Recovery of locomotor function after treadmill training of incomplete spinal cord injured rats

Our long-term goal is to formulate and assess functional methodologies to enhance recovery of locomotor function in human subjects after incomplete Spinal Cord Contusion Injury (iSCI). This methodology could consist of locomotor training by active treadmill walking. Here, we present kinematic analysis of limb movements in rats with iSCI that have undergone treadmill-walking training. Video images were recorded during treadmill walking of iSCI rats at different intervals from 2 weeks to 24 weeks post injury and in age matched rats without injury. A kinematic analysis program was used to acquire the data, which was further analyzed using Matlab routines. Joint angles were analyzed using cross-covariance and limit cycles. In addition, the maximum flexion and extension and range of motion (ROM) determined. 2 weeks post iSCI the ankle was overextended, the hip under flexed, and ROM of the knee severely reduced thereby leading to disoriented gait. The phase-shift between the hip and knee joints observed in uninjured rats during treadmill walking was absent in the iSCI rats. Treadmill training improved hip flexion and ankle overextension. Knee ROM continued to be deteriorated. The treadmill training eventually led to recovery of coordinated locomotor function after 7 weeks, albeit with deformities in gait. This recovery of locomotor function occurred in spite of significant loss of axonal connections between the brain and the spinal lumbar segments at site of injury (assessed by histology after terminal data collection). The results suggest that functional recovery of locomotion could be an activity dependent process.