Assessment of the effects on growth of porous hydroxyapatite granule cranioplasty in the immature guinea pig craniofacial skeleton

Use of Onlay Hydroxyapatite Cement for Secondary Cranioplasty

BACKGROUND

Children who undergo bi-fronto-orbital advancement (BFOA) frequently develop a contour deformity on the temporal and supra-orbital region, with an incidence reported as high as 55% and 75%, respectively. Up to 20% of patients may require correction. Hydroxyapatite cement (HAC) is a good alternative to autogenous tissue. The available literature on its use focusses on the reconstruction of bone defects, but little has been published on its efficacy and safety as an onlay graft over intact cranium.

OBJECTIVES

To describe our institution's experience with HAC in the pediatric population.

METHODS

Retrospective chart review from 1998 to 2018 on all patients from the Craniofacial Unit at the Sydney Children's Hospital who had either coronal or metopic craniosynostosis and underwent BFOA and later in life required cranioplasty with HAC for contour repair.

FINDINGS

We have performed 166 BFOA and nineteen secondary cranioplasties for contour repair using onlay HAC. The mean age at the time of operation was 14 years. Bi-coronal craniosynostosis was most frequently associated with secondary cranioplasty and 37% had an associated syndrome. The mean volume of HAC used was 37 mL. There was only 1 patient who had a complication (5.3%) and required partial removal of allograft. The mean length of admission was 2 days. Mean follow up time of 22.4 months.

CONCLUSIONS

HAC represents a safe option when used correctly, with low rates of complication and satisfactory cosmetic outcomes.

Complications of hydroxyapatite bone cement in secondary pediatric craniofacial reconstruction

Hydroxyapatite cement has become a popular alternative to bone grafts in reconstructing the calvarium. Although animal studies have shown promising results with use of hydroxyapatite, human clinical studies have shown mixed results including significant rates of infection. This is a retrospective chart review during a 7-year period (1997-2003) of 20 patients who underwent secondary forehead cranioplasty with hydroxyapatite cement (Norian Craniofacial Reconstruction System). Basic demographics including age, sex, and diagnosis were identified. Characteristics of the defects were recorded including size, location, and depth (full versus partial thickness). The volume of hydroxyapatite and any adjunctive procedures were identified. The postoperative course was analyzed for length of follow-up and the presence of infections.Twenty patients were identified in which Norian had been used and 3 patients were lost to follow-up. Secondary forehead asymmetry was the most common presentation. The mean volume of hydroxyapatite used was 24.4 mL. All patients had initially acceptable aesthetic results. Of the 17 patients, 10 (59%) ultimately had infectious complications. Infection occurred on a mean of 17.3 months after surgery (range, 4 mo to 4 y), and the mean amount of hydroxyapatite used was 32.5 mL (infections) versus 14.3 mL (no infections). Of the 10 patients with complications, 9 required surgical debridement and subsequent delayed reconstruction. Although hydroxyapatite cement can yield excellent aesthetic results, its use in secondary reconstruction has yielded unacceptably high infection rates leading to discontinuation of its use in this patient population.

Complications with hydroxyapatite cement in mastoid cavity obliteration

OBJECTIVE

To determine whether hydroxyapatite (HA) bone cement is a suitable material for mastoid cavity obliteration.

STUDY DESIGN & SETTING

Retrospective case review; tertiary care pediatric hospital.

PATIENTS

Three patients, aged 11 to 16 years, underwent canal wall down mastoidectomy for removal of cholesteatomas.

INTERVENTION

Mastoid cavity obliteration was performed with hydroxyapatite bone cement.

MAIN OUTCOME MEASURES

Failure was defined as the necessity for HA explantation.

RESULTS

All three patients required revision surgery to remove the HA cement. Two patients (one primary and one second look with obliteration) presented with granulations in the mastoid cavity, surrounding the cement. The third patient's intraoperative findings included extensive skull base osteitis with erosion of the posterior and middle fossa dural plates, and fistulae of the lateral and superior semicircular canals. All patients recovered fully after removal of the HA cement.

CONCLUSION

This study raises concerns over the use of HA cement for mastoid cavity obliteration. Three of three implanted patients required revision surgery, two with delayed failure of integration and infection, and one with severe osteitis and significant complications.

Custom made cranioplasty prostheses in porous hydroxy-apatite using 3D design techniques: 7 years experience in 25 patients

BACKGROUND

None of the materials currently used to reconstruct skull defects is fully satisfactory. Their biological and physical properties are very different to those of natural bone. Solid state, high porosity hydroxy-apatite (HA) seems to be a good support for bone regeneration within the prostheses, enabling integration of the heterologous material with low post-implant infective risk.

MATERIALS AND METHODS

A model of the cranium of each patient was made in epoxy resin by stereolithography. The prosthesis was built on this model using a ceramic sintering process. In each case, an exact copy of the missing bone flap was obtained (curvature, dimensions, margins, irregularities and thickness). The porosity obtained is the same as that of the spongy bone of the skull with interconnected macropores (>150 microm) to promote osteoblast migration into the prosthetic core. In The Neurosurgery Division of Cesena, 26 cranioplasty prostheses have been implanted with this technique in 7 years (from 1998 to 2004). No particular criteria were pre-established, but the main indications for use of ceramic prostheses were complex and/or extended (surface >25 cm(2)) post-surgery craniolacuna and/or previous unsuccessful procedures due to rejection, infection or bone flap reabsorption.

RESULTS

Twenty-five patients were included in this study. A clinical check-up and 3D CT (mean follow-up 30 months, range 12-79) always showed an excellent aesthetic result. No cases of infection, rejection or spontaneous prosthesis fragmentation were found. The surgical procedure was simpler and shorter than for other described procedures.

CONCLUSIONS

Bioceramic porous hydroxy-apatite prosthesis have been demonstrated as a valid alternative to traditional cranioplasty techniques both aesthetically and in terms of absence of infections/rejections. Principal limitations for the use of HA prostheses are the need for stereolithography process, the poor malleability of the material and the high cost.