14Revision and Reimplantation Surgery

TWhy implants come out: the spectrum of indications

Indications cluster into device-related causes (hard failure with loss of communication or measurable malfunction, soft failure with declining performance or non-auditory symptoms despite normal integrity testing) and recipient-related causes (recurrent infection, flap breakdown with device exposure, extrusion, and electrode migration). Across the literature the lifetime revision rate sits around 5%, and revision is consistently more common in children than adults, reflecting higher activity levels, head trauma, and longer years of device life at risk. A non-device reason for removal is increasingly the need for MRI or for resection of a tumour such as a vestibular schwannoma, where the magnet or the array would obscure imaging or be incompatible with the field strength required. Soft failure is a diagnosis of exclusion: progressive deactivation of more than three to five intracochlear electrodes, or fluctuating impedances without a hard fault, has been flagged as a warning sign that reimplantation may eventually be needed. In a large multicentre adult series, wound breakdown was the single most common significant complication and forced device removal in 2 of 253 ears (0.8%), underlining that the flap, not the electronics, is often the weak link.[2009][1997][2021][2005]

TProving a failure: integrity testing versus the patient's report

Manufacturers run remote integrity tests that interrogate the receiver-stimulator electronics; a hard failure shows up as a loss of telemetry or out-of-specification behaviour and is the cleanest justification for surgery. Soft failures pass every integrity test yet present with deteriorating speech scores, intermittent stimulation, aberrant percepts, pain, or shocks, and require a team consensus before a working device is removed. Impedance telemetry abnormalities in the postoperative period are uncommon, and because implants deliver constant current, rising impedance is compensated by voltage and may not change thresholds until circuits fail. Radiology has a defined role: plain films, rotational X-ray, or CT confirm whether an array has migrated, tip-rolled, or sits extracochlearly, since normal impedance and ECAP responses have been recorded even with electrodes lying outside the cochlea. A documented protocol that combines integrity testing, imaging, and behavioural data protects against both unnecessary surgery and the failure to act on a genuinely faulty device.[2014][2009][2005]

CThe explant-reimplant operation and the friendly fibrous tract

The skin incision follows the original scar; the overlying flap is often atrophic and must be handled gently, and monopolar cautery is forbidden for life once an implant is in place, so bipolar diathermy is the only safe option. The old receiver-stimulator is typically encased in a thick fibrous capsule that binds it immovably, while the lead is sheathed in fibrous tissue and sometimes new bone that has grown at the cochleostomy and a few millimetres into the scala. The fibrous sheath around the electrode is an asset on reinsertion: it marks the original tract into the scala tympani so the new array can usually be threaded to a depth comparable to the first, after any neo-ossification at the entry is removed with a pick or drill. New bone growth at the cochleostomy, thought to follow insertion trauma, is the commonest obstacle; it is cleared as in a primary procedure before the replacement array is advanced along the preserved channel. Risks specific to the second operation are further inner-ear trauma, difficulty re-inserting the array, and the possibility that performance will not match the original device, so families are counselled that improvement is likely but not guaranteed.[2001][2009][2003]

TOutcomes: a second cochlea that still works

Studies of revision surgery consistently show that the majority of reinsertions achieve electrode depth comparable to or better than the original, and that speech performance stays at baseline or improves in most patients. A representative reimplantation series found unchanged or improved speech-perception outcomes in about 85% of cases, with declined performance in roughly 15%, mirroring the spread reported for paediatric reimplantation. Device-survival figures are reassuring: contemporary cohorts report cumulative survival above 96% at 10 years and around 91% at 20 years, with one paediatric series reporting 97% at 5 years. About 72% of reimplantations in long-term cohorts occur within the first 5 years, so the early years carry most of the (small) failure burden and surveillance is weighted accordingly. Because outcomes are usually equal or better, a documented hard failure or intolerable soft failure justifies surgery with the realistic expectation that the recipient will return to or exceed their previous hearing level.[2001][2021][2013][2009]