[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Anatomy](https://durgical.com/en/anatomy/) › [Head and neck](https://durgical.com/en/anatomy/region/head-and-neck/) › Stapes [Sense organs](https://durgical.com/en/anatomy/system/sense-organs/) · [Head and neck](https://durgical.com/en/anatomy/region/head-and-neck/) # Stapes The stapes (stirrup) is the smallest bone in the body, the last middle ear bone; its footplate passes sound into the inner ear and stiffens in otosclerosis. [See in 3D →](https://durgical.app/?from=durgipedia&lang=en#region=head_neck&select=stapes&side=r) Opens in the Durgical app, no sign-up needed. ## What it is The smallest bone in the body, its footplate in the oval window; it stiffens in otosclerosis. ## What it does Passes and amplifies the [eardrum](https://durgical.com/en/anatomy/tympanic-membrane/) 's vibrations to the inner ear. ## Key points - Footplate held in the oval window by the [annular ligament](https://durgical.com/en/anatomy/annular-ligament-of-the-radius/); its piston movement pushes on the perilymph of the vestibule - Stapedius (facial nerve) inserts on its neck and damps loud sound (acoustic reflex); a facial palsy above the nerve to stapedius causes hyperacusis - Otosclerosis: conductive loss with a normal drum, a dip in bone conduction near 2 kHz (Carhart notch) and an absent acoustic reflex; treated surgically by stapedotomy - From the second pharyngeal arch (Reichert cartilage); the footplate is partly from the otic capsule ## Key facts **Joints with** Incus; footplate in the oval window **Landmarks** Head, neck, anterior and posterior limbs, footplate; smallest bone ## Relations **Lateral** Lenticular process of the [incus](https://durgical.com/en/anatomy/incus/) at the incudostapedial joint **Medial** Footplate in the oval window, opening onto the vestibule of the inner ear, with the saccule and utricle beyond **Above** Tympanic segment of the [facial nerve](https://durgical.com/en/anatomy/facial-nerve/) in its bony canal, just above the oval window; the canal is often thin or open here **Behind** Stapedius tendon, emerging from the pyramidal eminence on the posterior wall to reach the neck **Below** Promontory, the bulge of the basal turn of the [cochlea](https://durgical.com/en/anatomy/cochlea/), with the round window below and behind it ## How to find it Not seen through a normal eardrum. At surgery it is exposed by lifting the eardrum and removing a little bone from the posterosuperior canal wall, which shows the incudostapedial joint, the stapedius tendon and the facial nerve above. ## Examination - Rinne negative (bone louder than air) on the affected side and Weber lateralising to it: conductive loss, as in otosclerosis - Acoustic (stapedial) reflex testing: absent when the stapes is fixed or the facial nerve is interrupted proximal to the nerve to stapedius ## On imaging Too small for radiographs; high-resolution [temporal bone](https://durgical.com/en/anatomy/temporal-bone/) CT shows its crura and the footplate in the oval window. In fenestral otosclerosis, CT shows a lucent focus just in front of the oval window and sometimes a thickened footplate; cochlear otosclerosis adds a lucent ring around the cochlea (double ring). After stapes surgery, CT checks the position of the prosthesis. ## Common problems - Otosclerosis: bone grows around the stapes footplate and fixes it, causing slowly worsening hearing loss. ## How it is diagnosed Hearing tests showing a conductive loss with a normal eardrum. ## Treatment - Hearing aids. - Stapes surgery (stapedotomy) that replaces it with a tiny piston. ## Clinical notes - Otosclerosis is usually bilateral, often familial and may progress in pregnancy; a reddish blush on the promontory seen through the drum (Schwartze sign) marks the active phase - Stapedotomy: a small opening is made in the fixed footplate and a piston prosthesis is hooked onto the incus; risks include sensorineural loss, vertigo and taste change from chorda tympani injury - Hearing aids are the non-surgical alternative for the conductive loss of otosclerosis - A low-lying or exposed facial nerve overhanging the oval window can block access in stapes surgery ## Anatomical variants - Persistent stapedial artery running through the arch of the stapes: rare, a bleeding risk in stapes surgery - Congenital stapes fixation or malformation, sometimes with other second-arch anomalies ## Development The stapes forms from the second pharyngeal arch, its footplate partly from the otic capsule; the stapedial artery passes through its arch in the embryo and normally disappears. ## Related conditions - [Hearing loss (conductive and sensorineural, including sudden hearing loss)](https://durgical.com/en/conditions/hearing-loss/) - [Otosclerosis](https://durgical.com/en/conditions/otosclerosis/) ## Test yourself Think of the answer, then tap the question to see it. ## Which muscle inserts on the stapes, what is its nerve, and what follows its paralysis? The stapedius, supplied by the facial nerve; a facial palsy above the nerve to stapedius causes hyperacusis. ## What are the audiological features of otosclerosis? Conductive loss with a normal drum, a bone-conduction dip near 2 kHz (Carhart notch) and an absent acoustic reflex. ## What does a stapedotomy involve? A small opening in the fixed stapes footplate with a piston prosthesis hooked onto the incus; risks include sensorineural loss, vertigo and taste change. ## Which nerve lies just above the oval window and the stapes, often in a thin or open bony canal? The tympanic segment of the facial nerve. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/anatomy/stapes/) Educational information, not medical advice. For any symptom, see a health professional. ## Its names **Official Latin (TA2)** stapes TA2 895 **Official Spanish (DeCS)** Estribo DeCS D013199 **English (TA2)** Stapes **Also called** stirrup ## Related - [Incus](https://durgical.com/en/anatomy/incus/) - [Vestibule](https://durgical.com/en/anatomy/vestibule/) - [Temporal bones](https://durgical.com/en/anatomy/temporal-bone/) Sources: Terminologia Anatomica (TA2); [DeCS](https://decs.bvsalud.org/es/ths/resource/?id=13586); [Otosclerosis](https://www.ncbi.nlm.nih.gov/books/NBK560671/); [Ear, Hearing, and Facial Nerve Evaluation](https://www.ncbi.nlm.nih.gov/books/NBK556014/). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/anatomy/stapes/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/stapes/