Discussion
The use of contraceptive implants is increasing in Norway, with over 19 000 such implants inserted in 2016 (2). The procedure can be performed under local anaesthesia by a variety of healthcare professionals. The implants provide effective contraception for a period of three years (1). Nerve injuries are rare (3), but can be very serious, as our case histories illustrate. A systematic review identified 10 articles describing 14 nerve injuries in 12 patients (4). Twelve injuries occurred during removal of the implant and two upon implantation. The most common scenario was for a nerve to be pulled after having been mistaken for the implant. Most injuries involved the medial antebrachial cutaneous or median nerves, followed by the ulnar nerve. The basilic vein and brachial artery can also be affected. Median, and especially ulnar nerve injuries at this level in adults have a poor prognosis (5, 6).
Surprisingly few recommend placement in areas other than the medial upper arm, but the inner thigh and anterior abdominal wall have been suggested (7, 8). When inserting an implant in the upper arm, it is essential to follow the protocol carefully to ensure that the implant is inserted subdermally and, in particular, that it is positioned sufficiently posterior to the sulcus between the biceps and triceps muscles. A distance of 3–5 cm is recommended, but could well be increased further to ensure that the implant is overlying the triceps muscle. A study of 40 cadaveric arms provides support for this practice (9).
Upon removal, the implant must be stabilised by palpation. The distal part of the implant is pushed upwards so that the skin forms a 'tent' over the end. A small incision can then be made close to the rod, enabling it to be removed without difficulty. If the implant is non-palpable, it may have been inserted too deeply or it may have migrated within the upper arm or intravascularly (10, 11). Contraceptive implants that are difficult to palpate can be localised with X-rays (they contain barium sulphate) or ultrasound. Deeper positioning increases the risk of nerve damage. In the event of a non-palpable implant, the patient should be referred to a surgeon with expertise in peripheral nerve surgery (12) so that the implant can be removed in the safest way possible. In Norway, surgery on peripheral nerves is performed by hand surgeons. Surgical access must be increased to 4–5 cm to allow the contraceptive implant to be visualised and to provide a sufficient view of the surrounding structures prior to removal.
In summary, it is important that healthcare professionals who insert contraceptive implants follow the guidelines carefully, and that they receive sufficient training in the procedure. For the removal of an implant that is difficult to palpate, the patient should be referred to a surgeon experienced in operating close to nerves and blood vessels. If nerve damage is suspected, the closest Hand Surgical department should be contacted by telephone, and the patient referred for urgent care. Further investigation (such as neurophysiological testing) is unnecessary and leads to delay in treatment. The waiting time for surgery is an important prognostic factor, particularly in partial nerve injuries where the development of a neuroma can quickly complicate reconstruction.