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Increase in mitosis with narrowing of intracellular
spaces.
Melanocyte activity increases, which can cause
hyperpigmentation.
Epidermal thickening returns to baseline ~6 months
after expansion process.
Dermis
*Overall decrease in thickness due to reticular
dermis thinning, no change in papillary dermis.
Increased fibroblast and myofibroblasts numbers with
thickened collagen bundles.
Degenerative changes to sweat glands and hair
follicles.
Rupture of elastin producing striae.
Can have decreased appreciation of pain, temperature,
pressure and light touch.
*Dermal thinning returns to baseline ~2 years after
expansion.
Muscle
*Decrease in mass and thickness.
Disorganization of myofibrils and myofilament.
No loss of muscle function but injury has been reported
during expansion process (eg, reduced brow elevation
due to frontalis damage).
Fat
*Decrease in thickness, specifically subcutaneous
fat.
Permanent fat loss (30%-50%) due to atrophic
adipocytes being replaced by fibrosis.
Tissue expander capsule
Forms within days due to foreign body reaction
composed of parallel-oriented fibroblasts intervening
with a dense layer of collagen bundles.
Capsulotomy can be formed to increase tissue
advancement at time of tissue expander removal.
Capsulectomy should be used judiciously to avoid
interrupting vascular supply to random-pattern flaps.
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Bone
Thinning of bone but no change in bone density.
Vascularity
Expanded skin is hypervascular secondary to
angiogenesis.
Greatest density of blood vessels found at interface
between the capsule and the expanded local tissue.
No abnormal cellular architecture has been
demonstrated in expanded tissues.
PROCEDURAL CONSIDERATIONS
PRINCIPLES OF TISSUE EXPANDER
PLACEMENT
Fundamental Design
Surface
Smooth: more likely to move in the pocket
Textured: capsule able to grow into device, minimizing
migration
Shape
Available in many standard shapes; can also be
customized.
Round expanders: most commonly used in breast
reconstruction. Results in ~25% of theoretical tissue
gain.
Rectangular expanders: most commonly used in
trunk and extremities. Results in ~40% of theoretical
tissue gain.
Crescent expanders: useful in scalp reconstruction.
Results in ~30% of theoretical tissue gain.
Anatomic expanders: differentially expand the
overlying soft tissue envelope to more accurately
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recreate the body part (ie, tear-drop–shaped
expanders for breast reconstruction).
Custom expanders: designed for irregularly shaped
defects and may be more expensive.
Filling port
Remote port: connected to tissue expander via silastic
tubing and can be placed subcutaneously (more
common) or externally for direct access.
Integrated port: located within the expander. There is
risk of expander puncture.
Port often ferromagnetic and labeled as MRI-unsafe
due to potential interaction with the magnetic field of
the machine.
TECHNIQUE
Incision Placement
*Incisions are generally placed radially to the expander
pocket, perpendicular to the direction of expansion to
minimize tension on the incision during expansion process;
undue tension placed on the incision during expansion can
cause dehiscence and exposure of the expander. Do not
place expanders across joints.
Consider future reconstructive options when planning
incision placement such that the incisions can easily be
incorporated into planned flaps or the tissue to be resected.
Donor tissue sites should be well vascularized and free of
unstable scar without infection/contamination.Minimally
invasive placement of tissue expanders can be performed
with endoscopy to decrease incision length and has been
shown to decrease complications, operative time and
hospital stay.
Choice of Expander
Use the largest expander possible with a base diameter
~2-3 times that of the diameter of the soft tissue defect to
be reconstructed.
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If the expander contains a base plate or rigid backing,
this side should be placed along the floor of the pocket to
guide the direction of expansion outward.
Multiple expanders are sometimes needed to reconstruct
a single defect, depending on the availability of donor
tissue.
Pocket
The expander pocket can be developed in the
subcutaneous, submuscular, or subgaleal (scalp) planes
depending on the location of the soft tissue defect.
The size of the expander pocket should be individually
tailored to allow the expander to lie completely flat with
minimal wrinkling.
Excessive dissection should be limited to prevent expander
migration postoperatively, and meticulous hemostasis is
important to minimize hematoma formation.
Expansion Process
Insert a 23G butterfly needle or Huber (noncutting) needle
into the filling port perpendicularly; bigger needles should
be avoided because they can cause valve leak due to
increased back pressure.
At the time of expander placement, an initial volume is
infused intraoperatively to gently fill the expander pocket to
prevent seroma formation, and in the case of breast
reconstruction patients, to maintain the shape of the
overlying soft tissue envelope. If there is concern for
overlying skin viability, intraoperative fill can be deferred.
The expansion process usually begins 2-3 weeks
postoperatively and continues on a weekly basis thereafter.
Approximately 50-100 cc can be infused during each
expansion, but regardless of the volume infused, the
expander is filled until the patient expresses discomfort or
the overlying skin blanches.
The expansion process is complete based on surgeon
preference when he/she deems there is enough donor
tissue available to reconstruct the soft tissue defect;
however, this is often a difficult decision and additional
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“over” expansion is often recommended to ensure adequate
soft tissue coverage.Typically wait a minimum of 8 weeks
before removing expander for the patient's reconstructive
procedure to allow for adequate tissue equlibration.
CLINICAL APPLICATIONS
Indications for reconstruction generally include traumatic,
congenital, oncologic, or burn defects. See Table 5-1
TABLE 5-1 Indications for Reconstruction
Flap Pre-expansion
Pre-expansion of axial fasciocutaneous flaps facilitates
coverage of larger soft tissue defects using expanded local
tissue and simultaneously limits donor site morbidity by
allowing primary closure.
Pre-expansion of myocutaneous flaps improves safe flap
transfer due to a robust angiogenic response within the
expanded local tissue resembling an incisional delay
phenomenon.
COMPLICATIONS
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Major
Cellulitis and periprosthetic infection
Requires early and aggressive treatment with
intravenous antibiotics.
If caught early, salvage of the expander may be
possible with intravenous antibiotics alone; however,
removal of the expander is often needed due to
decreased clearance of bacteria from around the
expander.
If the infection becomes periprosthetic, removal of the
expander is absolutely mandated.
Port site infections can sometimes be managed by
externalizing the remote filling port.
Hematoma
Evacuation of the hematoma is necessary to prevent
ischemia of the overlying skin flaps and bacterial
superinfection.
Removal of the expander is often not necessary.
Expander exposure or extrusion
Requires removal of the expander if bacterial
colonization is suspected.
Most commonly due to inadequate pocket creation or
poor overlying skin quality.
Treat infection, if present.
Expander deflation
Usually presents clinically as a “flat tire,” and most
often the result of iatrogenic puncture during insertion
of the filling needle.
Requires removal and replacement with a new
expander.
Skin-flap ischemia
Avoid aggressive dissection during expander
placement to prevent devascularization of the overlying
skin flaps.
Avoid expanding too much during an individual
session. If the overlying skin turns white, remove some
fluid from the expander.
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Partial-thickness necrosis can usually be managed with
local wound care.
Full-thickness necrosis requires debridement of all
devitalized tissue and reclosure to ensure adequate
soft tissue coverage of the expander.
Treat infection, if present.
Minor
Incorrect valve placement or valve tissue expander
flipping
Inadequate expansion
Pain during expansion
Temporary contour deformity at the donor site
Widening of surgical scars
Transient neuropraxia of both motor and sensory
nerves
PEARLS
1. Methylene blue can be used to color the contents of the
expander to help identify the valve correctly when filling and to
detect leakage more easily. However, there is a small
percentage of patients with severe allergies to this dye.
2. Expanded local tissue can be re-expanded 3-6 months later.
3. The epidermis is the only layer of skin that increases in
thickness during tissue expansion.
4. The base diameter of the expander should be approximately
two to three times that of the diameter of the soft tissue defect to
be reconstructed.
5. Approximately 50% of the scalp and abdominal wall can be
reconstructed using tissue expansion.
QUESTIONS YOU WILL BE ASKED
1. Describe the phenomena of creep as it relates to tissue
expansion.
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1.
2.
3.
4.
5.
Creep describes the biological response of cells, which
proliferate in response to continued mechanical stress.
2. Describe the histological changes seen with tissue expansion.
Gap junctions become disrupted, epidermis thickens, and
dermis becomes thinner.
3. Describe the contraindications to tissue expansion.
No absolute contraindications, but irradiated bed, infection,
extremities in children are all relative contraindications.
4. What is the effect of tissue expander on overlying skin?
Blood flow increases, causing tissue expansion to mimic the
delay phenomenon.
Recommended Readings
Austad ED, Pasyk KA, McClatchey KD, Cherry GW. Histomorphologic
evaluation of guinea pig skin and soft tissue after controlled tissue expansion.
Plast Reconstr Surg. 1982;70(6):704‐710.
Dong C, Zhu M, Huang L, et al. Risk factors for tissue expander infection in
scar reconstruction: a retrospective cohort study of 2374 consecutive cases.
Burns Trauma. 2021;8:037.
Egeland BM, Cederna PS. A minimally invasive approach to the placement of
tissue expanders. Semin Plast Surg. 2008;22(1):9-17. doi: 10.1055/s-2007-
1019137. PMID: 20567683; PMCID: PMC2884855.
Huang X, Qu X, Li Q. Risk factors for complications of tissue expansion: a 20year systematic review and meta-analysis. Plast Reconstr Surg.
2011;128(3):787‐797.
Radovan C. Tissue expansion in soft-tissue reconstruction. Plast Reconstr
Surg. 1984;74(4):482‐492.
*
Denotes common in-service examination topics.
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6
Fat Grafting
Amy L. Strong and Jaclyn T. Mauch
OVERVIEW
Background
Early reports of fat grafting by Neuber, Czerny, and
Hollander demonstrated the positive, natural appearing
results achievable with fat grafting for facial and breast
reconstruction.
Despite early successes, subsequent reports were met with
varying levels of failure often associated with asymmetry
caused by fat resorption.
In the early 1990s, Coleman proposed several refinement
techniques focused on fat harvest, processing, and
reinjection that increased the predictability of fat grafting
outcomes.
Fat grafting is safe, abundant, readily available, and
completely biocompatible, making it the preferred soft
tissue filler for facial atrophy, breast asymmetry for
aesthetic and reconstructive purposes, radiation damage,
chronic ulceration, scleroderma, and burn injuries.
In general, “fat grafting” can be further broken down into its
components
Mature adipocytes (85%-90% volume).
Stromal vascular fracture (SVF): (10%-15%)
preadipocytes, fibroblasts, vascular smooth muscle
cells, endothelial cells, resident
monocytes/macrophages, lymphocytes, and adiposederived stem/stromal cells (ASCs).
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Adipose-derived stem/stromal cells (ASCs):
(3%-5%) regenerative cells that secrete cytokines and
chemokines that improve engraftment of cells by
reducing circulating immune cells, inhibiting
melanocyte proliferation and melanin synthesis, and
promoting cell turnover.
Fat grafting is further subdivided into the parcel size of the
fat lobules and cell type with different indications for each
(Table 6-1).
TABLE 6-1 Fat Grafting Parcel Size
Nanofats is a misnomer as it does not contain
adipocytes and is composed solely of SVF cells, ASCs,
growth factors, and extracellular matrix
Indications
Macrofat
Augmentation in any subcutaneous location with tissue
atrophy
Facial rejuvenation, specifically malar region in the
deep plane
Lipodystrophic syndromes and atrophic areas
Breast reconstruction
Breast augmentation
Scar revision
Coup de sabre and scleroderma
Hemifacial microsomia or progressive facial atrophy
Microfat: facial
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