Stapes prostheses

What a stapes prosthesis is

In otosclerosis the footplate of the stapes becomes fixed and stops passing vibration into the inner ear. Stapes surgery bypasses it. A tiny piston-shaped prosthesis — often called a stapes implant — is attached at one end to the long process of the incus, the middle of the three hearing bones. Its other end passes into a small opening in the footplate, the fenestra, and rests in the inner-ear fluid. Each movement of the eardrum and incus now drives the piston, and the piston moves the fluid.

It is one of the smallest implants in ear surgery. The shaft is usually 0.4–0.6 mm in diameter, matched to a fenestra of about 0.4–0.7 mm. The length, measured during the operation from the incus to the footplate, is typically 4.25–4.75 mm: too short and sound is transmitted poorly, too long and it can cause dizziness.

The first modern stapes prosthesis was a carved Teflon replica of the stapes placed over a vein graft. Designs have since followed two lines: prostheses resting on a tissue graft after removal of the whole footplate, and pistons passing through a small opening — see stapedectomy or stapedotomy.

Materials

Every prosthesis has a shaft, the piston, and an attachment at the incus end — a loop, ribbon, hook or clip — and the two are often made of different materials. A fluoroplastic piston with a platinum or titanium loop is a common combination, so “a Teflon piston” may still contain a little metal.

• Fluoroplastic (Teflon). The original material: light, inert and non-metallic.
• Platinum. A soft metal, easy to shape, used mainly for loops.
• Titanium. Light, strong and well tolerated; used for pistons, loops and clips.
• Gold. Used for the piston in some designs.
• Stainless steel. Used for decades. One magnetic type from the 1980s was recalled (see MRI below).
• Nitinol. An alloy of nickel and titanium with “shape memory”. In heat-activated designs the loop closes around the incus to a pre-set shape when warmed briefly, usually with a laser (see laser stapedotomy). In the newer superelastic designs the loop springs back by itself and grips the incus without heat or crimping. If you have a known nickel allergy, mention it before surgery.

Good results are reported with many different prostheses, provided the surgeon is experienced with the one chosen, and pooled data show comparable hearing with the two nitinol families. Whether one material gives clinically better hearing than another remains debated. The choice is the surgeon’s, guided by the anatomy found at operation.

Attaching the prosthesis: crimping and the incus

Attaching the prosthesis to the incus is the most delicate mechanical step. The long process of the incus is thin, and its blood supply is fragile.

With a conventional loop, the surgeon closes it around the incus with fine forceps — crimping. Too loose, and sound is transmitted poorly or the prosthesis can slip. Too tight, and the loop can compress the blood supply of the bone. Over months or years the tip of the incus may then erode (incus necrosis): the loop loosens, the piston no longer moves properly, and the hearing gain fades.

Self-crimping designs — heat-activated and superelastic nitinol, and clips that snap onto the incus — were developed partly to make this step more reproducible and to prevent over-tightening. They have not abolished incus erosion, though it is uncommon. Together with displacement of the prosthesis and scar around the oval window, it is one of the most common findings when a stapes result fades; see revision ear surgery.

When the incus cannot be used

At revision the incus may be found eroded, dislocated or fixed. If enough remains, a new prosthesis can sometimes be attached further up. If not, a longer prosthesis can run from the malleus — the first hearing bone, attached to the eardrum — directly to the opening in the footplate: a malleus-to-footplate prosthesis, or malleostapedotomy. It is more demanding, and the results are more modest than those of a first stapedotomy. Reconstruction for other conditions is covered on ossiculoplasty.

MRI after stapes surgery

MRI uses a very strong magnet. The concern with a metal implant is that the magnet could pull, twist or heat it; for a stapes prosthesis, a piston shifting in the opening to the inner ear could affect hearing or balance. What is known:

• At 1.5 tesla, none of 18 commonly used middle-ear prostheses moved in laboratory testing, and the original heat-activated nitinol prosthesis did not move either.
• At 3 tesla, three prostheses moved noticeably when lying loose in a dish, but not when fixed in place in human temporal bones. A 2024 systematic review found laboratory movement reported with a few stainless-steel types, no displacement in temporal-bone studies, and no reported harm in patients.
• The 1980s exception. In the 1980s a small number of patients received a prosthesis made of a magnetic (ferromagnetic) stainless steel. It was recalled and has not been used since 1987; reviews identify it as the 1987 McGee prosthesis. For anyone with a 1980s prosthesis, the review advised scanning at 1.5 T as a precaution.
• Overall, the review concluded that modern (post-1987) stapes prostheses do not pose a risk in the body during MRI. A review of manufacturers’ information found stapes prostheses other than the McGee prosthesis labelled MR Conditional for 1.5 T, and many for 3 T.

What “MR Conditional” means. MRI departments go by each implant’s labelling. MR Safe means no known hazard in any scanner — for example an implant made entirely of non-magnetic, non-conducting material. MR Conditional means safe under the conditions the manufacturer specifies, such as the maximum field strength. MR Unsafe means it must not enter the scanner. The conditions belong to a specific make and model, and approvals can differ between countries. This page cannot tell you whether your own prosthesis is cleared for a particular scanner; the MRI team checks the labelling for your model.

In practice:

• Tell the MRI department — on the safety questionnaire and in person — that you have had stapes surgery, on which side and when.
• Bring the implant card or operation note giving the manufacturer, model and material. If you have neither, ask the hospital where you were operated for a copy of the operation note.
• Soon after surgery. If a scan is planned in the first weeks after the operation, tell the radiology department and your surgeon. Whether and how the scan can be done is decided by the labelling of your specific prosthesis.
• After the scan, as at any time after stapes surgery, a sudden change in hearing, new dizziness or loud new tinnitus is a reason to contact your clinic; severe spinning vertigo or a sudden complete loss of hearing needs same-day care. See when to contact your surgeon.

CT scans, airport security and everyday devices

• CT scans use X-rays, not a magnet. The prosthesis is no obstacle, and CT is the scan used to check its position when a result fades — see interpreting hearing tests.
• Airport security. A stapes prosthesis contains very little metal, or none, and is not expected to set off metal detectors or body scanners. Carrying your implant card does no harm. Flying itself waits until the ear has healed, from two weeks to two months depending on the surgeon — see flying after ear surgery.
• Everyday devices — mobile phones, headphones, hearing aids — are not known to affect a stapes prosthesis.

What to keep

Many hospitals and manufacturers provide an implant card or label recording the manufacturer, product name, reference and lot number, diameter and length, with the date and side of the operation. Keep it with your medical documents, photograph it, and keep a copy of the operation note, which should describe the prosthesis and what was found. After more than one operation, keep the records of each: a revision may have replaced the original prosthesis. These records are also the starting point for any future surgeon if a result fades.

Sources

• Daher GS, Kocharyan A, et al. MRI safety of stapes prostheses: a systematic review. Otol Neurotol. 2024;45(5):469-474. PubMed
• Azadarmaki R, Tubbs R, et al. MRI information for commonly used otologic implants: review and update. Otolaryngol Head Neck Surg. 2014;150(4):512-519. PubMed
• Fritsch MH, Gutt JJ. Ferromagnetic movements of middle ear implants and stapes prostheses in a 3-T magnetic resonance field. Otol Neurotol. 2005;26(2):225-230. PubMed
• Knox GW, Reitan H. Shape-memory stapes prosthesis for otosclerosis surgery. Laryngoscope. 2005;115(8):1340-1346. PubMed
• Achena A, Pacelli L, et al. Nitinol prosthesis in stapes surgery: evolution from heat-activated to superelastic nitinol: a systematic review. J Clin Med. 2025;14(4):1069. PubMed
• Sevy A, Arriaga M. The stapes prosthesis: past, present, and future. Otolaryngol Clin North Am. 2018;51(2):393-404. PubMed
• Babighian GG, Albu S. Failures in stapedotomy for otosclerosis. Otolaryngol Head Neck Surg. 2009;141(3):395-400. PubMed
• Alicandri-Ciufelli M, D’Alessandro E, et al. Malleostapedotomy in patients with stapes fixation: a systematic review. Laryngoscope. 2026;136(4):1601-1613. PubMed

This page provides general educational information. It cannot replace an individual assessment, which depends on a full history, examination, audiometry and, where relevant, imaging. If you have sudden hearing loss, severe pain, facial weakness, severe dizziness or discharge with fever, seek medical care promptly.