Procedural Dermatology Volume I: Reconstruction E-Book

• Herausgeber: Thieme
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 627

Veröffentlichungsjahr: 2023

Beschreibung

A comprehensive, practical resource on reconstructive techniques after Mohs surgery

Since the 1980s, dermatologists have increasingly assumed the reins of surgical reconstruction after Mohs micrographic surgery of the head and neck, as well as delicate areas of the hands, feet, and genitalia. Volume I of Procedural Dermatology: Postresidency and Fellowship Compendium, edited by esteemed dermatologists David H. Ciocon and Yoon-Soo Cindy Bae, provides a comprehensive review of the latest techniques in surgical reconstruction after Mohs surgery based on the location of the defect. The content reflects years of firsthand expertise from an impressive group of internationally recognized reconstructive surgery experts, who contributed chapters on evidence-based surgical, cosmetic, and laser techniques.

Key Features

• Editors are fellowship trained, double board-certified in dermatology and micrographic dermatologic surgery
  
• Contributions from pioneers in the field, including Richard Bennett and John Zitelli
  
• A concise, algorithmic approach enhances acquisition of knowledge, while allowing treatment tailored to individual cases
  
• Sixteen consistently formatted chapters discuss anatomic-specific reconstructive techniques from the scalp to the lower legs, as well as scar revision, melanoma, and prevention and repair of internal nasal valve dysfunction

This is the quintessential resource on restorative surgery after Mohs surgery for dermatology fellows and clinicians who are new to practice. It will also benefit seasoned dermatologic surgeons looking to hone and expand their existing techniques.

Leseprobe

Procedural Dermatology

Volume I: Reconstruction

Postresidency and Fellowship Compendium

David H. Ciocon, MD Director of Procedural Dermatology and Dermatologic Surgery Associate Professor of Medicine Director of Clinical Operations Division of Dermatology Montefiore Medical Center Albert Einstein College of Medicine Bronx, New York, USA

Yoon-Soo Cindy Bae, MD Mohs Micrographic Surgeon and Dermatologic Oncologist Cosmetic and Laser Surgeon Laser & Skin Surgery Center New York; Clinical Assistant Professor of Dermatology New York University Grossman School of Medicine The Ronald O. Perelman Department of Dermatology New York, New York, USA

466 Illustrations

ThiemeStuttgart • New York • Delhi • Rio de Janeiro

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DOI: 10.1055/b000000252

ISBN: 978-3-13-242405-0

Also available as an e-book:

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Contents

Preface

Contributors

1Facial, Scalp, Neck, Hands, Lower Extremities, and Genital Anatomy

Shauna Higgins, Marissa B. Lobl, and Ashley Wysong

1.1Introduction

1.2Head and Neck

1.2.1Cosmetic Units and Facial Fat Pads

1.2.2Superficial Landmarks

1.2.3Muscles

1.2.4Innervation

1.2.5Vasculature

1.2.6Special Considerations

1.3Hand

1.3.1Innervation

1.3.2Vasculature

1.3.3Fascia and Soft Tissue

1.3.4Nail Anatomy

1.4Lower Extremities

1.4.1Innervation

1.4.2Vasculature

1.4.3Toe Nails

1.5Genitalia

1.5.1Female Genital Anatomy

1.5.2Male Genital Anatomy

1.6Conclusion

2Reconstruction of the Forehead Unit

Ardeshir Edward Nadimi, Sonal A. Parikh, and Vishal Anil Patel

2.1Introduction

2.1.1Anatomy

2.2Aesthetic Subunits

2.2.1Central Subunit

2.2.2Lateral Subunit

2.2.3Temple Subunit

2.2.4Eyebrow Subunit

2.3Massive Forehead Defects

2.4Tissue Expansion

2.4.1Introduction

2.4.2Intraoperative Tissue Expansion

2.4.3Internal and External Tissue Expanders

2.5Conclusion

3Reconstruction of the Nasal Unit

Ian Maher, Jamie L. Hanson, and Gabriel Amon

3.1Structure and Function

3.2Skin Characteristics

3.3Nasal Subunits

3.4Keys to Success

3.5Local Reconstruction of Subunits

3.5.1Mobile Subunits

3.5.2Immobile Subunits

3.5.3Large or Multisubunit Defects

3.6Conclusion

4Reconstruction of the Eyelid Units

Anne Barmettler

4.1Eyelid Reconstruction

4.1.1Location

4.1.2Depth

4.1.3Size

4.2Lower Lid Unit

4.2.1Skin-Only Defects

4.2.2Full-Thickness Defects (Skin and Tarsal Defects)

4.2.3Key Points

4.3Upper Lid Unit

4.3.1Skin-Only Defects

4.3.2Full-Thickness Defects (Skin and Tarsal Defects)

4.3.3Key Points

4.4Lateral Canthal Subunit

4.4.1Key Points

4.5Medial Canthal Subunit

4.5.1Key Points

4.6Conclusion

5Reconstruction of the Cheek

Jenna Wald and C. William Hanke

5.1Introduction

5.2Anatomy

5.2.1Soft Tissue

5.2.2Innervation

5.2.3Vascular Supply/Lymphatics

5.3Clinical Considerations

5.4Algorithm for Cheek Reconstruction

5.5Medial Subunit

5.5.1Advancement Flap

5.5.2Rotation Flap

5.5.3V-Y Advancement Flap

5.6Zygomatic Subunit

5.6.1Primary Closure

5.6.2V-Y Advancement Flap

5.7Lateral Subunit

5.7.1Advancement Flap with Burow’s Triangle

5.8Buccal Subunit

5.8.1Primary Closure

5.8.2Transposition Flap

6Reconstruction of the Upper and Lower Lip Unit

Gian Vinelli, Ramone F. Williams, David H. Ciocon, and Anne Truitt

6.1Anatomic Considerations

6.2Approach to Reconstruction of the Lip Unit

6.3Upper Lip

6.3.1Philtral Subunit

6.3.2Philtral Subunit: Vermilion Lip Only

6.3.3Lateral Subunits

6.3.4Vermilion Lip Only

6.4Lower Lip Reconstruction

6.4.1Cutaneous Lower Lip with or without Vermilion Involvement

6.5Vermilion Involvement Only

6.5.1Less than One-Third of the Lip Length

6.5.2Greater than One-Third of the Lip Length

7Reconstruction of the Mental Unit

Thomas K. Barlow, Arjun Dayal, and Vineet Mishra

7.1Anatomy

7.2Defects and Repairs

7.3Central Chin

7.3.1Central Chin Key Points

7.4Lateral Chin

7.4.1Lateral Chin Key Points

7.5Submental Chin

8Reconstruction of the Ear

David G. Brodland

8.1Basic Concepts in Reconstruction of the Ear

8.1.1Superior Helix

8.1.2Mid Helix

8.1.3Earlobe/Inferior Helix

8.2Antihelix and Conchal Bowl

8.3Posterior Ear Defects

9Reconstruction of the Neck Unit

Merrick A. Brodsky, Saud Aleissa, and Anthony Rossi

9.1Anatomy of the Neck

9.1.1Anterior Cervical Triangle

9.1.2Posterior Cervical Triangle

9.1.3Platysma

9.2.1Primary Closure

9.2.2Secondary Intention Healing

9.2.3Skin Grafts

9.2.4Skin Substitutes

9.2.5Skin Flaps

9.2.6Complications

10Reconstruction of the Scalp

Adam J. Tinklepaugh and Rachel Westbay

10.1Scalp Anatomy

10.1.1Soft-Tissue Layers

10.1.2Vascular Supply and Lymphatics

10.2Preoperative Evaluation

10.2.1Evaluating the Patient

10.2.2Evaluating the Defect

10.3Essential Concepts in Scalp Reconstruction

10.3.1Reconstructive Goals

10.3.2Surgical Principles

10.4Choosing the Reconstructive Approach

10.4.1Second Intention

10.4.2Primary Closure

10.4.3Skin Grafting

10.4.4Local Flaps

10.4.5Regional Flaps

10.4.6Microsurgical Free Tissue Transfer

10.4.7Piecemeal Closure

10.5Adjuvant Surgical Techniques

10.5.1Tissue Expansion

10.6Algorithm for Scalp Reconstruction

11Reconstruction of the Hand and Nail Unit after Mohs Surgery

Evelyn R. Reed, Thomas J. Wright, Madison E. Tattini, and Shaun D. Mendenhall

11.1Introduction

11.2Cutaneous Malignancies of the Hand

11.2.1Nonmelanoma Skin Cancers of the Hand

11.2.2Treatment for NMSC of the Hand

11.2.3Melanoma of the Hand

11.2.4Treatment for Melanoma of the Hand

11.3Dorsum of Hand

11.3.1Anatomy

11.3.2Reconstruction

11.4Dorsal Surface of Fingers

11.4.1Anatomy

11.4.2Reconstruction

11.5Thumb

11.5.1Anatomy

11.5.2Reconstruction

11.6Nail Plate and Nail Bed

11.6.1Anatomy

11.6.2Reconstruction

11.7Conclusion

12Reconstruction of the Genital

Jenny C. Hu and Richard G. Bennett

12.1Anatomy

12.1.1Anatomy of the Male External Genitalia

12.1.2Anatomy of the Female External Genitalia

12.1.3Anatomy of the Perineum

12.2Anesthesia

12.3Reconstruction

12.3.1Reconstruction of the Male External Genitalia

12.3.2Reconstruction of the Female External Genitalia

12.3.3Reconstruction of the Perineum

12.4Conclusion

13Reconstruction of Lower Legs

Kira Minkis, Thomas S. Bander, and Kristina Navrazhina

13.1Introduction

13.2Anatomy of Lower Extremity

13.2.1Arterial Supply

13.2.2Venous Drainage

13.2.3Cutaneous Innervation

13.3Reconstructive Approaches for Lower Extremity Defects

13.3.1Preoperative Consultation

13.3.2Overviewof Reconstructive Approaches

13.3.3Secondary Intention Healing

13.3.4Linear Repair

13.3.5Skin Grafts

13.3.6Random Pattern Flaps

13.3.7Perforator Flaps

13.4Postoperative Care Following Lower Extremity Reconstruction

13.4.1Dressings

13.4.2Unna Boot

13.4.3Postoperative Immobilization

13.5Complications

13.5.1Infection

13.5.2Dehiscence

13.5.3Contact and Stasis Dermatitis

13.5.4Hematoma or Seroma

13.5.5Management of Scarring

13.6Conclusion

14Reconstruction of Scars

Jill Waibel, Chloe Gianatasio, and Rebecca Lissette Quinonez

14.1Introduction: Why DoWe Scar?

14.2Types of Scars

14.2.1Atrophic

14.2.2Hypertrophic

14.2.3Keloid

14.2.4Contracture

14.3Scar Prevention

14.3.1Early Intervention

14.3.2Passive and Active Therapies

14.3.3To Skin Graft or not to Skin Graft

14.4Scar Revision

14.4.1Discoloration

14.4.2Laser Treatment of Erythema

14.4.3Laser Treatment of Pigmentation

14.4.4Discoloration in Hypertrophic and Keloid Scars

14.4.5Textural Irregularities

14.4.6Atrophic and Hypopigmented Scars

14.4.7Excision/Punch Biopsies

14.4.8Laser

14.4.9Laser-Assisted Delivery

14.4.10Hypopigmentation

14.4.11Atrophy

14.4.12Fat Grafting

14.4.13Other Techniques (Hyaluronic Acid Filler, Subcision)

14.4.14Hypertrophic and Keloid Scars

14.4.15Surgery

14.4.16Z-Plasty

14.4.17W-Plasty

14.4.18Laser

14.4.19Laser-Assisted Delivery

14.4.20Adjuvant Therapies

14.4.21Combination Treatment

14.5Conclusion

15Mohs and Melanoma

John A. Zitelli

15.1Melanoma In Situ and Malignant Melanoma

15.2Treatment

15.3Indications for MMS

15.4Mohs Micrographic Surgery: Procedure

15.4.1Technique

15.4.2Positive Margins

15.5Slow Mohs and Other Staged Excisions

15.6Local Recurrence after MMS

15.7Reconstruction after Clear MMS Margins

15.8Controversies

16Prevention and Repair of Internal Nasal Valve Dysfunction for the Reconstructive Surgeon

Parth Patel, Ethan T. Routt, Ziad M. Alshaalan, and David H. Ciocon

16.1Introduction

16.2Modalities/Treatment Options Available

16.3Indications and Evaluation of INV Dysfunction

16.4Patient Selection/Considerations

16.5Noninvasive Techniques

16.6Invasive Techniques: Suspension Sutures

16.6.1Nasal Valve Suspension toward the Orbital Rim

16.6.2Nasal Valve Suspension toward the Lateral Side of the Nasal Bone

16.6.3Nasal Valve Suspension toward Local Tissue

16.7Invasive Techniques: Cartilage Grafts

16.8Invasive Techniques: Repositioning and Reallocation of Scar Tissue

16.9Postoperative Instructions

16.10Potential Complications and their Management

16.11Pearls/Pitfalls

Index

Preface

The history of dermatologic surgery has witnessed profound but sustained transformation over the past four decades. Prior to the 1980s, many complex surgical reconstructions after Mohs surgery were outsourced to plastic surgeons or head and neck surgeons because dermatologists lacked the training or comfort level to perform such difficult cases. As education has evolved at the postgraduate level in both residency and fellowship programs and through conferences offered by the American College of Mohs Surgery and the American Society of Dermatologic Surgery, dermatologists have increasingly assumed the reins of surgical reconstruction after Mohs micrographic surgery, whether it involves the head and neck, or the delicate areas of the hand, feet, and genitalia.

The aim of this compendium is to provide a comprehensive summary of the latest techniques in surgical reconstruction after Mohs surgery based on the location of the defect. Drawing on the expertise of internationally recognized experts in the field of reconstructive surgery, we adopt a concise but algorithmic approach tailored to the benefit of the fledgling surgeon fresh from training and the seasoned surgeon looking to hone and expand existing techniques. While we recommend algorithms as a way of forming logical and coherent surgical plans for challenging defects in difficult-to-treat areas, we caution against a “cookbook” approach. Like any other in the art of medicine, individual cases must be treated on an individual basis. Treatment plans should always be tailored to the individual patients with close consideration of their unique anatomy, their comorbidities, their age, their social situation, their short- and long-term goals, and their insights and expectations.

In the words of Isaac Newton, our humble efforts are made possible only by standing on the shoulders of giants. Many of the techniques described in this text were developed, modified, and perfected by pioneers such as Richard G. Bennett and John A. Zitelli, who graciously agreed to contribute to this endeavor, among others. We are grateful to all our contributors who gave their time and their wisdom selflessly. Ours is a collective effort whose ultimate reward comes from the sharing and distribution of knowledge. Finally, I would be remiss if I did not extend my deepest gratitude to my co-editor Dr. Yoon-Soo “Cindy” Bae who had the vision and courage to conceive this idea, which is a labor of friendship and deep mutual respect. Thank you for inviting me on this incredible journey.

David H. Ciocon, MD

Contributors

Saud Aleissa, MD, FAAD

Assistant Professor

Department of Dermatology

King Abdulaziz University

Jeddah, Saudi Arabia

Ziad M. Alshaalan, MD

Department of Internal Medicine

College of Medicine

Jouf University

Sakaka, Saudi Arabia

Gabriel Amon, MD

Resident

Department of Dermatology

University of Minnesota Medical School

Minneapolis, Minnesota, USA

Thomas S. Bander, MD

Director of Procedural Dermatology

Department of Dermatology

Maine Medical Partners

Portland, Maine, USA

Thomas K. Barlow, DO, DHEd

Mohs Surgeon

Deseret Dermatology

Saratoga Springs, Utah, USA

Anne Barmettler, MD

Director of Oculoplastics;

Associate Professor of Ophthalmology;

Associate Professor of Surgery

Department of Ophthalmology

Montefiore Medical Center, Albert Einstein College of Medicine

Bronx, New York, USA

Richard G. Bennett, MD

Professor of Clinical Dermatology

Department of Dermatology

UCLA and USC Schools of Medicine

University of Southern California

Los Angeles, California, USA

David G. Brodland, MD

Assistant Professor

Department of Dermatology

Zitelli & Brodland Skin Cancer Center

University of Pittsburgh

Pittsburgh, Pennsylvania, USA

Merrick A. Brodsky, MD

Mohs Micrographic Surgery and Dermatologic Oncology Fellow

Department of Dermatology

The Ohio State Medical Center

Columbus, Ohio, USA

David H. Ciocon, MD

Director of Procedural Dermatology and Dermatologic Surgery;

Associate Professor of Medicine;

Director of Clinical Operations

Division of Dermatology

Montefiore Medical Center

Albert Einstein College of Medicine

Bronx, New York, USA

Arjun Dayal, MD

Attending Dermatologist

Section of Dermatology

Rush Copley Medical Center

Aurora, Illinois, USA

Chloe Gianatasio, MS

Director

Department of Scientific Affairs

Efficient CME

Fort Lauderdale, Florida, USA

C. William Hanke, MD

Clinical Professor

Department of Otolaryngology

Indiana University School of Medicine

Indianapolis, Indiana, USA

Jamie L. Hanson, MD

Dermatologist (nonacademic)

Department of Dermatology

Associated Skincare Specialists

Blaine, Minnesota, USA

Shauna Higgins, MD

Resident Physician

Department of Dermatology

University of Southern California

Los Angeles, California, USA

Jenny C. Hu, MD, MPH

Associate Clinical Professor

Department of Dermatology

Keck School of Medicine

University of Southern California

Los Angeles, California, USA

Marissa B. Lobl, PhD

Medical Student

Department of Dermatology

University of Nebraska Medical Center

Omaha, Nebraska, USA

Ian Maher, MD

Professor;

Director of Dermatologic Surgery;

Program Director, Mohs Surgery and Dermatologic Oncology Fellowship

Department of Dermatology

University of Minnesota;

Medical Director for Dermatology

M Health FairviewMinneapolis, Minnesota, USA

Shaun D. Mendenhall, MD

Assistant Professor of Surgery (Plastics) and Orthopaedic Surgery

Divisions of Plastic and Reconstructive Surgery and Orthopaedic Surgery

Children’s Hospital of Philadelphia

Perelman School of Medicine

University of Pennsylvania

Philadelphia, Pennsylvania, USA

Kira Minkis, MD, PhD

Associate Professor of Dermatology

Department of Dermatology

Weill Cornell Medicine

New York, New York, USA

Vineet Mishra, MD

Associate Professor of Dermatology

Department of Dermatology

University of California San Diego

San Diego, California, USA

Ardeshir Edward Nadimi, MD, FAAD

Mohs Micrographic Surgeon/Cutaneous Oncologist

Private Practice

Centreville, Virginia, USA

Kristina Navrazhina, PhD

MD-PhD Student, MS3

Department of Dermatology

Weill Cornell Medicine

New York, New York, USA

Sonal A. Parikh, MD

Staff Dermatologist and Mohs Surgeon

DermSurgery Associates – The WoodlandsThe Woodlands, Texas, USA

Parth Patel, MD

Dermatologist

Division of Dermatology

Montefiore Medical Center

Bronx, New York, USA

Vishal Anil Patel, MD, FAAD, FACMS

Director of Cutaneous Oncology

GW Cancer Center;

Director of Dermatologic Surgery

GW Department of Dermatology;

Associate Professor of Dermatology and Medicine/Oncology

George Washington University School of Medicine & Health Sciences

Washington DC, USA

Rebecca Lissette Quinonez, MD, MS

Research Fellow

Department of Research Division

Miami Dermatology and Laser Institute

Miami, Florida, USA

Evelyn R. Reed, MD

Plastic Surgery Resident

Division of Plastic Surgery

University of Utah

Salt Lake City, Utah, USA

Anthony Rossi, MD, FAAD, FACMS

Assistant Attending

Department of Medicine, Dermatology Service

Memorial Sloan Kettering Cancer Center

New York, New York, USA

Ethan T. Routt, MD

Staff Dermatologist and Mohs Surgeon

Golden Dermatology

Honolulu, Hawaii, USA

Madison E. Tattini, BS

Student

University of Utah

Salt Lake City, Utah, USA

Adam J. Tinklepaugh, MD

Assistant Professor of Medicine

Department of Dermatology

School of Medicine

University of Utah

Salt Lake City, Utah, USA

Anne Truitt, MD

Staff Dermatologist and Mohs Micrographic Surgeon

Skin Surgery Medical GroupSan Diego, California, USA

Gian Vinelli, MD

Mohs Surgeon

Department of Dermatology

Rochester Regional Health

Rochester, New York, USA

Jill Waibel, MD

Subsection Chief

Department of Dermatology

Baptist Hospital;

Clinical Voluntary Assistant ProfessorDr. Phillip Frost Department of Dermatology and Cutaneous SurgeryUniversity of Miami Miller School of Medicine Miami, Florida, USA

Jenna Wald, MD

Fellow

Department of Dermatology

St. Vincent’s Hospital

Indianapolis, Indiana, USA

Rachel Westbay, MD

Clinical Instructor

Mount Sinai School of MedicineNew York, New York, USA

Ramone F. Williams, MD, MPhil

Mohs Surgeon

Department of Dermatology

Harvard Medical School/Massachusetts General Hospital

Boston, Massachusetts, USA

Thomas J. Wright, MD

Plastic Surgery Resident

Division of Plastic Surgery

University of Utah

Salt Lake City, Utah, USA

Ashley Wysong, MD, MS

Professor and Founding Chair

Department of Dermatology

University of Nebraska

Omaha, Nebraska, USA

John A. Zitelli, MD

Adjunct Associate Professor

Departments of Dermatology, Otolaryngology, and Plastic Surgery

University of Pittsburgh Medical Center

Pittsburgh, Pennsylvania, USA

1 Facial, Scalp, Neck, Hands, Lower Extremities, and Genital Anatomy

Shauna Higgins, Marissa B. Lobl, and Ashley Wysong

Summary

This chapter discusses the anatomic areas of the face, scalp, neck, hands, lower extremities, and genitalia that are relevant to minimally invasive and surgical procedures performed for medical, oncologic, and cosmetic indications.

Keywords: dermatologic surgery cosmetic procedures anatomy danger zones

1.1 Introduction

Dermatologic surgery has expanded significantly with advances in minimally invasive and surgical procedures for medical, oncologic, and cosmetic indications. Procedurally relevant knowledge of anatomy is crucial to planning procedures, achieving optimal outcomes, and minimizing adverse events.

1.2 Head and Neck

1.2.1 Cosmetic Units and Facial Fat Pads

The face is broken down into a number of cosmetic subunits that share common characteristics such as skin color, texture, thickness, and presence or absence of hair.1 The cheek, temple, chin, and eyelids exist as their own well-defined units, with the nose and ear being subdivided into several smaller units (Fig. 1.1).1 At the borders of these units exist junction lines that include the melolabial fold that separates the cheek from the upper cutaneous lip, the mentolabial crease that divides the chin from the lower cutaneous lip, the nasolabial fold, the nasofacial sulcus, the hairline, and the jawline.2 These cosmetic units and their junction lines have a number of surgical implications. For example, junction lines generally serve as ideal locations to place incisions and closures.2 Surgical closures should also generally be confined to a single cosmetic subunit.1 When not possible, skin should be recruited from adjacent subunits and scar lines should be placed within junction lines or parallel to relaxed skin tension lines.1 When a defect involves several cosmetic subunits, consider repairing each subunit independently.1 Additionally, when the majority of a cosmetic subunit has been removed, for example, in tumor extirpation, consider removing the remaining portion and replacing the entire unit.1

Fig. 1.1 Cosmetic subunits of the face.2 (Reprinted with permission from Robinson JK, Arndt KA, LeBoit PE, Wintroub BU. Atlas of Cutaneous Surgery. Copyright Elsevier, 1995.)

Cosmetic subunits and their corresponding junctions also reflect variations in tissue composition and three-dimensional structure and contour.2 It is essential to thoroughly evaluate each patient for individual concavities, convexities, and transition zones. For example, variations in presence and density of fat pads such as the buccal and orbital pads can influence contour and may have implications for the depth and prominence of junction lines. Results of a 2018 study of 30 cadaver specimens revealed 7 bilateral distinct superficial (subcutaneous) facial fat compartments (when excluding the 3 subcutaneous compartments of the forehead): superficial nasolabial, superficial medial cheek, superficial middle cheek, superficial lateral cheek, jowl, and superficial superior temporal and superficial inferior temporal.3 Increased age was shown to have a significant influence on the inferior displacement of the superficial nasolabial and jowl compartments (p < 0.001).3 Several of these compartments are illustrated (Fig. 1.2). Wysong et al used magnetic resonance imaging scans of men and women to demonstrate measurable decreases in volume in the infraorbital area and the medial and lateral cheek areas, and concluded that facial soft tissue undergoes significant deterioration during the aging process and is different between men and women.3,​4,​5 Thus, this inevitably manifests in changes in volume and tissue laxity that can be addressed with injectable soft-tissue fillers. Of note, a 2018 cadaveric study utilized upright computed tomographic scanning to simulate the effects of gravity and reported that the superficial (subcutaneous) fat compartments behave differently upon injection of filling material.3 Whereas the inferior aspect of the nasolabial, middle cheek, and jowl compartments descended on filling, this effect was not observed for the medial or lateral cheek compartment or either of the superficial temporal compartments.3 Thus, in a clinical setting, care must be taken when injecting volumizing material into the subcutaneous plane.3 Targeting specific superficial fat compartments, such as the superficial nasolabial fat compartment, can result in an effect opposite to that desired: instead of reducing the nasolabial crease depth by the implantation of soft-tissue filler, a worsening of its appearance and a deepening of the crease can be noted.3 On the contrary, injections of soft-tissue filler into the superficial temporal compartments or the superficial medial cheek compartment (also called the malar fat pad) have been associated not with descent but with an increase in the local volume and an increase in the soft-tissue projection capable of inducing a lifting effect in the middle and/or lower face.3

Fig. 1.2 Superficial fat compartments of the face. (Image courtesy of Dr. Salvatore Piero Fundaro, Dr. Kwun Cheung Hau, and IMCAS Academy.)

The suborbicularis oculi fat (SOOF) has also been reported to be of particular clinical and procedural relevance, as nerves and vasculature such as the infraorbital and zygomaticofacial nerves course through the SOOF.6 The infraorbital nerve travels through the medial SOOF or deep medial cheek fat, whereas the zygomaticofacial nerve and artery travel through the lateral SOOF.6 Knowledge of this anatomy can help the surgeon accurately place nerve blocks and avoid bruising from bleeding complications.6 Further, because nerves travel within the medial and lateral SOOF, it is important to avoid performing multiple or crisscross passes with the needle in this plane, a technique that increases risk of nerve injury.6

1.2.2 Superficial Landmarks

The frontal, maxillary, zygomatic, and mandibular bones give rise to the prominent bony surface landmarks on the face that include the orbital rim, the zygomatic arch, the mastoid process, and the mentum (Fig. 1.3).2 On the orbital rim, several important foramina can be located. This includes the supraorbital and infraorbital foramina, with the former being located and palpable on the underside of the superior orbital rim 2.5 cm or approximately one thumb-breadth from midline.2 The supraorbital neurovascular bundle emerges from this foramen and includes the supraorbital artery, vein, and nerve.2 The infraorbital foramen can generally be located 1 cm below the infraorbital rim and is where the infraorbital artery, nerve, and vein emerge from the skull.2 The zygomatic arch serves as the prominent bone of the lateral cheek.2 Its posterior aspect helps define the superior pole of the parotid gland, the superficial temporal artery, and the temporal branches of the facial nerve.2 Of note, the temporal branch of the facial nerve is most superficial and vulnerable in the area around and just above the zygomatic arch. The mastoid process is the bony prominence palpated posterior and inferior to the postauricular sulcus.2 It serves as the landmark for the emergence of the facial nerve trunk from the stylomastoid foramen.2 After exiting the stylomastoid foramen, the trunk of the facial nerve travels through the nook of the neck for 1 to 1.5 cm, typically located midway between the cartilaginous tragal pointer of the external auditory canal and the posterior belly of the digastric muscle before entering the parotid gland. The mental protuberance of the mandible forms the prominence of the chin.2 The mental foramina, which are found on either side of the mandible along a vertical plumb line with the supraorbital and infraorbital foramina, are the route by which the mental nerve and artery exit the skull.2

Fig. 1.3 Bony landmarks of the face. (Reprinted with permission from Robinson JK. Surgery of the Skin. Copyright Elsevier, 2015.)

1.2.3 Muscles

There are two types of muscles in the face: the muscles of facial expression, also known as the mimetic muscles, and the muscles of mastication (Fig. 1.4). The muscles of facial expression are unique in that they are the only muscles to insert directly into the skin and interdigitate with other muscles. They can be described by the cosmetic subunits on which they act.

Fig. 1.4 Muscles of facial expression. (Reprinted with permission from Salasche SJ. Anatomy. In: Rohrer TE, Cook JL, Nguyen T, eds. Flaps and Grafts in Dermatologic Surgery. Copyright Elsevier, 2008.)

The muscles acting around the eyelids include the frontalis, corrugators, and orbicularis occuli.2 The frontalis muscle of the upper face/forehead acts as one unit to wrinkle the forehead and raise the eyebrows.2 It secondarily works to raise the eyelids via its interdigitation with the orbicularis oculi muscle.2 Injury to the frontalis muscle results in ipsilateral flattening of the forehead and often brow depression.2 The corrugator supercilii muscle is located underneath the bilateral eyebrows and is a common target of botulinum toxin injections.2 It has a large transverse head and an oblique head, the latter of which inserts into and depresses the skin of the medial brow to form the scowl lines of the glabella.2 The depressor supercilii has also been described as having a similar function.3 The orbicularis oculi encircles the orbital region and is described as having outer orbital and inner palpebral components.2 The palpebral component can be further divided into preseptal and pretarsal components.2 It interdigitates with the frontalis, corrugator supercilii, and procerus muscles. The inner orbital component acts to tightly close the eye and depress the eyebrow, whereas the outer palpebral portion acts to more gently close the eye and blink.2 It is innervated by temporal and zygomatic branches of the facial nerve.2

Muscles acting around the nose are minimal. The intrinsic muscle of the nose is the nasalis muscle, which functions to tense the skin over the dorsum and depress the septum to aid in deep inspiration. Superiorly, the procerus muscle extends down from the frontalis and aids in “scrunching” the nose. The levator labii superioris alaeque nasi also sends a few fibers to the lateral ala nasi and aids in dilating the nostril upon inspiration.

Muscles acting around the mouth include the orbicularis oris and the four lip elevators. The orbicularis oris muscle interdigitates with a number of other muscles of facial expression and functions to draw the lips together and also to pucker the lips. The four lip elevators are the levator labii superioris alaeque nasi, levator labii superioris, zygomaticus major, and zygomaticus minor. They all function to aid with smiling and other oral movements. The upper lip and the corner of the mouth are elevated by the risorius and the levator anguli oris muscles. Muscles involved in movement of the lower lip include the mentalis muscle, the depressor anguli oris, and the depressor labii inferioris muscle. The mentalis muscle helps wrinkle the skin of the chin, the depressor anguli oris depresses the corner of the mouth, and the depressor labii inferioris muscle depresses the lower lip.

1.2.4 Innervation

The primary nerves of the head and neck are the trigeminal (cranial nerve V), facial (cranial nerve VII), and spinal accessory nerve (cranial nerve XI). The trigeminal nerve provides motor innervation to the muscles of mastication, the facial nerve supplies the muscles of facial expression, and the spinal accessory nerve supplies the sternocleidomastoid (SCM) and trapezius muscles. Both the trigeminal and facial nerves are comprised of both sensory and motor nerve components, whereas the spinal accessory nerve is predominantly comprised of motor fibers. Motor nerves of the head and neck become increasingly superficial as they near their target muscle, making the lateral borders of these muscles sites of potential nerve injury.6 Sensory nerves generally course in neurovascular bundles with their respective arteries and veins and, relative to motor nerves, are more superficial and therefore more prone to injury and involvement by invasive skin cancers.7

The trigeminal nerve is a combined sensory and motor nerve, supplying sensory innervation to the face and anterior scalp and motor innervation to the muscles of mastication.7 It also sends secretory fibers to the lacrimal, parotid, and mucosal glands.7 Its three main sensory branches are the ophthalmic (V1), maxillary (V2), and mandibular (V3) branches (Fig. 1.5).7

The ophthalmic nerve exits the skull at the supraorbital foramen and divides into three main branches: the nasociliary, the lacrimal, and the frontal nerves.7 The nasociliary branch further divides into the infratrochlear nerve, which serves the medial canthus and the root of the nose, and the external nasal branch of the anterior ethmoidal nerve, which serves the dorsum, tip, and columella of the nose.7 Both the infratrochlear and external nasal branches are amenable for nerve block and regional anesthesia, which can be useful in dermatologic surgery. The lacrimal nerve supplies the lateral upper eyelid.7 The frontal nerve divides into the supratrochlear and supraorbital nerves.7 The supratrochlear nerve exits the supratrochlear notch about 1 cm lateral to midline to serve the upper eyelid and forehead/scalp.7 The supraorbital nerve exits the supraorbital foramen about 2.5 cm lateral to midline to also supply the upper eyelid and the forehead/scalp (Fig. 1.5).7

Fig. 1.5 The trigeminal nerve. (Image courtesy of Andy Trang, MD, Department of Psychiatry, University of Arizona, Tucson, Arizona, USA.)

The ophthalmic nerve emerges from the supraorbital foramen, a point 2.5 mm above the superior orbital margin, 23.9 mm from the facial midline, 25.89 mm from the nasion, and 30.08 mm from the frontozygomatic suture. The infraorbital foramen, from which the maxillary nerve emerges, is located 7.19 mm inferior to the infraorbital margin, approximately 45 mm from the nasion and 39.86 mm from the frontozygomatic suture. The mental nerve arises from the mental foramen, which is 20.4 mm inferior and 3.3 mm medial to the cheilions, as well as 25.8 mm lateral to the midline and 13.2 mm above the inferior mandibular margin.

The maxillary nerve exits the cranial cavity via the foramen rotundum and divides into three main branches: the infraorbital, zygomaticofacial, and zygomaticotemporal nerves.7 The infraorbital is the largest branch and exits the infraorbital foramen about 1 cm below the infraorbital rim in the mid-pupillary line.7,​8 It innervates the upper lip, medial cheek, lateral nose, and lower eyelid.7 Injury can be minimized by avoiding injections at the junction of the nasojugal crease and lid–cheek crease.6 The zygomaticofacial innervates the malar eminence, while the zygomaticotemporal innervates the temple region.7

The mandibular nerve is the largest of the three main trigeminal branches and is the only one to carry motor fibers, which innervate the muscles of mastication.7 Its three main branches are the auriculotemporal, buccal, and mental nerves.7 The auriculotemporal runs deep to the mandible and reaches the surface of the skin superior to the parotid gland, where it joins the superficial temporal artery and vein to supply sensory innervation to the lateral ear, temple, and parietal/temporal scalp.7 The buccal nerve provides sensory innervation to the cutaneous surface of the cheek in addition to the cheek mucosa and buccal gingiva and sulcus.9 It typically courses between the two heads of the pterygoid muscle, below the inferior portion of the temporalis muscle to ultimately join with the buccal branches of the facial nerve and pierce the posterior portion of the buccinator to branch extensively on the buccal surface of the cheek.9 On average, the buccal nerve was found in one cadaveric study to lie 3 cm lateral to the angle of the mouth.9 The mental nerve is at the highest risk of injury of all the mandibular nerve branches.1 It exits the mental foramen in the mid-pupillary line along with the mental artery and vein and innervates the chin and the inferior mucosal and cutaneous lip.7,​10,​11,​12 Whereas the mental branch and the infraorbital branch of the maxillary division are available for nerve block anesthesia, the buccal branch is not.7 The buccal branch is also not subjected to the same degree of iatrogenic injury, as the nerve is often protected by the buccal fat pad or the superficial musculoaponeurotic system (SMAS).13,​14

The facial nerve is a mixed sensory and motor nerve that may also be injured during a number of head and neck procedures such as tumor extirpation, liposuction, and parotid gland manipulation, thus requiring a strong knowledge of its course to mitigate negative surgical sequelae.15 The facial nerve exits the cranial cavity via the stylomastoid foramen inferior to the tragus of the ear.16 Its main branch is thus at risk of damage with removal with large and deep tumors near the inferior auricular attachment (Fig. 1.6). After exiting the cranial cavity, the facial nerve travels through the fat between the SCM and digastric muscles to the parotid within which it splits into a superior temporofacial and an inferior cervicofacial trunk.16 The trunk eventuates in the five major branches of the facial nerve that innervate the muscles of facial expression: the temporal, zygomatic, buccal, marginal mandibular, and cervical nerves.1 All five branches course deep to the parotid and are prone to injury during dermatologic surgery.16,​17,​18,​19,​20 Frequently used anatomic landmarks to identify the facial nerve and its branches include the tragal pointer, the tympanomastoid suture, the posterior belly of the digastric, the styloid process, and the retromandibular vein.15 The consistency of soft-tissue landmarks, however, is influenced by age, prior surgeries, intrinsic scarring, and the extent of the existing pathology.15 Bony landmarks have also been recently reported to be variable between the two sexes.15 Thus, one group has introduced a new anatomic triangle called Borle’s triangle for safer and more reliable operative identification of the trunk of the facial nerve, particularly during procedures involving manipulation of the parotid gland.15 The triangle is outlined by joining the inferior tip of the mastoid process, the superior border of the posterior belly of the digastric muscle, and the posterior border of the ramus of mandible with imaginary lines.15 The branches of the facial nerve most prone to clinically relevant iatrogenic injury are the temporal and marginal mandibular branches, as these represent terminal rami in approximately 85% of the population.1 The remaining branches of the facial nerve have numerous branches that minimize risk of permanent damage.1 The zygomatic nerve and its numerous branches innervate the orbicularis oculi muscle, the corrugator supercilii muscle, and the procerus muscle.21 The buccal nerve primarily innervates the levator labii superioris, the levator labii superioris alaeque nasi, buccinators, zygomaticus major and minor, levator anguli oris, and orbicularis oris muscles.22 The cervical branch innervates the platysmal muscle and is rarely a clinical consideration.7

Fig. 1.6 Main trunk of the facial nerve.

The inferior auricular attachment is in close proximity to the main trunk of the facial nerve. It courses anterior to the SCM, poster to the parotid fascia, and approximately 2 cm from the surface.

The course of the temporal branch of the facial nerve to the frontalis muscle can be approximated by a line connecting a point 0.5 cm below the tragus of the ear (near the inferior auricular attachment) to a point 2 cm above the lateral eyebrow.23 Schwember et al showed that the branch emerges from the parotid gland at a point that is approximately 29 mm from the intertragal notch, 59 mm from the palpebral lateral commissure, and 98 mm from the labial commissure.24 In a cadaveric study, Gosain et al found that it divides into an average of three several rami inferior to the zygomatic arch before reconnecting above the arch.25,​26 The posterior ramus was found to cross over the zygomatic arch at a range of 8 to 39 mm anterior to the external acoustic meatus.27 The anterior most ramus has been estimated to be found at a distance of 35.4 ± 4.6 mm from the root of the helix.28 According to Owsley et al, once the temporal branch of the facial nerve crosses the zygomatic arch, it begins to course more superficially.29 Within a few centimeters superior to the zygomatic arch, the galeal layer is replaced by fibrofatty tissue making the nerve more vulnerable to damage, particularly in procedures such as a temporoparietal fascia flap or a brow or facelift.1,​30,​31 In procedures in which the fascial plane has been exposed, however, if the plane easily moves side to side to the gloved finger, it is generally the superficial temporal fascia and the temporal nerve is likely intact.1 If the tissue is an immovable, tightly bound glistening membrane, the temporal fascia over the temporal muscle has likely been reached and the nerve has been cut.7 Damage to the temporal nerve results in paresis of the frontalis muscle with an ipsilateral inability to wrinkle the forehead or open the eye widely.7

The marginal mandibular branch of the facial nerve is responsible for supplying motor innervation to the depressor labii inferioris, depressor anguli oris, and mentalis muscles.32 It is particularly prone to injury given its superficial position and only partial coverage by the platysma at the jaw line and at the anterior border of the masseter muscle and given the frequency with which skin cancers and deep acne scars occur in these locations.7 Its course, however, has been reported to be highly variable.31,​33,​34,​35,​36,​37,​38 Several studies have found that its branches within the parotid gland course superficially to the retromandibular vein. Therefore, surgeons should be cautious when operating in the vicinity of the retromandibular vein, particularly in the superficial plane.39 In an anatomic study examining 40 cadavers, Basar et al found that the marginal mandibular branch exits from the parotid gland between 4.9 and 15.2 mm from the posterior border of the mandible and 0.2 and 15.1 mm from the inferior border of the mandible. Upon exiting the parotid gland, the nerve splits, giving off between one and four rami.31,​33,​34,​35 After exiting the parotid gland, the marginal mandibular branch courses roughly parallel to the mandible in an anteromedial direction before crossing the facial artery and migrating superiorly and anteromedially toward the target muscles of the lower lip and chin.31,​35 Most marginal mandibular rami are above the inferior border of the mandible once they have reached the facial artery, although it has been reported that it can cross the facial artery anywhere from 10.6 mm below to 30 mm above the inferior border of the mandible.31,​34 It is important to note that soft-tissue atrophy due to aging may result in inferior displacement of the nerve, a key consideration in elderly patients. A useful technique for avoiding marginal mandibular damage is placing incisions at least 3 cm or 2 fingerbreadths below the inferior border of the mandible, thus ensuring adequate clearance of the nerve. This technique is not infallible, as the nerve may remain within millimeters of the incision.

The spinal accessory nerve (CN XI) is responsible for providing motor innervation to the SCM and trapezius muscles. Iatrogenic injury to the accessory nerve is a well-documented complication of cutaneous oncological neck surgery and particularly neck dissections and lymph node biopsies.22 Accessory nerve injury is also a potential complication of cosmetic procedures such as rhytidectomy.40,​41,​42 The accessory nerve exits the SCM and enters the posterior triangle of the neck as it courses toward the trapezius. The posterior triangle of the neck is located between the SCM, trapezius, and clavicle. The spinal accessory nerve generally exits the SCM superior to Erb’s point at a range of 1 to 20 mm above it.43,​44,​45 This point is roughly 70 to 90 mm above the clavicle. After emerging from the SCM, the accessory nerve follows a posterolateral course within the posterior triangle toward the trapezius. At this point, the accessory nerve travels underneath the deep cervical fascia while remaining superficial to the levator scapulae muscle.43 Several superficial landmarks can be utilized in approximating the course of the accessory nerve. A useful method is to draw a triangle comprised of three points: Erb’s point, the inferior border of the upper one-third of the SCM, and the superior point of the lower one-third of the anterior trapezius (Fig. 1.7). Of note, the great auricular nerve originates from the cervical plexus, which also emerges from Erb’s point. It passes inferiorly to cross the SCM muscle about 6 cm inferior to the auditory canal, and courses just deep to the SMAS along the pathway of the external jugular vein.19 If dissection is done beneath the thick lateral adipose layer at the same depth past the boundary beyond which it lies deep to the SCM fascia, the dissection will proceed beneath the greater auricular nerve.6

Fig. 1.7 Superficial landmarks that may be used to approximate the course of the accessory nerve. A useful method is to draw a triangle comprised of Erb’s point, the inferior border of the upper one-third of the sternocleidomastoid (SCM), and the superior point of the lower one-third of the anterior trapezius.

1.2.5 Vasculature

The majority of the blood supply to the skull and its contents is derived from the common carotid artery, with the remainder coming from the vertebral artery46 (Fig. 1.8, Fig. 1.9). At the level of the fourth cervical vertebral body/hyoid bone, the common carotid artery divides into the external and internal carotid arteries.47 All vasculatures reaching the facial skin originate from either the external or internal branches of the common carotid artery.7,​48 The internal carotid artery system is predominantly dedicated to supplying the brain, although a few branches supply the head and neck region.7 The external carotid system predominantly supplies the lower face, temple, and posterior scalp.7 Its main branches are the inferior and superior labial arteries, facial artery, transverse facial, and infraorbital artery.7,​48

Fig. 1.8 Regions of the face supplied by the internal and external carotid arteries. (Reprinted with permission from von Arx T, Tamura K, Yukiya O, Lozanoff S. The Face: A Vascular Perspective. A literature review. Swiss Dent J. 2018; 128(5):382–392.)

Fig. 1.9 Vascular supply to the face. (Reprinted with permission from Salasche SJ. Anatomy. In: Rohrer TE, Cook JL, Nguyen T, eds. Flaps and Grafts in Dermatologic Surgery. Copyright Elsevier, 2008.)

The facial artery exits the submandibular gland at the anterior border of the masseter muscle at the jawline and curves around the inferior border of the mandible, where its pulse can be felt.47 It then ascends toward the medial eye, giving off the inferior labial artery within the orbicularis oris muscle en route.7 This artery in combination with the horizontal and vertical labiomental arteries comprise the majority of the perfusion to the lower lip.47 The horizontal labiomental artery also arises from the facial artery and is located below the inferior labial artery.47 The vertical labiomental artery is a branch of the submental artery.47 All three arteries form a vascular network in the subcutaneous and submucosal tissues of the lower lip with tiny vessels branching to the skin, mucosa, and muscles.47 In the upper lip, the superior labial artery is given off at the level of the commissure and follows a course similar to its lower lip counterpart.7,​47 Areas with minimal soft-tissue coverage over the blood supply, such as the lips, are at risk of skin necrosis even when minor injections are performed as injected volume may tamponade the vasculature and result in tissue ischemia.6 This creates the need for extreme care when augmenting small anatomic units that have thin soft-tissue units.6

After giving off the superior labial artery, the facial artery becomes known as the angular artery, at which point it courses toward the alar base, along the lateral aspect of the nose, and ultimately anastomoses with the dorsal nasal artery, a branch of the ophthalmic artery of the internal carotid that emerges from the medial orbit and runs down the nasal dorsum to anastomose with the lateral nasal branch of the facial artery on each side.7,​47 This supplies the skin of the medial eye angle, the lacrimal sac, and the bridge of the nose.47 The dorsal nasal artery (also known as the infratrochlear artery) also connects with the angular artery of the facial artery, and thus represents an anastomosis between the internal and external carotid artery systems.47 It runs downward along the side of the nose to supply the bridge of the nose and connect with the angular artery of the external carotid system.7 The anastomotic complex of the angular and dorsal nasal artery at the level of the medial canthus is an important vascular pedicle for the dorsal nasal or Rieger flap.18 Additionally, small vessels from the inferior alar branch supply the alar base and nostril floor, whereas small twigs from the superior alar branch perfuse the nasal dorsum and superior rim of the nostril.47 The external nasal artery, a terminal branch of the anterior ethmoidal artery, surfaces at the junction of the nasal bone and lateral nasal cartilage. This artery supplies the inferolateral areas of the nose and may also anastomose with the lateral nasal artery.47

Understanding the topography of the blood vessels distributed around the nasolabial fold region is essential for ensuring the safety of dermal filler injections into the area and avoiding vascular complications that include skin necrosis, embolism, or even blindness.49 In patients with a congenital or acquired nondominant facial artery in the nasolabial region, there is a risk of damaging the thickened infraorbital artery during deep injections into the skin and subcutaneous tissue.49 Superficial injections are thus recommended for removing rhytids of the nasolabial fold.49 Injection of dermal filler materials into the deep dermis is only recommended after preoperatively checking for contact of the needle or cannula with the bone49 (Fig. 1.10).

Fig. 1.10 High-risk areas for iatrogenic damage to the infraorbital artery.49 The infraorbital artery is particularly vulnerable to injury in zones V and VI and in the nasolabial fold.49 (Reprinted with permission from Kim HS, Lee KL, Gil YC, et al. Topographic anatomy of the infraorbital artery and its clinical implications for nasolabial fold augmentation. Plast Reconstr Surg. 142(3): 273e–280e. Copyright Wolters Kluwer, 2018.)

Additional branches of the external carotid include the postauricular artery, the occipital artery, the superficial temporal artery, and the internal maxillary artery.7 The postauricular artery curves around the styloid process to innervate the posterior ear and portions of the adjacent scalp above and behind the ear.7 The occipital artery courses posteriorly and superiorly with sensory nerves between the trapezius and the SCM muscles to supply the posterior scalp. After giving off the facial and occipital arteries, the external carotid artery divides into its two terminal branches, the superficial temporal artery and the internal maxillary artery.7 The superficial temporal artery supplies a large proportion of the facial skin including the lateral forehead, temple, zygoma, and ear.47 It arises within the parotid gland approximately 1 cm anterior to the ear.47 Its branches are numerous and include the frontal and parietal branches and the posterior auricular artery. In one study of 26 adult cadaveric hemifaces, the superficial temporal artery bifurcated into frontal and parietal branches on average 3 cm superior to the tragus.47 The posterior auricular artery also branches from the superficial temporal artery to supply the posterior auricle and the scalp posterior to the auricle.6 The posterior auricularis muscle can be used as a topographic landmark for the posterior auricular artery.6 To avoid direct injury to the frontal branch, Koziej et al suggest performing soft-tissue filler injections of the temporal region from lateral to medial in the superficial subcutaneous plane just below the dermis.50 Further, it is necessary to remember to stay above the temporoparietal fascia or just above the periosteum so as not to inject filler into the middle temporal vessels.50

Additionally, the transverse facial artery branches from the superficial temporal artery and has been described to supply a large region of the lateral malar face, including the SMAS. The SMAS is an organized fibrous network composed of the platysma muscle, parotid fascia, and the fibromuscular layer covering the cheek.19 It divides the deep and superficial adipose tissue of the face, lies inferior to the zygomatic arch and superior to the muscular belly of the platysma, and integrates with the superficial temporal fascia and frontalis muscle superiorly, and with the platysma muscle inferiorly.19 The SMAS has been described as a central tendon for coordinated muscular contraction of the face.19 Because the transverse facial artery runs directly through the SMAS, there is a risk of transection of this vessel during elevation of the SMAS during certain facial procedures.19 Thus, care must be taken to avoid harming not just the transverse facial artery but also other neurovascular structures that lie in close proximity to the area.19 Further, the SMAS plays a key role in rhytidectomy, commonly known as the facelift procedure.19 During face-lifting, the SMAS is surgically manipulated by tightening and suspending the facial muscles through various flap dissections and surgical approaches.16 Of note, although many neurovascular structures course deep to the SMAS, only sensory branches from the trigeminal nerve course superficial to the SMAS.19

The internal maxillary artery branch of the external carotid predominantly runs inside the mouth and nose but supplies terminal vessels that exit the infraorbital and mental foramen with their respective veins and sensory nerves to supply the maxilla region of the face.7,​48

Although the lateral forehead is supplied by the frontal branch of the superficial temporal artery, branches of the ophthalmic artery, the supraorbital and supratrochlear arteries, perfuse the remainder of the forehead.47 These vessels exit their foramens and travel deeply in the subcutaneous fat above the frontalis fascia and then over the galea aponeurotica.7 The supratrochlear artery emerges from the superomedial orbit close to a vertical line at the medial palpebral commissure.47 It supplies the upper eyelid along with the lacrimal, and supraorbital arteries.47 The lower eyelid is supplied by the palpebral branch of the infraorbital artery as well as by the lateral and medial palpebral branches from the lacrimal and supratrochlear arteries, respectively.47

The main artery of the chin is the mental artery, one of the terminal branches of the inferior alveolar artery.47 The submental artery extends vertically from around 3 cm below the mandibular border to around 1 cm below the oral commissure, and horizontally from around 1.5 cm posterior to the commissure to around 2 cm anterior of the SCM muscle.47

Many veins in the face accompany their corresponding arteries although there are some exceptions to the rule (inferior ophthalmic vein, retromandibular vein).47

The facial vein, responsible for the draining of the eyelids, nose, lips, cheek, and mental region, demonstrates a consistently more posterior course relative to the facial artery, traveling on average 15 mm posterior to the facial artery (range: 5–30 mm).47 The artery and vein also lie in close proximity at the lower border of the mandible until they reach the midface muscles of facial expression where the artery assumes a more tortuous path, while the vein travels in a direct path from the medial canthus to the lower mandible.47 The venous drainage of the middle forehead and upper eyelid occurs via the angular vein to the ophthalmic veins (superior and inferior) that communicate with the cavernous sinus.47 Venous drainage of the midface occurs via the infraorbital vein and pterygoid plexus that also has connections to the cavernous sinus.47 The venous blood from the chin is returned via the mental and inferior alveolar veins to the maxillary vein.47

The retromandibular vein is one of the facial veins that does not generally run with its corresponding artery. It has an anterior and an posterior division.47 The posterior division merges with the posterior auricular vein to form the external jugular vein, whereas the anterior division merges with the facial vein and drains into the internal jugular vein.47 There has also been a report of an unusual course of the right common facial vein parallel to the course of the external jugular vein, emptying into the ipsilateral subclavian vein in the lateral neck triangle behind the posterior border of the SCM muscle in a 78-year-old male cadaver.51 Such course may be hazardous for surgical procedures in the region given the high risk of profuse hemorrhage from any injury of the vessel.51

Of note, above the zygomatic arch, the neurovascular bundles containing major arteries and veins all course in the deep subcutaneous plane above the fascia or muscles of facial expression.7 Below the arch, however, the vessels are typically within the mimetic muscles and do not travel with major sensory nerves.7

1.2.6 Special Considerations

Aesthetic and reconstructive surgery of the face performed in different races and ethnicities may require special consideration of the variations in anatomy. In the Asian population, for example, orbital and periorbital structures may vary from those in Caucasian patients. Of note, although “Asian” refers to anything related to the continent of Asia and although the Asian population is comprised of various groups such as Chinese, Indian, Middle Eastern, and Southeast Asian, the “Asian eyelid” generally refers to the morphology of eyelids found in native Chinese and those of Chinese descent.52

There are generally six types of Asian eyelids that include the single eyelid, the low eyelid crease, and the double eyelid (Fig. 1.11).52 The double eyelid has a fold, which is formed by the supra-crease of overhanging skin when the eyes are open.52,​53,​54 The epicanthal fold is unique to the Asian eyelid and is defined as a skin fold from the upper eyelid that covers the inner angle of the eye. The four types of epicanthal fold according to Johnson’s classification are demonstrated in Fig. 1.12.52 A study in a Korean cohort found that the prevalence of the epicanthal fold was 86.7%, although the percentage of Asians with a reported epicanthal fold varies from 40 to 90% in the literature.55 The epicanthal fold is composed of an outer skin lining, a core structure of muscular fibers and fibrotic tissue, and an inner skin lining. Dermatologists should also be aware of the surgical anatomy of this region when performing surgical procedures, such as the epicanthoplasty, or laser procedures on epicanthoplasty scars. When performing surgery involving the epicanthal folds, the muscular and fibrotic tissue should also be removed or reconstructed.55

Fig. 1.11 Asian eyelid morphologies are categorized into six types. (a) Single eyelid (no visible lid crease). (b) Low eyelid crease (low-seated, nasally tapered, including hidden fold). (c) Double eyelid crease, in-fold type: the height of the upper lid crease is lower than the epicanthal fold. (d) Double eyelid crease, on-fold type: the height of the crease is right on the epicanthal fold. (e) Double eyelid crease, out-fold type: the height of the crease is higher than the epicanthal fold. (f) Double eyelid crease, out-fold type without an epicanthal fold.52

Fig. 1.12 The four types of epicanthal fold according to Johnson’s classification. (a) Epicanthus tarsalis. (b) Epicanthus supraciliaris. (c) Epicanthus palpebralis. (d) Epicanthus inversus.52

Additionally, variations in measurements of the Asian eyelid compared to the Caucasian eyelid are particularly relevant to blepharoplasties and eyebrow lifts as several studies suggest that the crease height is required to aid the surgeon in the decision of how much extra skin to excise during blepharoplasties.56,​57 The eyelid crease height is 8 to 10 mm in Caucasians and 6.5 ± 0.7 mm in Asians. The upper tarsal height is 11.3 ± 1.7 mm in Caucasians and 9.2 ± 0.8 mm in Asians. The intercanthal distance is 25 to 30 mm in Caucasians and 35.55 ± 2.75 mm for Asian females and 37.51 ± 2.92 mm for Asian males.58

1.3 Hand

Dermatologic surgery on the hands is performed for extirpation of cutaneous malignancies and in the context of cosmetic procedures. Surgery of the nail bed region is also common, yet complicated. Knowledge of the intricacies of the hand, nail, and superficial anatomy is critical to optimizing patient outcomes following hand surgery.

1.3.1 Innervation

The three major nerves that supply the hand are the ulnar, median, and radial nerves (Fig. 1.13). The median nerve passes through the carpal tunnel to enter the hand.59 After entering the hand, it gives off four branches: the recurrent, lateral, medial, and palmar cutaneous branches.59 The recurrent branch of the median nerve runs laterally beyond the flexor retinaculum and dives under the palmar aponeurosis to innervate the thenar muscles (except adductor pollicis and the deep head of flexor pollicis brevis).59 This nerve is commonly injured during procedures involving structures of the wrist and carpal tunnel.60,​61 Given its role in maintaining a functional hand grip, care should be taken to avoid injury during surgery. The lateral branch of the median nerve innervates the first lumbrical and provides sensation to the thumb and radial half of the second digit.59 The medial branch of the median nerve runs medially along the second through fourth digits, supplying the second lumbrical and skin of the second through fourth digits.59 The palmar cutaneous branch of the median nerve is given off proximal to the flexor retinaculum and supplies sensation to the center of the palm.59 To perform a median nerve block, utilize the palmaris longus tendon, which runs just superior to the median nerve.62 The palmaris longus tendon can be palpated just lateral to the center of the anterior wrist.62 Position the needle just medial to palmaris longus (Fig. 1.14).62

Fig. 1.13 Sensory innervation of the hand is provided by the median, radial, and ulnar nerves. (Reprinted with permission from Bolognia JL, Vandergriff TW. Dermatology. Copyright Elsevier, 2018.)

Fig. 1.14 Position for median nerve block. Place the needle just medial to the palmaris longus tendon, approximately 2.5 cm proximal to the wrist crease.

The ulnar nerve enters the hand through Guyon’s canal, alongside the ulnar artery.59 The ulnar nerve divides into deep and superficial branches as the nerve passes by the hamate and pisiform.59 The superficial branch of the ulnar nerve divides into two common palmar digital nerves and supplies the palmaris brevis and sensation to the ulnar side of the hand.59 The deep branch of the ulnar nerve supplies the hypothenar muscles as well as the adductor pollicis and the deep head of the flexor pollicis brevis.59 The palmar cutaneous branch of the ulnar nerve branches off from the ulnar nerve in the middle of the forearm, pierces the deep fascia, and supplies the skin at the base of the medial palm.59 The dorsal branch of the ulnar nerve arises in the forearm, passes under the flexor carpi ulnaris, penetrates the deep fascia, and branches off to supply the medial aspect of the dorsum of the hand, the proximal part of the fifth digit, and the medial part of the fourth digit.59 To perform an ulnar nerve block, utilize the flexor carpi ulnaris tendon, which runs just superior to the ulnar artery and nerve, the ulnar artery being palpable where it crosses the medial anterior wrist.62 Position the needle parallel to the plane of the palm and deep to the flexor carpi ulnaris (Fig. 1.15).62

Fig. 1.15(a, b) Position of the needle for ulnar nerve block. place the needle parallel to the plane of the palm and deep to the flexor carpi ulnaris (FCU).

The radial nerve and its branches supply the extensors of the forearm and hand. The superficial branch of the radial nerve branches off in the cubital fossa and emerges under the brachioradialis, piercing the deep fascia and dividing into two branches.59