Three-Dimensional Scanning Technique in the Congenital Microtia Reconstruction with Tissue Expander

Congenital microtia reconstruction remains one of the most complex challenges in plastic surgery. A successful outcome hinges on two critical components: the creation of a three-dimensional (3D) framework that mimics the intricate anatomy of a natural ear and the availability of sufficient soft tissue to cover this framework. Traditional methods, which rely on skin grafts to address posterior defects after framework elevation, often result in suboptimal outcomes due to color and texture mismatches, particularly in Asian populations. Additionally, skin grafts lack sensory function, leaving the reconstructed ear vulnerable to injury. The introduction of tissue expansion techniques by Brent in 1980 marked a significant advancement, enabling surgeons to generate additional skin with matching color and texture. However, the subjective nature of assessing skin adequacy post-expansion has limited its widespread adoption. This article presents a novel application of 3D surface scanning technology to objectively quantify skin availability during tissue expansion for microtia reconstruction.

Evolution of Tissue Expansion in Microtia Reconstruction

Tissue expansion has been refined over decades, with recent reports from Chinese and Korean groups demonstrating high success rates and low complication frequencies. Despite these advancements, a persistent challenge lies in determining whether sufficient skin has been generated to cover the 3D framework. Traditionally, this assessment relies on the surgeon’s empirical judgment, which introduces variability and potential for error. Overexpansion risks complications such as expander exposure, while under-expansion compromises aesthetic and functional outcomes. The integration of 3D scanning addresses this gap by providing precise, quantifiable measurements of expanded skin surface area.

Methodology: Integrating 3D Surface Scanning

Three male patients aged 8 to 28 years with congenital microtia (two concha-type and one lobule-type, per Nagata’s classification) underwent two-stage reconstruction using tissue expansion and autologous rib cartilage frameworks. Preoperative planning incorporated a DH-H30 3D surface scanner (Guangzhou Dimenstar Intelligent Technology) to capture detailed topography of the normal ear and the expanded mastoid region. Patients were scanned in a seated position to account for gravitational effects on tissue distribution.

The scanning protocol involved three key measurements:

1. Normal Ear Surface Area: The entire surface of the unaffected ear was digitized (Figure 1A, purple area).
2. Expanded Skin Surface Area: The expanded remnant ear and adjacent mastoid region were mapped (Figure 1A, pink area).
3. Expander Base Area: A mirrored projection of the expander’s footprint on the contralateral mastoid region was measured (Figure 1A, yellow area).

Using Geomagic Studio 2014 software (Morrisville, NC), these datasets were analyzed to calculate surplus skin availability. The formula applied was:
Surplus Skin = Expanded Skin Area − (Normal Ear Area + Expander Base Area)

Surgical Protocol

Stage 1: Tissue Expander Insertion and Expansion

A 100 mL kidney-shaped silicone gel expander (Wanhe Plastic Materials) was implanted subcutaneously in the mastoid region via a 4 cm incision within the temporal hairline. Expansion commenced 10 days postoperatively, with initial weekly injections of 6–12 mL saline. After 3D scanning confirmed adequate skin generation, the regimen shifted to 4–6 mL every two weeks for 2–3 months to minimize mechanical stress.

Stage 2: Framework Fabrication and Transposition

Autologous cartilage was harvested from the sixth, seventh, and eighth ribs via a subcostal incision. The sixth and seventh costal cartilages were preserved in continuity at their posterior perichondrium to form a stable base, while the eighth rib provided additional structural components. A 3D framework was carved using Brent’s technique, prioritizing anatomical fidelity of the helix, antihelix, and tragus. The preauricular skin pocket was dissected, and the expanded flap was draped over the framework without tension. Lobule transposition and minor contour adjustments completed the reconstruction.

Clinical Outcomes and 3D Scanning Data

The expansion phase lasted 121–176 days, with total infused volumes ranging from 174 mL to 190 mL. Post-expansion 3D scans revealed expanded skin surface areas of 7,119.70 mm², 8,310.93 mm², and 8,042.76 mm², exceeding the normative ear areas (3,852.94 mm², 4,351.08 mm², and 3,591.27 mm²) by margins of 2,173.6–4,457.82 mm² after subtracting expander base areas (3,093.16 mm², 3,094.28 mm², and 1,847.78 mm²). These quantitative findings confirmed sufficient skin for tension-free framework coverage.

All patients achieved stable, aesthetically satisfactory outcomes at two-year follow-up, with no complications such as flap necrosis, infection, or framework exposure. Figure 1B–E illustrates a representative lobule-type case, demonstrating successful transformation from preoperative deformity to post-expansion tissue readiness and final reconstructed auricle.

Discussion: Advantages and Refinements

The 3D scanning system introduces objectivity to a traditionally subjective process. By quantifying surface areas, surgeons can precisely time the transition between expansion phases and determine framework insertion readiness. This reduces reliance on experiential judgment, particularly beneficial for less-experienced practitioners. Furthermore, the non-contact nature of scanning eliminates tissue distortion caused by manual measurement tools.

The study’s preliminary data highlight two critical insights:

1. Regional Expansion Variability: Gravity-induced downward displacement of the expander generates uneven tension, with the upper third of the ear—requiring the greatest surface area—receiving less expansion. Future protocols will incorporate segmental analysis (upper, middle, lower thirds) to optimize inflation patterns.
2. Fluid vs. Air Inflation: Saline’s weight exacerbates inferior expander migration. Transitioning to air inflation may improve upper pole expansion, though long-term data are needed.

Broader Applications and Future Directions

While focused on microtia, this methodology holds promise for other tissue expansion applications:

• Breast Reconstruction: Quantifying skin availability post-mastectomy.
• Nevus Excision: Planning staged resection of giant congenital nevi.

Future studies will establish predictive formulas correlating inflation volume, duration, and surface area generation. Prospective data collection at each expansion session will refine protocols, enabling patient-specific customization.

Conclusion

The integration of 3D surface scanning into microtia reconstruction with tissue expansion represents a paradigm shift toward precision medicine. By replacing empirical guesswork with quantitative metrics, this technique enhances safety, reproducibility, and aesthetic outcomes. Ongoing refinements in regional analysis and inflation mechanics promise to further elevate its utility, solidifying its role as an indispensable tool in reconstructive plastic surgery.

doi.org/10.1097/CM9.0000000000001279

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