Date of Award

January 2025

Document Type

Open Access Thesis

Degree Name

Medical Doctor (MD)

Department

Medicine

First Advisor

Bohdan Pomahac

Abstract

As a transformative surgical procedure, face transplantation restores form and function to patients with severe facial disfigurements, yet the long-term aging dynamics of transplanted tissues remain poorly characterized. This study aimed to investigate the progression of facial ptosis in transplanted facial allografts over time, addressing a critical gap in the understanding of long-term outcomes following face transplantation. Specific aims include quantifying ptosis progression using cephalometric measurements, identifying regional variations in the degree of ptosis across the face, and comparing changes between face transplant recipients and a non-face transplanted control cohort to contextualize findings.

To assess these aims, standardized frontal headshots of nine face transplant recipients were analyzed at three time points: T0 (1 year post-transplantation), T1 (3 years post-transplantation), and T2 (most recent follow-up photograph available post-transplantation, median follow-up of cohort: 9 years). Utilizing ImageJ software, ten independent cephalometric measurements adapted from the literature were employed to assess facial ptosis at each timepoint in this patient cohort. These metrics include eyebrow peak angle (bilateral), eyebrow tail angle (bilateral), vertical eyelid-iris ratio (bilateral), lateral canthus-oral-nasal angle (bilateral), bigonial-bizygomatic ratio and ergotrid length-upper lip ratio. These same measurements were performed on a group of ten non-face transplant human subjects at two timepoints, T1 and T2, with a median time interval of 78 years between them. Various descriptive analysis and non-parametric statistical tests were utilized for evaluating the results.

The results demonstrated significant changes between median values at T1 and T2 of the face transplant cohort when examining the left eyebrow peak angle (T1: 28.54° vs T2: 20.98°, p=0.0239), left eyebrow tail angle (T1: 7.01° vs T2: 15.32°, p=0.0085), right eyebrow tail angle (T1: 6.30° vs T2: 15.53°, p=0.0008), left lateral canthus-oral-nasal angle (T1: 42.80° vs T2: 37.72°, p<0.0001), bigonial-bizygomatic ratio (T1: 0.87 vs T2: 0.91, p=0.0007), and ergotrid length-upper lip ratio (T1: 0.77 vs T2: 0.83, p=0.0007). There was no significant difference noted between median values at T1 and T2 when examining the right eyebrow peak angle (T1: 27.79° vs T2: 20.59°, p=0.1821), left vertical eyelid-iris ratio (T1: 0.65 vs T2: 0.62, p=0.1944) and the right lateral canthus-oral-nasal angle (T1: 42.68° vs T2: 37.11°, p=0.0689). Across all facial ptosis metrics evaluated in the upper, middle, and lower face there was no significant difference between T0 and T1 timepoints (p>0.05). Sub-analysis of the cohort across applicable facial ptosis metrics between patients with bony components included in their allograft versus myocutaneous only allograft highlighted in overall trend toward greater facial ptosis in myocutaneous only allografts. When examining the non-face transplant cohort, all facial ptosis metrics demonstrated significant changes between the two timepoints. A comparison of the median change in various facial ptosis metrics from T1 to T2 of the face transplant cohort compared to the non-face transplant human subjects demonstrated no significant difference across all facial ptosis metrics evaluated except for the ergotrid length-upper lip ratio which demonstrated significantly greater ptosis in the non-face transplant cohort (0.14 vs 0.07; p=0.0220).

This study is the first to provide a direct quantification of the degree of facial ptosis seen in face transplant recipients over time. Ultimately, the findings underscore the critical need for ongoing surveillance and periodic revision procedures in face transplant recipients to maintain functional and aesthetic outcomes over the long term. While early revisions mitigate ptosis during the initial years post-transplantation, significant ptosis observed at longer follow-up intervals demonstrates the limitations of these interventions in addressing long-term tissue laxity. Preliminary findings here suggest that incorporating skeletal subunits into facial allografts may provide biomechanical advantages by preserving ligamentous support and reducing ptosis. Additionally, the findings of this research contribute to the growing understanding of facial allograft aging and offers a comparative framework against natural facial aging. The comparative ptosis progression across a median 6-year time interval of face transplant patients equalizing to a median 78-year time interval of non-face transplant human subjects underscores the potentially accelerated aging dynamics of facial allografts as they relate to facial ptosis. Collectively, these findings provide a foundation for optimizing surgical techniques, improving long-term care strategies, and expanding the utility of facial ptosis metrics in reconstructive and rehabilitative medicine.

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This is an Open Access Thesis.

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