THE EFFECTS OF SCALP EXPANSION ON THE CRANIAL BONE - A CLINICAL, HISTOLOGICAL, AND INSTRUMENTAL STUDY

The effects of chronic compression of the cranial bone due to progress ive expansion of the scalp have been investigated. Ten patients were s tudied, 6 adults and 4 children, who were treated for congenital (micr otia) or acquired (burns or traumatic) deformities by chronic expansio n over a 2-month period, All underwent computed tomography scans of th e expansion site prior to introduction of the expansion device, immedi ately before removal, and at 9 months after the operation. A case of p ostburn alopecia was lost to the study, because the patient, who had u ltimated scalp expansion, did not return for flap advancement. Instead , she came back 3 months later, without the expander, which had been r emoved at another institution following an automobile accident, In thi s case, because of slower healing, we performed computed tomography sc ans 18 months postoperation. During the second procedure (expander rem oval and flap transposition), bone samples for histological examinatio n were collected directly underneath and along the perimeter of the ex panders, Macroscopically, the bone appeared thinned and had a reduced convexity. This reaction, although temporary, appeared more intense in the children and in the posttraumatic cases. Histological examination showed osteoclastic activation, bony hypotrophy, and reaction (deposi tion of osteoid matrix) under the device, with consequent bone resorpt ion and remodeling, A marked hyperplasia with a hyperostotic reaction was observed around the expanders, At 9 months postoperation, in most cases, a complete normalization was confirmed by computed tomography s cans, Expansion of target (fontanellar and sagittal) areas of the skul l in children, as well as previous trauma to both scalp and skull shou ld be taken into consideration as a risk factor. Further investigation s are suggested.