Successful Posterior Canal Wall Reconstruction with Tissue-Engineered Cartilage

Technology and Case Presentation

The patient was a 31-year-old man with left-sided pars flaccida–type cholesteatoma. Apart from middle ear surgery for right-sided cholesteatoma 2 years before, his previous medical history was unremarkable.

The procedure was approved by the Institutional Review Board of the university (15-245) and by the Japanese Ministry of Heath, Labor and Welfare (PB3170008). Written informed consent was obtained from the patient. Detailed procedures to produce tissue-engineered cartilage have been described in the literature. ³ Figure 1 summarizes the principal processes. Autologous serum for cell cultures was prepared from approximately 600 mL of venous blood. A small full-thickness cartilage plate (a square of approximately 10 mm) was harvested from the concha of the auricle and sent to a licensed facility that manufactures specific processed cells (Fujisoft Tissue Engineering Co, Ltd, FSTEC CPC; Tokyo, Japan) to produce tissue-engineered cartilage. Chondrocytes were isolated and expanded by cultures and subcultures. Cultured cells were recovered and placed in the porous body of a poly-L-lactic acid scaffold with atelocollagen hydrogel and then kept in a shaking culture. The final product was stick-shaped tissue-engineered cartilage (length, 50 mm; width, 6 mm; thickness, 3 mm) with a half moon–shaped cross section ( Figure 2a ) and of sufficient firmness (compressive strength, ≥0.1 MPa) to reconstruct bony structures.

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Figure 1.

Schemata showing procedures to manufacture and transplant tissue-engineered cartilage.

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Figure 2.

(a) Stick-shaped tissue-engineered cartilage. (b) Intraoperative image with sections of tissue-engineered cartilage placed to reconstruct the posterior canal wall, corresponding to the schema shown in Figure 3b .

Surgery (open mastoidectomy with posterior canal wall reconstruction and tympanoplasty) was performed with a postauricular incision. Open mastoidectomy was performed by drilling. The skin of the external acoustic canal (EAC) was preserved with the tympanic membrane (no incision in EAC). After removal of the cholesteatoma matrices, the ossicular chain was reconstructed by placing the reformed incus body between the head of the stapes and tympanic membrane. The size of the posterior canal wall defect was then measured with a piece of cardboard, and tissue-engineered cartilage was carved accordingly. Three sections of cartilage were placed side by side to form the reconstructed posterior canal wall ( Figure 2b ). These sections of tissue-engineered cartilage were completely wrapped by free fascia grafts to avoid exposure and contact with other materials. A defect in the tympanic membrane was also repaired with temporalis fascia grafts. EAC was finally packed with small pieces of sterilized gauze soaked in saline. Schemata for the procedure are shown in Figure 3 .

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Figure 3

(a) Cutting tissue-engineered cartilage just before transplantation. (b) Placement of pieces of tissue-engineered cartilage to reconstruct the posterior canal wall after open mastoidectomy. (c) Transverse sections representing pre- and postoperative configurations.

The postoperative course was uneventful. Epithelialization of the tympanic membrane and external ear canal showed progress within 1 month and was complete by 3 months after surgery. The reconstructed posterior canal wall showed no retraction until 6 months after surgery. Local and computed tomography findings are shown in Figure 4 . The pure tone average was unchanged (23 dB HL before surgery and 20 dB HL 6 months after surgery). Severe adverse effects were not observed. Therefore, the procedure for this patient was considered “successful” according to the study criteria.

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Figure 4.

(a) Preoperative axial computed tomography scans showing the attic, antrum, and mastoid cavity. (b) Local findings and coronal computed tomography scans before and 1 month (photo only), 3 months, and 6 months after surgery.

Discussion

To the best of our knowledge, this is the first-in-human case of reconstructing middle ear bony structures with tissue-engineered cartilage, suggesting a promising future for satisfactory reconstruction with minimal morbidity at the donor site. The product was initially invented to reconstruct the nasal bridge (ie, a 1-dimensional structure). The present case is also important because it shows that the application of this product may be expanded to reconstruct a plane (ie, a 2-dimensional structure).

Although a large amount of artificial material is acceptable (eg, artificial hip/knee joints) in other body parts protected by thick subcutaneous tissues and muscles, solid tissue reconstruction in our field of otolaryngology is frequently associated with difficulties. In reconstructive approaches with tissue-engineered cartilage, pediatric laryngotracheal reconstruction was successful in animal models, ⁴ and a clinical application for auricular reconstruction with patient-specific ear-shaped cartilage was recently reported. ⁵ Tissue-engineering approaches for solid tissue reconstruction in otolaryngology are no longer a fantasy, but they are steadily becoming a reality.

Author Contributions

Ken Ito, study design, data interpretation, article revision, final approval, accountability for the work; Makiko Toma-Hirano, study design, data collection, article drafting, final approval, accountability for the work; Takuya Yasui, study design, article drafting, final approval, accountability for the work.

Disclosures

Competing interests: None.

Sponsorships: None.

Funding source: None.