So What Exactly Is a ‘Stress Reaction’ and What Does It Mean for Yu Darvish’s Future?

While a clean MRI is always best when it comes to an athlete’s health, there was a convoluted sense of relief when the latest scan on Yu Darvish turned up a stress reaction in his right elbow. There was a triceps strain as well, possibly a compensatory injury, but the stress reaction is the worrisome part of the whole deal.

“We do believe the stress reaction is what has been bugging him all the way back to the end of May,” Theo Epstein told members of the media during a conference call Wednesday. “At least now we understand what he’s been dealing with.”

“We had a pitcher last year, Alec Mills, who experienced the same thing. It took him a while to get diagnosed. Stress reactions are difficult to diagnose. They don’t show up right away on normal scans.”

Some have called this latest diagnosis “essentially a bone bruise,” which, while not necessarily untrue, can be very misleading for those who’ve received their medical training from Twitter University. When you think of a bruise, you figure a little rest and ice and you’re back good as new. There’s also the matter of two previous clean MRIs on Darvish that revealed nothing, thereby leading some to conclude that this was all in the pitcher’s head.

That’s why Dr. Stephen Gryzlo, the Cubs team orthopedist, opted to go with an arthrogram MRI this time. In said procedure, a solution made from a combination of X-ray dye, lidocaine, and MRI contrast is injected into the joint to facilitate more detailed images than a traditional MRI would be able to provide.

As you can imagine, using a fluoroscope to pump stuff into a joint is going to cause a little discomfort — hence the lidocaine — and could cause inflammation or irritation beyond that which precipitated the test in the first place. And in case you’re wondering, yes, some of this information was part of a recent lecture I attended (notes below).

Arthrogram MRI

— Sahadev Sharma (@sahadevsharma) August 21, 2018

Just the last one. So they were able to find it this time. Obviously didn't want to do it earlier because of the reason you pointed out

— Sahadev Sharma (@sahadevsharma) August 21, 2018

Now we have a little better understanding of why this thing took so long to diagnose, which surely gave Darvish some measure of relief. It can be incredibly taxing when you know there’s something wrong with your body even though nothing is showing up in tests. Having this understanding, even though some no doubt believe it’s something the Cubs just decided to make up, will be a good thing in the end.

Speaking of understanding, perhaps I should get around to answering both parts of the titular question. First up: What exactly is a stress reaction?

According to a presentation by Dr. Lee Kaplan of the University of Miami’s sports medicine department, a stress reaction is a precursor to a stress fracture. These reactions occur as a response to bone being stressed beyond its normal elastic range.

Citing Wolff’s Law (which states that bones will adapt to the load under which they are placed), and Young’s Modulus (a measure of stiffness), Dr. Kaplan describes a stress reaction as the body’s inability to form new bone at a rate commensurate with the stress being placed on it. Left untreated, this stress can eventually lead to fracture(s) as the bone’s integrity continues to erode. In other words, being “Chicago tough” could have led to an actual break.

The mechanism, or cause, of injury can come from two things: Impingement of the olecranon, the part of your ulna (the longer, thinner bone in your forearm) that forms the point of your elbow, or “excessive tensile forces of the triceps on the olecranon during acceleration phase of throwing.” Huh, seems like we’ve heard about those issues with Darvish from the start of all this. But if that’s the case, why didn’t anyone notice it sooner.

As Dr. Kaplan points out, and as we saw with Darvish, X-rays and MRI scans may appear completely normal. And even though the olecranon is the most common fracture in baseball, with pitchers being most susceptible to them, such injuries only account for 0.8 percent of all high school sports injuries. One could surmise that reactions are more common than that, but the moral of the story is that these things really don’t happen often enough to have much attention paid to them.

Now we come to the second question: What does this mean for Darvish’s future? The outlook is actually very good, and not only because it involves non-operative treatment. Dr. Kaplan recommends a minimum six-week break from throwing, with a program starting back up once the subject exhibits a full range of motion and no pain following “provocative tests.” He also mentions the possibility of a bone stimulator, but notes that there isn’t sufficient evidence to support such a measure.

Provocative tests? Bone stimulator? Makes it sound like the rehab process involves having someone read 50 Shades or watch Basic Instinct and 9 1/2 Weeks.

Anyway, the good news here is that, regardless of whether Darvish consumes any mild erotica, his outlook is very good. Epstein said that the latest MRI revealed that the pitcher’s reconstructed right UCL is still stable and healthy, so there are no worries of a second Tommy John surgery.

As for the prospects of getting past his current issue, the study cited seven professional baseball players who underwent non-operative treatment for stress reactions, all of whom returned to playing professionally. The average time to resume a throwing program was eight weeks and they returned to live action in around 12-14 weeks.

Six of the seven players were still playing professionally four years later, with the other having been traded and thus no longer available to the study. Given the relatively short career arc of a professional athlete, those are very strong numbers. If he’s able to follow a similar path, Darvish should be throwing again by mid-to-late October and should be perfectly healthy by the start of spring training.

It’s also possible that the clean slate of sorts will have him in a better place psychologically and emotionally. Much has been made about those aspects of his personality and the ordeal of this injury no doubt swayed peoples’ views of Darvish as a competitor. Whether this latest revelation changes that from the outside or not, Darvish is no doubt looking forward to coming back in 2019 and beyond to show what he can do.