Today's News

Wednesday, March 10, 2004

Research on ACL-deficient knees earns OREF Award

By Jeannie Glickson

Frank R. Noyes, MD; Edward Grood, PhD; Thomas Andriacchi, PhD and Sue Barber Westin, BS, have received the 2004 OREF Clinical Research Award for their paper on "Factors affecting the treatment of anterior cruciate ligament (ACL)-deficient knees with lower limb malalignment and associated ligamentous instabilities: A correlated clinical, biomechanical and dynamic gait analysis."

"ACL ruptures in the United States alone account for more than 100,000 surgical reconstructions each year," noted the researchers. "By conservative estimates, 5 percent to 10 percent of these primary procedures fail, leading to 5,000 to 10,000 potential revision cases each year. The clinical syndrome of ACL-deficiency (alone or combined with other ligament instabilities), along with lower extremity malalignment, has posed unique challenges to clinicians over the past two decades."

Through a series of biomechanical, dynamic gait and clinical investigations conducted over a 17-year period, these researchers developed a stepwise algorithm for the diagnosis and treatment recommendations for these complex knees.

A focus on complex cases

The studies addressed complex revision cases in which four or more operative procedures had failed to achieve knee stability and function due to other, untreated abnormalities such as an underlying varus malalignment, medial tibiofemoral pain and arthrosis, loss of the medial meniscus, and associated posterolateral ligament deficiency. The patients were too young to be considered for total joint replacement and conservative measures failed to alleviate pain, instability and functional limitations with daily activities.

The researchers noted that in the mid-l980s, when their series of studies began, there was a paucity of scientific investigations and clinical results to formulate a rational treatment plan for knees with these combined abnormalities. There was an inability to predict the results of operative procedures to restore lower limb alignment and knee stability.

"We started to see many patients in our clinic who had prior ACL surgery that had failed and I noticed many had varus malalignment," explained Dr. Noyes. "It was our intent to develop a logical and rational plan to diagnose all of the abnormalities present and develop a stepwise approach to operative intervention. I believed that the osteotomy should be performed first, and explained to patients that their lower limb malalignment was like a tire on a car that is out of alignment. Just placing a new tire on the car without first fixing the malalignment wouldn't solve the problem."

Study series yields guidelines

First, a series of biomechanical studies were conducted to document the types of knee subluxations that occurred with ACL and posterior cruciate ligament ruptures, alone and in combination with posterolateral ligament injuries. The contribution of the different ligament structures that comprise the posterolateral soft tissue complex was defined. Knee laxity tests were then developed to allow the clinician to diagnose posterolateral ligamentous deficiency.

A system to classify the anatomic abnormalities of the lower limb and knee was proposed in which the terms primary-, double-, and triple-varus knee were developed. These terms take into account the underlying tibiofemoral osseous and geometric alignment, abnormal knee motion limits, abnormal knee joint positions (subluxations) and specific ligament defects.

Next, a series of gait studies were done that provided an analysis of the moments and forces about the knee joint, and abnormal loadings in varus aligned ACL-deficient knees. A new clinical syndrome of a hyperextension adaptation gait abnormality was identified in patients with associated posterolateral ligament injuries. These patients require preoperative gait retraining to correct abnormal gait characteristics before surgical intervention.

Two prospective clinical studies were then conducted on patients who had osteotomy to correct limb alignment, followed by knee ligament reconstruction in a staged procedure. New postoperative treatment protocols were established that allowed immediate protected knee motion postoperatively to lower complication rates of disuse and arthrofibrosis.

The final result of this multiyear effort was a series of clinical algorithms for the clinician to follow in: 1) diagnosis and treatment of combined malalignment and ligament instabilities of the knee joint, 2) determination of the type and magnitude of osteotomy correction, 3) selection of type of posterolateral reconstructive procedure when required, 4) staging of multiple operative procedures to decrease morbidity and increase the overall success of restoring limb function and 5) detailed postoperative rehabilitation programs to restore function.

  Frank R. Noyes, MD

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Last modified 19/February/2004