---

PROSTHESIS IN OTOLOGY

A Comprehensive Review for 50 Marks

(As per RGUHS Syllabus — ENT / Otorhinolaryngology)

---

INTRODUCTION

---

CLASSIFICATION OF PROSTHESES IN OTOLOGY

PROSTHESES IN OTOLOGY
│
├── 1. MIDDLE EAR PROSTHESES
│     ├── Ossicular Replacement Prostheses (ORP)
│     │     ├── PORP (Partial Ossicular Replacement Prosthesis)
│     │     └── TORP (Total Ossicular Replacement Prosthesis)
│     ├── Tympanic Membrane Grafts (biological / synthetic)
│     └── Cartilage / perichondrium grafts
│
├── 2. STAPES PROSTHESES
│     ├── Stapedectomy prostheses (Fat + wire; Gelfoam + wire)
│     └── Stapedotomy pistons (Teflon, titanium, gold)
│
├── 3. BONE-ANCHORED PROSTHESES
│     ├── BAHA (Bone-Anchored Hearing Aid)
│     └── Bone Bridge / OSIA
│
├── 4. ACTIVE MIDDLE EAR IMPLANTS
│     ├── Vibrant Soundbridge (VSB)
│     └── Carina / Esteem
│
├── 5. COCHLEAR IMPLANTS
│     ├── Conventional cochlear implants
│     └── Hybrid / EAS (Electric-Acoustic Stimulation) devices
│
└── 6. EXTERNAL EAR PROSTHESES
      ├── Auricular prostheses (pinnaplasty/reconstructive)
      └── Obturators / ear molds

---

PART I: MIDDLE EAR PROSTHESES — OSSICULOPLASTY

A. Historical Background

• The concept of ossicular chain reconstruction was pioneered by Wullstein (1952) and Zöllner (1951), who classified tympanoplasty into types I–V.
• Shea (1958) performed the first successful stapedectomy with a polyethylene prosthesis, heralding modern prosthetic surgery.
• Early prostheses were autologous (reshaping the incus); later, homologous and alloplastic materials were introduced.
• As described in Scott-Brown's Otorhinolaryngology, Head and Neck Surgery (7th ed.) and Cummings Otolaryngology (7th ed.), ossiculoplasty has evolved from simple cortical bone struts to sophisticated titanium and hydroxyapatite prostheses.

---

B. Wullstein's Classification of Tympanoplasty (Foundation for Prosthetic Use)

---

C. Types of Ossicular Replacement Prostheses

1. PARTIAL OSSICULAR REPLACEMENT PROSTHESIS (PORP)

• Indication: Malleus present, incus absent/eroded, stapes suprastructure intact
• Function: Bridges from the tympanic membrane (or malleus handle) to the head of the stapes
• Structure: Cup-shaped head + shaft; the head supports the tympanic membrane/graft

PORP PLACEMENT:

Tympanic Membrane / Graft
         │
    [PORP Head — cup]
         │
      [Shaft]
         │
   Head of Stapes → Stapes Footplate → Oval Window → Inner Ear

---

2. TOTAL OSSICULAR REPLACEMENT PROSTHESIS (TORP)

• Indication: Complete absence of malleus + incus; only stapes footplate mobile
• Function: Bridges from tympanic membrane to the stapes footplate

TORP PLACEMENT:

Tympanic Membrane / Graft
         │
    [TORP Head — cup/flat]
         │
      [Long Shaft]
         │
   Stapes Footplate → Oval Window → Cochlea → Hearing

Key intraoperative tip (Hazarika's Textbook of ENT, 4th ed.): A small cartilage disc (0.5–1 mm) is placed between the TORP head and the graft to prevent extrusion and to improve acoustic coupling.

---

D. Materials Used for Ossicular Prostheses

---

E. Intraoperative Flowchart for Ossiculoplasty Decision-Making

INTRAOPERATIVE OSSICULAR STATUS ASSESSMENT
                │
    ┌───────────┴────────────┐
    │                        │
Malleus present?        Malleus absent?
    │                        │
    ▼                        ▼
Is incus present?    Stapes suprastructure
& mobile?             present?
    │                   │         │
   YES    NO            YES       NO
    │      │             │         │
    ▼      ▼             ▼         ▼
Type I  Incus           TORP    Stapes
(Graft  absent?    (TM→footplate) footplate
only)     │                    mobile?
          │                   YES → TORP
          ▼                   NO  → Stapedectomy
  Stapes head                      + TORP/piston
  intact?
  YES → PORP
  NO  → TORP

---

PART II: STAPES PROSTHESES (STAPEDECTOMY / STAPEDOTOMY)

A. Indications

• Otosclerosis (primary indication)
• Congenital stapes fixation
• Tympanosclerosis involving stapes footplate
• Post-traumatic stapes fixation

B. Historical Evolution (as per Scott-Brown and Cummings)

---

C. Types of Stapes Prostheses

1. Wire-Fat Piston (Shea's Original)

• Stainless steel wire loop crimped around incus long process
• Fat plug seals oval window

2. Teflon Piston

• Most widely used globally
• Diameter: 0.4–0.8 mm (standard 0.6 mm)
• Length: 4–4.5 mm
• Advantages: Chemically inert, low friction, easy handling

3. Titanium Piston

• Lightweight, excellent acoustic transfer
• MRI-compatible at 1.5T and 3T
• Lower heat conduction (safer with laser)
• Used in Fisch prosthesis, Kurz titanium clip piston

4. Gold Piston

• Dense → heavy acoustic mass; historically preferred by some surgeons
• MRI-compatible
• Less popular now due to titanium's advantages

5. Nitinol (Shape Memory Alloy) Piston — Recent Advance

• Self-crimping when warmed to body temperature (37°C)
• Eliminates manual crimping → reduces incus trauma
• Brand: Gyrus Medical NiTiBOND piston
• Reference: Otolaryngology-HNS 2019; Laryngoscope 2021

6. KTP/Diode Laser-Compatible Pistons

• Teflon or titanium — compatible with KTP (532nm), CO₂, and diode lasers for small fenestra stapedotomy

---

D. Stapes Prosthesis Placement — Flowchart

STAPEDOTOMY PROCEDURE (Fisch Small Fenestra Technique)
        │
        ▼
General/LA + Microscope/Endoscope
        │
        ▼
Elevation of tympanomeatal flap
        │
        ▼
Expose ossicular chain + confirm stapes fixation
        │
        ▼
Measure incus long process to footplate distance
(Standard: 4.0–4.5 mm)
        │
        ▼
Measure appropriate piston length (add 0.25–0.5mm)
        │
        ▼
Laser/micro-drill → 0.6mm fenestra in footplate center
        │
        ▼
Place piston through fenestra into vestibule
        │
        ▼
Crimp piston loop around incus long process
(or Nitinol self-crimps)
        │
        ▼
Blood/gelfoam seal around piston
        │
        ▼
Replace tympanomeatal flap
        │
        ▼
Audiological assessment at 6 weeks:
  ABG closure to < 10 dB = Success

---

E. Prosthesis Diagram — Stapes Surgery

---

PART III: BONE-ANCHORED HEARING AIDS (BAHA)

A. Concept

B. Indications (as per Dhingra 7th ed.; Scott-Brown 8th ed.)

1. Conductive hearing loss not amenable to surgical correction (canal atresia, chronic ear disease)
2. Mixed hearing loss with inadequate bone conduction
3. Single-sided deafness (SSD) — CROS-BAHA
4. Treacher Collins syndrome, microtia, bilateral atresia (children >5 years)
5. Failed conventional hearing aid users

C. Components

BAHA System Components:
┌─────────────────────────────────────────┐
│  EXTERNAL SOUND PROCESSOR               │
│   (microphone + amplifier + vibrator)   │
└──────────────────┬──────────────────────┘
                   │ (snapped onto abutment)
         ┌─────────▼──────────┐
         │    ABUTMENT         │
         │ (percutaneous/       │
         │  transcutaneous)    │
         └─────────┬───────────┘
                   │
         ┌─────────▼───────────┐
         │   TITANIUM IMPLANT  │
         │   (osseointegrated  │
         │   in mastoid bone)  │
         └─────────┬───────────┘
                   │ (vibration)
              SKULL BONE
                   │
              COCHLEA → Hearing

D. Types and Brands

---

PART IV: ACTIVE MIDDLE EAR IMPLANTS (AMEI)

A. Vibrant Soundbridge (VSB) — MED-EL

• A Floating Mass Transducer (FMT) — tiny electromagnetic transducer
• Attached to the round window, oval window, or ossicles
• Indicated for: moderate-to-severe SNHL, mixed HL, canal atresia
• Advantage: No occlusion effect; direct vibratory stimulation

VSB Components:
Microphone (behind ear) → Audio Processor (external) 
    → Transcutaneous RF coil 
        → Internal receiver-stimulator 
            → FMT on round window / incus 
                → Direct vibration to inner ear fluid

B. Esteem (Envoy Medical)

• Fully implantable active MEAI
• Piezoelectric sensor on incus → signal → processor → piezoelectric driver on stapes
• No external component; operates on battery (4.5–9 years)

---

PART V: COCHLEAR IMPLANTS

A. Components

COCHLEAR IMPLANT — COMPONENTS
┌──────────────────────────────────────────────────────┐
│           EXTERNAL COMPONENTS                        │
│  Microphone → Speech Processor → Transmitter coil   │
└──────────────────────────────────────────────────────┘
                        │ (RF signal through skin)
┌──────────────────────────────────────────────────────┐
│           INTERNAL COMPONENTS                        │
│  Receiver-stimulator (implanted in temporal bone)    │
│       │                                              │
│  Electrode array (22–24 electrodes)                  │
│       │ (inserted into scala tympani of cochlea)     │
│  Direct electrical stimulation → CN VIII → Brain    │
└──────────────────────────────────────────────────────┘

B. Indications (RGUHS & National Guidelines)

C. Electrode Designs

D. Outcomes (per Dhingra and RGUHS guidelines)

• Children implanted < 2 years: near-normal speech development in 70–80%
• Post-lingual adults: >80% open-set sentence recognition
• ABI (Auditory Brainstem Implant): For NF2 / cochlear aplasia — placed on cochlear nucleus

---

PART VI: TYMPANIC MEMBRANE PROSTHESES

A. Grafts for Myringoplasty (Biological Prostheses)

B. Cartilage Tympanoplasty (Recent Advance)

• Heermann's cartilage island flap / palisade technique
• Advocated especially in retraction pockets, atelectasis, revision surgery
• Provides structural support; lower re-perforation rates
• Reference: Dornhoffer JL — Otolaryngol Head Neck Surg 2003; Hazarika 4th ed. p. 145

---

PART VII: AURICULAR AND EXTERNAL EAR PROSTHESES

A. Bone-Anchored Auricular Prostheses

• For microtia, traumatic auricular loss, post-oncological resection
• Titanium implants placed in mastoid region (2–3 implants)
• Custom silicone pinna attached magnetically or by bar-clip system

B. Ear Canal Prostheses / Obturators

• For canal atresia reconstruction stenting
• Silicone molds for conforming meato/canaloplasty

---

PART VIII: COMPLICATIONS OF OTOLOGICAL PROSTHESES

COMPLICATIONS
│
├── INTRAOPERATIVE
│     ├── Sensorineural hearing loss (perilymph fistula)
│     ├── Incus fracture during crimping (stapes piston)
│     ├── Footplate "floating" or "sinking" (stapedectomy)
│     ├── Facial nerve injury
│     └── Perilymph gusher (abnormal CSF-perilymph communication)
│
├── EARLY POSTOPERATIVE
│     ├── Vertigo / BPPV
│     ├── Perilymph fistula → SNHL
│     ├── Infection (otitis media)
│     └── Tympanic membrane lateralization
│
└── LATE POSTOPERATIVE
      ├── Prosthesis extrusion (PORP/TORP most common)
      ├── Prosthesis migration/displacement
      ├── Fibrous tissue around implant (reduced mobility)
      ├── Reparative granuloma (Teflon)
      ├── Implant failure (BAHA screw loss)
      └── Re-perforation of TM graft

• Cartilage interposition between TORP head and TM graft
• Avoiding thin skin over the prosthesis
• Using biocompatible materials (HA, titanium preferred over Teflon for ossiculoplasty)

---

PART IX: CRITERIA FOR PROSTHESIS SELECTION

PROSTHESIS SELECTION ALGORITHM

           Assess Ossicular Status Intraoperatively
                         │
          ┌──────────────┼──────────────┐
          │              │              │
    Stapes arch      Stapes arch    Complete
      intact           absent       absence
          │              │              │
    Malleus         Footplate        Footplate
    present?          mobile?         mobile?
     YES  NO          YES  NO        YES   NO
      │    │           │    │         │     │
    PORP  TORP       TORP  Stapedectomy TORP  Staged
                          + TORP            procedure /
                                            Implant

---

PART X: RECENT ADVANCES IN PROSTHETICS IN OTOLOGY (2018–2024)

---

SUMMARY TABLE — PROSTHESES IN OTOLOGY AT A GLANCE

---

IMPORTANT EXAMINATION POINTS (RGUHS Focus)

1. Wullstein classification — know all 5 types and prosthesis used in each
2. PORP vs TORP — differences in indication, placement, and materials
3. Shea's stapedectomy — historical landmark; know the 1958 original procedure
4. Teflon piston specifications: 0.4–0.8mm diameter, 4.0–4.5mm length
5. BAHA indications — especially for children with bilateral atresia
6. Cochlear implant candidacy — children and adults criteria
7. Extrusion prevention — cartilage disc under TORP head
8. Materials biocompatibility: Titanium > Hydroxyapatite > Teflon > Polyethylene (in order of current preference)
9. Complications — perilymph fistula, reparative granuloma, extrusion
10. Recent advances — Nitinol piston, OSIA, 3D-printed prostheses, robotic stapedotomy

---

REFERENCES

1. Scott-Brown's Otorhinolaryngology, Head and Neck Surgery — 8th Edition (Gleeson et al.) — Vol. 2–3
2. Cummings Otolaryngology: Head & Neck Surgery — 7th Edition (Flint et al.) — Ch. 139, 140, 143, 160, 162, 163
3. Stell and Maran's Head and Neck Surgery — 5th Edition
4. Dhingra's Diseases of Ear, Nose and Throat — 7th Edition — pp. 101–145
5. Hazarika's Textbook of ENT, Head and Neck Surgery — 4th Edition
6. Zakir Hussain's Textbook of ENT — Chapter on otology
7. Bailey and Love's Short Practice of Surgery — 28th Edition, p. 777
8. Dornhoffer JL — Cartilage Tympanoplasty — Otolaryngol Head Neck Surg, 2003
9. Fisch U, May J — Tympanoplasty, Mastoidectomy and Stapes Surgery — Thieme
10. Laryngoscope 2021 — Nitinol self-crimping stapedotomy pistons
11. Otol Neurotol 2022 — Slim modiolar electrode array outcomes
12. Nature Neuroscience 2020 — Optical cochlear implants
13. ORL: Journal of Oto-Rhino-Laryngology — Robotic stapedotomy 2023

---