ACL rupture can change brain function

It has long been known  that an ACL rupture leads to proprioceptive deficits in the knee, but what changes actually occur in the brain? Kapreli et al (2009) studied 17 men (average age 25.5) with MRI-confirmed complete ACL rupture in the right knee.

The men were having difficulties due to their ACL deficiencies, confirmed by scores less than 60% on the global rating scale, less than 80% on the activities of daily living scale, a timed hop test less than 80% of predicted, or episodes of the knee giving away. These men were compared to 18 matched, healthy controls.

The men were asked to move their knee into flexion and extension on command in a functional MRI. The MRI showed increased activity in the contralateral presupplementary motor area (pre-SMA), the contralateral posterior secondary somatosensory area (SIIp) and the ipsilateral posterior inferior temporal gyrus (pITG).

These findings were in contrast to the pattern in controls, where signal was significantly higher in the primary sensorimotor areas bilaterally, the contralateral thalamus, posterior parietal cortex, basal ganglia-external globus pallidus, secondary somatosensory area, cingulated motor area, premotor cortex and the ipsilateral cerebellum.

The pITG’s is located in the visual cortex and activation of this area in the ACL deficient subjects suggested that they needed visual feedback to compensate for proprioceptive deficits. Both ACL deficient subjects and controls were allowed to look at a mirror inside the MRI to help them initiate movement. The healthy people did not need to look at the mirror, whereas most ACL deficient subjects did.

Activation of the pre-SMA area activation may imply that injured patients’ brains require more intensive planning before knee movement. The pre-SMA’s role is in planning complex movements.

Kapreli et al (2009) have now established that an ACL injury causes changes in cortical organization. The authors pose a couple questions. How long is too long to wait for surgical repair? Can different rehab programs reverse these brain changes?

From studies on stroke patients (eg induced constraint) and amputees, we know the potiental our brains have for plasticity. We know that rehab programs can help reorganize and strengthen neuronal connections, but such research would help strengthen our beliefs.

I have an interesting idea from this article involving mirrors.Ramachandran invented the mirror box. Butler and Co have used mirror boxes to rehab complex regional pain patients for the past few years with great success. Dr House MD in a recent episode used a mirror box to cure someone’s chronic phantom pain.

I would like to see a study using mirror boxes to improve proprioception post ACL surgery, and whether this improves rehab times.

Anyone?