Written by Ellen Stoke, MD

In the United States, the contraceptive implant is a single, soft, flexible progestin rod that is inserted subdermally in the upper arm. Globally, two-rod systems are also available and some patients still have a discontinued six-rod system in place. All contraceptive implants should be placed superficially, but occasionally patients and clinicians are unable to palpate them making removal difficult.

About 14/1,000 device removals are reported as difficult, and 1/1,000 people have a nonpalpable device at the time of removal.¹ If unable to be palpated, the device should be located on imaging before removal is attempted. In some instances, a referral to a specialized center may be required.^2-5 Clinicians are encouraged to call the phone number listed in the implant prescribing information when they need assistance with a difficult or nonpalpable implant removal. The manufacturing company can provide the clinician with a nearby referral center to assist.^1,6

When a patient presents with a nonpalpable implant:

1. Rule out pregnancy and consider providing counseling on back-up contraception until the location of the implant is confirmed.
2. Obtain a history on the type of implant and where it was placed. If placed outside of the United States, consider that the implant may be a multi-rod system (See Contraceptive Pearl). Sometimes patients will not recall which arm it was placed in, so a physical exam looking for an insertion site scar may be helpful.
3. Use imaging to identify implant location.

If imaging is unable to locate the implant, then obtain an etonogestrel (ENG) level.^7-8 A negative serum ENG level verifies the absence of the implant by indicating undetectable levels of the active component of the implant (ENG). However, this detection method can only be employed with ENG implants (Nexplanon, Implanon NXT).

Authors Soler-Perromat et al. have proposed an algorithm for the localization of contraceptive implants (Figure 1).

Figure 1. Soler-Perromat et al. Algorithm for the localization of contraceptive implants. US, ultrasound; MRI, magnetic resonance imaging; ENG, etonogestrel; CT, computed tomography.⁸

Consider the following imaging modalities for non-palpable implants:

1. Ultrasound: If available, start with a bedside ultrasound^9-10 using a high-frequency linear array transducer (9-18 MHz or higher). Perform the ultrasound with the patient’s arm in 90° abduction and external rotation.¹¹ If the device is located: determine the depth of the implant, if the implant appears to be supra- or intramuscular, and if there are adjacent vascular structures. If unable to visualize on bedside ultrasound consider ordering a formal ultrasound of the suspected arm (or both arms if the patient is unsure).*
2. X-Ray: If ultrasound is unavailable or X-ray is more readily available then order an anteroposterior view of the upper suspected arm (or both arms if the patient is unsure of location). The implant will appear as one (or two or six, depending on the implant) radio-opaque bands. However, some implants, like Jadelle and Sino-Implant II, are not radiopaque and cannot be identified on X-ray. On rare occasions, the X-ray may show axillary migration of the implant.*
3. Magnetic Resonance Imaging (MRI): MRI can be a secondary imaging method if the implant has migrated out of the arm, is radiolucent, or is positioned deep within the muscle where the implant can be difficult to detect even with the use of ultrasound or X-ray.^7-8,11*
4. CT Imaging: CT imaging is generally avoided due to its ionizing radiation exposure and it is only able to detect radio-opaque implants. The primary utility of CT in locating non-palpable implants is in the extremely rare case of pulmonary embolism due to vessel implant migration from arm veins to pulmonary arteries.

*See Soler-Perromat et al. (2024) for examples of implants on US (Figure 1-2), X-ray (Figure 3-4), and MRI (Figure 5-6).

Sources:

1. Mastey N, Matulich MC, Uhm S, et al. US referral center experience removing nonpalpable and difficult contraceptive implants with in-office ultrasonography: A case series. Contraception. 2021;103(6):428-430. doi:10.1016/j.contraception.2021.01.018

2. Mommers E, Blum GF, Gent TG, Peters KP, Sørdal TS, Marintcheva-Petrova M. Nexplanon, a radiopaque etonogestrel implant in combination with a next-generation applicator: 3-year results of a noncomparative multicenter trial. Am J Obstet Gynecol. 2012;207(5):388.e1-388.e3886. doi:10.1016/j.ajog.2012.08.002

3. Pillai M, Gazet AC, Griffiths M. Continuing need for and provision of a service for non-standard implant removal. J Fam Plann Reprod Health Care. 2014;40(2):126-132. doi:10.1136/jfprhc-2013-100619

4. Shulman LP, Gabriel H. Management and localization strategies for the nonpalpable Implanon rod. Contraception. 2006;73(4):325-330. doi:10.1016/j.contraception.2005.10.009

5. Mansour D, Walling M, Glenn D, et al. Removal of non-palpable etonogestrel implants. J Fam Plann Reprod Health Care. 2008;34(2):89-91.

6. Matulich MC, Chen MJ, Schimmoeller NR, et al. Referral Center Experience With Nonpalpable Contraceptive Implant Removals. Obstet Gynecol. 2019;134(4):801-806. doi:10.1097/AOG.0000000000003457

7. Stillwell S, Sheppard P, Searle S. The impalpable Implanon: a case report. J Fam Plann Reprod Health Care. 2003;29(3):156-157. doi:10.1783/147118903101197566

8. Soler-Perromat JC, Bartolomé-Solanas Á, Del Amo M, et al. Non-palpable contraceptive implants localization: review of imaging techniques and algorithm proposal. Quant Imaging Med Surg. 2024;14(11):7862-7871. doi:10.21037/qims-24-353

9. Westerway SC, Picker R, Christie J. Implanon implant detection with ultrasound and magnetic resonance imaging. Aust N Z J Obstet Gynaecol. 2003;43(5):346-350. doi:10.1046/j.0004-8666.2003.00103.x

10. Biskamp C, Kauffman RP. Arm flexion during ultrasound assists localization of an intramuscular etonogestrel contraceptive implant. Contraception. 2016;93(3):273-275. doi:10.1016/j.contraception.2015.11.004

11. Merki-Feld GS, Brekenfeld C, Migge B, Keller PJ. Nonpalpable ultrasonographically not detectable Implanon rods can be localized by magnetic resonance imaging. Contraception. 2001;63(6):325-328. doi:10.1016/s0010-7824(01)00209-8

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