July 29, 1998

ACL: The crucial cruciate
The sports world seems to thrive on acronyms -- from
NCAA and NBA to ERA and PAT -- but perhaps none of
them creates a greater sense of gloom and doom among
athletes, coaches, and fans than the three letters
ACL: anterior cruciate ligament. A torn anterior
cruciate ligament -- also known as "blowing out" a
knee -- usually means at least a six-month sentence
on the sidelines and weeks upon weeks of therapy. But
there's good news, too: Advances in surgical
techniques have greatly lessened the trauma of the
injury's repair and can very often restore the knee
to its previous competitive condition. So what in the
past might have proved a career-ending catastrophe
can frequently be just an inconvenient layover. Dr.
Tarek O. Souryal, former team physician for the
Dallas Mavericks and a member of the Association of
Professional Team Physicians (PTP), was involved in
groundbreaking research during the late 1980s and
early '90s that identified key predisposing factors
in ACL tears. In this Q&A, he outlines the basics of
the injury and its diagnosis and treatment.

What exactly is the ACL, and what role does it play
in sports?

Dr. Souryal: The ACL is one of the four main
ligaments in the knee and is the primary stabilizer.
It's the smallest of the four, but it serves the most
important function: It stabilizes the knee for
rotational movement. When you cut to change
direction, that's when the ACL comes into play. For
most straightforward activities, such as jogging, the
ACL isn't involved. The most common sports in which
we see ACL tears include soccer, basketball,
football, and tennis. Back in the old days, before we
really understood the function of the ACL, having an
ACL injury used to be called a "trick knee." The
reason a knee without an intact ACL gives out
occasionally is that it's lost that stabilizer, and
although it does not give out every single time, you never know when it will
and when it won't.

This injury is rampant. There are between 250,000 and 300,000 ACL injuries
per year, and they're almost exclusively happening to athletes. The chances
of a nonathlete suffering an ACL injury are 1,000 to 1.

How do ACL tears occur?

Dr. Souryal: The most common mechanism of injury is non-contact and caused
by cutting. You're running along, you plant to change direction, and your
knee buckles. The next most common is a contact injury such as being clipped
from behind in football and hockey. A skier can also tear an ACL when the
ski catches awkwardly in the snow or the carving of the ski twists the leg.

Are certain athletes predisposed to the injury?

Dr. Souryal: My study was the first to describe the link between bony
anatomy and ACL tears and to describe the way of measuring it. We found that
a certain segment of the population has a bone structure that predisposes
them to an ACL tear. The ACL and posterior cruciate ligament (PCL) live in a
tunnel at the end of your thigh bone. If that tunnel is very narrow (which
you can detect by X-ray), then there's no room for the ACL to maneuver in
cutting activity, and those people are at 26 times more risk of tearing an
ACL.

In 1992, we took X-rays of 1,000 high school athletes' knees and followed
them for the next two years. Whenever a player went down with an ACL injury,
we looked at his notch. And it was phenomenal: The kids who were blowing out
their ACLs all had those narrow notches. We stopped the study early because
the numbers were so dramatic. I'm sure that there are a lot of factors that
go into ACL injuries -- the notch is just one of them -- and the biggest
question right now is, what lives inside the narrow notch? Does a small ACL
live in a narrow notch and tears because it's never had the room to grow
properly? Or does a normal-sized ACL live in the small notch and ruptures
because it doesn't have the room? We don't have answers because we're not
doing surgery on uninjured people and measuring their ACLs.

As a next phase, we're waiting for MRIs to get a bit clearer to allow us to
measure the normal ACLs in the notches. Maybe in the next couple of years,
we'll be able to answer the question. If it is a normal-sized ACL in the
notch, then maybe we can go in there surgically and widen the notch, and
perhaps save that person from an ACL rupture. But if it's an underdeveloped
ACL in that narrow notch, you can widen the notch all day long and you're
not going to fix it. Once we get this question answered, maybe we can do
something about people with the predisposition.

In '92, we found that girls have proportionally narrower notches than boys.
Does that have anything to do with the fact that ACL injuries are epidemic
among females? I don't know, but I certainly do think that it's one factor.
Other factors have to do with muscle development and neuromuscular
coordination, because the boys are encouraged to be active athletically
almost from birth. They may develop better neuromuscular coordination and
therefore are somewhat protected as they get into high school and college.
Girls are not necessarily directed into athletics early in life, and as they
become more athletically active in their teens, they may not have the
neuromuscular coordination that boys have. The bottom line is that nobody
knows for sure. But there's definitely a higher incidence of ACL ruptures in
female athletes than in male athletes.

How is a torn ACL diagnosed?

Dr. Souryal: By medical history, examination,
and nowadays MRI scans. History and
examination in most cases are sufficient. MRI
scans are only indicated when you really
cannot quite distinquish whether it's torn or
not. We fans have been programmed through
following the NFL, NBA and other sports that
when an athlete has an injury, he gets an MRI.
In the case of ACL tears, it's nice to get an
MRI, but it's not mandatory.

Lachman's test and the pivot shift test are
used. Both are about 90 percent diagnostic.
Lachman's test like a drawer test, but instead
of the knee being bent 90 degrees, it's just
slightly bent, and you attempt to pull the
tibia forward with one hand while holding the
thigh just above the knee with the other hand.
If the ACL is intact, the tibia doesn't come
forward. If the ACL is torn, it keeps coming.
That test is very diagnostic and conclusive
when performed by an expert.

How are ACL tears treated?

Dr. Souryal: The goal of treatment is to never
let the knee go out of place again. When you
tear your ACL, by definition the knee buckled.
Every time that happens, it can do cartilage
damage, which is bad from a long-term
perspective. Cartilage is there to protect you
from arthritis. If your knee is constantly
giving out, you're slowly chewing away pieces
of the cartilage, and that can led to early
arthritis. If you can keep your knee from
going out again by giving up cutting sports
and wearing a brace, then you've accomplished
your goal.

For most people, especially young athletic
ones, the only way to achieve that goal is
through surgery, which is almost exclusively
arthroscopic these days. You substitute for
the ACL with another structure. Forty years
ago, surgeons made an attempt at repairing
torn ACLs, but those attempts failed, because
the ligament wouldn't hold a stitch. It looks
very much like fiber-optic cable or the end of
a mop when you cut it across. Repairs didn't
do well, so the treatment evolved into
substitution. The substitute is usually a
portion of the patellar tendon, which is
located right in front of the ACL. The
patellar tendon spans from the tip of the
kneecap to the tibia.

Back in the '50s, surgeons were taking a
portion of that and substituting it for the
ACL, but because they couldn't see inside the
knee, they were not putting it in the correct
spot. Back then, they were making these huge
incisions, just so they could have access to
that tunnel. They were just guessing where to put that substitute ligament,
and the results were usually poor. The best cases were 60 percent success
rate, which is why this injury was so catastrophic. Nowadays, with
arthroscopy, you can see to the millimeter where to put the substitute;
hence the results are about a 98 percent return to sports. It's a far more
exact procedure now.

ACL surgery is extremely technical. A millimeter difference here or there
can have a huge impact on the result. The procedure is something that needs
to be performed by an experienced sports orthopedist -- someone who performs
the surgery two or three times a week rather than two or three times a year,
someone's who's familiar with the injury, its mechanism, and the demands
when you return.

How long is it usually before the injured athlete can return to his sport?

Six months is the benchmark. Some physicians say nine; some say a year.

Can ACL tears be prevented?

Dr. Souryal: That's the $64,000 question. These injuries are so rampant.
There's not a good way to prevent them. We can make some recommendations: Be
sure you stretch before, during and after an activity, and get those
hamstrings, quadriceps and muscle-tendon units flexible so they can absorb
shock. Stregnth and endurance training is helpful. Most physicians recommend
cross-training, because you not only develop the pure strength component but
also the endurance component. That will help you in the fourth quarter of a
basketball game or the second half of a soccer game. Use common sense: When
you get extremely tired and your legs feel like lead pipes, that is not the
time to attempt a 360 dunk. Muscles are wonderful shock absorbers. There's
split-second timing that's required for a plant and a cut, and a jump and a
landing, where the muscles can absorb that shock. When you're fatigued, that
split-second timing is lost, and you don't necessarily have the quads
strength to absorb the shock when you come down from a rebound.

Really, at this point, that sort of advice is all we have. There are no
braces that are preventive. There are proprioceptive exercises that most
colleges and pro teams have their players do. At the recreational level,
these exercises aren't normally taught.

What's the prognosis for an athlete with an ACL tear?

This used to be a devastating injury. When an ACL tears, it does not heal.
Unlike most other ligaments, the ACL never has the opportunity to mend due
to its position and role in the knee -- it's very much like a rubber band.
That's why this is a forever kind of injury. It used to end athletic
participation both on the professional and recreational level. Now with
arthroscopic surgery and proper strengthening and rehabilitation techniques,
the future is much brighter. National results show a 96 to 98 percent return
to sport. Recovery still takes six months and is economically demanding and
involves an operation, but it's no longer career-ending.

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 Dr. Tarek O. Souryal, a member of the Association of Professional Team
 Physicians (PTP), served as team physician for the Dallas Mavericks from
 1988 to 1996. He is medical director of Texas Sports Medicine Group in
 Dallas and Irving (www.txsportsmed.com) and is director of the Sports
 Injury Clinic at Southern Methodist University. He received his medical
 degree from the University of Texas Health Science Center in San Antonio
 and completed a fellowship at the acclaimed Hughston Sports Medicine
 Clinic in Columbus, Ga. He has also served as head physician for the
 Dallas Texans of the Arena Football League and the Dallas Freeze of the
 Central Hockey League.

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