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Anterior cruciate ligament tears are devastating injuries for serious athletes and weekend warriors alike. With no shortage of each, ACL repairs are among the most common orthopedic procedures performed. Today a growing number of orthopods are opting to reconstruct the ACL in ways that closely match the knee's natural anatomy. Read on to learn more about this so-called anatomic approach.
3D MRI Improves ACL Repair in Kids
Using 3D MRI imaging to pre-plan ACL repairs in young athletes leads to more precise reconstruction without disturbing the growth plate, say researchers at Emory University School of Medicine and Georgia Tech in Atlanta.
"The problem with young children having this surgery is traditionally we've made tunnels in certain orientations that go right through the growth plate," says John Xerogeanes, MD, an associate professor in the department of orthopedics at Emory. "And if you go through the plate, it can cause damage and result in growth arrest."
By making a 3D model of the knee before surgery, Dr. Xero-geanes says surgeons are able to pick 2 points and measure them on the specific knee anatomies of individual patients, letting surgeons drill the tunnels precisely where they'll place the new ligament. That ensures "they're going to miss the growth plate with the reconstruction" and lets them determine how long the tunnel hole and new ACL will need to be before taking that information to the OR and applying it. "That's going to save time and X-ray exposure, and give a better reconstruction for the child," he says.
Traditional treatment for ACL injuries in kids — who are often injured participating in football, basketball, soccer and gymnastics — has been rehabilitation, wearing a brace and refraining from athletics until growth stops and ACL reconstruction surgery can safely be performed (usually in the mid-teens), according to the Emory Sports Medicine Center.
Kids who undergo this type of operation will still have at least 1 year of recovery time before they can resume normal activity, says Dr. Xerogeanes.
— Daniel Cook
The old way
Since the ACL rarely heals on its own, injured athletes often don't have the stability in their knees to land from jumps or change directions quickly without the joint buckling, making surgical treatment for these injuries almost a given for those who play sports that require cutting and pivoting.
Several decades ago, surgical treatment of ACL tears meant sewing the ligament back together or reattaching it to the bone of the knee. These techniques didn't work well. Treatment shifted to ACL reconstructions, which entailed making new ligaments out of patients' tendons (autografts usually culled from the patellar or hamstring tendons) or from a donor's knee (allograft tendons). Over the last 20 years, ACL reconstruction hasn't changed much.
Success rates of traditional reconstruction have been good, but rotational instability in the knee following surgery remains a problem. Some researchers have demonstrated that placing a new ligament in the traditional fashion prevents the tibia from shifting out from under the femur, but it might not prevent the tibia from rotating abnormally around the femur. That could mean suboptimal outcomes for athletes who must change directions quickly.
The new way
Traditional reconstruction's limitations have spurred the trend toward anatomic ACL reconstructions. The term "anatomic" describes a pair of techniques that are used to place the graft tendon in a way that prevents both anterior translation and rotation of the knee. This can be done with 2 grafts, double-bundle reconstructions or by placing a single graft in a more lateral position in the femur.
- Single-bundle. To understand this approach, think of the intercondylar notch (the part of the femur in the center of the knee) as the face of a clock. Traditionally, surgeons drilled a tibial tunnel, then placed a guide through that tunnel and into the femur in order to drill the femoral tunnel. The tibial tunnel, usually placed at the 10:30 or 11:00 positions on a right knee (1:00 or 1:30 on a left knee), therefore dictated where the femoral tunnel was placed. Anatomic ACL reconstructions aim to move the femoral tunnel to a more lateral position: 10:00 or even 9:30 on a right knee (2:00 or 2:30 on a left knee). Once surgeons are comfortable with this approach, case times should last only about 10 minutes longer than a conventional ACL reconstruction.
- Double-bundle. Technically, this approach is the most anatomically accurate, since the ACL is comprised of the anteromedial and posterolateral bundles. You harvest 2 tendons or use cadaver grafts to make 2 grafts, one placed in the traditional vertical placement and one in the more lateral position. Some surgeons argue that using both grafts closely replicates normal ACL anatomy and provides both translational and rotational stabilities.
The idea of double-bundle ACL reconstruction has been slow to catch on for many reasons: much longer surgery times; a steep learning curve for surgeons; potentially increased donor site morbidity; potentially increased costs if allografts are used; and debate about how much better the actual results are compared to single-graft techniques. It's a technique that's best suited for high-level athletes who seek a return to competitive contact sports as opposed to injured baby boomers with aims at returning to everyday activities.
Case times are significantly longer than traditional ACL reconstructions; surgeons who are just learning the procedure might take up to 4 hours to complete it. Even cases performed by experienced surgeons who are expert in the technique will last at least 30 minutes longer than standard ACL procedures.
Shift in Tunnel Placement Spurs New Device Development
More orthopedic surgeons are placing the femoral tunnel more laterally to provide translational stability while eliminating rotational instability in the knee.
The shift in tunnel placement has led arthroscopic instrument and implant manufacturers to develop new or modified equipment that lets surgeons drill more lateral femoral tunnels.
Most sports medicine surgeons seem to be receptive to the concept of anatomic ACL reconstruction, and there does seem to be a larger trend toward placing the femoral tunnel more laterally in order to provide translational stability while eliminating rotational instability in the knee.
The shift in tunnel placement has led arthroscopic instrument and implant manufacturers to develop new or modified equipment that lets surgeons drill more lateral femoral tunnels. Several companies have designed femoral drill guides that can be placed through one of the arthroscopic knee portals rather than the tibial tunnel. One company has redesigned its femoral guide pins and reamers to make them flexible, so they can be bent and placed in a more lateral position. Another has developed low-profile reamers, which are essentially narrower devices that prevent damage to other knee structures while surgeons drill in the more lateral location. A third has designed tunnel-cutting devices that you can place through guides outside the knee and anywhere in the intercondylar notch that the surgeon chooses. All of theses developments potentially allow better femoral tunnel locations and a more anatomic graft.
Surgeons can perform these newer techniques with 1 or 2 new pieces of equipment and without the purchase of entirely new sets of instruments, which helps keep costs down when upgrading to the anatomic approach. You'll have to decide if the potential patient benefits outweigh the costs of the new equipment and storage requirements. From your surgeons' points of view, these technical modifications are fairly easy to adopt.
It's hard to disagree with those that argue that the anatomic approach is the best way to treat patients with ACL tears — especially when you consider that the approach will likely become the standard of care, if it hasn't already. The new techniques and required instrumentation add very little time to the surgery and require little extra training. And from a patient's standpoint, they might lead to higher satisfaction rates and a more successful return to sports.