Prospective Evaluation of Sport Activity and the Developemnt of Femoroacetabular Impingement in the Adolescent Hip

Femoroacetabular impingement (FAI) is a recently described condition that
causes hip pain and can lead to the development of
osteoarthritis of the hip later in life. Some cross-sectional studies have
estimated that the prevalence of hip impingement ranges
from 14-17% among asymptomatic young adults to almost 95% among competitive
athletes. FAI occurs as a result of a size and
shape mismatch between the femoral head (ball) and the acetabulum (socket). FAI
is typically classified into 2 subtypes; cam-type
(a misshaped femoral head / cam morphology) or Pincer type (an over covered or
deep socket). Most adult patients (18+ years)
have a combination of both types of impingement. With FAI, the abnormal femoral
head and acetabular rim of the hip joint collide or
*impinge* during movements such as hip flexion and rotation. Typically,
patients with this condition experience hip pain and loss of
hip function. The development of hip pain in this manner serves as an indicator
for early cartilage and labral damage, potentially
resulting in hip osteoarthritis.

The number and diagnoses of FAI has recently risen across all age groups, but
it has been especially notable within paediatric and
adolescent populations. In the adult, FAI is most commonly attributed to an
*idiopathic anatomic variant*. In the paediatric
population, implicated causes of FAI have included genetics, subclinical
paediatric hip disease, and stresses to the hip joint from
high-intensity, repetitive activity typically attributed to certain sports.
According to Packer et al., there is no definitive evidence that
FAI is transmitted genetically, and in otherwise healthy children, there is
growing evidence that FAI, particularly with cam
morphology, has a higher prevalence in athletes who performed at a high level
during adolescence.

Sports and the Development of FAI in the Paediatric Population
Over the past 20 years, sport injuries among children have dramatically
increased, where more than 38 million young athletes
participate in organized sports annually in US and of those, 3.5 million that
receive medical treatment for their injuries are 14 years
and younger. High impact and high intensity activity common in many sports have
the potential to cause hip damage, especially
during physeal closure in young children. Research is needed to determine *how
much is too much* sport activity in order to
advocate for the young who cannot easily protect themselves from excesses. This
concern has been highlighted in publications
addressing the potential deleterious impact of early sport specialization in
young athletes.

High impact activities in combination with intensity of various kinds have been
shown to affect the developing femur. Among
children, open physes and growing cartilage make them more susceptible to
injury and shear forces that can result in premature
physeal arrest, apophyseal avulsion fractures, and chondral injuries. A higher
prevalence of cam morphology (>50%), both
symptomatic and asymptomatic, has been shown in adolescent athletes that play
ice hockey, basketball, and soccer when
compared to controls that did not play sports. These sports involve repetitive
deep flexion, flexion-adduction or extension-abduction
movements, which bring the cam lesion on the femoral head or the pincer lesion
on the acetabulum into conflict. Therefore,
participating in high impact sports during growth likely plays an important
role in the development of a cam deformity. This is
concerning given the increasing trend toward year-round participation in youth
sports with early specialization.

Preliminary Studies
Most studies in the current literature that evaluate the relationship between
sports and the development of FAI are relatively small,
retrospective case-controls. There are 2 recent systematic reviews on this
topic that overlap in primary study data. There were up to
4 studies included across both reviews that were published since 2011 and
evaluated varying sports and levels of training intensity
through a meta-analysis. Both reviews describe an increased risk of development
of a cam morphology in athletes that play ice
hockey, basketball, soccer, and other jumping sports. In addition, adolescent
males that train for these sports at least 3 times per
week were at a greater risk than their non-athletic counterparts of developing
femoral head-neck deformities associated with FAI.

The studies in these reviews were predominantly cross-sectional in design, with
small sample sizes (wide confidence intervals), and
did not describe changes in hip morphology during the critical phase in hip
development and maturation. New evidence
demonstrates conflicting results regarding how and when primary cam-type FAI
develops in relation to skeletal maturity. Accordingly,
the current literature notes the need for longitudinal or prospective MRI
studies to understand the etiology of primary FAI
development to identify preventive strategies, delineate radiographic values,
define specific indications for operative management,
and examine long-term outcomes to determine optimal management.

Significance
As FAI is diagnosed most frequently in athletes, and it is estimated that 30 to
45 million adolescents age 6-18 years old are involved
in sports, it is becoming imperative to identify factors that may predict its
development, study treatments, and improve outcomes.
The presentation of a cam morphology can include hip pain, loss of function,
and the need for surgical treatment along with its
potential complications (complication rates of hip arthroscopy in children and
adolescents range from 1.8-12.9%). Considering that
research has demonstrated the connection between FAI and osteoarthritis in
adulthood, potentially leading to the need for total hip
replacement, it has now become critical to mitigate the risk of developing cam
morphology at a young age. A prospective evaluation
of the impact of sport activity, and the increasing tendency for sport
specialization, in the very young athlete is important to protect
the millions of adolescents involved in sports that may be at risk of
developing FAI

Study Objective 1
To determine if the level and type of sport activity is associated with the
development of hip deformities in the paediatric population
at 2 years. Intensive sport training and specialization has been implicated in
the development of abnormal hip morphology in
adolescents. Certain sports (e.g. soccer, basketball, ice hockey, football)
have also been identified as placing excessive stress on
the hip and surrounding soft tissues, which bring the cam morphology on the
femoral head and the pincer morphology on the
acetabulum into conflict. We hypothesize that: 1) Participants engaging in high
sport activity levels will have a higher prevalence of
cam morphology diagnosed through three dimensional magnetic resonance imaging
(3D MRI) of the dominant hip compared to
non-athletes in the same age group (controls) at 2 years; and 2) Participants
with specialized activity in certain sports (e.g. soccer,
basketball, ice hockey, football) will have a higher prevalence of cam
morphology diagnosed through MRI compared to non-athletes
at 2 years.

Study Objective 2
To determine if the presence of hip deformity is associated with varying hip
function and health-related quality of life (HRQL) in the
paediatric population at 2 years. Hip morphology will be diagnosed through MRI
of the dominant hip to avoid radiation exposure to
the developing hip. For any impingement morphology (cam or pincer) identified,
not all subjects may be symptomatic. We
hypothesize that: 1) Participants diagnosed with cam morphology will have
decreased function and HRQL at 2 years compared to
those without; and 2) Participants with symptomatic cam morphology will have
the lowest function and HRQL scores at 2 years
compared to asymptomatic individuals.

This prospective cohort study of 200 athlete and non-athlete participants
(around 100 per group) between the ages of 12 and 14.
Participants will be recruited from experienced hip surgeons and sports
medicine researchers at multiple international clinical sites.
Participants will be evaluated clinically and radiographically(MRI) at baseline
and again at the 2-year follow-up.

There are no known risks involved in our study, aside from the inconvenience of
completing questionnaires and wearing a GPS watch. The magnetic
resonance imaging does not involve any radiation and therefore the study
procedure is safe for children. Participants will be made
aware of potential risks in the informed consent form and during the consent
process