In the past twenty years there has been a revolution of reconstructive surgery and rehabilitation of the Anterior Cruciate Ligament. A rupture or tear of the Anterior Cruciate Ligament used to signify the end of the athlete's career, however studies and tremendous improvements have made it so a tear simply means the end of an athletes season. Today, 50,000 reconstructive surgeries are preformed each year. A recent study of healthy normal athletes against athletes recovering from ACL reconstructive surgery shows many interesting things. But dont take my word for it. Read on.
Studies of nerves and balance are chiefly responisible for the remarkable improvement in ACL knowelege. Why are nerves important? Studies show that when the ACL is ruptured there is a disruption of the sensory information, which is carried to the central nervous system. This disruption results in recurring microtrauma and a less stable lower extremity. Furthermore, problems with proprioception and passive movement have been found in patients with chronic ACL injuries. After an ACL rupture, static postural control is lessened. Postural control involves the aliginment of the leg and static refers to the control and function of the ligaments. In effect, an ACL rupture has a significant impact on an athletes ability to run, jump and perform the activities related to their sports. Doctors want to develop a tool which measures posture and balance. Little is known whether the measurement of postural control can tell you if there are conditions that might predispose an athlete to future injury.
Dr. Hoffman, Dr. Schrader, and Dr. Koceja did a study of normal athletes and athletes recovering from ACL reconstruction. Three areas were tested to find a relationship between nerves and function of the ACL. The first test was strength testing. A Cybex Dynamometer was used to determine the peak force and the peak torque when the athletes did one set of leg extensions wih 5 repetitions. The second test was the static balance evaluation. Participants stood on one foot on a Kistler Platform looking straight ahead without limbs touching eachother or the ground for 20 seconds. The center of pressure and movement were monitered. The third test was a dynamic balance evaluation. Participants would stand on one leg and after 8 seconds, electrical perturbation was delivered to the tibial nerve of the leg in contact with the ground. This would throw them off balance and the participant would have to recover. Three phases of this test were analyzed: Pre-stimulation, active and recovered to see the length of time it took to recover. They also took note of their standing techniques before and after. Computer scanning was used to detect center of pressure movement and sagital plane movement.
Results of this test showed that there was much less peak force generated by the ACL injured. The static analysis showed no significant effects. The dynamic balance evaluation displayed a significant effect with the ACL injured group having longer durations. The testees did not change their standing habits before and after perturbation even though they knew they were going to be perturbed.
Theories on ACL injuries are varied. One doctor suggests that damage done to the joint mechanoreceptors changes messages to the central nerve system for that specific joint. Others say that damage to these mechanoreceptors messes up a central postural control mechanism, effecting the postural control of the leg. At any rate, it is well known that ACL injury negatively effects postural control. Research supports the idea that ACL has a vast neurologic supply. Furthermore, evidence supports the idea that there is a direct connection between the neurologic part of the ACL and the central nervous system.
The strength findings of the test, supported by the outside reseach of others, concludes that quadraceps are weakened after ACL reconstruction. Reconstruction of the ruptured ACL does not look lik it affects force output of the noninjured leg strength. The peak torque values of the quadraceps pointed towards differences between the reconstructed and opposite leg, even though there is strong evidence that there are neural connections associated with strength.
Parts of this test also suggest that there are different mechanisms for dynamic balance and postural control because the findings were so unmatched. No differences in posture were detected, although the ACL injured group had longer phase durations.
As far as posture goes, findings from this test allude to the concept of a neurologic crossover effect from the injured to the noninjured leg. This points towards the existence of a central postural control mechanism. Some attribute this problem to the fact that the athlete becomes less physically active after their injury. Hoffman, Schrader, and Koceja think that it happens because the body has a mechanism which keeps symmetry in both knees. If one is injured, the other's function is decreased to produce symmetry.
All things considered, both legs of the ACL group demonstrated lesser functional ability than the healthy bunch.
In summary, the ACL reconstruction participants displayed differences from a control group in areas of strength and recovery from perturbation while showing no difference in measure of static balance. Even though dynamic balance and strength measures were different, these variables were not correlated in the ACL or control groups. The findings imply disruption of a central control mechanism of posture, since the dynamic balance measure didn't display unlikeneses between the legs of the ACL group, but showed group differences between the ACL injured and control groups.