The Histomorphologic Evaluation of Hair Follicles Before and After Tissue Expansion in the Human Scalp

ABSTRACT

Soft tissue expansion technique has been a very useful method for the reconstruction of scalp defects and alopecia since the scalp is an unyielding tissue allowing minimal distension in traditional local flap surgery. As a result, there has been wide use of the tissue expansion method in the reconstruction of scalp defect and treatment of alopecia in the plastic surgery. There have been many concerns about histomorphologic changes of the overlying skin and the underlying structure resulting from tissue expansion. We also know that progressive tissue expansion induces increased mitotic activity of the epidermis and thining of the dermis in the overlying skin, as well as significant gross, histologic bony erosion in the underlying structure. However, little informations have been reported about the changes of the hair and pilocebaceus units in scalp expansion. We compared the horizontal sections of the expanded scalp and its longterm histologic changes with a normal unexpanded scalp specimen as a control. The terminal hair proportions to the vellus hair both increased. There was a 32% decrease in follicular units, a 24% decrease in terminal hair, and a 23% decrease in total hairs 8 week after scalp expansion compared to the normal unexpanded scalp. The perifollicular inflammatory changes and fibrosis observed in the full expanded scalp specimen disappeared within 12 weeks after removal of the expander and the flap transposition. In our observation, tissue expansion at the hair-bearing scalp did not precipitate any adverse changes on the hair follicles. On the contrary, we observed that secondary scalp expasion could be safetly performed 3 months after the first scalp expansion.