Epidermal Tissue Underlying an Exposed Skull Fixation Plate: A Case Report.

For bone flap fixation after craniotomy, clamp-type titanium plates are widely used because of their procedural simplicity. However, mechanical irritation caused by the thickness of these plates is known to result in scalp thinning and plate exposure as complications. We report a rare case in which full-thickness skin, including hair, was found beneath an exposed clamp-type titanium plate. The patient was a woman in her 60s who presented with an exposed plate in the frontal region approximately 20 years after a craniotomy. During surgical removal of the plate, epithelial-like tissue with hair was observed directly underneath the outer clamp component. Pathological examination confirmed a full-thickness skin layer composed of epidermis, dermis, subcutaneous fatty tissue, and appendages such as hair follicles and glands. Signs of localized inflammation were also present. Potential mechanisms for this epithelial entrapment include intraoperative inclusion of a free skin fragment or secondary migration of skin appendages caused by chronic irritation. The accumulation of secretions and desquamated debris from such epithelium beneath a solid plate can lead to inflammation and infection. In this case, the exposed plate was removed, the underlying tissue was debrided, and the wound was closed. The patient has been followed for two years postoperatively without any complications. Although this is an unusual case, given the risk of epithelial tissue forming beneath the plate, removal of the plate and debridement of the underlying tissue should be considered when a clamp-type plate becomes exposed.