Hydroxyapatite cement. I. Basic chemistry and histologic properties

Mechanical Properties, Drug Release, Biocompatibility, and Antibacterial Activities of Modified Emulsified Gelatin Microsphere Loaded with Gentamicin Composite Calcium Phosphate Bone Cement In Vitro

Bone defects are commonly addressed with bone graft substitutes; however, surgical procedures, particularly for open and complex fractures, may pose a risk of infection. As such, a course of antibiotics combined with a drug carrier is often administered to mitigate potential exacerbations. This study involved the preparation and modification of emulsified (Em) crosslinking-gelatin (gel) microspheres (m-Em) to reduce their toxicity. The antibiotic gentamicin was impregnated into gel microspheres (m-EmG), which were incorporated into calcium phosphate bone cement (CPC). The study investigated the effects of m-EmG@CPC on antibacterial activity, mechanical properties, biocompatibility, and proliferation and mineralization of mouse progenitor osteoblasts (D1 cells). The average size of the gel microspheres ranged from 22.5 to 16.1 μm, with no significant difference between the groups (p > 0.05). Most of the oil content within the microspheres was transferred through modification, resulting in reduced cytotoxicity. Furthermore, antibiotic-impregnated m-EmG did not compromise the intrinsic properties of the microspheres and exhibited remarkably antibacterial effects. After combining with CPC (m-EmG@CPC), the microspheres did not significantly hinder the CPC reaction and produced the main product, hydroxyapatite (HA). However, the compressive strength of the largest microsphere content of 0.5 wt.% m-EmG in CPC decreased significantly from 59.8 MPa of CPC alone to 38.7 MPa of 0.5m-EmG@CPC (p < 0.05). The 0.5m-EmG@CPC composite was effective against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in drug release and antibacterial tests. Compared with m-EmG alone, the 0.5m-EmG@CPC composite showed no toxicity to mouse fibroblast cells (L929). Additionally, the proliferation and mineralization of mouse osteoblastic osteoprogenitor cells (D1 cells) did not have a negative impact on the 0.5m-EmG@CPC composite over time in culture compared with CPC alone. Results suggest that the newly developed antibacterial 0.5m-EmG@CPC composite bone cement did not negatively affect the performance of osteoprogenitor cells and could be a new option for bone graft replacement in surgeries.

Hydroxyapatite-based carriers for tumor targeting therapy

At present, targeted drug delivery is regarded as the most effective means of tumor treatment, overcoming the lack of conventional chemotherapeutics that are difficult to reach or enter into cancer cells. Hydroxyapatite (HAP) is the main component of biological hard tissue, which can be regarded as a suitable drug carrier due to its biocompatibility, nontoxicity, biodegradation, and absorbability. This review focuses on the cutting edge of HAP as a drug carrier in targeted drug delivery systems. HAP-based carriers can be obtained by doping, modification, and combination, which benefit to improve the loading efficiency of drugs and the response sensitivity of the microenvironment in the synthesis process. The drug adsorbed or in situ loaded on HAP-based carriers can achieve targeted drug delivery and precise treatment through the guidance of the in vivo microenvironment and the stimulation of the in vitro response. In addition, HAP-based drug carriers can improve the cellular uptake rate of drugs to achieve a higher treatment effect. These advantages revealed the promising potential of HAP-based carriers from the perspective of targeted drug delivery for tumor treatment.

Physical Properties and Antimicrobial Release Ability of Gentamicin-Loaded Apatite Cement/α-TCP Composites: An In Vitro Study

Apatite cement (AC), which has excellent osteoconductive ability, and alpha-tricalcium phosphate (α-TCP), which can be used for bone replacement, are useful bone substitute materials. The objective of this study was to clarify the physical properties and antimicrobial release ability of antibiotic-loaded AC/α-TCP composites in vitro. Gentamicin-loaded, rapid setting AC/α-TCP composites were prepared in 2 mixing ratios (10:3 and 10:6). The cement paste of AC/α-TCP composites was prepared in a plastic mold and dried in a thermostatic chamber at 37 °C and 100% relative humidity for 24 h. A diametral tensile strength test, powder X-ray diffraction analysis, and gentamicin release test were performed. The diametral tensile strengths of the AC/α-TCP composites were significantly less than that of AC alone. Powder X-ray diffraction patterns exhibited the characteristic peaks of hydroxyapatite in the AC/α-TCP composites and gentamicin-loaded AC/α-TCP composites. The concentration of the released gentamicin was maintained above the minimum inhibitory concentration of Staphylococcus aureus until Day 30 in both the gentamicin-loaded AC/α-TCP composites (10:3 and 10:6). Our results suggest that a gentamicin-loaded AC/α-TCP composite has potential as a drug delivery system. Further study is essential to investigate the antimicrobial activity and safety of the gentamicin-loaded AC/α-TCP composites in animal models.

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.

Comparison of Cranioplasty Techniques Following Translabyrinthine Surgery: Implications for Postoperative Pain and Opioid Usage

OBJECTIVE

To assess differences in postoperative pain, opioid usage, and surgical outcomes between cranioplasty using abdominal fat graft (AFG) versus hydroxyapatite cement (HAC) following translabyrinthine surgery.

STUDY DESIGN

Retrospective case control.

SETTING

Tertiary referral center.

PATIENTS

Sixty translabyrinthine procedures were evaluated, including 30 consecutive HAC patients and 30 matched AFG patients. Patients were matched by age, gender, body mass index, and tumor size.

INTERVENTION

Cranioplasty using HAC or AFG following translabyrinthine resection of vestibular schwannoma.

MAIN OUTCOME MEASURES

Postoperative patient pain ratings, narcotic usage, inpatient length of stay, and complication rates.

RESULTS

Patients who underwent HAC cranioplasty had lower postoperative pain scores on several measures (p < 0.05) and less postoperative narcotic usage (mean difference of 36.7 morphine equivalents, p = 0.0025) when compared to those that underwent AFG closure. HAC cranioplasty patients had shorter average length of hospital stay (2.2 vs 3.4 days, p = 0.0441). Postoperative cerebrospinal fluid leaks (one in HAC group, two in AFG group) and skin reactions in AFG closure patients (n = 1) were infrequent.

CONCLUSION

HAC cranioplasty is a safe technique comparable to AFG closure following translabyrinthine surgery which can decrease postoperative pain, narcotic usage, and hospital length of stay.

Non-Surgical Touch-Up with Hyaluronic Acid Fillers Following Facial Reconstructive Surgery

The use of hyaluronic acid (HA) injectable fillers has become increasingly widespread in facial recontouring and rejuvenation. We report our experiences to emphasize the role of HA fillers as tools beyond aesthetic treatments in cases of post-surgical facial sequelae. HA fillers are generally used for aesthetic rejuvenation, but one potential new horizon could be their application in trauma, reconstructive, and craniofacial surgery. This study was conducted retrospectively, evaluating medical reports of patients treated at the Maxillofacial Surgery Unit, University of Campania “Luigi Vanvitelli”, Naples, for lip incompetence, trauma, oncological, reconstructive, and craniosynostosis surgery sequelae. Visual analog scale (VAS) evaluation was performed to assess patient satisfaction. No major complications (i.e., impending necrosis or visual loss) were reported. Bruising and swelling was reported for 48 h after lip injection. At the immediate VAS evaluation, 67% of the patients were “extremely satisfied” and 33% “satisfied”. In those 33%, VAS scores changed to “extremely satisfied” at 6–9 weeks and 3–6 months of VAS evaluation (contextually to improvement in tissue flexibility, elasticity, and aesthetic appearance). Results indicate that this minimally invasive approach achieves a high level of aesthetic enhancement, improving patient satisfaction. The concept of HA filler applications could be a frontier that may be applicable to other areas of reconstructive facial plastic surgery.

Accuracy of patient-specific temporal implants using PEKK

The main aim of this study was to evaluate the accuracy of immediate CAD/CAM reconstruction of the temporal hollowing following temporalis muscle surgery, using a patient-specific implant (PSI) PEKK model. This case series included ten patients who underwent maxillofacial reconstruction using temporalis muscle flap (TMF). The study involved the preoperative planning and fabrication of the temporal implant using virtual surgical planning software. The planning was based on multislice CT scans, from which DICOM files were used to fabricate a 3D model of the temporalis muscle using polyetherketoneketone (PEKK). The patients were followed up for 12 months, to check for any signs of infection or mobilization, and to assess accuracy. At the end of the follow-up period, all the patients showed acceptance of the external appearance, with no signs of infection or rejection. These customized implants were measured and compared with their original 3D preoperative planning using a point-based analysis. This revealed a mean difference (±SD) of 0.0373 (±0.3036) mm and a median difference (Q1 to Q3) of 0.0809 (-0.2108 to 0.2769) mm. The study demonstrated that a highly accurate duplication of PSIs can be achieved using this template-molding workflow. The use of PEKK PSIs resulted in uneventful healing and esthetic acceptance by the patients and, therefore, is a relevant treatment option when temporal hollowing has to be corrected.

Tissue Level Changes after Maxillary Sinus Floor Elevation with Three Types of Calcium Phosphate Ceramics: A Radiological Study with a 5-Year Follow-Up

This study evaluates the radiological changes in tissue height after maxillary sinus floor elevation (MSFE) using three types of calcium phosphate ceramics over a period of up to 5 years after dental implant placement. In 163 patients, MSFE was performed. Three groups of patients were distinguished and treated based on the type of calcium phosphate ceramic used and radiologically evaluated: 40 patients with β-tricalcium phosphate (β-TCP), 76 patients with biphasic calcium phosphate (BCP) 20% hydroxyapatite (HA)-80% β-TCP, and 47 patients with BCP 60% HA-40% β-TCP. Radiological measurements were performed on panoramic radiographs at several time points up to 5 years after dental implant placement. After MSFE, a slow decrease in tissue height measured over time was seen in all three study groups. Resorption of the grafted bone substitutes was more prominent in β-TCP than in BCP ceramics with an HA component (60/40 and 20/80). Loss of tissue height after 5 years was lowest in BCP 60/40 and highest in β-TCP. This radiological study shows a predictable and comparable behavior of the slow decrease in tissue height over time for all three types of calcium phosphate ceramics used in MSFE. The fraction of HA in calcium phosphate ceramics and dental implant loading seems to be beneficial for tissue height maintenance after MSFE.

Reducing the risk of cerebrospinal fluid rhinorrhea following translabyrinthine surgery of the posterior fossa

Objective

To describe the procedure and results of an adapted closure and reconstruction technique for translabyrinthine surgery that focuses on identifying and managing potential pathways for CSF egress to the middle ear and Eustachian tube.

Methods

Retrospective review of a cohort of translabyrinthine acoustic neuroma cases that were reconstructed using this technique.

Results

In addition to meticulous packing of potential conduits using soft tissue, hydroxyapatite cement is used to seal opened air cell tracts prior to obliteration of the mastoid defect using adipose tissue. Early results of a small patient cohort using this technique are encouraging and there were no wound infections. There was a single case of CSF rhinorrhea associated with incomplete sealing of opened petrous apex cells, with no recurrence after appropriate implementation of the described protocol during revision surgery.

Conclusion

Proactive management of potential conduits of CSF egress including opened air cell tracts has a high likelihood of reducing rates of rhinorrhea and need for revision surgery after the translabyrinthine approach to the posterior fossa.

Impact of Dopants on the Electrical and Optical Properties of Hydroxyapatite

This chapter deals with the effect of alternating electrical current on hydroxyapatite [HAp, Ca10(PO4)6(OH)2] and doped HAp along with their optical response and the processes involved. The dielectric constant, permittivity and ac conductivity were analyzed to have an insight into the surface charge polarization phenomenon. Further, the magnitude and the polarity of the surface charges, microstructure, and phases also play significant role in the cell proliferation and growth on the implants. Besides, the mechanism behind the electrical properties and the healing of bone fracture are discussed. The influence of various dopants on the optical properties of HAp viz., absorbance, transmission, band gaps and defects energy levels are analyzed along with the photoluminescence and excitation independent emission. In the future outlook, the analysis of effect of doping is summarized and its impact on the next generation biomaterials are elucidated.

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.

Outcomes of a novel alloplastic technique for external auditory canal repair in tympanomastoidectomy

OBJECTIVE

To analyze surgical outcomes of a novel alloplastic reconstruction technique for partial external auditory canal (EAC) defects in tympanomastoidectomy.

METHODS

Retrospective study of 51 patients with cholesteatoma who underwent repair of partial EAC defects during tympanomastoidectomy at a tertiary referral center over 8 years. Nineteen patients were treated with a novel alloplastic graft technique using hydroxyapatite cement and bone pâté for EAC repair. Thirty-two patients treated with traditional cartilage repair of the EAC served as a control group. The primary outcomes measured were postoperative cholesteatoma recurrence rates, infection rates, and mean air-bone gap (ABG).

RESULTS

Twenty of the 51 cases (39.2%) were revision surgeries for cholesteatoma recidivism, with a greater proportion of revision surgeries in the alloplastic group (57.9% vs 28.1%, P = .04). There was no significant difference in postoperative cholesteatoma recurrence (P = 1.00) or infection rates (P = .64) between the two techniques, with the alloplastic group experiencing slightly lower rates of recurrence (36.8%) and infection (5.3%) than cartilage repair (37.5% recurrence, 12.5% infection). Mean postoperative ABGs were comparable between the alloplastic (21.5 dB) and cartilage group (26.0 dB, P = .10).

CONCLUSIONS

Composite alloplastic and bone pâté reconstruction is an effective technique to repair partial EAC defects in tympanomastoidectomy, with comparable postoperative hearing outcomes and no increased risk of cholesteatoma recurrence or infection compared to traditional cartilage repair. Recidivism rates were relatively high in both groups, likely due to the high rate of revision surgeries and aggressive nature of cholesteatoma within the cohort.

LEVEL OF EVIDENCE

Level 3B.

A study on biosafety of HAP ceramic prepared by SLA-3D printing technology directly

Hydroxyapatite powder was mixed into photosensitive resin to form complex shape scaffold using SLA-3D printing technology, and then the final entity was obtained successively by debinding and sintering. It is crucial to confirm whether the prepared hydroxyapatite scaffold have the toxic effects after our designed printing, debinding, and sintering processes because the photosensitive resin in the starting printing paste is poisonous to cells. To investigate these issues in details, thermogravimetric analysis (TG), differential scanning calorimetry (DSC), in vitro cytotoxicity test, and implantation pre-experiment in the rabbit parietal were performed, aiming to develop the SLA-3D prepared hydroxyapatite scaffold. Through thermal analysis, it was proved that photosensitive resin would be completely pyrolyzed at temperature ranging from 350 °C to 580 °C, corresponding to a secondary chemical reaction mechanism. Combined with cytotoxicity test results, it is unquestionable that the toxic substances would be totally decomposed after debinding process and a good biocompatible HAP samples could be obtained. The finally prepared HAP samples with micro-holes showed good biosafety in pre-experiment of the rabbit parietal implantation.

Potencial of different hydroxyapatites as biomaterials in the bone remodeling

PURPOSE

To analyze the therapeutic potentials of different hydroxyapatites used for the correction of bone defects in rats.

METHODS

Forty rats, male, albino wistar, were distributed in 4 groups. They were submitted to a 3.5 mm defect in tibia. They received low purity hydroxyapatite, Strontium hydroxyapatite and hydroxyapatite doped with gallium, having a seven day evaluation time. Histopathology slides were stained with hematoxylin-eosin, for morphological evaluation. Were analyzed inflammatory processes, necrosis, presence of osteoclasts and osteoblasts, presence of the material, presence of white cells, neovascularization and bone neoformation.

RESULTS

It was observed that the groups HAPSr and HAPGa, presented better results of trabecular bone, hyaline cartilage and bone marrow more organized.

CONCLUSION

There was improvement in the repair of the bone defect produced, showing that these hydroxyapatites are effective osteoinductive, osteoconductive, osteintegrant agents and have biocompatibility, and may be indicated for use in defect repairs.

Gold nanoparticles in injectable calcium phosphate cement enhance osteogenic differentiation of human dental pulp stem cells

In this study, a novel calcium phosphate cement containing gold nanoparticles (GNP-CPC) was developed. Its osteogenic induction ability on human dental pulp stem cells (hDPSCs) was investigated for the first time. The incorporation of GNPs improved hDPSCs behavior on CPC, including better cell adhesion (about 2-fold increase in cell spreading) and proliferation, and enhanced osteogenic differentiation (about 2-3-fold increase at 14 days). GNPs endow CPC with micro-nano-structure, thus improving surface properties for cell adhesion and subsequent behaviors. In addition, GNPs released from GNP-CPC were internalized by hDPSCs, as verified by transmission electron microscopy (TEM), thus enhancing cell functions. The culture media containing GNPs enhanced the cellular activities of hDPSCs. This result was consistent with and supported the osteogenic induction results of GNP-CPC. In conclusion, GNP-CPC significantly enhanced the osteogenic functions of hDPSCs. GNPs are promising to modify CPC with nanotopography and work as bioactive additives thus enhance bone regeneration.

The modified temporalis muscle flap in reconstruction of palate and temporal deformity

PURPOSE

The purpose of this article was to introduce a modified temporalis muscle flap (TMF) which was used to reconstruct palate and temporal deformity.

PATIENT AND METHODS

This was a retrospective review of the use of the modified TMF in reconstruction of palate and temporal deformity. We evaluated the result which included operative time, bleeding, necrosis, infection, facial nerve deficit, and cosmetic deformity.

RESULTS

All the 16 patients accepted the modified TMF surgery successfully. There were no complications. All of them were satisfied with the postoperative appearance.

CONCLUSIONS

The modified TMF was a reliable and safe flap that can be used to reconstruct the surgical defect of plate and fill the temporal fossa.

The use of a biphasic calcium phosphate in a maxillary sinus floor elevation procedure: a clinical, radiological, histological, and histomorphometric evaluation with 9- and 12-month healing times

Background

This study evaluates the clinical, radiological, histological, and histomorphometric aspects of a fully synthetic biphasic calcium phosphate (BCP) (60% hydroxyapatite and 40% ß-tricalcium phosphate), used in a human maxillary sinus floor elevation (MSFE) procedure with 9- and 12-month healing time.

Methods

A unilateral MSFE procedure, using 100% BCP, was performed in two series of five patients with healing times of 9 and 12 months respectively. Clinical and radiological parameters were measured up to 5 years postoperatively. Biopsy retrieval was carried out during dental implants placement. Histology and histomorphometry were performed on 5-μm sections of undecalcified bone biopsies.

Results

The MSFE procedure with BCP showed uneventful healing in all cases. All dental implants appeared to be well osseointegrated after 3 months. Radiological evaluation showed less than 1 mm tissue height loss from MSFE to the 5-year follow-up examination. No signs of inflammation were detected on histological examination. Newly formed mineralized tissue was found cranially from the native bone. The BCP particles were surrounded by connective tissue, osteoid islands, and newly formed bone. Mineralized bone tissue was in intimate contact with the BCP particles. After 12 months, remnants of BCP were still present. The newly formed bone had a trabecular structure. Bone maturation was demonstrated by the presence of lamellar bone. Histomorphometric analysis showed at 9 and 12 months respectively an average vital bone volume/total volume of 35.2 and 28.2%, bone surface/total volume of 4.2 mm²/mm³ and 8.3 mm²/mm³, trabecular thickness of 224.7 and 66.7 μm, osteoid volume/bone volume of 8.8 and 3.4%, osteoid surface/bone surface (OS/BS) of 42.4 and 8.2%, and osteoid thickness of 93.9 and 13.6 μm.

Conclusions

MFSE with BCP resulted in new bone formation within the augmented sinus floor and allowed the osseointegration of dental implants in both groups. From a histological and histomorphometric perspective, a 9-month healing time for this type of BCP may be the optimal time for placement of dental implants.

The Production of Porous Hydroxyapatite Scaffolds with Graded Porosity by Sequential Freeze-Casting

Porous hydroxyapatite (HA) scaffolds with porosity-graded structures were fabricated by sequential freeze-casting. The pore structures, compressive strengths, and biocompatibilities of the fabricated porous HA scaffolds were evaluated. The porosities of the inner and outer layers of the graded HA scaffolds were controlled by adjusting the initial HA contents of the casting slurries. The interface between the dense and porous parts was compact and tightly adherent. The porosity and compressive strengths of the scaffold were controlled by the relative thicknesses of the dense/porous parts. In addition, the porous HA scaffolds showed good biocompatibility in terms of preosteoblast cell attachment and proliferation. The results suggest that porous HA scaffolds with load-bearing parts have potential as bone grafts in hard-tissue engineering.

In Vivo Evaluation of S-Chitosan Enhanced Calcium Phosphate Cements

Calcium phosphate cements (CPC), made from dicalcium phosphate dihydrate and calcium hydroxide and reinforced with water soluble S-chitosan, were investigated in vivo. Cylinders of these cements were prepared and prehardened before implantation into preformed radial defects in rabbits. Histological observations after 1, 4, 14 and 22 weeks, respectively, were performed on thin decalcified sections. No inflammation or other negative response was found in the S-chitosan containing cements (S-CPCs). After 4 weeks, newly formed trabeculae contacted with the implant directly in the lower S-chitosan sample, while a thin layer of fibers had formed between the newly formed bone and the implant in the higher S-chitosan samples. The degradation rates of the S-CPCs were significantly lower than the original CPC cement alone. Most of the S-chitosan cements were still present at the end of the 22 weeks. The implant material and the surrounding infiltrated fluid layer were examined by back scattered scanning electron microscopy and X-ray energy-dispersive spectrometry.

Vocal fold augmentation with calcium hydroxylapatite (CaHA)

Objectives

Evaluate the effectiveness of CaHA injection for patients with glottal incompetence.

Methods

Multi-center, open-label, prospective clinical study with each patient serving as his/her own control. Voice-related outcome measures were collected for pre-injection and 1, 3, and 6 months.

Results

Sixty-eight patients were available for evaluation. Fifty percent of the injection procedures were done in office. Fifty-seven percent were diagnosed with unilateral paralysis and 42% with glottal incompetence with mobile vocal folds. Patient satisfaction 6 months post showed 56% had significantly improved voice and 38% reported moderately improved voice. Paired t tests from baseline to 6 months showed significant improvements on the VHI and VAS (vocal effort), CAPE-V judgments of voice severity and videoendostroboscopy ratings of glottal closure, and objective voice measures of glottal closure (MPT and S:Z ratio).

Conclusions

Preliminary results in this large cohort of patients demonstrate excellent clinical results.

Effect of microstructure characteristics on tetracalcium phosphate-nanomonetite cement in vitro cytotoxicity

MC3T3E1 murine pre-osteoblastic cells were used to evaluate the cytotoxicity of tetracalcium phosphate (TTCP)-nanomonetite (DCPA) cement. The starting cement powder mixture was prepared by the in situ reaction between TTCP and a diluted solution of orthophosphoric acid in a planetary ball mill. The cements in the form of pressed cement powder mixture discs differ from each other by the method of pre-treatment and degree of the transformation of cement components in phosphate-buffered saline (PBS). For the evaluation of TTCP-DCPA cement to be non-cytotoxic, it was sufficient to apply the short-time soaking in PBS solution, regardless of whether the cement components were completely transformed or not. If the texture motif and hydroxyapatite particle morphology were properly developed during the initial stage of hardening, the cement cytotoxicity or osteoblast proliferation were insignificantly influenced by the soaking time or the texture stability during cell cultivation, but the lattice ordering enhanced cell proliferation. Results showed that the surface texture and the hydroxyapatite particle morphology are crucial for in vitro cement cytotoxicity evaluation.

Bioceramics in ophthalmology

The benefits of ceramics in biomedical applications have been universally appreciated as they exhibit an extraordinarily broad set of physico-chemical, mechanical and biological properties which can be properly tailored by acting on their composition, porosity and surface texture to increase their versatility and suitability for targeted healthcare applications. Bioceramics have traditionally been used for the repair of hard tissues, such as bone and teeth, mainly due to their suitable strength for load-bearing applications, wear resistance (especially alumina, zirconia and composites thereof) and, in some cases, bone-bonding ability (calcium orthophosphates and bioactive glasses). Bioceramics have been also applied in other medical areas, like ophthalmic surgery; although their use in such a context has been scientifically documented since the late 1700s, the potential and importance of ceramic ocular implants still seem to be underestimated and an exhaustive, critical assessment is currently lacking in the relevant literature. The present review aims to fill this gap by giving a comprehensive picture of the ceramic-based materials and implants that are currently used in ophthalmology and pointing out the strengths and weaknesses of the existing devices. A prospect for future research is also provided, highlighting the potential of new, smart bioceramics able to carry specific added values which could have a significant impact on the treatment of ocular diseases.

Different angiogenic abilities of self-setting calcium phosphate cement scaffolds consisting of different proportions of fibrin glue

To investigate the different angiogenic abilities of the self-setting calcium phosphate cement (CPC) consisting of different proportions of fibrin glue (FG), the CPC powder and the FG solution were mixed at the powder/liquid (P/L) ratios of 1 : 0.5, 1 : 1, and 1 : 2 (g/mL), respectively, and pure CPC was used as a control. After being implanted into the lumbar dorsal fascia of the rabbit, the angiogenic process was evaluated by histological examination and CD31 immunohistochemistry to detect the new blood vessels. The result of the new blood vessel showed that the P/L ratio of 1 : 1 group indicated the largest quantity of new blood vessel at 4 weeks, 8 weeks, and 12 weeks after implantation, respectively. The histological evaluation also showed the best vascular morphology in the 1 : 1 group at 4 weeks, 8 weeks, and 12 weeks after the operation, respectively. Our study indicated that the CPC-FG composite scaffold at the P/L ratio of 1 : 1  (g/mL) stimulated angiopoiesis better than any other P/L ratios and has significant potential as the bioactive material for the treatment of bone defects.

Removal of hydroxyapatite cement from cadaveric temporal bones after transtemporal surgery

HYPOTHESIS

To determine the best method of removing hydroxyapatite cement from the temporal bone in the postoperative period.

BACKGROUND

The advent of hydroxyapatite cement in neurotologic surgery of the temporal bone has dramatically decreased the rate of postoperative cerebrospinal fluid leaks. However, there is no literature currently available on how to manage these patients in the setting of postoperative hematomas of the cerebellopontine angle.

METHODS

Nine cadaveric temporal bones were obtained that had previously undergone translabyrinthine approach drilling in an academic temporal bone lab. Fascia and adipose tissue were placed medial to the facial nerve and the temporal bone was then filled with hydroxyapatite cement to the level of the cortex. Removal of hydroxyapatite cement was undertaken using a Freer elevator, mastoid bone curette, and finally, a drill in sequential fashion. This occurred at 9 predetermined time intervals from 1 to 30 hours and was timed in each case.

RESULTS

Removal using the freer and curette failed in each case, and the drill was ultimately used to remove the hydroxyapatite cement in all cases. The time to reach the packed fascia and adipose tissue varied from 3 to 6 minutes, average time is 4.27 ± 0.84 minutes.

CONCLUSION

Although hydroxyapatite cement has dramatically decreased the rate of postoperative cerebrospinal fluid leak in translabyrinthine surgery, its use has also brought a new set of considerations. This study suggests that hydroxyapatite cement removal in the setting of postoperative hematoma after translabyrinthine surgery would require drilling rather than bedside incisional opening alone. Like standard craniotomy approaches, postoperative hemorrhage management requires intraoperative drainage.

Biomechanical behavior of MRI-signal-inducing bone cements after vertebroplasty in osteoporotic vertebral bodies: An experimental cadaver study

BACKGROUND

Conventional water-free polymethylmethacrylate cements are not MRI visible due to the lack of free protons. A new MRI-visible bone cement was developed through the addition of a contrast agent and either a saline solution or a hydroxyapatite (Wichlas et al., 2010). The purposes of the study were to examine the influence of the two MRI-signal-inducing cements on the biomechanical behavior of cadaveric osteoporotic vertebral bodies after vertebroplasty and to compare the performance of the cements with conventional polymethylmethacrylate cement.

METHODS

Three different cements were used: standard polymethylmethacrylate cement and two modified MRI-signal-inducing cements that were mixed with either a 0.9% saline solution or a hydroxyapatite. The modulus of elasticity for the standard polymethylmethacrylate cement was 2040MPa, and the moduli for the MRI-signal-inducing cements that were mixed with a 0.9% saline solution and a hydroxyapatite were 1477 and 1225MPa, respectively. The lumbar vertebral bodies from nine osteoporotic spines (mean age=87 years, range=78-99 years) of female cadavers were examined. Three groups were formed: polymethylmethacrylate cement with saline solution (n=14), polymethylmethacrylate cement with hydroxyapatite (n=12) and polymethylmethacrylate cement (n=13). The vertebral bodies were biomechanically tested before and after vertebroplasty. Stiffness was chosen as the primary biomechanical parameter.

FINDINGS

The vertebral body stiffness was nearly two-fold greater after vertebroplasty, and this increase was statistically significant for every group. All the groups had similar vertebral body stiffness value before and after the vertebroplasty. The UNIANOVA test for multivariate analysis of variance showed no influence of lumbar level, injected cement volume and initial vertebral body stiffness.

INTERPRETATION

The elastic moduli of the cements appear to exert little influence on the biomechanical values when the cement is in the vertebral body. Based on the direct comparison with the classic polymethylmethacrylate cement, we believe that the implementation of such cements for MRI-guided vertebroplasties is feasible.

Self-setting calcium orthophosphate formulations

In early 1980s, researchers discovered self-setting calcium orthophosphate cements, which are bioactive and biodegradable grafting bioceramics in the form of a powder and a liquid. After mixing, both phases form pastes, which set and harden forming either a non-stoichiometric calcium deficient hydroxyapatite or brushite. Since both of them are remarkably biocompartible, bioresorbable and osteoconductive, self-setting calcium orthophosphate formulations appear to be promising bioceramics for bone grafting. Furthermore, such formulations possess excellent molding capabilities, easy manipulation and nearly perfect adaptation to the complex shapes of bone defects, followed by gradual bioresorption and new bone formation. In addition, reinforced formulations have been introduced, which might be described as calcium orthophosphate concretes. The discovery of self-setting properties opened up a new era in the medical application of calcium orthophosphates and many commercial trademarks have been introduced as a result. Currently such formulations are widely used as synthetic bone grafts, with several advantages, such as pourability and injectability. Moreover, their low-temperature setting reactions and intrinsic porosity allow loading by drugs, biomolecules and even cells for tissue engineering purposes. In this review, an insight into the self-setting calcium orthophosphate formulations, as excellent bioceramics suitable for both dental and bone grafting applications, has been provided.

Recent developments of functional scaffolds for craniomaxillofacial bone tissue engineering applications

Autogenous bone grafting remains a gold standard for the reconstruction critical-sized bone defects in the craniomaxillofacial region. Nevertheless, this graft procedure has several disadvantages such as restricted availability, donor-site morbidity, and limitations in regard to fully restoring the complicated three-dimensional structures in the craniomaxillofacial bone. The ultimate goal of craniomaxillofacial bone reconstruction is the regeneration of the physiological bone that simultaneously fulfills both morphological and functional restorations. Developments of tissue engineering in the last two decades have brought such a goal closer to reality. In bone tissue engineering, the scaffolds are fundamental, elemental and mesenchymal stem cells/osteoprogenitor cells and bioactive factors. A variety of scaffolds have been developed and used as spacemakers, biodegradable bone substitutes for transplanting to the new bone, matrices of drug delivery system, or supporting structures enhancing adhesion, proliferation, and matrix production of seeded cells according to the circumstances of the bone defects. However, scaffolds to be clinically completely satisfied have not been developed yet. Development of more functional scaffolds is required to be applied widely to cranio-maxillofacial bone defects. This paper reviews recent trends of scaffolds for crania-maxillofacial bone tissue engineering, including our studies.

Autologous fat transplantation for the temporalis muscle flap donor site: our experience with 45 cases

BACKGROUND

Temporal depression after temporalis muscle flap transposition is characterized by a concavity of the soft tissue and associated with the relief of the orbital rim and zygomatic arch. The purpose of this study was to describe the use of autologous fat grafting for the treatment of postsurgical temporal contour deformities.

METHODS

Between March 2008 and April 2011, 45 patients were treated with lipofilling. A virtual 3-dimensional preoperative assessment was used to objectively quantify the loss of volume of the affected side. Two different methods were used to evaluate the surgical outcomes.

RESULTS

A noticeable soft tissue augmentation of the temporal region was noted in all cases. In 35 patients, a second procedure was required and in 1 patient, a third procedure was required. The final result was assessed as fully satisfactory by 39 patients (86.6%), as satisfactory by 5 patients (11.1%), and as unsatisfactory by 1 patient (2.2%).

CONCLUSION

We believe that structural fat grafting at the temporalis muscle flap donor site is an effective technique that provides a high satisfaction rate and only a few complications.

Cimento de aluminato de cálcio: uso em defeitos ósseos induzidos em fêmur de coelhos

Avaliou-se o comportamento do cimento de aluminato de cálcio em defeitos ósseos induzidos experimentalmente em fêmur de 12 coelhos Nova Zelândia Branco, distribuídos em três grupos experimentais, correspondentes aos tempos de observação pós-operatória de 15 (G15), 30 (G30) e 60 (G60) dias. Realizaram-se avaliações clínico-cirúrgicas, radiográficas e histológicas, a fim de se observar o potencial osteoindutor e osteocondutor do biomaterial no defeito ósseo, e se houve osteointegração. O cimento de aluminato de cálcio, na formulação utilizada, mostrou-se biocompatível, porém não atuou como osteocondutor ou osteoindutor.

Comparative analysis on the efficiency of the injection laryngoplasty technique using calcium hydroxyapatite (CaHA): the thyrohyoid approach versus the cricothyroid approach

OBJECTIVES

Temporary or permanent vocal paralysis can occur after head and neck surgery for thyroid cancer, esophageal resection, a chest operation that includes lung parenchymal resection due to a vagus or recurrent laryngeal nerve injury, and so forth. These days, the main treatment for vocal fold paralysis is the injection laryngoplasty through the cricothyroid (CT) approach. However, the CT approach is difficult in that an operator cannot see from the tip of the needle to the vocal fold. The aim of this study was to determine the efficacy of the thyrohyoid (TH) approach compared with the CT approach using calcium hydroxyapatite (CaHA) in patients with permanent unilateral vocal fold palsy.

METHODS

From March 2008 to July 2012, 68 consecutive injection laryngoplasties were performed in patients with unilateral glottic insufficiency. Percutaneous injection was performed under local anesthesia into the vocalis muscle, using disposable 25 gauge, 11cm long spinal needles through the CT membrane or TH membrane. Of the 68 patients, videostroboscopic findings and acoustic, perceptual, and subjective evaluations were completed for 64 patients before injection and at 3 months after injection.

RESULTS

In the 64 patients, the CT and TH approaches were used in 30 and 34 patients, respectively. The videostroboscopic findings, acoustic and perceptual parameters (maximum phonation time, jitter, shimmer, and noise-to-harmonic ratio), and Voice Handicap Index significantly improved after the injection in both the CT and TH groups (P<0.05).

CONCLUSION

Based on the results of this trial, injection laryngoplasty using the TH approach is an effective alternative to the CT approach, especially for the injection of CaHA in patients with permanent unilateral vocal fold palsy.

Frontal bone remodeling for gender reassignment of the male forehead: a gender-reassignment surgery

Gender-reassignment therapy, especially for reshaping of the forehead, can be an effective treatment to improve self-esteem. Contouring of the cranial vault, especially of the forehead, still is a rarely performed surgical procedure for gender reassignment. In addition to surgical bone remodeling, several materials have been used for remodeling and refinement of the frontal bone. But due to shortcomings of autogenous bone material and the disadvantages of polyethylene or methylmethacrylate, hydroxyapatite cement (HAC) composed of tetracalcium phosphate and dicalcium phosphate seems to be an alternative. This study aimed to analyze the clinical outcome after frontal bone remodeling with HAC for gender male-to-female reassignment. The 21 patients in the study were treated for gender reassignment of the male frontal bone using HAC. The average age of these patients was 33.4 years (range, 21–42 years). The average volume of HAC used per patient was 3.83 g. The authors’ clinical series demonstrated a satisfactory result. The surgery was easy to perform, and HAC was easy to apply and shape to suit individual needs. Overall satisfaction was very high. Therefore, HAC is a welcome alternative to the traditional use of autogenous bone graft for correction of cranial vault irregularities.

Biomaterials and implants for orbital floor repair

Treatment of orbital floor fractures and defects is often a complex issue. Repair of these injuries essentially aims to restore the continuity of the orbital floor and to provide an adequate support to the orbital content. Several materials and implants have been proposed over the years for orbital floor reconstruction, in the hope of achieving the best clinical outcome for the patient. Autografts have been traditionally considered as the "gold standard" choice due to the absence of an adverse immunological response, but they are available in limited amounts and carry the need for extra surgery. In order to overcome the drawbacks related to autografts, researchers' and surgeons' attention has been progressively attracted by alloplastic materials, which can be commercially produced and easily tailored to fit a wide range of specific clinical needs. In this review the advantages and limitations of the various biomaterials proposed and tested for orbital floor repair are critically examined and discussed. Criteria and guidelines for optimal material/implant choice, as well as future research directions, are also presented, in an attempt to understand whether an ideal biomaterial already exists or a truly functional implant will eventually materialise in the next few years.

Spontaneous cerebrospinal fluid leaks in congenital and acquired temporal bone defects-a long-term follow-up

Twelve patients presenting with tegmen defects and requiring surgical repair were retrospectively reviewed from 1982 to 1993. One half of the patients presented with a cerebrospinal fluid leak at some time in the course of their illness. Nine cases were considered to be acquired, secondary to previous mastoid surgery or trauma. All 9 had encephalocoeles. Three spontaneous leaks were considered congenital; 2 of these patients had encephalocoeles. This report represents a long-term follow-up of these cases, with an average follow-up of 7,6 years. Computed tomography and magnetic resonance imaging technology, as well as contrast studies, have tremendously aided in diagnosis and planning of surgical repair. Nine repairs were done through a dual transmastoid and middle fossa approach, with the other 3 done via a transmastoid approach only. We favored temporalis muscle flaps and temporalis fascia over synthetic materials for defect repairs. The long-term results and complications are discussed.

Influence of mixing blood with calcium phosphate bone paste on hardening

Calcium phosphate bone paste (CPP) has been recently introduced as a reconstructive material in craniofacial surgery. However, we observed that mixing of blood and CPP tended to interfere with CPP hardening. In addition, CPP mixed with blood tended to be absorbed postoperatively. Hence, we used a rabbit model and applied CPP mixed with blood over defects in the skull to investigate the influence of blood on CPP. Calcium phosphate bone paste was mixed with blood for 1 minute and applied to the defects in the calvarial bone of rabbits. At 4 and 24 postoperative weeks, we histologically evaluated morphologic changes in the hydroxyapatite (HA). Our study revealed that HA was not absorbed when a small quantity of blood (15%) was mixed with CPP. However, HA was absorbed almost entirely when a large quantity of blood (30%) was mixed with CPP. In addition, we found that the porosity of HA was increased by the mixture of a small quantity of blood into CPP, and this addition stimulated osteogenesis in HA.

In vivo performance of bilayer hydroxyapatite scaffolds for bone tissue regeneration in the rabbit radius

The objective of this study was to investigate the in vivo biomechanical performance of bone defects implanted with novel bilayer hydroxyapatite (HAp) scaffolds that mimic the cortical and cancellous organization of bone. The scaffolds maintained architectural continuity in a rabbit radius segmental defect model and were compared to an untreated defect group (negative control) and autologous bone grafts (positive control). Micro-CT evaluations indicated total bone and scaffold volume in the experimental group was significantly greater than the defect group but lesser than the autologous bone graft treatment. The flexural toughness of the scaffold and the autograft groups was significantly greater than the flexural toughness of the defect group. Interestingly, the absolute density of the bone mineral as well as calcium to phosphorus (Ca/P) ratio in that mineral for the scaffold and autograft contralateral bones was significantly higher than those for the defect contralaterals suggesting that the scaffolds contributed to calcium homeostasis. It was concluded from this study that new bone regenerated in the bilayer HAp scaffolds was comparable to the empty defects and while the HAp scaffolds provided significant increase in modulus when compared to empty defect and their flexural toughness was comparable to autografts after 8 weeks of implantation.

Use of rapidly hardening hydroxyapatite cement for facial contouring surgery

Hydroxyapatite cement is an ideal alloplastic material to replace the autogenous bone grafts in craniofacial surgery. Hydroxyapatite cement is advantageous because it can be easily molded by hand unlike other alloplastic materials such as silicone and high-density polyethylene. For aesthetic applications of hydroxyapatite cement, we evaluated the efficacy and safety of the rapidly hardening hydroxyapatite cement used in facial contour augmentation, especially for the forehead and the malar area. A total of 18 cases of facial skeleton augmentation or contouring surgery using rapidly hardening hydroxyapatite cement (Mimix; Biomet, Warsaw, IN) were examined, and the long-term cosmetic results and any complications were also analyzed. The aims of facial contouring surgeries were to correct the following conditions: hemifacial microsomia, craniosynostosis, posttraumatic facial deformity, deformity after tumor resection, dentofacial deformity, and Romberg disease. The application sites of hydroxyapatite cement were the forehead, malar area, chin, and paranasal area. A mean of 16 g (range, 5-50 g) of the hydroxyapatite cement was used. Postoperative infection, seroma, and migration of the implant were not observed during the follow-up period of 23 months. Rapidly hardening hydroxyapatite cement, Mimix, is easy to manipulate, promptly sclerotized, and can be replaced by living bone tissue, with a low complication rate. Therefore, it can be an optimal treatment that can be used instead of other conventional types of alloplastic materials used in facial contouring surgery.

Calcium orthophosphates as bioceramics: state of the art

In the late 1960s, much interest was raised in regard to biomedical applications of various ceramic materials. A little bit later, such materials were named bioceramics. This review is limited to bioceramics prepared from calcium orthophosphates only, which belong to the categories of bioactive and bioresorbable compounds. There have been a number of important advances in this field during the past 30-40 years. Namely, by structural and compositional control, it became possible to choose whether calcium orthophosphate bioceramics were biologically stable once incorporated within the skeletal structure or whether they were resorbed over time. At the turn of the millennium, a new concept of calcium orthophosphate bioceramics-which is able to promote regeneration of bones-was developed. Presently, calcium orthophosphate bioceramics are available in the form of particulates, blocks, cements, coatings, customized designs for specific applications and as injectable composites in a polymer carrier. Current biomedical applications include artificial replacements for hips, knees, teeth, tendons and ligaments, as well as repair for periodontal disease, maxillofacial reconstruction, augmentation and stabilization of the jawbone, spinal fusion and bone fillers after tumor surgery. Exploratory studies demonstrate potential applications of calcium orthophosphate bioceramics as scaffolds, drug delivery systems, as well as carriers of growth factors, bioactive peptides and/or various types of cells for tissue engineering purposes.

Calcium phosphate-based composites as injectable bone substitute materials

A major weakness of current orthopedic implant materials, for instance sintered hydroxyapatite (HA), is that they exist as a hardened form, requiring the surgeon to fit the surgical site around an implant to the desired shape. This can cause an increase in bone loss, trauma to the surrounding tissue, and longer surgical time. A convenient alternative to harden bone filling materials are injectable bone substitutes (IBS). In this article, recent progress in the development and application of calcium phosphate (CP)-based composites use as IBS is reviewed. CP materials have been used widely for bone replacement because of their similarity to the mineral component of bone. The main limitation of bulk CP materials is their brittle nature and poor mechanical properties. There is significant effort to reinforce or improve the mechanical properties and injectability of calcium phosphate cement (CPC) and this review resumes different alternatives presented in this specialized literature.