THYROPLASTIES - A Comprehensive 50-Mark Answer

(For RGUHS University Examinations)

INTRODUCTION

• Historical credit: Payr (1915) described the first laryngeal framework surgery
• Modern refinement: Isshiki (1974) systematized LFS into four types using alloplastic implants (Silastic), emphasizing local anesthesia with awake voice feedback
• Eponym: Isshiki's four-type classification remains the universally accepted standard

ISSHIKI CLASSIFICATION OF THYROPLASTIES

Figure: Types I, II, III and IV laryngeal framework thyroplasties as described by Isshiki (Scott-Brown's, Fig. 67.10)

TYPE I THYROPLASTY (MEDIALIZATION THYROPLASTY)

Definition

INDICATIONS

• Unilateral vocal fold paralysis (idiopathic, post-thyroid surgery, post-cardiac surgery, vagal nerve palsy)
• Vocal fold bowing (presbylaryngis / aging)
• Sulcus vocalis
• Cricothyroid joint fixation
• Soft tissue defects after tumor excision

• Aspiration due to glottic incompetence (even before 12-month observation period if aspiration is severe)
• Post-radiotherapy scar with glottic insufficiency
• Atrophic vocal folds

• For idiopathic VF paralysis: wait 12 months for possible spontaneous recovery before permanent medialization
• Injection laryngoplasty bridges this period
• If aspiration is life-threatening, early permanent medialization is warranted

CONTRAINDICATIONS

• Bilateral VF paralysis in median position (risk of airway compromise)
• Active laryngeal malignancy
• Poor surgical candidate
• Patient unwilling to tolerate awake procedure
• Active laryngeal infection / chondritis

PREOPERATIVE ASSESSMENT

History & Physical
       |
   Laryngoscopy ──────► Rigid / Flexible fiber-optic
       |
   Stroboscopy ───────► Mucosal wave, VF gap assessment
       |
   Voice analysis ────► Maximum phonation time (MPT), GRBAS scale,
                        Acoustic analysis (jitter, shimmer, HNR)
       |
   Swallowing study ──► FEES / Videofluoroscopy (if aspiration suspected)
       |
   Imaging ───────────► CT/MRI neck (if cause unknown, rule out malignancy)
       |
   EMG ───────────────► Laryngeal EMG (prognosis of recovery - optional)

SURGICAL ANATOMY - VOCAL FOLD LEVEL ON THYROID CARTILAGE

"A point half the distance between the anterior-inferior border of the thyroid cartilage and the thyroid notch defines the level of the true fold." (Cummings, p. 1156)

Figure: Window dimensions and location on thyroid cartilage (Scott-Brown's, Fig. 67.11). Critical point (), x = 12 mm male / 10 mm female from midline, y = 5 mm male / 4 mm female above inferior border.*

IMPLANT MATERIALS

SURGICAL TECHNIQUE - STEP BY STEP

POSITION: Supine, neck slightly extended
ANESTHESIA: Local anesthesia (1% lidocaine + adrenaline)
            Light sedation optional
            AWAKE patient essential for voice feedback

• Incise platysma
• Elevate subplatysmal flaps superiorly (to thyroid notch) and inferiorly
• Split strap muscles in midline
• Retract strap muscles laterally off thyroid lamina preserving outer perichondrium
• Single skin hook in contralateral ala for exposure

• Outline cartilage window with template / electrocautery
• Window dimensions:
  • VoCoM system: 6 mm (V) × 10 mm (H)
  • Netterville system: 6 mm (V) × 13 mm (H)
• Window position:
  • Anterior border: 5-8 mm from midline (women), 8-10 mm (men)
  • Superior border: at the level of the true vocal fold
• Incise outer perichondrium, elevate off cartilage
• Remove cartilage with bur/Kerrison punch
• Preserve inner perichondrium
• Elevate inner perichondrium circumferentially with laryngeal elevator to create paraglottic space

• Insert sizing templates (3 to 8 mm displacement) one by one
• All retractors removed - patient phonates
• Move template through four quadrants of window testing optimal position
• Select best template (usually largest that maintains voice quality)
• Insert final implant secured with shim
• If shim unstable: suture through neck of implant tied over titanium mini-plate

• Awake patient phonates throughout to optimize position
• Assess: breathiness, pitch, volume, effort

• Check for air leak (fill wound with saline; patient phonates - bubbling = mucosal breach)
• Suction drain deep to strap muscles
• Approximate strap muscles and platysma with 4-0 absorbable
• Skin: 5-0 subcuticular running suture
• Dexamethasone pre-operatively to minimize edema
• Antibiotics for 5 days post-op

WINDOW PLACEMENT - FLOWCHART

Identify thyroid notch (superiorly)
            |
Identify inferior border of thyroid cartilage
            |
Mark midpoint between notch and inferior border
            |
This midpoint = TRUE VOCAL FOLD LEVEL
            |
Draw horizontal line at this level (= glottic plane)
            |
Measure from midline:
  Women → 5-8 mm posterior to midline (anterior border)
  Men   → 8-10 mm posterior to midline
            |
Superior border of window = at vocal fold level
            |
Window dimensions:
  VoCoM:      6 mm H × 10 mm V
  Netterville: 6 mm H × 13 mm V
            |
Most common error = placing window TOO HIGH
  → displaces false cord, not true fold
  → poor glottic closure (Scott-Brown's)

OUTCOME MEASURES

• Phonation time: 4.6 → 15 seconds (mean)
• Voice amplitude: 62.9 → 68.0 dB (p < 0.01)
• Hoarseness significantly improved (p < 0.001)
• Breathiness significantly improved (p < 0.001)

COMPLICATIONS OF TYPE I THYROPLASTY

LIMITATIONS OF TYPE I THYROPLASTY

1. Purely static medialization - no effect on innervation or muscle mass
2. Cannot reliably close posterior glottic gap (cricoarytenoid joint limits)
3. Technically more demanding than injection laryngoplasty
4. Posterior glottic chink requires addition of arytenoid adduction
5. If paralyzed cord is on different vertical plane than normal cord - medialization alone insufficient

TYPE II THYROPLASTY (LATERALIZATION)

• Creates lateral displacement of vocal fold to widen the glottis
• Indicated for: Bilateral VF paralysis in midline (adductor) position, adductor spasmodic dysphonia
• Technique: Implant placed laterally through a window to push VF away from midline
• Often combined with posterior cordectomy or arytenoidectomy for bilateral paramedian VF paralysis

TYPE III THYROPLASTY (RELAXATION / SHORTENING)

• Shortens the vocal fold by collapsing the thyroid cartilage (removes a vertical strip)
• Effect: Decreases vocal fold tension → lowers fundamental frequency (pitch)
• Indicated for:
  • Excessively high-pitched voice (puberphonia/mutational falsetto unresponsive to speech therapy)
  • Post-thyroidectomy high pitch
  • Transgender females wanting lower pitch
• Technique: Vertical midline strip of thyroid cartilage removed; cartilage approximated with sutures/wire

TYPE IV THYROPLASTY (ELONGATION / TENSIONING)

• Increases vocal fold tension → raises fundamental frequency (pitch)
• Indicated for:
  • Mutational falsetto / puberphonia (rarely surgical)
  • Gender reassignment (male-to-female) - to raise pitch
  • Functional low-pitched voice
• Technique:
  • Separation of cricoid from thyroid cartilage anteriorly
  • Implants/sutures placed at cricothyroid space to maintain separation
  • Stretches vocal folds to increase tension

ARYTENOID ADDUCTION

• A large posterior glottic gap
• The paralyzed cord is at a different vertical level than the normal cord
• Type I alone cannot close posterior chink

• Arytenoid cartilage exposed, attached muscles divided
• Arytenoid fixed in midline position
• Suture placed between inferior horn of thyroid cartilage and cricoid anteriorly to add tension
• Combined with medialization thyroplasty

Posterior glottic gap assessment
          |
     Small gap                  Large gap
          |                          |
Type I alone sufficient     Paralyzed cord at same level?
                                 |            |
                                YES           NO
                                 |            |
                         Type I alone    Type I +
                          (may help)    Arytenoid Adduction
                                        (or Zeitels modification)

DECISION-MAKING ALGORITHM FOR THYROPLASTY

UNILATERAL VOCAL FOLD PARALYSIS
             |
    Will it recover?
    /              \
  YES               NO
   |                 |
Temporary         Permanent
Injection         Medialization
Laryngoplasty     (wait 12 months idiopathic)
(bridge therapy)         |
                    Evaluate glottis
                    /            \
              Small gap        Large posterior gap
                 |                    |
          Type I alone         Type I + Arytenoid
                                   Adduction
                                        |
                               Consider reinnervation
                               (ansa cervicalis to RLN)
                               for long-term tone

REINNERVATION PROCEDURES (Related to Thyroplasty)

• Ansa cervicalis to RLN anastomosis (Crumley technique) - prevents VF atrophy, maintains muscle tone
• Does NOT restore mobility (synkinesis prevents meaningful movement)
• Provides tonic innervation - improves VF bulk and position over time
• Preferred in young patients with unilateral VF paralysis
• Can be combined with Type I thyroplasty for best long-term results

COMPARISON: INJECTION LARYNGOPLASTY vs TYPE I THYROPLASTY

RECENT ADVANCES IN THYROPLASTY

1. Titanium Adjustable Vocal Implant (TAVI)

• Developed by Friedrich, Germany
• Titanium implant adjustable post-operatively via external screw mechanism
• Allows fine-tuning of medialization without reoperation
• Reviewed in [Laryngeal framework surgery - HNO 2021, PMID: 33978776]

2. Office-based Thyroplasty

• Type I thyroplasty increasingly performed as outpatient/office procedure
• Study demonstrates safety without admission in low-risk cases
• Exceptions: bilateral procedures, OSA, anticoagulation, high-risk comorbidities (Cummings, p. 1155)

3. 3D-Printed Custom Implants

• Patient-specific implants designed from CT data
• Reduces intraoperative carving time
• Precise fit to individual thyroid cartilage anatomy
• Early feasibility studies show promising results

4. Combined Medialization + Reinnervation

• Simultaneous ansa cervicalis to RLN reinnervation + Type I thyroplasty
• Provides immediate voice improvement (thyroplasty) + long-term tone (reinnervation)
• Long-term outcomes reviewed: [Torrecillas et al., Laryngoscope 2024, PMID: 38279973]

5. Infraglottal Medialization

• Novel approach targeting subglottal region to increase stiffness gradient
• Improves vocal efficiency by altering glottal aerodynamics
• [Cohen O et al., J Voice 2024, PMID: 39658427]

6. Swallowing Outcomes Data

• Systematic reviews confirm medialization thyroplasty significantly improves dysphagia in UVFP
• Meta-analysis: [Coulter M et al., Otolaryngol Head Neck Surg 2023, PMID: 35021908] - strongest evidence for swallowing benefit
• [Dhar SI et al., Dysphagia 2022, PMID: 35412149] - systematic review: medialization improves swallowing outcomes

7. Modified Montgomery Thyroplasty Under MAC Anesthesia

• Monitored anesthesia care (MAC) during thyroplasty allows better patient cooperation
• [Granell M et al., J Pers Med 2023, PMID: 36836427]

8. Autologous Temporalis Fascia Thyroplasty

• Dehydrated, rolled temporalis fascia inserted as autologous implant
• Avoids foreign body reaction
• Significant improvement in phonation time in case series

SUMMARY FLOWCHART - COMPLETE THYROPLASTY APPROACH

PHONOSURGICAL PROCEDURES
         |
         |──── Microlaryngeal procedures (excision)
         |──── Vocal fold injection
         |──── LARYNGEAL FRAMEWORK SURGERY (THYROPLASTIES)
         |──── Laryngeal reinnervation
         |──── Laryngeal relaxation procedures
         |
ISSHIKI CLASSIFICATION
         |
  ┌──────┴─────────────────────────────────────────┐
  │      │                  │                      │
Type I  Type II          Type III               Type IV
Medial  Lateral         Shortening             Elongation
ization ization         (Relaxation)           (Tensioning)
  │      │                  │                      │
  VF     VF              Lowers                 Raises
paralysis lateraliza-    pitch                  pitch
          tion
  │
  ▼
INDICATIONS:
VF paralysis, bowing, sulcus, aging
  │
PREOP ASSESSMENT:
Laryngoscopy + stroboscopy + voice analysis
  │
WINDOW:
6×10 mm (VoCoM) or 6×13 mm (Netterville)
Anterior: 5-8 mm female / 8-10 mm male from midline
Superior: at true vocal fold level
  │
IMPLANT:
Silastic / Hydroxyapatite (VoCoM) / Gore-Tex
  │
VOICE TESTING:
Awake patient - phonation during implant sizing
  │
RESULT:
Improved MPT, loudness, clarity, reduced aspiration
  │
COMPLICATIONS:
Airway obstruction (most serious), implant migration,
under-correction (10-15%), mucosal breach

KEY POINTS FOR RGUHS EXAMINATION

1. Isshiki (1974) - pioneer of modern thyroplasty; classified into 4 types
2. Type I = medialization, Type II = lateralization, Type III = shortening, Type IV = elongation/tensioning
3. Local anesthesia is critical - awake patient provides voice feedback
4. Window placed at TRUE VOCAL FOLD level (inferior half of thyroid cartilage)
5. Most common error = window too high → displaces false cord
6. Overcorrection advocated by Isshiki (edema resolves post-op, voice may deteriorate)
7. Complications: airway obstruction (most serious), under-correction (10-15%), implant migration
8. Arytenoid adduction needed when posterior gap is large
9. Reinnervation prevents atrophy and improves long-term outcome
10. Recent advances: TAVI, 3D implants, combined reinnervation + thyroplasty, swallowing outcomes data

REFERENCES / SOURCE TEXTS

• Cummings Otolaryngology Head and Neck Surgery (6th Ed.), Chapter 62 - Medialization Thyroplasty, pp. 1155-1161
• Scott-Brown's Otorhinolaryngology Head & Neck Surgery (8th Ed.), Chapter 67 - Laryngeal Framework Surgery, pp. 1033-1035
• Dhingra PL, Dhingra S. Diseases of Ear, Nose and Throat & Head and Neck Surgery - Chapter on Phonosurgery
• Hazarika P. Textbook of ENT & Head and Neck Surgery - Laryngeal Framework Surgery section
• Stell & Maran's Head and Neck Surgery - Phonosurgery chapter
• Zakir Hussain. ENT Essentials - Thyroplasty overview
• Isshiki N, Taira T, Kojima H et al. Recent modifications in thyroplasty type I. Ann Otol Rhinol Laryngol 98:777, 1989
• Isshiki N, Tanabe M, Sawada M. Arytenoid adduction for unilateral vocal cord paralysis. Arch Otolaryngol 104:555, 1978
• Coulter M et al. (2023). Dysphagia Outcomes Following Surgical Management of UVFI: Systematic Review and Meta-analysis. Otolaryngol Head Neck Surg [PMID: 35021908]
• Dhar SI et al. (2022). Does Medialization Improve Swallowing in UVFP? Systematic Review. Dysphagia [PMID: 35412149]
• Hess M, Fleischer S (2021). Laryngeal framework surgery. HNO [PMID: 33978776]
• Granell M et al. (2023). Anesthetic Technique in Modified Montgomery Thyroplasty. J Pers Med [PMID: 36836427]
• Torrecillas VF et al. (2024). Long-Term Outcomes in Laryngeal Reinnervation. Laryngoscope [PMID: 38279973]

Quick Tip for RGUHS 50-mark answer: Structure as: Introduction (2m) → Classification/Isshiki types with diagram (10m) → Indications/Contraindications (5m) → Preop assessment (5m) → Surgical technique Type I in detail with window measurements (15m) → Complications (5m) → Other types II/III/IV + Arytenoid adduction (5m) → Recent advances (3m) = 50 marks