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TOTAL OSSICULAR REPLACEMENT PROSTHESIS (TORP)

A Comprehensive Account for 50 Marks — RGUHS ENT

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1. DEFINITION

"A total ossicular replacement prosthesis (TORP) is used when the superstructure is absent." — Cummings Otolaryngology, Head & Neck Surgery

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2. ANATOMY & PHYSIOLOGY — BASIS OF OSSICULOPLASTY

Normal Ossicular Chain

• Malleus → Incus → Stapes (superstructure) → Oval window
• Amplification ratio = 22:1 (area ratio 17:1 + lever ratio 1.3:1)
• Loss of any component → maximal conductive hearing loss of 55–60 dB (acoustic coupling only)

Pathological Situations Requiring TORP

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3. INDICATIONS FOR TORP

1. Absent stapes superstructure with absent incus and/or malleus
2. Cholesteatoma surgery (canal wall down or wall up) with total ossicular erosion
3. COM — squamous type with total ossicular destruction
4. Revision ossiculoplasty after failed PORP/incus interposition
5. Post-traumatic ossicular discontinuity involving stapes
6. Congenital aural atresia reconstruction
7. Tympanosclerosis with total ossicular fixation and failed mobilisation

• Active middle ear infection / otorrhoea (relative)
• Only hearing ear (caution)
• Poor Eustachian tube function
• Sensorineural hearing loss > 30 dB (poor benefit)
• Open/wet mastoid cavity (elective ossiculoplasty results unsatisfying — Cummings, Box 145.2)

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4. PREOPERATIVE ASSESSMENT (Key Points — Box 145.2, Cummings)

1. ABG > 20–25 dB → consistent with ossicular discontinuity/fixation
2. ABG < 30 dB → approach with caution
3. Bone conduction > 30 dB → results often unsatisfactory
4. Severe mixed hearing loss → TORP can still enhance amplification
5. Improving the poorer ear to within 15 dB of the contralateral ear → facilitates binaural input

• Near-maximal flat conductive hearing loss, 55–60 dB
• Tympanogram: Type Ad (deep, hypercompliant — wide excursion due to discontinuity)
• No Carhart notch (unlike fixation)

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5. TYPES / CLASSIFICATION OF OSSICULAR PROSTHESES

A. By Extent of Replacement

B. By Material (Cummings, Scott Brown, Dhingra)

• Sculpted incus / malleus head (gold standard historically)
• Advantages: biocompatible, no cost, no extrusion risk
• Disadvantages: OR sculpting time, risk of disease recurrence in cholesteatoma, may demineralise

• Irradiated ossicles from bone banks
• Largely abandoned due to infection risk (HIV, prion concerns)

"Titanium and nontitanium prostheses show no significant difference in stability or effectiveness of sound transmission — meta-analysis of 12 studies, 1388 patients." — Zhang et al., cited in Cummings

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6. DESIGN FEATURES OF A TORP

┌────────────────────────────────────────────────────────────────┐
│               TORP — STRUCTURAL COMPONENTS                     │
│                                                                │
│   [HEAD / PLATFORM]  ──── cartilage cap placed here           │
│         │                contacts undersurface of TM          │
│         │                                                      │
│      [SHAFT]         ──── variable length (3–7 mm)             │
│         │                perpendicular to footplate           │
│         │                                                      │
│   [FOOT / BASE]      ──── sits on STAPES FOOTPLATE             │
│                           ± shoe/anchor for stability          │
└────────────────────────────────────────────────────────────────┘

• Fixed-length TORP — standard
• Adjustable/telescoping TORP — intraoperative length adjustment (e.g., Kurz Aerial TORP)
• Ball-joint TORP — allows angular correction
• Titanium/HA composite — combines osseointegration + flexibility

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7. TYMPANOPLASTY CLASSIFICATION (Wullstein) — CONTEXT FOR TORP

TORP = Tympanoplasty Type III (columellar reconstruction) when stapes superstructure is absent

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8. SURGICAL TECHNIQUE — STEP-BY-STEP

Pre-operative Planning

• HRCT temporal bone — assess ossicular chain, stapes footplate status, tegmen, sigmoid sinus
• Pure tone audiogram (PTA) + tympanogram
• Disease-free middle ear or staged procedure

Anaesthesia

• General anaesthesia (preferred) or local with sedation

Approach

• Endaural / Post-auricular approach
• Elevation of tympanomeatal flap
• Wide meatoplasty if cavity present

Steps of TORP Placement

FLOWCHART — TORP SURGICAL PROCEDURE
─────────────────────────────────────────────────────────────
Incision (endaural or postaural)
        │
Elevation of tympanomeatal flap
        │
Inspect ossicular chain intraoperatively
        │
Disease clearance (cholesteatoma/granulation)
        │
Assess stapes footplate — mobile? intact?
        │
        ├── Footplate mobile → TORP placement
        │
        ├── Footplate fixed → Stapedotomy/Stapedectomy FIRST
        │         ↓
        │    Then TORP on new opening / Gelfite wire
        │
Measure middle ear depth (footplate to TM)
        │
Select appropriate TORP length (3–7 mm)
        │
Place TORP shaft on stapes footplate
        │
Insert cartilage cap (tragal/conchal, 0.5–0.7 mm)
between prosthesis head and TM (perichondrium
facing TM, bare surface facing prosthesis)
        │
Position TM graft (fascia/perichondrium)
over cartilage and prosthesis head
        │
Ensure TORP is:
  - Perpendicular to footplate
  - In parallel piston motion with footplate
  - Minimal tension on TM
  - Not touching facial ridge
        │
Gelfoam packing in middle ear for stabilisation
        │
Closure of tympanomeatal flap
─────────────────────────────────────────────────────────────

Key Technical Points (Cummings, Scott Brown)

• TORP must move in piston-like motion parallel to the stapes footplate
• Positioned perpendicular to the TM
• Cartilage cap is mandatory between prosthesis head and TM — reduces extrusion, prevents drum erosion
• Perichondrium faces TM; bare cartilage faces prosthesis
• Silastic sheeting or hyaluronic acid sheets in middle ear prevent fixation of graft to promontory
• Proper sizing critical: too short → reduced high-frequency transmission + risk of dislodgement; too long → dampens low-frequency transmission + stapes footplate subluxation/perilymph leak

Intraoperative Assessment Diagram

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9. STAGING

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10. FACTORS AFFECTING OUTCOME (Dornhoffer & Gardner — cited in Cummings)

1. Mucosal fibrosis
2. Revision ear surgery
3. Absence of the malleus
4. Removal of the ear canal wall (canal wall down procedure)

• Prosthesis length and orientation
• Surgeon experience (more critical than the prosthesis chosen)
• Middle ear aeration and Eustachian tube function
• Cartilage interposition technique

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11. RESULTS

Hearing Outcomes

• TORP consistently yields poorer hearing results than PORP — because contact with the footplate rather than the superstructure is biomechanically less efficient
• Long-term follow-up: Significant progressive deterioration of hearing gain reported regardless of material used

Austin-Kartush Classification of Ossicular Chain Status (Prognostic)

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12. COMPLICATIONS

Intraoperative

• Perilymph gusher (footplate fracture/subluxation)
• Sensorineural hearing loss
• Facial nerve injury
• Dislodgement during graft placement

Postoperative

• Hydroxyapatite: lower extrusion than PTFE in some series
• Titanium TORP: ~5% extrusion (Kurz 5-year data)
• Use of cartilage interposition cap significantly reduces extrusion

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13. RECENT ADVANCES

1. Titanium Prostheses (Most Widely Used Currently)

• Kurz Aerial TORP, Medtronic Stapes Bell, Olympus Clip TORP
• Advantages: lightweight, corrosion-resistant, MRI-compatible (up to 3T), osseointegration, standardised sizes
• The "cartilage shoe" technique (anchor on footplate) — reduces medial displacement

2. Adjustable/Telescoping Prostheses

• Intraoperative fine-tuning of length
• Kurz Vario TORP — adjustable in 0.25-mm increments
• Reduces need for multiple prosthesis sizes

3. Endoscopic Ossiculoplasty (Transcanal Endoscopic Ear Surgery — TEES)

• Better visualisation of the epitympanum and sinus tympani
• Single-handed technique
• Improved TORP placement accuracy, less scutum removal
• Comparable or superior outcomes to microscopic approach (multiple recent series, 2015–2022)

4. Piezoelectric Middle Ear Implants (Active TORP)

• Vibrant Soundbridge (MED-EL): Floating Mass Transducer attached to round window or footplate
• Eliminates need for external hearing aid in mixed hearing loss
• Indicated when conventional TORP fails repeatedly

5. 3D-Printed / Patient-Specific Prostheses

• Custom titanium TORP designed from preoperative CT
• Optimal length and angulation predetermined
• Promising early results — reduces intraoperative adjustment

6. Bioactive Glass and HA-Coated Titanium

• HA coating on titanium shaft → improved osseointegration with footplate annular ligament
• Bioglass (Ceravital) — bioactive bond with bone

7. Cartilage Shoe Anchoring Technique

• Titanium TORP anchored with a small cartilage "shoe" on the footplate
• Long-term results: ABG < 20 dB in 82% PORP / 63% TORP at 5 years (Hess-Erga)
• Reduces lateral migration

8. Osseointegrated Bone Anchored Devices (Alternative to TORP)

• Baha (Cochlear Americas), Ponto (Oticon Medical), Bonebridge (MED-EL)
• For failed repeated TORP, aural atresia, or mixed hearing loss with ABG > 35 dB
• Superior speech recognition compared to conventional hearing aids (de Wolf et al.)

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14. COMPARISON: TORP vs PORP

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15. POSTOPERATIVE CARE

• Waterproof ear dressing × 2 weeks
• Antibiotics + topical antibiotic drops
• Avoid nose-blowing, air travel, heavy lifting × 4–6 weeks
• Audiogram at 6 weeks and 3 months postoperatively
• Regular follow-up for cholesteatoma surveillance (2nd look at 12 months if staged)

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16. DIAGRAMS & RADIOLOGICAL IMAGES

Diagram 1 — TORP Positioning (Cummings, Fig 145.12)

Diagram 2 — Postoperative HRCT Temporal Bone showing TORP in situ

Diagram 3 — TORP Extrusion Complication (Otoscopic view)

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17. SUMMARY FLOWCHART — DECISION ALGORITHM FOR OSSICULOPLASTY

PATIENT WITH CONDUCTIVE HEARING LOSS
            │
    ┌───────▼────────┐
    │ Assess ossicular│
    │ chain (HRCT +  │
    │ Intraoperative)│
    └───────┬────────┘
            │
    ┌───────▼──────────────────┐
    │ Stapes superstructure?   │
    └───────┬──────────────────┘
            │
    ┌───────┴──────────┐
    ▼                  ▼
PRESENT             ABSENT
    │                  │
    │          ┌───────▼──────────┐
    │          │ Footplate mobile? │
    │          └───────┬──────────┘
    │                  │
    │          ┌───────┴──────────┐
    │          ▼                  ▼
    │       MOBILE             FIXED
    │          │                  │
    │          │           Stapedotomy/
    │          │           Stapedectomy
    │          │                  │
    ▼          ▼                  ▼
  PORP      TORP               TORP
(capitulum  (footplate         (after
  to TM)    to TM)            stapedotomy)
    │          │
    ▼          ▼
Add cartilage cap between
prosthesis head and TM
    │
    ▼
Reposition TM graft (fascia/perichondrium)
    │
    ▼
Gelfoam pack for stabilisation
    │
    ▼
Postoperative audiogram at 6 weeks

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18. REFERENCES (Key Sources)

1. Cummings Otolaryngology Head and Neck Surgery (7th ed.) — Chapter 145: Ossicular Reconstruction
2. Scott Brown's Otorhinolaryngology, Head & Neck Surgery — Middle Ear Reconstruction
3. Dhingra PL — Diseases of Ear, Nose and Throat (7th ed.) — Tympanoplasty
4. Hazarika P — Textbook of ENT and Head & Neck Surgery
5. Stell & Maran's Head & Neck Surgery — Otological Reconstruction
6. Zakir Hussain — Clinical ENT
7. K.J. Lee's Essential Otolaryngology (available in library)
8. Hess-Erga J et al. — 5-year results, Kurz titanium TORP/PORP; JAMA Otolaryngol HNS
9. Zhang et al. — Meta-analysis titanium vs nontitanium prostheses (12 studies, 1388 patients)
10. Dornhoffer JL, Gardner E — Prognostic factors in ossiculoplasty (200 prostheses)
11. De Wolf et al. — Osseointegrated devices vs hearing aids in mixed hearing loss

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