There’s no guarantee these companies will replicate their success next year. But by examining catalysts and drivers of growth, investors are better positioned to pick winners in 2017. So what did 2016’s top gainers do right—and what might investors learn from their example?We looked at the NASDAQ to see which medical device stocks outperformed the rest. Below, we consider each—and look at the possible reasons for their soaring share price.

5 top-performing NASDAQ medical device stocks of 2016

Ekso Bionics Holdings (NASDAQ:EKSO)Heska (NASDAQ:HSKA)AxoGen (NASDAQ:AXGN)BioTelemetry (NASDAQ:BEAT)Exact Sciences (NASDAQ:EXAS)

1. Ekso Bionics Holdings

With year to date (YTD) gains over 250 percent, Ekso Bionics tops our list of best medical device stocks in 2016. This company builds wearable exoskeletons to help patients recovering from stroke or spinal cord injury. The devices also help to prevent injuries that sometimes occur during physical rehabilitation.Ready to wear and battery-powered, these robotic exoskeletons seemed to draw plenty of investor interest in 2016. Undoubtedly, much of that interest resulted from a major contract Ekso Bionics secured early in the year: The Defense Advanced Research Projects Agency’s (DARPA) Warrior Web program asked the company to develop an exoskeleton for soldiers to assist with load carriage.A few months later, Ekso Bionics received more good news: their GT Robotic Exoskeleton was cleared by the FDA for use with patients who have suffered a stroke or spinal cord injury.On the heels of these developments, Ekso Bionics elected to list on the NASDAQ. Previously traded solely over the counter, the company began trading on the NASDAQ on August 9, 2016. And as its place in this article shows, Ekso Bionics soon proved itself a top gainer.

2. Heska

Heska focuses on veterinary medicine, developing diagnostic and digital imaging solutions to keep Fido healthy. And in 2016, those products kept the stock healthy too: Heska has seen YTD gains of 75 percent.What’s behind that performance? The company has had a relatively quiet year, news-wise. But toward the end of 2015, Heska did acquire Cuattro Veterinary, which seems to have helped the company to grow its digital radiography and imaging divisions.

3. AxoGen

“It’s time to rethink nerve repair”: so declares AxoGen’s website. In 2016, it seemed many investors agreed. They bought stock in this medtech company, which has seen its share price soar 69 percent YTD.AxoGen makes surgical solutions, like the AxoGuard NerveConnector or AxoGuard NerveProtector. It also develops evaluation tools, which can help physicians detect and assess nerve issues.AxoGen bills itself as the “only company focused on peripheral nerve repair solutions”—which would suggest it has somewhat of a monopoly. That market share grew in 2016, as AxoGen launched Avive Soft Tissue Membrane: according to the press release, “the company now estimates that the current addressable market of AxoGen’s nerve product portfolio has increased from $1.6 billion to $1.8 billion.”Those are some big numbers—and given the stock’s YTD performance, it seems investors took note.

4. BioTelemetry

BioTelemetry works with wireless technology. Their Mobile Cardiac Outpatient Telemetry (MCOT) system, for example, transmits ECG data to a monitoring center, where it is analyzed and forwarded to the patient’s physician. As such, this product line facilitates constant analysis of a patient’s cardiac health—and it does so in real time.BioTelemetry had a strong 2016. In the third quarter, the company actually had its highest ever quarterly revenues—$53.1 million. It appears some investors expect that performance to continue as the stock is up 67.38 percent YTD.

5. Exact Sciences

Rounding out our list? Exact Sciences, which has seen YTD gains of 64.25 percent. This company makes Cologuard, a kit that collects and registers abnormal DNA in order to diagnose colon cancer. In 2016, that kit won the Prix Galien Award for Best Medical Technology Product.As for other big wins in 2016? Exact Sciences expanded Cologuard’s in-network coverage, with insurers like Anthem BlueCross, Health Care Service Corp., Blue Shield and Florida Blue choosing to cover the Cologuard kit. The company believes this will further growth going forward, and in 2016, it seemed investors agreed.