Although the hand-held electronic devices being used in surgery are becoming more and more complicated, there is a high priority to keep the connectors and cables on them as simple as possible. Another priority is to ensure an easy and reliable connection of the device to the console, without compromising design and cost goals of either critical part of the system. If the device is disposable, connector cost also becomes a major issue. The engineer must create a design which keeps the cost of the disposable device as low as possible, yet adheres to high quality and performance levels historically associated with surgical devices. Often, a device handpiece, whether a catheter or surgical tool, uses several operational modes. A single device can use low level signals, high power RF, fiber-optics, or fluidics.

Connector requirements

In addition to the signals carried by cables and connectors, consider the overall environment in which they will be used. Questions to ask include:

• Should it be a locking connector for reliability, or non-locking for safety and simplicity?

• Should the cable/connector be sealed? If so, to what extent?

• Should it be shielded? Grounded or floating?

• Should a multi-mode hybrid connector be designed in or should separate connectors be used?

• Will the handpiece and cable be disposable, reusable, or a combination?

• How will it be sterilized?

• What are the handpiece weight, flexibility, and other ergonomic requirements?

The ideal connector will allow these requirements to change as the design evolves by having the flexibility to be backward compatible.

Hybrid connections

The contact blocks of some hybrid connectors can be assembled into a wide variety of configurations by using fiber optic, coax, and electrical contacts, as well as inserts for transmitting fluid or gas. These inserts operate inside self-aligning housings. Machined from solid brass, plated with electroless nickel and chrome, these corrosion-resistant housings are designed for long-term reliability in the most stringent of environments.

Gold-plated signal contacts, some tested to over 50,000 mating cycles, can be combined in the same connector with impedance-controlled coaxial contacts that operate at frequencies up to 10 GHz with a maximum of 1.35 dB signal loss. The hybrid line can incorporate up to 12 coaxial contacts in one connector.

Applications that need fiber optic lines can use single-mode contacts for 9/125 fiber lines and multimode contacts for 50/125 or 62.5/125 fiber lines as substitution for the coaxial contacts. Either a fiber or coaxial line can be inserted into each screw-machined part. Users can mix and match these contacts as needed.

Hybrid connectors transport fluid, gas, and signals using multiple conduits per connector. Each contact has an o-ring seal around each conduit to prevent leaking, and is tested up to 5 bar of pressure to earn an IP69 rating when mated. These fluidic-gas conduits are supplied preinstalled in the same connector with multiple signal contacts.

Disposable handpiece connectors

Because disposable devices are cost sensitive, there is a tendency to select an inexpensive connector plug. Unfortunately, these are usually mated to a low-cost receptacle. Engineers are forced to either over-design the disposable handpiece by using high-cost plugs to mate with a high-cost receptacle on the console, or to under-design the console by using a low-cost receptacle to mate with a low-cost plug on the handpiece.

Limited-use connectors (LUC) are specifically designed for disposables. Disposable plugs let equipment keep working with high-cycle lifetime receptacles. LUCs are available from 2 to 19 pins with solder or crimp contacts, and accept a maximum cable diameter of 8.7 mm.

In some LUCs, the plug can be mounted into a disposable handpiece or overmolded with a user's choice of shape. Both configurations are easily customizable and are well suited for compact designs. A third option is to mount the plug to a disposable cable, either with a one-piece back shell for simplicity and economy, or a two-piece back shell with a snap lock for easy assembly. The two-piece back shell offers additional features such as a rubber grip, standard and custom colors, and space to accommodate embedded electronics that could, for instance, disable the connector after a preset number of uses. Parts withstand EtO and gamma sterilization and conform to UL/IEC 60601 requirements.

Connecting the connectors

There are three basic cabling methods to choose from, depending on which is most appropriate and cost effective. The first is to use a long section of cable hardwired to the handpiece, where the handpiece, wire, and plug are all thrown away after a single use.

The second method uses a much shorter section of disposable cable, and the plug connects to an intermediate cable instead of directly to the console. The intermediate cable uses standard male and female connectors. This cable should be strong enough to withstand hundreds of autoclave cycles.

The third method, similar to the second, also uses an intermediate cable with standard cable connectors, but there is no disposable cable hardwired to the single-use handpiece. The LUC mounts directly to the handpiece using the snap-in version.