The POSAS deals with the most commonly described scar characteristics from a patient and observers perspective:
Vascularity: The increased vascularisation of the scar (erythema) is a good indicator for scar activity in the early maturation phase. On the long term scars frequently become pale.
Pigmentation disorders are caused by variation in the concentration of melanocytes in the epidermal layer and their melanin production. Significant pigmentation disorders may remain in the long term.
Relief/texture: Irregularities of the scar surface (surface roughness or relief) are particularly seen after split skin autografting by using a meshed split skin graft. The irregularities result from secondary healing of the interstices of the meshed skin graft.
Thickness: Scar tissue normally becomes thicker than the surrounding skin (hypertrophy) during the first months after which the thickness reduces in most cases. Burn scars frequently remain hypertrophic to some extent but scar atrophy is also noted in some scar categories. In daily clinical practice, normally the protruding part of the scar, compared to the surrounding skin, is judged.
Pliability: Scar tissue is normally less supple than normal skin mainly because the scar is thicker and has an inferior quality of collagen architecture. This may cause functional impairment, especially when scars are located on or around joints.
Surface area: The surface area of scars can either reduce or increase as a result of scar contraction or expansion respectively. Scar contraction is mostly considered as a problem in burn scars where it may cause functional problems, whereas scar expansion or widening is often observed in linear scarring
Pain: Pain is defined as an unpleasant sensory and emotional experience which is associated with actual or potential tissue damage. The pathophysiology is still not well understood, but a strong relation with scar hypertrophy and itching has been reported.
Itching / Pruritus: this is an irritating cutaneous sensation that produces a desire to scratch. The impact of itching caused by scar tissue is frequently underestimated especially when large body surface areas are involved i.e. after extensive burn injuries or paediatric burn injury. Itching is often associated with hypertrophic scarring.