In the U.S., 3.6 out of 1000 school-aged children are diagnosed with cerebral palsy (CP). Their symptoms include abnormal gait patterns which results in joint degeneration over time. Slow walking speed, reduced range of motion of the joints, small step length, large body sway, and absence of a heel strike are other difficulties that children with CP experience. A subset of these children exhibit crouch gait which is characterized by excessive flexion of the hips, knees, or ankles.
Today, a team led by Sunil Agrawal, professor of mechanical engineering and of rehabilitation and regenerative medicine at Columbia Engineering, has published a pilot study in Science Robotics that demonstrates a robotic training method that improves posture and walking in children with crouch gait by enhancing their muscle strength and coordination.
Crouch gait is caused by a combination of weak extensor muscles that do not produce adequate muscle forces to keep posture upright, coupled with tight flexor muscles that limit the joint range of motion. Among the extensor muscles, the soleus, a muscle that runs from just below the knee to the heel, plays an important role in preventing knee collapse during the middle of the stance phase when the foot is on the ground. Critical to standing and walking, the soleus muscle keeps the shank upright during the mid-stance phase of the gait to facilitate extension of the knee. It also provides propulsive forces on the body during the late stance phase of the gait cycle.
“One of the major reasons for crouch gait is weakness in soleus muscles,” says Agrawal, who is also a member of the Data Science Institute. “We hypothesized that walking with a downward pelvic pull would strengthen extensor muscles, especially the soleus, against the applied downward pull and would improve muscle coordination during walking. We took an approach opposite to conventional therapy with these children: instead of partial body weight suspension during treadmill walking, we trained participants to walk with a force augmentation.”
The research group knew that the soleus, the major weight-bearing muscle during single stance support, is activated more strongly among the lower leg muscles when more weight is added to the human body during gait. They reasoned that strengthening the soleus might help children with crouch gait to stand and walk more easily.