Pediatric anterior cruciate ligament injuries
– management, treatment rationale and long-term outcomes
PhD Clinical Thesis Guri Ranum Ekås
Faculty of Medicine 2020
© Guri Ranum Ekås, 2020
Series of dissertations submitted to the Faculty of Medicine, University of Oslo
ISBN 978-82-8377-596-9
All rights reserved. No part of this publication may be
reproduced or transmitted, in any form or by any means, without permission.
Cover: Hanne Baadsgaard Utigard.
Print production: Reprosentralen, University of Oslo.
Acknowledgements ... 2
Abbreviations ... 6
Preview of thesis ... 7
Included papers in thesis ... 8
Introduction ... 9
Aims of thesis ... 14
Material and methods ... 14
Summary of results... 29
Discussion of main findings ... 41
Methodological considerations ... 58
Ethical perspectives ... 77
Clinical implication and conclusion ... 79
Future research ... 81
References ... 85
Papers I-V ... 97
Table of Contents
Pediatric anterior cruciate ligament injuries
– management, treatment rationale and long-term outcomes
Acknowledgements
The research work for my thesis was conducted at the Oslo Sports Trauma Research Centre (OSTRC) and the Orthopedic Division, Oslo University Hospital between August 2015 and May 2019, in collaboration with the University of Oslo and Norwegian School of Sports Sciences (NIH). Our research group also acknowledge the Norwegian Sports Medicine Clinic (NIMI) for providing functional testing facilities. Also, we wish to thank the Sophie’s Minde Foundation and the Trust for Norwegian Sports Medicine and Physical Activity (Fondet til fremme av norsk idrettsmedisin og fysisk aktivitet) for appropriating a research grant and funding radiological imaging for our patient cohort.
During my early years of orthopedic training, I became involved in sports medicine because of my interest in road cycling. The field of sports medicine introduced me to a
multidisciplinary approach and the importance of integrated care. I experienced first-hand how this approach could be beneficiary for athletes and patients, and this brought about an interest in how to optimize healing, facilitate rehabilitation, improve outcomes and also prevent injuries. This experience has later shaped me as an orthopedic surgeon.
The realm of pediatric ACL injuries allows me to be involved in sports medicine, orthopedic surgery, physical rehabilitation and most importantly the treatment of young adolescents and children. A special thanks goes to all the patients involved in our clinical outcome study, who we in some cases have followed for more than 10 years.
First and foremost, I would like to thank my main supervisor Professor Lars Engebretsen. He has believed in me and been instrumental in introducing me to the field of sports medicine and ACL reconstructive surgery. My initial interest for pediatric ACL injuries was largely based on his facilitation and encouragement. Lars has been an absolutely fantastic supervisor with his extensive experience, sincere dedication, and vast knowledge in
orthopedics, and having such a longstanding and extensive list of merits both clinically and within research. His support has given me the confidence and motivation to fulfill my tasks and goals both within article writing and when presenting our work. Lars has been very generous with his time and I am very grateful for all his guidance.
Secondly, I wish to thank my closest research collaborators who are also my three co- supervisors. Professor May-Arna Risberg has been an inspiration and her work ethic has shown me that it is possible to set a goal and complete this on time. Her sincere dedication and thoroughness have been a great motivation. Hege Grindem has been a very close collaborator, and she has been crucial to the work we have done with gathering data and writing the articles. Håvard Moksnes has been very supportive during presentations and symposiums and has always been the first to respond with comments and advice during finalizing article manuscripts.
I want to give special thanks to Clare Ardern. She is a very special co-worker and a fantastic researcher. Clare and Hege have been the main locomotive engines and together a research powerhouse when it comes to the work we completed with the systematic review. Clare has played a crucial role in our research group.
Throughout the project period I have received great support from the Orthopedic
Department at Oslo University Hospital and the University of Oslo. As many of you know our department is divided between “Ullevål” and “Legevakten” and most of my orthopedic training I have completed at these two locations. I want to thank all my co-workers and in particular Professor Lars Nordsletten, Sverre Løken and Vera Halvorsen. They have all in their own ways guided me during my training and throughout my research endeavors and for that I am truly thankful. Also, I wish to thank the Department of Radiology and particularly Marit Mjelde for her work with analyzing images. In addition, Morten Fagerland has been very helpful with statistical analysis in conjunction with the systematic review. At the University of Oslo and the Institute of Clinical Medicine I wish to acknowledge Professor Ludvig Munthe for his advice on writing the clinical thesis.
My other place of work during the past four years has been the Sports Medicine Department (SIM) at the Norwegian School of Sport Sciences (NIH) and the research group Oslo Sports Trauma Research Center (OSTRC). Being part of this research environment established at NIH has allowed me to become a better researcher. The positive and friendly atmosphere in the department truly makes research enjoyable. Thanks to all colleagues and staff at SIM and a special thanks to Sigmund Andersen for his excellent leadership of the department. I would also like to use the opportunity to give special thanks to Professor Roald Bahr for his guidance and encouragement.
An important part of my research work has been to travel to international conferences in
injuries. I have met many new colleagues and it has been crucial for me to be able to gather information first-hand on how these types of injuries are treated elsewhere. One person that has made a particular impression on me is Professor Romain Seil. He has been instrumental in introducing me to the international arena and has been a very important confidant in our research strategies and future endeavors.
I also want to thank the Orthopedic Department at the Coastal Hospital at Hagevik and Kari Indrekvam for making it possible for me during the past year to focus on finalizing this clinical thesis.
A special thanks goes to Akershus University Hospital, which is my new employer and has given me the possibility to continue my work within pediatric ACL injuries. In particular I wish to thank Professor Asbjørn Aarøen and Rune Mikaelsen who have supported my work and believed in our continued research endeavors. Also, I wish to thank Arne Larmo at the Department of Radiology for his contribution to the radiological outcome study.
Lastly, but perhaps most importantly I would like to thank family and friends for their support and encouragement. Thanks to my lovely hosts in the Oslo area during my commuting period the past year, Titti and William in Frognerveien and Julie and Jørn at Kolsås. To my parents, thank you for your endless support and for making it possible for me to fulfill my goals. Also, thanks to my siblings Anders, Leif, Sigurd and Maren. Finally, thank you Peder for your continued support, encouragement and love.
Abbreviations
ACL Anterior cruciate ligament
ACL-RSI Anterior cruciate ligament - return to sport after injury scale ADL Activities of daily living
DAG Directed acyclic graphs
GRADE Grading of recommendations assessment, development and evaluation IKDC International knee documentation committee
KOOS Knee injury and osteoarthritis outcome score MIC Minimal important change
NIH Norwegian School of Sports Sciences SIM Sports Medicine Department
NIMI The Norwegian Sports Medicine Clinic NKLR Norwegian Cruciate Ligament Registry OSTRC Oslo sports trauma research center PAMI Pediatric ACL monitoring initiative PASS Patient acceptable symptom state
PLUTO Pediatric ACL: Understanding Treatment Outcomes
PRISMA Preferred reporting items for systematic reviews and meta-analysis PROSPERO International prospective register of systematic reviews
RCT Randomized control trial
STROBE Strengthening the reporting of observational studies in epidemiology
QoL Quality of life
Preview of thesis
Pediatric ACL injuries are increasing which causes concern regarding long-term knee health.
Clinical decision making is challenging because current evidence is inconsistent and has scientific limitations. The indication for reconstructive surgery for pediatric ACL injured patients is controversial. A common clinical dogma has been to advocate early ACL
reconstruction in order to protect the menisci, despite weak scientific evidence in support.
In this thesis, our research group aimed to develop the best available evidence for managing pediatric ACL injuries. We contributed to a consensus statement on prevention, diagnosis and management of pediatric ACL injuries (Project 1), investigated clinical and radiological outcomes in young adults who had sustained an ACL injury before 13 years (Project 2) and conducted a systematic review of new meniscal tears after ACL injury (Project 3).
In summary, our research has demonstrated that pediatric patients with ACL injuries require a multidisciplinary approach in order to optimize recovery and prevent further injuries. High- quality rehabilitation and continued injury prevention are essential for all, but there is not consensus regarding surgical intervention. However, young adults who sustained an ACL injury in childhood had overall good long-term outcomes following primary non-operative treatment with optional delayed surgery. In addition, there is a very low certainty of evidence regarding the risk of new meniscal tears after ACL injury, and this evidence is not sufficient to support decision making. Thus, our study findings challenge the clinical dogma that all children with ACL injury require early reconstructive surgery.
In conclusion, this thesis supports an individualized treatment approach and suggests that a non-operative treatment approach has a role in management of some pediatric ACL injuries.
Included papers in thesis
1. Ardern CL, Ekas GR, Grindem H, Moksnes H et al. 2018 International Olympic Committee consensus statement on prevention, diagnosis and management of paediatric anterior cruciate ligament (ACL) injuries. Br J Sports Med 2018;52(7):422- 38. doi: 10.1136/bjsports-2018-099060 [published Online First: 2018/02/27]1
2. Ekas GR, Moksnes H, Grindem H, Risberg MA, Engebretsen L. Coping With Anterior Cruciate Ligament Injury From Childhood to Maturation: A Prospective Case Series of 44 Patients With Mean 8 Years' Follow-up. Am J Sports Med
2018:363546518810750. doi: 10.1177/0363546518810750 [published Online First:
2018/11/27]2
3. Ekas GR, Laane MM, Larmo A, Moksnes H, Grindem H, Risberg MA, Engebretsen L.
Knee Pathology in Young Adults After Pediatric Anterior Cruciate Ligament Injury: A Prospective Case Series of 47 Patients With a Mean 9.5-Year Follow-up. Am J Sports Med 2019:363546519837935. doi: 10.1177/0363546519837935 [published Online First: 2019/04/30]3
4. Ekas GR, Ardern C, Grindem H, Engebretsen L. New meniscal tears after ACL injury:
what is the risk? A systematic review protocol. Br J Sports Med 2018;52(6):386. doi:
10.1136/bjsports-2017-097728 [published Online First: 2017/06/26]4
5. Ekas GR, Ardern C, Grindem H, Engebretsen L. New meniscal tears after ACL injury:
what is the risk? A systematic review. (Submitted BJSM April 2019)
Introduction
The anterior cruciate ligament (ACL) plays a key role in knee function, contributing to knee stability by restricting anteroposterior translation and rotation between femur and tibia5 6. An ACL injury is a common injury among athletes in various sports and active individuals in the general population. Young adults between the ages of 16 to 40 years are particularly suceptible7. In this age group, the annual incidence of ACL reconstructions has been
estimated at 85 per 100 000 citizens7. However, ACL injuries also occur in children with open growth plates, which are then identified as pediatric ACL injuries.
There are different types of injuries involving the ACL. ACL injuries include both total and partial intrasubstance ruptures, but do not encompass tibial spine fractures. A tibial spine fracture is an avulsion fracture of the ACL insertion site on the proximal tibia.
In this thesis, we focus on total instrasubstance pediatric ACL injuries. A pediatric ACL injury is defined as an ACL rupture that occurs in a patient who is skeletally immature, which is defined as having open growth plates. Growth plates in skeletally immature patients normally close by the age of 16 years for girls and 18 years for boys, after which, further growth ceases. Large individual variations do however exist for both females and males.
Therefore, in relation to pediatric ACL injuries, chronological age is a poor guide for maturity;
what matters is assessment of the patient’s skeletal age and remaining growth. Determining whether a patient is skeletally immature at the time of ACL injury is very important because it has implications for treatment.
Historically, ACL injuries were considered to be uncommon among children8. In the pediatric population, the tibial spine was regarded as the weakest structure in the ACL complex (ACL and insertion sites). Children were therefore believed to sustain tibial spine fractures rather than intrasubstance ACL injuries. However, just like in adults, one of the main causes of hemarthrosis in the pediatric knee is an anterior cruciate ligament injuriy9. Hemarthrosis is an acute swelling in the knee directly following a knee trauma and is caused by intraarticular bleeding, which indicates a structural knee injury.
The incidence of pediatric ACL injuries is unknown. In recent years, many speculate that the total number of pediatric ACL injures is rising. One reason for this, is that the number of ACL reconstructive surgeries in skeletally immature patients have increased 2 to 3-fold over the last two decades10 11. This trend is alarming due to potential short- and long-term
12 13
increased risk of developing symptomatic knee osteoarthritis in their twenties14. Therefore, strategies to prevent “the old knee” in these young patients is a key aspect in
management15.
Management of pediatric ACL injuries is a controversial topic16. The treatment decision largely relies on traditions as well as patient and surgeon preferences17. The evidence base to guide clinical decision making is limited, and studies with long-term follow-up that include primary active rehabilitation (non-operative treatment) are lacking. There is a certain set of studies which are commonly referred to when discussing treatment approach. These studies are typically cross-sectional and document additional meniscal injuries in children who have early ACL reconstruction or delayed ACL reconstruction 18-22. These studies generally
advocate early surgery to prevent new meniscal injuries because the patients undergoing delayed surgery tend to have higher rates of meniscal tears23 24. Consequently, a clinical dogma has emerged stating that early ACL reconstruction protects the menisci and cartilage in the ACL deficient knee23-25. However, selection bias is a major problem in these studies – children who cope and remain non-operated are unlikely to be included. Thus, the literature has methodological limitations26 and findings may be misleading27.
Evidence regarding treatment of adult ACL injuries is often directly transferred to the pediatric population. However, children are not “just” small adults - they have immature bodies and minds. The open growth plates in skeletally immature children are especially vulnerable during surgery. Therefore, ACL surgery in a skeletally immature patient is not without risks. There are additional challenges in children compared to adults: risk of growth
disturbances28-31, uncertainties regarding graft maturation32 33, small pediatric knee dimensions and high risk of graft failures and other re-injuries34-36. Furthermore, children cannot be expected to comprehend the full extent of their injury or be able to follow the same rehabilitation programs as adults37. Based on these limitations in literature and the inherit risks of surgery, one can postulate that non-operative treatment with active rehabilitation may still be an option if ACL copers exist in the pediatric population. An ACL coper is defined in the adult literature as a patient who is able to compensate for being ACL deficient (lack of ACL function which is normally due to a ruptured ligament) while
maintaining functional knee stability even during pivoting activity38 39. Correspondingly, a non-coper is a patient who experiences instability episodes and cannot maintain functional stability40 of the ACL deficient knee.
In Norway, we reserve early ACL reconstruction for pediatric patients with additional injuries that warrant immediate repair (i.e. a bucket handle meniscal tear, unstable ramp lesion or osteochondral fracture)41. The majority of patients, without additional injuries, are treated non-operatively with primary rehabilitation41 to stabilize the knee through neuromuscular control. Delayed surgery is an option if the child develops either recurrent instability after rehabilitation, sustains additional injuries that require repair (same injuries as listed above), or has unacceptable activity limitations41 (non-coping issues). At 2 years follow-up, this individualized treatment approach has demonstrated good clinical outcomes, low incidence of new meniscal and cartilage injuries, and high rates of return to sport42 43.
Long term-outcomes (clinical, radiological and surgical) following this treatment approach is unknown. This includes the status of these patients’ menisci which is of particular interest for surgical decision making. However, our individualized treatment approach41 is debated and not in line with the current clinical dogma which states that both children and adults should have early ACL reconstruction to protect the menisci and cartilage in an ACL deficient knee16. Meniscal injuries are associated with ACL injuries, either as an injury occurring at the time of ACL injury, or subsequent to the ACL injury as a result of knee instability44-47. In the short-term, meniscal injuries may lead to pain and reduced function. In the long-term, meniscal injury is a strong predictor for knee osteoarthritis12 48. Therefore, protecting or
“saving” the meniscus should be a cornerstone in treatment of both children and adults regardless if patients are treated surgically or not49-53. The concept of saving the meniscus incorporates both meniscal repair of the injured meniscus and prevention of meniscal injuries50. Prevention of new meniscal tears is a treatment goal for all patients with ACL injury49. Consequently, and as we have learned from sports medicine literature on injury prevention54, being aware of the extent of the problem (in our case: new meniscal tears), is important in its prevention. A fundamental question is therefore: “What is the risk for new meniscal tears after ACL injury?”
Aims of thesis
The aim for this PhD thesis was to develop the best evidence for management of pediatric ACL injuries and to evaluate long-term results following the Norwegian treatment approach for pediatric ACL injuries.
We asked the following questions:
1. How to manage pediatric ACL injuries – can we reach a consensus?
2. What is the long-term clinical and radiological outcome following the Norwegian treatment approach for pediatric ACL injuries?
3. What is the risk for new meniscal tears after ACL injury, and what is the certainty of current evidence regarding this question?
Material and methods
Our research team is multidisciplinary and includes surgeons, radiologists and physical therapists with clinical and academic interest in pediatric knee injuries. A central strategy for us has been to adhere closely to published guidelines supported by the International
Committee of Medical Journal Editors (ICMJE). All articles included in this thesis have been published or submitted to high-ranking peer-reviewed journals; either American Journal of Sports Medicine (AJSM) or British Journal of Sports Medicine (BJSM).
In order to answer the study questions, we initiated three separate projects which have resulted in five articles:
Project 1: Consensus statement
(Consensus statement on management of pediatric ACL injuries)
Article 1: 2018 International Olympic Committee consensus statement on prevention, diagnosis and management of pediatric anterior cruciate ligament (ACL) injuries.
(published April 2018, BJSM)
Project 2: Clinical and radiological outcomes
(Long-term clinical outcomes in patients with ACL injury before age 13 years)
Article 2: Coping with anterior cruciate ligament injury from childhood to maturation: A prospective case series of 44 patients with mean 8 years' follow-up.
(published January 2019, AJSM)
Article 3: Knee pathology in young adults following pediatric Anterior Cruciate Ligament injury - A prospective case series of 47 patients with mean 9.5 years follow-up.
(published April 2019, AJSM)
Project 3: Systematic review
(Systematic review of new meniscal tears after ACL injury in children and adults)
Article 4: New meniscal tears after ACL injury: what is the risk? A systematic review protocol. (published March 2018, BJSM)
Article 5: New meniscal tears after ACL injury: what is the risk? A systematic review.
(submitted April 2019, has been peer-reviewed and is currently in revision, BJSM)
Project 1 (Consensus statement):
In project 1, an expert pediatric ACL injury group was initiated and appointed by the Medical and Scientific Commission within the International Olympic Committee (IOC). Twenty-one international experts represented major arthroscopic societies. This international
(representatives from Europe, North America, South America and Australia) and
multidisciplinary group consisting of orthopedic surgeons, an expert in medical ethics and physiotherapists worked together for two years in order to develop the consensus
statement. Initially we defined key topics within management of pediatric ACL injuries through a modified 2-round Delphi process55-57. The IOC organized a consensus meeting in October 2017 in Lausanne to discuss and review the key topics identified in the Delphi process. Prior to the consensus meeting, all participants prepared written reports and presentations to cover these topics. Current literature was reviewed and resulted in a
written consensus statement that was finalized and submitted approximately 3 months after the meeting in Lausanne. All participants contributed significantly to the manuscript. The manuscript was published simultaneously in four peer-reviewed journals (BJSM, Orthopedic Journal of Sports Medicine (OJSM), Knee Surgery, Sports Traumatology and Arthroscopy (KSSTA) and International Society of Arthroscopy, Knee Surgery and Orthopedic Sports Medicine (ISAKOS) journal.
We aimed to present a comprehensive and accessible clinical practice guideline for the multidisciplinary team of clinicians who work with pediatric patients with ACL injuries. The consensus statement was designed to have a clear clinical scope and provide useful clinical tips for the reader. We focused on six clinical questions (related predefined topics listed in brackets):
How can clinicians prevent ACL injuries in children (injury prevention)?
How does the clinician diagnose ACL injuries in children (diagnostic tests and imaging)?
What are the treatment options for a child with an ACL injury? (high-quality rehabilitation, surgical techniques, the pediatric ACL graft)
What are the most important considerations when making treatment decisions?
(skeletal assessment, the decision for ACL reconstruction, risks associated with ACL reconstruction, management of associated injuries)
How does the clinician measure outcomes that are relevant to the child with an ACL injury? (pediatric patient-reported outcome measures)
What are the clinician’s role and responsibilities? (ethical considerations)
Methodology used in Project 1 (Consensus statement):
A Delphi process is a structured method of reaching a consensus in an expert group through at least 2 rounds of questionnaires with feedback between the rounds58 59. This feedback consists of a preliminary anonymous summary of the expert opinions and also includes justifications for these opinions all of which is overseen by a facilitator between each round.
Thus, in the next round the expert panel will view the questions again in light of this
summary60. The rationale for using this process is that the answers or opinions will converge and help form a consensus based on these expert opinions60.
In this consensus statement we used the Delphi process in the following way to address key topics: Clare Ardern (facilitator and first author), Lars Engebretsen (senior author) and Håvard Moksnes reviewed the literature initially to identify the evidence statements that formed the basis for the first round of the Delphi process. A survey based on these evidence statements was created. In the first round, the experts rated the importance of each evidence statement.
They also had the opportunity to suggest statements that they felt had not been covered. The facilitator and senior author collated these ratings. Evidence statements that reached consensus (80% agreement) in the first round were removed from the Delphi process and included in the consensus statement. In the second Delphi round, experts again rated the importance of remaining evidence statements that had not reached consensus in the first round. Statements that reached consensus in the second round was also included in the consensus statement. We discarded remaining statements that did not reach consensus.
Project 2 (Clinical and radiological outcome):
Project 2 was based on long-term follow-up of a prospective case series of 50 children. They sustained a total intrasubstance ACL injury before age 13 years, during skeletal immaturity and with open growth plates confirmed radiologically. The ACL injury diagnosis was verified by clinical examination61, magnetic resonance imaging (MRI)62 and manual knee laxity testing (Manual maximum test, KT 1000, Med-Metric, San Diego, California, USA )63. Patients
who had a tibial spine fracture were excluded (n=2). Included patients were all treated according to our treatment approach41. This approach entailed early ACL reconstruction and meniscal repair if additional injuries such as a bucket handle meniscal tear was present.
Patients without additional injuries, underwent primary active rehabilitation initially.
Delayed surgery was an option for these patients who received primary active rehabilitation if they (1) experienced instability problems, (2) sustained new meniscal injuries or (3) had unacceptable limitations in activity2 3 41 42.
Active rehabilitation emphasizes exercises that target range of motion, neuromuscular control (Figure 1) and muscle strength41. This rehabilitation protocol is supervised by a physical therapist and progresses through four phases. In Phase 1 (the acute phase), the treatment goals are to reduce pain and swelling, and maintain range of motion. Phase 2 focuses on regaining knee function in activities of daily living. Phase 3 focuses on improving knee stability in activities such as running and landings. Phase 4 focuses on continued (secondary) injury prevention41.
Figure 1. Illustration showing full knee extension during one leg stance - an important exercise for quadriceps control1.
For all ACL reconstructions we used a transphyseal ACL reconstruction technique (Figure 2), and the majority had hamstring autografts. Following this treatment algorithm 4 children required early ACL reconstruction due to the presence of additional bucket handle meniscal tears warranting repair, and 46 children underwent primary active rehabilitation. At final follow-up 44 out of 46 patients, who underwent active rehabilitation initially, remained in the study.
Figure 2. Transphyseal ACL reconstruction1.
At mean 8 years follow-up (n=44), we used the following tests and evaluations: functional tests (hop tests and isokinetic strength testing), clinical examination, activity level, surgical history and patient-reported outcome measures (PROMs). PROMs included both the Knee and Osteoarthritis Outcome Score (KOOS)64 and the International Knee Documentation Committee Subjective Knee form (IKDC)65.
In addition, at mean 9.5 years after injury, 47 out of the 50 included patients underwent bilateral knee MRIs and long-leg weight bearing x-rays. Two independent radiologists
assessed these images according to a predefined scoring sheet focusing on meniscal injuries, cartilage injuries and growth disturbances (leg length and alignment).
We prepared two separate research protocols as part of Project 2 (one for each of the two planned articles) in order to allow for thorough methods, results and discussion sections.
The protocols and manuscripts adhered to the Strengthening the reporting of observational studies in epidemiology (STROBE) statement66. Following are methods used for Article 2 (mean 8 years clinical follow-up) and Article 3 (mean 9.5 years radiological follow-up).
Methods used in Article 2 (Project 2, Clinical outcomes):
Patient setting and characteristics: Only patients treated non-operatively initially were included in this study. Four patients who underwent early ACL reconstruction were excluded. Initially, 46 out of 50 patients underwent non-operative treatment. Forty-four patients remained in the study at final follow-up (mean 8 years); 15 girls and 29 boys. Age at injury was mean 11±1.5 years (min-max: 7-13 years).
Follow-up: Follow-up time was mean 8.0 ± 1.7 years (min-max: 5-11 years) since injury corresponding to mean age 19.1± 1.6 years (min-max: 16-23 years). Two patients were lost to follow-up due to lack of time and inability to travel to Oslo. As a result, the study had 44 patients at final follow-up.
Patient-reported outcome measures (PROMs): We included four PROMs; International Knee Documentation Committee Subjective Knee form (IKDC)65, Knee and Osteoarthritis Outcome Score (KOOS)64, Knee Outcome Survey Activities of Daily Living (KOS-ADLS)67 and Visual analogue scale for knee function (VAS). Patients completed the PROMs together with
their parents at previous follow-ups (before they were 16 years), and independently from their parents at final follow-up (older than 16 years). We used the same forms at previous follow-ups (1 and 2 years after injury), but these forms are not validated for children.
Both IKDC and KOOS have acceptable measurement properties64 65 68 69 for our study population70 and are commonly used in the ACL literature71-74. We reported mean scores and individual KOOS scores in a spaghetti plot to explore the variation in the data material.
In addition, in order to present these data in a clinically meaningful way75, we included two concepts with regard to patient-reported outcome measures: patient acceptable symptom state (PASS)76 and minimal important change (MIC)77. PASS is a defined threshold for patient satisfaction and threshold values have been described for both IKDC and the KOOS
subscales76. MIC is the minimal improvement in scores that is clinically important for the patient and has been described for the KOOS subscales77 78. We calculated the proportions of patients who reached these clinically relevant cut-off values.
As well as the PROMs described above, we included questions on activity level (sports participation, number and length of training sessions per week), giving way episodes, re- injuries and surgical history. Because pivoting activity is particularly relevant with regard to treatment decision and re-injury risk, we classified sports participation as level 1 to 4 according to the degree of pivoting2 79 80.
Hop tests: The four hop tests (single-leg hop, triple hop, triple-crossover hop and 6-meter timed hop) described by Noyes81 are functional tests of hop performance. Three of the tests (single hop, triple hop and triple cross over hop) measure hop distance and one test (6- meter timed hop) measures time required to hop a distance of 6 meters. A senior physical therapist demonstrated and supervised the hop tests. We used the hop test data to calculate leg symmetry indexes for the four hop tests. The testing protocol and setting is reported in detail in article 2.
Isokinetic strength testing: We tested isokinetic concentric strength of quadriceps and hamstrings muscle groups for all patients using a dynamometer (Biodex 6000; Medical Systems). Muscle strength was reported in newton meters per kilogram and in leg symmetry indexes. The testing protocol and setting is reported in detail in article 2.
Clinical examination: The senior author examined all patients. The Lachman82 and Slocum83 tests were performed and documented for all patients. In addition, instrumented knee laxity tests (using KT-100063 knee arthrometer) were performed for most patients.
Medical chart reviews: Medical charts were reviewed to verify details regarding surgical history, re-injuries (ACL graft ruptures, meniscal tears, other potential injuries to the index knee) and complications. If patients had undergone treatment at another hospital (n=1) medical chart were retrieved.
Data analysis: We used Predictive Analytics Software Statistics (V24.0 SPSS Inc., Chicago, Illinois, USA) for calculating descriptive statistics for patient characteristics and main
outcomes. We also calculated proportions for dichotomous variables. We used appropriate tests (Student’s t-test or Wilcoxon sign-rank test depending on the data distribution
evaluated by histograms) to compare outcomes at 2 years and at final follow-up.
Methods used in Article 3 (Project 2, Clinical outcome):
Patient characteristics and setting: Both patients who received initial non-operative treatment (n=43), and those treated with early ACL reconstruction (n=4) were included in this study. The patient sample at final follow-up (n=47) included 16 girls and 31 boys with a mean age of 20.6 ±1.9 (min-max: 17-24)). Three patients were lost to follow-up (all had initial non-operative treatment). Two patients declined further participation in the study due to lack of time and travel issues, and one patient did not attend three consecutive MRI appointments.
Radiological imaging: We based our knee pathology evaluation on bilateral knee 3.0 Tesla MRIs and long-leg weight bearing x-rays. These examinations were performed at skeletal maturity, mean 9.5±1.6 years after ACL injury. Diagnostic MRIs and bilateral MRIs (same MRI unit as final follow-up) from 1 and 2 years after injury were also available.
Radiological assessment:
ACL: We adhered to the Van Dyck criteria84 to evaluate the ACL.
Menisci: We described the menisci as ruptured or not, according to the two-slide-touch rule described by de Smet85. If an abnormal signal broke through the articular surface of the meniscus in at least two images, the meniscus was considered ruptured85 86. We adhered to the ISAKOS classification to describe the rupture pattern; longitudinal-vertical, horizontal, radial, flap or complex (more than one tear pattern) 87 88.
Cartilage: We used the International Cartilage Repair Society Classification (ICRS) of cartilage injuries modified to MRI observations89 to describe cartilage injuries. The localisation and size of the lesion were described.
Evaluation of axis and leg-length: We evaluated knee alignment and leg length on long-leg weight bearing radiographs at final follow-up. We used the hip-knee-ankle angle to measure alignment in the lower extremities. This is the angle between the mechanical axis of the femur (line from the centre of the femoral head to the midpoint of the intraarticular notch) and the mechanical axis of the tibia (line from the centre of the inter-eminence area of tibia to the centre of the tibial plafond). We used the mechanical axis in the lower extremities to describe leg length. This is the distance from the centre of the femoral head to the centre of the tibial plafond. The uninjured leg was compared to the injured leg. We based our
reporting on cut-off values in the pediatric ACL literature for knee malalignment and limb length discrepancies: > 3° and > 10 mm respectively28 90 91. Therefore, we reported the number of patients who presented higher values than these cut-off values.
Data analysis: We calculated proportions to describe the main outcomes, but also used Predictive Analytics Software Statistics (V24.0 SPSS Inc., Chicago, Illinois, USA) to calculate
Project 3 (Systematic review):
Our research group designed and conducted a systematic review according to the Preferred Reporting Items for Systematic reviews and Meta-Analysis (PRISMA) statement. We aimed to investigate the risk of new meniscal tears after ACL injury in children and adults. We
registered the study protocol in The International Prospective register of systematic reviews (PROSPERO), and it was later published (May 2017, BJSM). Two reviewers conducted the following in duplicate: article screening, eligibility process, risk of bias assessment and data extraction. The risk of bias was assessed using the Newcastle Ottawa Scale for Cohort Studies92, which we modified slightly to allow a domain-based assessment of bias. We assessed certainty of evidence according to the Grading of Recommendations Assessment Development and Evaluation (GRADE) working group methodology93.
Methodology used in Project 3 (Systematic review):
Patient characteristics and setting: We included studies that evaluated patients with ACL injury regardless of age, sex, activity level or treatment. For inclusion, studies must have confirmed the ACL injury diagnosis by MRI or arthroscopy, provided a baseline meniscal status and reported new meniscal injuries since this same baseline (at least two time points for meniscal evaluation). Studies that reported exclusively on patients with graft ruptures or multi-ligament injuries were excluded.
Newcastle Ottawa Scale: We assessed the risk of bias with the Newcastle Ottawa Quality Assessment Scale for Cohort Studies94. We rated each study on 8 items (domains). We
dichotomized each item as low or high risk of bias, based on predefined decision rules. Two independent reviewers performed the risk of bias assessment. Disagreements were resolved by consensus discussions. The risk of bias assessment informed our data synthesis,
judgement of certainty of evidence and the study conclusion.
GRADE: We evaluated the certainty of evidence for the study outcome (new meniscal tears) using the Grading of Recommendations Assessment Development and Evaluation working group methodology (GRADE) (www.gradeworkinggroup.org)95. GRADE is a tool to develop and present summaries of evidence and is widely used to assess certainty of evidence, and for making clinical practice recommendations93. Components of the GRADE judgement are:
study designs, risk of bias, inconsistency, indirectness, imprecision and publication bias.
Certainty was graded as high, moderate, low or very low according to the GRADE working group95 9693. We created an evidence profile using GRADEpro (GRADEpro GDT: GRADEpro Guideline Development Tool; McMaster University, 2015; Evidence Prime, Inc.;
gradepro.org) and provided an extended rational for our judgement in text.
Data analysis: We used Stata 15 (StataCorp. 2017. Stata Statistical Software: Release 15.
College Station, TX: StataCorp LLC) for data analysis. We calculated proportions by metaprop and planned to compare subgroups by melogit. We used meta-regression to examine the correlation between factors such as time and meniscal tears.
Summary of results
Project 1 (Consensus statement)
There are 10 key guiding principles from the Consensus statement (Project 1) that are important to focus on when considering management of pediatric ACL injuries.
1) Injury prevention programs should be implemented early in pediatric sport teams97-99. Continued injury prevention is important for pediatric patients with ACL injury to address the high risk of re-injury (Figure 3).
Figure 3. Injury prevention exercises in a team setting1.
2) Hemarthrosis in a child suggests structural injury. Performing history, examination and MRI diagnosis is more challenging in children than adults. No single question, test or imaging technique is always reliable to accurately identify a child’s ACL injury. The negative predictive value for ACL injury diagnosis of MRI is higher than the positive predictive value. If the MRI is positive for an ACL injury, the diagnosis cannot always be ruled in61.
3) High-quality rehabilitation is essential for all children with ACL injury regardless of treatment approach. The rehabilitation must be individualized to the patient and their parents. After ACL reconstruction, return to pivoting sports is not advised until at least 12 months after surgery100 101.
4) Due to lack of robust evidence, our group were not able to reach consensus on a superior surgical technique for pediatric ACL patients. Both, transphyseal and physeal sparing
techniques are acceptable techniques and none have proven to be superior.
5) Regardless of surgical technique, the epiphysis needs to be respected. Drilling through the epiphysis should be as vertical as possible and be centrally placed in tibia. Tunnel position may be at expense of anatomical position of the graft. Hardware, bone-blocks or implants should not cross the epiphysis. Tunnels should be filled with soft tissue grafts. In pediatric patients only soft tissue grafts without bone blocks are appropriate to avoid disturbing the growth plate. Allografts should be avoided due to poor clinical outcomes102 103.
6) Documenting the child’s skeletal age and defining remaining growth potential are
important in clinical decision making. A combined clinical and radiological approach may be most appropriate. Standing long-leg x-rays soon after injury should be considered to provide a baseline for axis and leg length evaluation (this would have been useful in our clinical study).
7)Irrespective of technique ACL reconstruction has associated risks. The main risks that clinicians, patients and their caretakers should be aware of are growth disturbances, secondary ACL rupture (graft rupture or in the contralateral knee), poor long-term knee health especially related to meniscectomy, knee stiffness and infection.
8) The pediatric meniscus has higher vascular distribution than adults104 which may be seen as an increased intrameniscial signal on MRI86. Increased intrameniscial signal should not be confused for a degenerative meniscal tear. Consequently, the pediatric meniscus has great healing potential. Therefore, whenever possible, meniscal ruptures should be repaired, not resected105 106.
9)We recommend Pedi-IKDC and KOOS-child to evaluate subjective knee function in children107. Both are derived from adult PROMS and do not have any pediatric-derived components. We do not know what outcome children themselves rate as most important.
10)Treatment decisions in children with ACL injury are challenging; children are vulnerable, evidence is sparse and opinions divided. Protecting the knee and the long-term welfare of the child should be the primary focus for clinicians, but decision making must involve all parties. Shared-decision making is central to informed decision-making. There is no ideal standard that can provides ethical guidance in every situation.
Impact: This consensus statement synthesizes the current evidence in a clinically relevant way. It provides an accessible guideline for clinicians, policymakers and individuals involved in pediatric sports. We highlighted some central aspects of treatment all experts agree upon:
saving the meniscus, rehabilitation, early surgery plus meniscal repair when there are additional injuries that warrant surgery, and continued injury prevention in all patients. The importance of integrated care and a multidisciplinary approach is highlighted. Furthermore, including an ethical perspective is highly relevant in pediatric sports medicine and has encouraged further work on this topic108. The consensus statement also discusses
controversial areas such as treatment approach, describes the scientific limitations in the current literature and implications for future research. This helps to educate readers, stimulating critical thinking and support research initiatives.
Project 2 (Clinical and radiological outcomes), Article 2 and 3
Article 2 investigates how young adults who sustained a pediatric ACL injury cope at a mean 8 years after ACL injury in terms of patient-reported outcomes, function and surgical history.
Key findings: 24 out of 44 patients with initial non-operative treatment (55%) had delayed surgery (mean 15.3 years ± 1.3, (min-max: 13.2-19.5 years)) due to instability (n=20), new injuries (n=2) or unacceptable activity limitations (n=2).
16 out of 44 patients (36%) had meniscal surgery during the study period
9 patients sustained a new meniscal tear to a previously healthy meniscus
One patient sustained a tibial nerve injury in the index knee following ACL reconstruction
One patient was diagnosed with early postoperative infection in the index knee
At the time of clinical follow-up one patient had sustained graft rupture and one patient had clinical graft insufficiency
Mean KOOSsport and recreation subscalescores for patients with ACL reconstruction was 85.6 ±15 (40-100) and for patients with non-operative treatment 86.5 ±19.2 (40-100). For the KOOSsport and recreation subscale, 38 patients (86%) had scores above the PASS threshold. Mean KOOSquality of life(QoL) was 79.3±19.6 (25-100) for patients with ACL reconstruction and 84.2±17.7 (44-100) for patients with non-operative treatment. For the KOOSQoLsubscale, 40 patients (91%) passed the PASS threshold. One patient had a KOOS QoLsubscale value <44.
Mean IKDC scores were 86.3 ±13.7 for patients with ACL reconstruction and 90.6 ± 11.8 for patients with non-operative treatment. Thirty-six of 44 patients (82%) had higher scores than PASS.
For hop tests all mean leg symmetry indices were >90 % except for single hop test for patients with ACL reconstruction. For muscle strength, all mean leg symmetry indices were
>90% except for knee flexion in patients with ACL reconstruction. For quadriceps strength 30 (68%) patients had a leg symmetry index of >90%.
Mean scores for IKDC, KOS ADSL, KOOSQoL and VAS improved significantly from 2 years to final follow-up. For KOOSQoL16 of 44 patients (36%) improved more than the MIC threshold of 18.
Forty of 44 patients (91%) reported regular sports participation; 15 patients reported participating in pivoting sport (8 patients with ACL reconstruction and 7 patients with non- operative treatment), 25 (57%) participated in non-pivoting sport and 4 (9%) were not active in sports. The reasons for not participating in pivoting sports were knee-related for 50% of the patients; either functional or psychological.
Impact (Article 2): This article demonstrated that ACL copers exist in the pediatric
population and that they may have excellent outcome and remain active. However, 27 out of 44 required delayed ACL reconstruction. There were acceptable patient-reported, functional and surgical outcomes in both treatment groups. Primary active rehabilitation with close follow-up and optional delayed surgery may have a role in managing pediatric ACL injuries unless additional injuries warrant early ACL reconstruction and repair.
Article 3 focused on knee pathology in young adults 9.5 years following an ACL injury.
Key findings: 16 patients (34%) sustained a new meniscal injury since diagnostic MRI. This happened in patients with non-operative treatment (n=3), before ACL-reconstruction (n=9) or after ACL reconstruction (n=4). Of these new tears, 6 tears appeared to be healed as they were no longer visible on final follow-up MRI.
14 patients (30%) had signs of a current meniscal tear at final follow-up. Two patients required meniscal surgery due to a lateral meniscus re-tear. The rest of the patients were asymptomatic. Eight of these 14 patients with current meniscal tear had ACL reconstruction and had undergone meniscal repair in the same tear location previously. Three current tears were in patients with non-operative treatment, but were asymptomatic and the tear was considered stable.
In total 20 meniscal tears (baseline tear or new tear) in 17 patients appeared healed because they were no longer visible at final follow-up.
Thirteen patients (28%) had cartilage injuries, mainly to the medial patella and lateral femoral condyle.
Nine patients had contralateral knee injuries (to the meniscus n=2, cartilage n=5 or a subchondral fracture n=1). We detected no contralateral ACL injuries.
At final follow up, 2 patients had a graft re-tear and one had a clinical graft insufficiency.
Six patients showed signs of previous meniscal resection. 4 patients had signs of spur formation on the tibial spine, but osteoarthritis was not observed at weigh bearing surfaces.
Three patients had >5° degrees difference in alignment between the legs. These patients all had ACL reconstruction. One of these patients had a leg shortening on the index side of 3.5 cm, but he also had a leg length deficiency of 2.1 cm diagnosed before injury. In total 2 patients had a lower limb length deficiency of > 1.5 cm on final follow-up (one patient as described above had ACL reconstruction and the other had non-operative treatment). Overgrowth over 1.5 cm was not observed in our
study, but 8 patients had an overgrowth of 1.0-1.5 cm. However, of these 6 patients had non-operative treatment.
Impact (Article 3): Based on a series of bilateral knee MRIs in all patients, the incidence of new meniscal tears was 34% and the prevalence of current meniscal tears was 30%. A high proportion of baseline or new meniscal tears healed. No patients had signs of osteoarthritis.
This study demonstrates that it is possible to cope with a pediatric ACL injury; to remain active and have intact menisci nearly 10 years after ACL injury. However, risk of meniscal injuries and other intra-articular injuries remain a concern in this group of patients regardless of treatment approach.
Project 3 (Systematic review)
Key findings: 75 studies (11707 patients) were included for systematic review; 54 for quantitative analysis. Six studies included only pediatric patients (defined as skeletally immature or under 16 years at the time of ACL injury). The rate of new meniscal tears varied from 0-52%. Heterogeneity was very high (I2 93%) and precluded meta-analysis. There was a high risk of bias in the included studies, especially selection bias, misclassification bias and detection bias. Outcome reporting and detection varied, and may contribute to bias. Often new meniscal surgeries were reported only, and source of information was typically medical charts. The follow-up time and rate were variable, but acceptable for most patients.
Acceptable follow-up was defined as minimum 2 years (75% of studies) and acceptable follow-up rate >80% (55% of studies). Effect of confounding i.e. activity level on effect
estimate is unknown. Many studies (36%) included some potentially skeletally immature patients. Studies were predominantly retrospective and small. Thirteen studies (17%) assessed all patients for new meniscal tears with an appropriate method (MRI or
arthroscopy) and of these, only 2 studies included an independent evaluator. According to our GRADE assessment the certainty of evidence was very low.
Impact: The rate of new meniscal tears varied from 0-52%. Heterogeneity precluded meta- analysis. Included studies were limited by bias and the certainty of evidence was very low.
Therefore, there is a weak knowledge base for clinical decision making.
How study results address the three research questions
1. How to manage pediatric ACL injuries – can we reach a consensus?
In the consensus statement (Project 1), pediatric ACL experts agreed that there is a need for high-quality rehabilitation and continued injury prevention in all patients, to prevent further knee injuries. The consensus statement highlighted the importance of saving the meniscus.
Children have a high healing potential, and the injured pediatric meniscus should be repaired rather than resected whenever possible. In line with the concept of saving the meniscus, there was agreement regarding performing early ACL reconstruction in patients with additional injuries initially that need immediate repair (i.e. bucket handle meniscal tear, unstable ramp lesion and/or osteochondral defect). However, there was no consensus regarding indication for ACL reconstruction in the pediatric patients without additional injuries requiring immediate repair. Some surgeons advocate early surgery in all patients to protect the meniscus and cartilage, others suggest a trial of active rehabilitation initially and
reserve ACL reconstruction for non-copers (those with recurrent instability after
rehabilitation, who sustain additional injuries that require ACL reconstruction, or experience unacceptable activity limitations).
Our clinical studies (Project 2) which follow our treatment approach, provide both clinical and radiological results that should be considered when evaluating treatment approach. This is described in detail below. Our systematic review (Project 3) is also relevant, because it demonstrates that the knowledge background regarding risk for new meniscal tears after ACL injuries is low. However, Project 2 and Project 3 do not give an answer to what is the best treatment approach for pediatric ACL injuries. However, the current clinical dogma may not be evidence-based.
2. What are the long-term clinical and radiological outcomes following the Norwegian treatment approach for pediatric ACL injuries?
Our two clinical outcome studies (Article 2 and Article 3, Project 2), demonstrated that non- copers exist among pediatric patients with ACL injury, nearly 10 years after ACL injury. After mean 8 years follow-up (Article 2), 24 out of 44 patients who underwent active rehabilitation initially, had undergone ACL reconstruction - primarily due to instability. Our results
indicated symmetrical strength in knee flexors and extensors when we compared the limbs, and symmetrical hop performance. All tests, except one hop and flexor strength, for patients with ACL reconstruction had a leg symmetry index (LSI) consistently above 90% on average.
All patients (n=44) did strength testing at final follow-up, but 2 could not perform hop tests
high, and the majority of patients had scores above the defined thresholds for patient acceptable symptom states (PASS). Nine out of every ten patients were still active in sports, although two-thirds had reduced their activity level to a non-pivoting sport.
From time of injury up until mean 9.5 years follow-up (Article 3), 16 out of 47 patients had sustained a new meniscal tear to a previously healthy meniscus. Six of these tears had healed (in 6 patients) at final follow-up. Of these 6 tears, 3 healed after surgery. The increased vascularity in the pediatric meniscus and the assumed superior healing potential we elucidated in the consensus statement is noteworthy in regard to this.
In conclusion, 39 % (17/44) of patients who underwent primary active rehabilitation at index ACL injury, remained non-operatively treated. These patients coped remarkably well and had uninjured menisci nearly 10 years after their ACL injury. The 3 remaining patients with non- operative treatment, showed signs of a stable meniscal tear, but were asymptomatic.
However, in the complete cohort, which also included those who had undergone early surgery, 4 out of 47 patients required early ACL reconstruction and meniscal surgery in childhood and 23 had delayed ACL reconstruction. Delayed surgery postpones the time of surgery, which may allow for greater skeletal maturity at time of surgery, at which one assumes that a more predictable and safe result can be achieved. In this study, outcomes were still acceptable, and rates of new meniscal tears were lower than described in previous reports109110 111.
3. What is the risk for new meniscal tears after ACL injury and what is the certainty of current evidence?
In the systematic review (Project 3), the rate of new meniscal tears varied substantially between studies (0-52%). The high heterogeneity (I2=93) precluded meta-analysis. We could not fully explain this heterogeneity, but both clinical (i.e. age, activity level, treatment) and methodological factors (study design, study setting, outcome assessment/detection and outcome reporting) likely contributed. We found that the quality of evidence regarding new meniscal tears after ACL injury is very low. In summary, the literature is limited by inferior study designs, bias (especially selection, misclassification and detection bias), inconsistency and indirectness. The scientific limitations in the literature and the low certainty of estimates suggest that we do not have robust evidence to determine what is the best treatment
approach and thus to guide decision making.
Our clinical studies illustrate how more meniscal tears are detected in studies in which all patients are examined with MRI, compared to detection by history and medical chart reviews alone. In article 2, 9 new meniscal tears were detected, whereas in article 3 where all patients were assessed by bilateral MRI, 16 new tears were detected. Our article 3 was included in the systematic review and was 1 of 2 studies out of 75 studies which included meniscal assessment by MRI or arthroscopy in all patients evaluated by an independent evaluator. The weakness in the current literature regarding meniscal tears and timing of surgery was discussed in the consensus statement.
Discussion of main findings
One of the main findings of this thesis was the lack of consensus regarding the best
approach to treating pediatric ACL injuries. Experts agreed on the importance of saving the meniscus in the management of pediatric ACL injuries and consequently the need for high- quality rehabilitation and continued injury prevention in all patients to reduce the risk of further injuries. Furthermore, early ACL reconstruction and meniscal repair is recommended in those with repairable additional injuries to optimize meniscal healing. However, a
common treatment approach for all patients could not be agreed upon. There were conflicting opinions regarding the indication for ACL reconstruction in pediatric patients without additional injuries warranting surgery. The consensus statement highlighted the need for future high-quality multicenter studies. This idea was further encouraged in all studies included in this thesis.
We demonstrated that ACL copers exist in the ACL injured pediatric population. The majority (17 out of 20) are still active in sports and have healthy menisci nearly 10 years after their ACL injury. However, non-operative treatment is not acceptable for all pediatric patients. In our patient cohort, 4 out of 50 patients required ACL reconstruction initially due to bucket handle meniscal tears. In addition, between time of injury and final follow-up 24 out of 44 patients who initially received non-operative treatment had undergone delayed ACL
reconstruction, mainly due to knee instability. Regardless of final treatment, both treatment groups had good patient-reported outcomes, symmetrical knee function and a lower rate of new meniscal injuries than previously reported following non-operative treatment109-111. We
assessed all patients for meniscal injury (outcome) with MRI which is an acceptable measure for this outcome112-114. At final follow-up, 91 % of patients participated in sports regularly (including 2 competitive athletes; one alpine skier with ACL reconstruction and one elite level cross-country skier with non-operative treatment). However, two-thirds had reduced their activity level to a non-pivoting sport.
We found that the rate of new meniscal tears after ACL injury varied between 0-52% among all patients (pediatric and adult). The high heterogeneity (I2 = 93%) precluded meta-analysis.
Risk of bias was generally high especially for selection, misclassification and detection bias.
Certainty of evidence regarding new meniscal tears after ACL injury was very low and not appropriate for guiding clinical decision making. There are very few studies that include ACL copers, although our clinical studies (Article 2 and 3) have demonstrated that nearly half of pediatric patients with ACL injury may be copers. Studies on outcomes following non- operative treatment often include non-copers scheduled for surgery115-117. Furthermore, surgical series tend to base their reporting of meniscal tears on new meniscal surgeries at the study center. As a result, numbers of new meniscal tears may be underestimated because only those who return for surgical treatment are recorded.
Surgical indication
Surgical indications for pediatric ACL injuries continue to be debated. However, the need to preserve the pediatric meniscus is unquestionable – the meniscus should be protected and repaired whenever possible49 50. The reason for this is that the meniscus status is an
important predictor for long-term osteoarthritis118-120. A systematic review concluded that the 10-year rate of osteoarthritis following combined ACL and meniscal injury in adults was 21-48% compared to 0-13% following isolated ACL tears118. In a systematic review from 2019 ACL injury increased the odds of knee osteoarthritis at 10 years 4 times compared to in an uninjured knee, but an additional meniscal injury increased the odds 6 times. Other studies have supported these findings48 121 and concluded that meniscal resection in particular is a predictor for knee osteoarthritis48 122.
The interpretation of the concept “saving the meniscus” may be key to understanding the treatment controversy regarding this topic. Those who advocate early surgery do so in order to protect the menisci from further damage18 23 24. A number of studies in both children and adults support this approach, but these studies have scientific limitations, especially due to selection bias19 21-24 123. Most of these studies compare the presence of additional injuries (meniscus and cartilage) in patients who have early or delayed ACL reconstruction (different definitions are used). These studies are integrated in current literature and often referred to, but may contribute to misconception27. A group of patients who all received delayed ACL reconstruction may not be a representative sample of all non-operated patients. They are likely to suffer from non-coping issues that may increase the chance of having sustained subsequent injuries, whereas non-operated patients who cope are typically not included in these studies. At the same time, in our systematic review we found that time is correlated with an increased risk of new meniscal injuries regardless of treatment. These three factors may contribute to a higher rate of new meniscal injuries in the delayed surgery group. This
possible over-estimation may mislead clinicians. Thus, early ACL reconstruction may protect the meniscus, but we do not know in which patients this is necessary.
On the other hand, clinicians who do not advocate early surgery in all pediatric ACL injured patients may have a different perspective and may pay more attention to the limitations in the literature and the possible negative effects of surgery. Thus, when balancing the
uncertain increased risk of new meniscal tears without surgery with the risks associated with surgery, a trial of non-operative treatment with active rehabilitation and activity
modification (until functional124 and/or time based milestone100 are met) may seem like a viable option. This is in line with our treatment approach in Norway which was developed many years ago and published in 201241. This is still the standard of care for pediatric patients with ACL injury in Norway. This individualized treatment approach was debated at the consensus statement, but there was consensus that early ACL reconstruction is
appropriate for the subset of patients with meniscal or other additional injuries that warrant surgery.
Non-operative treatment
To operate or not to operate has been discussed125, but maybe we should rather discuss surgical indication? Discussing surgical indication may be more clinically relevant than discussing non-operative or surgical treatment. Strict non-operative treatment without the option of having surgery is unethical and rarely an option and to our knowledge not
described126-128. Our systematic review confirmed that there are few studies on non-
