Cranial bone flap resorption-pathological features and their implications for clinical treatment

Abstract

Cranioplasty following decompressive craniectomy (DC) has a primary complication when using the autologous bone: aseptic bone resorption (ABR). So far, risk factors such as age, number of fragments, and hydrocephalus have been identified but a thorough understanding of the underlying pathophysiology is still missing. The aim of this osteopathological investigation was to gain a better understanding of the underlying processes. Clinical data of patients who underwent surgical revision due to ABR was collected. Demographics, the time interval between craniectomy and cranioplasty, and endocrine serum parameters affecting bone metabolism were collected. Removed specimens underwent qualitative and quantitative histological examination. Two grafts without ABR were examined as controls. Compared to the controls, the typical layering of the cortical and cancellous bone was largely eliminated in the grafts. Histological investigations revealed the coexistence of osteolytic and osteoblastic activity within the necrosis. Bone appositions were distributed over the entire graft area. Remaining marrow spaces were predominantly fibrotic or necrotic. In areas with marrow cavity fibrosis, hardly any new bone tissue was found in the adjacent bone, while there were increased signs of osteoclastic resorption. Insufficient reintegration of the flap may be due to residual fatty bone marrow contained in the bone flap which seems to act as a barrier for osteogenesis. This may obstruct the reorganization of the bone structure, inducing aseptic bone necrosis. Following a path already taken in orthopedic surgery, thorough lavage of the implant to remove the bone marrow may be a possibility, but will need further investigation.

Keywords: Autologous; Bone flap resorption; Cranioplasty; Failed.

Fig. 1

Bone flap resorption on CT scan

Fig. 2

Thin section preparations. a Complete overview of sample H85-16. b The graft (original bone, ob) contains empty osteocyte cavities (arrow) next to newly formed bone (new bone, nb). c Extensive resorption with fibrotic connective tissue in the marrow cavity. d Parallel layering of the bone structure, × 25 magnification (toluidine blue; b, c × 200, d × 25)

Fig. 3

Intact marrow cavity with hematopoiesis of sample H11-16 (Masson-Goldner, × 50)