SCALP LAXITY, AN IMPORTANT ASPECT OF DONOR STRIP HARVESTING
What is SCALP LAXITY?
Scalp laxity is a function of scalp movement on the Sub-Galeal space. The Sub-Galeal space (the potential space between the cranium and the connective tissue layer immediately covering the cranium’s surface) – consists of Fibro Areolar tissue.
The ability of the scalp to stretch. This is independent of the sliding phenomenon and is related to the amount of stretching of the skin’s connective tissue layers – more specifically the stretching of elastin and collagen fibres in the dermis.
Scalp laxity has two very distinct components
- First is the ability of the scalp to slide or glide on the underlying pericranium (the outer surface of the scull). This is facilitated by the loose fibro-areolar tissue in the subgaleal compartment, which allows the scalp to be moved on the cranium, often for a distance of several centimeters. This has nothing to do with tissue extensibility or stretching and is due to a simple mechanical movement of the scalp on the pericranium.
In a scalp with a high capacity to slide/glide, an excision width of 5cm or more may be made and closure obtained without any undermining or stretching.
- The second component of scalp laxity is its ELASTICITY or ability to elongate – or “stretch”. It is reiterated that this is independent of the sliding phenomenon. Elasticity is a function of stretching the elastin and collagen fibers (which form part of the connective tissue components of skin). Most of the elastin and collagen fibers are located in the lower layer (reticular layer) of the dermis of the skin. The skin consists of two major layers, the epidermis on the outside and the dermis, which is located below the epidermis. The dermis in itself consists of two layers. The papillary dermis, which links into the basal layer of the epidermis and the reticular layer which sits on top of the sub-cutaneous (under the skin) fat layer. The dermis consists of many nerve endings, blood vessels, sebaceous cysts and sweat glands. The dermis is approximately five times thicker than the epidermis (the outer layer of skin), which consists of five layers in itself, which are from bottom to top: the basal layer, the stratum spinosum, stratum granulosum, stratum lucidum and the stratum corneum which is outer layer of the skin. The stratum corneum consists of dead scales that are packed like shingles and this is exactly what comprises the external aspect of what we generally refer to as hair on the scalp (the hair that we can see on the scalp surface) – the external hair shafts actually consist mainly of scales of stratum corneum singles.
PLASTICIZATION = Stretch Atrophy
When skin elongation (stretching) exceeds 100% of its resting length. In this situation the Elastin fibers are stretched beyond their furthest point of recoil and the skin is then unable to contract back to normal and remains stretched and abnormal.