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 Hanger Orthopedic (NYSE: HGR) plummeted more than 20% in early trading after issued worse-than-expected fourth-quarter guidance. The stock closed off 15.7%.

So what: Third-quarter earnings came in a penny ahead of expectations at $0.46 on $235.2 million in revenue, about $2.5 million short of estimates.

Now what: For Q4, the prosthetic-device specialist expects to earn $0.49 to $0.52 in profit on $243 million to $247 million in revenue. Analysts, by contrast, had been projecting $0.58 a share on $261.9 million in sales. Does the miss matter? Would you buy shares of Hanger Orthopedic at current prices? Please weigh in using the comments box below.

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Fool contributor Tim Beyers is a member of the Motley Fool Rule Breakers stock-picking team. He didn't own shares in any of the companies mentioned at the time of publication. Check out Tim's portfolio holdings and Foolish writings, or connect with him on Google+ or Twitter, where he goes by @milehighfool. You can also get his insights delivered directly to your RSS reader.

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