumaSurgery: Development Protocol and User Evaluation of the AnkleJoint AppFlorian Dittrich1, Dr med; David Alexander Back2, Priv-Doz; Anna Katharina Harren3, Dr med; Marcus Jäger4,Univ-Prof; Stefan Landgraeber1, Univ-Prof; Felix Reinecke5; Sascha Beck1,6, Dr med1Department for Orthopaedics and Orthopaedic Surgery, Saarland University Medical Center and Saarland University Faculty of Medicine, Homburg,Germany2Clinic of Traumatology and Orthopedics, Bundeswehr Hospital Berlin, Berlin, Germany3Department of Plastic, Reconstructive & Aesthetic Surgery, Specialized Clinic Hornheide, Münster, Germany4Department of Orthopaedics, Trauma and Recontructive Surgery, St. Marien Hospital Mülheim and Chair of Orthopaedics and Trauma Surgery,University of Duisburg-Essen, Essen, Germany5Clinic of Trauma, Hand and Reconstructive Surgery, University Hospital Essen, Essen, Germany6Sportsclinic Hellersen, Lüdenscheid, GermanyCorresponding Author:Florian Dittrich, Dr medDepartment for Orthopaedics and Orthopaedic SurgerySaarland University Medical Center and Saarland University Faculty of MedicineKirrbergerstr. 100Building 37-38HomburgGermanyPhone: 49 68411624520Email: [email protected]: Ankle sprains are one of the most frequent sports injuries. With respect to the high prevalence of ankle ligamentinjuries and patients’ young age, optimizing treatment and rehabilitation is mandatory to prevent future complications such aschronic ankle instability or osteoarthritis.Objective: In modern times, an increasing amount of smartphone usage in patient care is evident. Studies investigating mobilehealth (mHealth)–based rehabilitation programs after ankle sprains are rare. The aim of this study was to expose any issues presentin the development process of a medical app as well as associated risks and chances.Methods: The development process of the Ankle Joint App was defined in chronological order using a protocol. The app’squality was evaluated using the (user) German Mobile App Rating Scale (MARS-G) by voluntary foot and ankle surgeons (n 20)and voluntary athletes (n 20).Results: A multidisciplinary development team built a hybrid app with a corresponding backend structure. The app’s contentprovides actual medical literature, training videos, and a log function. Excellent interrater reliability (interrater reliability 0.92;95% CI 0.86-0.96) was obtained. The mean overall score for the Ankle Joint App was 4.4 (SD 0.5). The mean subjective qualityscores were 3.6 (surgeons: SD 0.7) and 3.8 (athletes: SD 0.5). Behavioral change had mean scores of 4.1 (surgeons: SD 0.7) and4.3 (athletes: SD 0.7). The medical gain value, rated by the surgeons only, was 3.9 (SD 0.6).Conclusions: The data obtained demonstrate that mHealth-based rehabilitation programs might be a useful tool for patienteducation and collection of personal data. The achieved (user) MARS-G scores support a high quality of the tested app. Medicalapp development with an a priori defined target group and a precisely intended purpose, in a multidisciplinary team, is highlypromising. Follow-up studies are required to obtain funded evidence for the ankle joints app’s effects on economical and medicalaspects in comparison with established nondigital therapy paths.(JMIR Mhealth Uhealth 2020;8(2):e16403) doi: /XSL FORenderXJMIR Mhealth Uhealth 2020 vol. 8 iss. 2 e16403 p. 1(page number not for citation purposes)

JMIR MHEALTH AND UHEALTHDittrich et alKEYWORDSsmartphone; ankle sprain; rehabilitation; self-care; mHealth; mobile phoneIntroductionBackgroundAn ankle sprain is one of the most frequent injuries, with anincidence of 1:10,000 individuals per day in amateur andhigh-performance sports in the United States [1]. With respectto the high prevalence of ankle ligament injuries and patients’young age, optimizing aftercare and rehabilitation is mandatory[2]. Moreover, the economic burden of ankle sprains isenormous [3]. High medical, physiotherapeutic, and lostproductivity costs burden health care systems and create theneed for new, efficient diagnostic and therapeutic solutions [4].To prevent long-term complications, complex ligament injuriesand recurrent ankle sprains with progression to chronic ankleinstability (CAI) have to be recognized. The development ofankle osteoarthritis (OA) as a long-term consequence of CAIwas first shown by Harrington et al [5] in 1979. Following anankle ligament injury, posttraumatic muscular insufficiency[6,7] and ankle OA were observed in 13% of the cases [8].Therefore, the adequate and consequent treatment of an anklesprain might prevent CAI and OA.Nowadays, early functional treatment is considered the goldstandard for the lateral ligament lesion of the ankle [2,9]. Thelatest national guideline published by the German OrthopedicFoot and Ankle Society (Deutsche Assoziation für Fuß undSprunggelenk eV, DAF) also recommends a conservativeapproach to acute ligament tears of the lateral ankle joint [10].In times of digitalization and emerging technologies,smartphones are regularly used to accomplish everyday tasks,such as Web-based banking and communication via messengeror email, and penetrate rapidly into more and more areas of life[11]. The portability and omnipresent accessibility ofsmartphones enable usage anywhere and anytime [12]. Ingeneral, the growing implementation of smartphones as atransfer media in medical context is evident [13].It has already been shown that the patients’ acceptance is givenfor collecting personalized health-relevant data via softwareapps, to share these with their peers or the medical staff [14].Moreover, mobile short message service text messages and appscan have a positive impact on the posttraumatic outcome byshowing increased adherence to medications and protocols,improved clinic attendance, and decreased readmission ratesand emergency room visits [15].However, the implementation and use of mobile health(mHealth) in medical care, especially in the fields of orthopedicsand trauma surgery, can still be regarded to be in an early stage.So far, only 13 serious medical apps in orthopedics and traumasurgery have been identified for regular use in outpatient andinpatient medical care in German-speaking countries [16]. In asurvey among German orthopedic and trauma surgeons, theAnkle Joint App (Sprunggelenks-App, Mediploy GmbH,Langenfeld, Germany) was shown to be frequently chosen,although the medical usage rate was still very low at 2.3% [17]. FORenderXStudies investigating mHealth-based diagnostics [18] orrehabilitation programs after lateral ankle sprains already exist,for example, in the Netherlands (app: Strengthen your Ankle)[19], where a positive influence on medical and economicaspects could be demonstrated [20-22]. To date, the applicationof posttraumatic mHealth solutions after ankle sprains has notbeen investigated in Germany.ObjectiveTo address this gap, this work outlines the methodology todevelop and design an app for patient education as well asprevention and identification of CAI after ankle sprains (AnkleJoint App). The publication of an app development processmight be the basis for future mHealth solutions to improvepatient care.The app’s content, usability, and styling were evaluated byGerman orthopedic or trauma surgeons and athletes whosuffered from ankle sprain.MethodsDevelopment ProtocolBasic App ConceptionA multidisciplinary team was involved in the development ofthe ankle joint app. The team members comprised 2 orthopedicand trauma surgeons (FD and SB), a physiotherapist, a lawyer,and a software and Web developer. Before programming theapp, some general aspects regarding the software structure,design, and content had to be considered. At an early stage, thetarget group and the intended purpose needed to be definedprecisely to clarify whether the app had to be defined as amedical device and therefore had to be regulated by medicalproducts law [23].Technical SpecificationsThe ankle joint app was developed using React Native(Facebook Inc) technology. React Native is a Javascript-basedframework for software developers, building cross-platformmobile apps for Android or iOS devices. The framework featuresbuilt-in components and application programming interfaces,which are essential for developing innovative and user-friendlymobile apps [24].The backend server runs on a Web app based on the HypertextPreprocessor framework Symfony and meets actual softwaresecurity guidelines. Any data exchange between the backendserver and the app runs via Secure Sockets Layer securedconnection. All server structures are located in Germany.Patient-related data remain strictly on the mobile device.Texts and VideosThe ankle joint app is based on the latest national guidelinespublished by the German Orthopedic Foot and Ankle Society(DAF) and related medical literature. The content is written inGerman. All relevant references are stored in the app and arehyperlinked to the primary source to facilitate search for theJMIR Mhealth Uhealth 2020 vol. 8 iss. 2 e16403 p. 2(page number not for citation purposes)

JMIR MHEALTH AND UHEALTHuser. Special efforts have been made to ensure that theinformation communicated is short, clear, and easy tounderstand. To explain medical terms comprehensibly, aglossary function has been integrated to avoid overloaded maintext pages. By answering frequently asked questions, personaldata are collected and made available to the user at some keypoints. Thus, the content adapts to the individual healing processconstantly.With the cooperation of a physiotherapist and considering thecurrent research data, a training program was created, whichDittrich et alcan be carried out without special equipment. In addition togiving some general information, for example, the PRICE-rule(P protection, R rest, I ice, C compression, and E elevation)or the activation of the muscle-vein pump in the acute stage,patients are also provided with short video clips in the laterstages (Figure 1). A total of 15 successive built-up exerciseswere made available to patients via the app. A special focus inthis training circle was placed on early functional mobilizationand proprioceptive training to prevent CAI.Figure 1. App screen view: (a) timeline-based aftercare plan, (b) information, and (c) training videos.Patient-Generated Data and Log FunctionInitially, to start the timeline, the timepoint of the injury has tobe defined. In addition, the user is asked to evaluate whether itwas the first or the second event of an ankle sprain. Moreover,the kind of trauma and prescribed aids are requested. At regularintervals, patients are asked questions via push messages abouttheir current level of pain, using the visual analog scale; feelingof instability; and load-bearing capacity. The collectedpatient-related data are presented to the patient in anunderstandable graphical form in the diary function (Figure 2). FORenderXGerman Cumberland AnkleThe Cumberland Ankle Instability Tool (CAIT) was developedfor measuring the severity of functional ankle instability [25].Using a well-established 9-item 30-point scale, the CAIT showsan adequate correlation to performance tests. It is a valid andreliable instrument for assessing CAI [26-28]. The minimaldetectable change, as well as the minimal clinical importantdifference, lies at 3 points [29]. We assessed the status of CAIusing the validated German CAIT in a digital form for the firsttime [30,31]. The CAIT was surveyed on day 56 after trauma.A score of 25 indicates CAI, and the app user is informed thatadditional diagnostics are recommended [32].JMIR Mhealth Uhealth 2020 vol. 8 iss. 2 e16403 p. 3(page number not for citation purposes)

JMIR MHEALTH AND UHEALTHDittrich et alFigure 2. App screen view: (a) collection of patient-related data and (b) log function of patient-related data.Styling, Design, and TestingSpecial attention was paid to the development of an intuitiveand user-friendly interface. To allow elderly patients to use theapp, an onboarding feature was established to explain the mainfunctions and interactions. Milestones in rehabilitation werepresented graphically in a timeline to ensure clarity for patientsabout the progress of their rehabilitation. Information regardingthe rehabilitation process was structured logically and linkedto icons with a recognition factor.After the app had been developed, an alpha test was carried outby the development team using the software TestFlight (AppleInc). The following beta test was performed on persons whohad already undergone an ankle distortion trauma. Sometechnical, content-related, and interactional improvements weremade as a consequence to the test feedback under controlledconditions.App Quality TestingStudy Design and SampleThe app was evaluated by 20 German orthopedic and traumasurgeons with a special interest in foot and ankle surgery aswell as 20 athletes. All the physicians and athletes includedwere familiar with smartphone devices and used apps on a dailybasis. The involved athletes already sustained an acute anklesprain in their past sporting career. The study was conductedbetween June 2019 and August 2019. The link for the digitalquestionnaire on a Google Docs (Google LLC) platform wassent to the participants by email or Quick Response codescanning. The email addresses of the physicians were generatedmanually via the home pages of clinics or via established emaildistribution lists. The athletes were screened in local badminton FORenderXor boxing clubs (FC Langenfeld, VFL Bochum, and Lannamartial arts Bochum).German Mobile App Rating ScaleThe MARS rating is a well-established assessment scale formedical app quality. It was developed for professionals, and itincludes the sections classification, objective app quality,subjective app quality, and a modifiable app-specific section.MARS items are scored using a 5-point Likert scale(1 inadequate, 2 poor, 3 acceptable, 4 good, and 5 excellent).The objective app quality section includes 19 items divided into4 subscales—engagement, functionality, esthetics, andinformation quality—and a separate subjective app qualitysection. The subjective app quality section contains four itemsevaluating the user’s overall satisfaction.Calculating the mean scores of the engagement, functionality,esthetics, and information quality objective subscales, as wellas an overall mean app quality, total score is how the MARS isscored. Mean scores instead of total scores are used becauseitems can be rated as not applicable. The subjective qualityitems can be scored separately as a mean subjective qualityscore [33].The English MARS version’s sections were extended in theMARS-G by an additional section focusing on the medical gainof an app. The 5 subscales and the overall score determine theapp’s quality [34]. All surgeons watched the associatedMARS-G instructional video on how to use the MARS-G scalebefore rating in case of doubt [35].Data AnalysisThe analog (user) MARS-G was converted into a digitalquestionnaire on a Google Docs platform (Google LLC). DataJMIR Mhealth Uhealth 2020 vol. 8 iss. 2 e16403 p. 4(page number not for citation purposes)

JMIR MHEALTH AND UHEALTHwere saved and then transferred into an Excel table (MicrosoftCorp). Descriptive statistics were calculated for all items. Theintraclass correlation coefficient (ICC) was calculated amongthe reviewers. We selected an individual absolute agreementICC (AA-ICC) for a two-way mixed model on the basis of ICCguidelines by Shrout and Fleiss [36]. All statistical analyseswere conducted using SPSS (version 25, IBM Corp).ResultsParticipantsA total of 20 foot and ankle surgeons as well as 20 athletes whosuffered an ankle sprain took part in the app rating, which isequivalent to a response rate of 65% (20/31) for the surgeonsand 44% (20/46) for the athletes. Excellent interrater reliabilities(two-way mixed model AA-ICC 0.92; 95% CI 0.86-0.96 forDittrich et alsurgeons and athletes) were shown following the guidelines forICC interpretation established by Koo et al [37]. The surgeons’group comprised 20% (4/20) Android and 80% (16/20) iOSusers, and the athletes’ group comprised 59% (10/17) Androidand 41% (7/17) iOS users.German Mobile App Rating ScaleThe mean overall score for the Ankle Joint App was 4.4 (SD0.5), rated by both surgeons and athletes. It was derived fromthe mean scores on app functionality, engagement, esthetics,and information quality (Figure 3). The mean subjective qualityscores were 3.6 (surgeons: SD 0.7) and 3.8 (athletes: SD 0.5).The section behavioral change, which included an assessmentof the perceived impacts on disease-related knowledge, attitude,awareness, and behavior, had mean scores of 4.1 (surgeons: SD0.7) and 4.3 (athletes: SD 0.7). The medical gain, rated by thesurgeons only, was 3.9 (SD 0.6; Table 1, Figure 3).Figure 3. Mean scores of the (user) German Mobile App Rating Scale for the Ankle Joint App (surgeons: n 20 and athletes: n 20). FORenderXJMIR Mhealth Uhealth 2020 vol. 8 iss. 2 e16403 p. 5(page number not for citation purposes)

JMIR MHEALTH AND UHEALTHDittrich et alTable 1. Detailed results of the (user) German Mobile App Rating Scale.SubscaleMARS-Ga surgeonsuMARS-Gb athletesMinimumMaximumMean (SD)MinimumMaximumMean (SD)Entertainment354.4 (0.9)354.1 (0.7)Interest354.3 (0.9)254.4 (0.9)Customization253.8 (0.8)253.6 (0.9)Interactivity354.2 (0.7)254.3 (0.9)Target group454.6 (0.5)454.6 (0.5)Performance455.0 (0.2)354.8 (0.6)Usability454.6 (0.5)354.6 (0.6)Navigation454.6 (0.5)354.5 (0.7)Gestural design454.5 (0.5)454.5 (0.5)Layout354.4 (0.8)354.5 (0.6)Graphics454.6 (0.5)354.5 (0.6)Visual appeal354.1 (0.7)354.3 (0.7)Accuracy of app description (in app store)354.8 (0.5)—c——Goals354.3 (0.6)———Quality of information354.5 (0.8)454.7 (0.5)Quantity of information454.8 (0.4)354.9 (0.5)Visual information454.3 (0.5)354.5 (0.6)Credibility354.0 (0.9)253.8 (1.0)Evidence base254.0 (1.1)———Gain for patients354.3 (0.8)———Gain for physicians253.8 (0.9)———Risks, side and adverse effects354.5 (0.6)———Transferability into routine care253.3 (1.0)———354.4 (0.9)354.3 (0.7)How many times do you think you would use1this app in the next 12 months if it was relevantto you?53.2 (1.2)253.9 (0.7)Would you pay for this app?132.0 (0.7)132.4 (0.8)What is your overall star rating of the app?454.6 (0.5)354.6 (0.6)Awareness254.5 (0.8)354.6 (0.6)Knowledge354.6 (0.6)354.8 (0.6)Attitudes253.7 (0.9)354.3 (0.7)Intention to change353.9 (0.8)454.4 dical gainSubjective qualityWould you recommend this app to people whomight benefit from SL FORenderXJMIR Mhealth Uhealth 2020 vol. 8 iss. 2 e16403 p. 6(page number not for citation purposes)

JMIR MHEALTH AND UHEALTHSubscaleaDittrich et alMARS-Ga surgeonsuMARS-Gb athletesMinimumMaximumMean (SD)MinimumMaximumMean (SD)Help seeking254.1 (1.0)253.8 (1.0)Behavior change254.0 (0.9)354.3 (0.8)MARS-G: German Mobile App Rating Scale.buMARS-G: (user) German Mobile App Rating Scale.cNot applicable.DiscussionPrincipal FindingsOur research using the Ankle Joint App demonstrates thatmHealth-based rehabilitation programs might be an adequateand innovative tool for patient education, prevention, andcollection of personal data.The achieved (user) MARS-G scores prove the app’s qualityfrom a professional and user point of view, demonstrating acomparatively high overall mean (user) MARS-G value [33].The highest scores were reached in the functionality section forboth surgeons and athletes. In accordance with a recent surveyamong orthopedic and trauma surgeons, intuitive usability wasconsidered the most important factor for the regular use andquality of an app. The integration of complex functions in anintuitive lean and secure user interface poses a great challengeto the development team. Moreover, the development of anintuitive frontend is complex and involves high developmentcosts and test phases [38]. Multifunctional apps, for example,in the field of diabetes mellitus type II therapy for patients over50 years showed limited usability with negative effects oncompliance and therapy outcomes. Apps with basic functionsprovide enhanced usability [39], but the limitation of softwarefeatures affects the app’s functionality. To address thisdivergence, trial runs with specific target groups and permanentreevaluation of the initial concept are mandatory during theapp’s development process.As a first step, when developing an app, the target group andthe intended purpose have to be defined precisely. The AnkleJoint App was especially designed for young and active patientsto optimize conservative rehabilitation following an acute anklesprain without osseous lesions. With respect to this, thedifferences in evaluating the medical gain for physicians andpatients, with individual requirements in their rehabilitationepisode [40], can be explained.Customization seems to be important to the target group andmight be improved in our app. We believe that medical appshave to be adaptable not only to the specific users’ requirementsbut also to the varying hospital standards. The aspects to beconsidered in the development of medical apps are the limitedareas of application in combination with varying standards oftreatment, both national and international, and the legal andmedical aspects of an app with regard to liability and dataprotection [21]. These aspects represent a challenge for financingthe complex development and maintenance of an app, as the 10most popular apps ranked by the number of users in Germanyin 2018 were all available for free download [41]. FORenderXConsidering recent data scandals, which led to a fundamentaldistrust of apps that might be implemented in the context of BigData, the secure and transparent collection of medical personaldata can be challenging [42,43]. For this reason, we decided tostore personal data exclusively on the mobile device to avoidcloud upload. In general, dichotomous scenarios about dataexchange between patients and medical staff are possible. Therecovery progress could be displayed analogously on thepatient’s smartphone in the event of a doctor’s appointment (eg,CAIT). Alternatively, an upload of data into a secure cloudsystem can be taken into consideration [44]. In the event ofdeviations from the expected progression of the disease, patientscould be informed about and provided with medical expertisemore rapidly. Moreover, the collection of validated scores andsurveys might be relevant for academic research.In contrast to these positive effects, app users and providers(physicians and medical staff) should keep in mind that thecollection and processing of personal data also representcornerstones of app financing. This could lead to potentialconflicts of interest as the collected data represent an immensevalue, for example, for the provision of personalized advertising[45]. Before downloading an app, the financing, developmentprocess, and data flow have to be completely and plausiblydepicted by the publisher. Therefore, transparent and appropriateapp store descriptions, data protection regulations, and termsand conditions of use are of utmost importance [46].This study has some limitations. The evaluation of the app’squality was carried out within a theoretical framework; thus, itonly reflects its use to a limited extent in daily clinical practice.It has to be mentioned that the app was only evaluated by arelatively small number of users (patients) for a short period of3 months. Thus, data on compliance, demographics, and usagebehavior are hardly representative. Moreover, the economicaspects of the development process and app costs per user werenot taken into account. In addition, the response rate wasmoderate, which might lead to a bias toward users with highdigital affinity. Comparative randomized control trial studiesare required to gain funded evidence on the app’s positive effectson patient education and treatment progress in comparison withestablished nondigital therapy paths to prevent CAI and reacha final scientific conclusion; this has to be addressed by futurestudies.Nowadays, in many countries, an increasing number of patientsvisiting emergency units with minor complaints can beregistered. Often, the treatment of these patients is time andstaff consuming, compromising the medical attention of moreseverely injured individuals. This overcrowding may lead tonegative consequences to the patients’ safety and their outcomeJMIR Mhealth Uhealth 2020 vol. 8 iss. 2 e16403 p. 7(page number not for citation purposes)

JMIR MHEALTH AND UHEALTH[47-49]. Given the increasing workload, physicians aredissatisfied with highly time-consuming procedures, forexample, electronic patient recording in the emergencydepartment [50,51]. Apps might be used by the emergency staffto easily create and recommend digitally customized aftercareplans.Moreover, the established discharge letter contains medicalterminology, which offers very little benefit to a self-determined,competent patient. This practice does not meet the requirementsof adequate patient involvement in the treatment process [52].Improving patient education and optimizing the communicationstructures via apps on mobile devices have the potential to solvethese issues. Individually designed and supervised aftercaretreatments showed better outcomes [53]. The Ankle Joint Apphas a modular design and might be transferred to a wide rangeof aftercare treatments.In contrast to the great potential of standardized medical appusage, there are also risks. However, medical resources andhealth care have to be distributed equally for everyone on thebasis of moral and ethical obligations. This is why medical appusage also entails a particular risk of disadvantaging groupswith low health competence and a high risk of disease [39]. Inparticular, the elderly patient might be disadvantaged by theDittrich et aluse of medical apps, because in 2014, only about 17% of theindividuals over 65 years regularly used a smartphone [54]. Asdegenerative diseases represent an important pillar of orthopedicand trauma surgery expertise, special attention has to be paidon the app development for these newcomers and theirrequirements in the future. Particularly in the area of appusability, the requirements of elder generations have to beaddressed, for example, implementing an intuitive interface, areading function, or a screen magnifier [55]. Self-endangermentbecause of incorrect app usage might occur, but the risk can bereduced by an onboarding function with an introduction of theapp to new users and individual feedback mechanisms [56].ConclusionsWorking in a multidisciplinary team, using a backend structureto modify the app’s content and using React Native, proved tobe efficient in the development process of medical apps. Thesuccess was proven by reaching high overall mean MARS-Gscores for the Ankle Joint App in surgeons and athletes. Dataobtained suggest that an mHealth-based rehabilitation programmight be a useful tool for patient education and collection ofpersonal data. The achieved (user) MARS-G scores prove thetested app’s high quality. Medical app development with an apriori defined target group and a precisely intended purpose, ina multidisciplinary team, is highly promising.AcknowledgmentsWe acknowledge support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) and Saarland Universitywithin the funding programme Open Access Publishing.Conflicts of InterestFD and SB are active in Mediploy GmbH and in the development process of the Ankle Joint App.References1. H, Harrasser N, Fehske K. [Lateral ligament injuries]. Unfallchirurg 2018 Sep;121(9):683-692. [doi:10.1007/s00113-018-0535-2] [Medline: 30054645]Vuurberg G, Hoorntje A, Wink LM, van der Doelen BF, van den Bekerom MP, Dekker R, et al. Diagnosis, treatment andprevention of ankle sprains: update of an evidence-based clinical guideline. Br J Sports Med 2018 Aug;52(15):956. [doi:10.1136/bjsports-2017-098106] [Medline: 29514819]Bielska IA, Wang X, Lee R, Johnson AP. The health economics of ankle and foot sprains and fractures: a systematic reviewof English-language published papers. Part 1: Overview and critical appraisal. Foot (Edinb) 2019 Jun;39:106-114. [doi:10.1016/j.foot.2017.04.003] [Medline: 29108669]Hupperets MD, Verhagen EA, Heymans MW, Bosmans JE, van Tulder MW, van Mechelen W. Potential savings of aprogram to prevent ankle sprain recurrence: economic evaluation of a randomized controlled trial. Am J Sports Med 2010Nov;38(11):2194-2200. [doi: 10.1177/0363546510373470] [Medline: 20699429]Harrington KD. Degenerative arthritis of the ankle secondary to long-standing lateral ligament instability. J Bone JointSurg Am 1979 Apr;61(3):354-361. [Medline: 429402]Kazemi K, Arab AM, Abdollahi I, López-López D, Calvo-Lobo C. Electromiography comparison of distal and proximallower limb muscle activity patterns during external perturbation in subjects with and without functional ankle instability.Hum Mov Sci 2017 Oct;55:211-220. [doi: 10.1016/j.humov.2017.08.013] [Medline: 28843163]Lobo CC, Morales CR, Sanz DR, Corbalán IS, Marín AG, López DL. Ultrasonography comparison of peroneus musclecross-sectional area in subjects with or without lateral ankle sprains. J Manipulative Physiol Ther 2016;39(9):635-644.[doi: 10.1016/j.jmpt.2016.09.001] [Medline: 27793349]Valderrabano V. Joint-preserving surgery of ankle osteoarthritis. Foot Ankle Clin 2013 Sep;18(3):xiii-xxiv. [doi:10.1016/j.fcl.2013.06.013] [Med

Saarland University Medical Center and Saarland University Faculty of Medicine Kirrbergerstr. 100 Building 37-38 Homburg Germany Phone: 49 68411624520 Email: [email protected] Abstract Background: Ankle sprains are one of the most frequent sports injuri