By Patrick May

When Indianapolis Colts defensive end Trent Cole sacked Oakland Raiders quarterback Derek Carr early in the fourth quarter of their Christmas Eve game, the devastating hit left not only a broken fibula for the MVP contender but raised a lot of questions about the ankle bone in question.

Carr was scheduled to undergo surgery today in Los Angeles, and while Raiders coach Jack Del Rio initially said the star QB would be out indefinitely, Carr was determined to get back on his feet in time of a possible Super Bowl run, tweeting “I will bounce back and be on my feet in no time!”

We don’t know exactly the scope of Carr’s injury. But with the help of Dr. Nick Grosso, a sports medicine surgeon and president of The Centers for Advanced Orthopaedics, here’s a primer on the fibula, how a break is repaired, and other issues that the Raiders quarterback may be facing in the coming weeks and months.

What’s a fibula?

This long, thin and lateral bone runs along the lower leg, parallel to the tibia, or shinbone, and plays a starring role in stabilizing the ankle and supporting lower-leg muscles. The fibula is a small fry compared with other bones, such as the femur, or thigh bone, which is the longest, heaviest and strongest in the human body.

“The fibula’s an accessory bone in the lower leg,” says Grosso. “As a result, it only has to support between 14 and 17 percent of the body’s weigh while the vast majority of weight goes through the shin bone.”

Do they break often?

Grosso says the fibula “is a very common bone to fracture and it can break in a bunch of different ways. What matters most to the surgeon is where it broke; it’s a fairly long bone that starts at your knee and runs to the ankle joint, and if it breaks in the upper half we usually don’t mess with it at all and we just let it heal on its own.”

He says it’s fairly rare for the fibula to break in that upper section. But when it fractures at the other end near the ankle, things can get messy, as Carr found out.

“If it breaks down at the very end,” he says, “and especially if it’s on the inside part of the ankle, that’s when you’d need surgery and that plate-and-screws kind of thing.”

So Carr’s surgery probably involves a plate and screws?

Grosso can’t say for sure, but “after watching that play on TV over and over, it looked to me like his ankle rolled under him and the pressure from the other player came down hard on him. So it looks like he’s sustained a significant injury. But that’s all conjecture.”

So determining the amount of injury around the ankle is crucial?

There are a couple of major ways a fibular fracture can play out, depending on how badly the ankle joint is impacted by the break. There are isolated fibular fractures, when the ankle joint is  unimpaired and the injury can be treated simply, with the use of a brace. These are called “lateral malleolus fractures.” Anyone who’s twisted an ankle playing volleyball knows how miserable they can feel, but they heal on their own. However, if the inner side of the ankle gets hurt, a so-called “fibula fracture with associated ankle injury” will require more invasive treatment and surgery is usually needed to stabilize the ankle joint. Derek Carr can probably relate.

What’s a fibula fracture feel like?

“It’s not the most painful,” says Grosso, pointing out that “the amount of pain is related to the amount of force applied, so since the bigger bones require more force to break that would be more painful. The fibula is smaller than other bones, and from looking at Carr’s initial reaction, I’d say he either heard it or felt it snap. I’m not a lip-reader, but apparently he was either saying ‘it’s bad’ or ‘it’s broken.”’

Why didn’t they perform surgery immediately?

“If there’s too much swelling,” says Grosso, “it can be tough closing the skin. We let the swelling go down for a few days and this certainly didn’t require an emergency surgery since the season is almost over. If this had happened to him in week one through five, you might have seen surgery that night because he could have been back in for the end of the season.”

Are you saying that Carr won’t be back for a possible Super Bowl game, even if he thinks he will be?

“This guy won’t be back in time for a possible Super Bowl – that ain’t happening,” he says. “There will be six to eight weeks minimum for healing and Super Bowl will be over by then.”

Can you describe the kind of surgery Carr may be facing today?

“It typically takes 45 minutes to an hour,” Grosso says. “Sometimes, if there’s an injury to the inside of the ankle that would require more surgery and make it longer. But just plating the fibula doesn’t take long at all.”

How does one plate a fibula?

“You make an incision at the tip of fibula and up the leg, cut down to the bone, take the muscle and everything off, then put a metal plate on the side and put screws in above and below the fracture to hold the plate in place. The plate acts as an internal splint.”

So what’s Carr’s prognosis?

Grosso says “biological healing occurs and then you don’t need the plate anymore and you can take it out or leave it, which is what we do with older people. With Carr, there are pros and cons, but they’d probably leave it in because if you take it out that require another mending period. My bet is that it’ll stay in the rest of his life.”

After six to eight weeks, Carr could start a gentle rehab program, says Grosso, adding that “it’ll then take an additional four to six weeks before he can play again because even once the bone has healed  the soft tissue around it also needs to be adapt and remodel itself. But he could be training and even throwing again in three months.”

Read more here