Evaluation of the Use of Calcium Phosphate Cement for Aesthetic Neurosurgical Cranial Reconstruction

Anatomy of the Frontal Sinus Drainage Pathway Evaluated in 247 Cadavers to Prevent Cerebrospinal Fluid Leakage After Frontobasal Craniotomy

BACKGROUND AND OBJECTIVES

The frontal sinus (FS) drainage pathway (FSDP) may be a conduit for cerebrospinal fluid leakage after frontobasal craniotomy. In this cadaveric study, we aimed to evaluate the anatomy of the FSDP.

METHODS

The FSs and FSDPs of 247 cadavers were investigated. We counted the number of FSs and FSDPs in each half-head, verified the presence of a narrowing section in each FSDP, and evaluated the depth, shape, and size of each narrowing FSDP section.

RESULTS

We investigated 494 sides and 472 FSDPs of 247 cadavers. FSs were unilaterally undeveloped in 13 of 247 cadavers (5.3%) and bilaterally in 8 (3.2%). FSs were unilaterally duplicated in 7 of 247 cadavers (2.8%), and no FSs were bilaterally duplicated or triplicated. No FSs had 2 or more FSDPs, and all 472 investigated FSDPs were invariably narrowed at various depths. The narrowing FSDP sections were elliptical (78.6%), circular (18.1%), triangular (1.8%), or crescent-shaped (1.4%) and of varying thickness and orientation. Although FSDPs were asymmetric in 92.2% of cadavers and narrowing FSDP sections were located deep (8.9 ± 4.4 mm from the anterior skull base), the narrowing FSDP sections were typically small (area: 5.9 ± 3.3 mm 2 ) or thin (short diameter: 2.1 ± 0.7 mm).

CONCLUSION

Each FS had only one FSDP, all FSDPs were invariably narrowed at various depths, and the narrowing FSDP sections were sufficiently small or thin to allow local closure, facilitating prevention of cerebrospinal fluid leakage after frontobasal craniotomy.

Utilization of carbonated calcium phosphate cement for contouring cranioplasty in patients with syndromic craniosynostosis

PURPOSE

Carbonated calcium phosphate (CCP) cement is an alloplastic material which has been increasingly utilized for cranioplasty reconstruction; however, there is a paucity of data investigating its use in patients with syndromic craniosynostosis. The purpose of this study was to characterize our institutional experience with CCP cement for secondary contouring cranioplasty in these patients to establish safety and aesthetic efficacy.

METHODS

Patients with syndromic craniosynostosis undergoing cranioplasty with CCP cement from 2009 to 2022 were retrospectively reviewed for prior medical and surgical history, cranioplasty size, cement usage, and postoperative complications. Aesthetic ratings of the forehead region were quantified using the Whitaker scoring system at three timepoints: preoperative (T1), < 6 months postoperative (T2), and > 1 year postoperative (T3).

RESULTS

Twenty-one patients were included. Age at surgery was 16.2 ± 2.8 years, forehead cranioplasty area was 135 ± 112 cm², and mass of cement was 17.2 ± 7.8 g. Patients were followed for 3.0 ± 3.1 years. Whitaker scores decreased from 1.9 ± 0.4 at T1 to 1.4 ± 0.5 at T2 (p = 0.005). Whitaker scores at T2 and T3 were not significantly different (p = 0.720). Two infectious complications (9.5%) were noted, one at 4.5 months postoperatively and the other at 23 months, both requiring operative removal of CCP cement.

CONCLUSION

Our results suggest that aesthetic forehead ratings improve after CCP contouring cranioplasty and that the improvement is sustained in medium-term follow-up. Complications were uncommon, suggesting that CCP is relatively safe though longer-term follow-up is needed before reaching definitive conclusions.

Eggshell Microparticle Reinforced Scaffolds for Regeneration of Critical Sized Cranial Defects

Scaffold-based approaches for bone regeneration have been studied using a wide range of biomaterials as reinforcing agents to improve the mechanical strength and bioactivity of the 3D constructs. Eggshells are sustainable and inexpensive materials with unique biological and chemical properties to support bone differentiation. The incorporation of eggshell particles within hydrogels yields highly osteoinductive and osteoconductive scaffolds. This study reveals the effects of microparticles of whole eggshells, eggshells without a membrane, and a pristine eggshell membrane on osteogenic differentiation in protein-derived hydrogels. The in vitro studies showed that gels reinforced with eggshells with and without a membrane demonstrated comparable cellular proliferation, osteogenic gene expression, and osteogenic differentiation. Subsequently, in vivo studies were performed to implant eggshell microparticle-reinforced composite hydrogel scaffolds into critical-sized cranial defects in Sprague Dawley (SD) rats for up to 12 weeks to study bone regeneration. The in vivo results showed that the eggshell microparticle-based scaffolds supported an average bone volume of 60 mm³ and a bone density of 2000 HU 12 weeks post implantation. Furthermore, histological analyses of the explanted scaffolds showed that the eggshell microparticle-reinforced scaffolds permitted tissue infiltration and induced bone tissue formation over 12 weeks. The histology staining also indicated that these scaffolds induced significantly higher bone regeneration at 6 and 12 weeks as compared to the blank (no scaffold) and pristine gel scaffolds. The eggshell microparticle-reinforced scaffolds also supported significantly higher bone formation, remodeling, and vascularization over 6 and 12 weeks as confirmed by immunohistochemistry analysis. Collectively, our results indicated that eggshell microparticle-reinforced scaffolds facilitated significant bone regeneration in critical-sized cranial defects.

Middle Cranial Fossa Approach to Repair Tegmen Dehiscence Using Self-setting Calcium Phosphate Cement: A Retrospective Case Review

OBJECTIVES

To review the outcomes of repairing tegmen dehiscence using the middle cranial fossa approach with a self-setting bone cement.

STUDY DESIGN

Retrospective case series.

SETTING

Two academic tertiary hospitals.

PATIENTS

All patients presenting for surgical repair of tegmen dehiscence and with postoperative follow-up for at least 6 months between October 2015 and July 2019.

INTERVENTION

Surgical repair using a middle cranial fossa approach using a layered reconstruction with temporalis fascia and self-setting calcium phosphate bone cement.

MAIN OUTCOME MEASURES

Perioperative complications, recurrence of presenting symptoms/disease, hearing, and facial nerve grade.

RESULTS

The cohort consisted of 22 patients with 23 tegmen dehiscence repairs (1 sequential bilateral repair). There were 16 males and 6 females with an average age at operation of 52.6 years. Repairs were left sided in 9, right sided in 12 patients, and bilateral in 1 patient. No patients had recurrence of presenting symptoms or disease at most recent follow-up. Preoperative hearing was maintained in all patients. Two patients (9% of repairs) experienced delayed partial temporary facial nerve weakness House-Brackman grade 2 and 4 which had recovered by 8 weeks postoperative.

CONCLUSION

We demonstrate a technique for repairing tegmen dehiscence of the middle cranial fossa floor that has excellent postoperative outcomes. We highlight potential technical challenges in this approach as well as the need for counseling for potential partial transient facial nerve dysfunction.

Mineralized Hydrogels Induce Bone Regeneration in Critical Size Cranial Defects

Sequential mineralization enables the integration of minerals within the 3D structure of hydrogels. Hydrolyzed collagen-based hydrogels are sequentially mineralized over 10 cycles. One cycle is defined as an incubation period in calcium chloride dihydrate followed by incubation in sodium phosphate dibasic dihydrate. Separate cycles are completed at 30-minute and 24-hour intervals. For the gels mineralized for 30 min and 24 h, the compressive moduli increases from 4.25 to 87.57 kPa and from 4.25 to 125.47 kPa, respectively, as the cycle number increases from 0 to 10. As indicated by X-ray diffraction (XRD) and Fourier transform infrared analysis (FTIR) analyses, the minerals in the scaffolds are mainly hydroxyapatite. In vitro experiments, which measure mechanical properties, porous structure, mineral content, and gene expression are performed to evaluate the physical properties and osteoinductivity of the scaffolds. Real time-quantitative polymerase chain reaction (RT-qPCR) demonstrates 4-10 fold increase in the expression of BMP-7 and osteocalcin. The in vivo subcutaneous implantation demonstrates that the scaffolds are biocompatible and 90% biodegradable. The critical size cranial defects in vivo exhibit nearly complete bone regeneration. Cycle 10 hydrogels mineralized for 24 h have a volume of 59.86 mm³ and a density of 1946.45 HU. These results demonstrate the suitability of sequentially mineralized hydrogel scaffolds for bone repair and regeneration.

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.