Suchyta, Marissa

Background: Quantitative neuromorphometric analysis of the peripheral nerve is paramount to nerve regeneration research. However, this technique relies upon accurate segmentation and determination of myelin and axonal area. Manual histologic analysis methods are time-consuming and subject to error and bias. The authors demonstrate and validate a user-friendly method relying on open-source machine-learning software and requiring no coding knowledge. Methods: Nineteen rat facial nerve segments were fixed, osmicated, embedded in epoxy, sectioned, and stained with toluidine blue. Whole nerve cross-sections were scanned at 20×. Images were preprocessed in ImageJ to measure fascicular area and remove background. Images were imported into Ilastik, and the pixel classification module was used to segment myelin and axons. A novel CellProfiler pipeline was used with Otsu 2-threshold processing to segment and quantify individual axon and myelin objects from segmentations. Axon counts and g-ratio of nerve samples were acquired manually and using this technique to compare between methods. Results: Analysis of an entire nerve cross-section can be completed with this method in less than 5 minutes. Bland-Altman plot and intraclass correlation coefficient demonstrated reliability between axon counts performed manually and with this protocol. There was no significant difference in accuracy in determining g-ratio compared with manual techniques (P < 0.05). Conclusions: The protocol presented here demonstrates a novel and accurate means of segmenting and analyzing histologic nerve cross-sections. This method decreases both user time and potential bias, enables analysis of an entire nerve versus random sampling, and uses only open-source software freely accessible to researchers.

Background: Nerve transfer from the masseteric branch of the trigeminal nerve is a widely performed procedure for facial reanimation. Despite achieving powerful muscle force, clinical and aesthetic results leave room for improvement. Preclinical animal models are invaluable to establishing new therapeutic approaches. This anatomical study aimed to establish a masseteric-to-zygomatic nerve transfer model in rats and pigs. Methods: The masseteric branch of the trigeminal nerve and the zygomatic branch of the facial nerve were dissected in 30 swine and 40 rat hemifaces. Both nerves were mobilized and approximated to achieve an overlap between the nerve ends. Over the course of dissecting both nerves, their anatomy, length, and branching pattern were documented. At the coaptation point, diameters of both nerves were measured, and samples were taken for neuromorphometric analysis. Results: Anatomic details and landmarks were described. Tension-free coaptation was possible in all rat and pig dissections. In rats, the masseteric branch had an average diameter of 0.36 mm (±0.06), and the zygomatic branch average diameter was 0.46 mm (±0.13). In pigs, the masseteric branch measured 0.52 (±0.16) mm and the zygomatic branch, 0.59 (±0.16) mm. No significant differences were found between the diameters and axon counts of both nerves in pigs. In rats, however, their diameters, axon counts, and fascicular areas were significantly different. Conclusion: Our study demonstrated the feasibility of direct masseteric-to-zygomatic nerve transfer in rats and pigs and provided general anatomic knowledge of both nerves.

Summary: Aging of the face is the result of the interrelation of three-dimensional changes occurring over time among the 5 different layers of the face and its associated structures. Knowledge regarding the causes of these changes and identification of new key anatomic structures have helped elucidate one of the most complex areas of the human body. This has resulted in the introduction of pharmacologic agents to help stop, mitigate, or counteract signs of aging and restore the youthful appearance of the face. The authors performed a systematic search of the literature to review the current highest-level evidence of facial antiaging pharmacologic agents. Pharmacologic and minimally invasive antiaging treatments can target different components of facial aging and continue to evolve. With continuous research efforts, traditional treatments, such as botulinum toxin type A, injectable fillers, and chemical peels, are emerging in newer, more effective formulations, with longer lasting clinical results. However, for soft-tissue descent and facial volume loss, surgery remains the standard treatment. An adequate understanding of the three-dimensional process of facial aging over time (the fourth dimension), facial anatomy, and the pharmacologic properties of antiaging/rejuvenation agents are the sine qua non of facial antiaging treatment. The specific modality should be tailored to patient characteristics, preferences, and goals.

AbstractAdvances in computer-aided design and computer-aided manufacturing software have improved translational applications of virtual surgical planning (VSP) in craniomaxillofacial surgery, allowing for precise and accurate fabrication of cutting guides, stereolithographic models, and custom implants. High-resolution computed tomography (CT) imaging has traditionally been the gold standard imaging modality for VSP in craniomaxillofacial surgery but delivers ionizing radiation. Black bone magnetic resonance imaging (MRI) reduces the risks related to radiation exposure and has comparable functionality when compared with CT for VSP. Our group has studied the accuracy of utilizing black bone MRI in planning and executing several types of craniofacial surgeries, including cranial vault remodeling, maxillary advancement, and mandibular reconstruction using fibular bone. Here, we review clinical applications of black bone MRI pertaining to VSP and three-dimensional (3D)-printed guide creation for craniomaxillofacial surgery. Herein, we review the existing literature and our institutional experience comparing black bone MRI and CT in VSP-generated 3D model creation in cadaveric craniofacial surgeries including cranial vault reconstruction, maxillary advancement, and mandibular reconstruction with fibular free flap. Cadaver studies have demonstrated the ability to perform VSP and execute the procedure based on black bone MRI data and achieve outcomes similar to CT when performed for cranial vault reshaping, maxillary advancement, and mandibular reconstruction with free fibula. Limitations of the technology include increased time and costs of the MRI compared with CT and the possible need for general anesthesia or sedation in the pediatric population. VSP and 3D surgical guide creation can be performed using black bone MRI with comparable accuracy to high-resolution CT scans in a wide variety of craniofacial reconstructions. Successful segmentation, VSP, and 3D printing of accurate guides from black bone MRI demonstrate potential to change the preoperative planning standard of care. Black bone MRI also reduces exposure to ionizing radiation, which is of particular concern for the pediatric population or patients undergoing multiple scans.

Abstract The complex three-dimensional (3D) anatomy in facial allotransplantation creates a unique challenge for surgical reconstruction. Evolution of virtual surgical planning (VSP) through computer-aided design and computer-aided manufacturing has advanced reconstructive outcomes for many craniomaxillofacial indications. Surgeons use VSP, 3D models, and surgical guides to analyze and to trial surgical approaches even prior to entering the operating room. This workflow allows the surgeon to plan osteotomies and to anticipate challenges, which improves surgical precision and accuracy, optimizes outcomes, and should reduce operating room time. We present the development, evolution, and utilization of VSP and 3D-printed guides in facial allotransplantation at our institution, from guide conception to first clinical case.

Summary: Advances in virtual surgical planning and three-dimensionally–printed guides have enabled increased precision in vascularized free fibula flap reconstruction of the mandible and valuable preoperative planning. However, virtual surgical planning currently requires high-resolution computed tomographic scans, exposing patients to ionizing radiation. The aim of this study was to determine whether black bone magnetic resonance imaging can be used for accurate surgical planning and three-dimensionally–printed guide creation, thus reducing patient radiation exposure. This study included 10 cadaver heads and 10 cadaver lower extremities. A mock fibula free flap for mandible reconstruction was performed. Five operations were planned with guides created using black bone magnetic resonance imaging, whereas the other five were planned and performed using guides created with computed tomographic scan data. All specimens underwent a postoperative computed tomographic scan, and three-dimensional reconstruction of scans was performed and surgical accuracy to the planned surgery was assessed. Guides created from black bone magnetic resonance imaging demonstrated high accuracy to the surgical plan. There was no statistically significant difference in postoperative deviation from the plan when black bone magnetic resonance imaging versus computed tomographic scanning was used for virtual surgical planning and guide creation. Both modalities led to a postoperative positive or negative deviation from the virtual plan within 0.8 mm. This study demonstrates that virtual surgical planning and three-dimensionally–printed guide creation for free fibula flaps for mandible reconstruction can be performed using black bone magnetic resonance imaging with comparable accuracy to computed tomographic scanning. This could reduce radiation exposure for patients and enable a more streamlined imaging process for head and neck cancer patients.

Abstract Dermal filler injections, one of the most commonly performed procedures in facial esthetic surgery, are rising in popularity. This has also led to an increase in nonmedical grade filler injections performed by nonmedical personnel, including that of injectable silicone. Surgical removal of silicone fillers is challenging, as the hydrophobic material often disperses within the soft tissue as droplets. This can lead to a systemic inflammatory reaction requiring steroid treatment. MRI localization of the filler material does not enable intraoperative guidance, and palpitation of the material is challenging since the filler droplets are often too small to palpate and located in multiple planes. We present a case demonstrating the advantages of utilizing intraoperative ultrasound to localize and silicone filler material. Utilizing this technique, we were able to achieve a high degree of excision of silicone filler material and the patient was able to stop her previous necessary immunosuppressive steroid regimen successfully.

Abstract Background Autologous breast reconstruction (ABR) has grown in popularity due to improved aesthetic and long-term patient reported outcomes, but data regarding sensory reinnervation of autologous flaps remain limited. Traditionally, the lateral cutaneous branch of the fourth intercostal nerve has been used for flap neurotization, but the use of the anterior cutaneous branch of the intercostal nerves (ACB) offer a more optimal location to the microsurgical field when using internal mammary vessels for the microanastomosis. This study aimed to evaluate the optimum ACB recipient site level for sensory nerve coaptation in ABR. Methods Twelve hemi-chests were dissected from six fresh cadaveric females. Costal cartilages were removed and the anterior cutaneous intercostal nerve (ACB) and the lateral (subcutaneous) division of the anterior cutaneous branch (LACB) of the intercostal nerve were exposed. Anatomical measurements were recorded, and nerve samples were evaluated histologically with carbonic anhydrase staining to differentiate sensory fascicles. Assessment of fascicular diameter, axonal counts, and fascicular area were compared. Results A total of 75 nerve specimens were assessed. The ACB was identified at all levels (100%) and the subcutaneous LACB was noted consistently in the second to fourth rib space (96% cadavers), with a median length of 43, 37.5, and 37 mm, respectively. Across all rib spaces, the fascicular and axonal counts were comparable between the LACB and ACB. Nerves in the second intercostal space had a significantly larger mean fascicular area mean (112,816 ± 157,120 µm2) compared with that in the fourth (mean 26,474 ± 38,626 µm2), p = 0.03. Axonal count of sensory fascicles was the highest in the second intercostal nerves (p < 0.05). Conclusion This study provides anatomical and histological basis to determine the optimum recipient site choice for sensory coaptation in microsurgical breast reconstruction. This would aid in operative decision-making regarding the ideal recipient anterior cutaneous intercostal nerve branches for recipient site coaptation in ABR.