The contraceptive implant, often referred to by its brand name, Nexplanon, is a highly effective, long-acting reversible contraceptive method. This method involves the subdermal insertion of a small, flexible rod about the size of a matchstick, which continuously releases a progestin hormone to prevent pregnancy. The implant is typically placed just under the skin on the inner side of the non-dominant upper arm, providing continuous contraception for up to three years. Knowing its normal position and how to monitor it remains an important part of using this method.
Normal Position and The Importance of Self-Checking
The implant is correctly situated in the upper arm, a specific distance above the elbow and away from the major blood vessels and nerves. Once inserted, it lies superficially, just beneath the skin, over the triceps muscle. You should be able to feel the implant easily with your fingertips, and it will have a distinct, rigid, rod-like feel.
A healthcare provider should confirm the implant’s presence by palpation immediately after insertion, and you should be shown how to feel it yourself. Establishing this baseline sensation is important because you should perform a gentle self-check once a month. This routine involves lightly running your fingers over the insertion area to confirm the entire four-centimeter length of the rod is still present. Regular self-checking ensures the device remains in its proper location. The continued presence and correct placement of the implant help ensure that removal will be a straightforward procedure.
Identifying Physical Signs of Implant Movement
The most immediate sign that an implant may have moved is a change in the tactile sensation during your self-check. Instead of feeling the full, smooth rod, you might only be able to feel one end of the device, or you may not be able to feel it at all at the original insertion site. Even minor displacement can make the implant non-palpable, especially if it has moved deeper into the tissue.
Visual changes can also suggest displacement. Migration can sometimes cause the device to appear visible beneath the skin, or create a slight bulge in an unexpected location away from the insertion scar. Localized symptoms near the insertion site or traveling down the arm can sometimes signal an issue with placement.
Persistent, localized pain, unusual tingling, or numbness (paresthesia) may suggest the implant is irritating a nearby nerve. In rare cases, if the implant has migrated into a blood vessel, systemic symptoms may occur, such as unexpected chest pain, coughing, or difficulty breathing.
Potential Consequences of Displacement
For most users, a slight shift in the implant’s position does not affect its ability to deliver the hormone and prevent pregnancy. The device’s efficacy is dependent on the continuous release of etonogestrel into the body, which typically continues even if the rod has moved slightly. However, any movement that makes the implant difficult to locate can complicate the eventual removal process.
The primary concern with displacement is the potential for difficult removal, which can occur if the implant has migrated more than two centimeters from the insertion site or moved deeper than the subdermal layer. Deeply inserted or migrated implants may become encased in muscle or connective tissue, making the standard outpatient removal procedure challenging. In such instances, a provider must use specialized techniques.
In rare cases, the implant can migrate into the vascular system, potentially traveling to the pulmonary arteries in the chest. This distant migration makes removal significantly more complex, requiring advanced medical imaging and surgical expertise.
When to Seek Medical Attention and What to Expect
You should contact your healthcare provider immediately if your monthly self-check reveals you cannot feel the implant at all, or if you feel only one end of the rod. Immediate professional attention is also warranted if you experience persistent, unexplained pain, swelling, or numbness in your arm, or if you develop any signs of a serious problem, such as chest pain or shortness of breath. You should never attempt to push the implant back into place yourself.
Your healthcare provider will first perform a physical examination to try and locate the device through palpation. If they cannot feel it, they will typically order imaging tests to confirm its presence and exact location. A high-frequency ultrasound is often the first step, as it can clearly visualize the rod in soft tissue.
If the implant is still not located, the provider may use an X-ray, as the current implant rods are radiopaque, meaning they are visible on a radiograph. In rare circumstances where the implant cannot be found in the arm, advanced imaging like a CT scan or MRI may be used, sometimes including a scan of the chest to rule out distant migration. If imaging fails to confirm the device’s presence, a blood test can measure the level of the active hormone to verify if the implant is still in the body.