In both the medical and lay
press, much has been written about athletic knee injuries in adults. Most
of us have at least some familiarity with tears of the anterior cruciate
ligament (ACL) and how they affect the season, and sometimes the career
of professional, collegiate or local high school athletes. Newspapers
often quote team physicians and include reports of MRI results after a
professional or other high-profile athlete suffers a knee injury. Many
ski vacations have been cut short by a bad fall and subsequent visit to
an orthopedic surgeon back home, resulting in a diagnosis of ACL tear.
Fortunately, the orthopedic community has extensive collective experience
in treating this problem – patterns of injury are understood, the
natural history is well defined and surgical techniques continue to be
perfected. Despite some ongoing controversy regarding the technical aspects
of the surgical reconstruction, most patients who suffer an ACL injury
have a predictable outcome from surgery or learn to maximize their function
without surgery.
Only recently, however, have
surgeons begun to fully understand the nature of ACL injuries in skeletally
immature athletes. Specialized study of ligament injuries in children
is necessary because of the unique biology of growing bones and ligaments.
Longitudinal growth in the child takes place at the ends of the long bones,
with particularly rapid growth occurring around the knee at the end of
the femur (thigh bone) and top of the tibia (shin bone). Growth plates
(where growth occurs) are comprised of a sliver of specialized cartilage
through a cross section of these bones near each joint. The bones literally
increase in length and grow away from these areas. ACL surgery presents
unique issues in adolescent or skeletally immature athletes because the
reconstructive surgery involves drilling tunnels across the growth plates
and placing a graft (replacement ligament) into the knee joint through
these tunnels.
In adults, who have completed
skeletal growth, the passage of the graft does not affect the growth plates
adversely as they have already closed and growth has ended. In children,
however, this part of the surgery can theoretically injure the growth
plates, resulting in a shortened or angulated leg compared to the opposite
limb that continues to grow normally. The degree of the deformity depends
upon the extent of injury to the growth plate and the amount of growth
remaining. In other words, if damage to the growth plate occurs, younger
patients are at risk for greater degrees of growth disturbance.
Your child’s orthopedic
surgeon will take all of these biologic issues into consideration when
counseling him or her on treatment options for an injured knee. Several
variations on traditional surgical techniques have been devised in an
attempt to minimize disruption of the growth plates during surgery. While
no surgery is risk-free, choosing the proper technique to reconstruct
the ligament at the appropriate time in the child’s growth curve
should lead to predictable results in treating ACL injuries.
A history of a twisting injury
associated with an audible “pop” followed by swelling of the
knee raises suspicion for a ligament tear. When visiting an orthopedic
surgeon for a knee injury, your young athlete should expect a thorough
examination of the knee followed by x-rays and, if there is suspicion
of an ACL tear, a referral for an MRI study to verify the diagnosis.
Once the diagnosis is confirmed,
then the process of decision-making begins. It is very important that
the treating physician have significant experience in treating ACL injuries
in immature athletes. As outlined above, your physician will help you
to assess the risks and benefits of the various treatment options for
a torn ACL. The major decision point revolves around conservative treatment,
including supportive exercise and activity modification, versus surgical
reconstruction. This is a decision that must be made by the patient, parents
and physician together as the treatment depends very much on the young
athlete’s ago, biology, goals, motivation and education.
