Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
2001-12-27
2003-12-30
Schaetzle, Kennedy (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
C439S909000, C439S827000
Reexamination Certificate
active
06671554
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the field of medical devices, and, more specifically, to electronic leads for implants and tools for using such electronic leads.
RELATED ART
Electronic implant devices are used in the medical profession to monitor health processes, such as glucose levels and heart activity, and to control or stimulate health processes, such as controlling heart rate and stimulating muscle function. Examples of implant devices include glucose sensors, pacemakers, muscle stimulators, and the like.
Implanted systems may include multiple devices connected for communication. In this case, a mechanism for electrical transmission between these devices is needed, whether for communication of data, power or both. Typically, due to power and size constraints, electrical transmission is relegated to a single pair of conductors. Two conductors are typically sufficient to send ground and supply voltages from a power supply to an implant device, or, for communication of data between two or more devices.
Because implantable leads are designed to be implanted in the subcutaneous tissue of a patient's body, the dimensions of such leads can have an impact on the level of comfort of the implant patient and the external appearance of the implant path. Also, the path of the lead implant may be substantially determined by the other devices within the implanted system, limiting options for selecting a least offensive implant path. Typically, a lead of relatively small dimensions and, in particular, a relatively small diameter dimension, will minimize patient discomfort and noticeable protrusions along the implant path. Accordingly, there is a demand in the industry for minimizing the diameter dimension of implantable electronic leads, particularly in sensor applications where, for example, the size of a glucose sensor is of the same order as the diameter of the electrical lead.
Small devices like the glucose sensor may be implemented with no power source of their own, and rely on power extracted from the data signal itself. As power levels are typically low to begin with, it is important that the electrical lead have a high conductivity value to minimize power attenuation over the length of the lead. The lead should also be sufficiently strong and flexible to resist breaking due to any stresses placed on the lead by the insertion process during the implant operation, as well as stresses caused by movement or pressure of the patient's body during normal activities. Unfortunately, the need for strength, flexibility and high conductivity often limits how small the diameter of an electrical lead can be made.
Other problems with implantable leads concern the connectors used to couple the leads to the implanted devices. For example, most connector structures are of greater diameter than the lead itself. This can cause extra trauma during insertion as these nonuniform structures catch and tear in the body tissues. Further concerns are with the integrity of the connections achieved by the connectors. It is important that the connectors not become disconnected during use. Connection integrity is typically ensured by complicated cam structures or external screws which the surgeon must manipulate during the implant process to lock the connection. Also, fluids and other matter from the exterior implant environment can penetrate the connectors, resulting in a short between conductors. Pacemaker leads have used a single rubber O-ring to seal out fluids. However, there is a need for connectors that can provide a more efficient seal to inhibit such short circuits from occurring.
Finally, the junction between the cable and the connectors is often placed under greater amounts of stress than other portions of the lead. Therefore, the lead is more likely to fail at that point. Pacemaker leads have tried to overcome this weakness in the cable by molding large ball-like or disk-like rubber structures around the lead at those points to resist excessive flexure. Such external structures only serve to widen the diameter of the cable at those points, generate unwanted protrusions, and complicate insertion procedures.
Thus, there remains a demand in the industry for new and improved electrical lead structures that have reduced diameter dimensions, yet which do not compromise other operational characteristics, such as the strength to resist stress and the conductivity to minimize attenuation. Further, lead structures are needed that minimize diameter-related anomalies caused by connectors and stress relieving structures, and that provide secure connections without requiring complicated manipulations by a surgeon during insertion.
SUMMARY OF THE DISCLOSURE
Embodiment of the present invention relate generally to implant devices having one or more lead cables for the transmission and/or reception of electrical signals between two or more electronic devices in a medical implant environment. Particular embodiments relate to cables, connectors and tools for such devices and methods of making and using the same, which address one or more of the concerns and demands in the industry as noted above.
Embodiments of the invention may employ cable structures that reduce the diameter and improve the strength of the lead, as compared to prior cable technologies. In this manner, smaller leads may be used in implant procedures to reduce the initial physical trauma of the implant procedure, and the continuing discomfort and physical trauma caused by the constant presence of the implanted lead, without compromising the strength and conductivity of the lead. Embodiments of the invention may also employ connector structures that simplify the operation and enhance the reliability of the lead connectors, as compared to prior connector configurations. Thus, implant leads may be connected quickly and easily, without sacrificing retention strength, circuit integrity or the surgeon's confidence that a connection was made. Further, embodiments of the invention may also employ insertion tools to minimize surgical trauma and maximize surgical efficiency, as compared to prior implant procedures. In this manner, leads may be implanted quickly and easily, without sacrificing safety. Various preferred embodiments may be particularly suited for implant environments. Other preferred embodiments may be employed in external (non-implant) environments.
A sensor lead according to an embodiment of the invention includes a coaxial cable structure, a female connector and a male connector. The cable structure includes an outer insulator tube containing an inner coil and an outer coil separated by an inner insulator tube. The inner and outer coils may be helical ribbon conductors that each represent a separate electrical channel. In some embodiments, the helical ribbon conductors include multiple adjacent wires configured in a ribbon strip that is twisted about a central axis. In this manner, a strong and conductive cable is formed that is also both thin and flexible. In some embodiments, each wire is made up of a highly conductive silver core surrounded by a durable cobalt alloy. According to one aspect of the invention, a tolerance value may be determined for maximum radial offsets by any one wire in a coil, to prevent stress points along the cable. Further, a nominal coil spacing distance may be determined to provide a desired balance of strength and flexibility.
A female connector according to an embodiment of the invention has a female connector body including two conductive body members separated by a middle insulator. The female connector body defines an inner cavity configured to accept a male connector via insertion. Within grooves along the interior walls of the connector body, the connector includes the following: respective conductive tension members electrically coupled to each of the conductive body members, and a seal molded into the middle insulator to electrically isolate the interiors of the conductive body members from each other. In some embodiments, the conductive tension members are i
Byers Charles
Chernoff Edward
Gibson Scott R.
Shah Rajiv
Foley & Lardner
Medtronic Minimed Inc.
Schaetzle Kennedy
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