Can the Implant Move in Your Arm?

Contraceptive implants like Nexplanon can shift position in your arm after insertion, and in rare cases they migrate far enough to cause problems. Most of the time, any movement is minor, just a centimeter or two within the soft tissue where it was placed. But the more dramatic scenarios, where an implant travels deep into muscle or even enters a blood vessel, do happen and are worth understanding if you have one or are considering getting one.

What Counts as Normal Movement

The implant is a thin, flexible rod about the size of a matchstick, and it sits in the subdermal tissue of your upper arm. You should be able to feel it under the skin by pressing lightly with your fingers. Small shifts within that tissue layer are common and typically harmless. The rod might settle a bit after insertion as your body adjusts, but it generally stays where the clinician placed it. A large observational study tracking over 7,300 insertions found that no implants were located outside the arm, and the vast majority stayed in their expected position through the full duration of use.¹

The concern is not really about the implant drifting half a centimeter to the left. It is about the implant moving deep enough that you can no longer feel it, or entering tissue layers or structures it was never meant to be near. That kind of movement is what clinicians call “migration,” and it is a different category of event from ordinary settling.

Why the Insertion Site Matters So Much

The implant goes into the inner side of your non-dominant upper arm, about 8 to 10 centimeters above the bony bump at the inside of your elbow. That specific spot was chosen because it sits away from any major blood vessels or nerves.² An anatomical study of this area confirmed that no major neurovascular structures sit directly over the recommended placement zone, and that bending the elbow during insertion actually pushes the ulnar nerve farther from the site, adding another layer of safety.³

When insertion goes exactly right, the rod sits just beneath the skin in a quiet pocket of tissue where there is not much to disturb it. When things go wrong, it is usually because the rod was placed too deep. A deep insertion means the rod ends up below the fascia, the tough sheet of connective tissue that separates the superficial fat from the muscle underneath. Once it is beneath that barrier, the implant has access to structures like veins, nerves, and muscle compartments that it was never designed to interact with.

How Often Does Significant Migration Happen

The most alarming form of migration is when the implant enters a vein and travels through the bloodstream to the lungs. This is genuinely rare. A nationwide French study calculated the incidence of implants migrating into the pulmonary vasculature at roughly 1 to 3 per 100,000 implants sold, depending on the year.⁴ To put that in perspective, if a million people had implants, somewhere between 10 and 30 would experience this complication. Case reports describe implants being found in branches of the pulmonary artery after a patient noticed they could no longer feel the rod in their arm.⁵

More commonly than vascular migration, implants simply end up deeper in the arm tissue than intended. The same large observational study mentioned earlier found that incorrect insertions, including deep insertions and partial insertions, occurred at a rate of about 13 per 1,000 procedures.¹ That is a meaningful fraction, about 1 in 80 insertions. Not all of these deep placements lead to migration, but they do increase the risk of complications down the line.

What Causes Migration

The mechanism behind vascular migration is straightforward in concept. If the implant is accidentally placed into or near a vein during insertion, the rod can enter the venous system. From there, blood flow carries it through progressively larger veins, through the right side of the heart, and into the pulmonary arteries.⁶ This path is the same route any object in the arm’s venous system would take. It is not that the implant “breaks free” months later; the initial placement into or too near a vessel is the triggering event, though sometimes the implant sits near a vessel wall and gradually erodes into it over time.

For non-vascular migration, where the implant shifts deeper into the arm rather than entering a blood vessel, several risk factors have been identified. A retrospective analysis found that lower body mass index at the time of insertion, greater weight gain during use, and longer duration of implant use were all independently associated with the implant ending up in a deep position at removal.⁷ The same study found that insertion by a non-physician or non-OB/GYN was associated with higher rates of deep removal, suggesting that clinician experience and training matter. A 2024 systematic review corroborated that inadequate insertion technique and being normal weight or underweight appear to raise migration risk.⁸

The BMI connection might seem counterintuitive at first. You might expect larger arms to have more room for the implant to move. But the subdermal fat layer in people with lower BMIs is thinner, which means there is less cushioning between the skin surface and the deeper tissue planes. A clinician inserting the implant at the standard depth is more likely to overshoot into the fascial or muscular layer when there is less tissue to work with. The weight gain finding also makes sense mechanically: as the arm’s tissue composition changes over three years, the implant’s position relative to surrounding structures can shift.

What Does Migration Feel Like

In many cases, you will not feel migration as it happens. The most reliable signal is that the implant becomes non-palpable, meaning you can no longer feel the rod when you press on your arm where it was placed. Some people notice this at a routine check; others discover it when they try to confirm the implant is still there. The current recommendation is to check periodically by feeling for the rod, and if you cannot find it, contact your provider.

When the implant migrates into or presses against a nerve, symptoms are more obvious. Case reports describe tingling, numbness, or pins-and-needles sensations running from the inner elbow down to the fourth and fifth fingers, following the path of the ulnar nerve.⁹ In one case, a woman presented with ulnar neuropathy three years after insertion; imaging showed the implant had migrated proximally and deep, and it was found lying directly on the ulnar nerve during surgical exploration.¹⁰ Her neurological symptoms resolved after the implant was surgically removed.

In the observational study data, pins and needles or numbness in the arm, hand, or fingers was the most commonly reported patient event after insertion.¹ Not every case of tingling means the implant has migrated; some transient nerve irritation can happen from the insertion procedure itself. But persistent or worsening nerve symptoms in the arm where your implant sits should prompt a visit to your provider.

How a Migrated Implant Is Found

If you cannot feel your implant, the first step is imaging. Ultrasound is the preferred first-line tool because it is quick, cheap, and accurate for finding implants in the soft tissue of the arm.¹¹ The current version of the implant, Nexplanon, is radiopaque, meaning it shows up on plain X-rays. This was a deliberate design upgrade from its predecessor, Implanon, which was not visible on X-ray and could be much harder to locate if it moved.⁵ If ultrasound does not locate the implant in the arm, X-ray or CT imaging can search a wider area, including the chest, which is where vascular migration would deposit the rod.

The imaging algorithm is generally stepwise. Clinicians start with ultrasound of the arm. If the implant is not there, a chest X-ray or CT scan is the next move. In the rare cases where the implant has traveled to the pulmonary artery, CT has been the tool that pinpoints its location in a specific branch of the lung’s vasculature.

Removing an Implant That Has Moved

When the implant has shifted deeper in the arm but is still in the arm tissue, removal is usually possible with an ultrasound-guided procedure. One described technique involves positioning the arm in abduction and rotation, using local anesthesia, and then performing hydrodissection, which means injecting saline around the implant to free it from any tissue adhesions. A small scalpel creates a path under ultrasound guidance, and surgical forceps are used to grasp and extract the rod.¹² This is more involved than a standard removal, which typically takes just a few minutes with a small incision, but it is still a minimally invasive procedure that can be done with local anesthesia.

Sometimes a deeply placed implant requires fluoroscopic guidance or even an orthopedic surgeon’s involvement, particularly when the rod is embedded in muscle tissue or near a nerve. Case reports describe implants found within the biceps muscle itself, requiring surgical exploration to remove.¹³ These cases underscore why “blind” removal attempts, where the clinician tries to extract a non-palpable implant without imaging guidance, can cause additional harm.

For the most extreme cases where the implant has reached the pulmonary artery, retrieval typically involves endovascular techniques. A catheter is threaded through a vein and guided to the implant’s location in the lung vasculature. This approach has a high success rate and carries less risk than open surgery, though complications like vessel injury are possible.¹⁴ If catheter retrieval fails, thoracoscopic surgery may be needed.

When Removal Itself Causes Nerve Damage

One underappreciated risk is not from the implant migrating on its own but from the removal procedure when a deep implant is extracted improperly. A case report describes a 21-year-old woman who developed ulnar nerve palsy after an attempted in-office removal of a deeply implanted Nexplanon. The injury was severe enough to require surgical exploration, excision of a neuroma that had formed, and nerve cable grafting.¹⁵ This is an extreme outcome, but it highlights a point that matters for anyone in this situation: if your implant has moved and is no longer palpable, the removal should be done by someone with the right imaging equipment and surgical skill, not attempted blind in a standard clinic visit.

Risk factors for nerve injury during removal mirror the risk factors for deep placement itself. Being underweight and having a device that has migrated are both flagged in the literature as increasing the likelihood of ulnar nerve complications.¹⁶ The good news is that in most reported cases where the implant was pressing on a nerve, symptoms resolved once it was properly removed.

Practical Steps If You Have an Implant

The single most useful habit is periodically checking that you can still feel the rod under your skin. There is no official recommended frequency, but running your fingers over the insertion site every few weeks takes seconds and is the earliest possible alert system. If you can feel it, it has not migrated in any meaningful way. If you suddenly cannot feel it when you previously could, that warrants a call to your provider.

If your provider cannot locate the implant on palpation, imaging should be the immediate next step. The implant should not be assumed to have fallen out or never been inserted. A non-palpable implant needs to be found and accounted for because it may still be releasing hormones and providing contraception, or it may be in a location where it could cause harm. You should use a backup contraceptive method until the implant is located and its status is confirmed.

When discussing removal of a non-palpable implant, ask about the plan for imaging guidance. Ultrasound-guided removal is the current standard for deep implants. If your provider does not have this capability in-office, they should refer you to someone who does. The evidence is clear that blind removal attempts carry unnecessary risk of nerve injury and incomplete removal.

How Implant Design Has Changed

The shift from Implanon to Nexplanon was partly driven by the need to address insertion errors and improve localization of migrated devices. The earlier Implanon applicator had a design that contributed to non-insertions and deep insertions; a risk-management analysis of the applicator identified specific steps in the insertion process that were prone to user error and recommended design changes.¹⁷ Nexplanon introduced a redesigned applicator intended to reduce these errors, along with the barium sulfate core that makes the implant visible on X-ray and CT.

The radiopacity change was arguably more important than the applicator redesign. When Implanon migrated, finding it could be a genuine ordeal because it did not show up on standard imaging. The ability to locate Nexplanon quickly with a simple X-ray has made the management of migration cases substantially easier and has likely prevented some of the more prolonged diagnostic searches that occurred with the older device.

The Duration-of-Use Question

One finding from the literature that deserves attention is the association between longer duration of use and deeper implant position at removal. In the retrospective analysis, each additional month of use slightly increased the odds of the implant being in a deep position.⁷ The implant is approved for up to three years (recently extended to five years in some regions for contraceptive efficacy), and many people who experience difficult removals have had the implant for the full duration or beyond. Whether the implant slowly migrates deeper over time through tissue remodeling, or whether the body gradually encapsulates the rod in a way that makes it feel deeper at removal, is not entirely clear. But from a practical standpoint, keeping the implant beyond its approved duration appears to increase the chances that removal will be more complicated than expected.

The association between implant exchange and deep removal was also notable in that same study. People on their second or third consecutive implant had higher rates of deep placement. This could reflect scar tissue from the previous removal site, altered tissue planes, or simply the cumulative years of having a foreign body in the same area of the arm. If you are getting a replacement implant, it is worth discussing placement strategy with your provider, particularly whether the new implant should go in the same site or a different location on the arm.