Osteointegration in Custom-made Porous Hydroxyapatite Cranial Implants: From Reconstructive Surgery to Regenerative Medicine

Exploring complications following cranioplasty after decompressive hemicraniectomy: A retrospective bicenter assessment of autologous, PMMA and CAD implants

Cranioplasty (CP) after decompressive hemicraniectomy (DHC) is a common neurosurgical procedure with a high complication rate. The best material for the repair of large cranial defects is unclear. The aim of this study was to evaluate different implant materials regarding surgery related complications after CP. Type of materials include the autologous bone flap (ABF), polymethylmethacrylate (PMMA), calcium phosphate reinforced with titanium mesh (CaP-Ti), polyetheretherketone (PEEK) and hydroxyapatite (HA). A retrospective, descriptive, observational bicenter study was performed, medical data of all patients who underwent CP after DHC between January 1st, 2016 and December 31st, 2022 were analyzed. Follow-up was until December 31st, 2023. 139 consecutive patients with a median age of 54 years who received either PMMA (56/139; 40.3%), PEEK (35/139; 25.2%), CaP-Ti (21/139; 15.1%), ABF (25/139; 18.0%) or HA (2/139; 1.4%) cranial implant after DHC were included in the study. Median time from DHC to CP was 117 days and median follow-up period was 43 months. Surgical site infection was the most frequent surgery-related complication (13.7%; 19/139). PEEK implants were mostly affected (28.6%; 10/35), followed by ABF (20%; 5/25), CaP-Ti implants (9.5%; 2/21) and PMMA implants (1.7%, 1/56). Explantation was necessary for 9 PEEK implants (25.7%; 9/35), 6 ABFs (24.0%; 6/25), 3 CaP-Ti implants (14.3%; 3/21) and 4 PMMA implants (7.1%; 4/56). Besides infection, a postoperative hematoma was the most common cause. Median surgical time was 106 min, neither longer surgical time nor use of anticoagulation were significantly related to higher infection rates (p = 0.547; p = 0.152 respectively). Ventriculoperitoneal shunt implantation prior to CP was noted in 33.8% (47/139) and not significantly associated with surgical related complications. Perioperative lumbar drainage, due to bulging brain, inserted in 38 patients (27.3%; 38/139) before surgery was protective when it comes to explantation of the implant (p = 0.035). Based on our results, CP is still related to a relatively high number of infections and further complications. Implant material seems to have a high effect on postoperative infections, since surgical time, anticoagulation therapy and hydrocephalus did not show a statistically significant effect on postoperative complications in this study. PEEK implants and ABFs seem to possess higher risk of postoperative infection. More biocompatible implants such as CaP-Ti might be beneficial. Further, prospective studies are necessary to answer this question.

Design of customized implants and 3D printing of symmetric and asymmetric cranial cavities

A methodology has been developed in this work to design customized cranial implants from computed tomography (CT) scan images for symmetric as well as asymmetric defects. The two-dimensional CT scan images were converted into three-dimensional geometric models using software packages. Two cases of cranial cavities at different locations were considered for implant design using two different approaches. Case 1 is having a symmetric cranial cavity while Case 2 has an asymmetric frontal cranial cavity. The craniums with defects were 3D reconstructed. Customized cranial implants were made for the two cases. In Case 1, symmetry was used to design the cranial implant. Symmetry cannot be used in Case 2. In Case 2, the implant was designed by blending from the surface available adjacent to the missing portion of the cranium. 3D reconstructed bone models and customized implants were 3D printed in poly-lactic acid (PLA) using a fused deposition modeling process for form and fit evaluation. Finite element analysis was performed to compare the mechanical behavior of bone, and the two biomaterials - polyether ether ketone (PEEK), and Ti6Al4V. Static structural finite element analysis was performed to simulate the impact of falling off a bicycle with an impact on the cranial implants in the two cases. The load was modeled as a normal force acting on the surface of the implant. It was found that the stresses in the titanium alloy are comparable to those of PEEK for both the cases. However, the strains and deformation were found to be much smaller compared to those in PEEK. Therefore, the titanium alloy is the material of choice for both the cases among the materials under consideration. The designed implants are solid hence may face the challenge in bone ingrowth. In future studies, the implant can be made porous by incorporating a lattice structure to enhance osseointegration and promote bone ingrowth. Implants for both symmetric and asymmetric defect cases in cranium were successfully designed.

Pulsed radiofrequency energy device (PEAK plasmablade™) and CustomBone® Cranioplasty: an appealing surgical rendez-vous

BACKGROUND

CustomBone® prosthesis is a widely recognized effective and successful technique for the reconstruction of cranial bone defects. Prior the cranioplasty implant, meticulous dissection within thick scar tissue is required. During this delicate surgical manoeuvre is vital to avoid damage to the skin flap itself and to the underlying cerebrovascular structures. We report our experience and potential applications of a novel, pulsed monopolar radiofrequency energy device (PEAK PlasmaBlade™, Medtronic plc). It reduced the incidence of post operativesubgaleal hematoma, the operative times and the intra operative blood loss following cranioplasty compared to the traditional scalpel and scissor dissection.

METHODS

The authors present a one centre case series study to review the indications, safety and efficacy of the PEAK PlasmaBlade™ in adult patientsunderwent cranioplasty. Two surgical techniques for tissue dissection were compared: PEAK PlasmaBlade™ versus scalpel and scissor dissection (SSD). Treatment outcomes following each of these surgical approaches, relative to rate of post-operative subgalealhematoma formation, hospital admission, and operative times were compared.

RESULTS

A total of 10 patients that had cranioplasty treatment were evaluated. In patients underwent scalp dissection with the PEAKPlasmaBlade™, we observed a reduction in the operative times, in the subgaleal hematoma formation and then in the hospital stay.

CONCLUSION

PEAK PlasmaBlade™ revealed to be a safe and effective device in tissues dissection for cranioplasty implant. It provided reduction of the rate of subgaleal hematoma formation, operating times and less potential risk to damage cerebrovascular structures.

Long-Term Fate and Efficacy of a Biomimetic (Sr)-Apatite-Coated Carbon Patch Used for Bone Reconstruction

Critical bone defect repair remains a major medical challenge. Developing biocompatible materials with bone-healing ability is a key field of research, and calcium-deficient apatites (CDA) are appealing bioactive candidates. We previously described a method to cover activated carbon cloths (ACC) with CDA or strontium-doped CDA coatings to generate bone patches. Our previous study in rats revealed that apposition of ACC or ACC/CDA patches on cortical bone defects accelerated bone repair in the short term. This study aimed to analyze in the medium term the reconstruction of cortical bone in the presence of ACC/CDA or ACC/10Sr-CDA patches corresponding to 6 at.% of strontium substitution. It also aimed to examine the behavior of these cloths in the medium and long term, in situ and at distance. Our results at day 26 confirm the particular efficacy of strontium-doped patches on bone reconstruction, leading to new thick bone with high bone quality as quantified by Raman microspectroscopy. At 6 months the biocompatibility and complete osteointegration of these carbon cloths and the absence of micrometric carbon debris, either out of the implantation site or within peripheral organs, was confirmed. These results demonstrate that these composite carbon patches are promising biomaterials to accelerate bone reconstruction.

From Reparative Surgery to Regenerative Surgery: State of the Art of Porous Hydroxyapatite in Cranioplasty

Decompressive craniectomy is one of the most common neurosurgical procedures, usually performed after neuropathological disorders, such as traumatic brain injury (TBI), but also vascular accidents (strokes), erosive tumours, infections and other congenital abnormalities. This procedure is usually followed by the reconstruction of the cranial vault, which is also known as cranioplasty (CP). The gold-standard material for the reconstruction process is the autologous bone of the patient. However, this is not always a feasible option for all patients. Several heterologous materials have been created in the last decades to overcome such limitation. One of the most prominent materials that started to be used in CP is porous hydroxyapatite. PHA is a bioceramic material from the calcium phosphate family. It is already widely used in other medical specialties and only recently in neurosurgery. In this narrative review of the literature, we summarize the evidence on the use of PHA for cranial reconstruction, highlighting the clinical properties and limitations. We also explain how this material contributed to changing the concept of cranial reconstruction from reparative to regenerative surgery.

Quality control methods in musculoskeletal tissue engineering: from imaging to biosensors

Tissue engineering is rapidly progressing toward clinical application. In the musculoskeletal field, there has been an increasing necessity for bone and cartilage replacement. Despite the promising translational potential of tissue engineering approaches, careful attention should be given to the quality of developed constructs to increase the real applicability to patients. After a general introduction to musculoskeletal tissue engineering, this narrative review aims to offer an overview of methods, starting from classical techniques, such as gene expression analysis and histology, to less common methods, such as Raman spectroscopy, microcomputed tomography, and biosensors, that can be employed to assess the quality of constructs in terms of viability, morphology, or matrix deposition. A particular emphasis is given to standards and good practices (GXP), which can be applicable in different sectors. Moreover, a classification of the methods into destructive, noninvasive, or conservative based on the possible further development of a preimplant quality monitoring system is proposed. Biosensors in musculoskeletal tissue engineering have not yet been used but have been proposed as a novel technology that can be exploited with numerous advantages, including minimal invasiveness, making them suitable for the development of preimplant quality control systems.

Hydroxyapatite Obtained via the Wet Precipitation Method and PVP/PVA Matrix as Components of Polymer-Ceramic Composites for Biomedical Applications

The aspect of drug delivery is significant in many biomedical subareas including tissue engineering. Many studies are being performed to develop composites with application potential for bone tissue regeneration which at the same provide adequate conditions for osteointegration and deliver the active substance conducive to the healing process. Hydroxyapatite shows a great potential in this field due to its osteoinductive and osteoconductive properties. In the paper, hydroxyapatite synthesis via the wet precipitation method and its further use as a ceramic phase of polymer-ceramic composites based on PVP/PVA have been presented. Firstly, the sedimentation rate of hydroxyapatite in PVP solutions has been determined, which allowed us to select a 15% PVP solution (sedimentation rate was 0.0292 mm/min) as adequate for preparation of homogenous reaction mixture treated subsequently with UV radiation. Both FT-IR spectroscopy and EDS analysis allowed us to confirm the presence of both polymer and ceramic phase in composites. Materials containing hydroxyapatite showed corrugated and well-developed surface. Composites exhibited swelling properties (hydroxyapatite reduced this property by 25%) in simulated physiological fluids, which make them useful in drug delivery (swelling proceeds parallel to the drug release). The short synthesis time, possibility of preparation of composites with desired shapes and sizes and determined physicochemical properties make the composites very promising for biomedical purposes.

In Vitro Osteoinductivity Assay of Hydroxylapatite Scaffolds, Obtained with Biomorphic Transformation Processes, Assessed Using Human Adipose Stem Cell Cultures

In this study, the in vitro biocompatibility and osteoinductive ability of a recently developed biomorphic hydroxylapatite ceramic scaffold (B-HA) derived from transformation of wood structures were analyzed using human adipose stem cells (hASCs). Cell viability and metabolic activity were evaluated in hASCs, parental cells and in recombinant genetically engineered hASC-eGFP cells expressing the green fluorescence protein. B-HA osteoinductivity properties, such as differentially expressed genes (DEG) involved in the skeletal development pathway, osteocalcin (OCN) protein expression and mineral matrix deposition in hASCs, were evaluated. In vitro induction of osteoblastic genes, such as Alkaline phosphatase (ALPL), Bone gamma-carboxyglutamate (gla) protein (BGLAP), SMAD family member 3 (SMAD3), Sp7 transcription factor (SP7) and Transforming growth factor, beta 3 (TGFB3) and Tumor necrosis factor (ligand) superfamily, member 11 (TNFSF11)/Receptor activator of NF-κB (RANK) ligand (RANKL), involved in osteoclast differentiation, was undertaken in cells grown on B-HA. Chondrogenic transcription factor SRY (sex determining region Y)-box 9 (SOX9), tested up-regulated in hASCs grown on the B-HA scaffold. Gene expression enhancement in the skeletal development pathway was detected in hASCs using B-HA compared to sintered hydroxylapatite (S-HA). OCN protein expression and calcium deposition were increased in hASCs grown on B-HA in comparison with the control. This study demonstrates the biocompatibility of the novel biomorphic B-HA scaffold and its potential use in osteogenic differentiation for hASCs. Our data highlight the relevance of B-HA for bone regeneration purposes.

Security and reliability of CUSTOMBONE cranioplasties: A prospective multicentric study

BACKGROUND

Repairing bone defects generated by craniectomy is a major therapeutic challenge in terms of bone consolidation as well as functional and cognitive recovery. Furthermore, these surgical procedures are often grafted with complications such as infections, breaches, displacements and rejections leading to failure and thus explantation of the prosthesis.

OBJECTIVE

To evaluate cumulative explantation and infection rates following the implantation of a tailored cranioplasty CUSTOMBONE prosthesis made of porous hydroxyapatite. One hundred and ten consecutive patients requiring cranial reconstruction for a bone defect were prospectively included in a multicenter study constituted of 21 centres between December 2012 and July 2014. Follow-up lasted 2 years.

RESULTS

Mean age of patients included in the study was 42±15 years old (y.o), composed mainly by men (57.27%). Explantations of the CUSTOMBONE prosthesis were performed in 13/110 (11.8%) patients, significantly due to infections: 9/13 (69.2%) (p<0.0001), with 2 (15.4%) implant fracture, 1 (7.7%) skin defect and 1 (7.7%) following the mobilization of the implant. Cumulative explantation rates were successively 4.6% (SD 2.0), 7.4% (SD 2.5), 9.4% (SD 2.8) and 11.8% (SD 2.9%) at 2, 6, 12 and 24 months. Infections were identified in 16/110 (14.5%): 8/16 (50%) superficial and 8/16 (50%) deep. None of the following elements, whether demographic characteristics, indications, size, location of the implant, redo surgery, co-morbidities or medical history, were statistically identified as risk factors for prosthesis explantation or infection.

CONCLUSION

Our study provides relevant clinical evidence on the performance and safety of CUSTOMBONE prosthesis in cranial procedures. Complications that are difficulty incompressible mainly occur during the first 6 months, but can appear at a later stage (>1 year). Thus assiduous, regular and long-term surveillances are necessary.

Long-term follow-up of custom-made porous hydroxyapatite cranioplasty in adult patients: a multicenter European study. Can we trust self-reported complications?

BACKGROUND

Cranioplasty is a surgical intervention aiming to re-establish the integrity of skull defects. Autologous bone and different heterologous materials are used for this purpose, with various reported related complications. The aim of the study was to evaluate the complication rate in a multicentric cohort of patients underwent porous hydroxyapatite (PHA) cranioplasty implantation and to assess the validity of company post-market clinical analysis.

METHODS

Authors analyzed a company based register of 6279 PHA cranioplasty implanted all over the world. In these adult patients only self-reported complications were available. We then obtained the data of adult patients treated with custom-made porous HA prostheses (CustomBone Service) in 20 institutions from different European countries through an on-site interview with the physicians in charge of the patients (494 patients). The endpoints were the incidence of adverse events and of related implant removal.

RESULTS

The groups of patients had similar demographics characteristics. The average follow-up was 26.7 months. A significantly higher number of complications was recorded in the group of patients underwent onsite interview. Thirty-nine complications were reported (7.89%) with an explantation rate of 4.25% (21 cases) in the series, compared to the data reported from the Company (complications rate of 3.3% and explantation rate of 3.1%). The most common complications were infection (4.86%), hematomas (1.22%), fractures (1.01%), mobilization (0.4%) and scar retraction (0.4%).

CONCLUSIONS

Our data confirm that porous HA cranioplasty is at least as effective as other heterologous materials to repair cranial defects. Another interesting finding is that self-reporting complicantions by surgeons does not give a precise picture of the real rate of complications of the devices. These data in future studies need to be re-confirmed with on-site interviews.

Custom-made Hydroxyapatite Cranioplasty: Radiological and Histological Evidence of Bone-Biomaterial Osteointegration in Five Patients

Custom-made cranial implants facilitate the surgical reconstruction of destructive pathologies of the skull or extensive demolitive skull surgery. Customized cranioplasty allows for an immediate restoration of the functional integrity of the cranial defect (restitutio ad integrum), with excellent functional and esthetic outcome and a quick, safe, and simple procedure. In this context, bioceramics like hydroxyapatite (HA) claim high biocompatibility and bone-binding capability. The osteoconductive properties of the HA have been reported in animal models and humans. The purpose of this study is to demonstrate with radiological and histological examination and how HA prosthesis may integrate after their implantation showing data related to five patients that needed primary HA cranial reconstruction with secondary removal after few years. The histological examination showed neo-formed lamellar/trabecular bone tissue fragments accompanied by the amorphous reticular tissue (HA prosthesis) revealing diffuse ossification sites in all included cases.

Reconstruction of the Shoulder Joint with a Custom-Made Ceramic Implant After a Total Scapulectomy: A Case Report

CASE

We describe a 22-year-old woman who underwent total scapulectomy and shoulder joint reconstruction with use of a custom-made ceramic implant composed of hydroxyapatite and beta-tricalcium phosphate (β-TCP) for a recurrent atypical perineurioma that had arisen from the scapula.

CONCLUSION

To our knowledge, there have been no previous reports of shoulder joint reconstruction with use of a custom-made ceramic implant after a total scapulectomy. The patient showed excellent function of the new shoulder joint and good range of motion without pain or dislocation at 18 months postsurgery. This new method of reconstructing the shoulder joint after a total scapulectomy appears useful and promising.

Hydroxyapatite cranioplasty: a retrospective evaluation of osteointegration in 17 cases

BACKGROUND

Cranial reconstruction with autologous bone is still the gold standard although several biomaterials are available to re-establish the integrity of the cranial vault. Due to their biological and morphological characteristics, hydroxyapatite implants show promising results in small clinical cohort studies, especially within the paediatric population. Its biocompatibility and osteoconductivity should allow the formation of osseous bridging at the skull-prosthesis interface.

OBJECTIVE

To examine the possible occurrence of osteointegration and to quantify it.

METHODS

A retrospective study of patients with a hydroxyapatite implant from 2010 to 2014 at our neurosurgical department was conducted. Demographic, surgical and radiological data were studied. A senior neuroradiologist, a staff member neurosurgeon and a resident neurosurgeon independently performed the radiological evaluation. A new software analysis technique was developed to objectively quantify the degree of osteointegration.

RESULTS

Seventeen implants were evaluated with an average patient age of 39 years and a mean follow-up of 155 weeks. Through radiologic evaluation, osseous bridging was deemed higher than 50% in six prostheses and higher than 75% in three. In five patients, no osteointegration could be seen. The remaining patients exhibited sparse signs of osteointegration, estimated between 10 and 50%. Software analysis showed an average osteointegration ratio of 37.4% with a 400-HU filter and 27.3% with a 700-HU filter.

CONCLUSION

In this small retrospective study of cranial hydroxyapatite implants, osteointegration did occur and to a degree of more than 50% in 1/3 of the patients.

Long-Term Follow-Up Comparative Study of Hydroxyapatite and Autologous Cranioplasties: Complications, Cosmetic Results, Osseointegration

OBJECTIVE

A three-dimensional reconstruction technique using the CustomBone (CB) prosthesis allows custom-made cranioplasty (CP) possessing osseointegration properties owing to its porous hydroxyapatite (HA) composition. This reconstruction technique has replaced less expensive techniques such as subcutaneously preserved autologous bone (SP). Our primary objective was to evaluate complications between CB and SP CP techniques. A secondary objective was to assess cosmetic results and osseointegration of CPs.

METHODS

This single-center study comprised patients undergoing delayed CB or SP CP after craniectomy between 2007 and 2014. A prospective interview was conducted to collect all data, including 2-year follow-up clinical and radiologic data. Cosmetic results were assessed by a qualitative score, and osseointegration was assessed by measuring relative fusion at the CP margins.

RESULTS

Of 100 patients undergoing CB or SP CP between 2007 and 2014, 92 (CB, n = 44; SP, n = 48) participated in the prospective interview. No significant difference in complication rates was observed between the 2 groups. The main complication specific to the CB group was fracture of the prosthesis observed in 20.8% patients. A higher rate of good cosmetic results was observed in the CB group (92.5% vs. 74.3%, P = 0.031). In the CB group, 51% of patients demonstrated no signs of bone fusion of the CP.

CONCLUSIONS

Although the CB prosthesis is associated with cosmetic advantages, the porous hydroxyapatite composition makes it fragile in the short-term and long-term, and effective osseointegration remains uncertain.

Quantitative stereological analysis of the highly porous hydroxyapatite scaffolds using X-ray CM and SEM

BACKGROUND

Material properties of the scaffolds as well as their microstructure are vital in determining in vivo cellular response. Three-dimensional (3D), highly porous scaffolds are used in tissue engineering to provide a suitable microenvironment and to support regeneration of bone. Both pore sizes and their architecture, in particular interconnection density, impact functionality of scaffold during its biomedical applications.

OBJECTIVE

In this paper a comparative study of the microstructure of highly porous hydroxyapatite scaffolds produced via gelcasting of foamed slurries and replication of polyurethane sponge were carried out.

METHODS

Quantitative stereological analysis of the microstructure was conducted using transmission X-ray computed microtomography (μCT) and scanning electron microscopy (SEM). Application of the X-ray microtomography allowed obtaining the 2D cross-sectional images of examined samples, and then the 3D reflection of individual samples.

RESULTS

In our studies we proved that the distribution of pores in HAp bioceramics can be controlled by selection of the manufacturing method. In the case of material produced by the gelcasting method, the porosity of the samples was about ∼78 vol.%, while for the method of replication of the porous organic matrix it was higher ∼84 vol.%. Application of gelcasting method resulted in bioceramics with the macropores ranging from 95 μm to 158 μm (the modal value of 120 μm). Furthermore, micropores of size 34 μm-60 μm - so called "windows", were observed on spherical macropores surfaces. In the case of replication of polyurethane sponge only macropores from 295 μm to 337 μm (the modal value of 300 μm) were obtained. Application of μCT and SEM give more information than classical mercury intrusion porosimetry in studies of porous bioceramics. Developed materials met the criteria for porous bone substitutes.

CONCLUSIONS

The results of quantitative description of microstructure allowed determining the differences between porous hydroxyapatite bioceramics obtained via replication of porous organic matrix and gelcasting of foamed slurry. The stereological analysis demonstrated, that bioceramics prepared via gelling of foamed slurry has a lower pore size and grains (1.1-1.9 μm) than the material obtained by the method of replication of polyurethane sponge (2.1-2.3 μm). Based on morphological analysis the porosity of tested materials was determined. In the case of material produce by the gelcasting, porosity of the samples was about ∼78 vol.%, while for method of replication of the porous organic matrix the porosity was higher and constituted ∼84 vol.%. Furthermore, evaluated materials varied in porosity and the pore size distribution. It was stated that the method of gelcasting resulted in hydroxyapatite bioceramics with the macropores diameter (95-158 μm), micropores so called "windows" (34-60 μm) - observed on spherical macropores walls and micropores of size 0.6 μm-1.3 μm, which were visible in sintered areas. When the method of replication of polyurethane sponge was applied only macropores from 295 μm to 337 μm were obtained. The comparable values of shape factors such as elongation, curvature of pours boundary and convexity, confirmed that macropores in both studied series had similar shape.

Histological assessment of porous custom-made hydroxyapatite implants 6 months and 2.5 years after cranioplasty

Background:

In cranial reconstruction, the features of artificial bone differ. Custom-made porous hydroxyapatite (HAp) implants for cranioplasty have been used all over the world because of their good cosmetic, biocompatibility, and osteoconductive properties. Surgical techniques were analyzed, and histological assessment of new bone formation in the hydroxyapatite was performed.

Methods:

Over a 6-year time period, 41 patients underwent cranioplasty using a custom-made three-dimensional hybrid pore structured hydroxyapatite (3DHPoHAp) implant. The surgical techniques and histological evaluations of 3DHPoHAp in 2 cases, removed 6 months and 2.5 years after cranioplasty, are described.

Results:

Using 3DHPoHAp, cranioplasty was successfully performed for all patients. The implant fit the bone defect exactly, and surgical manoeuvres were simple and easy. All implants were firmly fixed using a titanium plate, and postoperative infection occurred in 1 patient (2.4%). New bone formation was seen in 2 cases 6 months and 2.5 years after cranioplasty. Osteoblasts were progressing to the stoma at various depths, and bone tissue had ripened. Furthermore, lamellar structure was observed in the case at 2.5 years.

Conclusions:

In this study, there was a low infection rate, and new bone formation was seen in vivo after cranioplasty. This study also demonstrated that the 3DHPoHAp implant is a good candidate for cranial bone implants because its good osteoconductivity and biocompatibility.

Hydroxyapatite cement cranioplasty following translabyrinthine approach: Long-term study of 369 cases

OBJECTIVE

To report the authors' experience with hydroxyapatite cement (HAC) cranioplasty and analyze the material's long-term safety and efficacy in repairing translabyrinthine skull-base defects by examining adverse events, specifically cerebrospinal fluid (CSF) leaks and surgical site infections.

STUDY DESIGN

Retrospective case-control study (primary study arm); prospective cross-sectional study of patients not examined within the last 5 years (secondary arm).

SETTING

tertiary-care neurotology private practice and academic practice (two centers).

METHODS

Hydroxyapatite cement implanted following translabyrinthine approach, with or without fat graft, was included. Combined approaches were excluded. Implant-associated adverse events were defined as 1) CSF leaks requiring reoperation or spinal drainage, and (2) infections requiring reoperation. Patients not examined within 5 years were interviewed by telephone to update their condition. Incidence of adverse events was compared to published data for translabyrinthine cranioplasty using fat graft alone. Implant survival analysis was performed.

RESULTS

The study cohort included 369 HAC implants in the same number of patients. There were seven CSF leaks and seven infections. Combined (n = 14) incidence of adverse events was 3.8% (2.09%, 6.28%). Compared to fat graft alone, the adverse events associated with HAC were fewer (P < 0.001). Up to 15 years (5,475 days), HAC cement maintained 95% adverse event-free survival. There were no cases of meningitis.

CONCLUSION

Cranioplasty using HAC with autologous fat following translabyrinthine skull-base surgery is safer and more effective than fat graft alone, up to 15 years after surgery.

LEVEL OF EVIDENCE

4. Laryngoscope, 127:2120-2125, 2017.

Osteointegration in cranial bone reconstruction: a goal to achieve

BACKGROUND

The number of cranioplasty procedures is steadily increasing, mainly due to growing indications for decompressive procedures following trauma, tumor or malformations. Although autologous bone is still considered the gold standard for bone replacement in skull, there is an urgent need for synthetic porous implants able to guide bone regeneration and stable reconstruction of the defect. In this respect, hydroxyapatite scaffolds with highly porous architecture are very promising materials, due to the excellent biocompatibility and intrinsic osteogenic and osteoconductive properties that enable deep bone penetration in the scaffold and excellent osteointegration. Osteointegration is here highlighted as a key aspect for the early recovery of bone-like biomechanical performance, for which custom-made porous hydroxyapatite scaffolds play a major role. There are still very few cases documenting the clinical performance of porous scaffolds following cranioplasty.

METHODS

This paper reports 2 clinical cases where large cranial defects were repaired by the aid of porous hydroxyapatite scaffolds with customized shapes and 3D profiles (Fin-Ceramica, Faenza, Italy).

RESULTS

In the long term (i.e., after 2 years), these scaffolds yielded extensive osteointegration through formation and penetration of new organized bone.

CONCLUSIONS

These results confirm that porous hydroxyapatite scaffolds, uniquely possessing chemico-physical and morphological/mechanical properties very close to those of bone, can be considered as a tool to provide effective bone regeneration in large cranial bone defects. Moreover, they may potentially prevent most of the postsurgical drawbacks related to the use of metal or plastic implants.

Repair of the Orbital Wall Fractures in Rabbit Animal Model Using Nanostructured Hydroxyapatite-Based Implant

Cellular uptake and cytotoxicity of nanostructured hydroxyapatite (nanoHAp) are dependent on its physical parameters. Therefore, an understanding of both surface chemistry and morphology of nanoHAp is needed in order to be able to anticipate its in vivo behavior. The aim of this paper is to characterize an engineered nanoHAp in terms of physico-chemical properties, biocompatibility, and its capability to reconstitute the orbital wall fractures in rabbits. NanoHAp was synthesized using a high pressure hydrothermal method and characterized by physico-chemical, structural, morphological, and optical techniques. X-ray diffraction revealed HAp crystallites of 21 nm, while Scanning Electron Microscopy (SEM) images showed spherical shapes of HAp powder. Mean particle size of HAp measured by DLS technique was 146.3 nm. Biocompatibility was estimated by the effect of HAp powder on the adhesion and proliferation of mesenchymal stem cells (MSC) in culture. The results showed that cell proliferation on powder-coated slides was between 73.4% and 98.3% of control cells (cells grown in normal culture conditions). Computed tomography analysis of the preformed nanoHAp implanted in orbital wall fractures, performed at one and two months postoperative, demonstrated the integration of the implants in the bones. In conclusion, our engineered nanoHAp is stable, biocompatible, and may be safely considered for reconstruction of orbital wall fractures.