Serial kinematic analysis of canine hind limb joints after unilateral L4-S1 dorsal root ganglionectomy: Insights into locomotor control mechanisms.

Following unilateral L4-S1 dorsal root ganglionectomy to deafferent the hind limb, each of six dogs showed increased extension of the ipsilateral hip, knee and ankle joints during most of the gait cycle throughout a 26-week period of observation. The contralateral hind limb joints initially exhibited increased flexion during gait (which presumably compensated for the increased extension of the deafferented limb), but over time contralateral joint extension gradually increased, i.e. the movement of the joints of the contralateral limb progressively began to resemble that of the ipsilateral joints. We suggest that the long-term kinematic changes in both limbs (increased extension) occurred because of neurological changes in spinal cord structure, associated with death of sensory neurons and an associated increase in the influence of descending systems (e.g. vestibulospinal) on motoneurons. These results emphasize the importance of long-term observation of kinematic patterns after experimental induction of neural lesions and indicate that the contralateral limb should not, a priori, be considered a valid control in such studies.