Tiny mechanical wrist gives new dexterity to needlescopic surgery

Tiny mechanical wrist could improve minimally invasive surgery

With the flick of a tiny mechanical wrist, a team of engineers and doctors at Vanderbilt University’s Medical Engineering and Discovery Laboratory hope to give needlescopic surgery a whole new degree of dexterity.

Needlescopic surgery, which uses surgical instruments shrunk to the diameter of a sewing needle, is the ultimate form of minimally invasive surgery. The needle-sized incisions it requires are so small that they can be sealed with surgical tape and usually heal without leaving a scar.

Although it’s been around since the 1990s, the technique, which is also called mini- or micro-laparoscopy, is so difficult that only a handful of surgeons around the world use it regularly. In addition, it has largely been limited to scraping away diseased tissue with sharp-edged rings called curettes or burning it away with tiny lasers or heated wires.

So a research team headed by Associate Professor of Mechanical Engineering Robert Webster has developed a surgical robot with steerable needles equipped with wrists that are less than 1/16th of an inch (2 mm) thick. The achievement is described in a paper titled “A wrist for needle-sized surgical robots” presented in May at the International Conference on Robotics and Automation in Seattle.

The new device is designed to provide needlescopic tools with a degree of dexterity that they have previously lacked. Not only will this allow surgeon-operators to perform a number of procedures such as precise resections and suturing that haven’t been possible before, but it will also allow the use of needles in places that have been beyond their reach, such as the nose, throat, ears and brain.

“The smaller you can make surgical instruments the better…as long as you can maintain an adequate degree of dexterity,” said Professor of Urological Surgery S. Duke Herrell, who is consulting on the project. “In my experience, the smaller the instruments, the less post-operative pain patients experience and the faster they recover.”

That has certainly been the case with traditional minimally invasive surgery (MIS), which has become increasingly common in recent years. This method, which involves operating with instruments inserted through incisions that range from 3/8th to 3/16th of an inch (10 mm to 5 mm), generally causes patients less pain, less tissue damage, less scarring and shorter recovery periods.

The effort to adapt robotic technology to MIS has been dominated by Intuitive Surgical’s da Vinci Surgical System, a robotic surgical system designed specifically for the minimally invasive approach. Depending on the type of surgery, it requires incisions that are 1/3 of an inch (8 mm) or 3/16th of an inch (5 mm).

“Although it works very well for abdominal surgery, the da Vinci uses a wire-and-pulley system that is extremely difficult to miniaturize any further, so it won’t work in smaller spaces like the head and neck,” said Webster.

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