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TISSUE EXPANSION
A) HISTORY
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Codivilla (1905) noted that distraction used for bone lengthening resulted in tissue expansion.
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TE was first used beneficially by Neumann in 1957 (PRS 19:124; 1957). He placed a rubber balloon
beneath the temporal skin and serially inflated it to provide local tissue for ear reconstruction. The port
was external and the expander was inflated with air. Neumann’s report was treated as anecdotal.
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In 1975 Radovan did clinical trials (met with scepticism) and re-introduced the TE. His expander is
the type that is in use today: ie internal, self-sealing port with semi-rigid back plate, expanded with saline.
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In 1982, Austad and Rose develop a self expanding osmotic expander
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Austad independently studied the histological changes of TE in the lab.
B) TYPES OF TISSUE EXPANDERS
1. ‘Physiological’ expansion: growth, pregnancy, tumours, festoons, etc.
2. Iatrogenic expansion
a. Remote port
b. Internal port
c. Osmotic/hydrophilic expanders
Some expanders are designed to expand asymmetrically due to variations in wall thickness.
Rapid expansion – mechanically assisted delayed primary closure using various commercial devices (SureClosure, Wisebands)
C) THE PATHOPHYSIOLOGY AND BIOLOGY OF TISSUE EXPANSION
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TE can be divide up into several phases:
1. Insertion
2. Expansion - wound healing phase, expansion phase,
3. Reconstruction
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The expansion phase may occur at different rates, broadly classified into 4 groups:
1. continuous
2. intra-operative,
3. rapid (eg, daily),
4. slow (eg, weekly).
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
TE exerts its effect on tissue aimed at expansion and on adjacent tissue that may not require
expansion.

Expandable tissues are skin (epi and dermis), muscle, fascia,vessels and nerves, hollow muscular
organs? other tissues?
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TE is a combination of:
1. Creep - the progressive increase in the skin length that occurs when skin is stretched by a
constant force
a. Mechanical (70%) - due to collagen fibres adopting parallel orientation, micro
fragmentation of elastin fibres, Displacement of water, Recruitment of tissue from
adjacent areas
b. Biological (30%) – growth of new tissue
2. Stress relaxation - progressive decrease in tension when skin is stretched to a constant length
3. Delay
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Limiting factors to TE include skin elasticity and nutrient blood flow.
CHANGES THAT OCCUR IN DIFFERENT TISSUES DURING EXPANSION
Generally during the expansion phase,skin gets thinner and the collagen content increases.
1. Epidermis
 Mitotic activity in the epidermis is increased during expansion. The epidermis thickens initially, probably
because of postoperative edema, but returns to normal within several weeks.
 With expansion, an increase in melanocytic activity has been noticed. The resulting hyperpigmentation
usually disappears spontaneously after reconstruction.
 Histological changes:
1. reduction in inter-cellular distances,
2. flattening of rete ridges,
3. thickening of stratum spinosum (acanthosis)
2. Dermis
 The dermis over the TE thins. This process starts as soon as the TE is placed and continues during
expansion.
 Overall, expanded skin has a net accumulation of collagen.
Histological changes (in subcutaneously placed expanders):
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1. Thick and compact bundles of collagen are formed and are oriented parallel to the expander
surface
2. Active fibroblasts are noted
3. Myo-fibroblasts are seen in the deep dermis near the capsule
4. On EM, elastin fibres become thicker and longer.
5. Accessory skin structures (glands and hair follicles) may show compression but no degeneration.
6. individual follicles hair may be separated by at least a factor of 2 without producing noticeable hair
thinning.
3. Subcutaneous Tissue
 Subcutaneous tissue thins as a result of TE, seems to be permanent
 Fat atrophy occurs.
 Fibrous septae thicken.
 Vascular structures increase.
4. Muscle
 Muscle atrophies (whether the implant is placed above or below the muscle)
 Muscle mass is diminished and a ‘bathtub’ depression is seen after removal of the TE.
 It is thought that these changes rapidly reverse and the muscle returns to normal.
 Muscle function usually remains unaffected and atrophy recovers
 Histological changes show only those of pressure atrophy:
 Reduced mitochondria
2. Abnormally arranged sarcomeres.
 The vasculature in the muscles remain normal.
5. Bone
 Bony erosion occurs under TE (especially in the very young paediatric patient).
 Bony liping and deposition of bone occur at the periphery of the expander.
 Cranial suture lines become effaced and convoluted.
 Serial CT scans reveal decreased bone thickness and volume but unchanged bone density.
 Osteoclastic resorption occurs beneath TE’s and a periosteal reaction occurs at the periphery.
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 These changes are progressive and significant and can be seen macroscopically and on histology.
 The pathophysiology is a remodelling effect, not just simple pressure deformation.
 The skull is affected more than the long bones.
 After removal of the TE, the bone remodels. Evidence of this remodelling can be seen from day 5. Full
healing occurs by about 2 months (PRS 1990)
 The inner table, the intracranial pressure and the brain are generally not affected by cranial TE’s. Isolated
case reports of full thickness erosion.
6. The Capsule
 A dense fibrous capsule forms around the TE. (Thickness = 300 to 1200 microns)
Capsule thickness is greatest at 2 to 2½ months.
There are 4 histological zones to the capsule around a prosthesis (some have observed only 3 zones, ie no
transitional zone):
1. Inner zone closest to the TE which contains cellular layer with macrophages and fibroblasts, and
relatively acellular collagen fiber bundles
2. Central zone formed by fibrous tissue:
a) fibroblasts and myofibroblasts,
b) thick bundles of collagen fibres becoming increasingly more parallel towards the priphery
3. Transitional zone:
a) loose bundles of collagen,
b) few blood vessels.
4. Outer zone - predominantly a vascular layer containing
a) dilated established and new blood vessels,
b) loosely dispersed collagen fibres,
c) thick and elongated elastic fibres,
d) fibroblasts and occasional mast cells.
 With time the capsule becomes less cellular and more fibrous.
 Only if there is infection or extrusion is there a significant inflammatory cell response.
 The capsule is important in providing the increased vascularity seen in an expanded flap
CHANGES THAT HAVE NOT BEEN NOTED TO OCCUR WITH TE
 Dystrophic calcification.
 Ossification.
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 Dysplastic changes.
 Changes in normal cell maturation.
VASCULARITY OF EXPANDED TISSUE
 Expanded tissue is extremely well vascularised. This has been shown both clinically and histologically.
 New vessels form adjacent to the capsule.
 The mechanism of formation and degree of persistence after expansion is unknown.
 Expanded random pattern flaps can have a greater length and still survive as compared to control
flaps and delayed flaps of the same width (Cherry, Austad and Pasyk, PRS 72:680, 1983):
 Similar experiments with microspheres have demonstrated increased flap length survival as well as
increased blood flow to expanded tissue.
 Microsphere experiments have also demonstrated that the circulation in the capsule exceeds that of the
sub-dermal plexus!
WHERE DOES THE EXTRA TISSUE COME FROM (DIVIDEND OR LOAN)?
 Tissue surface area is increased by TE.
 Clinical observation, photos and tattoo techniques reveal that expansion occurs maximally in the central
area over the TE and least towards the periphery.
 What is the source of the extra tissue gained by TE?
A] Recruitment of tissue from adjacent areas (loan)
B] Increased growth (dividend).
 Brobmann and Huber (PRS 76:731, 1985) showed significant recruitment of tissue from adjacent areas.
This has been confirmed by other authors. Recruitment (or loan) of tissue from adjacent areas should
result in thinning of skin at the periphery of an area of TE. But no thinning at the periphery has been
demonstrated (ie the skin has not stretched and thinned). In fact the periphery usually appears normal and
it is postulated that transient thinning stimulates increased mitotic activity and that thus there is a dividend
or net gain in tissue.
 Austad, Thomas and Pasyk (PRS 78:63, 1986) demonstrated increased mitotic activity in the epidermis
during expansion. There was a threefold increase in epidermal mitotic activity occurring within 24 hours
of expansion followed by a gradual return to normal baseline levels over 2 to 5 days. With prosthesis
deflation, there was a significant decline in the rate of epidermal mitoses below the normal baseline level.
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 Mechanism of action was not postulated. Expansion would therefore appear to result in a net increase in
tissue (a dividend).
 But what percentage of the expanded tissue arises from recruitment and what percentage arises from
the growth of new tissue is unknown.
AFTER RECONSTRUCTION, WHAT CHANGES CAN BE SEEN IN THE PREVIOUSLY EXPANDED TISSUE?
Essentially none!
1. Epidermal, dermal, subcutaneous tissue and muscle thickness return to normal.
2. Blood vessels return to normal size and number.
3. No residual capsule can be seen.
(In specimens taken 2 years after reconstruction).
D) BASIC PRINCIPLES OF TISSUE EXPANSION
I. ADVANTAGES:
1. Local tissue: Better colour, texture, thickness and sensation
2. Minor donor site morbidity (primary closure usually possible)
3. Improved flap vascularity due to delay effect and capsular neovascularisation
4. Generally good aesthetic results
II. DISADVANTAGES:
1. 2 operations
2. Prolonged treatment course
3. Multiple visits and injections
4. Temporary cosmetic and functional impairment
5. Expense
6. Complications
III. INDICATIONS:
1. For shortage of tissue
2. For obtaining skin with special desirable qualities
3. Creation of a flap otherwise not possible
4. Avoiding donor site problems
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Where is tissue expansion useful:
1. for tissue shortage: eg, for breast reconstruction,
2. for obtaining skin with special desirable properties: eg, for correction of alopecia,
3. for creation of a flap otherwise not possible: eg, pre-expanded forehead flap for nasal reconstruction
allows the creation of a broader longer flap than would otherwise be possible,
4. for creation of flaps of skin and functioning muscle: eg, flaps for H+N reconstruction and for facial reanimation,
5. for avoiding problem donor sites: eg, lower leg defects reconstruction.
But, where the lesion can be removed by 3 serial excisions, this is done in preference to TE.
IV. TECHNIQUE
1. Planning
 Plan the procedure in reverse so that the type of local flap that will be used for reconstruction can be
visualised. This allows appropriate selection of expander (size and shape) as well as correct placement
of incision and expander pocket. Select stable tissue for expansion.
 Depending on the area – plan for subcutaneous or subfascial/muscular placement
o scalp – place subgaleal (subcutaneous placement associated with ischeamia)
o face – place above SMAS (below SMAS associated with abnormal facial gesturing).
 incisions should not compromise blood supply or later flap movement.
 Place incisions so that they may be incorporated into the incisions necessary for the ultimate
reconstruction and so that they are concealed along the borders of facial aesthetic units. Radial
incisions are preferred by some to minimize tension on the suture lines, but these may be difficult to
accomplish without creating additional scars and perhaps compromising the blood supply to the
expanded flap. Radial incisions lie perpendicular to the forces of expansion. This allows inflation of
the expander to begin immediately with a lower risk of wound separation. An alternative is to make a
small incision at the margin of the defect, roughly parallel to the defect. This tangential incision is at
increased risk for wound separation once expansion begins, and no expansion should be attempted
initially.
 The expander should be slightly larger than the defect to be repaired. After measuring the defect,
select an expander with a slightly larger base diameter. Some authors recommend expanders with a
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base 2.5 times the diameter of the defect to be closed, although this is not always possible within the
confines of the head and neck region.
2. First Stage (Insertion of the TE)
 Peri-operative cephalosporin is used (Iconomou, Michelow, Zuker - Toronto Hosp for Sick Children:
Annals 31(2):135, 1993). Cloxacillin at RXH.
 Make a large (usually subcutaneous) pocket - larger than the expander selected to allow the base of the
TE to lie flat and to allow closure after placement.
 Some advocate making the pocket prior to choosing the TE. The pocket is made as big as is necessary
and then the largest, comfortably-fitting expander is selected afterwards.
 Some recommend that the long axis of the TE be perpendicular to the skin incision so that the suture
line is not stressed during expansion.
 Obtain good haemostasis.
 Minimal handling of the TE.
 Check the function and integrity of the TE prior to placement.
 Place the filler port in a separate subcutaneous pocket.
 Place a small volume of saline (10-20% of the volume of the TE) in the TE to reduce folds and to
improve haemostasis by the pressure effect.
 Drains are used by us but not in Toronto (ref. above).
 Closure in at least 2 layers: 1 layer to close the pocket with the TE inside; 1 (or more) layers to the
skin and subcut tissue.
3. Expansion
 Begin expansion only after the incision has completely healed, usually after + 3 wks.
 Expansion should be done under sterile conditions injecting saline via a small (usually 23 gauge)
needle. Inject + 10 to 20% of the total TE volume (rough guide).
 Sedation / EMLA cream are useful adjuncts, especially in the child.
 The end points of expansion are determined by:
a) patient comfort / pain
b) skin tension and blanching.
 Continue expansion until enough soft tissue to cover approximately twice the area of the defect has
been achieved. Over-expansion is better than under-expansion.
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 Measurement over the dome(height) of the expander minus the base width of the expander provides a
rough estimate of the additional tissue available for reconstruction
 Usually wait about 3 weeks before the reconstruction is done.
4. Reconstruction
 Reconstruction is done with the local expanded flap (advanced, transposed or rotated) or the expanded
tissue can be used as a free graft. Check that the expanded tissue is large enough before excising any
lesion.
 Evidence exists that the increased vascularity of expanded flaps may be exquisitely sensitive to the
vasoconstrictive effects of adrenaline; therefore, it should not be used
 Drains are recommended at this stage.
DON’S CAVEATS FOR SUCCESSFUL EXPANSION (Burns 21(3):209, 1995)
1. The expander pocket must be 1cm longer and wider than the size of the expander base.
2. The pocket must be closed in 2 layers.
3. Suction drains are always used.
4. Peri-operative antibiotics are routine.
5. The expander is filled on the operating table with 10% of the expander volume.
6. Formal expansion is only started 2 to 3 weeks after TE placement.
7. After the last expansion wait one month before doing the reconstruction.
E) FRONTIERS
 Reduction in the expansion phase: rapid (daily) expansion, intra-operative expansion, continuous
expansion.
 Increasing the range of tissues that can be expanded: vessels, nerves, fascia.
1. RAPID EXPANSION (DAILY)
Described by Marks, Argenta and Thornton (Clinics 1987). The first patients that they rapidly expanded
were those with TE exposure. These patients were expanded on a daily basis (presumably with the expander
still exposed?) so that as much tissue as possible was available for reconstruction. They noticed that
expansion was still successful and therefore they did experiments in pigs to determine pressures, tissue
oxygen tensions, capillary blood flow and flap survival. In the pigs they achieved the same end point in
expansion after 1 week as had previously been done in 5 or 6 weeks. They continued their work in a few
carefully selected human cases.
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In order to achieve a significant degree of expansion, TE’s are aggressively inflated and patients experience a
considerable amount of discomfort, even pain with daily inflations. Inflation is stopped when:
1. pain becomes significant,
2. when the skin feels very tense, or,
3. when blanching occurs.
If blanching occurs, the patient is observed for 30 minutes and if the blanching has not resolved, a small
amount of saline is removed until the blanching goes.
Disadvantages of Rapid Expansion:
1. A thinner capsule is produced with rapid expansion than with normal slow expansion. They comment
that this lack of ‘substance’ that results may present some risks when advancing the expanded flap.
2. Complications are more common with rapid than with conventional slow expansion.
The ability to have all the advantages of an expanded flap (ie local tissue) in an acute setting may outweigh,
in the selected case, the disadvantages of rapid expansion.
2. INTRA-OPERATIVE SUSTAINED LIMITED EXPANSION (ISLE)
Sasaki described a method of intra-operative TE (Clinics 1987). He used cyclic loading (saline filling) of
temporary TE’s placed close to the edges of tissue defects to provide extra skin to allow closure with
minimal tension or distortion.
The mechanism of production of extra skin is stated by Sasaki to be the following:
1. Circumferential migration of skin towards the apex of the expander
2. Thinning of the skin provides length (?the skin stretches)
3. Tissue fluids and mucopolysaccaride are squeezed out.
ISLE seems to rely on creep (and recruitment as part of creep) to obtain its ‘extra’ skin.
Man took Sasaki’s work further by using extremely high intra-expander pressures at the time of surgery.
Mackay, Manders et al in a controlled animal trial (piglets) (PRS 86(4):722, 1990) compared ISLE and
simple undermining of skin and demonstrated no improvement in the amount of tissue gained. They state
that all the benefit from ISLE are as a result of the tissue undermining required for expander placement. The
process of intra-operative tissue expansion merely stretches the skin for a short period and that soon after
surgery the skin attempts to return to its previous state and undue tension is placed on the wound. Their
experiments are well conducted compared with Sasaki’s ‘observations’.
3. CONTINUOUS EXPANSION
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Wee, Logan and Mustoe (PRS 90(5):808, 1992) compared Sasaki’s load-cycling method of expansion with
computer assisted continuous pressure TE in the pig model. The continuous pressure TE was done over 3 or
4 days. Intra-operative (pulsed) TE gave a true gain in skin area of 7,4%, while continuous TE resulted in a
22% gain (measured with the TE at 10 mmHg). When the effects of both recruitment and expansion were
added (measurements done with the TE inflated to a pressure of 40 mmHg), intra-operative TE gave a
dividend of 192% versus 286% for continuous TE. Continuous TE therefore yields greater gains than loadcycled TE.
Continuous TE also showed alterations in stress relaxation and breaking strength as compared to both normal
skin and skin expanded by the load-cycling intra-operative method. These alterations are thought to occur
because:
a) collagen fibres have been reorganised, and,
b) some collagen bonds have been broken to allow true stretch.
This is relevant because they state that it is their belief that: ‘much of the (additional) skin achieved in true
tissue expansion represents stretch and reorganisation of dermal collagen fibres rather than new skin created
by mitoses.’
4. TISSUE EXPANSION OF BLOOD VESSELS
Hong et al (Annals 1987) placed TE’s beneath BV’s and expanded them to yield excellent results. The
vessels lengthened considerably, there were no clinical features suggestive of intimal damage and the postexpansion appearance of the vessels was normal suggesting a net gain in tissue.
They state the advantages of vessel expansion may:
1. allow one to avoid the use of a vein graft,
2. extend the arc of rotation in myocutaneous or free flaps.
5. TISSUE EXPANSION OF MYOCUTANEOUS AND FASCIAL FLAPS
Thornton, Argenta, et al (Annals 1987) and Kostakoglu, et al (PRS 91(1):72, 1993) describe the use of TE to
enlarge myocutaneous and fascial flaps.
 Advantages of expanding these flaps prior to use:
1. Increases the size of the flap and therefore a larger defect may be covered and there is less of a problem
with covering the donor defect.
2. Increases the vascularity which allows a larger random segment distally in the flap.
 The disadvantage, however, with expanding muscle is that it tends to atrophy with expansion.
6. TISSUE EXPANSION OF PERIPHERAL NERVES
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This has also shown to be feasible (Manders et al; Clinics 1987).
7. EXPANSION OF OTHER TISSUES
Manders et al also showed that ureter could be expanded.
Bladder responded poorly to intraluminal
expansion (distension led to contraction and subsequent muscle hypertrophy).
The same group are studying the effects of small bowel expansion with initial encouraging results.
Contraindications
Patient factors
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Unwillingness or medical inability to undergo 2 or more operations
Unwillingness or inability to comply with the numerous outpatient visits required for the expansion
process
Lack of concern regarding the appearance of a skin graft or other alternative procedure
Noncompliance
Mental disability
Inability to tolerate the cosmetic deformity during the expansion process
Unwillingness to curtail participation in contact sports or other social activities that increase the risk
of complications
Wound factors
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Previous removal of a malignancy with a significant risk of recurrence (covering the site with an
expanded flap makes detection of recurrence more difficult than in the presence of a skin graft) or
recurrence
Acute injury (possibility of damaged tissues, contamination of the site, or inability to give adequate
informed consent)
Poorly vascularized tissues from radiation therapy (approach with caution because of increased
risk of complications)
Active infection or open wounds
Ongoing chemotherapy (expand at a more gradual rate)
COMPLICATIONS
Minor
1. Pain on expansion
2. Seroma
3. Widening of scar
4. Dog ears after advancement
Major
1. Infection
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2. Exposure
3. Implant failure
4. Implant exposure
a. With imminent exposure without infection, consider

Remove saline and allow skin to heal
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Proceed to reconstruction, often partial and consider further attempt at expansion once
all wounds are healed.
5. Implant migration
6. Induced ischeamia
7. Pressure effects of expander
a. Neuropraxia
b. Skin ischaemia – more likely with vigorous inflation or irradiated tissue
c. Bony deformity
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At 9 months postoperation, in most cases, a complete normalization was confirmed by
computed tomography scans.
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Full thickness skull erosion reported