Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of NuVasive (Nasdaq: NUVA) rallied as much as 20% earlier in the trading session after the medical equipment manufacturer reported better-than-expected first-quarter results.

So what: For the quarter, NuVasive reported a 22% rise in revenue to $151.9 million and an adjusted profit of $0.20. This compares to Wall Street's expectations for an adjusted profit of $0.18 on $143.5 million in sales. NuVasive also reaffirmed its previous revenue and EPS full-year guidance. If there was one negative to report, the company's gross margin fell to 75.7% from 81.1% a year earlier as expenses rose.

Now what: NuVasive's management team seemed pretty pleased with the company's market-share taking results thus far, but I would be more concerned with the falling margins. Although the company kept its full-year forecast unchanged, I'm still not sold on NuVasive at 19 times forward earnings -- especially with costs rising.

Craving more input? Start by adding NuVasive to your free and personalized watchlist so you can keep up on the latest news with the company.