Complications of tissue expansion in the head and neck

A Gaussian process approach for rapid evaluation of skin tension

Skin tension plays a pivotal role in clinical settings, it affects scarring, wound healing and skin necrosis. Despite its importance, there is no widely accepted method for assessing in vivo skin tension or its natural pre-stretch. This study aims to utilise modern machine learning (ML) methods to develop a model that uses non-invasive measurements of surface wave speed to predict clinically useful skin properties such as stress and natural pre-stretch. A large dataset consisting of simulated wave propagation experiments was created using a simplified two-dimensional finite element (FE) model. Using this dataset, a sensitivity analysis was performed, highlighting the effect of the material parameters and material model on the Rayleigh and supersonic shear wave speeds. Then, a Gaussian process regression model was trained to solve the ill-posed inverse problem of predicting stress and pre-stretch of skin using measurements of surface wave speed. This model had good predictive performance (R2 = 0.9570) and it was possible to interpolate simplified parametric equations to calculate the stress and pre-stretch. To demonstrate that wave speed measurements could be obtained cheaply and easily, a simple experiment was devised to obtain wave speed measurements from synthetic skin at different values of pre-stretch. These experimental wave speeds agree well with the FE simulations, and a model trained solely on the FE data provided accurate predictions of synthetic skin stiffness. Both the simulated and experimental results provide further evidence that elastic wave measurements coupled with ML models are a viable non-invasive method to determine in vivo skin tension. STATEMENT OF SIGNIFICANCE: To prevent unfavourable patient outcomes from reconstructive surgery, it is necessary to determine relevant subject-specific skin properties. For example, during a skin graft, it is necessary to estimate the pre-stretch of the skin to account for shrinkage upon excision. Existing methods are invasive or rely on the experience of the clinician. Our work aims to present an innovative framework to non-invasively determine in vivo material properties using the speed of a surface wave travelling through the skin. Our findings have implications for the planning of surgical procedures and provides further motivation for the use of elastic wave measurements to determine in vivo material properties.

Prediction model for haematoma after tissue expander placement: A retrospective cohort study of 7080 cases over 20 years

Haematoma is an early complication of tissue expander placement and can lead to infection, capsule contracture and various complications, hindering successful reconstruction. However, no scientific models can accurately predict the risk of haematoma following tissue expansion. Therefore, this study aimed to develop and validate a prediction model for haematoma following tissue expander placement. The medical records of patients who underwent expander placement between 2001 and 2021 were obtained from the clinical database of the Department of Plastic Surgery at the Xijing Hospital. A total of 4579 consecutive patients with 7080 expanders and 179 expanded pocket haematomas were analysed. Multivariate logistic regression analysis identified adult age (P = 0.006), male sex (P < 0.001), scar reconstruction (P = 0.019), perioperative hypertension (P < 0.001), face and neck location (P = 0.002) and activated partial thromboplastin time above the normal range (P < 0.001) as risk factors for haematoma. Therefore, these were included in the prediction model, and a nomogram was constructed. The discrimination of the nomogram was robust (area under the curve: 0.78; 95% confidence interval: 0.72-0.83). Further, the prediction model had a strong fit (Hosmer-Lemeshow test, P = 0.066) and maintained similar discrimination after considering performance optimism (bootstrapped area under the curve: 0.79; 95% confidence interval: 0.73-0.84). This clinical prediction model was created using a generalisable dataset and can be utilised to obtain valid haematoma predictions after expander placement, assisting surgeons in implementing preventive measures or interventions to reduce the occurrence of haematoma.

Quantification of Bony Depression in Mastoid Region After Expander Implantation for Microtia Reconstruction in Hemifacial Microsomia

Object: Three-stage expansion method represents the most common form of microtia reconstruction in hemifacial microsomia (HFM). Although the complication related expander has lowered owing to the current advances, bony depression in mastoid region in microtia patients with hemifacial microsomia was observed in clinical work. The aim of this study was to quantify bony depression after retroauricular expander implantation and identify associated factors. Methods: 42 patients were enrolled and studied prospectively utilizing 3-dimensional (3D) evaluation. Craniofacial computed tomography (CT) was performed before the first (pre-expansion) and the second stage (post-expansion) and 3D quantification was done to quantify bony depression in mastoid region by using CT data. Univariate analysis was performed to identify factors associated with bony depression in mastoid region. Results: The mean level of mastoid depression was 0.83 mm (range: 0.07-4.08 mm), and the max level of mastoid depression was 1.40 mm (range: 0.20-6.65 mm). In univariate analysis, capsular duration of expansion and expansion volume were associated factors with mastoid depression. Conclusion: This study showed the possibility of mastoid depression following expander implantation for microtia reconstruction in hemifacial microsomia. Plastic surgeons should be aware of the possibility and associated factors of bony depression in mastoid region following expander implantation to optimize microtia reconstruction for patients with HFM.

Refractory Folliculitis Decalvans Treatment Success with a Novel Surgical Excision Approach Using Guarded High-Tension Sutures

Purpose

Folliculitis decalvans (FD) is a difficult-to-treat, localized scarring alopecia characterized by an expanding area of chronically inflamed purulent plaques or masses. Current treatment modalities vary and often result in only temporary remission. There are no reports of surgical therapies for FD. Here, we describe FD treatment using surgical excision and second-intention healing aided by guarded high-tension sutures.

Methods

Five patients (one woman and four men) with histologically confirmed FD were treated by surgical lesion excision. All wounds were allowed to heal via second-intention. Guarded high-tension sutures were employed to minimize tissue tears while aiding and guiding wound contraction.

Results

All wounds healed with a 47-83% spatial contraction of the maximum wound diameters. Three patients healed entirely by second-intention, while two required a minor skin graft to close the wound completely. No disease recurrence was noted at 10-24 months.

Conclusion

Surgical excision with second-intention healing aided by guarded high-tension sutures effectively treated small and extensive FD lesions with no recurrence at long-term follow-up. To our knowledge, this is the first report of successful surgical treatment of FD.

The Efficacy of Anterior Capsulotomy and Basal Capsulectomy Adherent to Expanded Scalp Flap During Alopecia Reconstruction in Pediatric Burned Patients

BACKGROUND

Scalp expansion is an optimal treatment for alopecia resulting from burn injuries, especially in the pediatric population through providing highly vascularized adjacent local tissues with optimal hair density, color matching, texture, and hair-bearing characteristics. The aim of this study was to evaluate the efficacy of anterior capsulotomy and basal capsulectomy adherent to expanded scalp flap during alopecia reconstruction with scalp expansion in pediatric burned patients.

METHODS

The study was conducted on 127 patients with an age range of 5 to 19 years who presented with postburn alopecia accompanied by hairline loss. The patients were divided into 2 groups: group I consisted of 58 patients who were operated on using conventional technique, and group II consisted of 69 patients who were operated using modified technique including basal capsulectomy on the skull side and anterior capsulotomy on the expanded scalp flap.

RESULTS

The Hairdex, a validated questionnaire of Hair-Specific Health-Related Quality of Life measures, showed that percentage of satisfaction concerning outcomes was 91.50%, psychological well-being was 95%, and self-confidence was 84.30% in group II, compared with 63%, 55.70%, and 66.20%, respectively, in group I. This significant values had a great positive effect on patient satisfaction, changing child's behavior and self-confidence.

CONCLUSION

Although physiological background of tissue expansion is the same, proper flap design with anterior capsulotomy on flap undersurface and basal capsulectomy on the skull side improve results of the traditional method significantly and minimize the complication rate. These surgical modifications provide maximum benefits from expanded tissue, with restoration of the hairline and a uniform hair direction.

LEVEL OF EVIDENCE

Level III, case-control study.

Expanded forehead flap in Asian nasal reconstruction

This article reviewed our experience of Chinese nasal reconstruction over 12 years and evaluated the effect of expanded forehead flap both aesthetically and functionally. The special skin type and other anatomic features of Chinese patients was understood thoroughly during the treatment. This article thus catered for the need of multiracial nasal reconstruction. We analyzed existing clinical data and demonstrated a typical case in detail. The postoperative result supported our strategy which advocated the extensive application of expanded forehead flap, together with flip scar flap as the internal lining. The features of Chinese patients also prompted the use of costal and auricular cartilage. Emerging technology like 3D-printing would benefit nasal reconstruction from more aspects.

Clinical Application of Pre-Expanded Perforator Flaps

Background: Challenging large soft tissue defects are typically treated with microvascular free tissue transfer; however, success has been noted with pre-expanded perforator flaps. Objective: To report outcomes and complications from pre-expanded perforator flaps. Methods: A retrospective chart review of patients undergoing tissue reconstruction with pre-expanded perforator flaps between 2014 and 2020. Data collection included flap type, defect characteristics, and complications. Results: All 29 patients had successful flap reconstruction without major complication. The median area of tissue defect was 17 × 13 cm² (range 7 × 4 to 27 × 24 cm²). Mean tissue expansion period was 15.2 weeks (range 9-26 weeks). The most common flap was the pre-expanded internal mammary artery perforator flaps. Conclusion: The findings of this study suggest that combining tissue expansion with a perforator flap for large tissue reconstruction can be successful with limited complications. This technique may allow a larger pliable skin flap that deserves further investigation.

Single-Cell Transcriptomics Uncover Key Regulators of Skin Regeneration in Human Long-Term Mechanical Stretch-Mediated Expansion Therapy

Tissue expansion is a commonly performed therapy to grow extra skin invivo for reconstruction. While mechanical stretch-induced epidermal changes have been extensively studied in rodents and cell culture, little is known about the mechanobiology of the human epidermis in vivo. Here, we employed single-cell RNA sequencing to interrogate the changes in the human epidermis during long-term tissue expansion therapy in clinical settings. We also verified the main findings at the protein level by immunofluorescence analysis of independent clinical samples. Our data show that the expanding human skin epidermis maintained a cellular composition and lineage trajectory that are similar to its non-expanding neighbor, suggesting the cellular heterogeneity of long-term expanded samples differs from the early response to the expansion. Also, a decrease in proliferative cells due to the decayed regenerative competency was detected. On the other hand, profound transcriptional changes are detected for epidermal stem cells in the expanding skin versus their non-expanding peers. These include significantly enriched signatures of C-FOS, EMT, and mTOR pathways and upregulation of AREG and SERPINB2 genes. CellChat associated ligand-receptor pairs and signaling pathways were revealed. Together, our data present a single-cell atlas of human epidermal changes in long-term tissue expansion therapy, suggesting that transcriptional change in epidermal stem cells is the major mechanism underlying long-term human skin expansion therapy. We also identified novel therapeutic targets to promote human skin expansion efficiency in the future.

Risk factors for tissue expander infection in scar reconstruction: a retrospective cohort study of 2374 consecutive cases

Background

Tissue expansion is used for scar reconstruction owing to its excellent clinical outcomes; however, the complications that emerge from tissue expansion hinder repair. Infection is considered a major complication of tissue expansion. This study aimed to analyze the perioperative risk factors for expander infection.

Methods

A large, retrospective, single-institution observational study was carried out over a 10-year period. The study enrolled consecutive patients who had undergone tissue expansion for scar reconstruction. Demographics, etiological data, expander-related characteristics and postoperative infection were assessed. Univariate and multivariate logistic regression analysis were performed to identify risk factors for expander infection. In addition, we conducted a sensitivity analysis for treatment failure caused by infection as an outcome.

Results

A total of 2374 expanders and 148 cases of expander infection were assessed. Treatment failure caused by infection occurred in 14 expanders. Multivariate logistic regression analysis identified that disease duration of ≤1 year (odds ratio (OR), 2.07; p < 0.001), larger volume of expander (200–400 ml vs <200 ml; OR, 1.74; p = 0.032; >400 ml vs <200 ml; OR, 1.76; p = 0.049), limb location (OR, 2.22; p = 0.023) and hematoma evacuation (OR, 2.17; p = 0.049) were associated with a high likelihood of expander infection. Disease duration of ≤1 year (OR, 3.88; p = 0.015) and hematoma evacuation (OR, 10.35; p = 0.001) were so related to high risk of treatment failure.

Conclusions

The rate of expander infection in patients undergoing scar reconstruction was 6.2%. Disease duration of <1 year, expander volume of >200 ml, limb location and postoperative hematoma evacuation were independent risk factors for expander infection.

Transcriptomic analysis reveals dynamic molecular changes in skin induced by mechanical forces secondary to tissue expansion

Tissue expansion procedures (TE) utilize mechanical forces to induce skin growth and regeneration. While the impact of quick mechanical stimulation on molecular changes in cells has been studied extensively, there is a clear gap in knowledge about sequential biological processes activated during long-term stimulation of skin in vivo. Here, we present the first genome-wide study of transcriptional changes in skin during TE, starting from 1 h to 7 days of expansion. Our results indicate that mechanical forces from a tissue expander induce broad molecular changes in gene expression, and that these changes are time-dependent. We revealed hierarchical changes in skin cell biology, including activation of an immune response, a switch in cell metabolism and processes related to muscle contraction and cytoskeleton organization. In addition to known mechanoresponsive genes (TNC, MMPs), we have identified novel candidate genes (SFRP2, SPP1, CCR1, C2, MSR1, C4A, PLA2G2F, HBB), which might play crucial roles in stretched-induced skin growth. Understanding which biological processes are affected by mechanical forces in TE is important for the development of skin treatments to maximize the efficacy and minimize the risk of complications during expansion procedures.

Tissue Expansion Improves the Outcome and Predictability for Alveolar Bone Augmentation: Prospective, Multicenter, Randomized Controlled Trial

Objectives: The purpose of this study was to evaluate the effectiveness of the intraoral use of subperiosteally placed self-inflating tissue expanders for subsequent bone augmentation and implant integrity. Material and methods: A prospective, multicenter, randomized controlled trial was performed on patients requiring alveolar bone graft for dental implant insertion. Patients were assigned to three groups: tissue expansion and tunneling graft (TET group), tissue expansion and conventional bone graft (TEG), and control group without tissue expansion. Dimensional changes of soft tissue and radiographic vertical bone gain, retention, and peri-implant marginal bone changes were evaluated and secondary outcomes; clinical complications and thickness changes of expanded overlying tissue were assessed. Results: Among 75 patients screened, a total of 57 patients were included in the final analysis. Most patients showed uneventful soft tissue expansion without any inflammatory sign or symptoms. Ultrasonographic measurements of overlying gingiva revealed no thinning after tissue expansion (p > 0.05). Mean soft vertical and horizontal tissue measurements at the end of its expansion were 5.62 and 6.03 mm, respectively. Significantly higher vertical bone gain was shown in the TEG (5.71 ± 1.99 mm) compared with that in the control patients (4.32 ± 0.97 mm; p < 0.05). Hard tissue retention— measured by bone resorption after 6 months—showed that control group showed higher amount of vertical (2.06 ± 1.00 mm) and horizontal bone resorption (1.69 ± 0.81 mm) compared to that of the TEG group (p < 0.05). Conclusion: The self-inflating tissue expander effectively augmented soft tissue volume and both conventional bone graft and tunneling techniques confirmed their effectiveness in bone augmentation. With greater amount of bone gain and better 6 month hard tissue integrity, the TEG group compared to the control group—without tissue expansion—showed that the combined modality of tissue expander use and guided bone regeneration (GBR) technique may improve the outcome and predictability of hard tissue augmentation.