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 robotic surgery device maker MAKO Surgical (NASDAQ:MAKO.DL) fell as much as 14% following the release of select fourth-quarter earnings data -- although, shares have rebounded to be lower by only 4.5% as of this writing.

So what: MAKO is actually presenting at the JPMorgan Healthcare Conference on Wednesday and is widely expected to release its full-year results then. However, the data divulged today shows that MAKO sold 15 Robotic Arm Interactive Orthopedic systems, or RIOs, during the quarter, matching its total in the third quarter, and hitting the midpoint of its annual range of 42 to 48 systems. Also, MAKOplasty procedures rose by 20% over the sequential quarter to 2,904, and are 29% higher than the year-ago quarter.

Now what: Given that Intuitive Surgical (NASDAQ:ISRG) has had such resounding success with its da Vinci surgical system, everyone just sort of expected that MAKO would be a genuine competitor for Intuitive. Unfortunately, it hasn't worked out that way, and investors once again seem disappointed that MAKO merely met the midpoint of its own guidance. The rollout of MAKO's RIO system takes quite a bit of time and a lot of physician training, so patience is going to be required by investors in the meantime. I'll keep my eye on MAKO at these levels, but I'm clearly sold on Intuitive's growth and near-monopoly on the robotic surgery sector in the interim.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.