Development of a morphing technique for predicting the position and size of an artificial ear in hemifacial microsomia patients

Determination of Novel, Cranium-Based Relationships for Construct Placement in Microtia Reconstruction for Hemifacial Microsomia Patients

OBJECTIVE

Determine if the ideal location of the construct in microtia reconstruction for hemifacial microsomia (HFM) can be more accurately derived from measurements on the cranium.

DESIGN

High-resolution computerized tomography (CT) images were analyzed through craniometric linear relationships.

SETTING

Our tertiary care institution from 2000 to 2021.

PATIENTS/PARTICIPANTS

Patients diagnosed with HFM and microtia, who had high-resolution craniofacial CT scans, yielding 36 patients accounting for 44 CT scans.

MAIN OUTCOME MEASURE(S)

First, the integrity of the posterior cranial vault among HFM patients was determined. If proven to be unaffected, it could be used as a reference in the placement of the construct. Second, the position of the ear in relation to the cranium was assessed in healthy age-matched controls. Third, if proven to be useful, the concordance of these cranium-based relationships could be validated among our HFM cohort.

RESULTS

The posterior cranial vault is unaffected in HFM (P > .001). Further, craniometric relationships between the tragus and the Foramen Magnum, as well as between the tragus and the posterior cranium, have been shown to be highly similar and equally precise in predicting tragus position in healthy controls (P > .001). These relationships held true across all age groups (P > .001), and importantly among HFM patients, where the mean absolute difference in predicted tragus position never surpassed 1.5 mm.

CONCLUSIONS

Relationships between the tragus and the cranium may be used as an alternative to distorted facial anatomy or surgeon's experience to assist in pre-operative planning of construct placement in microtia reconstruction for HFM patients.

Morphologic Variability of Bone and Soft Tissue in Microtia With Hemifacial Microsomia

Objective: Microtia patients with hemifacial microsomia (HFM) have a host of distinct anatomical disorder of skeletal and soft tissue asymmetries. The purpose of this study was to assess soft tissue discrepancies in microtia patients with HFM and their correlation with skeletal discrepancies. Methods: A total of 42 patients were enrolled and studied prospectively using a 3-dimensional superimposition and color mapping of the soft and hard tissues. Mirroring techniques created perfectly symmetric models for comparison. Differences between affected and normal sides were evaluated in 5 areas: retroauricular mastoid, malar, maxillary frontal, mandibular frontal, and gonion areas. Pearson correlations were used to assess the relationship between skeletal and soft tissue asymmetry. Results: Hard tissue asymmetry ranged from 0.79 mm (mandibular frontal) to 1.29 mm (malar), while soft tissue asymmetry ranged from 1.34 mm (maxillary frontal) to 5.26 mm (retroauricular mastoid). Correlations between skeletal and soft tissue asymmetry varied, with the strongest correlation observed at the retroauricular mastoid area and the weakest at the maxillary frontal area. Conclusion: There was a high correlation between bone and soft tissue hypoplasia at the retroauricular mastoid area, while the other evaluated areas showed poor correlation between skeletal and soft tissue asymmetries. Clinicians should assess each component separately for optimal treatment planning in microtia patients with HFM.

Surgical Microtia Reconstruction in Hemifacial Microsomia Patients: Current State and Future Directions

Background:

Hemifacial microsomia (HFM) is one of the most common congenital craniofacial disorders. Among many other features, microtia is present in the large majority of these patients. However, mainly due to the unilateral hypoplastic anatomy, microtia reconstruction among this patient population remains a reconstructive challenge for plastic surgeons. Given that no clear standards exist, an evidence-based synthesis of the literature was devised.

Methods:

A systematic search of Pubmed, Medline, and Embase was carried out, in accordance with the PRISMA guidelines. Studies discussing surgical microtia reconstruction for HFM patients were retained. Qualitative data regarding study design, challenges addressed, specific recommendations, and their respective strengths/limitations were extracted from each. Retrieved recommendations were consolidated and assigned a level of evidence grade.

Results:

Although only 11 studies were included in this review, these provided 22 main recommendations regarding the eight HFM-specific challenges identified, which were of either grade C (n = 5) or D (n = 17). Included studies addressed construct location (n = 7), the low hairline (n = 6), soft tissue construct coverage (n = 6), earlobe reconstruction (n = 6), construct projection (n = 5), anomalies of the relevant neurovascular systems (n = 2), retroauricular construct coverage (n = 2), and sizing of the construct (n = 2).

Conclusions:

Given the many persisting reconstructive challenges regarding surgical microtia reconstruction for HFM patients, the authors present a comprehensive and evidence-based consolidation of recommendations specific to these challenges. The authors hope this systematic review can appropriately guide plastic surgeons and will ultimately improve care for this patient population.