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All About Your ACL

All About Your ACL

Fitness
By Claudia Kalb
posted: 04/02/2000

It's early on a Tuesday morning in Ambulatory Surgery Room No. 1 at the Hospital for Special Surgery in New York City. The Talking Heads pulse througha pair of portable speakers, nurses buzz to and fro, and Dr. John MacGillivray dives knee-deep into his latest surgery. MacGillivray, a U.S. Ski Team doctor, makes a two-and-a-half-inch incision across patient Julie Bevad's left knee, opening it just enough to isolate Bevad's rubbery patellar tendon, which runs down the front of the joint. Using a surgical saw, MacGillivray and his assistant, Dr. Ross Henshaw, remove the middle third of the tendon, along with chips of bone on each end, and place it on a measuring board. The graft, about four inches long, will be Bevad's new anterior cruciate ligament. "Perfect," says MacGillivray. "That's the best cut I've seen."

Over the next 20 minutes or so, MacGillivray clears "junk" out of Bevad's knee—fat cells and damaged cartilage, which looks remarkably like crabmeat. Henshaw, meanwhile, works with the care of a jeweler polishing a diamond. He trims rough spots off the graft, then crafts the bone at either end into precisely shaped plugs. The doctors drill holesor "tunnels" into Bevad's shinbone and thighbone and then the graft goes in, its bone plugs acting like anchors to secureit in place. From start to finish, the surgery takes about an hour. The Talking Heads album is over. Now, it's Norah Jones singing "Sunrise." A new day for Bevad. Another successful ACL reconstruction for MacGillivray. "All right, good," he says. "That's fixed."

Across the country this season, too many unlucky skiers will hear the nasty pop of a torn ACL. Time was, knee injuries were rare among skiers—shinbone and ankle fractures were far more common. The advent in the '70s and '80s of stiff, high-backed boots, torsionally rigid skis and advanced bindings nearly eliminated lower-leg injuries, but also ushered in a modern ski plague: damaged ACLs. Some 24,000 skiers tear the ligament each season, making it perhaps the most common serious on-slope injury. There is no single explanation for the epidemic, but one leading theory involves a combination of factors. Today's stiff, forward-leaning boots apply greater pressure to a skier's ACL. Meanwhile, modern skis carve so readily and hold an edge so well that when skiers lose balance to the rear, their skis can continue turning across the hill, resulting in a twisted knee.

The good news, though, is that ACL reconstruction techniques are effective—and getting better all the time. Doctors are learning more about the biomechanics of the knee, and they're perfecting surgical techniques. Meanwhile, scientists are exploring futuristic ways to make ligaments from scratch—growing cellular "scaffolds" in petri dishes, even crafting new ACLs from silk. "We're doing substantially better than we were 10 years ago," says Dr. Spero Karas,an orthopedic surgeon at Atlanta's Emory University, "and I think we'lldo even better 10 years from now."

The knee is a masterwork of biological architecture. A hinged joint connecting the top of the shin with the bottom of the thigh, it allows us to jump, pivot, glide and slide—all moves we make on the mountain. The ACL, which runs through the middle of the knee like a cable on a suspension bridge, is a key piece of the structural design. Anchored at the back of the thighbone and the front of the shinbone, it prevents the lower leg from sliding too far forward and the knee from extending beyond its normal limits. It stabilizes a basketball player coming down from a rebound, a football player cutting a hard diagonal, or a skier laying down quick turns or landing a jump. Tear it, and you may still be able to jog or swim, but you won't do well with short stops or sudden turns. And you may suffer the aggravation of the old "trick knee," which gives out without warning, sometimes damaging healthy cartilage and setting you up for painful degenerative arthritis in yea to come.
[pagebreak]
John Rediger knows how critical the ACL is. A competitive skier since the 1970s, Rediger, 63, had suffered more than a few injuries over the years—a broken leg, a torn rotator cuff, a busted collarbone, six broken ribs. Then, on day five of a weeklong trip to Colorado last year, Rediger's knee gave out. "I was building up a lot of energy in my skis, making a left turn," he says. "I heard my right knee go pow!" Rediger, of Pecos, Texas, didn't need a doctor to tell him what had happened. "I fell down, tried to stand up and fell back down," he says.

"I knew what I'd done."

Thirty years ago, doctors "repaired" torn ACLs simply by stitching them back together, but the ligament lacks sufficient blood supply to heal itself. By the early '80s, doctors realized that such repairs were likely to fail and, in any event, did little to stabilize the knee over the long run. So the medical community turned to replacement ligaments. Over the years, a variety of artificial ACL materials have come and gone—the carbon fiber replacement, Dacron and even Gore-Tex ligaments. But, says Dr. Bert Zarins of Massachusetts General Hospital, "none of them withstood the test of time." What has? Human tissue.

Replacement ligaments come mainly from one of three human sources: your patellar tendon, your hamstring or a piece of cadaver tissue. The patellar tendon, which connects the kneecap to the tibia, is considered the gold standard for reconstruction. Surgeons remove the middle third of the tendon, then craft it into a new ACL. (The procedure is often referred to as bone-tendon-bone.) In a graft from the hamstring, which linksthe back of the thigh to the lower leg, two tendons are removed, then stitched together to maximize strength. But for many doctors and patients, cadaver tissue, called an allograft, is often the simplest option: Surgeons simply buy an actual patellar tendon, hamstring or even an Achilles heel tendon, from a tissue bank, then install it as an instant replacement. All three procedures have very good success rates—in the 80 to 90 percent range for skiers, says Karas.

Top surgeons are capable of using any one of the three techniques—but they tend to have strong preferences. MacGillivray favors the patellar approach, especially for younger, active patients. So do Zarins, head physician for the New England Patriots and the Boston Bruins, and Dr. Richard Steadman, cofounder of the Steadman-Hawkins Clinic in Vail, Colo. One of the patellar technique's main advantages: those ready-made bone plugs. "It's a strong graft with very good fixation," says Zarins.

One potential downside, however, to the patellar method is numbness in the kneecap, at the site from which the graft is harvested. Dr. Robert Johnson, emeritus professor of orthopedic surgery at the University of Vermont, calls it a "diddly problem," and says few patients complain. But patients vary when it comes to healing. Removing a hunk of the patella (kneecap), says Emory's Karas, may cause pain in some people when they return to sports, or even just when they kneel or crouch.

As a result, some surgeons prefer to avoid the issue altogether by transplanting a piece of the patient's own hamstring instead. Early on, doctors were concerned about how securely a hamstring graft would adhere. Without bone plugs on either end, would the hamstring slide around in the tunnels? Today, though, new fixation devices—better screws and specialized clips—are tightening the bond. Tunnel positioning has evolved: A graft that is positioned vertically is less stable and has a higher failure rate than one that goes in at a slightly more horizontal angle. And surgeons like Dr. Robert Hunter, a former team doctor for the U.S. Men's Alpine Ski Team who's now at the University of Arizona, are using a technique called "interference" or "compression" fit to make the connection even stronger. The key: making the holes in the shinbone smaller than the diameter of the screws used to secure the graft. "We keep getting smarter," says Hunter.

[pagebreak]

Michele Onderko is one hamstring fan. Three years ago, Onderko—a beginning skier—ripped her ACL when she crossed her tips and fell. "I did the somersault face-plant thing," she says. "It was a sharp pain. I couldn't move my knee at all; I couldn't stand on it." When it came time for surgery, Onderko, 35, of Moab, Utah, opted for a hamstring graft for two reasons. She enjoys caving, which requires crawling around on the ground, so she didn't want to risk a sore kneecap. And the mere thought of an allograft made her uneasy. "I freaked out about having somebody's body part in me," she says. Today, Onderko says her left hamstring, which provided the graft, is a little bit weaker than her right—not an uncommon side effect of the hamstring procedure. "I can't do as many leg curls," she says. But the difference is minor and, overall, "I have no problems with it. It's great."

So what about that allograft? It's the least popular of the three options, with one major disadvantage: risk of infection. Diseases like hepatitis and even HIV can be transmitted from donor to recipient. For the most part, however, donor tissues are sterile and safe. And for patients who already have damaged knees or for older patients whose own tissue may be weakened by age or who value the reduced pain and rehab effort the procedure generally affords, allografts are a solid choice. Hunter uses them almost exclusively. "There's no robbing of Peter to pay Paul," he says. "We can either take your parts and cause some post-op pain, or we can grab one off the shelf and stick it in like a new part." John Rediger initially resisted a donor graft, fearing infection, but after talking it over with his surgeon, he decided it was the best way to go. Less than a year after surgery, Rediger was back on his skis. "I had no pain," he says.

Sometimes it's possible to avoid an ACL reconstruction altogether. Skiers who suffer minor tears, who hit the slopes only occasionally, who avoid moguls and take it slow, or who are old enough to join the AARP may be able to get away with rehab alone. Interesting fact: You don't actually need a working ACL to ski effectively; you need it to help prevent you from falling, especially if your leg muscles aren't in great shape. For skiers who are lucky enough to tear their ACLs right at the spot where the ligament attaches to the thighbone, Steadman offers another nonreconstructive option, which he calls the "Healing Response." Working through an arthroscope, he makes tiny holes at the end of the thighbone. The procedure stirs up bone marrow cells deep inside the bone, which then clump together to create a bond between the bone and the ACL. "It is possible to make the ligament heal on its own," says Steadman. In 2001, he used the technique on U.S. racer Bode Miller, who last season became the first American in more than 20 years to win the overall World Cup title.

Of course, scientists wouldn't be scientists if they didn't dream up the next big thing. When it comes to ACL reconstruction, the scientific frontier isthe quest to create new ligaments in the lab. The history of artificial ACLs is littered with failure. Synthetic replacements, such as Gore-Tex, turned out to be too stiff, and they weren't biocompatible with the human body. Patellar tendons, hamstrings and allografts act as natural scaffolds, allowing a patient's own cells to populate the graft, then remodel it into a functional ACL. Synthetic replacements, by contrast, act like oil in water—they don't mix with patients' cells and, as a result, they weaken and rupture over time. "Back when we were using Gore-Tex, we thought it would be the Holy Grail," says MacGillivray, "but it failed miserably."
[pagebreak]
At the Hospital for Special Surgery, MacGillivray and other researchers are experimenting with using natural scaffolller than the diameter of the screws used to secure the graft. "We keep getting smarter," says Hunter.

[pagebreak]

Michele Onderko is one hamstring fan. Three years ago, Onderko—a beginning skier—ripped her ACL when she crossed her tips and fell. "I did the somersault face-plant thing," she says. "It was a sharp pain. I couldn't move my knee at all; I couldn't stand on it." When it came time for surgery, Onderko, 35, of Moab, Utah, opted for a hamstring graft for two reasons. She enjoys caving, which requires crawling around on the ground, so she didn't want to risk a sore kneecap. And the mere thought of an allograft made her uneasy. "I freaked out about having somebody's body part in me," she says. Today, Onderko says her left hamstring, which provided the graft, is a little bit weaker than her right—not an uncommon side effect of the hamstring procedure. "I can't do as many leg curls," she says. But the difference is minor and, overall, "I have no problems with it. It's great."

So what about that allograft? It's the least popular of the three options, with one major disadvantage: risk of infection. Diseases like hepatitis and even HIV can be transmitted from donor to recipient. For the most part, however, donor tissues are sterile and safe. And for patients who already have damaged knees or for older patients whose own tissue may be weakened by age or who value the reduced pain and rehab effort the procedure generally affords, allografts are a solid choice. Hunter uses them almost exclusively. "There's no robbing of Peter to pay Paul," he says. "We can either take your parts and cause some post-op pain, or we can grab one off the shelf and stick it in like a new part." John Rediger initially resisted a donor graft, fearing infection, but after talking it over with his surgeon, he decided it was the best way to go. Less than a year after surgery, Rediger was back on his skis. "I had no pain," he says.

Sometimes it's possible to avoid an ACL reconstruction altogether. Skiers who suffer minor tears, who hit the slopes only occasionally, who avoid moguls and take it slow, or who are old enough to join the AARP may be able to get away with rehab alone. Interesting fact: You don't actually need a working ACL to ski effectively; you need it to help prevent you from falling, especially if your leg muscles aren't in great shape. For skiers who are lucky enough to tear their ACLs right at the spot where the ligament attaches to the thighbone, Steadman offers another nonreconstructive option, which he calls the "Healing Response." Working through an arthroscope, he makes tiny holes at the end of the thighbone. The procedure stirs up bone marrow cells deep inside the bone, which then clump together to create a bond between the bone and the ACL. "It is possible to make the ligament heal on its own," says Steadman. In 2001, he used the technique on U.S. racer Bode Miller, who last season became the first American in more than 20 years to win the overall World Cup title.

Of course, scientists wouldn't be scientists if they didn't dream up the next big thing. When it comes to ACL reconstruction, the scientific frontier isthe quest to create new ligaments in the lab. The history of artificial ACLs is littered with failure. Synthetic replacements, such as Gore-Tex, turned out to be too stiff, and they weren't biocompatible with the human body. Patellar tendons, hamstrings and allografts act as natural scaffolds, allowing a patient's own cells to populate the graft, then remodel it into a functional ACL. Synthetic replacements, by contrast, act like oil in water—they don't mix with patients' cells and, as a result, they weaken and rupture over time. "Back when we were using Gore-Tex, we thought it would be the Holy Grail," says MacGillivray, "but it failed miserably."
[pagebreak]
At the Hospital for Special Surgery, MacGillivray and other researchers are experimenting with using natural scaffolds seeded with fibroblasts—cells that excrete collagen, which is the protein that makes up ligament, bone and other tissue. "It would be great to be able to grow a new ACL in a petri dish, then place it in the patient," says MacGillivray. Other research teams are pursuing similar goals. The key question: What kind of material makes the best scaffold?

Biomedical engineer Greg Altman of Tissue Regeneration, Inc., in Medford, Mass., thinks he has the answer. He's making ACL scaffolds out of silk. The key to his product, Altman says, is that the silk—which has been treated to make it biocompatible—is strong enough to stabilize the knee immediately after surgery, but it's also capable of degrading at a controlled rate. As it does, the body's cells make their way into the scaffold and reinforce it. The silk is now being tested in animals, and while there's no published data yet, "the early results look incredibly promising," says Altman. "The truly revolutionary aspect of this research is that it's a way to recreate your own tissue without having to harvest tendon graft tissue from the body."

New ligaments would be a boon to the ski-knee industry. They'd make surgery easier for both patient and doctor, they'd minimize pain, and they'd speed recovery. But we're not there yet. For now, replacements adapted from patients' own bodies work well, but they're only as good as the will of their patients. The key to a long-lasting result: rehab. "Rehab is as important as surgical reconstruction," says Dr. Henry Goitz, chief of sports medicine at the Medical College of Ohio.

Twenty years ago, rehab meant immobility: knee in cast, patient in bed. But sitting still, doctors learned, stiffens the knee and actually impedes recovery. "Immobilization is almost worse than the injury itself," says Michael Levinson, clinical supervisor of HSS's sports medicine rehab department. Today, the goal is immediate movement. Bill Knowles, director of iSPORT Training at the Vermont Orthopaedic Clinic in Killington, Vt., recommends staying away from strength-training machines early on and relying more on free weights to challenge the body's sense of balance. Later, balance or "wobble" boards can help simulate the back-and-forth of skiing, allowing patients to develop a better feel for how their bodies move. "You retrain your brain to know where your legs are in space," says Goitz.

That concept, known in sports-medicine lingo as proprioception, could play a critical role in avoiding injuries. Over the course of 20 years treating professional ballerinas, Dr. Nicholas DiNubile, an orthopedic surgeon at the University of Pennsylvania, has seen only a handful of ACL tears. DiNubile believes that dancers' finely tuned coordination, internal balance and keen sense of body positioning allows them to land safely and keeps their knees strong. "They know where they are in space, and when they hit the ground it's like they have a little leveler in their knee," he says. "These dancers are immunized against ACL injuries." New research suggests that learning about proprioception can help reduce injuries. In July, the Santa Monica Orthopaedic and Sports Medicine Research Foundation reported that an intensive 20-minute muscle strengthening and proprioceptive training program reduced ACL injuries by 88 percent in one year among female soccer players.

[pagebreak]

Can skiers learn to prevent ACL injuries, too? Dr. Robert Johnson thinks so. Johnson, who's been studying ACL injuries for more than three decades, believes the way in which skis and boots position the body is the problem. "The combination of a good-turning ski and fixed forward lean is to blame," he says.

For years, Johnson has made it his mission to teach skiers to prevent injury. His ACL Awareness Training program, which offers advice on how to recover from phantom-foot falls (keep arms forward, feet together and hands over skis) and avoid them altogether by corr

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