Tissue expansion
Tissue expansion | |
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MeSH | D015626 |
Tissue expansion is a technique used by plastic, maxillofacial and reconstructive surgeons to cause the body to grow additional skin, bone, or other tissues. Other biological phenomena such as tissue inflammation can also be considered expansion (see tissue inflammation below).[citation needed]
Skin expansion
Skin expansion is a common surgical procedure to grow extra skin through controlled mechanical overstretch. It creates skin that matches the color, texture, and thickness of the surrounding tissue, while minimizing scars and risk of rejection.[1]
When skin is stretched beyond its physiological limit, mechanotransduction pathways are activated. This leads to cell growth as well as to the formation of new cells. In some cases, this may be accomplished by the implantation of inflatable balloons under the skin. By far the most common method, the surgeon inserts the inflatable expander beneath the skin and periodically, over weeks or months, injects a saline solution to slowly stretch the overlaying skin. The growth of tissue is permanent, but will retract to some degree when the expander is removed.[2] Topically applied tissue expansion devices also exist. These have the benefit of being inexpensive and do not require a surgical procedure to implant them under the skin.[3]
Breast reconstruction surgery, for example, can use this technique when the mammary gland is removed by surgery (mastectomy). Later, a more permanent breast implant filled with saline or silicone gel is inserted under the expanded skin pocket.[citation needed]
In other applications, excess skin is grown purposely by expansion on the back or the buttocks, so that it can be harvested later for
Mechanics of skin expansion
Stretching the skin beyond normal expansion invokes several mechanotransduction pathways which increase mitotic activity and promote collagen synthesis. As a result, the skin surface area increases. Continuum mechanics approaches can be used to model skin growth during tissue expansion and non-linear finite element methods can be used to computationally simulate different tissue growth scenarios.[4]
Tissue growth due to skin expansion can be modeled as anisotropic surface area growth as described by the following equations:[citation needed]
where is elastic area stretch that is reversible and is irreversible area growth described by:[citation needed]
where is a vector in the direction of skin thickness. We assume that the skin does not grow in the thickness direction for area growth is equal to volume growth or .[4] We also assume that the newly created skin will have the same density, stiffness, and microstructure as the original, non-expanded skin.[5]
Radial forearm free flaps
Recent studies have demonstrated that using topical tissue expansion can reduce the need for a split thickness skin graft after harvesting a forearm free flap.[6] The authors noted that this results in less pain as well as reduced healing time. This method has also been shown to be cost effective[3] as well as improve cosmetics.[citation needed]
In scalp reconstruction
Tissue expansion has been used on the scalp for treating scalp scarring and baldness, in lieu of hair transplantation when there is insufficient donor hair to transplant on the scar or the scar tissue is not vascularized to support hair growth.
Foreskin restoration
Tissue expansion has also been used for the technique of foreskin restoration, which is usually non-surgical and applies tension externally using specialized devices to replace circumcised tissues with new cells.[10]
Non-surgical tissue expansion techniques can expand one's surviving penile skin, making it a longer tube so it can function like a foreskin.[11]
Men who have been circumcised stretch and apply tension to their shaft and foreskin remnants to expand and elongate tissue in efforts to produce a functional foreskin. This form of tissue expansion can take years, as the amount of skin growth required is typically around 15 in2.[12]
Bone expansion
Muscle expansion
Muscle tissue may also expand and grow, in a process known as stretch-induced myofibrillogenesis.[14][15]
Tissue inflammation
Inflammation, in the biological sense, refers to the cellular response of the body to disturbances, be they internal or external. In the case of asthma or chronic bronchitis the human body responds to allergens or pollutants by flooding the bronchial tree and airway walls with mononuclear cells. The layers of the airway wall, including the inner epithelial tissue lining thickens and expands anywhere from 10% to 300% of healthy individuals, and obstructs air flow.[16] Enduring the disease long term coupled with airway hyperresponsiveness (smooth muscle contraction or Bronchial hyperresponsiveness) leads to chronic continuous inflammation and thickening, and noticeable airway remodeling consisting of stiffer airways and lost elasticity.[17] Inflammation in a constricted cylinder, as with an airway, eventually folds over on itself, leading to mechanically studied buckling patterns and growth relationships within tissue linings.[18][19]
Breast tissue expansion
Tissue expansion is a common technique used for
Alternatives to skin expansion
Research dedicated to alternative skin grafts is currently within the purview of tissue engineering. Multiple engineered tissue-derived and tissue-like substances have made it through the FDA and into the market, though financial success has been moderate.[22] Limitations of this strategy include long incubation times, as well as difficulty in mimicking that exact mechanical and biological properties of functional skin.[23] However, benefits range from decreased donor site morbidity (as a result of no longer needing to harvest from skin expansion) as well as a ready-available source of materials for emergency medicine in the case of traumatic burn or injury. There remains much clinical interest today in developing inexpensive engineered skin grafts that possess the mechanical and biological properties of skin.[citation needed]
See also
References
- PMID 22052000.
- S2CID 36246768.
- ^ S2CID 25611539.
- ^ PMID 22227432.
- PMID 22052000.
- PMID 21453657.
- ^ Van Atta, Burr: "It Was a Bit of a Stretch, But It Reversed His Baldness." The Philadelphia Inquirer, March 1989.
- ^ Kirschner, Joyce: "Hair Today, Gone Tomorrow: Here are the latest techniques to banish baldness." Inside Magazine, Fall 1989.
- ^ Hair Transplant Forum International, Sept/Oct 2006, Scalp Reconstruction: The Role of Tissue Expansion Archived 2012-02-18 at the Wayback Machine, (archive)
- PMID 6484035.
- PMID 22083672.
- ^ "Not a "Snip," But 15 Square Inches". NOHARMM. Retrieved June 4, 2019.
- S2CID 23966501.
- ^ De Dyne, Patrick G (2001). "Application of Passive Stretch and Its Implications for Muscle Fibers". Journal of the American Physical Therapy Association. 81 (2): 819–827.
- PMID 23766692.
- PMID 15032597.
- PMID 10988102.
- S2CID 1209384.
- PMID 21252217.
- PMID 6723196.
- S2CID 28106120.
- ^ Advanced Tissue Sciences Inc.: learning from the past, a case study for regenerative medicine.
- ^ Tissue engineering of replacement skin: the crossroads of biomaterials, wound healing, embryonic development, stem cells and regeneration
External links
- Ilizarov apparatus.
- About Faces: Skin. NICDR National Institutes of Health on-line exhibit. Source of the images used.