Tissue Expansion Flashcards
A 15-year-old girl is evaluated 2 months after a failed scalp replantation because of an avulsion injury. Skin grafting is planned, followed by staged tissue expansion. Photographs are shown. Between which of the following layers of the scalp is the most appropriate anatomic plane for tissue expander placement?
A) Skin and galea
B) Galea and temporalis muscle
C) Temporalis muscle and pericranium
D) Pericranium and cranium
The correct response is Option B.
Layers of the scalp can be easily remembered using the mnemonic SCALP: S (skin), C (subcutaneous), A (galea aponeurotica), L (loose areolar), and P (pericranium). The skin is quite thick and densely adherent to the subcutaneous layer, which contains the vessels and nerves that travel just above the galea. The galea aponeurotica is continuous with extensions of the superficial muscular aponeurotic system: the frontalis anteriorly, the occipitalis posteriorly, and the temporoparietal fascia (superficial temporal fascia) laterally. The loose areolar plane is quite mobile and dissects very easily. As a result, most avulsions occur within this plane. The pericranium is densely attached to the skull and is contiguous laterally with the deep temporal fascia. The temporalis muscle lies below this layer and attaches directly to the temporal bone.
Tissue expanders should be placed under the galea/superficial muscular aponeurotic system layer to provide maximal tissue coverage and to protect and optimize the blood supply to the expanded skin. Placement in the subcutaneous plane would require a difficult, tedious dissection and would result in a thin, poorly perfused flap. Conversely, placement of the expander under the pericranium is unnecessary and would result in a painful, difficult, and unpredictable expansion. There is no clinical indication to place a tissue expander under the temporalis muscle.
2018
A 3-year-old girl is undergoing tissue expansion of the scalp and forehead for resection of a giant congenital nevus. Which of the following changes is most likely to be observed in the area undergoing expansion?
A) Increased adipose tissue
B) Increased blood flow
C) Increased muscle mass
D) Thickening of dermis
E) Thinning of epidermis
The correct response is Option B.
The most likely change to the area undergoing expansion is increased blood flow. Expansion causes increased angiogenesis and vascularity to the tissues, which improves survival when flaps are rotated or transposed. Tissue expansion also causes 1) thickening of the epidermis and hyperkeratosis (this resolves after removal of the expander); 2) thinning of the dermis (which normalizes after approximately 2 years); 3) thinning and reduced muscle mass (without diminished function); and 4) permanent loss of up to 50% of adipose tissue.
2017
A 17-year-old boy is evaluated for scalp reconstruction because of a burn sustained 10 years ago. On examination, there is patchy alopecia and hypertrophic scarring of the left side of the temporoparietal scalp that occupies approximately 35% of the total scalp. Which of the following is the most appropriate method for reconstruction in this patient?
A) Free latissimus dorsi musculocutaneous flap and skin grafting
B) Hair transplantation
C) Orticochea flap
D) Serial excision and closure
E) Tissue expansion
The correct response is Option E.
No other tissue or donor site in the body will approximate the hair-bearing qualities of scalp tissue. Simply, the best replacement for scalp tissue is scalp tissue. In addition to calvarial coverage and wound closure, the reconstructive surgeon should strive for a cosmetically pleasing outcome. In this patient with nearly 40% scalp loss, tissue expansion will provide the optimal functional and aesthetic outcome. Tissue expansion should be considered when local tissue rearrangements are inadequate because of defect size, trauma, or unacceptable rearrangement or distortion of the hairline. Tissue expansion increases the amount of locally available tissue, preserves sensation, and maintains hair follicles and adnexal structures.
Approximately 50% of the scalp can be reconstructed with expanded tissue with minimal change in hair density. Serial expansions can be performed if needed for ultimate closure. When performing expansion, the largest tolerated expander(s) should be placed in the subgaleal plane. Rectangular and crescent-shaped implants provide more expansion than circular devices. Expansion should continue until the expanded flap is approximately 20% larger than the expected defect to account for tissue recoil. Disadvantages of tissue expansion include prolonged time to complete the expansion process (up to 3 months not uncommon), need for at least two operations, and a high rate of complications (6 to 48%). Common problems include infection, implant exposure or extrusion, hematoma, flap necrosis, skull erosion, alopecia, and wide scars.
Serial excisions are useful for smaller defects. The amount of scar and deformity is much less when using tissue expanders versus serial reductions and complex rotation flaps.
Free tissue transfer is best utilized for reconstruction of total or near-total scalp defects, particularly in the setting of irradiation or oncologic reconstruction. The latissimus dorsi muscle free flap is one of the best choices because of its large area and long pedicle. With time, the muscle flap will atrophy and conform well to the underlying bone. Other good options include the radial forearm, anterolateral thigh, or parascapular flaps.
The Orticochea and Juri flaps are ill suited for a defect this large (>30% of scalp) or in this location. Juri flaps (temporoparietal-occipital) are useful for frontal or frontoparietal defects. The flap is based on the parietal branch of the superficial temporal artery and is best used after surgical delay of the distal aspect. The Orticochea procedure (3-flap technique) was classically described for reconstruction of acquired defects of the occiput. Each flap in the design must include a vascular pedicle and the technique can be used to cover up to 30% of the scalp. The cosmetic outcome using Orticochea flaps is often inferior to what can be obtained using tissue expansion because of unnatural resultant hair orientation. For this reason, tissue expansion should be considered in lieu of Orticochea flaps if possible.
Hair transplantation is not appropriate for a defect of this size and a scarred recipient site.
2017
A 9-year-old girl is evaluated because of an 8-month history of alopecia of the scalp caused by a skin graft over the periosteum. A photograph is shown. Which of the following is the most appropriate method to correct this patient’s alopecia?
A) Coverage with a latissimus dorsi musculocutaneous free flap
B) Follicular hair transplantation
C) Full-thickness skin grafting from hair-bearing scalp
D) Serial excision of the skin graft
E) Tissue expansion
The correct response is Option E.
(Please note that this pictorial appears in color in the online examination)
Tissue expansion effectively expands hair-bearing scalp that can then be rotated, advanced, and/or transposed over the area of alopecia to correct the deformity. A latissimus dorsi musculocutaneous free flap does not contain hair, and thus, would cause a similar area of alopecia. Follicular hair transplantation would not be efficacious for a large area of alopecia, and the split-thickness graft over periosteum would be insufficient tissue to accept the grafts. Serial excision of the skin graft is not possible because of the large defect and absence of normal scalp tissue on either side of the defect. A full-thickness graft from the hair-bearing scalp would cause a similar area of donor site alopecia.
2015
Which of the following thickens when a tissue expander is placed and inflated?
A) Dermis
B) Epidermis
C) Fat
D) Muscle
The correct response is Option B.
Data have shown that there are predictable changes that occur to the layers of the skin and soft tissue in response to tissue expansion. Of all the layers listed, only the epidermis displays an increased thickness as a result of tissue expansion. Specifically, the epidermis becomes thicker through a process of hyperkeratosis. There is also narrowing of intercellular spaces and an increase in mitotic activity. The dermis actually thins up to 50% with fragmentation of the elastin fibers and flattening of dermal papillae. Sweat glands and hair follicles drift farther apart. Muscle decreases in both thickness and mass, although its function remains unchanged. Fat thins with some permanent loss of total fat mass. In cases of aggressive expansion, fat necrosis and fibrosis may also occur.
2014
A healthy 5-year-old boy is scheduled to undergo a staged expansion to remove a large congenital melanocytic nevus. Which of the following anatomical regions of the body has the highest risk for complications during the expansion process?
A) Head
B) Lower extremity
C) Neck
D) Torso
E) Upper extremity
The correct response is Option B.
The anatomic region associated with the most complications is the lower extremity. Huang et al. conducted a 20-year meta-analysis and systematic review to come to this conclusion:
The pooled odds ratio for lower limb complications as compared with other anatomical sites was 2.80 (95% confidence interval, 1.14 to 6.86; p = 0.17).
The pooled odds ratio for head and neck complications versus other anatomical sites was 1.31 (95% confidence interval, 0.95 to 1.80; p = 0.1).
The pooled odds ratio for upper limb complications was 1.24 (95% confidence interval, 0.60 to 2.55).
The pooled odds ratio for trunk complications was 0.78 (95% confidence interval, 0.45 to 1.33).
The results indicated that the lower limb was more likely to develop complications than other anatomical sites, whereas the trunk was the safest site on which to perform tissue expansion. This conclusion has also been reported by prior studies. There are certain anatomical and physiologic differences between the extremities and other areas. The extremities tend to be in frequent motion, resulting in compressive and disruptive forces exerted by the regional musculature. Scarring can limit the availability of local flaps because the flaps themselves require a complex geometry in terms of distance and orientation to effectively encompass a curvilinear biconvex surface. The creation of a pocket from a distance, around a curve, or in a cylindrical extremity can be quite challenging.
2020
A 15-year-old boy presents with a giant congenital nevus of the calf. He has a history of lymphoma treated successfully with chemotherapy. His BMI is 28 kg/m2. Placement of a tissue expander with staged excision and advancement flap reconstruction is planned. This patient’s risk of expander-related complications is highest due to which of the following factors?
A) Age
B) Elevated BMI
C) Expander location
D) History of malignancy
E) Male sex
The correct response is Option C.
This patient’s risk factor for expander-related complications is the device being implanted in an extremity. Several large studies have shown that the scalp and extremities are the locations with the highest rate of complications. The patient’s BMI of 28 kg/m2 is not a significant risk factor (if anything, a recent study shows that low BMI is associated with higher risk). A history of treated malignancy does not mean this patient is immunocompromised or increase their risk. Biological sex is not generally found to be a risk factor, although one recent study found that female sex was associated with higher risk for expander-related complications. Younger age has been found to be a risk factor in some studies; however, this patient is a teenager.
2022
