Study sheds light on 'dark side' of the knee

July 01, 2002

ORLANDO, FLA -- As orthopedic surgeons come to appreciate the important role of the so-called "dark side of the knee" in the failure of reconstructive knee surgeries, laboratory research led by a Duke University Medical Center investigator has determined the optimal surgical approach to improve the outcomes of these reconstructive surgeries.

Knee damage is the most common sports injury and it usually occurs when there is a tear or break in at least one of the four ligaments of the knee, the most common being the anterior cruciate ligament (ACL). Orthopedic surgeons will often reconstruct the joint using tissue from the patient or a cadaver. While the surgery and subsequent rehabilitation returns about 90 percent of patients to normal sporting activity, surgeons are finding that instability in a little-studied area of the knee -- the posterolateral corner -- is a leading cause of knee reconstruction failures. The posterolateral corner is the outside region of the knee just posterior to the kneecap.

"To our knowledge, no one has studied the two accepted procedures for dealing with the instability in this 'dark side' of the knee," said Claude T. Moorman III, M.D., orthopedic surgeon and director of the sports medicine program at Duke, who led a team of researchers from the University of Maryland, Johns Hopkins University and University of Alabama-Birmingham. "While both surgical approaches are effective, our analysis shows that a simpler and quicker approach may be the better of the two."

The results of the team's study were prepared for presentation today (July 1, 2002) at the 28th annual meeting of the American Orthopedic Society for Sports Medicine (AOSSM). The study received the 2002 Aircast Award for Basic Science, given annually by the AOSSM. The study was funded by University of the Maryland Sports Medicine, where Moorman served prior to coming to Duke last year.

"This posterolateral corner has been referred to as the 'dark side' of the knee because it is poorly understood and treatment for these injuries has not been consistently successful," Moorman said. "Now, as a result of this comparison, we have a straightforward and predictable approach to successfully restore knee stability to its normal state."

The knee is a complex joint, in which a series of ligaments, tendons and cartilage create a "hinge" where the femur, the upper leg bone, connects with the two bones of lower leg, the larger tibia and the smaller fibula. The kneecap, or patella, protects the joint. When the posterolateral corner is not aligned properly after reconstruction, the tibia and femur rotate more than normal, which puts undo forces on the joint and leads to the failure of the reconstruction.

To compare the benefits of the two most commonly used procedures to address this instability, the team used 12 pairs of fresh cadaveric knees. After performing each of the two surgeries on one knee of the pair, the knees were then attached to a device in the laboratory that can simulates the pressures and torques experienced by the knee.

The first approach, known as the combined tibial and fibular-based reconstruction, uses cadaveric tendon to make two attachments: from the femur to both the fibula and tibia. In the second approach, called the fibular-based reconstruction, a portion of patient's tendon is used to make a figure-eight connection from the femur to the fibula. (See attached drawings.)

"After testing both approaches in the laboratory, we found that both can successfully restore stability to the knee, but the fibular-based has the advantages of being an easier procedure, taking less time in the operating room, and causing fewer surgical complications," Moorman said.

Moorman added that the benefits of the cadaveric (allograft) source over the patient (autograft) source of tendon are still a matter of debate among surgeons. While the harvest of autograft tissue involves another incision, the quality of the tissue is usually better and there is no risk of disease transmission, Moorman said. Further clinical trials are needed to determine the best source of tissue, he added.

"While many techniques have been considered and used in clinical practice, few have been critically evaluated by biomechanical studies to determine their ability to restore normal knee functions," Moorman said. "Our study provides guidance for orthopedic surgeons who treat this difficult injury pattern."
-end-
Other members of the team included Peter Rauh, M.D., and Leigh Ann Curl, M.D., of the University of Maryland; Louis Jasper and Stephen Belkoff, Ph.D., Johns Hopkins University; and W.G. Clancy, M.D., University of Alabama-Birmingham.

Duke University Medical Center

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