Epidemiology of Pediatric and Adolescent Anterior Cruciate Ligament Injury

Peter D. Fabricant

Emily R. Dodwell

Robert G. Marx

INTRODUCTION

There has been an increased interest in pediatric and adolescent anterior cruciate ligament (ACL) injury due to the recent spike in rates of diagnosis and treatment. With nearly 70% of children in the United States playing team sports, there has been a dramatic rise in participation in competitive athletics year-round. This, along with increased levels of competition and sports specialization in addition to improved recognition of ACL injury, has led to a significant increase in the number of ACL injuries diagnosed in skeletally immature patients.¹,² Historically, treatment has largely been nonoperative for fear of injury to open physes. Currently, however, with improved treatment strategies, the standard of care has become reconstruction to prevent further cartilage and meniscal damage.³,⁴

Paramount to the understanding of ACL injury in children and adolescents is the recognition of the epidemiology of ACL injury in this age group as well as risk factors for ACL injury and strategies developed to prevent injury. The purpose of this chapter is to describe the epidemiology of ACL injury and reconstruction in children and adolescents as well as briefly address the risk factors for injury, which is described in greater detail throughout this section of the textbook. In addition, this chapter discusses the costs and effectiveness of ACL injury screening programs as well as ACL injury prevention programs, as these represent substantial interventions toward injury prevention in children, adolescents, and young adults.

EPIDEMIOLOGY OF ANTERIOR CRUCIATE LIGAMENT INJURY AND RECONSTRUCTION

Historically, treatment of ACL injury in the skeletally immature has largely been nonoperative for fear of injury to the physes in the growing skeleton. Currently, with improved treatment strategies, the standard of care has become reconstruction to prevent further cartilage and meniscal damage. Recent studies have shown that nonoperative management of ACL tears in the skeletally immature patient often results in poor outcomes³,⁵,⁶ and that treatment delays increased the risk of further meniscal and cartilage damage.³,⁴ Further, a recent meta-analysis reported that operatively managed ACL tears in children and adolescents have a high rate of good or excellent knee function with average Lysholm scores⁷ of 96. This, coupled with improved surgical technique for ACL reconstruction in the skeletally immature, likely accounts for much of the recent increase in the rate of ACL reconstructions in this age group.

To date, there are very few large cohort and population-based studies on ACL injury in the skeletally immature athlete. A study that sampled 2,133 children aged 5 to 17 years, drawn from a cohort of nearly 140,000 patient visits treated over 9 years in a sports medicine division at a large academic pediatric medical center found that ACL tears comprised 9.4% of all presenting injuries.⁸ The percentage was slightly higher in the 13- to 17-year-old age group when compared to those aged 5 to 12 years old.

The largest population-based study to date on the epidemiology of ACL reconstruction in children and adolescents was performed in New York State by Dodwell et al.⁹ A billing and coding discharge database was used to identify ACL reconstructions in patients aged 3 to 20 years at the time of surgery over a 20-year period, from 1990 to 2009. The study noted that the rate of ACL reconstruction has increased steadily over the 20- year interval studied, from 17.6 to 50.9 per 100,000 population (Fig. 2.1). The authors noted that the rate of ACL reconstruction was 15% higher in boys than in girls. Although this study is the only existing population-based study to evaluate the rate of pediatric and adolescent ACL injury, its main limitation is that it quantified ACL reconstruction surgeries, which does not account for some ACL tears that are undiagnosed or treated nonoperatively. Despite this limitation, the study provides convincing evidence of the increase in rate of ACL tears in children and adolescents. As of 2009, the highest rate of ACL reconstruction was noted in 14- to 20-year-olds, with the greatest peak at age 17 years (Fig. 2.2).

Figure 2.1. Rate of ACL reconstructions in the pediatric population (aged 3 to 20 years) in New York State from 1990 to 2009. (Adapted with permission from Dodwell ER, Lamont LE, Green DW, et al. 20 years of pediatric anterior cruciate ligament reconstruction in New York State. Am J Sports Med. 2014;42[3]:675-680.)

RISK FACTORS FOR ANTERIOR CRUCIATE LIGAMENT INJURY

In order to understand the risk factors for pediatric and adolescent ACL injury, one must evaluate elements that are both intrinsic to the patient as well as external factors.¹⁰,¹¹ Although some intrinsic risk factors are not controllable by the adolescent, many intrinsic and all extrinsic risk factors are modifiable to some extent.

Intrinsic Risk Factors

Intrinsic risk factors are variables that are inherent to the patient and include factors that are both controllable (e.g., playing style, training and preparation, skill) as well as those that are not under the athlete’s control (e.g., age, previous ACL reconstruction, mechanical alignment, soft tissue laxity, hormonal differences, anatomic variation in ACL morphology and intercondylar notch geometry).⁹,¹⁰,¹¹,¹²,¹³,¹⁴,¹⁵ Risk for ACL injury is increased by athletic activity that requires pivoting, deceleration, and landing and can be in part related to biomechanical forces including posture, alignment, and differential muscle activation.¹⁶ These have led to the development of strength and conditioning programs, which have been designed to mitigate these risk factors and prevent ACL injury and are discussed later in this chapter.¹²,¹⁷,¹⁸,¹⁹,²⁰,²¹,²²,²³,²⁴

Figure 2.2. Rate of anterior cruciate ligament (ACL) reconstructions in 2009 compared with 2009 New York State (NYS) population by age. (Adapted with permission from Dodwell ER, Lamont LE, Green DW, et al. 20 years of pediatric anterior cruciate ligament reconstruction in New York State. Am J Sports Med. 2014;42[3]:675-680.)

Of the intrinsic risk factors, gender differences have drawn the most interest in the scientific literature. Clinical studies have noted increased rates of ACL tears in young female athletes when compared with males, in the order of 2 to 10 times greater.²⁵,²⁶,²⁷,²⁸,²⁹ Recent large cohort and population-based studies, however, have noted a greater frequency of ACL reconstruction surgery in males compared to females, with a rate of ACL reconstruction up to 15% higher in boys than in girls.⁹,³⁰ Although the absolute number of males with ACL reconstruction is greater than that of females, females have a higher rate of injury per athletic exposure.¹,²⁷,²⁸,²⁹,³¹ On average, males experience more athletic exposures than girls, thus leading to a greater number of ACL injuries despite a lower risk per athletic exposure.²⁷,³²,³³,³⁴,³⁵,³⁶

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