Management of long-term and reversible hysteroscopic sterilization: a novel device with nickel-titanium shape memory alloy

Abstract

Background: Female sterilization is the second most commonly used method of contraception in the United States. Female sterilization can now be performed through laparoscopic, abdominal, or hysteroscopic approaches. The hysteroscopic sterilization may be a safer option than sterilization through laparoscopy or laparotomy because it avoids invading the abdominal cavity and undergoing general anaesthesia. Hysteroscopic sterilization mainly includes chemical agents and mechanical devices. Common issues related to the toxicity of the chemical agents used have raised concerns regarding this kind of contraception. The difficulty of the transcervical insertion of such mechanical devices into the fallopian tubes has increased the high incidence of device displacement or dislodgment. At present, Essure® is the only commercially available hysteroscopic sterilization device being used clinically. The system is irreversible and is not effective immediately.

Presentation of the hypothesis: Our new hysteroscopic sterility system consists of nickel-titanium (NiTi) shape memory alloy and a waterproof membrane. The NiTi alloy is covered with two coatings to avoid toxic Ni release and to prevent stimulation of epithelial tissue growth around the oviducts. Because of the shape memory effect of the NiTi alloy, the device works like an umbrella: it stays collapsed at low temperature before placement and opens by the force of shape memory activated by the body temperature after it is inserted hysteroscopically into the interstitial tubal lumen. The rim of the open device will incise into interstitial myometrium during the process of unfolding. Once the device is fixed, it blocks the tube completely. When the patient no longer wishes for sterilization, the device can be closed by perfusing liquid with low temperature into the uterine cavity, followed by prospective hysteroscopic removal. After the device removal, the fallopian tube will revert to its physiological functions.

Testing the hypothesis: Currently, experimental and clinical studies are needed to attest the safety, efficiency and reversibility of the novel sterilization device.

Implications of the hypothesis: If our hypothesis is confirmed, appropriate and reversible contraceptive can be achieved with the device we have designed, which may have significant repercussions for numerous women worldwide.

Figure 1

Illustration of the structure and working principle of the device. (A) The device before insertion into the tubal interstitial portion, like a folded umbrella which minimizes its size in diameter and subsequently facilitates the insertion of the device; (B) The device after the insertion into the interstitial portion, like an unfolded umbrella; (C) Coronal section view, the device is placed at the interstitial portion of the tube, The device is anchored in the right place and the passage through the tube is completely blocked. 1. A semi-soft hat; 2. A waterproof membrane; 3. Guild rod; 4. A small hole; 5. The supporter of the shape memory umbrella; 6. A thin circular rim to cut into the interstitial myometrium for fixation.