Improving Treatment For Posterior Cruciate Ligament Knee InjuriesMany people are familiar with anterior cruciate ligament (ACL) tears. But inside the knee joint there are two important ligaments. The ACL criss-crosses with the posterior cruciate ligament (PCL). And PCL injuries account for up to one-third of all knee injuries.
The PCLs main job is to keep the tibia (lower leg bone) from sliding backwards under the femur (thigh bone). A second function of the PCL is to restrain the tibia from rotating outward too far.
There is a broad range of acceptable treatment methods for PCL injuries. For mild injuries, conservative (nonoperative) care is advised. This may include physical therapy and/or bracing. Reconstructive surgery may be needed. But whereas surgical treatment for ACL injuries is fairly standard now, there isn't one single method of surgical management for PCL injuries that is considered the gold standard.
In this study, surgeons used cadaver knees (preserved after death for study) to help iron out this problem. They specifically focused in on the effects of injury to the PCL. They also looked at what happens when the posterolateral corner of the knee joint is damaged. Severe PCL tears are often accompanied by damage to this corner of the knee where the femur and tibia meet.
Posterior refers to the back side of the knee.Lateral is along the outside edge of the joint. There are five basic structures that make up the posterolateral corner. These include two muscles: the lateral head of the gastrocnemius (calf) and the popliteus. Three ligaments are also involved: the popliteofibular ligament, the lateral collateral ligament (LCL), and the arcuate-fabellofibular ligament complex.
The researchers placed 10 pairs of intact (normal) cadaver knees in a special limb-holder. The PCL of each knee was tested. Then they cut the PCL and retested the specimens. In the third step, they took out the posterolateral corner (as if it were torn completely) and retested again.
The tests consisted of the posterior drawer test, the dial test, and stress radiography. The posterior drawer test is done by the examiner. The knee is bent 90-degrees. The foot is stabilized (usually flat on the floor or examining table) while the examiner grasps the lower leg and pushes it backward. If the tibia moves back more than normal, the test is positive for a probable PCL tear.
PCL tears were graded as 0 for normal (the tibia moves or gives a little but not easily), Grade 1 for three to five millimeters (mm) of posterior translation (backward movement), Grade 2 for six to 10 mm, and Grade three for more than 10 mm of displacement.
The dial test is done by using a goniometer to measure how far the tibia can rotate externally (outwardly). A goniometer is a special tool used to measure joint range-of-motion. The goniometer measurement was taken with the knee in 30-degrees of flexion and in 90-degrees of flexion.
Stress radiography is a series of X-rays taken with the knee in a neutral position and then in a positive posterior drawer position. In both views, the knee was flexed 90-degrees. A special device was used to apply enough force to the upper portion of the tibia to displace it backwards. The X-rays were repeated after the posterolateral corner was removed.
All data collected was compared among the intact knees, knees with an isolated Grade 2 PCL injury, and knees with damage done to both the PCL and posterolateral corner (Grade 3). With each additional injury, the amount of posterior tibial displacement increased. The amount of external tibia rotation also increased. This was especially noticeable with damage to the posterolateral corner.
The findings were summarized as follows:
The result of this study confirm that patients with a Grade 3 posterior drawer test have both a PCL tear and damage to the posterolateral corner. More than 10 mm displacement on stress radiography confirms a combined injury. This type of injury requires reconstructive surgery to both areas. Previous studies have confirmed that repairing the PCL without fixing the corner results in a failed surgery.
Jon K. Sekiya, MD, et al. A Clinically Relevant Assessment of Posterior Cruciate Ligament and Posterolateral Corner Injuries. In The Journal of Bone and Joint Surgery. August 2008. Vol. 90-A. No. 78. Pp. 1621-1627.
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