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True Outcome of ACL Reconstruction

There are many different ways to approach the problem of an anterior cruciate ligament (ACL) injury of the knee. A partial tear may respond well to conservative (nonoperative) care. But if rehab doesn't yield the desired results (or in the case of a competitive athlete), the ligament may need surgical repair. The surgeon stitches the ends of the ligament back together.

A fully ruptured ACL often requires surgical reconstruction. It doesn't work to try and pull the ends of the ruptured ligament back together -- instead, a piece of tendon is taken from another area of the knee and used as a graft to replace the damaged ligament. The donor graft comes from one of two places: either the patellar tendon (just below the knee cap) or the hamstrings (behind the knee).

Research is ongoing trying to figure out which method works best. There are a lot of variables to work through in making the comparison. For example, patients of all ages, sizes, and shapes injure the ACL and need this treatment. Athletes have very different needs than older, less active adults.

The reconstructive surgery can be done with an open incision but more recently, the use of an endoscope has become more the standard of care. The endoscope is a thin, round tube that can be inserted into the joint through which the surgeon can see inside the joint as well as pass instruments and sutures down through the tube for use inside the joint.

One other confounding factor in studying ACL reconstructive surgery is the fact that two-thirds of all patients with a rupture ACL also sustained damage at the same time to other soft tissues in the knee. Only about one-third of the patients with a deficient ACL have an isolated ACL injury. By isolated, we mean the ACL injury is the only area of damage.

In this study, orthopedic surgeons from Australia have been following patients with an isolated ACL injury reconstructed who had a patellar tendon graft. They have reported on their short-term and mid-term results in previous studies. This time, it's a report after 15 years! That time frame certainly qualifies as a long-term study.

Results have been measured using a variety of tools. Knee range-of-motion can be easily measured with a special tool called a goniometer. Stability of the joint was tested using several clinical tests well-known to orthopedic surgeons, physical therapists, and athletic trainers (e.g., pivot-shift test, Lachman test). Knee function was assessed using the single-legged hop test, the Lysholm Knee Score, and the International Knee Documentation Committee evaluation (IKDC).

They found that a full 30 per cent of the group had another ACL injury after the first one. Most of those injuries were to the ACL in the other knee. A smaller number ruptured the graft. Graft ruptures were most common in active patients who were under the age of 18 at the time of the first (initial) ACL injury. A closer look at the data also showed that the angle of the graft made a difference. Lower graft angles (measured as less than 17 degrees) were much more likely to rupture.

Stability, motion, and function were nearly normal in 90 to 100 per cent of the group. The biggest functional problem (affecting daily activities) was pain when kneeling. A second equally important finding was the high incidence of osteoarthritic changes. At the end of the first five years, one-third of the group had signs of joint degeneration (seen on X-rays). By the end of 15 years, that number had increased to 51 per cent.

Let's go back and talk a little more about those patients who injured their other ACL. In today's modern lingo, "What's up with that?" The authors suspect there may be several reasons why someone with a reconstructed ACL would end up rupturing the other knee.

The first is simply anatomy, biomechanics, and genetics -- in other words, the way you are put together. The second is the fact that a reconstructed ACL is actually more stable and stronger than the natural ligament that might stretch out more over time. And the third relates to patients being more protective of the reconstructed knee. Further study may uncover the exact reason(s) for this phenomenon.

In summary, long-term results of isolated anterior cruciate ligament injuries treated with reconstructive surgery using a patellar tendon graft are good. A few problems can crop up such as pain with kneeling, arthritis, and further knee injuries. Efforts to find ways to reduce knee pain after patellar tendon grafting are underway. Patients agree a little knee pain when kneeling is a small price to pay for the excellent long-lasting results they got otherwise.

Reference: Catherine Hui, MD, FRCS(C), et al. Fifteen-Year Outcome of Endoscopic Anterior Cruciate Ligament Reconstruction with Patellar Tendon Autograft for "Isolated" Anterior Cruciate Ligament Tear. In The American Journal of Sports Medicine. January 2011. Vol. 39. No. 1. Pp. 89-98.