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Study Sheds Light on "Dark Side" of the Knee

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Duke Health News 919-660-1306

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."

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.

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