Correction of large (>25 cm(2)) cranial defects with "reinforced" hydroxyapatite cement: technique and complications

Hydroxyapatite cement is both biocompatible and osteoconductive, and it lacks significant toxic or immunogenic properties, making it an ideal substrate for the repair of cranial defects. However, with its putty-like composition, the repair of large cranial defects can be difficult because significant settling occurs as the cement hardens. We describe a technique in which we use hydroxyapatite cement, reinforced with tantalum mesh and titanium miniplates, for the repair of large (>25 cm(2)) cranial defects.

After the margins of the cranioplasty are delineated, tantalum mesh is placed under the edges of the defect. Titanium miniplate single-hole bars are used to criss-cross the defect and are then secured to the surrounding bone with screws. The mesh is secured to the bars with 28-gauge stainless steel wire. Hydroxyapatite cement is applied in the defect and contoured appropriately.

We performed nine cranioplasties in eight patients ranging in age from 1.5 to 35 years (mean, 12.2 +/- 10.1 yr). The reasons for cranioplasty included cranial defect from prior trauma (n = 4), fibrous dysplasia (n = 2), infected bone flaps (n = 2), and tumor (n = 1). The cranioplasties ranged in size from 40 to 196 cm(2) (mean, 128.3 +/- 56.9 cm(2)). Follow-up ranged from 2 to 33 months (mean, 11.4 +/- 12.8 mo). Two cranioplasty constructs were removed at 1 and 3 months postoperatively owing to infection.

The use of hydroxyapatite cement with mesh and miniplates provides internal structural support and increased stability of the construct. Although this technique provides an excellent cosmetic result and no evidence to date of bony resorption, the rate of infection is alarmingly high in these large constructs.