We can divide today's surgical power tools into three distinct types: pen-style, stand-alone and modular systems. And each is powered one of three ways: pneumatic, electric or battery. Here's a look at the power sources and the features you should look for in power tools.

Traditional power
Pneumatic tools are the most mature segment of power tool technology. The technology is fairly simple, comprised of a control valve (foot or hand control), hose and the pneumatic tool itself. They are highly reliable with low mean time between failures; and because the foot controls are valves, not electric, they, too, are highly reliable. Able to achieve high-speed rotation (greater than 60,000 RPM) and develop lots of torque in a very small package, you need pneumatics when sculpting or dissecting dense bone, biometals or ceramics.

On the downside, pneumatic instruments are tethered to a bulky, high-pressure nitrogen hose. This can fatigue a surgeon during a long procedure. Another disadvantage is that most pneumatic instruments are noisy, and high-speed pen-style motors generate lots of heat and need continuous lubrication.

In addition, many outpatient facilities no longer incorporate nitrogen in their pipeline medical gas systems because actual use of nitrogen-powered instruments is minimal, and recent advances have been made in electric instrument power and speed. But for less than $1,000, you can have a nitrogen tank on a dolly to move between rooms.

Electric advances
Corded electric motors mean lighter weight and the capability to add wide varieties of attachments; a single control panel could drive shavers, drills, drivers and saws. However, as with the pneumatic tools, the instrument is still going to be tethered to something; in this case, a control panel.

The cords, control panels and footswitches are at the mercy of the condition and maintenance of cords and connectors. Although reliable overall, electrical systems include more components that can fail because of the complexity of the system.

Going cordless
Battery power means you get to ditch the cords and hoses, enhancing mobility and sterile technique. But there's a trade-off: Instruments are generally heavy if you want them to generate lots of power. The lower the speed and torque, the lighter the weight - and conversely, more power means more weight. The tools are very reliable, but you're at the mercy of batteries' being charged and ready.

Batteries last two years to five years, depending on their type, frequency of use and care. The older nickel cadmium batteries develop a memory if not fully discharged before recharging; this keeps the battery from taking and delivering a full charge. Smart battery chargers will automatically discharge batteries before recharging them, and newer lithium-ion batteries don't develop memory.

Pen-style systems
Pen-style motors used to power bits and burrs in small bone procedures and neurosurgery; they are also used in ENT, maxillofacial, dental, hand and podiatric procedures. These pen-style handpieces are generally very high speed. Traditionally these devices have been pneumatically powered by nitrogen, but with advances in tiny, powerful electric motors, this type of handpiece is now available in electric versions. Here are the features to consider in these instruments:

• Ergonomics. Look for pen-style systems that are designed to fit with the hand, so that the surgeon will be allowed fine control of the business end of the burr. Some manufacturers offer convertible designs that let the surgeon change the orientation of the handpiece. Remember, this type of surgical tool is used for precision work, so the surgeon needs the utmost control. Ergonomics are the first step toward that.
• Motor variety. Some manufacturers offer more than one motor so you can change them depending on whether you need a smaller profile or improved visualization by the surgeon. Attachments and tools required for any of the motors should be standardized, which will help decrease duplication of instrument inventories. Many pneumatic motors use a new lubricant/diffuser cartridge that simplifies set-up and allows up to one hour of continuous use.
• Weight and balance. Electric pen-style systems often offer the light and well-distributed weight surgeons desire.
• Speed. Manufacturers are offering upwards of 70,000 RPM and promising more torque. You're going to have to pay more for this, but if your surgeons don't feel they're getting enough power out of the current models, you might trial these to see if it makes a difference.

Stand-alone instruments
Stand-alone instruments are the big three of large bone surgery: the reamer/drill, the oscillating saw and the reciprocating saw. These are the largest and most powerful of the power tools category. Once only pneumatically powered, most are now battery powered. Two things to think about here:

• Battery sizes. Some manufacturers offer several battery sizes, so you can use different ones depending on procedure length, letting you minimize weight when long use isn't needed.
• Attachments. You want stand-alone instrumnets to be versatile; and the more attachments that are available or compatible with the brand you buy, the better. An example of an attachment would be a saggital saw on a reamer/drill.

Modular systems
The premise of these systems is that a single motor unit accepts a wide variety of attachments to perform multiple tasks. These system attachments typically function as shavers, drills, reamers, wire drivers, and small saws. Modular instrument systems come in corded and uncorded varieties. Uncorded varieties resemble drill motors; corded varieties typically have a footswitch-controlled power unit outside the surgical field and a sterilizable cord and handpieces that accept the attachments. Most arthroscopic shaver units are similarly configured and get double-duty as shavers and modular power tool kits.

Obviously you want many attachments, because you want a modular system for as many procedures as possible. Dedicated power cables for each handle type can enhance longevity.

Make it last
Powered instruments usually last about seven years to 10 years with regular use and proper maintenance, but I've seen some last 20 years. Word of mouth can be important for determining general durability; if you ensure staff are properly trained in maintenance, you can make your power tools last.