Shares of Sensei robotic-catheter maker Hansen Medical (Nasdaq: HNSN) have more than doubled over the past 12 months, against a mere 20% gain for the S&P 500. Hansen booked most of its gains over just the past month, as shares bounced off a June 13 low to rise 70% in the ensuing four weeks -- leading fellow Fool Rick Munarriz to name the stock one of last week's "biggest winners" on Wall Street.

But is the run-up for real?

Bull thesis
Bulls would argue that it's not only for real -- it's also not done yet. On June 29, investment banker Piper Jaffray urged investors to buy Hansen in anticipation of a new vascular robotic system's gaining FDA approval. Piper posited a $5 stock price for Hansen shares, suggesting there's another 10 percentage points' worth of profit left in the stock.

Bear thesis
Bears, on the other hand, have at least three reasons to distrust Hansen's run-up. For one thing, there's the record of the analyst who helped spark it. According to our CAPS records, Piper Jaffray is one of the least accurate medical-device stock pickers out there, getting nearly twice as many of its recommendations wrong as right.

For another, stent-sales growth has decelerated, a trend that led Johnson & Johnson (NYSE: JNJ) to exit the market last month. Recent studies have raised concerns of the overuse of stents versus drugs and noted a decrease in heart-related procedures. Potentially, reduced stent usage could impinge on the need for Hansen's Sensei system. However, stent grafts are still a large market, Medtronic (NYSE: MDT), Abbot Labs (NYSE: ABT), and Boston Scientific (NYSE: BSX) continue making the widgets, though, so J&J’s retreat may be more of a company-specific problem than an industrywide issue.

Most crucial are the issues with Hansen itself. Unprofitable today, burning cash, and with losses expected to grow throughout 2011 and into 2012, Hansen depends greatly on the kindness of strangers. Until it can pay its own way, the company must find lenders or new share-buyers willing to give it money -- or else close up shop. Current cash levels are good only to keep the company in business for about 18 months at current burn rates. After that -- expect dilution.

Foolish takeaway
Hansen is a prototypical ground-floor stock. Early adopters are flocking to it in hopes of owning a winner early, before it generates the kinds of profits that attract the rest of us investors -- and drive up the stock price. It's a high-risk, high-reward strategy. My biggest fear: Hansen may not survive long enough to pay off.

Do you think Hansen has a future? Head over to Motley Fool CAPS now, and tell us why.

Fool contributor Rich Smith owns no shares of any company named above. The Motley Fool owns shares of Abbott Laboratories, Medtronic, and Johnson & Johnson. Motley Fool newsletter services have recommended buying shares of Abbott Laboratories and Johnson & Johnson and creating a diagonal call position in Johnson & Johnson.

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