NORMAL ANATOMY OF THE SKIN
Normal Skin Histology
- Epidermis
- Outer layer
- Five strata: (1) Corneum, (2) lucidum, (3) granulosum, (4) spinosum, and (5) basale (mnemonic: Californians Love G-String Bikinis)
- Predominant cells: Keratinocyte, melanocytes, Langerhans cells, and Merkel cells.
- Epidermal-dermal junction
- Rete pegs: Epidermal projection into dermal layer
- Papillae: Dermal projection into epidermal layer (vascularized).
- Dermis
- Predominant cells: Fibroblast, histiocytes, monocytes, lymphocytes, and Langerhans cells
- Papillary layer: Loose connective tissue, and small vessels/nerve endings
- Reticular layer: Dense connective tissue, blood vessels, hair follicles, sweat glands, lymphatics, nerves, sebaceous glands, and apocrine/eccrine glands.
- Hypodermis (subcutaneous layer)
- Contains fat and fibrous tissue
Variations in Skin Thickness in the Head and Neck
The measure of skin thickness can help guide reconstructive choices by matching similar skin thickness between donor and recipient sites (Table 1).4
Skin Biomechanical Properties
The four fundamental biomechanical properties of the skin are the following:5
- Stress: Force applied per cross-sectional area of the skin.
- Strain: Change in length divided by the original length of the given tissue to which a force is applied.
- Creep: Increase in strain applied to skin when it is under constant stress. Creep can occur over a brief amount of time (minutes) and is due to the extrusion of fluid from the dermis and breakdown of the dermal framework.
- Stress relaxation: Decrease in stress on skin when it is held in tension at a constant strain for a given period of time.
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SKIN INCISION PLACEMENT
Relaxed Skin Tension Lines
Incisions parallel to relaxed skin tension lines (RSTL) result in the most favorable scars. The RSTLs are fine lines on the facial skin that are formed by the action of the underlying muscles and as a result, are perpendicular to them (Fig. 1).6
Facial Subunit Principle
The units and subunits are based on skin thickness, color, texture, and underlying structural contour. Precise planning of surgical incisions and reconstructions require analysis of the entire unit or subunit. Incisions within unit or subunit borders result in the most favorable scars.
The original 14 esthetic units include:7
- Nasal unit: Tip subunit, columellar subunit, right and left alar base subunits, right and left alar side wall subunits, dorsal subunit, and right and left dorsal side wall subunits
- Eye lid units: Lower lid unit, upper lid unit, lateral canthal subunit, and medial canthal subunit
- Cheek unit: Medial subunit, zygomatic subunit, lateral subunit, and buccal subunit
- Upper lip unit: Philtrum subunit, lateral subunit, and mucosal subunit
- Lower lip unit: Central subunit, and mucosal subunit
- Mental unit
- Auricular unit: Helical subunit, antihelical subunit, and triangular fossa subunit, conchal subunit, and lobe subunit.
- Neck unit.
WOUND CLOSURE
Different Suture Techniques and their Characteristics
Good suturing technique should eliminate dead space in subcutaneous tissues, and minimize tension that causes wound separation. Below are the steps required in obtaining a fine line scar:8
- Minimizing damage to the skin edges with a traumatic technique
- Tension free closure with
- Wound edge eversion
- Prompt removal of suture material
- Clean non-infected wound
- Use of non-absorbable synthetic sutures
Table 2 outlines the most commonly employed suture techniques and their most common indications.9–13
SKIN APPROXIMATION MATERIAL REFERENCES
Suture Materials, Advantages, and Disadvantages
Evidence Base for Suture Removal
On the face and ears, sutures can be removed within 5–7 days, with eyelid sutures being removed in 3–5 days.11 Neck sutures are removed within 7 days and scalp sutures in 7–10 days.11
WOUND HEALING
The normal wound healing stages have been described in Table 6.
Most Common Causes of Impaired Wound Healing
Wound healing is the result of interactions among cytokines, growth factors, blood, and the extracellular matrix. The cytokines promote healing by various pathways such as stimulating the production of components of the basement membrane, preventing dehydration, increasing inflammation and the formation of granulation tissue. These pathways are affected by various local and systemic factors. Table 7 summarizes the most common causes of impaired healing.17, 18
DRESSINGS AND PROBLEM WOUNDS
Dressing Selection and Wound Management Principles
Based on the wound type, suitable dressing material must be used. In general, modifiable characteristics of the optimal wound environment is moist, sterile, and warm.19 To obtain a moist environment, dry wounds should be moistened and excessively exudative wounds should be dried up.
Common Dressings
Negative Pressure Therapy20
Negative pressure wound therapy (NPWT) has been shown to accelerate healing. It has become increasingly valuable in the management of chronic and acute wounds, contaminated wounds, traumatic tissue loss, surgical dehiscence, ulcers from vascular insufficiency, fistulas, and other indications.5
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Its effect on the wound bed are the following: Extraction of exudate from the wound bed, decrease of interstitial edema, increase in vascularity, promotion of granulation formation, decrease in bacterial burden, stimulation of fibroblast and endothelial cell proliferation, and mechanical contracture of the wound bed.
Head and neck evidence: Negative pressure wound therapy in head and neck surgery is safe and has potential to be a useful tool for complex wounds in patients with a compromised ability to heal.
Hyperbaric Oxygen Therapy
Hyperbaric oxygen therapy (HBOT) is defined by the Undersea and Hyperbaric Medical Society (UHMS) as a treatment in which a patient intermittently breathes 100% oxygen while the treatment chamber is pressurized to a pressure greater than sea level (1 atmosphere absolute, or 1 ATA).
The mechanisms of HBOT when relative to wound healing are:21
- Hyperoxygenation
- Vasoconstriction (to reduce edema)
- Angiogenesis
- Fibroblast proliferation and collagen synthesis
- Leukocyte oxidative killing
- Toxin inhibition and antibiotic synergy
Indications of hyperbaric oxygen therapy illustrated in Box 1 and and complications/contraindications illustrated in Table 9.24
REFERENCES
- Moore KL, Persaud TVN, Torchia MG. Before we are born: essentials of embryology and birth defects, 9th edition. Philadelphia, PA: Elsevier/Saunders; 2016. p. 361.
- Carlson BM. Human embryology and developmental biology, 5th edition. 2014, Philadelphia, PA: Saunders/Elsevier; 2014. p. 506.
- Burns T, Breathnach S, Cox N, et al. Rook's Textbook of Dermatology, 8th edition. Chichester, West Sussex, UK; Hoboken, NJ: Wiley-Blackwell; 2010.
- Ha RY, Nojima K, Adams WP Jr, et al. Analysis of facial skin thickness: defining the relative thickness index. Plast Reconstr Surg. 2005;115:1769–73.
- Gaboriau HP, Murakami CS. Skin anatomy and flap physiology. Otolaryngol Clin North Am. 2001;34:555–69.
- Johnson JT, Rosen CA, Bailey BJ. Bailey's Head and Neck Surgery—Otolaryngology, 5th edition. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2014.
- Fattahi TT. An overview of facial aesthetic units. J Oral Maxillofac Surg. 2003;61:1207–11.
- Thorne C, Gurtner GC, Chung K, et al. Grabb and Smith's Plastic Surgery, 7th edition. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2014. p. 1030.
- Kudur MH, Pai SB, Sripathi H, et al. Sutures and suturing techniques in skin closure. Indian J Dermatol Venereol Leprol. 2009;75:425–34.
- Moy RL, Waldman B, Hein DW. A review of sutures and suturing techniques. J Dermatol Surg Oncol. 1992;18:785–95.
- Zachary CB. Basic cutaneous surgery: a primer in technique. Practical Manuals in Dermatologic Surgery. New York: Churchill Livingstone, 1991. p. 134.
- Swanson NA. Atlas of cutaneous surgery, 1st edition. Boston: Little, Brown; 1987. p. 177.
- Janis JE. Essentials of plastic surgery, Second edition. St. Louis, Missouri Boca Raton: Quality Medical Publishing, CRC Press/Taylor & Francis Group; 2014. xxv, p. 1336.
- Singer AJ, Clark RA. Cutaneous wound healing. N Engl J Med. 1999;341:738–46.
- Gurtner GC, Werner S, Barrandon Y, et al. Wound repair and regeneration. Nature. 2008;453:314–21.
- Guo S, Dipietro LA. Factors affecting wound healing. J Dent Res. 2010;89:219–29.
- Thomas Hess C. Checklist for factors affecting wound healing. Adv Skin Wound Care. 2011;24:192.
- Dhivya S, Padma VV, Santhini E. Wound dressings—a review. Biomedicine (Taipei). 2015;5:22.
- Asher SA, White HN, Golden JB, et al. Negative pressure wound therapy in head and neck surgery. JAMA Facial Plast Surg. 2014;16:120–6.
- Kindwall EP. Hyperbaric medicine practice, 2nd edition. Flagstaff, Ariz: Best Publishing. Company; 1995. p. 692.
- Young T. Hyperbaric oxygen therapy in wound management. Br J Nurs. 1995;4:796, 798-803.
- Broussard CL. Hyperbaric oxygenation and wound healing. J Vasc Nurs. 2004;22:42–8.
- Plafki C, Peters P, Almeling M, et al. Complications and side effects of hyperbaric oxygen therapy. Aviat Space Environ Med. 2000;71:119–24.
Self-Assessment Exercise
Q 1. Define stress relaxation.
Ans: A decrease in stress on skin when it is held in tension at a constant strain for a given period of time.
Q 2. Name 5 local factors of impaired wound healing.
Ans:
- Infection
- Radiation
- Hematoma
- Wound desiccation
- Ischemia.
Q 3. Name all nasal subunits.
Ans:
- Tip subunit
- Columellar subunit
- Right and left alar base subunits
- Right and left alar side wall subunits
- Dorsal subunit
- Right and left dorsal side wall subunits.
Q 4. Where are the thickest and thinnest skin sites of the face?
Ans: Thinnest: upper eyelid; Thickest: nasal tip.
Q 5. Name three possible complications of HBOT.
Ans: Pneumothorax, ARDS, middle ear barotrauma.
Multiple Choice Questions
Q 1. Which of the following statements is TRUE regarding the different Skin Line Types?
- Relaxed Skin Tension Lines (RSTL) usually run perpendicular to the wrinkles
- Relaxed Skin Tension Lines (RSTL) usually run parallel to the contraction of muscles
- Langer's lines are relaxation creases found in the skin of cadavers
- Facial Langer's lines coincide with the facial wrinkle lines.
Ans: C. Langer's lines are relaxation creases found in the skin of cadavers
Q 2. Which of the following nasal subunits has a thick, immobile and sebaceous skin?
- The lobule
- The dorsum
- The sidewall
- The ala
Ans: A. The lobule
Q 3. Which of the following statements is TRUE about external nasal subunits?
- Any subunit defect greater than 30% should be enlarged to occupy the entire subunit
- The ala refers to the skin and soft tissue overlying the lateral crura of the lower lateral cartilages
- The tip-defining point indicates the base of the soft triangle of the nose
- The sill comprises the most posterior aspect of the nostril rim
Ans: D. The sill comprises the most posterior aspect of the nostril rim
Q 4. Which of the following nasal areas has the THINNEST skin?
- Nasion
- Rhinion
- Supratip
- Columella
Ans: D. Columella
Q 5. In tissue expanders, the INCREASE in skin surface when the skin is under constant stress is related to:
- Viscoelasticity
- Creep
- Extensibility
- Stress relaxation
Ans: B. Creep
Q 6. Which of the following statement regarding BIOLOGIC CREEP is FALSE?
- It involves an overall increase in mitotic activity
- It involves a displacement of fluids and the collagen fibers are realigned
- It involves an increase in surface area
- It involves permanent changes in the microanatomy of tissue
Q 7. Which of the following terminology is related to “ a DECREASE in the force necessary on the skin when is held in a contant stretch over a given period of time”.
- Viscoelasticity
- Creep
- Extensibility
- Stress relaxation
Ans: D. Stress relaxation
Q 8. Which of the following cell types is MOST predominantly seen in the epidermis?:
- Langerhan's cells
- Keratinocytes
- Melanocytes
- Merkel's cells
Ans: B. Keratinocytes
Q 9. Which of the following cells have THE MOST important ROLE in the inflammatory phase of wound healing?
- Macrophages
- Lymphocytes
- Monocytes
- Neutrophils
Ans: A. Macrophages
Q 10. Which of the following cells are FIRST TO APPEAR in the wound healing process?
- Polymorphonuclear leukocytes
- Macrophages
- Lymphocytes
- Endothelial cells
Ans: A. Polymorphonuclear leukocytes
Q 11. Which of the following tissue adhesives is the LEAST histotoxic?
- Butyl-2-cyanoacrylate
- Methyl-α-cyanoacrylate
- Octyl-8-cyanoacrylate
- Fibrin glues
Ans: D. Fibrin glues
Q 12. Which of the following cells synthesizes COLLAGEN?
- Keratinocytes
- Melanocytes
- Langerhans’ cells
- Fibrocytes
Ans: D. Fibrocytes
Q 13. Which of the following cells are implicated in the production of TROPOCOLLAGEN UNITS?
- Macrophages
- Fibroblasts
- Lymphocytes
- Endothelial cells
Ans: B. Fibroblasts
Q 14. Which of the following cell types have been RELATED to the mediation of immunologic responses within the skin?
- Keratinocytes
- Langerhans’ Cells
- Merkel's Cells
- Melanocytes
Ans: B. Langerhans’ Cells
Q 15. Which one of the following will promote FASTER reepithelialization during wound healing?
- Desiccation
- Occlusive wound dressing
- Triamcinolone acetonide ointment (0.1%)
- Anticoagulants
Ans: B. Occlusive wound dressing
Q 16. Which of the following mineral DEFICIENCIES is clinically important in wound healing?
- Zinc
- Iron
- Calcium
- Copper
Ans: A. Zinc
Q 17. Which of the following suture materials will produce LESS tissue reaction when used on the face?
- Chromic catgut
- Vicryl
- Silk
- Nylon
Ans: D. Nylon
Q 18. The main DISADVANTAGE in applying cyanoacrylate tissue adhesive to the skin is its:
- Erythema effect
- Foreign body effect
- Local histotoxicity effect
- Blister effect
Ans: C. Local histotoxicity effect
Q 19. Which of the following suture materials will induce the MOST inflammatory tissue reaction?
- Nylon
- Vicryl
- Chromic catgut
- Prolene
Ans: C. Chromic catgut
Q 20. In which layer of the skin are the “melanocytes” found?
- The basal cell layer
- The prickle cell layer
- The granular cell layer
- The stratum lucidum layer
Ans: A. The basal cell layer
Q 21. The corpuscles of “Vater-Pacini”mediate the sensation of:
- Pressure
- Pain
- Temperature
- Touch
Ans: A. Pressure
Q 22. Which of the following is TRUE regarding the phases and order of wound healing?
- Inflammation, proliferation and differentiation
- Inflammation, proliferation and maturation
- Proliferation, remodeling and differentiation
- Proliferation, remodeling and contraction
Ans: B. Inflammation, proliferation and maturation
Q 23. At the end of the remodeling phase of wound healing the scar HAS approximately:
- 20% of the tensile strength of nonwounded normal skin
- 40% of the tensile strength of nonwounded normal skin
- 60% of the tensile strength of nonwounded normal skin
- 80% of the tensile strength of nonwounded normal skin
Ans: D. 80% of the tensile strength of non-wounded normal skin
Q 24. Which of the following is the CORRECT TIMING for the appearance of the fibroblasts in the process of wound healing?
- 24 hours
- 3 days
- 7 days
- 10 days
Q 25. In the wound healing process granulation tissue forms at which of the following points?
- 24 hours
- 48 hours
- 4 days
- 7 days
Ans: C. 4 days
Q 26. HOW LONG does the tensile strength chromic gut last?
- 1 week
- 2 weeks
- 4 weeks
- 6 weeks
Ans: B. 2 weeks
Q 27. When is the REMODELING PHASE in wound healing COMPLETE?
- 3 months
- 6 months
- 10 months
- 12 months
Ans: D. 12 months
Q 28. At the end of the inflammatory phase of wound healing (one week after closure) the wound HAS what percentage of unwounded normal skin?
- 10%
- 30%
- 50%
- 70%
Ans: A. 10%
Q 29. Which of the following vitamins, supplements or medications WILL NOT INTERFERE with blood clotting?
- St. John's wort
- Vitamin B
- Ginkgo biloba
- Naproxen
Ans: B. Vitamin B
Q 30. Which of the following statements about WOUND HEALING is TRUE?
- Polymorphonuclear leukocytes appear after 72 hours
- Macrophages are predominant in the first 36 hours
- Granulation tissue appears on day # 4
- Wound contraction initiates 3 weeks after injury
Ans: C. Granulation tissue appears on day # 4
Q 31. When will FAST ABSORBING SURGICAL GUT LOOSE virtually ALL TENSILE STRENGTH?
- After 48 hours
- After 72 hours
- After 5 days
- After 7 days
Ans: C. After 5 days
Q 32. In which of the following facial areas are SILK SUTURES INDICATED?
- Eyelid margin
- Cheek
- Forehead
- Ear
Ans: A. Eyelid margin
Q 33. Which of the following cells plays a KEY ROLE in the coagulation phase of wound healing?
- Platelets
- Neutrophils
- Lymphocytes
- Macrophages
Ans: A. Platelets
Q 34. When does PEAK wound contraction occur?
- 5 days
- 7 days
- 14 days
- 21 days
Ans: C. 14 days
Q 35. Which of the following cellular components in wound healing is responsible for the CONTRACTION PHASE?
- Macrophages
- Fibroblasts
- Myofibroblasts
- Lymphocytes
Ans: C. Myofibroblasts
Q 36. When in the healing process does a wound achieve the Tensile Strength of preinjured tissue?
- 6 months
- 1 year
- 2 years
- Never
Ans: D. Never
Q 37. Which of the following properties enables this condition, related to the skin: “ the ability to retain the shape obtained by stretching when the deforming force is gone”?
- Tensile strength
- Elasticity
- Plasticity
- Memory
Ans: C. Plasticity
Q 38. Which of the following nonabsorbable sutures has the MOST tissue reaction?
- Silk
- Polypropylene (prolene)
- Polyester (mersilene)
- Stainless steel
Ans: A. Silk
Q 39. Which of the following statements about the suture material PLAIN CATGUT is FALSE?
- It is derived from the submucosal layer of sheep intestine
- It elicits a low inflammatory response
- It loses its tensile strength by 7 days
- It increases its tensile strength up to 21 days by treating the catgut with chromium salts (chromic gut)
Ans: B. It elicits a low inflammatory response
Q 40. Which of the following substances is produced by THE LYMPHOCYTES in the immune response to wound repair?
- FGF (Fibroblast growth factor)
- IGF-1(Insulin-like growth factor)
- PDGF (Platelet derived growth factor)
- TGF-beta (Transforming growth factor-beta)
Ans: D. TGF-beta (Transforming growth factor-beta)
Q 41. The Epidermal Growth Factor (EGF) is derived from:
- Platelets
- Lymphocytes
- Macrophages
- Neutrophils
Q 42. Which of the following is the source of Interferon?
- Fibroplasts and lymphocytes
- Macrophages and neutrophils
- Masts cells and lymphocytes
- Neutrophils and lymphocytes
Ans: A. Fibroplasts and lymphocytes
Q 43. Which of following herbal and supplemental medicines used by cosmetic patients WILL INHIBIT AND PROLONG wound healing?
- Glucosamine
- Ginseng
- Garlic
- Vitamin E
Ans: D. Vitamin E
Q 44. Which of the following herbal and supplemental medicines used by cosmetic patients will most likely cause hypoglycemia?
- Glucosamine
- Ginseng
- Garlic
- Vitamin E
Ans: A. Glucosamine
Q 45. Which of the following is the INITIAL EVENT in wound healing?
- Local vasoconstriction
- Local vasodilatation
- Increase microvascular permeability
- Cellular response proliferation
Ans: A. Local vasoconstriction
Q 46. Which of the following factors WILL NOT impede wound healing?
- Diabetes mellitus
- Venous stasis
- Wound moisture
- Hyperthyroidism
Ans: C. Wound moisture
Q 47. Which of the following primary cell types are predominantly found in the DAY 6 of the wound healing process?
- Fibroblasts
- Red blood gell
- Platelets
- Neutrophils
Ans: A. Fibroblasts
Q 48. Which of the following cells synthesize COLLAGEN?
- Macrophages
- Fibroblasts
- Mast cells
- Muscle cells
Ans: B. Fibroblasts
Q 49. Which type of collagen is the MOST common in scar tissue?
- Type I
- Type II
- Type III
- Type IV
Ans: A. Type I
Q 50. Which of the following primary cell type in the post wound healing is the ONE indicated by the rectangle? The vertical axis represents the cell type, the horizontal axis represents the time (days).
- Red blood cells
- Macrophages
- Neutrophils
- Platelets
Ans: B. Macrophages
Q 51. In wound healing the MAXIMAL CONTRACTION occurs at:
- 1 week
- 2 weeks
- 3 weeks
- 1 month
Ans: B. 2 weeks
Q 52. Which of the following components is CRITICAL in the hemostatic phase of wound healing?
- Neutrophils
- Macrophages
- Platelets
- Red blood cells
Ans: C. Platelets
Q 53. Which of the following components is CRITICAL in the synthesis of collagen?
- Vitamin A
- Vitamin C
- Zinc
- Vitamin E
Ans: B. Vitamin C
Q 54. Which of the following vitamins or trace elements in high doses has been associated with delayed wound healing ?
- Vitamin A
- Vitamin C
- Vitamin E
- Zinc
Ans: C. Vitamin E
Q 55. Which of the following percentage of the hair cycle is in the ANAGEN phase?
- 10%
- 50%
- 70%
- 90%
Ans: D. 90%
Q 56. In which of the following medical conditions in the use of synthetic tissue adhesives for wound closure INDICATED?
- Patients with insulin-dependent diabetes
- Patients with collagen vascular disease
- Patients with tendency to form hypertrophic scars or keloids
- Wound depth beyond the depth of the dermis with tendency toward skin-edge inversion
Q 57. Which of the following statements regarding skin staples in FALSE?
- They are made of stainless steel
- They are used in hair-bearing of the scalp
- They do not evert the skin edges
- They are minimally reactive
Ans: C. They do not evert the skin edges
Q 58. Which of the following suture materials has the MOST tensile strength?
- Polypropylene (Prolene)
- Silk
- Polyglactin (Vicryl)
- Polyester (Mersilene)
Ans: D. Polyester (Mersilene)
Q 59. The IDEAL place for using staples for skin closure IS:
- The scalp
- The postauricular area
- The temple area
- The neck
Ans: A. The scalp
Q 60. You are excising a scar by the fusiform ellipse technique. The excision line is 1 cm wide. What is the value of “X” representing the LENGTH of the fusiform incision?
- 1 cm
- 2 cm
- 3 cm
- 4 cm
Ans: C. 3 cm
Q 61. Which of the following statements regarding tissue adhesives is TRUE?
- BioGlue is a tissue adhesive primarily use for vascular anastomosis
- Cyanoacrylate tissue adhesives are designed for superficial and deep tissue use
- Butyl-cyanoacrylate is a long-chained derivatives with a slow breakdown rate of degradation
- Fibrin tissue adhesives are contraindicated in facelift surgery
Ans: A. BioGlue is a tissue adhesive primarily use for vascular anastomosis
Q 62. Which of the following tissue adhesives is composed of purified bovine serum albumin and glutaraldehyde?
- BioGlue
- Tisseel
- Butyl-cyanoacrylate
- 2-Octyl cyanoacrylate
Ans: A. BioGlue
Q 63. Which of the following statements regarding CYANOACRYLATE tissue adhesives is FALSE?
- Cyanoacrylate tissue adhesives are solely recommended for superficial skin closure
- Cyanoacrylate tissue adhesives are contraindicated in children
- Cyanoacrylate tissue adhesives can be used in wound/incision closure for blepharoplasty and facelift
- Cyanoacrylate tissue adhesives breakdown products can produce a histotoxic reaction
Ans: B. Cyanoacrylate tissue adhesives are contraindicated in children
Q 64. Which of the following tissue adhesives is the ONE used for superficial tissue closure?
- Tisseel
- BioGlue
- 2-Octyl cyanoacrylate
- Butyl-cyanoacrylate
Ans: C. 2-Octyl cyanoacrylate