The ACL Dilemma

The more we learn, the more we often realize how much we don’t know. Twenty-five years ago, I thought we had the anterior cruciate ligament (ACL) dilemma all figured out: arthroscopic technique, patellar tendon grafts, meniscus repair, and immediate motion. Everything looked good clinically until we started seeing the results of long-term outcome studies.² I must admit I’ve been missing some of the warning signs. While arthritic changes were not unusual in many of the knees of patients showing up 10 to 12 years after ACL surgery in my clinic, there were many who were out that long who were still active and doing pretty well. Consequently, I’m still not sure where the truth lies on the success of our current ACL techniques. Unfortunately, nothing changes perceived good results more than long-term follow-up. A close look at some of the best known clinical reviews reveals some interesting regional differences in treatment that may factor into the reported outcomes. For instance, in the review by Oiestad et al, in 2009,⁶ a cohort study with an evidence level of II, there were 127 partial meniscectomies in 106 patients with only 8 meniscal repairs. The mean time from injury to ACL reconstruction was 28 months. The delay to reconstruction and the low number of meniscus repairs may reflect the Scandinavian approach, which may not be representative of clinical trends elsewhere and may explain some of the less-than-optimal clinical results.

One of the difficulties in tracking results of specific ACL techniques is the rapidly changing ACL technique carousal. No doubt, the recent emphasis on a more anatomic reconstruction results in better surgeries and is a step in the right direction. Whether 1 bundle or 2, placing the graft in the anatomic femoral and tibial footprint while producing a more horizontal (and less vertical) graft will pay dividends. It’s very interesting how technology drove us to the more vertical position and what we have done recently as surgeons to correct those errors. Being aware of how we went awry should help steer our efforts in the future as we more critically evaluate emerging technologies.

Now that we are doing a better job placing the ACL graft in the femoral and tibial footprint, thinking more about the soft tissue mechanics of the graft itself appears worthwhile.⁴ Most techniques use a strong, well-fixed construct, which will allow immediate motion, accelerated rehabilitation, and, consequently, a quicker return to full activities. Unfortunately, equaling or surpassing the tensile strength of a normal ACL may not be optimal if the stiffness of the graft does not match that of the normal ACL. The extreme example of this issue would be the use of a steel cable for an ACL, which would alter joint kinematics, possibly transmitting much higher contact forces through the joint. Current hamstring and patella tendon grafts may be too stiff.¹ Furthermore, these very strong, high-stiffness grafts may stress shield the host and donor cells in the graft, robbing them of the forces needed for postoperative maturation.

Needless to say, much can be examined in the effort to improve current ACL surgery. Refining the graft placement while we search for a better graft source will most likely yield further improvements. Hopefully, these will minimize the arthritic changes seen after many ACL reconstructions.

Besides refining operative approaches, there are many things that we can do as clinicians to help our patients deal with the problem of osteoarthritis. We know what factors accelerate osteoarthritis development without an ACL injury. No doubt, obesity,^7,8 lower extremity strength¹¹ (especially in the quadriceps), impact activities, and contact sports^3,13 all play a role in the development of osteoarthritis. Counseling our patients about the maintenance of an ideal body weight, regular low impact exercise to maintain strength, and the consequences of continued contact sports should be routine. Many of our patients will not heed these concerns, at least initially, but hopefully, they will see the light with time. We should be particularly vigilant with those who have malaligned lower extremities, knowing that it may accelerate the degenerative processes.⁹ Strict attention should also be paid to the maintenance of full range of motion at the knee (yes, even hyperextension) through the preoperative, operative, and postoperative course, making sure not to “capture the knee” with poor graft placement, overtightening the graft, or inadequate attention to detail during rehabilitation. Shelbourne et al’s outcome results paint a much brighter future for those that can maintain a full range of motion.¹⁰

With all of these pitfalls of clinical care looming, no doubt prevention of ACL injuries is the best and safest route for our patients. The ACL risk factor review in this issue¹² emphasizes several anatomic and neuromuscular risk factors: female sex, decreased intercondylar femoral notch size, decreased depth of medial tibial plateau, increased slope of lateral tibial plateau, and increased anterior/posterior knee laxity. Hopefully, we will soon be able to noninvasively screen for all of these features. These most likely act in some combination. Unfortunately, a multivariate risk model incorporating all of these is not yet available.

Until we can better target who is most at risk, those participating in the highest risk sports, like women’s soccer and basketball, should incorporate an ACL injury prevention program into their training schedule. A review in this issue highlights the 2 programs that have decreased ACL injury rates: Prevent Injury and Enhance Performance and Cincinnati SportsMetrics.⁵ While dissecting the components of these programs, it’s still difficult to determine which exercises are changing the injury rate. The link between physiologic change and the mechanisms of ACL injury is still not clear.

So, if anyone is wondering why another journal issue is focusing on the ACL, there is a lot more that we need to know, and, unfortunately, that pile is growing rapidly.

Happy New Year, and let’s get to work!

—Edward M. Wojtys, MD
Editor-in-Chief