Shape modifications of porous hydroxyapatite prostheses to improve rigid implant fixation: Experience in 12 cases

Abstract

Background: Various methods of fixation have been described for custom made hydroxyapatite cranial implants. Their poor malleability limits most of the common used fixation techniques because of the high risk of cranioplasty's fracturing or higher exposure to infections. We present our experience with a new fixation technique, based on an appositely premodified hydroxyapatite implants.

Methods: In a 2-year time period, 12 patients underwent cranioplasty by a modified custom made porous hydroxyapatite implant. Once the three-dimensional computer model of the prostheses was performed, three semicircular extensions placed at strategic positions were drawn and the final prosthesis was realized. At surgery, holes fitting the extensions were drilled into the skull borders and the implant was easily embedded inside the defect. Small titanium meshes overlying the extensions were fixed by screws to the surrounding bone.

Results: A minimal increase of operative times was recorded, with drilling and fixation requiring additional 30 and 15 minutes, respectively. Optimal contact between cranioplasty and skull borders was always observed at control computed tomography (CT) scans. Permanent rigid fixation was obtained in all cases, with good functional and aesthetic results at follow-up.

Conclusions: Modifications of hydroxyapatite implants are obtained without additional costs. The minimal increase of operative times is largely counterbalanced by optimal fixation results. Finally, the bone drilling and the immediate proximity of bone to prosthesis might enhance the potential for osteogenesis and osteointegration.

Keywords: Bone fixation; decompressive craniectomy; hydroxyapatite cranioplasty; osteointegration; prostheses.

Figure 1

Custom bone hydroxyapatite implants fixed by silk sutures (a), large titanium meshes (b), and titanium miniplates (c) positioned in the frontal (F) and temporo-parietal (T, P) region

Figure 2

3D implant model showing the extensions (black asterisks) and intraoperative images demonstrating the areas of drilling (white asterisks) and the final implant position (a), CT scan with 3D reconstruction showing the filling of the cranial defect (b)