Thyroplasty - 10 Marks Answer (MS ENT)

Definition

Isshiki Classification of Thyroplasty (1974)

Type I Thyroplasty - Medialization (Most Clinically Important)

Indications

• Unilateral vocal fold paralysis (most common indication)
• Vocal fold bowing due to presbylaryngis (aging)
• Cricothyroid joint fixation
• Sulcus vocalis
• Soft tissue defects after excision of laryngeal pathology
• Aspiration due to glottic incompetence
• Palliative management in malignancy with vocal fold paralysis

Advantages Over Vocal Fold Injection

1. Performed under local anesthesia - allows real-time voice assessment during surgery
2. Patient positioning is more anatomic, enabling better intraoperative evaluation
3. Potentially reversible (implant can be removed/revised)
4. Prosthesis placed lateral to inner perichondrium - preserves structural integrity of vocal fold, allowing effective pre-phonatory gap closure and decreased oscillation threshold
5. Can be performed as an outpatient procedure in most cases

Disadvantages

1. Open surgical procedure (neck incision)
2. Technically more demanding than injection
3. Limited ability to close the posterior glottis

Surgical Technique (Type I)

1. Position: Supine. Local anesthesia subcutaneously over ipsilateral thyroid lamina
2. Incision: 5 cm paramedian horizontal skin incision over the middle of thyroid lamina
3. Exposure: Platysma divided; subplatysmal flaps elevated; strap muscles split in midline and retracted laterally, preserving outer perichondrium
4. Window creation: Cartilage window outlined - measures 6 mm (vertical) x 10 mm (horizontal) for VoCoM system. The anterior edge is placed 5-8 mm posterior to the ventral midline in women, 8-10 mm in men. The superior aspect at the level of the true vocal fold (landmark: midpoint between inferior thyroid border and thyroid notch)
5. Inner perichondrium elevation: Elevated circumferentially with a laryngeal elevator to create a pocket for the implant
6. Sizing: Sizing templates (3-8 mm displacement) inserted through the window and rotated 90 degrees with bevel directed superiorly. Patient is asked to phonate while template is positioned - optimal position determined intraoperatively
7. Implant placement: Final implant (Silastic, Gore-Tex, or hydroxyapatite) placed and secured with a shim. Suture through implant neck may be tied over a titanium plate for security if needed
8. Closure: Small suction drain placed deep to strap muscles; strap muscles and platysma closed in layers

Implant Materials Used

• Silastic (Silicone) - traditional, most widely used
• Gore-Tex (expanded PTFE) - flexible, placed via standard fenestra or inferior approach
• Hydroxyapatite - prefabricated system (VoCoM); comes in 3-7 mm displacement implants with offset shims
• Titanium - used for securing implants

Combined Procedures

• Arytenoid adduction: For posterior glottal gap, poor arytenoid rotation, or when vocal fold level difference is significant. Animal studies show combined arytenoid adduction + thyroplasty gives superior acoustic and aerodynamic results over thyroplasty alone
• Laryngeal reinnervation: For long-term maintenance of vocal fold tone and bulk

Complications of Type I Thyroplasty

1. Failure to achieve adequate medialization - most common
2. Penetration of endolaryngeal mucosa - intraoperative complication
3. Airway obstruction - from hematoma, edema, or overmediation; most feared immediate complication
4. Wound infection and chondritis
5. Implant migration or extrusion
6. Overcorrection - rare
7. Revision thyroplasty may be required in cases of inadequate result; combined with injectable fat, Cymetra, or arytenoid adduction as alternatives

Type IV Thyroplasty (Cricothyroid Approximation) - High Yield for Exams

• Approximates cricoid to thyroid cartilage anteriorly
• Increases vocal fold tension and raises pitch
• Used in male-to-female transgender voice feminization
• Can cause dysphagia if cricoid is rotated excessively

Key Exam Points

• Isshiki classified thyroplasty in 1974 (published 1975 in Acta Otolaryngologica)
• Type I = lateral compression = medialization = most performed
• Performed under local anesthesia - hallmark advantage (allows patient to phonate during procedure)
• Implant placed between thyroid cartilage and inner perichondrium (lateral to inner perichondrium)
• Window position: anterior edge 5-8 mm (female) / 8-10 mm (male) from midline
• Level of true fold = midpoint of distance from inferior thyroid border to thyroid notch
• Potentially reversible - distinguishes it from permanent injection
• Combined with arytenoid adduction for posterior gap