Crystal's Coder Hub🫁 CPT 31591 — Laryngoplasty, Medialization, Unilateral
Quick Reference
wRVU: 9.20 | Global Period: 090 (90 days) | Assistant Payable: ✅ Yes | Bilateral Indicator: 1 — Unilateral code; bilateral requires modifier -50
📋 Clinical Description
CPT 31591 describes a unilateral open medialization laryngoplasty — commonly called Type I thyroplasty, medialization thyroplasty, or framework surgery — the gold-standard definitive surgical treatment for unilateral vocal cord paralysis or significant vocal cord paresis/atrophy causing dysphonia, aspiration, or dysphagia. The procedure is performed under local anesthesia with sedation (most commonly) or under general anesthesia, through a 4-6 cm horizontal external neck incision centered over the thyroid cartilage. The thyroid ala on the affected side is exposed, and a precisely sized rectangular window is created in the thyroid cartilage lamina at the level of the membranous vocal cord. A carving guide or direct measurement determines the implant dimensions. A carved implant — most commonly silastic (silicone elastomer block), Gore-Tex (expanded polytetrafluoroethylene), a prefabricated titanium vocal fold medialization prosthesis (e.g., Montgomery or Netterville titanium system), or other biocompatible synthetic material — is inserted through the cartilage window into the paraglottic space lateral to the inner perichondrium and medial to the vocal cord musculature, physically displacing the vocal cord medially toward the midline.
The hallmark and therapeutic advantage of awake medialization thyroplasty (the dominant technique) is that the patient is conscious and able to phonate during the procedure — the surgeon asks the patient to count, sustain vowel sounds, and speak while adjusting implant size and position in real time, achieving optimal glottic closure before the wound is closed. This intraoperative voice feedback loop is what distinguishes 31591 from injection augmentation (31574) — the open framework approach allows precise, titrated, adjustable positioning under direct auditory and endoscopic feedback.
31591 was added to the CPT code set in 2017 as part of a major laryngology code restructuring, replacing the previously used 31599 (unlisted procedure, larynx) that providers had been using for medialization thyroplasty for over two decades. Per the AAO-HNS CPT Assistant bulletin (2017), 31591 specifically describes the open framework approach — an external neck incision with implant insertion through a thyroid cartilage window. Endoscopic laryngoplasty approaches do NOT use 31591 — per AAO-HNS CPT for ENT guidance, endoscopic laryngoplasty is reported with 31599 (unlisted larynx code).
This procedure may be performed in the following clinical contexts:
- Unilateral vocal cord paralysis (UVCP) from recurrent laryngeal nerve (RLN) injury — The most common indication; RLN injury from thyroidectomy, anterior cervical spine surgery, esophagectomy, cardiac/thoracic surgery (left RLN injury from aortic arch procedures, PDA ligation), cervical trauma, or skull base surgery; document the specific etiology of the RLN injury and the nerve laterality.
- Unilateral vocal cord paralysis of unknown etiology (idiopathic) — When the etiology is not identified after full workup (CT chest/neck, MRI, laryngoscopy, thyroid evaluation, neurology consult); typically after 9-12 months of observation for spontaneous recovery; document the workup performed and the duration of observation before surgical intervention.
- Vocal cord paralysis from neurologic disease or skull base tumor — Vagal nerve palsy from jugular foramen or skull base lesion, posterior fossa tumor, or peripheral neuropathy; document the underlying neurologic etiology and its contribution to the vocal cord paralysis.
- Vocal cord atrophy or bowing without frank paralysis (presbylaryngis) — Significant vocal cord atrophy or bowing causing dysphonia, voice fatigue, and/or aspiration in elderly patients or those with neurologic disease causing vocal cord paresis; medialization closes the glottic gap; document the specific vocal cord deformity and the functional impairment.
- Post-hemilaryngectomy or partial laryngectomy glottic insufficiency — After partial laryngectomy leaving a vocal cord remnant that does not adequately close, medialization laryngoplasty may be performed to restore phonatory and swallowing function; document the prior surgical history and the current glottic anatomy.
- Failed or insufficient injection augmentation — When prior injection augmentation (31574) provided inadequate or temporary improvement and the patient requires a permanent framework procedure; document the prior injection history, materials used, and the rationale for escalation to open framework surgery.
🔬 Implant Types and Techniques
| Implant / Technique | Material | Characteristics | Coding Notes |
|---|---|---|---|
| Silastic Block (Silicone Elastomer) | Medical-grade silicone elastomer | Hand-carved to custom fit using carving guides; most commonly used; adjustable; removable; excellent long-term biocompatibility | All implant types are captured by 31591 — the code does not distinguish by implant material; the implant itself may be separately reportable under HCPCS code C1878 (material for vocal cord medialization, synthetic, implantable) for facility/ASC billing; confirm payer coverage |
| Gore-Tex (ePTFE) | Expanded polytetrafluoroethylene | Ribbon form; layered strips placed through the cartilage window; allows fine adjustment; very popular in contemporary laryngology practice | Same 31591 regardless of Gore-Tex technique; Gore-Tex strips may be reportable under C1878 or facility supply codes — confirm payer |
| Titanium Vocal Fold Medialization Implant (Montgomery, Netterville System) | Titanium alloy with or without silicone tip | Prefabricated sizing system; titanium anchor secured in the cartilage window; available in standardized sizes for male and female larynges; reduces carving time | Same 31591 regardless of titanium system used; the device may be separately reportable under facility device codes; confirm payer policy for implant billing |
| Awake Procedure (Local Anesthesia + Sedation) | N/A — technique, not implant | Patient awake during implant placement; able to phonate for real-time voice feedback to guide optimal implant position; the dominant technique for medialization thyroplasty | Awake vs. general anesthesia does NOT change the CPT code; 31591 is reported regardless of anesthesia technique; if performed under general anesthesia, the anesthesia provider bills under the appropriate anesthesia CPT code |
| General Anesthesia Technique | N/A — technique | Used in patients who cannot tolerate awake procedure; surgeon relies on laryngoscopic visualization (rigid or flexible) rather than voice feedback for implant position assessment | Same 31591; document the anesthesia type in the operative note; loss of awake voice feedback is a known limitation and should be documented |
31591 Is OPEN Framework Surgery Only — NOT Injection Augmentation
Per AAO-HNS CPT for ENT guidance and the 2017 CPT code restructuring:
- 31591 = Open medialization laryngoplasty via external neck incision + thyroid cartilage window + implant insertion → the framework/Type I thyroplasty approach
- 31574 = Flexible laryngoscopy with injection(s) for augmentation, unilateral → injection augmentation of the vocal cord with a bulking agent (PROLARYN, Radiesse, fat, Cymetra) via percutaneous or transoral injection; NO external incision; NO thyroid cartilage window; NOT reported with 31591
- 31571 = Direct operative laryngoscopy with injection for augmentation, with operating microscope/telescope → injection augmentation via direct suspension laryngoscopy approach; NOT the open framework approach
- 31599 = Unlisted procedure, larynx → used for endoscopic laryngoplasty (scope-guided framework-type procedure without external incision) per AAO-HNS guidance
Reporting 31591 for an injection-only vocal cord augmentation is incorrect. The external neck incision and thyroid cartilage window are the defining technical elements that distinguish 31591 from injection codes.
✅ Procedure Includes
- Pre-operative flexible laryngoscopy correlation on the same date — typically bundled; if performed as a separate session before the surgical day, separately reportable under 31575 with appropriate documentation
- Awake sedation monitoring (if local anesthesia technique) or general anesthesia (separately billable by the anesthesia provider)
- External neck incision and exposure of the thyroid ala on the affected side
- Thyroid cartilage window creation — measurement, marking, and precise cartilage removal to the dimensions of the planned implant
- Dissection and elevation of the inner perichondrium to create the implant pocket in the paraglottic space
- Implant carving (silastic) or selection (titanium system) and trial placement with intraoperative voice feedback assessment (awake technique) or endoscopic visualization (general anesthesia technique)
- Final implant placement and securing — cartilage perichondrium flap replacement, implant stabilization
- Wound closure — platysma, subcutaneous tissue, and skin in layers
- Intraoperative flexible laryngoscopy for glottic closure assessment — included when performed as part of the same operative session for implant position evaluation
- Post-operative airway monitoring and dietary modification instructions (bundled in the 90-day global)
❌ Excludes / Do Not Report Together
| Code | Description | Relationship to 31591 |
|---|---|---|
| 31574 | Laryngoscopy, flexible; with injection(s) for augmentation, unilateral | Injection augmentation of the vocal cord — a completely different procedural approach from 31591; not reportable together at the same session for the same vocal cord; 31574 is the injection/bulking agent approach; 31591 is the open framework approach; if injection and open framework procedures are performed at the same session for distinct vocal cord pathology, evaluate NCCI edits carefully |
| 31571 | Laryngoscopy, direct, operative, with injection(s) for augmentation; with operating microscope or telescope | Direct operative laryngoscopy with vocal cord injection — distinct from the open framework approach; not reported alongside 31591 for the same vocal cord at the same session |
| 31560 | Laryngoscopy, direct, operative, with arytenoidectomy | Separately reportable when arytenoid adduction (technically different from arytenoidectomy but sometimes coded similarly — see arytenoid adduction note below) is performed concurrently with medialization thyroplasty; apply modifier -51 on the lower-valued code; the operative note must distinctly document each procedure |
| 31592 | Cricotracheal resection | Separate laryngeal framework procedure — resection of the cricotracheal segment for subglottic stenosis; not related to medialization; separately reportable when performed at the same session for a distinct indication; apply modifier -51 |
| 31575 | Laryngoscopy, flexible; diagnostic | Post-operative or concurrent flexible laryngoscopy for implant position assessment — when performed as a distinct diagnostic evaluation at a separate encounter, 31575 is separately reportable; when performed intraoperatively as part of the same operative session for implant guidance, it is generally bundled into 31591 |
| 31579 | Laryngoscopy, flexible or rigid telescopic, with stroboscopy | Pre-operative or post-operative stroboscopy — separately reportable at a distinct encounter; bundled if performed same session as 31591 without independent clinical documentation of a separately identifiable diagnostic purpose |
| E/M codes (992xx / 920xx) | Office or hospital visit, any level | Same-date E/M is bundled in the 90-day global; modifier -57 on the E/M code (NOT 31591) is required when the same-day pre-operative E/M represents the decision to perform this major surgical procedure (90-day global); modifier -25 is used for significant, separately identifiable E/M services NOT representing the decision for the 31591 surgery |
Arytenoid Adduction — Critical Bundling Issue
Arytenoid adduction is commonly performed concurrently with medialization thyroplasty (31591) for patients with a large posterior glottic gap, a fixed arytenoid, or a significantly lateralized vocal cord. There is no dedicated CPT code specifically for “arytenoid adduction” as a standalone procedure. The most commonly used code alongside 31591 for concurrent arytenoid adduction is 31561 (laryngoscopy, direct, operative, with arytenoidectomy; with operating microscope or telescope) or 31560 (without microscope) — though this is a known coding gray area since arytenoid adduction is technically not the same as arytenoidectomy. Some providers use 31599 (unlisted larynx code) for the arytenoid adduction component. Verify current NCCI edit status for 31591 + 31560/31561 before submitting, and confirm your MAC’s preferred coding approach for concurrent arytenoid adduction. Apply modifier -51 to the lower-valued code when both are separately reported.
🌳 Code Tree — Surgery: Respiratory System — Repair Procedures on the Larynx
CPT 31551-31599 Repair Procedures on the Larynx / Laryngeal Framework Surgery
│
LARYNGEAL STENOSIS — OPEN REPAIR:
├── 31551 Laryngoplasty; for laryngeal stenosis, with graft, without indwelling stent placement (Global: 090)
├── 31552 Laryngoplasty; for laryngeal stenosis, with graft, with indwelling stent placement (Global: 090)
├── 31553 Laryngoplasty; for laryngeal stenosis, without graft, without indwelling stent placement (Global: 090)
├── 31554 Laryngoplasty; for laryngeal stenosis, without graft, with indwelling stent placement (Global: 090)
│
LARYNGOTRACHEAL RECONSTRUCTION / CRICOTRACHEAL:
├── 31580 Laryngoplasty; for anterior web formation, with epiglottic flap (Global: 090)
├── 31584 Laryngoplasty; with open reduction of fracture (Global: 090)
├── 31587 Laryngoplasty, cricotracheal resection (see 31592)
├── 31590 Laryngoplasty, arytenoid abduction, external approach (Global: 090)
├── 31592 Cricotracheal resection (Global: 090)
│
MEDIALIZATION / FRAMEWORK SURGERY:
└── ▶▶ 31591 ◀◀ Laryngoplasty, medialization, unilateral ← YOU ARE HERE (Global: 090)
│
INJECTION AUGMENTATION (NOT Framework — Different Approach):
├── 31574 Laryngoscopy, flexible; with injection(s) for augmentation (eg, percutaneous, transoral), unilateral (Global: 000)
├── 31570 Laryngoscopy, direct, with injection into vocal cord(s), therapeutic (Global: 010)
└── 31571 Laryngoscopy, direct, with injection(s) for augmentation; with operating microscope or telescope (Global: 010)
│
UNLISTED:
└── 31599 Unlisted procedure, larynx — used for endoscopic laryngoplasty and arytenoid adduction per AAO-HNS
💰 RVU & Reimbursement Profile
| Component | Value |
|---|---|
| Work RVU (wRVU) | 9.20 (verify against current CMS MPFS RVU26A; subject to 2026 -2.5% efficiency adjustment on non-time-based procedural services — verify final adjusted value) |
| Non-Facility PE RVU | ~9.62 (verify against CMS RVU26A) |
| Malpractice RVU | ~0.95 |
| Non-Facility Total RVU | ~19.77 (verify against CMS RVU26A) |
| Facility Total RVU | ~12.45 (verify against CMS RVU26A; most 31591 claims are facility-based — outpatient hospital or ASC) |
| Estimated Medicare Facility Payment (2026) | ~33.4009 × facility total RVU; actual payment varies by locality GPCI — verify)* |
| Global Period | 090 (90 days) |
| Bilateral Indicator | 1 — UNILATERAL CODE — Standard bilateral reduction rules apply; when bilateral medialization laryngoplasty is performed at the same session (rare due to airway concerns), report with modifier -50 (or -RT/-LT per MAC format); bilateral payment = 150% of the unilateral rate; NEVER report two units of 31591 without a bilateral modifier |
| Assistant Surgeon | ✅ Payable — modifier -80 or -82; document medical necessity; commonly appropriate for complex cases, revision surgery, concurrent arytenoid adduction, or patients with prior neck surgery/radiation |
| Co-Surgeon | ✅ Potentially applicable — modifier -62 when two surgeons of different specialties perform distinct portions concurrently — e.g., in complex skull base or thoracic cases where the etiology of the RLN injury is being simultaneously addressed |
| Team Surgery | ❌ Not typically applicable for isolated 31591 |
| PC/TC Split | ❌ No — Procedure code only (Indicator 0) |
| Modifier -51 Exempt | No — Subject to multiple procedure reduction rules when billed with other surgical procedures at the same session |
| Anesthesia | Commonly performed under local anesthesia + monitored anesthesia care (MAC) — the awake technique enables real-time voice feedback; MAC anesthesia is separately billable by the anesthesia provider; if performed under general anesthesia, the anesthesia provider bills under CPT 00320 (anesthesia for all procedures on larynx and trachea, patients ≥ 1 year); the surgeon does NOT separately bill for anesthesia |
| HCPCS Device Code | C1878 — Material for vocal cord medialization, synthetic (implantable) — reportable by the facility (not the surgeon) for the medialization implant (silastic, Gore-Tex, titanium prosthesis) in the ASC or outpatient hospital setting; confirm payer coverage and whether the device is separately reimbursed or bundled into the facility payment for 31591 at your specific MAC/payer |
31591 at 9.20 wRVU carries dramatically higher value than vocal cord injection augmentation 31574 at approximately 1.88 wRVU — reflecting the substantially greater surgical complexity, operative time, external incision, cartilage framework manipulation, and awake intraoperative management involved in open medialization thyroplasty. From a revenue and provider production standpoint, 31591 is one of the highest-value single laryngeal procedures in the otolaryngology CPT code set. Accurate documentation of the open framework approach (external neck incision, thyroid cartilage window, implant insertion) is essential to support 31591 over a lower-value injection augmentation code.
🏷️ Modifier Reference
| Modifier | Name | When to Apply |
|---|---|---|
| -50 | Bilateral Procedure | Required when bilateral medialization laryngoplasty is performed at the same session; 31591 is unilateral — bilateral requires -50; clinically rare due to airway safety concerns (bilateral vocal cord medialization carries risk of airway compromise); document specific bilateral clinical justification; confirm MAC billing format preference (-50 single line vs. -RT/-LT two lines); payment = 150% of the unilateral rate |
| -RT | Right Side | Right unilateral medialization thyroplasty — apply when documenting right-side surgery; use when billing bilateral as two separate line items per MAC format, or for single-side right |
| -LT | Left Side | Left unilateral medialization thyroplasty — use for bilateral line-item billing or single-side left documentation |
| -22 | Increased Procedural Services | When the procedure required substantially greater work than typical — prior neck surgery or radiation creating scarred/fibrotic tissue planes, calcified thyroid cartilage requiring powered instrumentation or drilling to create the window, revision implant surgery (implant exchange or repositioning), markedly prolonged operative time; document specific complexity factors in the operative note; attach a cover letter to the claim |
| -25 | Significant, Separately Identifiable E/M | Applied to the E/M code — NOT 31591 — when a significant, separately identifiable evaluation is performed same date that does NOT represent the decision to perform 31591; the 90-day global bundles post-operative E/M visits |
| -57 | Decision for Surgery | Applied to the E/M code (NOT 31591) when the same-date pre-operative E/M visit represents the decision to perform this major surgical procedure (90-day global); -57 on the E/M code opens separate payment for that evaluation despite the global; required for same-day pre-operative office visit + 31591 billing |
| -24 | Unrelated E/M During Postoperative Period | Applied to the E/M code when the patient returns within the 90-day global window for a condition unrelated to the medialization thyroplasty; document the unrelated nature explicitly in the medical record |
| -51 | Multiple Procedures | When 31591 is performed alongside other separately reportable surgical procedures at the same session — e.g., concurrent arytenoid adduction (31560/31561), cricothyroid subluxation, or tracheostomy; apply -51 to the lower-valued code |
| -52 | Reduced Services | Procedure partially completed — e.g., thyroid cartilage window created but implant placement unsuccessful due to inadequate cartilage dimensions, patient intolerance of awake procedure, or abandoned due to intraoperative complications; document the specific extent of the procedure completed |
| -54 | Surgical Care Only | Surgeon performs 31591 but post-operative care (90-day global) is transferred to another provider; the global is split; both providers coordinate claim submission |
| -55 | Postoperative Management Only | Provider assuming post-operative care during the 90-day global after surgery was performed by a different surgeon |
| -57 | Decision for Surgery | See above — on the E/M code, not 31591 |
| -58 | Staged or Related Procedure | Planned staged procedure during the 90-day global — e.g., staged second-side medialization, planned arytenoid adduction staged after confirming first-side implant position, or planned post-medialization vocal therapy evaluation in the OR; must be documented as planned in the original operative report; opens a new global period |
| -59 | Distinct Procedural Service | When 31591 is billed alongside a procedure at a genuinely distinct anatomic site that payers may bundle |
| -XS | Separate Structure | Preferred over -59 when the distinct service involves a clearly separate anatomic structure |
| -76 | Repeat Procedure by Same Physician | Revision medialization thyroplasty (implant exchange, repositioning, augmentation of an existing implant) by the same surgeon; document the specific clinical indication for the revision — implant migration, implant extrusion, under-correction, over-correction with airway compromise |
| -77 | Repeat Procedure by Different Physician | Revision thyroplasty by a different surgeon |
| -78 | Unplanned Return to OR | Unplanned return during the 90-day global — e.g., implant migration causing acute airway compromise, post-operative hematoma requiring surgical drainage, wound infection requiring debridement; document the unplanned nature and the complication driving the return |
| -79 | Unrelated Procedure During Postoperative Period | Unrelated surgical procedure during the 90-day global window |
| -80 | Assistant Surgeon | When an assistant surgeon participates — document medical necessity; appropriate for complex cases with prior neck surgery, radiation fibrosis, or concurrent arytenoid adduction |
🩺 Common ICD-10-CM Pairings
Vocal Cord Paralysis / Paresis — Primary Diagnoses
| ICD-10 Code | Description | HCC? | Clinical Notes |
|---|---|---|---|
| J38.01 | Paralysis of vocal cords and larynx, unilateral | ❌ No | Most commonly paired primary diagnosis for 31591 — unilateral vocal cord paralysis (UVCP) is the primary indication for medialization thyroplasty; document the affected side (right vs. left), the etiology (post-thyroidectomy, idiopathic, vagal, etc.), and the duration; J38.01 does not specify the side or etiology — document these in the clinical record even though the ICD-10 code does not capture them |
| J38.02 | Paralysis of vocal cords and larynx, bilateral | ❌ No | Use for bilateral vocal cord paralysis — less commonly treated with bilateral 31591 due to airway risk; when bilateral medialization is performed (rare), J38.02 is the primary diagnosis; confirm airway safety documentation |
| J38.3 | Other diseases of vocal cords | ❌ No | Use for vocal cord paresis (incomplete/partial paralysis), vocal cord atrophy, vocal cord bowing (presbylaryngis), or Reinke’s edema not covered by more specific codes; when medialization is performed for atrophy/bowing rather than frank paralysis, J38.3 is appropriate; document the specific finding (atrophy, bowing, paresis) in the clinical record |
Etiologic / Underlying Diagnoses
| ICD-10 Code | Description | HCC? | Clinical Notes |
|---|---|---|---|
| G52.2 | Disorders of vagus nerve | ❌ No | Use as secondary diagnosis when unilateral vocal cord paralysis is caused by a vagal nerve injury or disorder — e.g., vagal schwannoma, vagal neuropathy, or idiopathic vagal palsy; codes the neurologic mechanism; assigned secondary to J38.01 unless the neurologic disorder is the principal diagnosis of the admission |
| Z98.89 | Other specified postprocedural states | ❌ No | Use as secondary diagnosis when the vocal cord paralysis is a post-surgical sequela — post-thyroidectomy RLN injury, post-esophagectomy, post-cardiac surgery, post-anterior cervical discectomy; documents the post-procedural context; code sequencing: J38.01 as principal diagnosis, Z98.89 as secondary |
| S14.2XXA | Injury of nerve root of cervical spine, initial encounter | ❌ No | Use for vocal cord paralysis secondary to cervical nerve root injury — post-surgical or traumatic; 7th character A = initial encounter; document the specific nerve and mechanism |
| C32.0 | Malignant neoplasm of glottis | ✅ HCC | Use when vocal cord paralysis is secondary to a laryngeal malignancy — code the malignancy as the principal/primary diagnosis with J38.01 as secondary; per ICD-10-CM sequencing guidelines, code the causative condition first when a paralysis code is listed as “in diseases classified elsewhere” |
Functional Symptoms Supporting Medical Necessity
| ICD-10 Code | Description | HCC? | Clinical Notes |
|---|---|---|---|
| R49.0 | Dysphonia | ❌ No | Use as primary or secondary diagnosis when dysphonia (voice change, hoarseness, breathy voice) is the presenting symptom driving the 31591 surgery — the voice change is the primary functional complaint; assign as secondary when J38.01 or J38.3 is the principal diagnosis; R49.0 supports medical necessity for voice-directed intervention |
| R13.10 | Dysphagia, unspecified | ❌ No | Use as secondary diagnosis when aspiration or dysphagia accompanies the vocal cord paralysis — impaired glottic closure causes aspiration of liquids and dysphagia; documents the functional swallowing impairment and supports medical necessity for surgical glottic closure improvement; when the pattern is characterized (oropharyngeal, pharyngoesophageal), use R13.19 for greater specificity |
| R13.19 | Other dysphagia | ❌ No | Use when the specific dysphagia pattern (oropharyngeal, neurogenic) is documented — more specific than R13.10; preferred when the swallowing study characterizes the dysphagia type |
Neurologic Etiologies
| ICD-10 Code | Description | HCC? | Clinical Notes |
|---|---|---|---|
| G12.21 | Amyotrophic lateral sclerosis | ✅ HCC | Use as the etiologic secondary diagnosis when vocal cord paresis is a manifestation of ALS-related bulbar palsy; G12.21 is an HCC code with significant risk adjustment weight; ALS with bulbar palsy may present with bilateral vocal cord dysfunction — confirm which code most accurately captures the ALS subtype from the treating neurologist’s documentation |
| G35.A | Multiple sclerosis | ✅ HCC | Use as secondary diagnosis when vocal cord paresis or paralysis is attributable to demyelinating disease (MS); document from the treating neurologist’s assessment; G35.D is an HCC code |
Implant-Related Diagnoses (Revision Cases)
| ICD-10 Code | Description | HCC? | Clinical Notes |
|---|---|---|---|
| T85.398A | Other mechanical complication of other implanted prosthetic devices, implants and grafts, initial encounter | ❌ No | Use as principal diagnosis when 31591 is performed as a revision procedure due to implant migration, implant extrusion, implant malposition, or implant failure from a prior medialization thyroplasty; the 7th character A = initial encounter for the complication; sequence as principal when the complication is the reason for the revision surgery |
ICD-10-CM Sequencing: Paralysis vs. Etiology
When coding 31591 encounters, the sequencing question is whether the paralysis (J38.01) or the underlying etiology (e.g., C32.0 malignancy, G52.2 vagus nerve disorder) is the principal diagnosis. For outpatient/profee coding, the condition chiefly responsible for the visit (the vocal cord paralysis requiring the surgical procedure) is typically sequenced first. For inpatient facility coding, the principal diagnosis is the condition established after study to be chiefly responsible for the admission — if the admission is specifically for the medialization thyroplasty, J38.01 is the principal diagnosis with the etiology sequenced as secondary. If the patient is admitted for the underlying condition (e.g., laryngeal cancer requiring combined resection and reconstruction) and 31591 is performed as a concurrent procedure, the malignancy is the principal diagnosis. Query the treating physician when sequencing is ambiguous.
🏥 MS-DRG Considerations (Inpatient)
Inpatient Coding Reminder
CPT 31591 maps to MDC 03 (Diseases and Disorders of the Ear, Nose, Mouth, and Throat) for vocal cord paralysis and laryngeal repair diagnoses, grouping to DRG 133/134/135 (Other Ear, Nose, Mouth and Throat O.R. Procedure with MCC/CC/without CC/MCC). The CC/MCC tier is driven by concurrent diagnoses — the most impactful MCC diagnoses in the 31591 population include: aspiration pneumonia (J69.0 — MCC), acute respiratory failure (J96.01 — MCC), and malnutrition (E43 — MCC) in dysphagic patients with recurrent aspiration from vocal cord paralysis. CDI querying should focus on: (1) confirming the specific etiology of the vocal cord paralysis to determine if an HCC-bearing etiologic code applies; (2) documenting aspiration complications that qualify as MCC; and (3) confirming nutritional status in patients with chronic aspiration and dysphagia. When 31591 is performed concurrently with arytenoid adduction or other laryngeal framework procedures, the ICD-10-PCS codes for all procedures must be assigned for facility inpatient billing.
🔧 ICD-10-PCS Equivalents (Inpatient Facility Coding)
Note
At the inpatient facility level, 31591 is most accurately represented by ICD-10-PCS using root operation Reposition (S) — moving to its normal location, or other suitable location, all or a portion of a body part — because the fundamental surgical objective is to reposition the vocal cord medially to its functional position. However, because an implant (synthetic substitute) is inserted through the thyroid cartilage window, the Insertion (H) root operation for device placement may also be argued. ICD-10-PCS does not have a single dedicated code that perfectly captures the complete Type I thyroplasty procedure. Facility coding teams commonly use Reposition of Larynx, Open Approach (0RS70ZZ) or Reposition of Vocal Cord Right/Left, Open with Synthetic Substitute depending on the body system mapping. Confirm the ICD-10-PCS assignment with your facility’s grouper and coding team, as the exact mapping may vary by facility policy and grouper version.
| PCS Code | Full Description | Applicable Scenario |
|---|---|---|
0RQC0ZZ | Repair Larynx, Open Approach, No Device, No Qualifier | Open laryngeal repair without device — used when the PCS root operation Repair (Q) is chosen; less accurate for implant-based medialization but used by some facilities |
0RHC0JZ | Insertion of Synthetic Substitute into Larynx, Open Approach | Insertion root operation (H) — captures the implant placement component; used when the primary operative objective is characterized as device insertion (synthetic implant into the larynx via open approach) |
0RSS0JZ | Reposition Larynx with Synthetic Substitute, Open Approach | Most conceptually accurate PCS code — Reposition (S) of the larynx (vocal cord) with Synthetic Substitute (J = implant), Open Approach; captures the repositioning of the vocal cord AND the use of an implant device |
PCS Character Analysis — 0RSS0JZ (Reposition Larynx with Synthetic Substitute, Open)
| Position | Character | Value | Definition |
|---|---|---|---|
| 1 | Section | 0 | Medical and Surgical |
| 2 | Body System | R | Upper Joints (or confirm body system mapping for larynx in your grouper version — some groupers map larynx to the Respiratory System B or Mouth and Throat C body systems) |
| 3 | Root Operation | S | Reposition (moving to its normal location, or other suitable location, all or a portion of a body part — the vocal cord is repositioned medially toward its functional midline position) |
| 4 | Body Part | S | Larynx (in some PCS versions the larynx is character S; in others the vocal cord is a distinct body part — confirm in your PCS code tables) |
| 5 | Approach | 0 | Open (cutting through the skin or mucous membrane and any other body layers necessary to expose the site of the procedure — the external neck incision provides open access to the thyroid cartilage) |
| 6 | Device | J | Synthetic Substitute (the medialization implant — silastic, Gore-Tex, or titanium prosthesis — is the synthetic substitute device) |
| 7 | Qualifier | Z | No Qualifier |
ICD-10-PCS Root Operation: Reposition (S) vs. Insertion (H) vs. Repair (Q)
The correct PCS root operation for 31591 is debated in the inpatient facility coding community because the procedure achieves its therapeutic goal through repositioning the vocal cord (using an implant to push it medially) while simultaneously inserting a synthetic substitute device:
- Reposition (S) — Most conceptually accurate for the surgical objective of moving the vocal cord to midline; device (J = Synthetic Substitute) is used to achieve and maintain the repositioned position
- Insertion (H) — Appropriate when characterizing the procedure as primarily a device insertion (the implant is placed in the paraglottic space as the operative act); some facilities default to this for implant-based procedures
- Repair (Q) — Least accurate; Repair restores body part to its normal anatomic structure; medialization thyroplasty does not restore the nerve or restore normal vocal cord motion — it compensates for the paralysis with an implant; avoid Repair when Reposition with a device more accurately reflects the operative technique
- Facility coding policy should define the preferred root operation for 31591 — apply consistently across all cases and verify with your facility’s ICD-10-PCS coding expert
📝 Coding Examples
Example 1 — ASC: Awake Right Medialization Thyroplasty for Post-Thyroidectomy Vocal Cord Paralysis
Clinical Scenario: A 54-year-old female develops right unilateral vocal cord paralysis following a total thyroidectomy for papillary thyroid carcinoma 11 months ago. She presents with breathy dysphonia (MPT 4 seconds, G2R1B2A0S0) and aspiration on thin liquids on modified barium swallow study. Office flexible laryngoscopy confirms complete right true vocal cord immobility in the paramedian position with a moderate posterior glottic gap. After 11 months of observation without spontaneous recovery and failed swallowing therapy, she is scheduled for right medialization thyroplasty. The procedure is performed in the ASC under local anesthesia (1% lidocaine with epinephrine) and MAC sedation. External neck incision, right thyroid ala exposed. A 4 × 12 mm window is created in the right thyroid cartilage lamina. Silastic block hand-carved and trial-fitted; patient counts aloud — improved voice on first trial implant. Final silastic implant seated in the paraglottic space; sustained /a/ at 12 seconds, G1R0B1A0S0 on final assessment. Implant secured with perichondrial flap, wound closed in layers.
| Field | Code | Rationale |
|---|---|---|
| CPT | 31591--RT | Laryngoplasty, medialization, unilateral — right side; open framework surgery confirmed: external neck incision, thyroid cartilage window, silastic implant insertion; awake technique with voice feedback documented; -RT for right-side documentation |
| PDx | J38.01 | Paralysis of vocal cords and larynx, unilateral — right vocal cord paralysis; the primary diagnosis driving the surgical procedure |
| SDx | Z98.89 | Other specified postprocedural states — post-thyroidectomy status; documents the etiology of the RLN injury as a surgical sequela |
| SDx | R49.0 | Dysphonia — breathy dysphonia is the primary functional complaint; supports medical necessity |
| SDx | R13.10 | Dysphagia, unspecified — aspiration on thin liquids documented on modified barium swallow; supports medical necessity for glottic closure improvement |
Note
The HCPCS code C1878 (material for vocal cord medialization, synthetic, implantable) is separately reportable by the ASC facility for the silastic implant — NOT by the surgeon. The surgeon bills 31591 for the professional fee; the ASC bills 31591 for the facility fee and may separately bill C1878 for the implant device. Confirm with the ASC billing department and the payer whether C1878 is separately reimbursed or bundled into the ASC facility payment. Some payers package the implant cost into the 31591 payment and do not separately reimburse C1878.
Example 2 — Outpatient Hospital: Medialization Thyroplasty with Concurrent Arytenoid Adduction
Clinical Scenario: A 67-year-old male with left idiopathic vocal cord paralysis (duration > 24 months, no recovery on serial laryngoscopy, workup negative for malignancy) presents with severe dysphonia (MPT 2 seconds) and recurrent aspiration pneumonia. Office laryngoscopy confirms complete left true vocal cord immobility in the lateral position — a large posterior glottic gap is present consistent with a fixed lateralized arytenoid position. The laryngologist plans combined left medialization thyroplasty AND arytenoid adduction for the posterior gap. Under general anesthesia with flexible laryngoscopic monitoring, left external neck incision, left thyroid cartilage window created (4 × 10 mm), Gore-Tex strips layered to achieve medialization. Separately, left arytenoid adduction sutures placed through the muscular process of the arytenoid to adduct the arytenoid and close the posterior glottic gap — confirmed with intraoperative flexible laryngoscopy. Both procedures documented distinctly in the operative report.
| Field | Code | Rationale |
|---|---|---|
| CPT 1 | 31591--LT | Left medialization thyroplasty — open framework surgery confirmed; -LT for left-side documentation |
| CPT 2 | 31561--51--LT | Laryngoscopy, direct, operative, with arytenoidectomy; with operating microscope or telescope — used to capture the arytenoid adduction component (coding gray area — no dedicated CPT for arytenoid adduction; 31561 or 31599 per facility/payer preference); -51 on the lower-valued code; -LT for left side; confirm NCCI edit status for 31591 + 31561 before submitting; some providers use 31599 for arytenoid adduction |
| PDx | J38.01 | Paralysis of vocal cords and larynx, unilateral — left vocal cord paralysis; principal diagnosis driving the combined procedure |
| SDx | R13.10 | Dysphagia, unspecified — recurrent aspiration pneumonia from glottic incompetence; confirm whether aspiration pneumonia (J69.0) should be sequenced as a more specific secondary diagnosis |
| SDx | R49.0 | Dysphonia — severe voice impairment supporting medical necessity |
Warning
The coding for concurrent arytenoid adduction alongside 31591 is a recognized coding gray area in laryngology. The AAPC Otolaryngology Coding Alert and the AAO-HNS have both addressed this issue. When arytenoid adduction is performed as a concurrent procedure, the most defensible coding approach is to: (1) document both procedures distinctly in the operative note with separate instrument descriptions and surgical actions; (2) confirm NCCI edit status for 31591 + 31560/31561 at the time of billing; (3) if NCCI bundles the codes, evaluate whether 31599 (unlisted larynx) is a better code for the arytenoid adduction component; and (4) if submitting with 31599, include a cover letter with operative note excerpts explaining the arytenoid adduction procedure and the crosswalk to the comparison code for reimbursement reference.
Example 3 — Outpatient Hospital: Revision Medialization Thyroplasty — Implant Migration
Clinical Scenario: A 61-year-old male with a history of right medialization thyroplasty with silastic implant 14 months ago for post-esophagectomy right RLN paralysis presents with recurrent dysphonia and hoarseness developing over the past 2 months. Office strobolaryngoscopy confirms medial displacement of the right vocal cord implant — the silastic block has migrated posteriorly, resulting in inadequate anterior cord medialization and a recurrent anterior glottic gap. The patient is taken back to the operating room for revision right medialization thyroplasty: the original neck scar is re-opened, the prior cartilage window is re-exposed, the migrated silastic implant is removed, and a new Gore-Tex medialization implant is placed in the corrected anterior position. Voice confirmed improved with final Gore-Tex layering.
| Field | Code | Rationale |
|---|---|---|
| CPT | 31591--76--RT | Revision laryngoplasty, medialization, right — repeat procedure by the same surgeon; -76 = repeat procedure; -RT = right side; the revision surgery constitutes the full re-performance of 31591 with new implant placement; document that the prior implant was removed and a new implant was seated |
| PDx | T85.398A** | Other mechanical complication of other implanted prosthetic devices, implants and grafts, initial encounter — implant migration is a mechanical complication of the prior medialization implant; 7th character A = initial encounter for the complication; this is the reason for the revision surgery |
| SDx | J38.01 | Paralysis of vocal cords and larynx, unilateral — the underlying vocal cord paralysis persists; secondary to the complication code |
| SDx | R49.0 | Dysphonia — recurrent voice change is the symptom driving re-operation |
Note
Revision medialization thyroplasty falls outside the 90-day global period of the original 31591 in this scenario (14 months post-original surgery) — no modifier is needed to bypass the global period. If the revision had occurred within the 90-day global of the original procedure, modifier -78** (unplanned return to OR for complication) would be required to separately report the revision surgery. The -76 modifier (repeat procedure by the same physician) is appropriate here because the revision is clinically distinct from the original procedure and is documented as a new, planned surgical event addressing a complication. Document the specific clinical finding (implant migration on stroboscopy, recurrent dysphonia) that supports the medical necessity for revision surgery.
⚠️ Common Coding Pitfalls
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Reporting 31591 for vocal cord injection augmentation: The most fundamental error in laryngoplasty coding is using 31591 for a vocal cord injection procedure. 31591 is exclusively an open framework surgery — it requires an external neck incision, thyroid cartilage window creation, and implant insertion into the paraglottic space. Vocal cord injection with bulking agents (PROLARYN, Radiesse, fat, Cymetra) is coded to 31574 (flexible laryngoscopy with injection, unilateral) or 31570/31571 (direct laryngoscopy with injection). If the operative note does not describe an external neck incision and cartilage window, 31591 is incorrect. Coders unfamiliar with laryngology sometimes see “vocal cord medialization” in the procedure title and assign 31591 regardless of technique — always confirm the operative approach before code selection.
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Failing to apply -RT or -LT for laterality documentation: Because 31591 is a unilateral code and the vocal cord paralysis is inherently lateralized (right vs. left), appending the laterality modifier (-RT or -LT) provides important clinical documentation that aligns with the diagnosis (J38.01 is unspecified for side) and with clinical records. While these modifiers are not always required for payment, they improve claim accuracy, reduce audit risk, and support medical record reconciliation. When billing bilateral with -50, the two-line format (-RT + -LT) is often preferred over single-line -50 — confirm MAC preference.
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Not using modifier -57 on the same-day pre-operative E/M for a 90-day global procedure: Because 31591 carries a 90-day global period, if the surgeon performs a pre-operative office evaluation on the same day as the surgery and that evaluation represents the decision to proceed with the medialization thyroplasty, modifier -57 (decision for surgery) must be appended to the E/M code (NOT 31591) to separately bill the E/M service. Confusing -25 (used for procedures with 0-day or 10-day globals or when the E/M is not the decision-for-surgery visit) with -57 (required for the decision-for-surgery E/M on the same day as a 90-day global procedure) is a common modifier selection error in ENT billing.
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Not coding the C1878 device at the facility level: The HCPCS code C1878 (material for vocal cord medialization, synthetic, implantable) is separately reportable by the facility (ASC or outpatient hospital) for the medialization implant. Many facility billing teams overlook this device code or are not aware of payer-specific coverage for C1878 alongside 31591. Some payers package the implant into the 31591 payment; others separately reimburse it. A routine pre-authorization and benefit verification workflow should include checking whether the implant device (silastic, Gore-Tex, or titanium) is separately reimbursable under C1878 for the specific payer. Failing to submit C1878 when payable leaves device revenue on the table.
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Misidentifying the global period as 010 instead of 090: Because 31536 (microlaryngoscopy with biopsy, which is frequently performed before 31591 to confirm diagnosis) has a 010 global period, coders sometimes incorrectly apply a 010 global to 31591. 31591 has a 90-day (090) global period — all post-operative visits for 90 days are bundled, modifier -57 is required for same-day decision-for-surgery E/M, and any staged or related procedures within 90 days require -58. Verify the global period for each code independently and do not apply the global period of a concurrent biopsy code to the framework surgery code.
📎 Sources
AMA CPT 2025 Professional Edition — CPT 31591 Laryngoplasty, Medialization, Unilateral (added CPT 2017 per AAO-HNS/AMA code restructuring) · CMS 2025 Medicare Physician Fee Schedule Final Rule (CMS-1807-F) and CMS 2026 MPFS Final Rule (CMS-1832-F) · CMS RVU26A Relative Value Files · NCCI Policy Manual Chapter 5 (Respiratory System — Larynx), CMS 2024-2025 · ICD-10-CM Official Guidelines for Coding and Reporting FY2025 · ICD-10-PCS Official Guidelines for Coding and Reporting FY2025 · AAO-HNS Bulletin — “CPT Assistant on New Flexible Laryngoscopy Codes Released” (American Academy of Otolaryngology - Head and Neck Surgery, August 2017) · AAO-HNS CPT for ENT: Endoscopic Laryngoplasty — Guidance on CPT 31599 vs. 31591 (AAO-HNS, December 2023) · AAPC Otolaryngology Coding Alert — “Medialization Laryngoplasty Code Proves Elusive: Reader Question” (AAPC, September 2003) · GenHealth AI — CPT 31591 Clinical Description