Mouton et al. J EXP ORTOP (2021) 8:45 Journal of https://doi.org/10.1186/s40634-021-00366-7 Experimental Orthopaedics REVIEW PAPER Open Access Preliminary experience of an international orthopaedic registry: the ESSKA Paediatric Anterior Cruciate Ligament Initiative (PAMI) registry Caroline Mouton1,2, Håvard Moksnes3, Rob Janssen4,5,6, Christian Fink7,8, Stefano Zaffagnini9, Juan Carlos Monllau10, Guri Ekås3,11,12, Lars Engebretsen3,13 and Romain Seil1,2,14* Abstract Paediatric and adolescent ACL injuries are an emerging health burden, increasing at a higher rate than in adults. They compromise quality of life, affect knee structure and function, lead to the early development of osteoarthritis and are a serious economic burden due to shortened professional careers and subsequent surgeries. Up to 35% of children and adolescents will experience a second ACL injury and this population particularly at high risk of secondary intraarticular soft tissue degeneration and growth abnormalities. However, there is still a lack of high-quality out- come studies on this specific population and many knowledge gaps persist in the current treatment guidelines. It is currently unknown whether ACL reconstruction in this young population decreases the risk of irreversible secondary intraarticular soft tissue degeneration. Furthermore, it is not known whether return to high or elite level sports after paediatric ACL injury or reconstruction should be recommended. The relatively low number of paediatric ACL injuries seen in each hospital makes it necessary to conduct international multi-centre studies to collect robust data to pro- vide evidence-based guidelines for the treatment of these injuries. The Paediatric Anterior Cruciate Ligament Initiative (PAMI) was thus started by the European Society of Sports Traumatology, Knee Surgery & Arthroscopy and opened for patient inclusion in 2018. This comprehensive overview of the first 2 years of the PAMI registry shows that the project is now well consolidated and accepted by the European orthopaedic community. Future challenges include ensur- ing additional external funding to ascertain long term sustainability and continuous dissemination of the knowledge acquired in scientific journals. Keywords: Anterior cruciate ligament, Knee, Paediatric, Child Introduction of osteoarthritis [27] and is a serious economic burden An anterior cruciate ligament (ACL) injury in paediat- due to potentially shortened professional careers and ric and adolescent populations is a life-long burden both later surgeries. Paediatric and adolescent ACL injuries for the paediatric and adolescent athletes and the soci- are increasing rapidly [7, 20, 25, 29]. This population age ety. It compromises quality of life, affects future knee group is associated to the fastest growing incidence rate structure and function, leads to the early development of anterior cruciate ligament injuries [20, 26]. This rise is significantly higher than in adults and places these inju- ries as an emerging health burden [20]. *Correspondence: rseil@yahoo.com Many knowledge gaps persist in the current treat- 1 Department of Orthopaedic Surgery, Centre Hospitalier de Luxembourg – Clinique d’Eich, 78 Rue d’Eich, L‑1460 Luxembourg, Luxembourg ment guidelines of paediatric and adolescent ACL Full list of author information is available at the end of the article injuries [6, 15], leaving the treating physicians with a © The Author(s) 2021. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://​creat​iveco​mmons.​org/​licen​ses/​by/4.​0/. Mouton et al. J EXP ORTOP (2021) 8:45 Page 2 of 7 therapeutic dilemma. Nonoperative treatment has shown protocols as well as surgical procedures of paediatric and to be successful in some patients. However, an associa- adolescent ACL injuries on an international level. tion between the delay of surgery and the occurrence of The PAMI registry aims to provide important insights secondary meniscus and cartilage lesions suggests that it into several aspects of paediatric ACL injuries. Initially may increase the risk of irreversible secondary intraar- it will help to assess the magnitude of ACL injuries aris- ticular soft tissue degeneration [8]. The limitations in ing in the paediatric and adolescent population as well as the literature preclude firm conclusions [9, 10]. Paedi- describing current treatment options following a paediat- atric ACL reconstruction surgery is challenging for the ric ACL injury. Understanding of the injury mechanism orthopaedic surgeon and highly specialised. A variety of as well as collective and individual ACL injury risk fac- surgical techniques have been described in the orthopae- tors in this specific population may also help establishing dic literature, making it difficult to establish generaliz- a knowledge base for future ACL injury prevention ini- able treatment standards. Given the complex anatomy of tiatives. The analyses of short-, medium- and long-term paediatric knees, each technique has its individual risks clinical outcome will help to improve the understanding and complications. All of them bear a serious potential of the anatomy, the biomechanics and the development to generate secondary growth abnormalities [12]. There of children’s knees. It will also extend the evidence base is a lack of high-quality outcome studies after surgi- on optimal treatment choices by providing important cal treatment and it is furthermore currently unknown insights into the natural history of ACL injured knees whether ACL reconstruction in this young population in children, and will allow discriminating those patients decreases the risk of irreversible secondary intraarticular needing operative treatment from those who benefit soft tissue degeneration. Up to 35% of children and ado- most from a nonoperative treatment. Such knowledge lescents experience a second ACL injury, be it a retear of will help to improve rehabilitation strategies in order their ACL reconstruction or an injury of the unaffected to reduce the pre-existing high injury recurrence and contralateral knee [3, 18]. It remains unknown whether improve secondary prevention after ACL injury and sur- return to high or elite level sports after paediatric ACL gery in this young and active population. The project will injury or reconstruction should be recommended and on provide indispensable data required to identify children which criteria it should be based [4]. at risk for ACL injuries, and to diagnose and treat ACL The relatively low number of paediatric ACL injuries injuries in children and adolescents based on scientific seen in each hospital makes it necessary to conduct inter- evidence. Finally, the project will help establishing inter- national multi-centre studies to collect sufficient and national treatment guidelines. robust data in order to provide evidence-based guide- lines for the treatment of paediatric ACL injuries. The History 2018 International Olympic Committee (IOC) consensus The PAMI registry represents one of the rare interna- statement on prevention, diagnosis and management of tional collaborative studies in orthopaedic surgery and paediatric ACL injuries [1] highlighted this multicen- orthopaedic sports medicine. The initial idea to create tre approach as one of the highest research priorities an international registry for the treatment of paediat- in the field. The Paediatric Anterior Cruciate Ligament ric anterior cruciate ligament (ACL) injuries was born Initiative (PAMI) was started by the European Society in 2013. The initiative was built on a closed e-survey of Sports Traumatology, Knee Surgery & Arthroscopy submitted to ESSKA member and affiliates in July 2013 (ESSKA) in 2013 with the long-term vision to create a [17, 21]. The aim of the survey was to describe the treat- multicentre international registry. The PAMI registry ment options in paediatric ACL injuries. Beyond the fact was opened for patient inclusion in late 2018. It repre- that it showed the feasibility of the initiative in terms of sents one of the rare international collaborative studies recruitment capacity, it helped to document that the inci- in orthopaedic surgery and orthopaedic sports medicine. dences of paediatric ACL injuries and idiopathic growth The aim of the present report is to give a comprehensive disturbances may be higher than previously estimated. overview of the PAMI registry, to present preliminary Additionally, that there were substantial differences with epidemiological data and discuss its future. regard to preferred treatment algorithms, surgical tech- niques and long-term follow-up procedures. Planning Aims of the initiative and structuring lasted until 2016 when the development The main purpose of the PAMI registry is to collect data of the PAMI registry was started. In 2018, the PAMI col- from orthopaedic surgeons who are treating children laboration was officially announced [19] and opened for and adolescents with ACL injuries in order to improve participation requests during the ESSKA Biennial Con- existing treatment algorithms, standardize treatment gress in May 2018. Inclusion of patients was initiated Mouton et al. J EXP ORTOP (2021) 8:45 Page 3 of 7 in December 2018. In February 2021, the number of also document the results of the Lachman test [24], the patients included in the PAMI exceeded 100. pivot shift test [13] and the recurvatum for each patient and injury. Patients are then followed regardless if they Stakeholders and overall project organization are treated surgically or not. In case of a surgical treat- The PAMI was initiated, promoted and financially sup- ment, a full report is requested containing data on the ported by ESSKA and the ESSKA Foundation. Essential ACL reconstruction (surgical technique, graft, fixations, financial support as a starting grant was provided by tunnel …) as well as ACL and associated lesions (other Smith & Nephew and the Olympic Solidarity (OS). The knee ligament injury, menisci and cartilage) and proce- project was undertaken in collaboration with the Sports dures (e.g. extra-articular tenodesis…). The skeletal age at Medicine Research Laboratory of the Luxembourg Insti- the time of the surgery as well as the clinical examination tute of Health (LIH) for its scientific and technical expe- under anaesthesia (Lachman test, the pivot shift test and rience. A dedicated steering committee (PAMI steering recurvatum) can also be specified. Finally, patients are committee) guarantees that the general objectives of the contacted every year to fill in the Paediatric International PAMI project are met, advises ESSKA on strategic deci- Knee Documentation Committee Subjective Knee Form sions regarding the quality assurance and the develop- in Children (Pedi-IKDC) [16] and the Pediatric Activity ment of the PAMI registry and is responsible for project Rating Scale (HSS Pedi-FABS) [11]. These questionnaires related communication and dissemination of results. The have been shown to be adequate for children with knee daily administrative management is taken care of by a ligament injuries [5]. They are currently available in Eng- member of the PAMI steering committee acting as the lish, German, French, Norwegian, Italian and Dutch. The project manager. The project manager’s tasks include, but foreseen follow-up is of 30 years for each patient. Any are not limited to ensure communication with all project new ACL injury (i.e. to the same or opposite knee) that stakeholders, assist partner institutions in applying to the may occur during the follow up of the patient can be doc- PAMI project and ensure that all legal requirements are umented so as to know the recurrence rate of ACL inju- met. As the PAMI initiative aims at including data from ries in this population. multiple centres, it is open to any institution willing to The PAMI steering committee and partner institutions engage in this project and to provide data on current sur- are currently discussing to develop the long-term out- gical and non-surgical treatments and their clinical out- comes such as imaging and its variables of interest (i.e. comes using a dedicated web portal. growth disturbance, tibial slope…). Although growth disturbances are rare, they are a serious risk [12] and Patient selection and outcomes require a regular patient monitoring in order to detect Currently, every patient with a physical activity-related any leg length discrepancy or malalignment which may traumatic ACL injury may be recruited for the PAMI be the result of a growth arrest, an over- or undergrowth provided that the diagnosis is confirmed according to process. Other data on knee function such as the results criteria established in the IOC consensus [1] and that of functional performance tests, of isokinetic force tests the skeletal age at the time of inclusion or at surgery is of knee extensor and flexor muscles, of knee joint laxity between 8 and 14 years for girls or 8 and 16 years for boys measurements may also be implemented. (as determined on radiographs of the left hand according to the Greulich & Pyle atlas criteria [14]). Patients with PAMI database knee dislocations, combined ACL-PCL injuries and / or All data are entered in a secured website with a strictly tibial spine fractures are currently excluded. The inclu- limited access to PAMI participating centres. The com- sion of younger patients or patients with bony avulsion or pliance of the project and platform with the General ACL agenesis is currently under discussion. Data Protection Regulation (GDPR) 2016/679 has been A data collection platform has been created, the PAMI previously explained in a specific book chapter [22]. In database or PAMI platform, to carry out a systematic summary, a secured communication protocol has been and standardized collection of outcomes judged as rel- implemented to secure data communication to and from evant to the problem of paediatric ACL injuries. Infor- the PAMI database. The system works with a two-factor mation collected within the PAMI project currently authentication solution: the site coordinator enters his consist of 5 data categories: patient and injury-related username/password and receives a numeric code via information, clinical examination, treatment and follow- SMS (Short Message Service) on his or her personal cell up. Patient data include birth date, sex, height, weight, phone to be able to enter the platform. skeletal age. Other mandatory data are related to injury All included data are pseudonymized to ensure maxi- (date of injury, injured side, previous knee injuries, activ- mal data protection and avoid legal issues related to data ity at time of injury, injury mechanism). All centres can transfer between different European countries. Patient Mouton et al. J EXP ORTOP (2021) 8:45 Page 4 of 7 identification information is replaced by a patient ID and delayed until the end of the growth period (closed phy- data cannot be attributed to a patient. As a consequence, ses – n = 18; mean age = 15 ± 1). Overall, 36 patients each site-coordinator manages a correspondence table out of 61 (59%) presented with a meniscal tear (5 bime- between patient ID information and a primary key gener- niscal tears). In ACL reconstructions with open phy- ated by the system to ensure long-term follow-up of each ses, semitendinosus and/or gracilis graft were preferred patient. (72%) over quadriceps tendon (28%). Extraarticular ACL tenodesis were performed in 40% of patients. Lesions to Preliminary epidemiological data the medial meniscus were observed in 7 knees (16%), of From the first inclusion in October 2018 to February which 6 were repaired. Lateral meniscus lesions were 2021 (Fig. 1a), 100 patients (71 males / 29 females) from observed in 19 knees (44%), of which 9 were repaired. In 7 institutions (Austria, Italy, Luxembourg, Netherlands, delayed ACL reconstructions, quadriceps tendon (44%), Norway, Spain) were included in the PAMI registry. semitendinosus and/or gracilis (39%) and patellar tendon These patients sustained 104 ACL injuries (4 patients (17%) were used. Extraarticular ACL tenodesis were per- with 2 injuries: 3 contralateral ACL injuries and 1 graft formed in 33% of patients. Lesions to the medial menis- rupture). The median chronological age at injury was cus were observed in 8 knees (44%), of which 6 were 13 (interquartile range: 3) years (Fig. 1b). Most injuries repaired. Lateral meniscus lesions were observed in 6 occurred during physical activities (87%) mainly while knees (33%), of which 3 were repaired. playing football (n = 37), during alpine skiing (n = 23) or trampoline (n = 9) (Fig. 1c). At the time of the analysis, there were 28 ongoing Preliminary experience and future perspectives nonoperative treatments, 4 patients with knee surgery This is the first time that a comprehensive overview of the without ACL reconstruction, 70 ACL reconstructions PAMI registry is provided, together with preliminary epi- and 2 drop out (patients moved into another hospital; demiological data. The PAMI registry is one of the rare Fig. 1d). Time from injury to surgery reached a median of international collaborative studies in orthopaedic surgery 6 months. Patients undergoing surgery were further sepa- and orthopaedic sports medicine. A similar project in rated into 2 groups: ACL reconstructions with open phy- children named “Pediatric ACL: Understanding Treat- ses (n = 43; mean age = 13 ± 2) and ACL reconstructions ment Options (PLUTO)” has been started in 2016 and is Fig. 1 Preliminary epidemiological data from PAMI. a Number of patients recruited in the PAMI since 2018 (2 patients recruited in 2021). b Chronological age of patient at injury (n = 100 patients). c Injury context (n = 104 injuries). d Treatment (n = 104 injuries) Mouton et al. J EXP ORTOP (2021) 8:45 Page 5 of 7 conducted in 10 centres in North America with close to the ethical aspects probably remain a major weakness of 800 patients (August 3, 2020) enrolled so far. any international multi-centre studies. The administra- While being in line with the research priorities high- tive burden for each partner institution was high as they lighted by the 2018 IOC consensus statement on pre- had to seek ethics clearance to their local or national eth- vention, diagnosis and management of paediatric ACL ics committee in accordance with their national laws and injuries [1], these initiatives represent an organizational regulations. This process is highly variable in the vari- challenge and many barriers may interfere with their set ous countries of the EU and was also slowed down due up. First of all, the overall project organisation and study to required translations of patient information, consent protocol are to be consolidated. While the idea of the and questionnaires (Pedi-IKDC and HSS Pedi-FABS) PAMI was born in 2013, first patient inclusion could only which were translated through a standardised process be achieved in 2018. Many prerequisites were indeed [2]. Beginning of 2021, 8 centres were actively recruit- required in order to launch such an international mul- ing patients with a continuous increase of patient inclu- ticentre initiative. These are similar to the planning of a sion observed over time. Although the current results patient/disease registry. According to the published user are limited to 100 patients, we are confident that the guides to evaluate patient outcomes [23], it was impor- recruitment will continue to grow exponentially with the tant to articulate the purpose, identify key stakeholders increase of partner institutions. Seven additional centres and assess the feasibility and sustainability of the future from Italy, Greece, France and UK are indeed in the pro- registry. Then, a registry team, previously mentioned as cess of ethics clearance in order to join the initiative. the steering committee, was built in order to establish the The feedback of recruiting centres had a significant governance and oversight plan, define the scope and rigor impact on the evolution and consolidation of the PAMI needed, define the targeted population, dataset and out- registry. It has helped to adapt the PAMI database to comes, develop the study protocol and assess the follow- enhance user’s experience with the PAMI web portal as up of the project plan. Likewise, innovative technological well as to consolidate data accuracy and completeness, solutions had to be implemented. In case of the PAMI, two of the major data quality dimensions according to project development included the creation of a specific methodological guidelines for registries [28]. This was IT platform which took an additional year. Setting up only possible with an extensive and continuous com- multicentre initiatives thus represents years of prepara- munication between the different partners. Communi- tion and the related organisational process is rarely linear. cation between the steering committee and partner or Many of the previously cited steps may occur in parallel interesting institutions has now been planned and stand- and should be periodically (re)evaluated to ensure that ardised and includes (1) a yearly newsletter to increase the objectives are being met. For example, in the case of awareness about the initiative and recruit new centres, ACL injuries in paediatric and adolescent populations, (2) guidelines provided to partner institutions to ensure treatment practices may rapidly evolve over years. This data quality and proper use of the PAMI platform, (3) requires that the content of the PAMI database is regu- 2 participants newsletter per year including latest rel- larly adapted (i.e. adding additional field of data if a new evant publications and the evolution of the recruitment surgical technique is used or a new possible answer in a and database to keep all partners motivated, (4) a com- drop-down list) in order to capture the latest trends. mon workshop every year to discuss about the difficulties Major difficulties encountered during the first years of around the project and its perspectives. As an example, the PAMI included funding, ethical approval and recruit- during the last workshop in October 2020, inclusion/ ment. Unstable funding remains the main threat in every exclusion criteria were discussed again as well as the pos- research project one may encounter [28]. Currently, long sibility to extend the content of data gathered within the term sustainability of the PAMI must be ascertained project (i.e. assessment of long-term outcomes). In addi- by additional external funding. The interest of partner tion to this communication strategy, the PAMI managers institutions is no longer to be proven, but project con- will organise in 2021 the first monitoring of PAMI data tinuity will have to be constantly maintained through and start to provide yearly personalised feedbacks to regular feedback to stakeholders, common publications partner institutions on their data in order to ensure the and networking initiatives. The first years of the project quality of data. The PAMI steering committee will make were decisive to consolidate the project in its long term it a priority for the next years to continue to improve the although patient recruitment started slowly. The main PAMI registry. This will be achieved through the organi- reasons behind this were that ethical and legal require- sation of periodic critical evaluations to ensure that the ments had to be fulfilled before any patients could be PAMI objectives are met and up to date or to be able to entered in the database. Despite the standardisation of quickly react and adapt the initiative in line with the rel- European legislation on clinical trials and data protection, evant published scientific literature within the field. Mouton et al. J EXP ORTOP (2021) 8:45 Page 6 of 7 Conclusion Institute of Research in Orthopaedics, Sports Medicine and Science (LIROMS), Luxembourg, Luxembourg. 3 Oslo Sports Trauma Research Centre (OSTRC), This comprehensive overview of the first 2 years of the Norwegian School of Sports Sciences, Oslo, Norway. 4 Department of Ortho- PAMI experience shows that the project is now well paedic Surgery & Trauma, Máxima Medical Center, Eindhoven‑Veldhoven, consolidated and accepted by the orthopaedic commu- The Netherlands. 5 Orthopaedic Biomechanics, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Nether- nity. The strategy to ensure data quality, communication lands. 6 Value‑Based Health Care, Department of Paramedical Sciences, Fontys with partner institutions and dissemination of results is University of Applied Sciences, Eindhoven, The Netherlands. 7 Gelenkpunkt now well established. Future challenges include ensuring - Sports and Joint Surgery, Innsbruck, Austria. 8 Research Unit for Orthopaedic Sports Medicine and Injury Prevention (OSMI), UMIT Tirol, Hall, Austria. 9 IIa Cli- additional external funding to ascertain long term sus- nica Ortopedica E Traumatologica, IRCCS Istituto Ortopedico Rizzoli, Bologna, tainability of the PAMI and continuous dissemination of Italy. 10 Hospital del Mar / Hospital Universitari Dexeus, Universitat Autònoma the knowledge acquired in scientific journals. These con- de Barcelona (UAB), Barcelona, Spain. 11 Department of Orthopedic Surgery, Akershus University Hospital, Lørenskog, Norway. 12 Institute of Clinical Medi- tinuous efforts are needed to improve existing treatment cine, University of Oslo, Oslo, Norway. 13 Department of Orthopaedic Surgery, algorithms, standardize treatment protocols and improve Oslo University Hospital, Oslo, Norway. 14 Human Motion, Orthopaedics, Sports rehabilitation strategies to reduce the pre-existing high Medicine and Digital Methods, Luxembourg Institute of Health, Luxembourg, Luxembourg. injury recurrence in paediatric and adolescent ACL inju- ries and surgery on an international level. Received: 29 April 2021 Accepted: 15 June 2021 Abbreviations ACL: Anterior cruciate ligament; ESSKA: European Society of Sports Traumatol- ogy, Knee Surgery & Arthroscopy; GDPR: General Data Protection Regulation; References HSS Pedi-FABS: Pediatric Activity Rating Scale; IOC: International Olympic 1. Ardern CL, Ekas GR, Grindem H, Moksnes H, Anderson AF, Chotel F et al Committee; LIH: Luxembourg Institute of Health; MRI: Magnetic resonance (2018) 2018 International Olympic Committee consensus statement on imaging; OS: Olympic Solidarity; PAMI: Paediatric Anterior Cruciate Ligament prevention, diagnosis and management of paediatric anterior cruciate Initiative; Pedi-IKDC: Paediatric International Knee Documentation Commit- ligament (ACL) injuries. Br J Sports Med 52:422–438 tee; PCL: Posterior cruciate ligament; PLUTO: Pediatric ACL: Understanding 2. Danielsen AK, Pommergaard HC, Burcharth J, Angenete E, Rosenberg Treatment Options. J (2015) Translation of questionnaires measuring health related quality of life is not standardized: a literature based research study. PLoS One Acknowledgements 10:e0127050 The authors would like to further acknowledge their respective site coordina- 3. Dekker TJ, Godin JA, Dale KM, Garrett WE, Taylor DC, Riboh JC (2017) tor for their active involvement in the PAMI project: Return to sport after pediatric anterior cruciate ligament reconstruction - Marieke van der Steen for the Department of Orthopaedic Surgery, and its effect on subsequent anterior cruciate ligament injury. J Bone Máxima Medical Centre & Catharina Hospital, Eindhoven, The Netherlands Joint Surg Am 99:897–904 - Elisabeth Abermann, Kathrin Stradner for Gelenkpunkt—Sports and Joint 4. Dietvorst M, Brzoskowski MH, van der Steen M, Delvaux E, Janssen RPA, Surgery, Innsbruck, Austria & Research Unit for Orthopaedic Sports Medicine Van Melick N (2020) Limited evidence for return to sport testing after ACL and Injury Prevention (OSMI), UMIT Tirol, Hall, Austria reconstruction in children and adolescents under 16 years: a scoping - Luca Macchiarola for IIa Clinica Ortopedica e Traumatologica, IRCCS review. J Exp Orthop 7:83–83 Istituto Ortopedico Rizzoli, via Cesare Pupilli 1, 40136, Bologna, Italy 5. Dietvorst M, Reijman M, van Groningen B, van der Steen MC, Janssen - Simone Perelli for Hospital del Mar / Hospital Universitari Dexeus. Univer- RPA (2019) PROMs in paediatric knee ligament injury: use the Pedi-IKDC sitat Autònoma de Barcelona (UAB), Spain and avoid using adult PROMs. Knee Surg Sports Traumatol Arthrosc 27:1965–1973 Authors’ contributions 6. Dietvorst M, Reijman M, van Zutven R, van den Bekerom MPJ, Meuf- CM was a major contributor in writing the manuscript. All authors read, fels DE, Somford MP et al (2021) Current state of care for pediatric ACL revised critically and approved the final manuscript. ruptures in the Netherlands: a survey. J Knee Surg 34:520–525 7. Dodwell ER, Lamont LE, Green DW, Pan TJ, Marx RG, Lyman S (2014) 20 Funding years of pediatric anterior cruciate ligament reconstruction in New York The Paediatric Anterior Cruciate Ligament Initiative received a starting grant State. Am J Sports Med 42:675–680 from Smith & Nephew and from the IOC Olympic Solidarity. 8. Ekås GR, Ardern CL, Grindem H, Engebretsen L (2020) Evidence too weak to guide surgical treatment decisions for anterior cruciate ligament Availability of data and materials injury: a systematic review of the risk of new meniscal tears after anterior Not applicable. cruciate ligament injury. Br J Sports Med 54:520–527 9. Ekås GR, Laane MM, Larmo A, Moksnes H, Grindem H, Risberg MA et al (2019) Knee pathology in young adults after pediatric anterior cruciate Declarations ligament injury: a prospective case series of 47 patients with a mean 9.5- year follow-up. Am J Sports Med 47:1557–1566 Ethics approval and consent to participate 10. Ekås GR, Moksnes H, Grindem H, Risberg MA, Engebretsen L (2019) Cop- Not applicable. ing with anterior cruciate ligament injury from childhood to maturation: a prospective case series of 44 patients with mean 8 years’ follow-up. Am Consent for publication J Sports Med 47:22–30 Not applicable. 11. Fabricant PD, Robles A, Downey-Zayas T, Do HT, Marx RG, Widmann RF et al (2013) Development and validation of a pediatric sports activity Competing interests rating scale: the Hospital for Special Surgery Pediatric Functional Activity None. Brief Scale (HSS Pedi-FABS). Am J Sports Med 41:2421–2429 12. Frosch KH, Stengel D, Brodhun T, Stietencron I, Holsten D, Jung C et al Author details (2010) Outcomes and risks of operative treatment of rupture of the 1 Department of Orthopaedic Surgery, Centre Hospitalier de Luxembourg – Cli- anterior cruciate ligament in children and adolescents. Arthroscopy nique d’Eich, 78 Rue d’Eich, L‑1460 Luxembourg, Luxembourg. 2 Luxembourg 26:1539–1550 Mouton et al. J EXP ORTOP (2021) 8:45 Page 7 of 7 13. Galway HR, MacIntosh DL (1980) The lateral pivot shift: a symptom and GDPR: walking in the footsteps of the PAMI project (Paediatric ACL moni- sign of anterior cruciate ligament insufficiency. Clin Orthop Relat Res toring initiative). In: Musahl V, Karlsson J, Hirschmann MT et al (eds) Basic (147):45–50. methods handbook for clinical orthopaedic research. Springer Berlin 14. Greulich WW, Pyle SI (1959) Radiographic atlas of skeletal development of Heidelberg, Berlin, Heidelberg, pp 427–434. https://​doi.​org/​10.​1007/​978- the hand and wrist. California: Stanford University Press 3-​662-​58254-1_​45 15. Janssen R, Lind M, Engebretsen L, Moksnes H, Seil R, Faunø P et al (2018) 23. TO CNHI (2010) Registries for evaluating patient outcomes: a user’s guide Pediatric ACL injuries: treatment and challenges. In: Kerkhoffs GMMJ, second edition Haddad F, Hirschmann MT, Karlsson J, Seil R (eds) ESSKA instructional 24. Torg JS, Conrad W, Kalen V (1976) Clinical diagnosis of anterior cruciate course lecture book: Glasgow 2018. Springer Berlin Heidelberg, Berlin, ligament instability in the athlete. Am J Sports Med 4:84–93 Heidelberg, pp 241–259. https://​doi.​org/​10.​1007/​978-3-​662-​56127-0_​17 25. Weitz FK, Sillanpää PJ, Mattila VM (2020) The incidence of paediatric 16. Kocher MS, Smith JT, Iversen MD, Brustowicz K, Ogunwole O, Andersen ACL injury is increasing in Finland. Knee Surg Sports Traumatol Arthrosc J et al (2011) Reliability, validity, and responsiveness of a modified 28:363–368 International Knee Documentation Committee Subjective Knee Form 26. Werner BC, Yang S, Looney AM, Gwathmey FW Jr (2016) Trends in pediat- (Pedi-IKDC) in children with knee disorders. Am J Sports Med 39:933–939 ric and adolescent anterior cruciate ligament injury and reconstruction. J 17. Moksnes H, Engebretsen L, Seil R (2016) The ESSKA paediatric anterior Pediatr Orthop 36:447–452 cruciate ligament monitoring initiative. Knee Surg Sports Traumatol 27. Whittaker JL, Woodhouse LJ, Nettel-Aguirre A, Emery CA (2015) Out- Arthrosc 24:680–687 comes associated with early post-traumatic osteoarthritis and other 18. Paterno MV, Rauh MJ, Schmitt LC, Ford KR, Hewett TE (2014) Incidence of negative health consequences 3–10 years following knee joint injury in second ACL injuries 2 years after primary ACL reconstruction and return youth sport. Osteoarthritis Cartilage 23:1122–1129 to sport. Am J Sports Med 42:1567–1573 28. Zaletel M, Kralj M, Magajne M, Doupi P (2015) Methodological guidelines 19. Seil R, Theisen D, Moksnes H, Engebretsen L (2018) ESSKA partners and and recommendations for efficient and rational governance of patient the IOC join forces to improve children ACL treatment. Knee Surg Sports registries. National Institute of Public Health, Ljubljana, pp 17–39 Traumatol Arthrosc 26:983–984 29. Zbrojkiewicz D, Vertullo C, Grayson JE (2018) Increasing rates of anterior 20. Shaw L, Finch CF (2017) Trends in pediatric and adolescent anterior cruci- cruciate ligament reconstruction in young Australians, 2000–2015. Med J ate ligament injuries in Victoria, Australia 2005–2015. Int J Environ Res Aust 208:354–358 Public Health 14(6):599 21. Siebold R, Seil R, Engebretsen L (2016) ACL tear in kids: serious injury with high risk of osteoarthritis. Knee Surg Sports Traumatol Arthrosc Publisher’s Note 24:641–643 Springer Nature remains neutral with regard to jurisdictional claims in pub- 22. Theisen D, Moksnes H, Hardy C, Engebretsen L, Seil R (2019) How to lished maps and institutional affiliations. organise an international register in compliance with the European