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), a medical device company that specializes in treatments of the spine, rocketed higher by as much as 25% today following an upgrade by Canaccord Genuity earlier in the week.

So what: It's been a delayed reaction, but Canaccord life sciences analyst William Plovanic referred to NuVasive as the "best asset in its class." He noted that there have been products which haven't performed as well as once anticipated and that legal issues still exist for the company. In fact, a hearing is scheduled for tomorrow whereby Medtronic (NYSE: MDT) will be seeking an injunction against NuVasive for allegedly infringing on some of its patents. Taking all of this into account, Mr. Plovanic placed a $19 price target on the company.

Now what: This is as good a time as any to be reminded that analyst upgrades and downgrades are largely one-day to one-week events and don't have much bearing on the long-term outlook of a stock. NuVasive is in one of my favorite fields -- medical devices -- and its sales are increasing nicely. Unfortunately, Wall Street estimates show that legal woes and the lag time related to introducing new products is going to stymie EPS growth for at least the next year or two. Following today's huge rally, I'm more than content to pass on NuVasive here and perhaps re-evaluate it on a dip.

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