Thyroplasty is a laryngeal framework surgery in which the thyroid cartilage is surgically modified — through an external neck approach — to change the position, tension, or length of the vocal folds without directly manipulating the vocal fold mucosa itself. It is distinguished from injection laryngoplasty, which augments the vocal fold bulk endoscopically with a filler material rather than altering the cartilage framework, and from arytenoid adduction, which repositions the arytenoid cartilage rather than the thyroid lamina (the two are frequently combined for severe glottic gaps). The procedure is classified using the Isshiki system into four types based on mechanism: Type I (medialization — repositions a paralyzed or bowed fold medially via an implant placed through a thyroid cartilage window; the most common form, coded to CPT 31591), Type II (lateralization — widens the glottis, used for adductor spasmodic dysphonia), Type III (relaxation/shortening — lowers vocal pitch), and Type IV (elongation/tensioning, often paired with cricothyroid approximation — raises vocal pitch). The underlying pathophysiologic target is most often unilateral vocal fold paralysis or paresis from recurrent laryngeal nerve (RLN) injury (J38.01), producing glottic insufficiency with dysphonia, aspiration risk, and poor cough. Thyroplasty is always a therapeutic, pathology-driven intervention — there is no physiological (non-surgical) counterpart. It is most easily confused with laryngoplasty in general coding language: laryngoplasty is the broader CPT procedural family (which includes web repair, stenosis repair, and fracture fixation), while thyroplasty specifically denotes framework surgery via the thyroid cartilage for glottic competence or pitch change.
“shield-shaped” — refers to the thyroid cartilage, named for its resemblance to a Greek warrior’s shield; combining form denoting the thyroid cartilage (not the thyroid gland, despite the shared root)
Noun-forming surgical suffix — “surgical repair, reconstruction, or reshaping of”
The term thyroplasty was coined in the surgical literature in the 1970s (Isshiki et al., 1974) to describe cartilage-framework surgery of the larynx, built directly from the Greek combining form thyreo- (“shield,” referring to the thyroid cartilage) and the productive surgical suffix -plasty (“molding/reshaping”), already well established in terms like rhinoplasty (“nose reshaping”) and blepharoplasty (“eyelid reshaping”). Despite the shared root, thyroplasty is unrelated to the endocrine thyroid gland — the cartilage was named for its shield-like shape long before endocrinology adopted the same root for the gland that sits against it. The root thyro- also connects this term to thyroidectomy (removal of the thyroid gland — a different structure sharing the name), thyrohyoid (the membrane and muscle spanning the thyroid cartilage and hyoid bone), thyroarytenoid (the vocalis muscle, running from thyroid cartilage to arytenoid), and thyrotomy (surgical division of the thyroid cartilage, as in laryngofissure). The suffix -plasty is highly productive in surgical terminology, also appearing in arytenoidplasty, laryngoplasty, and tympanoplasty.
🔀 ALIASES / ALTERNATE TERMS
Medialization laryngoplasty(the preferred clinical and CPT-billing term for Type I thyroplasty; “laryngoplasty, medialization, unilateral” is the exact CPT 31591 descriptor)
Medialization thyroplasty(synonymous with Type I thyroplasty; used interchangeably in ENT operative notes)
Isshiki Type I / II / III / IV(classification-based naming convention identifying the surgical mechanism — medialization, lateralization, shortening, or lengthening, respectively)
Laryngeal framework surgery(umbrella clinical term encompassing all forms of thyroplasty; distinguishes cartilage-framework procedures from injection-based or neural procedures)
Vocal fold/cord medialization(functional description of the Type I procedure’s goal, often used in documentation and patient-facing materials)
Montgomery thyroplasty(eponymous variant using a standardized silicone implant system, typically performed under local anesthesia with intraoperative voice monitoring)
Gore-Tex thyroplasty(technique-specific term naming the ePTFE ribbon implant material used for medialization; distinct from silastic/silicone implant techniques)
🔗 RELATED TERMS
Injection laryngoplasty — an alternative, less invasive treatment for the same underlying pathology (glottic insufficiency); augments the vocal fold via percutaneous or endoscopic injection of a bulking agent rather than modifying the cartilage framework; billed under a distinct CPT family (31570, 31571) rather than the laryngoplasty/thyroplasty codes.
Arytenoid adduction — a companion or alternative procedure that rotates and repositions the arytenoid cartilage to close a posterior glottic gap; frequently performed at the same operative session as Type I thyroplasty for larger glottic defects.
Laryngeal reinnervation — a distinct surgical approach (e.g., ansa cervicalis–to–recurrent laryngeal nerve neurorrhaphy) that restores neuromuscular function rather than statically repositioning the fold; coded separately under 31590.
Vocal fold paralysis — the primary indication for Type I thyroplasty; complete loss of vocal fold mobility from RLN or vagus nerve injury (J38.01 unilateral, J38.02 bilateral).
Vocal fold paresis — a partial, incomplete form of vocal fold immobility; may also be treated with thyroplasty when symptomatic, though often trialed with injection augmentation first.
Glottic insufficiency — the functional consequence common to both paralysis and paresis — incomplete vocal fold closure during phonation, causing breathy dysphonia and aspiration risk; the core indication thyroplasty is designed to correct.
Spasmodic dysphonia — a laryngeal dystonia treated with Type II (lateralizing) thyroplasty in select surgical candidates, distinguishing this thyroplasty subtype’s mechanism (widening, not narrowing, the glottis) from Type I.
Recurrent laryngeal nerve injury — the most common etiology of unilateral vocal fold paralysis prompting thyroplasty; commonly iatrogenic (thyroidectomy, cardiothoracic surgery), idiopathic, or malignancy-related.
Laryngofissure — a broader thyrotomy approach (splitting the thyroid cartilage in the midline) used for laryngeal stenosis or reconstruction; anatomically related but a different procedure class than framework thyroplasty.
Cricothyroid approximation — the companion maneuver for Type IV (pitch-elevating) thyroplasty, narrowing the cricothyroid space to increase vocal fold tension.
Videostroboscopy — the primary diagnostic tool used pre- and post-operatively to assess vocal fold mobility, glottic closure pattern, and mucosal wave, guiding surgical candidacy and outcome assessment.
Unlisted procedure, larynx (used for Type II/III/IV thyroplasty, revision thyroplasty, and Montgomery-technique variants that lack a dedicated CPT code — per AAO-HNS coding guidance)
Append to indicate laterality of the vocal fold treated (31591 is inherently unilateral, so laterality modifiers support medical necessity and prevent bilateral-billing edits)
Bilateral procedure — rarely applicable to thyroplasty itself (nearly always unilateral), but relevant if bilateral arytenoid or combined procedures are staged
Distinct procedural service — needed when thyroplasty (31591) is billed with arytenoid adduction or another laryngeal procedure at the same session to override NCCI bundling edits, provided the procedures are separately identifiable
⚠️ Coding Note: CPT 31591 already specifies “unilateral,” so no separate laterality add-on code exists — capture right/left in the diagnosis-linked documentation and via -LT/-RT modifiers rather than code selection alone. Sequencing: report the underlying vocal fold paralysis code (J38.01/J38.02) as the primary diagnosis driving medical necessity; only add an etiology code (e.g., G52.2) when the operative or clinical documentation explicitly links the paralysis to vagus/RLN nerve injury — do not infer etiology from surgical history alone. A common inpatient profee undercoding trap: when thyroplasty is performed for iatrogenic RLN injury following a same-admission or recent thyroidectomy, query the physician to confirm whether the paralysis should be captured as an intraoperative/postprocedural complication versus an unrelated new diagnosis, since this materially affects code selection and MS-DRG assignment. Watch for NCCI bundling between 31591 and concurrently performed arytenoid adduction or injection laryngoplasty at the same encounter — modifier -59 (or -XS, where payer-preferred) is typically required to unbundle when both are separately documented and medically necessary. Payers frequently require prior authorization and implant-specific documentation (device type, e.g., Gore-Tex vs. silastic) for facility billing of the supply component.