Fig. 1

Cranial computed tomography (CT) scan of a 12-year-old male patient who undergone a right decompressive craniectomy because of traumatic brain injury (a). Three months after the initial operation, CT scan (b) and 3D reconstruction of the cranium (c) revealed the existence of residual bone scraps under the scalp (white arrow). Follow-up CT scans after cranioplasty with titanium mesh at 2 months (d & e), 5 months (f) and 9 months (g) indicated gradually enlargement of the bone debris under the implant (white arrow). Eleven months after cranioplasty, a scalp defect (2.0 × 3.0 cm, white arrow head) appeared at the right parietal skin with exposure of the titanium mesh underneath (h). During the implant removal operation, we found the implant under the skin defect was covered by granulation tissue (5.0 × 6.0 cm, multiple white arrow) and an enlarged bone debris (1.0 × 2.0 cm, single white arrow) was found under the mesh (i). After removal of the titanium mesh, the ossification site (white arrow) was found to be right under the defect (white arrow head) (j). All the bone debris were removed during operation (e). Clinical follow-up at 2 months later showed satisfactory wound healing (k)