"It's fantastic," he said. "There's nothing better for the body, let alone for my head."
For now, the Food and Drug Administration has approved the devices only for use at a medical facility, as a therapy aid. But the goal for both products - ReWalk, by Israel-based Argo Medical Technologies, and Ekso, by California-based Ekso Bionics - is everyday use at home.
Locally, MossRehab has two ReWalks, and chief medical officer Alberto Esquenazi led clinical trials for the device.
Good Shepherd Penn Partners, a joint venture between Allentown-based Good Shepherd Rehabilitation Network and Penn Medicine, has an Ekso. And Magee Rehabilitation Hospital has an Ekso on order. Eythor Bender, chief executive officer of Ekso Bionics, said he could not think of another metro area with so many such devices.
"Philadelphia - it's a bionic hub," Bender said.
Each type of device has its advantages, but neither is cheap. Ekso costs $130,000, ReWalk $85,000 - each well more than 10 times the cost of a typical electric wheelchair. So to get insurers to pay, the device makers will have to demonstrate a medical benefit in a clinical trial.
Some users already are reporting benefits, said Kristin Gustafson, director of spinal-cord injury services at Good Shepherd Penn Partners. They say they experience less spasticity - the uncontrolled muscle tightness or spasms that plague some spinal-injury patients. They also report reduced swelling in the joints.
And the devices can make it easier to use the bathroom, as the standing position allows gravity to help empty the bladder, MossRehab's Esquenazi said. Long-term, proponents hope exoskeletons will help wearers maintain bone strength, and Webb says the devices are good for his circulation.
"Down the road, I would think it would be saving money because of all the issues that are going to come up later in life," Webb said.
Exoskeletons are not just for people with paralysis. Researchers are developing models for the able-bodied, to help them carry heavy weights.
Among them is HULC - the Human Universal Load Carrier, (pronounced "hulk") - also the work of Ekso Bionics. The device was licensed to Lockheed Martin in 2009 and lets the wearer carry up to 200 pounds on a 12-mile hike on one battery charge. It is undergoing testing with the Army.
There is pop-culture precedent, of course. Think of the Ripley character donning her powerful metal frame in the movie Aliens, or inventor Tony Stark of Marvel Comics and his Iron Man suit.
But strapping on an exoskeleton is an altogether different experience for someone who cannot walk.
Michael Sullivan, 46, of South Philadelphia, was paralyzed from the neck down in a diving accident at the Jersey Shore. Though he has since regained some use of his arms and trunk, he had not walked in nearly 18 years - until last month.
He received an e-mail inviting him to try out an Ekso at the Good Shepherd Penn Partners facility at 18th and Lombard Streets, and he knew immediately he had to do it.
"I didn't even finish reading the e-mail, and I was already calling on the phone," Sullivan said.
He tried it April 9, then again April 12 in front of an audience.
"Words cannot really describe how I feel at the moment," Sullivan said afterward, grinning widely. "If I would hit the lottery tomorrow, I would certainly try to get one."
Webb, who has tried both devices, said each had its pluses. For now, a physical therapist must push a button for Ekso to take each step, whereas ReWalk moves forward on its own, guided partly by a hip-mounted accelerometer that senses when the wearer is tilted in the right direction for the next step. Yet Webb said Ekso's gait feels more natural, whereas with ReWalk he sometimes drags one of his feet on the ground.
Bender, the Ekso Bionics official, said all Eksos will be modified within a few months so they can be fully user-operated.
Several similar devices are in development, said Arun Jayaraman, who tests them at the Rehabilitation Institute of Chicago. He predicted that they would be ready for home use in two or three years, though ReWalk's creators hope to get there as soon as next year.
Among the questions that need to be answered is whether some of the exoskeletons might impede potential recovery for patients who still have some function in their legs, Jayaraman said.
"People who have some capability, you don't want to make them passive," said Jayaraman, an assistant professor in the department of physical medicine rehabilitation at Northwestern University.
Webb, an archery hunter, suffered his injury when a bolt broke in his tree stand and the structure collapsed on top of him.
He has regained some function and feeling in his legs, and he says he is optimistic that an exoskeleton will help him maintain flexibility should he improve even further.
Even if he does not, he says, he wants one of the robotic devices for the independence.
Like for the times when he goes to watch his daughters play softball but cannot roll his wheelchair over bumpy ground to get to a good vantage point. So he ends up watching from beyond the outfield.
With an Ekso or ReWalk, on the other hand, Webb could get as close as he wanted.
What's more, he could stand up and cheer.
Contact staff writer Tom Avril at 215-854-2430 or firstname.lastname@example.org .