Note: This article will appear in an upcoming issue of Outpatient Surgery Magazine. I wrote it for that magazine’s audience – mostly hospital and surgery center managers, surgeons, nurses, etc. I posted it here for readers in those groups, but I also think that the average reader might find the technical aspects interesting.
Anterior cruciate ligament tears can be devastating injuries for athletes and athletic individuals. It is very difficult to play in sports that require cutting and pivoting without an ACL. Since the ligament does not usually heal on its own, athletes often do not have the stability in their knees to land from jumps or change directions quickly without their knees buckling. Therefore, surgical treatment for these injuries in athletes is very common.
Several decades ago, surgical treatment of ACL tears consisted of surgeons trying to repair the ligament, meaning sewing it back together or reattaching it. Unfortunately these “repairs” did not work well. Treatment then shifted to ACL “reconstructions,” essentially meaning that surgeons make a new ligament. Typically we use either tissue from the patient’s own knee (autograft – usually the patellar or hamstring tendons) or from a donor’s knee (allograft). Over the last twenty years, the surgery has not changed very much.
Success rates of the traditional ACL reconstruction have been good, but there has been increased attention recently on continued rotational instability with the traditional techniques. Essentially some researchers have demonstrated that the new ligament placed 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. An athlete playing a sport that requires changing directions might have a suboptimal outcome.
That is the idea behind the trend toward “anatomic” ACL reconstructions. This is a generic term in which a variety of techniques can be used to try to place the graft differently in order to prevent both anterior translation and rotation. This can be done with either two grafts (i.e. double-bundle reconstructions) or placing a single graft in a more lateral position in the femur.
Let me try to explain the concept describing the intercondylar notch (part of the femur in the center of the knee) as the face of a clock. Usually the surgeon drills the tunnel in the tibia first. Then he or she places a guide through the tibial tunnel into the femur to drill the femoral tunnel. The tibial tunnel then mostly dictates the location of the femoral tunnel, and it usually is placed at the 10:30 or 11:00 positions on a right knee (1:00 or 1:30 on a left knee). Anatomic ACL reconstructions aim to move the femoral tunnel to a more lateral position – to 10:00 or even 9:30 on a right knee (2:00 or 2:30 on a left).
Surgeons who use a double-bundle technique harvest two tendons or use cadaver grafts to make two grafts – one placed in the traditional vertical placement and one in the more lateral position. They argue that using both grafts more closely replicates normal ACL anatomy and provides both types of stability. The idea of double-bundle ACL reconstructions has been slow to catch on for several reasons – much longer surgery time, a steep learning curve for surgeons, potentially increased donor site morbidity, potentially increased costs If allografts are used, and debate about how much better these patients actually do clinically.
Most sports medicine surgeons do seem to be receptive to the concept of “anatomic” ACL reconstructions, and there does seem to be a larger trend towards placing the femoral tunnel more laterally. It is sort of a compromise in that it uses a single tunnel but places it in a way to still provide translational stability but eliminate rotational instability. This shift in tunnel placement has led surgeons and arthroscopic instrument and implant companies to develop new or modified equipment to 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 to allow them to bend and be placed in a more lateral position. One company has made the reamers “low profile” – essentially narrower to prevent damage to other knee structures while drilling in the more lateral location. Lastly, a company has designed tunnel cutting devices that can be placed through guides outside the knee anywhere in the notch that the surgeon chooses. All of the devices potentially allow better femoral tunnel locations, and thus, and more anatomic graft.
From a hospital’s or surgery center’s standpoint, these newer techniques can often be performed with one or two new pieces of equipment and not require entire sets of new instruments, helping to keep costs down. They will have to decide if the potential benefit to the patients outweigh the costs of the new equipment and storage requirements in their facilities. From a surgeon’s point of view, these technical modifications are fairly easy to adopt. They add very little time to the surgery and require little extra training. And from a patient’s standpoint, these newer techniques might lead to higher satisfaction rates and more successful return to sports.
