Applications of fast-setting hydroxyapatite cement: cranioplasty

Icing and multilayering technique of injectable hydroxyapatite cement paste for cranial base reconstruction after transsphenoidal surgery: technical note

OBJECTIVE

Injectable hydroxyapatite cement (HAC, Biopex; Mitsubishi Pharma Corp., Osaka, Japan) can reconstruct the accurate contour of bone defects intraoperatively, and it is slowly replaced with bone by a process of resorption and osteoconduction, making it a useful substrate for the repair of cranial defects. In the operative site with continuous oozing of the cerebrospinal fluid, however, the implanted HAC may be dissolved and washed out as a result of its water solubility during the setting time. For successful reconstruction of cranial defects in such wet situations, we describe a new technique to reinforce the implanted HAC with a multilayered application.

METHODS

As a preliminary experiment, we observed that the setting process of the HAC was severely restricted by the environmental temperature. At a temperature of 5 degrees C, the initial setting time of the HAC could be extended to 10 hours after the beginning of the mixing of the HAC. Bone defects of the sellar floor after transsphenoidal surgery for pituitary adenomas, craniopharyngiomas, meningiomas, or suprasellar arachnoid cysts were reconstructed using the HAC in 55 patients during a 5-year period. The results and complications were obtained through retrospective review.

RESULTS

Ninety-eight percent of bone defects were successfully repaired using the HAC, and the reconstruction remained stable over the course of this study. There was one case of postoperative cerebrospinal fluid leakage. Wound infection occurred in one patient, which required reoperation and removal of the biomaterial.

CONCLUSION

The icing and multilayering method for proper use of this biomaterial resulted in restoration of the integrity of the cranial base bone and a decrease of cerebrospinal fluid leakage as a postoperative complication of transsphenoidal surgery. HAC is a biomaterial that is recommended to be used as the primary method for reconstructing cranial base bone defects.

Use of Calcium-Based Bone Cements in the Repair of Large, Full-Thickness Cranial Defects: A Caution

BACKGROUND

Calcium-based bone cements have increased in popularity for the correction of craniofacial contour defects. The authors' experience with them in more than 120 patients has resulted in the establishment of strict criteria for their use. Although the authors' overall complication rate with these cements has been low, certain patient groups have an unacceptably high complication rate. The authors describe their experience with the repair of large, full-thickness cranial defects using calcium-based bone cements.

METHODS

The study group comprised 16 patients who underwent correction of large, full-thickness (>25 cm2) skull defects. The surgical technique included reconstruction of the floor of the defect with rigid fixation to the surrounding native bone, interposition of the cement to ideal contour, and closure of the defect.

RESULTS

The mean patient age was 35 years (range, 1 to 69 years). The mean defect area was 66.4 cm2 (range, 30 to 150 cm2). Cases were equally divided between BoneSource and Norian CRS. The mean amount of bone cement used was 80 g. Follow-up varied between 1 and 6 years (mean, 3 years). Major complications occurred in eight of 16 patients, with one occurring as late as 6 years postoperatively. Complications occurred throughout the course of review, indicating that they were not caused by a learning curve.

CONCLUSION

Because of the unacceptably high complication rate with the use of calcium-based bone cements in large skull defects, the authors believe that their use is contraindicated and have returned to using autogenous split skull cranial bone reconstruction for these patients.

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

BACKGROUND

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

The mechanical properties and osteoconductivity of hydroxyapatite bone scaffolds with multi-scale porosity

The relative osteoconductivity and the change in the mechanical properties of hydroxyapatite (HA) scaffolds with multi-scale porosity were compared to scaffolds with a single pore size. Non-microporous (NMP) scaffolds contained only macroporosity (250-350 microm) and microporous (MP) scaffolds contained both macroporosity and microporosity (2-8 microm). Recombinant human bone morphogenetic protein-2 (rhBMP-2) was incorporated into all scaffolds via gelatin microspheres prior to implantation into the latissimus dorsi muscle of Yorkshire pigs. After 8 weeks, only the MP scaffolds contained bone. The result demonstrates the efficacy of the MP scaffolds as drug carriers. Implanted and as-fabricated scaffolds were compared using histology, microcomputed tomography, scanning electron microscopy, and compression testing. Implanted scaffolds exhibited a stress-strain response similar to that of cancellous bone with strengths between those of cancellous and cortical bone. The strength and stiffness of implanted NMP scaffolds decreased by 15% and 46%, respectively. Implanted MP scaffolds lost 30% of their strength and 31% of their stiffness. Bone arrested crack propagation effectively in MP scaffolds. The change in mechanical behavior is discussed and the study demonstrates the importance of scaffold microporosity on bone ingrowth and on the mechanical behavior of HA implant materials.

Contouring of Cranial Vault Irregularities With Hydroxyapatite Cement: A Clinical and Experimental Investigation

The biocompatible hydroxyapatite cement (HAC) is a welcome alternative to the traditional use of autogenous bone for postoperative corrections of cranial vault irregularities. The authors performed experimental studies to show the safety and osseointegration capacity of HAC on animal models and confirm the osseous replacement without toxic reactions. The purpose of the current study was to analyze the clinical outcome after correction of secondary cranial vault irregularities with HAC. Twenty-one patients were treated for residual cranial frontal bone defects after craniotomy with HAC (Bone Source, Stryker Leibinger GmbH, D-79111 Freiburg, Germany). The average age was 38.5 years (range, 23-57 years). All of the patients were male. The average volume per patient was 53.83 g. The volume implanted ranged from 25 to 125 g; in all cases the dura was covered with bone. Irregularities resulted from sunken bone. The authors' clinical series demonstrates that a satisfactory and aesthetically pleasing result can be achieved in one surgical intervention in patients for surgical correction of postoperative cranial vault irregularities using HAC. It permits osseointegration, which makes it relatively resistant to infection. HAC is easy to apply and shape to suit individual needs. HAC is a welcome alternative to the traditional use of autogenous bone for postoperative corrections of cranial vault irregularities.

Antibiotic Elution from Hydroxyapatite Cement Cranioplasty Materials

Hydroxyapatite cements (HAC) are a contemporary material used for multiple cranioplasty applications. In an effort to decrease the risk of postoperative infection, mixing antibiotics into the material during intraoperative application is frequently done. It has been assumed, but never substantiated, that significant antibiotic release from the material occurs after implantation. Using standardized morphologies, a mixture of a specific HAC (Mimix bone void filler) and tobramycin antibiotic was prepared, hydrated in phosphate-buffered saline, and tested in vitro for as long as 22 days after preparation. The results show that the majority of the antibiotic (91%) was released within the first 24 hours, with the balance being eluted during the next 8 days. Overall, the release of tobramycin from Mimix bone void filler appears to fit the pattern of antibiotic release demonstrated to occur from other bioabsorbable ceramic-type carriers.

Experimental facial augmentation with hydroxyapatite cement

OBJECTIVE

To study the results of implantation of preformed hydroxyapatite (HA) disks and HA cement in onlay augmentation.

METHODS

In this prospective study involving 16 adult New Zealand rabbits, HA disk and HA cement samples were implanted separately and together along the bony and cartilaginous nasal dorsum as well as over the supraorbital bone. Gross and histologic examinations of the implants were performed at intervals ranging from 3 to 24 months.

RESULTS

There was no evidence of infection, adverse reaction, or implant extrusion in the 15 rabbits surviving the planned period. Grossly, all rabbits had prominent noses and supraorbital regions that were immobile on digital palpation. No measurable change in HA disk height and width was noted but there was a 15% decrease in height and width in the HA cement implant. Microscopically, preformed HA disks were found to be enclosed in a vascularized fibrous capsule. When disks were combined with HA cement, a vascular fibrous capsule was still noted around the implant but there was osteoconversion in the underlying cement layer. Used alone, HA cement underwent both osteoconversion and osteointegration. Neither the preformed HA disk with and without HA cement nor the HA cement alone elicited giant cell reaction or inflammatory changes. The HA cement alone was found to have microscopic fissures at the edges.

CONCLUSION

This animal study suggests that preformed HA implants and HA cement, alone or in combination, can be used to augment the non-stress-bearing craniofacial skeleton.

Frei modellierbare Hydroxylapatit-Kollagen-Komposite zur Sanierung oss�rer Defekte

AIM

In the following study we evaluated the biological response of a new freely moldable bone substitute in an animal model.

MATERIAL AND METHODS

Critically sized defects were created surgically in the lower jaw of ten adult minipigs. The drill defects were filled with hydroxyapatite collagen paste. After observation periods of 1, 3, 6, 12, and 18 months the mandibles were harvested without wound healing defects for histological evaluation of resorption and bone ingrowth with a sawing and grinding technique.

RESULTS

The result of the remodeling process was a complete degradation of hydroxyapatite collagen implants after 12-18 months with reorganization of vital trabeculae oriented in a mature pattern.

CONCLUSION

The hydroxyapatite collagen cement works as an osteoconductor and shows signs of direct osseointegration and resorption.

Complication Rate of Transtemporal Hydroxyapatite Cement Cranioplasties: A Case Series Review of 76 Cranioplasties

OBJECTIVE

The objective of this study was to evaluate the complication rate of transtemporal cranioplasties using hydroxyapatite cement (HAC) for repair.

STUDY DESIGN

We conducted a retrospective case review of patients receiving HAC cranioplasties in the Acoustic Neuroma and Skull Base Surgery Program between July 1998 and December 2002.

SETTING

This study was conducted at a tertiary referral center.

PATIENTS

A total of 76 HAC cranioplasties were performed in 72 patients undergoing lateral skull base surgery. Patients undergoing anterior skull base surgery or those in which HAC was used for other reconstructive purposes were excluded from the study.

INTERVENTIONS

We studied transtemporal approaches for otologic procedures requiring cranioplasty.

MAIN OUTCOME MEASURES

Main outcomes measures consisted of complications requiring medical or surgical intervention.

RESULTS

Of the 76 HAC cranioplasties, two cranioplasty grafts became infected, requiring explantation. The first case involved a wound infection that extended into and involved the HAC graft; the second involved seeding of the HAC graft after meningitis after a percutaneous, endoscopic gastrostomy tube placement performed several days after the primary skull base surgery. This gives our series a wound infection incidence rate of 1.3% and an overall complication incidence rate of 2.63%.

CONCLUSIONS

This retrospective review provides the largest series to date evaluating the incidence of infection in HAC cranioplasties. Despite having a much larger series, our complication rate is the lowest published rate of HAC cranioplasty explantation, and the incidence of superficial wound infections reported here is consistent with the published data for neurosurgical and neurotologic procedures.

Ossicular Reconstruction Using Bone Cement

OBJECTIVE

The objective of this study was to describe our results of ossicular reconstruction using bone cement.

STUDY DESIGN

We conducted a retrospective review of 264 patients with chronic suppurative otitis media operated on since 1999.

SETTING

Academic tertiary referral center.

PATIENTS

: Two hundred sixty-four patients with chronic suppurative otitis media underwent mastoidectomy with tympanoplasty. Eighty patients had incudostapedial disarticulation secondary to infection and or cholesteatoma and were reconstructed using an incus interposition graft (n = 31), a partial ossicular prosthesis (POP; n = 31), or more recently, bone source (n = 18). This study evaluates the results of the ossiculoplasties using bone source.

INTERVENTION

Ossicular discontinuity was repaired using bone cement.

MAIN OUTCOME MEASURE

Audiometric studies pre- and postintervention were compared. One to 3 years of follow up are provided.

RESULTS

Preoperative air-bone gaps ranged from 18 dB to 60 dB and averaged 33 dB. Postoperative air-bone gaps ranged from 1 to 24 dB and averaged 10 dB. No patients have experienced any increase in their persistent conductive hearing loss. The pre-/postoperative hearing loss comparisons showed statistically significant hearing improvement. There were no complications.

CONCLUSION

The use of POPs and incus interposition grafts is fraught with the possibility of migration and resultant recurrent conductive hearing loss. Using bone cement to reconstruct the ossicular chain restores the integrity of the ossicular chain in the most natural of ways. This reconstruction technique provides an excellent alternative to currently accepted methods and should be considered for incus-stapes disarticulation. There has been no dissolution of the bone source and the results have persisted thus far.

The Fate of Hydroxyapatite Cement Used for Cranial Contouring: Histological Evaluation of a Case

Craniofacial contouring is a commonly performed procedure applied for traumatic and postsurgical cranial vault or facial skeleton irregularities. Hydroxyapatite cement is an alloplastic material composed of tetracalcium phospate and dicalcium phospate anhydrous that transforms into a paste-like substance when these two compounds placed in an aqueous environment. This mixture, which is a nonceramic microporous calcium phosphate combination, is another alternative for refining the craniofacial contour. There are not enough data regarding bone formation within this material after its use in human beings, however. A case requiring secondary craniofacial contouring after a motor vehicle accident is presented. Hydroxyapatite cement was used for reconstruction, and a second look was carried out for further correction during which secondary contouring of the cement was made and a sample of the previously implanted material was histologically evaluated. It was observed in this case that hydroxyapatite cement is incorporated within the surrounding bony structures and permits secondary contouring procedures. New bone and vessel formation was also detected within the implanted material, but this was limited and thus was not convincing for significant osteoconversion as seen in animal studies.

Repair of calvarial defects in rats by prefabricated hydroxyapatite cement implants

The aim of the present study was to test the hypothesis that calvarial defects can be repaired by using preformed implants of calcium phosphate bone cement (CPBC) in rats. Sixty adult female Sprague-Dawley rats received full-thickness calvarial nonhealing defects with a diameter of 8 mm. Three different CPBCs were used: group 1: tetracalcium phosphate-based powder; group 2: a blend of amorphous and crystalline calcium phosphate precursors; and group 3: an alpha-tricalcium phosphate (alpha-TCP)-based powder. Implants were left to cure for 25-40 min at room temperature in a silicon mold of 7.9 mm and inserted press fit into the defects. Fifteen animals served as unfilled controls. After 13, 26, and 52 weeks, the material was analyzed qualitatively by using surface-stained undecalcified thick-section specimens and quantitatively by using semiautomated histometry. Kruskal-Wallis tests were applied to compare mean values of periimplant bone formation at a significance level of p < 0.05. Three implants of group 1 fractured during insertion. Resorption of CPBC without complementary bone formation was noticed in these implants. Unfractured implants were resorbed with simultaneous apposition of bone on the implant surface. After 52 weeks, the resorption rate varied between 23.1 and 39.3%. Periimplant bone formation increased continuously on average around all implant types, but it reached statistical significance only in group 2. The results showed that repair of calvarial defects can be achieved by preformed CPBC implants. The rate of resorption of preformed implants is, however, much lower than that reported for in vivo cured CPBC.

Osteogenic Differentiation of Human Bone Marrow Stromal Cells on Partially Demineralized Bone Scaffoldsin Vitro

Tissue engineering has been used to enhance the utility of biomaterials for clinical bone repair by the incorporation of an osteogenic cell source into a scaffold followed by the in vitro promotion of osteogenic differentiation before host implantation. In this study, three-dimensional, partially demineralized bone scaffolds were investigated for their ability to support osteogenic differentiation of human bone marrow stromal cells (BMSCs) in vitro. Dynamic cell seeding resulted in homogeneous cell attachment and infiltration within the matrix and produced significantly higher seeding efficiencies when compared with a conventional static seeding method. Dynamically seeded scaffolds were cultured for 7 and 14 days in the presence of dexamethasone and evaluated on biochemical, molecular, and morphological levels for osteogenic differentiation. Significant elevation in alkaline phosphatase activity was observed versus controls over the 14-day culture, with a transient peak indicative of early mineralization on day 7. On the basis of RT-PCR, dexamethasone-treated samples showed elevations in alkaline phosphatase and osteocalcin expression levels at 7 and 14 days over nontreated controls, while bone sialoprotein was produced only in the presence of dexamethasone at 14 days. Scanning electron microscopy evaluation of dexamethasone-treated samples at 14 days revealed primarily cuboidal cells indicative of mature osteoblasts, in contrast to nontreated controls displaying a majority of cells with a fibroblastic cell morphology. These results demonstrate that partially demineralized bone can be successfully used with human BMSCs to support osteogenic differentiation in vitro. This osseous biomaterial may offer new potential benefits as a tool for clinical bone replacement.

Correction of large (>25 cm(2)) cranial defects with "reinforced" hydroxyapatite cement: technique and complications

INTRODUCTION

Hydroxyapatite cement is both biocompatible and osteoconductive, and it lacks significant toxic or immunogenic properties, making it an ideal substrate for the repair of cranial defects. However, with its putty-like composition, the repair of large cranial defects can be difficult because significant settling occurs as the cement hardens. We describe a technique in which we use hydroxyapatite cement, reinforced with tantalum mesh and titanium miniplates, for the repair of large (>25 cm(2)) cranial defects.

METHODS

After the margins of the cranioplasty are delineated, tantalum mesh is placed under the edges of the defect. Titanium miniplate single-hole bars are used to criss-cross the defect and are then secured to the surrounding bone with screws. The mesh is secured to the bars with 28-gauge stainless steel wire. Hydroxyapatite cement is applied in the defect and contoured appropriately.

RESULTS

We performed nine cranioplasties in eight patients ranging in age from 1.5 to 35 years (mean, 12.2 +/- 10.1 yr). The reasons for cranioplasty included cranial defect from prior trauma (n = 4), fibrous dysplasia (n = 2), infected bone flaps (n = 2), and tumor (n = 1). The cranioplasties ranged in size from 40 to 196 cm(2) (mean, 128.3 +/- 56.9 cm(2)). Follow-up ranged from 2 to 33 months (mean, 11.4 +/- 12.8 mo). Two cranioplasty constructs were removed at 1 and 3 months postoperatively owing to infection.

CONCLUSION

The use of hydroxyapatite cement with mesh and miniplates provides internal structural support and increased stability of the construct. Although this technique provides an excellent cosmetic result and no evidence to date of bony resorption, the rate of infection is alarmingly high in these large constructs.

Hydroxyapatite cranioplasty: 2. Clinical experience with a new quick-setting material

A clinical series of 62 patients who underwent cranioplasty using a new quick-setting hydroxyapatite (HA) material was done over a 2-year period. The majority of procedures (69%) were performed for secondary reconstruction of frontal, temporal, and supraorbital deficiencies after primary repair of a craniosynostosis. The frontal sinus was obliterated as part of the cranioplastic procedure in 5 cases (8%) in older patients. The material set effectively in approximately 5 minutes with a good working time. Infection occurred in 3 patients (5%) which was treated by removing the HA cranioplastic material. This faster-setting HA material offers similar cranioplastic benefits as other materials but with an accelerated intraoperative set time.

Hydroxyapatite cement cranioplasty in translabyrinthine acoustic neuroma surgery

OBJECTIVES

Hydroxyapatite cement cranioplasty (HAC) after translabyrinthine resection of acoustic neuroma is a promising new technique for wound reconstruction. This study reviews the efficacy of HAC for the prevention of cerebrospinal fluid (CSF) leakage and the long-term wound outcomes of HAC versus abdominal fat graft (AFG) reconstruction.

METHODS

This retrospective study of l08 consecutive acoustic neuromas operated on by Pittsburgh Ear Associates uses chart review, telephone interview, and mail questionnaire data. Fifty-four patients received AFG dural repair, and 54 patients received HAC.

RESULTS

Seven AFG patients (12.5%) had CSF leaks versus 2 (3.7%) of the overall group of 54 HAC patients. However, none (0%) of the 47 HAC patients had CSF leakage with current HAC techniques. HAC also produced significantly less postauricular wound depression and superior cosmetic results in comparison with AFG. Although HAC patients experienced less postoperative discomfort, wound complications requiring medical or surgical intervention were extremely uncommon in both groups.

CONCLUSION

HAC offers significant CSF leakage control and long-term cosmetic and comfort advantages over AFG alone. We recommend HAC as the standard closure technique for translabyrinthine acoustic neuroma surgery.

Titanium mesh and hydroxyapatite cement cranioplasty: a report of 20 cases

PURPOSE

This article describes the use of titanium mesh and hydroxyapatite cement constructs for the treatment of large through-and-through calvarial defects.

PATIENTS AND METHODS

Twenty consecutive calvarial defects (10 to 156 cm(2)) that resulted from surgical removal of neoplasms or were secondary to trauma were reviewed retrospectively after reconstruction with titanium mesh and hydroxyapatite cement. All patients were followed up by clinical examination and periodic radiographic studies for a minimum of 6 months (range, 6 months to 3 years). Three patients underwent biopsy of the construct at various points during their follow-up.

RESULTS

There was no evidence of adverse healing, wound infection, or implant exposure or extrusion in any of the patients reviewed. Adequate 3-dimensional aesthetic restoration of calvarial contour was noted in each case. There was evidence of osseous ingrowth into the titanium mesh and hydroxyapatite cement construct in all 3 patients who underwent biopsy.

CONCLUSION

Titanium mesh and hydroxyapatite cement cranioplasty appears to be a reasonable method for the reconstruction of significant calvarial defects.

Frontal sinus obliteration with hydroxyapatite cement

OBJECTIVE

To evaluate the efficacy hydroxyapatite cement as an alternative to autologous fat in the obliteration of the frontal sinus after trauma or chronic suppuration.

METHODS

Single institution, nonrandomized, prospective analysis of patients treated in an academic, tertiary care center. Patients were followed with physical examinations and were monitored for recurrent infections, which would have necessitated removal of the implant. Follow-up radiographs were obtained at 12 months. Standard surgical techniques were used to obliterate the frontal sinus with the addition of the placement of a vascularized pericardial flap along the frontal sinus floor.

RESULTS

Eleven patients underwent hydroxyapatite frontal sinus obliteration. There were 2 women and 9 men in the series with age ranges from 33 to 82 years (mean, 48 y). Three patients underwent obliteration for trauma and 8 for chronic infections with or without mucopyocele. The mean follow-up is 27 months (range, 3.3-37 mo). No patient has developed clinical or radiographic evidence of recurrent frontal sinusitis and at this point no implants have been removed. Nine of 11 patients (91%) report complete resolution of all symptoms.

CONCLUSION

Hydroxyapatite cement had demonstrated efficacy in full-thickness reconstruction of frontal sinus defects. The pericranial flap may provide a barrier to prevent infection of the implant in the face of acute ethmoid sinusitis. Hydroxyapatite cement offers the advantages of no donor site morbidity and the potential for complete osseointegration.