Nonpalpable Implant

A nonpalpable implant is one that cannot be felt under the skin of the inner upper arm at the expected site. It may be too deep, may have migrated, may have been broken, or may never have been inserted. A difficult implant is one that is palpable but hard to remove because of depth, fibrosis or position. Removal should be done only by a provider trained in the procedure. If the provider is not trained, removal must not be attempted and the patient is referred.

Why it matters. Deep implants lie close to the neurovascular bundle of the arm. Failure to locate an implant leaves the patient unprotected if the implant was never inserted, and creates surgical risk if removal is attempted blindly.

Implants in use. Etonogestrel 68 mg single rod with a 3 year duration, levonorgestrel 75 mg two-rod system with a 5 year duration, and levonorgestrel 75 mg two-rod system with a 3 year duration.

History. Date and site of insertion, who inserted it, whether the insertion was straightforward, the number of rods seen at insertion, bruising, weight change, pregnancy, symptoms in the arm.

Examination. Palpate both arms, from the insertion site along the proximal and distal tract. Check for scar, tenderness, numbness, weakness and signs of infection. Pregnancy test.

Differential diagnosis. Deep insertion, migration, fibrous encasement, fracture of a rod, expulsion, and failure to insert.

Imaging.

• High-frequency linear ultrasound (10 to 18 MHz) of the arm is the first test. Sweep from the elbow crease to the axilla.
• Plain film of the arm and chest when ultrasound does not find the rod. Etonogestrel rods are radio-opaque. Levonorgestrel rods are less reliably seen.
• Magnetic resonance imaging or computed tomography for a rod not found in the arm.

Hormone assay. Where available, an etonogestrel level shows whether an etonogestrel implant is present.

Pregnancy exclusion. Reasonably certain if no intercourse since last menses, consistent use of a reliable backup method, within 7 days of menses, or within 4 weeks postpartum. Otherwise do a pregnancy test.

Palpable implant. Remove by the usual technique if trained. If a rod is difficult to deliver, use a second incision, avoid blind probing and stop if resistance or neurological symptoms occur.

Nonpalpable implant.

1. Do not explore blindly.
2. Exclude pregnancy and give backup condoms.
3. Do ultrasound with a high-frequency probe.
4. If the rod is found and superficial, remove under ultrasound control by a trained provider.
5. If the rod is deep, near vessels or nerves, or not found, refer to a specialist centre for imaging and removal.
6. If no rod is found on imaging and the patient has no pregnancy and no etonogestrel level, proceed as if no implant was inserted and start another method.

Analgesia for removal. Lidocaine 1% (10 mg/mL) infiltrated, up to 4.5 mg/kg without adrenaline, maximum 300 mg (30 mL). Reduce in liver disease.

Contraceptive cover. Until the implant is confirmed in place and still within its duration, use condoms or another method. If unprotected sex has taken place, give levonorgestrel 1.5 mg orally as a single dose within 120 hours.

Broken rods. Remove all fragments when possible. A small fragment left behind may be left if removal carries risk, with counselling.

Follow up. Review wound after removal. Check the arm for neurological signs. Confirm contraception for the patient after removal.

Method decisions. If the implant is confirmed in place and within its duration, it continues to protect. If it is expired and not found, offer another method. Insert a new implant only after the old one is removed or the patient is counselled on risks of retention.

Referral and escalation. Refer every nonpalpable implant after a failed ultrasound, suspected deep implant near neurovascular structures, suspected migration to the chest, and patients with neurological symptoms.