Can Implanon Migrate Into the Triceps Muscle?
Yes, Implanon/Nexplanon implants can migrate into muscle tissue, including the triceps, though this is a rare complication that typically results from improper insertion technique.
Understanding Implant Migration
While the available guidelines focus on proper insertion technique rather than specific migration patterns, the research evidence clearly documents cases of implant migration into muscle tissue. The implant is designed to be inserted subdermally in the groove between the biceps and triceps muscles of the upper arm 1, 2, 1, 2, 1, 3. However, when insertion is too deep or improper, migration can occur.
Documented Migration Cases
The literature confirms muscle migration is possible:
- Multiple case reports document implants migrating into the biceps muscle specifically 4, 5, 6
- One recent case (2025) reported migration into the pectoralis muscle 7
- Another case documented an implant adherent to the ulnar nerve requiring fluoroscopy-guided removal 8
While these reports specifically mention biceps and pectoralis muscles rather than triceps, the anatomical proximity and mechanism of migration suggest triceps involvement is theoretically possible, particularly given that the insertion site is in the groove between these two muscle groups.
Why Migration Occurs
Three conditions must be present for implant migration 9:
- Lack of proper tissue integration
- Improper insertion depth (too deep, subfascial, or intramuscular)
- A force pushing the implant from its original location
The most common cause is insertion technique error - the implant being placed too deeply at the time of insertion rather than true migration after proper placement 10.
Clinical Implications and Management
When an implant becomes non-palpable:
- Immediate imaging is essential to prevent further neurovascular injury 6
- High-resolution ultrasound (10-15 MHz linear array transducer) is the first-line imaging modality 11
- If ultrasound fails to locate the implant, MRI is typically the next best choice 11
- Nexplanon contains barium sulfate making it visible on X-ray and fluoroscopy, unlike original Implanon 1
Removal considerations:
- Deeply placed or intramuscular implants may require specialist referral 5
- Ultrasound-guided or fluoroscopy-guided removal by interventional radiologists or peripheral nerve surgeons may be necessary 4, 8
- General anesthesia and wide exposure may be required for safe removal when the implant is adherent to nerves or deep in muscle 5
Prevention Through Proper Technique
The key to preventing migration is correct insertion 1, 2, 1, 2, 1:
- Insert subdermally (not intramuscularly) in the inner aspect of the non-dominant upper arm
- Place 6-8 cm above the elbow in the groove between biceps and triceps
- Ensure the implant is palpable immediately after insertion
- Only trained clinicians should perform insertions
Critical pitfall: In France, 77% of reported pregnancies with Implanon were due to insertion errors where the implant was never actually inserted 10. This underscores the importance of confirming palpability post-insertion and proper training.