JPH0235583B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bone growth stimulator, and more particularly to a connector for use in a lead wire of a bone growth stimulator.

U.S. Pat. No. 59,443 to Whitscomb et al., filed July 20, 1979, describes a billet-shaped bone growth stimulator that promotes bone-to-bone fusion, or bone growth, through electrical stimulation. The Whitscomb et al. application herein referred to describes the general background of bone growth stimulators. Such stimulators are simply constant current sources. One or more cathode leads from the stimulator are implanted into the bone at the site of the fracture. The case itself, made primarily of titanium but preferably plated with titanium in at least limited areas, can serve as an anode and a separate anode lead is provided for insertion into the soft tissue. be able to.

The Hyasion et al. patent application, referenced herein, describes an improved bone growth stimulator that is not only hermetically sealed but also capable of monitoring the therapeutic current. The stimulator generates a series of pulses with a magnitude proportional to the magnitude of the current applied to the fracture site;
An external frequency counter can be used to determine the magnitude of the current.

The cathode lead of a typical conventional bone growth stimulator is made of titanium wire and is spirally wound with the free end wrapped tightly around the chuck end of a smooth mandrel, such as a drill bit.
A chunk of bone, typically 1 cm wide and 2 to 3 cm long, is removed from the fracture site and the uninsulated coiled end of the anode lead wire is implanted into the remaining bone hole. During implantation surgery, the cathode lead is often pulled, and the lead usually breaks where it exits the bone. The electrode itself cannot be removed from the previously implanted bone because the bone will grow around it.

There are several problems with this type of construction in which the lead electrodes are an integral part of the entire stimulator. Regardless of the lead wire breaking exactly where it exits the bone, many times the lead wire will break elsewhere if it remains loosely within the patient's body. Additionally, there is always the risk that the lead wire will not cut cleanly, leaving a sharp jagged end at the break site. It is highly preferred to provide a lead wire to ensure that the break always occurs at the intended location during the implantation procedure and that the break does not become undesirable.

It would be advantageous if the bone growth stimulator lead could be made such that the same force is always required to break the lead during the implantation procedure. Significant force is required to break a conventional lead, and surgeons are reluctant to pull on implanted leads with such great force. Also, repeatability in surgical procedures is desirable, and for this reason it is highly desirable to have a lead whose breaking force is always substantially the same. Conventional titanium wire lead wires exhibit different breaking strengths based on the different compositions of the strands and the different heat treatment processes for each strand, especially when the lead wire is made of titanium strands. It is known that different forces are required to break.

Traditional lead wires are usually made of titanium, as titanium is the most hospitable metal for the human body. However, titanium is not the best metal for lead wires considering other considerations. Stainless steel is contemplated for its sufficient strength and great durability, especially if the lead is subject to continuous bending, such as when the electrodes are on the fingers or the stimulator is on the forearm. However, traditional leads are not made of stainless steel because the electrodes must remain in the bone or body after the implantation procedure, and titanium is much better in this regard. Conventionally, there is no means to achieve the advantages of the strength and cheapness of stainless steel and the coexistence of titanium.

Bone growth stimulators are expected to do their job for several months, but are always unsuccessful. In such cases, stimulation must be continued. But the battery is 20
Because it applies a relatively large constant direct current of microamperes, the battery that powers the stimulator has a lifespan of several months. Continuous stimulation in the prior art requires not only a new implant but also the attachment of new electrodes to the bone. This is based on the fact that the leads/electrodes form an integral part of the entire stimulator.

It is known to prepare a large number of prefabricated electrodes. Based on the specific fractures included,
The dimensions of the electrode helix can be varied. It is also possible that electrodes of different materials may be required by the surgeon, as is preferred for the use of silver electrodes, as shown, for example, in the Hiersion et al. patent. If hospitals started stocking a complete set of bone growth stimulators with integrated leads/electrodes, they would have many different types of bone growth stimulators to suit any contingency. This stimulator has everything it can do.
This increases the investment considerably, especially as a large number of stimulators of each type must be available.

The general object of the present invention is to provide a bone growth stimulator and lead wire/lead that overcomes all of the prior art drawbacks mentioned above.
The purpose is to provide electrodes.

All of the conventional drawbacks mentioned above are overcome by providing a two-part lead/electrode.
Most of the leads are conventionally an integral part of the stimulator. Instead of the ends of this lead being used as electrodes, the ends of this lead terminate in part of the connector. Other compatible parts of the connector are attached to the electrodes themselves.

Hospitals now only need to stock one type of bone growth stimulator, a Billet-type bone growth stimulator with connector-end leads. To accommodate different electrode materials and shapes, hospitals only need to stock the inexpensive connector-end electrodes themselves. Prior to implantation, the surgeon selects the electrodes and the plug within the stimulator. Thereafter, the transplant surgery is the same as in the past.

When it is time to implant the stimulator, the surgeon pulls on the lead wire. The wire consisting of the lead wire and electrode is 6.8Kg (15 lbs) which is greater than the separation force.
Since it has such a tensile force, the breakage is always at the connector. The same force, approximately 1.4 to 2.7 kg (3 to 6 pounds), is always required to dislodge the stimulator from the electrodes remaining in the bone. With this stimulator the wires are never jagged and breaks always leave the body with a known length of electrode lead, which is very short and the connector is attached to the bone. remains nearby.

If necessary, replacing the stimulator is now a simple matter. Instead of performing another implantation surgery, all that is required is to replace the stimulator itself and connect new leads to connectors that remain at the ends of the electrodes already in the bone. Similarly, the use of connectors allows the stimulator leads to be made of stainless steel and the electrodes to be made of conventional titanium or other desired materials.

There are many different types of connectors used in electronic technology, and standard types of connectors can be considered to meet the above objectives. However, this was not known until now. Experience has shown that many connector types are inadequate. For example, the simplest connector is a male-female mating type. In such connectors, a male circular pin is pushed into a female circular hole. This type of mating connector is known to have tight tolerances and high manufacturing costs in order to provide reproducible removal forces. Other types of connectors have been considered, but with little success. The tripping force is required to be relatively constant and independent of the tripping speed, i.e., the same tensile resistance is exerted when the lead is pulled slowly or quickly out of the body; Consideration must be given to the fact that upon disconnection, the connector is unalteredly immersed in water in a humid body environment, and that mating connectors have been found to be unsuitable.

Although other types of connectors may be operable, only one type has been found to have satisfactory implementation. The male part of the connector consists of circular pins. However, the female portion of the connector, herein referred to as a split female, consists of a sleeve with a diametrical slit along its length. Connection is not simply accomplished by fitting a pin into a socket. Rather, the two halves of the female socket, separated by the slit, act to bend the beam and clamp the pin between the beams. Separation forces that vary by several pounds at different degrees of water immersion can be easily achieved without the very tight tolerances required. The separation force is
Even if the male and female connectors are pushed and pulled together dozens of times, they can be regenerated. Matching combinations are not absolutely necessary. The male connector of the electrode can cooperate with the female connector attached to the stimulator, provided that certain tolerances remain, as discussed below. The male and female connectors can be reversed for any type of stimulator if desired.

Other objects, features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.

The bone growth stimulator 10 of FIG. 1 is provided with an integral lead assembly 12 and female connector 14. The stimulator itself is preferably of the type described in the Hiersion patent specification. Pre-made electrode 1
8 is connected to the male connector 16 by a wire 36 made of the same material. Before implantation, special electrodes are selected and connected to the stimulator. FIG. 2 shows another electrode 18' connected to male connector 18' by wire 36'. This special electrode is suitable for use in the knee joint. Of course, the invention is not limited to prefabricated electrodes; the surgeon can make the electrodes himself from wire with a preattached connector.

A portion of the female connector 14 is shown in FIG. 4, and an example of its dimensions will be described later, but the overall shape is clear at this stage. The left hand end of connector member 26 of female connector 14 is provided with an integral hole 26a for insertion of stimulator lead 20 (FIG. 3). The right hand end of the connector member 26 also has a circular hole with a diametrical slit 26c extending longitudinally along the sleeve portion. Slit 26c creates two semicircular beams 26d, 26e into which pins 30a of male connector 16 mate.

Connector member 30 of male connector 16 is shown in FIG. 5 and has two main sections. The left-hand pin 30a fits into the socket of the female connector 14, and the right-hand hole 30b of the connector member 30 has an electrode wire 36 (FIG. 3) inserted therein. Reference is now made to FIG. 3, which shows the general structure of the connector, and the dimensions of FIGS. 4 and 5 will be explained later.

In a preferred embodiment of this invention, lead wire 20
For example, 0.4 commercially available from American Cyanimitsu
Made from mm diameter multi-stranded stainless steel suture wire. The free end of the lead wire 20 is connected to the female connector 14
The connector member 26 is then swaged at 90° intervals around the periphery, as shown at 28, to secure the leads 20 to the connector member 26. The size of each upsetting part is approximately 1
×1 mm. The upsetting strength is greater than the tensile strength of the connector member, so it is better for the two parts of the connector member to be separated during implantation surgery than for the lead wire or the connector member. Therefore, the lead wire 20
After being attached to connector member 26, Dow Corning medical grade tubing 22 is placed over lead wire 20 and connector member 26, and tube 22 is placed over lead wire 20 and connector member 26.
The right-hand end of connector member 2 extends to the right-hand end of connector member 26 . Dow Corning Medical Silastack adhesive 24 is injected into the left hand end of tube 22 and fills the gap between lead wire 20 and tube 22. The left hand end of the lead 20 is attached to a stimulator such as that shown in the Hiasion et al. patent, and the Shirastack tube 22 is adhered to the Shirastack top cover by Shirastack adhesive. It will be appreciated that the full length of lead 20 is not shown in the drawings. Lead wire 20 is actually approximately 160 mm long.

Silastack materials are human-compatible and can be used to bond other Silastack materials and metal wires.

The electrode wire 36 consists of three strands of heat-treated titanium wire and has an overall diameter of 0.55 mm.
The end of the wire 36 is inserted into the hole 30b of the connector member 30 of the male connector 16, and the end of the wire 36 is inserted into the hole 30b of the connector member 30 of the male connector 16.
is upholstered at four locations as shown by numeral 32,
The upsetting strength is greater than the tensile strength of the connector.
A short shira stick sleeve 38 connects the wire 36.
is placed over the hole 30b and inserted into most of the hole 30b. Sleeve 38 is flexible to reduce sharp bends in wire 36 where wire 36 exits connector member 30. The shirastaik tube 42 is then placed over the connector member 30 and sleeve 38 as shown. In the final manufacturing process, the adhesive 40 of the Shirastick is applied to the wire 3.
6 and sleeve 38 to form a smooth strip on the end of male connector 16 and to bond sleeve 42 to sleeve 38.

It should be noted that the swaging in each part of the connector member is not close to the exit location of the wires being connected. The upsetting position is not arbitrary. The weakest point of each wire is at the upsetting section. If a crack is created in the wire due to upsetting, it is preferable to prevent bending of the wire near the crack. Since wires near each swaging location cannot be bent, the risk of breakage is reduced. The upsetting force itself should be kept to a minimum to reduce the rate of wire cracking. Upsetting is due to the holding force exceeding the separation force, but only by a few pounds at most.
In the preferred embodiment of this invention, the separation force is 1.4-2.7Kg
(3 to 6 pounds). However, in general, the invention contemplates separation forces in the range of 3 to 20 pounds. It may be said that for special types of connectors the separation force may range beyond this wide range. On the other hand, the separation force is only about 2.7Kg (6
(pounds) or within the range of a given type. For special kinds, separation force is 1.4~4.1Kg
(3 to 9 pounds), 4.5 to 7.2 Kg (10 to 16 pounds), etc. In particular, no advantage is gained by requiring separation forces in excess of 2.7 Kg (6 lbs).

When the two connector members 26, 30 are brought into abutment against each other near the tubes 22, 42 of the shirastaik, bodily fluids can flow into the connectors. There is no practical means to prevent this. The shield insulation is provided to minimize exposed portions of the connector so that leakage currents are kept to a minimum and water can enter the connector. However, the important thing is that the presence of water does not substantially affect the separation force.

In installing the connector, it is noted that the only exposed surfaces are the silica tube and the titanium electrode wires. Because Shilastake and titanium are body-compatible materials, Shilastake and titanium prevent excessive fibrous encapsulation that would otherwise prevent separation of the two parts of the connector.

connector members 26 for female and male connectors;
30 is shown enlarged in FIGS. Each connector member is made of commercially available pure titanium without heat treatment. In the preferred embodiment of the invention, the connector member is manufactured by IMI, commercially available from Imperial Metal Industries Limited, Birmingham, UK.
Constructed from grade 130 3mm or 4mm cold drawn titanium rod. There are only two limited dimensions for male connector members and three limited dimensions for female connector members.

Two limited dimensions of male connector member 30 are shown in FIG. The holding force is determined by the two lever parts 26d on the right side of the female connector member 26,
26e is determined by the bend. The degree of bending is determined by the inner diameter of the hole 26b of the female connector member 26 and the outer diameter of the pin 30a of the male connector member 30. The outer diameter of the pin 30a is limited. This is one of the dimensions. Further, the length of the pin 30a is limited as shown. The two connector members 26, 30 are fully pressed into each other, and the left end of the pin 30a has a diameter portion before being tapered such that the two lever portions 26d, 26e of the connector member 26 of the female connector 14 are separated. substantially compressed and bent. Accordingly, the degree of bending is related to the length and outer diameter of pin 30a of male connector member 30, two limited dimensions being shown in FIG.

The limited dimension of the female connector member 26 is the hole 2.
6b, the length of the hole 26b, and the width of the slit 26c. The force for bending the two lever parts 26e and 26d is due to the outer diameter of the pin 30a and the lever parts 26e and 26d.
The internal diameter of the hole 26b in conjunction with the length of the hole 26b and the width of the slit 26e determine the mechanical advantage of the hole 26d. The limited width of slit 26e is shown approximately 2.5 mm from the right end of female connector member 26. This dimension itself is not limited. The slit 26c has a constant width over the entire length and does not change.
For testing purposes, the slit width is measured approximately 2.5 mm from the end of the connector member 26.

In the illustrated embodiment of the invention, the tensile separation force of the connector is determined by the force exerted on the ends of the male pins by the deformation of the two semi-cylindrical beams of the female connector. The tolerances are relatively easy to achieve, with only five limited tolerances in the first location. A series of connectors made in this way can maintain a 1.4
Provide a tensile force of ~2.7 Kg (3-6 lbs).

A female connector split into four sections is considered preferable because it moves less in response to lateral forces than only two. The symmetry of the diametrically split members allows for the creation of a connector that is insensitive to bending moments. However, this has been found to be insufficient, increasing machining time and therefore cost, and not helping the efficiency of the design. For this reason, a single slit is preferred for female connectors.

Although this invention has been described with reference to specific embodiments,
It should be understood that this example merely illustrates the use of the principles of the invention. Various changes and modifications can be made without departing from the spirit and scope of the invention.

[Brief explanation of drawings]

FIG. 1 is a general view of the stimulator, connector, and electrode combination when used in accordance with the principles of the invention;
Figure 2 shows different electrodes and shows how the same stimulator can be used with many different electrodes of the same type based on the use of connectors; Figure 3 shows that the female connector is connected to the stimulator lead. FIG. 4 is an enlarged view of the connector member of the female connector, and FIG. 5 is an enlarged view of the connector member of the male connector. In the figure, 14: female connector, 16,
16': Male connector, 18, 18': Electrode, 2
0: Lead wire, 26: Connector member, 26a, 2
6b: hole, 26c: slit, 26d, 26e:
lever part, 30: connector member, 30a: pin,
30b: hole, 36, 36': wire, 38: sleeve, 42: tube.

Claims (1)

Claims: 1. An implantable power supply comprising: an implantable power source; an integrally connected lead wire terminating in a first connector member; and an electrode terminating in a second connector member;
and a second connector member, one having a male pin and the other a female sleeve having a diameter slit along its length, both connectors being coupled to each other during the implantation procedure. a bone growth stimulator, wherein the connector member is covered with a biocompatible plastic except at the end of the sleeve and around the pin. 2. The bone growth stimulator according to claim 1, wherein the connector member has a separation force of 9 kg (20 pounds) or less. 3 Separation force of connector parts is 2.7Kg (6 pounds)
A bone growth stimulator according to claim 1 as follows. 4. The bone growth stimulator according to claim 1, wherein the lead wire and the electrode are made of different metals. 5 an implantable power source, an integrally connected lead wire terminating in a first connector member, and an electrode terminating in a second connector member;
and a second connector member, one having a male pin and the other a female sleeve having a diameter slit along its length, both connectors being coupled to each other during the implantation procedure. are separated, the connector members are covered with biocompatible plastic except at the ends of the sleeves and around the pins, and the connector members have a separation force of 3 to 20 pounds (1.4 to 9 kg). ) and less than the strength of said leads and electrodes.