This invention relates to a contraceptive device which can be used to occlude the fallopian tube for the purposes of sterilisation of a female.

The commonest method of contraception is sterilisation of the female. Various methods are currently used, mostly involving division, excision or external occlusion of the fallopian tubes and laparotomy or laparoscopy.

Hysteroscopic/vaginal methods which avoid abdominal surgery have also been tried. These include the use of pre-formed plugs of various designs which can be inserted into the tubal ostium without any fixation, or are fixed in place by spines or a perforating claw, or because they swell after insertion (or a combination of these properties). A technique based on the injection of a formed in situ silicone plug is currently undergoing testing. The tubal ostia can also be coagulated using thermal energy using a thermal coagulator, electrodiathermy or laser, blindly or under hysteroscopic vision. Finally, sclerosing chemicals can be injected into the fallopian tune or uterine

cavity, again blindly or under hysteroscopic control.

However, sterilisation at laparotomy involves major surgical trauma, leaves a relatively large external scar, and requires a general anaesthetic. Laparoscopic sterilisation can be performed under local anaesthesia (although is generally not), but still risks all the complications of laparoscopy, principally intra- abdominal trauma related to the blind insertion of needles and cannulae. Neither approach to sterilisation is suitable for out-patient treatment. Hysteroscopic/vaginal methods of tubal occlusion are suitable for out-patient treatment. However, techniques utilising pre-formed plugs were abandoned because of a high failure rate resulting from dislodgement . The formed in situ silicone plugs involve multiple applications in over 10% of patients to achieve bilateral insertion, and the inconvenience of a follow-up hysterosalpinogram X-ray to check for tubal occlusion. The same investigation is required for methods involving thermal coagulation of the proximal fallopian tube, with the additional disadvantages of a high complication rate of the procedure itself and a high pregnancy rate; as a result these techniques have largely been abandoned. The injection of irritant sclerosing agents has met with variable success, but once more several treatments may be required, a post-sterilisation hysterosalpingogram is necessary, and even if this shows bilateral tubal occlusion, tubal recanalisation can still occur.

According to the present invention there is provided a contraceptive device for occlusion of a fallopian tube of a female, the device comprising a plug which is capable of occluding a fallopian tube and has an external thread thereon such that upon insertion of the

plug into a fallopian tube and subsequent rotation therein, the plug grips the walls of the fallopian tube and resists removal from the tube without further rotation of the plug.

Preferably the thread is self-tapping.

Preferably, the plug is elongate and has a pointed or rounded end for initial insertion into the tube.

Preferably, the plug has a head on the opposite end to the pointed or rounded end which head has at least one formation such as a shoulder etc allowing torque to be applied to the plug by a driver. The driver is preferably elongate.

Preferably, the head is generally octagonal and a driver is preferably also provided having a generally octagonal socket to receive and engage the head so that torque applied to the driver is transferred to the plug. However, other shapes of head and driver socket can of course be used, eg slots or sockets in one and ridges or protrusions in the other.

The head may have an annular groove and the socket a circumferential ridge (or vice versa) which co-operate to lock the socket and head together. Alternatively or additionally the socket may comprise a clamp (eg it may have portions which are radially expansible or contractible) so as to receive the head in a tight fit. Other locking means may be provided to lock the device to the driver.

The plug and driver may be at least partially enclosed within an outer sleeve for ease of manipulation of the plug and driver in the uterus. The outer sleeve and

driver can both be laterally flexible but preferably both are fairly resistant to longitudinal compression and tension. The driver and plug can preferably move axially within the outer sleeve, and movement (eg axial movement) of the plug and driver relative to the outer sleeve can be a useful means of attaching and releasing the plug from the driver in the uterus .

Means may be provided in the outer sleeve to induce lateral bending of the outer sleeve (and of the driver therein) in response to manipulation of controls at the end of the sleeve remote from the plug. This allows manipulation of the sleeve, driver and plug in the uterus. Alternatively, or additionally, the sleeve, driver and plug can be passed through a channel in an operating hysteroscope or other such device.

The head may be provided with formations to assist gripping of the head with forceps etc.

The invention also provides a sterilisation assembly comprising a plug, driver and preferably an outer sleeve as hereinbefore defined.

While further modifications and improvements may be made without departing from the scope of this invention, the following is a description of one or more examples of the invention, with reference to the accompanying drawings.

Fig. 1 shows a side view of a contraceptive device, a sleeve and a driver, its insertion into the uterine cavity (1) and the final position of the screw-in devices in the proximal tubal ostia (15); Fig. 2 shows a side view of the Fig. 1 device;

Fig. 3 shows an alternative device; Fig. 4 shows a driver for use with the Fig. 1 device; Fig. 5 shows an outer sleeve for use with the Fig. 1 device; and Fig. 6 shows the alternative system of the Fig. 3 device with outer sleeve and driver.

Referring now to the drawings, a contraceptive device 1 has a body 5 and a head 10. The head 10 is attached to the body 5 at one end thereof, and at the other end, the body 5 has a rounded tip 5t. A collar 11 surrounds the joint between the head 10 and body 5. The body is externally threaded with a self tapping thread.

The head (as shown in view from A in Fig. 2) has a tapered octagonal shape. There is an aperture 10a through opposing flat sides of the octagonal head 10 to allow a handle or wire to be passed therethrough.

The device 1 is formed from rigid inert plastics material which preferably is radio opaque, or otherwise appears opaque on X-rays or ultrasound scanning. The overall measurements of the device 1 might, for example, be 1.5cm x 3mm x 3mm approximately, but will be sized to fit within a fallopian tube of a female to be sterilized. Clearly, where the device is to be used with a non-human female then sizings may be modified from those given above.

An alternative form of device 2 shown in Fig. 3 has a body 5, a collar 11, and a head 9. The device 2 is similar to the device 1 and all reference numerals correspond, except that the head 9 is shaped as a four side pyramid as shown in the view from A in Fig. 3, and has an aperture 9a through which a handle or a wire may

pass .

The head of the device 1 (and thus the body 5) is rotated by a driver 15 which comprises a hollow tube with an inner profiled surface to engage with the profile on the head 10 of the device 1. The distal end 15d of the driver is slotted to allow divergence of the end 15d around the head 10 of the device 1 so that the device 1 is securely held within the divergent arms of the end 15d. The driver 15 is formed of flexible plastics material and can bend laterally but is preferably resistant to torsional, compressive and tensioning forces. Exemplary measurements are 25cm by 2.8mm by 2.8mm (all measurements approximate) for a human female, although measurements may be altered for non-human subject.

An outer sheath 20 is also provided, comprising a hollow tube with thin walls resistant to torsional compressive and tensioning forces, but able to bend laterally. The outer sheath 20 is dimensioned to fit over the driver 15 and has exemplary dimensions 20cm x 3mm x 3mm (measurements approximate) . When the outer sheath 20 is slid over the driver 15 when the device 1 is held between the arms 15d of the driver 15, the outer sheath 20 can compress the arms 15d of the driver against the head 10 of the device 1, thereby locking the device in position in the driver. Sliding movement of the outer sheath 20 away from the end 15d allows divergence of the arms and release of the device 1.

All components are preferable resistant to sterilisation by any desired method, eg gamma radiation or antoclaving at 121°C for 20 minutes.

The device is located in the end 15d of the driver 15

and the outer sheath 20 is slid therealong so as to close the arms at the end 15d around the head 10 thereby holding the device 1 in place. The assembly is then introduced into the uterine cavity, optionally using a hysteroscope fitted with a suitable operating channel. Under hysteoscopic vision, the distil tip of the device 1 is directed towards the tubal opening of the fallopian tubes, and the device is screwed into the proximo fallopian tube by clockwise rotation of the driver, which can be manipulated externally of the patient. Once in place, the driver can be released from the screw in device by withdrawing the outer sheath 20 thereby allowing the arms at the end 15 to diverge and releasing the device 1 from the driver 15. The sheath 20 and driver 15 are thereafter removed from the uterus and the procedure can be repeated on the contralateral side.

For removal of the device 1 from the fallopian tubes, the end 15d of the driver 15 can be located on the head 10 of the device 1, and the sheath 20 slid therealong to clamp the end 15d around the head 10. The device 1 can thereafter be unscrewed anti-clockwise from the proxi of fallopian tube and removed from the uterine cavity.

In the event that the device 1 cannot be unscrewed using the driver 15, hysteroscopic grasping forceps can be used to pull on the handle or wire at the end of the device 1 to dislodge it from the fallopian tube.

The invention has the following advantages:

1. It is suitable for out-patient treatment without general anaesthesia (cf. sterilisation at laparotomy or laparoscopy);

2. It leaves no external scars (cf. sterilisation at laparotomy or laparoscopy) ; 3. There is minimal if any risk of intra-abdominal trauma (cf. sterilisation at laparotomy or laparoscopy) ; 4. The screw-in device is unlikely to dislodge spontaneously or to migrate (cf. earlier pre-formed plugs) ; 5. Bilateral tubal occlusion can be achieved at one application (cf. formed in situ silicone plugs, sclerosing agents); 6. Contraceptive effects is immediate (cf. formed in situ silicone plugs, sclerosing agents); 7. Follow-up hysterosalpinogram to check for tubal occlusion is not required (cf. formed in situ silicone plugs, thermal coagulation, sclerosing agents); 8. Thermal damage to surrounding tissues isobviated (cf. thermal coagulation techniques); 9. Tubal recanalisation cannot occur (cf. thermal coagulation, sclerosing agents); and 10. The techniques may prove to be easily reversible following removal of the screw-in device (cf. most other methods).

Modifications and improvements may be incorporated without departing from the scope of the invention.