Now, after participating in a study conducted by scientists at the University of Louisville, UCLA and the California Institute of Technology, he can stand up on his own and remain standing and bearing weight for up to four minutes at a time. With periodic assistance, he can stand for up to an hour.

Summers also voluntarily can move his toes, ankles, knees and hips on command. With harness support and therapist assistance, he can make repeated stepping motions on a treadmill.

These unprecedented results are the subject of an article published today in the British medical journal The Lancet.

“This is a breakthrough,” said Susan Harkema, PhD, lead author on the article and a faculty member in the UofL Department of Neurosurgery. “It opens up a huge opportunity to improve the daily functioning of (people with spinal cord injuries).

“But we have a long road ahead,” she said.

Researchers described Summers, the only person to have been studied so far, as being an athlete in extraordinary physical condition before his injury. He had some feeling below the level of injury.

The rehabilitation research director at the Kentucky Spinal Cord Injury Research Center and director of research at theJewish Hospital & St. Mary’s HealthCare Frazier Rehab Institute, where the study took place, Harkema was one of two principal investigators on the study. The other was V. Reggie Edgerton, PhD, of the Division of Life Sciences and David Geffen School of Medicine at UCLA.

The study involved application of continual direct electrical current — via implanted electrodes — at varying frequencies and intensities to the part of the spinal cord that controls movement of the hips, knees, ankles and toes.

This type of epidural stimulation mimics signals the brain normally sends to initiate movement. Once that happens, the spinal cord’s own neural networks, combined with the sensory input from the legs to the spinal cord, can direct the muscle and joint movements required to stand and step with assistance on a treadmill.

The other crucial component of the research was an extensive regimen of locomotor training while the spinal cord was stimulated and Summers was suspended over the treadmill. Rehabilitation specialists helped move his legs to retrain his spinal cord neural networks to produce the muscle movements necessary to stand and to take assisted steps.

“This procedure has completely changed my life,” Summers said. “For someone who for four years was unable to even move a toe, to have the freedom and ability to stand on my own is the most amazing feeling. To be able to pick up my foot and step down again was unbelievable, but beyond all of that my sense of well-being has changed. My physique and muscle tone has improved greatly — so much that most people don’t even believe I am paralyzed. I believe that epidural stimulation will get me out of this chair.”

Harkema and Edgerton worked with nine other team members on the study, which was funded by the Christopher & Dana Reeve Foundation and the National Institutes of Health.

Harkema is director of the Reeve Foundation’s NeuroRecovery Network, which translates scientific advances into activity-based rehabilitation treatments. Edgerton is a member of the foundation’s Science Advisory Council and its International Research Consortium on Spinal Cord Injury.

They and their colleagues envision a day when at least some people with complete spinal cord injuries will be able to use a portable stimulation unit and, with the assistance of a walker, stand independently, maintain balance and execute some effective stepping.

Relief from secondary complications of complete spinal cord injury — including impairment or loss of bladder control, sphincter control and sexual response — could prove to be even more significant.

“The spinal cord is smart,” Edgerton said.