What started out as a typical sunny day in San Diego for Pat Brogan ended with a trip to the emergency room.

She was visiting the seaside city with her husband in August, and they thought it would be fun to rent two of Lime's electric scooters. A San Francisco Bay Area local and an avid cyclist and skier, Brogan liked the idea of zipping around town without using a car. After cruising along for about a mile, the couple started to descend a steep hill. Brogan, 63, eased on the brakes as her scooter gained speed — only to discover they didn't work.

"I blew through three intersections and luckily didn't get hit," she said. "I'm now going 25 mph heading toward six lanes of traffic."

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By the end of the day she'd be in the hospital. And she's not the only one. Starting in March, a handful of tech companies dropped thousands of e-scooters across nearly 100 US cities, and injuries have surged. Two people have been killed in electric scooter accidents. And trauma surgeons are reporting daily occurrences in hospitals from San Diego to Denver to Austin. Some of these injuries have been life-threatening; others have left people permanently disabled.

Silicon Valley is known for "disruption" — the idea of changing a service or product with technology to make it better. But, over the past few years, many of these innovations have produced unintended consequences. Facebook, originally conceived to "connect" people, is being blamed for undermining political elections around the world. Uber, devised to provide rides at the "touch of a button," is said to exacerbate traffic problems and clog city streets.

Now electric scooters — first seen as a fun way to solve the last-mile puzzle — are leading to deadly situations.

"This is disruptive technology," said Dr. Christopher Ziebell, emergency room medical director at Austin's Dell Seton Medical Center. "But this time the disruption is disrupting forearms, elbows and heads."

Scooter accidents happen for a lot of reasons. Sometimes the rider doesn't have control and runs into a curb or wall. Sometimes a car crashes into the rider. And sometimes, the scooter is the problem. Doctors and lawyers report instances when riders say a scooter's throttle got stuck or the brakes failed — like what happened to Brogan.

As she sped down that hill in San Diego, her husband yelled to Brogan to crash into him in order to break her fall. But she didn't want to send him flying. So moments before careening into the busy intersection, she held her arms up against her chest and slid the scooter out sideways.

"I went about 10 feet skidding on the pavement," Brogan said. "If I didn't crash when I did, I would've been killed. I'm sure of that."

Two surgeries later, Brogan ended up with a broken metacarpal held together with two metal pins in her right hand, along with a cracked knuckle joint, road rash and a hematoma down her entire right leg. Her left hand was so badly swollen, doctors had to cut off her rings.

Some might consider her lucky.

The gory details

Brogan's injury is just one of what looks to be thousands across the US, according to CNET's calculations. Because rentable electric scooters are so new, federal and local officials haven't started tracking accidents, and the companies have declined to release any stats. But some numbers are beginning to appear.

A quick sweep of local news stories brought up at least 50 incidents in the last six months. The tales are often gruesome. Like in San Antonio when a tourist accidentally turned into oncoming traffic and was hit head-on by a pickup truck. Or when an Oklahoma City man, traveling at full speed, clipped a metal drainpipe and was thrown over the handlebars — breaking both arms. Or when a rider in Cincinnati ran a red light and crashed into two pedestrians, sending them both to urgent care.

Injuries listed in these news reports range from broken ribs, collarbones, scapulas, ankles and femurs to collapsed lungs, ruptured spleens, multiple stitches, black eyes and head fractures.

This 31-year-old woman was in a scooter accident in Santa Monica, California, in October and broke three bones in her ankle that required surgery, a metal plate and screws. McGee, Lerer and Associates

CNET spoke to trauma centers in Denver, San Diego, San Francisco and Austin. All reported an uptick in injuries from scooter accidents. It's been just a few months since the vehicles were unleashed onto city streets, so emergency room doctors say they're only beginning to collect data.

"We are seeing some scary injuries," said Dr. Chris Colwell, chief of emergency medicine for Zuckerberg San Francisco General Hospital and Trauma Center. "There's still a lack of recognition of how serious this can be."

Colwell said his emergency room is logging about 10 injuries a week. They range from extensive bruising to severe head trauma. Given the hills in San Francisco, he also sees a lot of road rash.

"We saw a guy who fell over on his back this week," Colwell said. "He ended up going through so many layers of skin, we had to essentially put him to sleep to clean out the gravel embedded in his back."

San Francisco General Hospital is in the unique position of being the only Level 1 trauma center in the city, which means all significant injuries pass through its emergency room. Colwell, along with other doctors and public health specialists, decided in August to conduct an official study on scooter injuries. The idea: to track accidents and identify patterns.

"We'll collect data over the next six months, just to get a snapshot of what's happening," said Dr. Catherine Juillard, trauma surgeon at the hospital and one of the study leads. "We have to remember this is a public health issue. We have to make sure people are safe and that lives are saved."

Scripps Mercy Hospital in San Diego began tracking injuries in late summer. Dr. Vishal Bansal, medical director of trauma at Scripps, said they've documented more than 30 cases, for an average of about 10 a month. These cases only involve scooter riders, not pedestrians hit by the vehicles.

In Austin, the rate of accidents appears to be even higher. Doctors in Dell Seton's emergency room say they're seeing about 10 injuries a day.

"The vast majority end up getting discharged with cuts and scrapes, maybe a broken bone," said Ziebell. "But some injuries are significant."

The hospital has seen 37 severe traumas since April: eight head injuries, 23 orthopedic injuries, four facial injuries and two "other" injuries. In October alone, doctors say 18 people were admitted to either the intensive care unit or surgeries with overnight hospital stays.

"The folks that had severe head injuries, they're in for a long course of rehab," Ziebell said. "Some people may need lifelong care, like a nursing home."

"If you hit the ground at 20 miles per hour [on a scooter] or a baseball bat hits your head at 20 miles per hour, that's about the same thing," he added.

Do's and don'ts

With every disastrous accident, the scooter companies repeat the same mantra: "Safety is our very top priority," a Bird spokeswoman said.

"We strongly recommend reporting any damaged scooters or incidents that Bird scooters are involved in, as we have a support team dedicated to safety that is available around the clock to address questions and reports we receive," she added.

A Lime spokesman said, "Safety is incredibly important to Lime, and we're constantly educating our riders and developing new tools to promote safety and prevent accidents on our platform."

Other scooter companies have vehicles on city streets, too, including Scoot, Skip, Spin, Lyft and Uber's Jump. But Bird and Lime have more scooters in more cities than their rivals do. Lime said it's given more than 20 million rides around the world, and Bird's latest numbers show it's given more than 10 million. The scooters cost $1 to rent plus 15 cents for every minute of riding time.

Nearly 100 US cities now have dockless electric scooters for rent. James Martin

Bird and Lime are in the process of rolling out their own in-house scooter models, but for now they still use vehicles made by third-party manufacturers, including Xiaomi and Segway.

When someone buys one of these $500 scooters off the shelf, they get a user manual on vehicle maintenance and the do's and don'ts of riding. Recommendations include "wear a helmet," "avoid contacting obstacles with the tire" and be aware of speed because "the faster the scooter is, the longer it takes to stop." They say a rider should weigh no more than 220 pounds.

Xiaomi and Segway say scooters should be checked before every use and stored in a "cool, dry place." They also say not to ride in the rain or keep scooters outdoors for extended periods, adding that exposure to sunlight and extreme temperatures can "accelerate aging and compromise the scooter."

These recommendations aren't necessarily being followed with rentable scooters.

Bird and Lime warn riders only about hills and obstacles in online video tutorials, which aren't mandatory to watch. You'll see people of all sizes zooming along and even riding double. And the vehicles are usually kept outdoors all day and likely aren't being checked before each use. That doesn't even include what happens to scooters that are also being vandalized.

The fine print of Bird and Lime's user agreements tells riders not to exceed weight limits and to do a basic safety check beforehand. This inspection includes examining the brakes, lights, condition of the frame and trueness of the wheels. It's unclear if most riders know how to do this.

Lime had to recall one of its scooter models, made by the manufacturer Okai, earlier this month after a pattern emerged in which the vehicles' handlebars detached from the baseboard during rides. Company mechanics reportedly tested the scooters and found that some of them broke in half after only a few small hops, according to the Washington Post. More than 40 people reported being thrown from the scooters after the vehicles snapped midride.

"We are actively looking into reports that scooters manufactured by Okai may break," the Lime spokesman said. "As a precaution, we immediately decommissioned all Okai scooters in the global fleet."

Doctors say the fact that very few people wear helmets is also contributing to the rise in serious injuries.

Bird and Lime do have small stickers affixed to their scooters telling people to wear helmets, but the vehicles don't actually come with helmets. Colwell said only about 30 percent of scooter riders wear helmets, while around 72 percent of cyclists wear them.

Lime launched a $3 million safety campaign earlier this month called "Respect the Ride" that promotes safe riding behavior and gives out free helmets. And Bird says it'll also send a free helmet to anyone who uses its scooters. So far, Bird said it's given away more than 50,000 helmets.

But Bird was also instrumental in repealing California's helmet law for electric scooters. Under current state law, people must wear helmets while riding these vehicles, which can travel at 15 mph. Bird sponsored a bill in February to get rid of that law, which passed in September. Starting January, helmets will no longer be required for scooter riders in California.

Bird said its goal in sponsoring the legislation was to create "consistent ridership rules" between e-scooters and e-bikes since helmets aren't required with e-bikes.

You assume all responsibility

When you sign up to rent a scooter, you must click a button that says you agree to the app's terms of service.

This lengthy multiscreen agreement basically says users take on all responsibility for what happens during rides. Even when it may "result in injury or death to you or others," as Lime's agreement states.

That means if a car hits you, it's your responsibility. You hit a pedestrian? You're liable. What if the scooter's brakes fail? Still your fault.

"Rider agrees that Vehicles are machines that may malfunction," reads Bird's agreement. "Rider assumes full and complete responsibility for all related risks, dangers, and hazards."

Bird scooters are affixed with stickers that say "Ride Safely. Dara Kerr/CNET

These terms of service are similar to what people agree to when they sign up for apps like Uber and Lyft. The Lime spokesman said its agreement is "designed to be user friendly, and is written in plain language so that our riders are properly informed."

"Sometimes accidents do happen," he added, "which is why we have insurance policies and processes in place to support our riders and investigate all incidents."

Despite the user agreements, lawyers across the country say they're still getting dozens of calls from people hurt in scooter accidents.

"No one has ever read that user agreement," said Catherine Lerer, attorney for Santa Monica-based firm McGee, Lerer and Associates.

Lerer said she gets three to four calls a day. It got to be so much that she decided to file a class-action lawsuit against Bird, Lime, Xiaomi and Segway in October. The suit was filed on behalf of nine clients and lists 15 counts against the companies, including aiding and abetting assaults and gross negligence.

"Over and over, it's the same malfunctions that I'm hearing — the brakes failing, the throttle sticks and the scooter dies midride," Lerer said. "Something is not right."

"The scooter companies like to say safety is their number one priority, but prove it," she added.

Xiaomi and Segway didn't return requests for comment.

When asked to comment on the lawsuit, the Bird spokeswoman said, "Class-action attorneys with a real interest in improving transportation safety should be focused on reducing the 40,000 deaths caused by cars every year in the US."

Bryant Greening, attorney for the firm LegalRideshare in Chicago, said he's also gotten calls from scooter riders. The most common injuries he's hearing about involve user error, like when someone hits a pothole or runs into a curb and can't control the vehicle.

With their smaller wheels, scooters tend to be wobblier than bicycles and more susceptible to bumps in the road and uneven surfaces.

"If you hit a pothole on a bicycle with a big wheel, you could have a problem," forensic kinesiologist James Kent told CNET in an interview in July. "You hit a pothole on this little thing, you're going to go down."

Greening said such cases are difficult to litigate because it's hard to point to anything other than user error.

"You see these images of people bloody and broken and often there's no obvious recourse," Greening said. "These cases are so new and these companies are so new, they have not had the opportunity to make their way through the courts yet. It's still an evolving world."

Hospital bills

After Brogan's crash, her husband rushed her to the local urgent care. While waiting to be seen by doctors, she got several in-app messages from Lime saying she hadn't ended her ride and was still accruing charges.

"Scooter unsafe no brakes now in emergency room multiple fractures," Brogan wrote back.

Once out of the hospital, she emailed Lime to fully recount what happened. They had a brief back-and-forth in which Lime told her to file a claim for review. Brogan wrote back saying her out-of-pocket expenses totaled about $8,000 and asked if Lime would repay those losses. She said she never heard from the company again. Lime's spokesman declined to comment on Brogan's specific claim.

Now, three months later, the pins are out of her knuckles and her bruises have faded. She's still going through therapy to get movement and grip back in both of her hands. Even after everything, Brogan still appreciates the idea of electric scooters — with some reservations.

"It's a great concept," she said. "But it's not ready for prime time."

This article originally appeared on CNET, titled "Electric scooters are now disrupting wrists, elbows and heads"