Upper Limb Peripheral Nerve Injuries Associated With Subdermal Contraceptive Implants: A Case Series, Systematic Review, and Proposed Evidence-based Treatment Algorithm.

BACKGROUND: Subdermal contraceptive implants (SCIs) are a widely used form of long-acting reversible contraception (LARC) with high efficacy (Pearl Index 0.00, 95% CI: 0.00-0.14). However, upper limb neurovascular injuries related to SCI insertion and removal are increasingly reported. The true incidence of these complications cannot be reliably estimated from the current literature, which is largely limited to case reports and small case series, although sporadic cases are being described with increasing frequency. These injuries may result in significant morbidity, including chronic neuropathic pain, sensorimotor deficits, and functional impairment, yet standardized management guidelines remain lacking. This study aims to systematically review the literature on SCI-associated upper limb peripheral nerve injuries and present a case series of affected patients treated by the senior authors. The findings are intended to inform evidence-based recommendations for the prevention and management of these injuries.

METHODS: Following PRISMA guidelines, a systematic review of the literature was conducted to identify and characterize SCI-associated PNIs. Data extraction included demographics, injury-related factors (incidence, clinical presentation, implant type, timing of injury (insertion/removal), nerve injury classification and functional deficits at presentation, and treatment-related factors (management strategies and patient outcomes at latest follow-up). A prospectively collated bi-institutional case series of patients presenting with PNI's following SCI procedures is also presented.

RESULTS: This systematic review identified 24 patients (mean age 28.5 y, range: 19 to 51) with 26 PNIs linked to subdermal contraceptive implants. Most injuries occurred during removal (67%), with the ulnar nerve most frequently affected (52% n=14), followed by the median (26% n=7) and medial antebrachial cutaneous nerves (22% n=6). Injury severity included neuropraxia (33%, n=9), axonotmesis (26%, n=7), axonotmesis with neuroma-in-continuity (33%, n=9), and partial nerve transection (7%, n=2). Surgical intervention was required in 56% (n=13) of cases. At the latest follow-up, 39% (n=9) achieved full recovery, 43% (n=10) had partial recovery, and 9% (n=2) had no recovery. Our case series of 6 patients mirrored these findings, with injuries ranging from transient neuropraxia to persistent deficits.

CONCLUSIONS: SCI-associated PNIs can cause significant morbidity. The ulnar nerve is particularly at risk, especially during removal, with implant impalpability contributing to injury severity. This study underscores the need for enhanced practitioner training, improved insertion and removal techniques, and consideration of alternative insertion sites to mitigate nerve injury risks. Image-guided removal should be standard practice for impalpable implants.