Pediatric Cranioplasty Using Hydroxyapatite Cement: A Retrospective Review and Preliminary Computational Model

IIntroduction Cranioplasty is a standard technique for skull defect repair. Restoration of cranial defects is imperative for brain protection and allowing for homeostasis of cerebral spinal fluid within the cranial vault. Calcium phosphate hydroxyapatite (HA) is a synthetic-organic material that is commonly used in cranioplasty. We evaluate a patient series undergoing HA cement cranioplasty with underlying bioresorbable mesh for various cranial defects and propose a preliminary computational model for understanding skull osteointegration. Methods A retrospective review was performed at the institution for all pediatric patients who underwent HA cement cranioplasty. 17 patients were identified and success of cranioplasty was determined based on clinical and radiographic follow-up. A preliminary computational model was developed using bone growth and scaffold decay equations from previously published literature. The model was dependent on defect size and shape. Patient data was used to optimize the computational model. Results Seventeen patients were identified with an average age of 6±5.6 years. Average defect size was 11.7±16.8 cm2. Average time to last follow-up CT scan was 10±6 months. Three patients had failure of cranioplasty, all with a defect size above 15 cm2. The computational model developed shows a constant decay rate of the scaffold, regardless of size or shape. The bone growth rate was dependent on the shape and number of edges within the defect. Thus, a star-shaped defect obtained a higher rate of growth than a circular defect because of faster growth rates at the edges. The computational simulations suggest that shape and size of defects may alter success of osteointegration. Conclusion Pediatric cranioplasty is a necessary procedure for cranial defects with a relatively higher rate of failure than adults. Here, we use hydroxyapatite cement to perform the procedure while creating a preliminary computational model to understand osteointegration. Based on the findings, cranioplasty shape may alter rate of integration and lead to higher success rates.

Hydroxyapatite cement cranioplasty in the setting of simultaneous translabyrinthine resection of cerebellopontine angle tumors and cochlear implantation

Cochlear implantation (CI) has become an option for the treatment of hearing loss after translabyrinthine resection of vestibular schwannomas. The surgical video presents the case of a 67-year-old male who had translabyrinthine resection of vestibular schwannoma with simultaneous CI and closure with a hydroxyapatite (HA) cement cranioplasty. HA cement cranioplasty can be utilized in place of abdominal fat graft for the closure of translabyrinthine approaches with similar efficacy and complication profile. To the authors’ knowledge, this is the first reported case of a simultaneous CI and translabyrinthine resection of vestibular schwannoma with HA cement cranioplasty. The video can be found here: https://stream.cadmore.media/r10.3171/2021.7.FOCVID211

Reconstruction of Mastoid Cortex Defects with Hydroxyapatite Cement for Negative Sequelae of Mastoidectomy

Objectives: Mastoid cortex defects resulting from mastoidectomy surgery can rarely lead to negative sequelae, including unsightly post-auricular depression and discomfort. This study sought to evaluate the use of hydroxyapatite cement (HAC) to reconstruct mastoidectomy cortex defects. Methods: Retrospective chart review was undertaken for all patients that underwent reconstruction of the mastoid cortex using HAC at a single tertiary medical center between 2013 and 2019. Collected data included demographics, indications for mastoidectomy, complications, and associated symptom status. Results: Twenty-nine patients that underwent mastoid cortex repair using HAC were included, and ten of these underwent mastoid revision in a secondary procedure to reconstruct the mastoid cortex with a specific goal to eliminate negative signs and symptoms. There were no associated postoperative complications and no instances of post-auricular depression following repair. All cases of secondary reconstruction resolved the primary signs and symptoms that prompted mastoid revision. Conclusions: HAC mastoid cortex reconstruction may be a safe and effective method to resolve negative sequelae resulting from previous mastoidectomy defects. Also, upfront HAC mastoid cortex reconstruction appears viable in select instances as an option to prevent potential future complications.