Applications of fast-setting hydroxyapatite cement: cranioplasty

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Clinical Impact of Hydroxyapatite on the Outcome of Skull Base Reconstruction for Intraoperative High-Flow CSF Leak: A Propensity Score Matching Analysis

Background

Despite recent advances in skull base reconstructive techniques, including the multilayer technique during the last decade, complete reconstruction of grade 3 intraoperative high-flow cerebrospinal fluid (CSF) leak remains challenging. This study was designed to investigate the role of injectable hydroxyapatite (HXA) used in the multilayer technique on the clinical outcome of skull base reconstruction for intraoperative high-flow CSF leak.

Materials and Methods

This study enrolled 187 patients who experienced intraoperative high-flow CSF leak after endoscopic endonasal surgery for anterior skull base or suprasellar pathologies between January 2014 and July 2021. All skull base defects were reconstructed using the conventional multilayer technique including a vascularized naso-septal flap (NSF, n = 141) and the combined use of HXA with the conventional multilayer technique (HXA group, n = 46). We retrospectively evaluated the efficacy of the HXA group by 1:2 propensity score matching analysis.

Results

Overall, 17 of 187 patients (9.1%) showed postoperative CSF leaks, resulting in second reconstruction surgery. There were no statistical differences in patient age, sex, body mass index, tumor location, tumor type, and degree of resection, except for the follow-up period between the two groups. The HXA group showed a significantly lower incidence of postoperative CSF leak than the control group (0% vs. 12.1%, p < 0.05). Postoperative lumbar drain (LD) was performed in 8.7% of the HXA group compared to 46.1% of the control group (p < 0.01). CSF leak-related infection rates showed a decreasing tendency in the HXA group compared to the control group (0 vs. 7.1%, p = 0.06). A total of 46 patients in the HXA group were well matched with the control group (92 patients) at a 1:2 ratio. In the propensity score-matched control group, there were higher rates of postoperative CSF leaks than in the HXA group.

Conclusion

The use of HXA combined with the conventional multilayer technique completely reduced postoperative CSF leaks in this study. This technique resulted in reduced CSF leakage, even without postoperative LD, and decreased infection rates. Further randomized comparative studies are required to confirm our findings.

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.

Graded Reconstruction Strategy Using a Multilayer Technique Without Lumbar Drainage After Endoscopic Endonasal Surgery

OBJECTIVE

Sellar reconstruction following endoscopic endonasal surgery (EES) requires modification based on the degree of cerebrospinal fluid (CSF) leak. For high-flow (grade II or III according to Esposito et al. 2007) intraoperative CSF leak, lumbar drainage (LD), in addition to the multilayer closing technique, is generally recommended. However, LD occasionally has complications including postpuncture headache, overdrainage symptoms, and increased length of stay. We retrospectively evaluated the outcome of our graded reconstruction strategy using a multilayer technique with a novel material, without LD, after EES.

METHODS

Ninety-seven patients who underwent EES with grade II or III intraoperative CSF leak between June 2020 and March 2021 were retrospectively reviewed. For grade II CSF leak, fibrin sealant and a nasoseptal flap were placed; for grade III CSF leak, a multilayer technique was used in combination with collagen matrix, an acellular dermal graft, injectable hydroxyapatite (HXA), and a nasoseptal flap. Postoperatively, routine LD was not performed.

RESULTS

This study included 48 (49.5%) grade II and 49 (50.5%) grade III CSF leaks. At follow-up (mean, 8.7 months), no patient showed postoperative CSF leak in either group. No HXA-associated complications occurred.

CONCLUSIONS

A graded surgical repair strategy after EES could avoid postoperative CSF leak. Combined use of injectable HXA and acellular dermal grafts for high-flow CSF leak can limit LD requirement without significant risks.

Decision-Making in Adult Cranial Vault Reconstruction

LEARNING OBJECTIVES

After studying this article, the participant should be able to: 1. Define and classify different types of cranial defects 2. Compare both autologous and alloplastic options for reconstruction 3. Develop an optimal approach for cranial vault reconstruction in various clinical scenarios.

SUMMARY

Defects of the cranium result from various causes, including traumatic loss, neurosurgical intervention, skull tumors, and infection. Cranial vault reconstruction aims to restore both the structural integrity and surface morphology of the skull. To ensure a successful outcome, the choice of appropriate cranioplasty reconstruction will vary primarily based on the cause, location, and size of the defect. Other relevant factors that must be considered include adequacy of soft-tissue coverage, presence of infection, and previous or planned radiation therapy. This article presents an algorithm for the reconstruction of various cranial defects using both autologous and alloplastic techniques, with a comparison of their advantages and disadvantages.

Comparative study of photoinitiators for the synthesis and 3D printing of a light-curable, degradable polymer for custom-fit hard tissue implants

Three-dimensional (3D) printing enhances the production of on-demand fabrication of patient-specific devices, as well as anatomically fitting implants with high complexity in a cost-effective manner. Additive systems that employ vat photopolymerisation such as stereolithography (SLA) and digital light projection are used widely in the field of biomedical science and engineering. However, additive manufacturing methods can be limited by the types of materials that can be used. In this study, we present an isosorbide-based formulation for a polymer resin yielding a range of elastic moduli between 1.7 and 3 GN mm^-2 dependent on the photoinitiator system used as well as the amount of calcium phosphate filler added. The monomer was prepared and enhanced for 3D-printing using an SLA technique that delivered stable and optimized 3D-printed models. The resin discussed could potentially be used following major surgery for the correction of congenital defects, the removal of oral tumours and the reconstruction of the head and neck region. The surgeon is usually limited with devices available to restore both function and appearance and with the ever-increasing demand for low-priced and efficient facial implants, there is an urgent need to advance new manufacturing approaches and implants with a higher osseointegration performance.

Use of Onlay Hydroxyapatite Cement for Secondary Cranioplasty

BACKGROUND

Children who undergo bi-fronto-orbital advancement (BFOA) frequently develop a contour deformity on the temporal and supra-orbital region, with an incidence reported as high as 55% and 75%, respectively. Up to 20% of patients may require correction. Hydroxyapatite cement (HAC) is a good alternative to autogenous tissue. The available literature on its use focusses on the reconstruction of bone defects, but little has been published on its efficacy and safety as an onlay graft over intact cranium.

OBJECTIVES

To describe our institution's experience with HAC in the pediatric population.

METHODS

Retrospective chart review from 1998 to 2018 on all patients from the Craniofacial Unit at the Sydney Children's Hospital who had either coronal or metopic craniosynostosis and underwent BFOA and later in life required cranioplasty with HAC for contour repair.

FINDINGS

We have performed 166 BFOA and nineteen secondary cranioplasties for contour repair using onlay HAC. The mean age at the time of operation was 14 years. Bi-coronal craniosynostosis was most frequently associated with secondary cranioplasty and 37% had an associated syndrome. The mean volume of HAC used was 37 mL. There was only 1 patient who had a complication (5.3%) and required partial removal of allograft. The mean length of admission was 2 days. Mean follow up time of 22.4 months.

CONCLUSIONS

HAC represents a safe option when used correctly, with low rates of complication and satisfactory cosmetic outcomes.

Alloplastic Cranioplasty Reconstruction: A Systematic Review Comparing Outcomes With Titanium Mesh, Polymethyl Methacrylate, Polyether Ether Ketone, and Norian Implants in 3591 Adult Patients

BACKGROUND

Acquired defects of the cranium represent a reconstructive challenge in patients with calvarial bone loss due to trauma, infection, neoplasia, congenital malformations, or other etiologies. The objective of this study was to compare postoperative rates of infection, local complications, and allograft failures following cranioplasty reconstruction using titanium mesh (Ti), polymethyl methacrylate (PMMA), polyether ether ketone (PEEK), and Norian implants in adult patients.

METHODS

This constitutes the first systematic review of available literature on 4 different methods of alloplastic cranioplasty reconstruction, including Ti, PMMA, PEEK, and Norian implants, using the Newcastle-Ottawa Quality Assessment Scale guidelines for article identification, screening, eligibility, and inclusion. Electronic literature search included Ovid MEDLINE/PubMed, EMBASE, Scopus, Google Scholar, and Cochrane Database. Pearson exact test was utilized at P < 0.05 level of significance (J.M.P. v11 Statistical Software).

RESULTS

A total of 53 studies and 3591 patients (mean age, 40.1 years) were included (Ti = 1429, PMMA = 1459, PEEK = 221, Norian = 482). Polymethyl methacrylate implants were associated with a significantly higher infection rate (7.95%, P = 0.0266) compared with all other implant types (6.05%). Polyether ether ketone implants were associated with a significantly higher local complication rate (17.19%, P = 0.0307, compared with 12.23% in all others) and the highest ultimate graft failure rate (8.60%, P = 0.0450) compared with all other implant types (5.52%).

CONCLUSIONS

This study qualifies as a preliminary analysis addressing the knowledge gap in rates of infection, local surgical complication, and graft failure in alloplastic cranioplasty reconstruction with different implant types in the adult population. Longer-term randomized trials are warranted to validate associations found in this study.

Cranioplasty after craniectomy in pediatric patients-a systematic review

INTRODUCTION

Complications following cranioplasty with either autografts or cranial implants are commonly reported in pediatric patients. However, data regarding cranioplasty strategies, complications and long-term outcomes are not well described. This study systematically reviews the literature for an overview of current cranioplasty practice in children.

METHODS

A systematic review of articles published from inception to July 2018 was performed. Studies were included if they reported the specific use of cranioplasty materials following craniectomy in patients younger than 18 years of age, and had a minimum follow-up of at least 1 year.

RESULTS

Twenty-four manuscripts, describing a total of 864 cranioplasty procedures, met the inclusion criteria. The age of patients in this aggregate ranged from 1 month to 20 years and the weighted average was 8.0 years. The follow-up ranged from 0.4 months to 18 years and had a weighted average of 40.4 months. Autologous bone grafts were used in 484 cases (56.0%). Resorption, infection and/or hydrocephalus were the most frequently mentioned complications. In this aggregate group, 61 patients needed a revision cranioplasty. However, in 6/13 (46%) papers studying autologous cranioplasties, no data was provided on resorption, infection and revision cranioplasty rates. Cranial implants were used in 380 cases (44.0%), with custom-made porous hydroxyapatite being the most commonly used material (100/380, 26.3%). Infection and migration/fracturing/loosening were the most frequently documented complications. Eleven revision cranioplasties were reported. Again, no data was reported on infection and revision cranioplasty rates, in 7/16 (44%) and 9/16 (56%) of papers, respectively.

CONCLUSION

Our systematic review illuminates that whether autografts or cranial implants are used, postcranioplasty complications are quite common. Beyond this, the existing literature does not contain well documented and comparable outcome parameters, suggesting that prospective, long-term multicenter cohort studies are needed to be able to optimize cranioplasty strategies in children who will undergo cranioplasty following craniectomy.

Cranioplasties following craniectomies in children-a multicenter, retrospective cohort study

OBJECTIVE

Complications following pediatric cranioplasty after craniectomy with either autologous bone flaps or cranial implants are reported to be common, particularly bone flap resorption. However, only sparse data are available regarding cranioplasty strategies, complications, and outcomes. This manuscript describes a Canadian-Dutch multicenter pediatric cohort study with autografts and cranial implant cranioplasties following craniectomies for a variety of indications.

METHODS

The study included all children (< 18 years) who underwent craniectomy and subsequent cranioplasty surgeries from 2008 to 2014 (with a minimum of 1-year follow-up) at four academic hospitals with a dedicated pediatric neurosurgical service. Data were collected regarding initial diagnosis, age, time interval between craniectomy and cranioplasty, bone flap storage method, type of cranioplasty for initial procedure (and redo if applicable), and the postoperative outcome including surgical site infection, wound breakdowns, bone flap resorption, and inadequate fit/disfigurement.

RESULTS

Sixty-four patients (46 males, average age 9.7 ± 5.5 years) were eligible for inclusion, with mean follow-up of 82.3 ± 31.2 months after craniectomy. Forty cranioplasties (62.5%) used autologous bone re-implant, 23 (57.5%) of which showed resorption. On average, resorption was documented at 434 days (range 62-2796 days) after reimplantation. In 20 cases, a revision cranioplasty was needed. In 24 of the post-craniectomy cases (37.5%), a cranial implant was used with one of ten different implant types. Implant loosening prompted a complete revision cranioplasty in 2 cases (8.3%). Cranial implants were associated with low morbidity and lower reoperation dates compared to the autologous cranioplasties.

CONCLUSION

The most prominent finding in this multicenter cohort study was that bone flap resorption in children remains a common and widespread problem following craniectomy. Cranioplasty strategies varied between centers and evolved over time within centers. Cranial implants were associated with low morbidity and low reoperation rates. Still, longer term and prospective multicenter cohort studies are needed to optimize cranioplasty strategies in children after craniectomies.

Trans-mastoid approach for cerebrospinal fluid leak repair

PURPOSE OF REVIEW

To describe the technique and discuss the advantages and outcomes of the trans-mastoid approach (TMA) for temporal bone cerebrospinal fluid (CSF) leak.

RECENT FINDINGS

TMA for CSF leak repair is an alternative to middle cranial fossa approach (MCFA) with less morbidity and good outcomes.

SUMMARY

Persistent CSF leak in the temporal bone whether idiopathic, congenital or acquired, is an indication for surgery. TMA is a valid option for surgery, competing with MCFA in selected cases. Surgical technique consists of a standard mastoidectomy, exposure of the osteodural defect, and repairing it using multiple layers in an inlay and overlay fashion. Outcomes show low recurrence and complication rates with good hearing results. However, long-term follow-up should be made, as recurrences can be delayed.

离体灭活多孔骨瓣结合BAM骨诱导人工骨修复大鼠颅骨缺损的效果评价

OBJECTIVE

To study the effect of BAM bone grafting combined with inactivated autologous porous bone flap in repairing skull defect in rats.

METHODS

Seventy-two Wistar rats with skull defect were randomly divided into control group, inactivated autologous bone flap group (AB group), BAM bone-induced artificial bone material group (BAM group), and inactivated autologous bone flap with BAM bone-induced artificial bone group (BAM+AB group). The bone healing was evaluated with micro-CT and the new bone formation was assessed with histological staining at 1, 2, and 3 months after modeling.

RESULTS

Inactivated porous bone flap combined with BAM bone-induced artificial bone effectively induced vascular and fibrous tissue regeneration and osteogenesis in the cranial defects. With the inactivated porous bone flap as the scaffold, BAM bone-induced artificial bone obviously promoted the restoration of the skull appearance in the rats with cranial defects.

CONCLUSION

Inactivated autologous bone flap group and BAM bone-induced artificial bone material can promote skull healing and restoration of the original skull appearance, and can be used for reconstruction of the local anatomy of the skull surface.

Complications of Hydroxyapatite Use for Transnasal Closure of Cerebrospinal Fluid Leaks

Background

Hydroxyapatite cement (HAC) was first introduced in the 1980s as a new method for bone replacement. However, it has not been recommended for use in areas exposed to air. Despite this, surgeries have been performed using HAC to close nasal/sinus cerebrospinal fluid (CSF) leaks or in the treatment of encephaloceles.

Methods

This study retrospectively documented four patients in whom HAC was used for closure of ethmoid and sphenoid sinus CSF leaks.

Results

This study showed that exposed hydroxyapatite could be extremely problematic resulting in scarring, chronic granulation, infection, and prolonged healing. Oftentimes, revision surgery was necessary to help control the reaction to hydroxyapatite.

Conclusion

Because of the frequent complications occurring with use of hydroxyapatite in the paranasal sinuses, its use should be limited to selected individuals in whom difficulty in achieving closure of the CFS leak could be anticipated and in whom adequate tissue coverage could be provided.

Which One Is Better to Reduce the Infection Rate, Early or Late Cranioplasty?

OBJECTIVE

Decompressive craniectomy is an effective therapy to relieve high intracranial pressure after acute brain damage. However, the optimal timing for cranioplasty after decompression is still controversial. Many authors reported that early cranioplasty may contribute to improve the cerebral blood flow and brain metabolism. However, despite all the advantages, there always remains a concern that early cranioplasty may increase the chance of infection. The purpose of this retrospective study is to investigate whether the early cranioplasty increase the infection rate. We also evaluated the risk factors of infection following cranioplasty.

METHODS

We retrospectively examined the results of 131 patients who underwent cranioplasty in our institution between January 2008 and June 2015. We divided them into early (≤90 days) and late (>90 days after craniectomy) groups. We examined the risk factors of infection after cranioplasty. We analyzed the infection rate between two groups.

RESULTS

There were more male patients (62%) than female (38%). The mean age was 49 years. Infection occurred in 17 patients (13%) after cranioplasty. The infection rate of early cranioplasty was lower than that of late cranioplasty (7% vs. 20%; p=0.02). Early cranioplasty, non-metal allograft materials, re-operation before cranioplasty and younger age were the significant factors in the infection rate after cranioplasty (p<0.05). Especially allograft was a significant risk factor of infection (odds ratio, 12.4; 95% confidence interval, 3.24-47.33; p<0.01). Younger age was also a significant risk factor of infection after cranioplasty by multivariable analysis (odds ratio, 0.96; 95% confidence interval, 0.96-0.99; p=0.02).

CONCLUSION

Early cranioplasty did not increase the infection rate in this study. The use of non-metal allograft materials influenced a more important role in infection in cranioplasty. Actually, timing itself was not a significant risk factor in multivariate analysis. So the early cranioplasty may bring better outcomes in cognitive functions or wound without raising the infection rate.

Hydroxyapatite Cement in Craniofacial Reconstruction

OBJECTIVES: To evaluate the long-term efficacy of hydroxyapatite cement in craniofacial reconstruction, specifically examining the role (if any) of radiation, implant location, and cement type.

STUDY DESIGN: A retrospective chart review was conducted of all patients presenting to the senior surgeon (Y.D.) for craniofacial reconstruction from September 1997 to April 2004.

METHODS: Data were collected including type of cement used, size of defect, complications, need for removal of cement, reason for defect, and pathologic results of examination of removed cements.

RESULTS: One hundred two patients were identified who underwent craniofacial reconstruction with hydroxyapatite cements, 7 of whom required complete implant removal (6 Norian and 1 Mimix), and 4 (2 Norian and 2 Bone source) of whom required partial implant removal for foreign body reaction. Five of the removals were in patients who underwent postoperative radiation.

CONCLUSIONS: Hydroxyapatite cements are safe in craniofacial reconstruction. The highest risk of implant infection comes from reconstruction in the area of the frontal sinus, immediately beneath coronal incisions, and in patients who receive postoperative radiation treatment. Based on our results, there does appear to be a statistically significant difference in rates of infection and foreign body reaction between the different types of hydroxyapatite cement. We would not recommend implantation of this material in contact with the frontal sinus. Caution should be exercised when it is placed directly beneath an incision or in patients receiving postoperative radiation, particularly if a boost dose is given.

EBM RATING: C

Exposure of Titanium Mesh after Cranioplasty for Microvascular Decompression Surgery: Two Case Reports

Two cases of exposed titanium mesh occurred after implantation for cranioplasty after repeated procedures for microvascular decompression (MVD). Case 1 was a 62-year-old female who underwent MVD for left hemifacial spasm followed by repair of cerebrospinal fluid leak after the surgery, and Case 2 was a 75-year-old female who underwent MVD twice for right trigeminal neuralgia. Both patients visited our hospital again with complaints of postauricular lesion. Titanium mesh was visible through the operative scar and was successfully removed with no complication in both cases. Both patients were underweight females, and combined with multistep surgery may have contributed to the pathology. The present cases suggest that use of titanium mesh should be avoided for cranioplasty of posterior fossa surgery, especially for repeated procedures.

Rapid prototyping-assisted maxillofacial reconstruction

Rapid prototyping (RP) technologies have found many uses in dentistry, and especially oral and maxillofacial surgery, due to its ability to promote product development while at the same time reducing cost and depositing a part of any degree of complexity theoretically. This paper provides an overview of RP technologies for maxillofacial reconstruction covering both fundamentals and applications of the technologies. Key fundamentals of RP technologies involving the history, characteristics, and principles are reviewed. A number of RP applications to the main fields of oral and maxillofacial surgery, including restoration of maxillofacial deformities and defects, reduction of functional bone tissues, correction of dento-maxillofacial deformities, and fabrication of maxillofacial prostheses, are discussed. The most remarkable challenges for development of RP-assisted maxillofacial surgery and promising solutions are also elaborated.

History of synthetic materials in alloplastic cranioplasty

When faced with calvarial defects, surgeons have long searched for repair materials. General criteria include ease of use, low cost, availability, cosmetic shape, and osteointegrative potential. While autologous bone is widely used and favored in contemporary reconstructive procedures, synthetic alternatives have been used throughout history and are necessary in current practice for select cases when autograft reconstruction is not an option (such as cases with severe bony comminution, bone graft resorption, infection, and limited donor site options). For centuries, surgeons have experimented with metals, ceramics, plastics, and later, resorbable polymers. This paper provides a tour of the materials that have been used and experimented with throughout the history of alloplastic cranioplasty.

Osteogenic properties of PBLG-g-HA/PLLA nanocomposites

New development of biomaterial scaffolds remains a prominent issue for the regeneration of lost or fractured bone. Of these scaffolds, a number of bioactive polymers have been synthesized and fabricated for diverse biological roles. Although recent evidence has demonstrated that composite scaffolds such as HA/PLLA have improved properties when compared to either HA or PLLA alone, recent investigations have demonstrated that the phase compatibility between HA and PLLA layers is weak preventing optimal enhancement of the mechanical properties and making the composites prone to breakdown. In the present study, poly (γ-benzyl-L-glutamate) modified hydroxyapatite/(poly (L-lactic acid)) (PBLG-g-HA/PLLA) composite scaffolds were fabricated with improved phase compatibility and tested for their osteogenic properties in 18 Wistar female rats by analyzing new bone formation in 3 mm bilateral femur defects in vivo. At time points, 2, 4 and 8 weeks post surgery, bone formation was evaluated by µ-CT and histological analysis by comparing 4 treatment groups; 1) blank defect, 2) PLLA, 3) HA/PLLA and 4) PBLG-g-HA/PLLA scaffolds. The in vivo analysis demonstrated that new bone formation was much more prominent in HA/PLLA and PBLG-g-HA/PLLA groups as depicted by µ-CT, H&E staining and immunohistochemistry for collagen I. TRAP staining was also utilized to determine the influence of osteoclast cell number and staining intensity to the various scaffolds. No significant differences in either staining intensity or osteoclast numbers between all treatment modalities was observed, however blank defects did contain a higher number of osteoclast-like cells. The results from the present study illustrate the potential of PBLG-g-HA/PLLA scaffolds for bone tissue engineering applications by demonstrating favorable osteogenic properties.

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.

Midterm clinical and tomodensitometric evaluation of cortical bone repair using bone substitute and allogenic membrane protection in the areas of cortical bone harvesting in the parietal cranium in preimplant reconstructive surgery

The authors present their clinical and computed tomographic findings in a series of 13 cases of monocortical bone harvesting, in the setting of preimplant reconstructive surgery, with the harvest sites filled with granular bovine bone substitute, which had an additional coverage using a collagen membrane. These patients were compared with a control group of 6 patients who had not received any cranial bone reconstruction during the initial harvesting. Clinical and computed tomographic evaluations of the repaired parietal cortical bone harvest sites were performed to study the contour of the cortical bone harvest sites in relation to the surrounding soft tissue. Among the 13, there were no clinical cases of infection or allergic reaction. Midterm results of the parietal cortical bone reconstruction using granular bone substitute with overlying protective biodegradable membrane show that this method of reconstruction of the cranium after cranial bone harvesting resulted in significantly improved clinical outcomes.

Porous CaP/silk composite scaffolds to repair femur defects in an osteoporotic model

The most common complication for patients with postmenopausal osteoporosis is bone-related defects and fractures. While routine medication has a high probability of undesirable side effects, new approaches have aimed to develop regeneration procedures that stimulate new bone formation while reversing bone loss. Recently, we have synthesized a new hybrid CaP/silk scaffold with a CaP-phase distribution and pore architecture better suited to facilitate cell differentiation and bone formation. The aim of the present study was to compare the involved remodeling process and therapeutic effect of porous CaP/silk composite scaffolds upon local implantation into osteoporotic defects. Wistar rats were used to induce postmenopausal osteoporotic model by bilateral ovariectomy. The pure silk and hybrid CaP/silk scaffolds were implanted into critical sized defects created in distal femoral epiphysis. After 14 and 28 days, the in vivo osteogenetic efficiency was evaluated by μCT analysis, hematoxylin and eosin staining, Safranin O staining, tartrate-resistant acid phosphatase staining, and immunohistochemical assessment. Animals with or without critical-sized defects were used as drill or blank controls, respectively. The osteoporotic defect model was well established with significantly decreased μCT parameters of BV/TV, Tb.N and increased Tb.Sp, porosity, combined with changes in histological observations. During the healing process, the critical-sized drill control defects failed to regenerate appreciable bone tissue, while more significantly increased bone formation and mineralization with dynamic scaffold degradation and decreased osteoclastic bone resorption could be detected within defects with hybrid CaP/silk scaffolds compared to pure silk scaffolds.

A new custom made bioceramic implant for the repair of large and complex craniofacial bone defects

INTRODUCTION

Neurosurgery and Maxillofacial Surgery Departments of Limoges University Hospital Centre have developed a new concept of a custom made ceramic implant in hydroxyapatite (HA) for the reconstruction of large and complex craniofacial bone defects (more than 25 cm(2)).

MATERIALS AND METHODS

The manufacturing process of the implants used a stereolithography technique that produces implants with three-dimensional shapes derived directly from the scan file of the patient's skull without moulding or machining. Eight patients received 8 implants between 2005 and 2008.

RESULTS

The surgical procedure is simple and fast. The post-operative follow-up was 12 months. No major complications (infection or fracture of the implant) were observed. The cosmetic result was considered satisfactory by both patients and surgeons.

CONCLUSIONS

These new implants are well suited for reconstruction of large craniofacial bone defects (greater than 25 cm(2)) in adults and children over 8 years.

A review of reconstructive materials for use in craniofacial surgery bone fixation materials, bone substitutes, and distractors

Over the last 40 years, craniofacial surgery, in general, and surgery for craniosynostosis, in particular, has witnessed the introduction of a number of new materials for use in operations involving the cranial vault. Some of these materials have proven quite useful over time, while others have failed to meet their stated objectives. In this review, the more popular implant materials are analyzed, and their relative merits and drawbacks are discussed. Craniofacial surgery in the pediatric population has its own unique limitations, quite different from the adult population and those issues are reviewed as well.

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.

Reconstruction of Skull Base and Fronto-orbital Defects following Tumor Resection

Reconstruction of the anterior skull base and fronto-orbital framework following extensive tumor resection is both challenging and controversial. Dural defects are covered with multiple sheets of fascia lata that provide sufficient support and avoid herniation. Plating along the skull base is contraindicated. After resection of orbital walls, grafting is necessary if the periosteum or parts of the periorbital tissue had to be removed, to avoid enophthalmus or strabism. Free bone grafts exposed to the sinonasal or pharyngeal cavity are vulnerable to infection or necrosis: therefore, covering the grafts with vascularized tissue, such as the Bichat fat-pad or pedicled temporalis flaps, should reduce these complications. Alloplastic materials are indispensable in cranial defects, whereas microsurgical free tissue transfer is indicated in cases of orbital exenteration and skin defects. The authors review their experience and follow-up of 122 skull base reconstructions following extensive subcranial tumor resection. Most significant complications were pneumocranium in 4.9%, CSF leaks in 3.2%, and partial bone resorption in 8.1%.

Controversies in skull reconstruction

In the early 1980s, it was shown that bone from the skull (membranous bone) maintained its volume to a significantly greater extent than bone from the rib and iliac crest regions (endochondral bone). However, the reason for this enhanced volume maintenance was not clarified for many years. On the basis of this enhanced volume maintenance, cranial bone became the ideal autogenous graft of choice for hard tissue repair. In the ensuing years, the current authors performed a large number of autogenous split skull cranial bone cranioplasties with significant success. However, the lure of an off-the-shelf material that obviates bone harvest remained. From 1995 to 2005, the senior author performed 20 full-thickness skull defect cranioplasty corrections using calcium phosphate cement (Norian Craniofacial Repair System; Synthes, Inc, West Chester, PA; Stryker-Leibinger, Kalamazoo, MI). Of these full-thickness defects, 16 were large (arbitrarily defined as greater than 25 cm2). In this paper, we report our long-term major and minor complication rates using this material. Because of our high, long-term complication rate (38%), we believe this material is contraindicated for large, full-thickness, skull defects (>25 cm2) and we have returned to autogenous cranial bone as the criterion standard for reconstruction in such patients.

A review of the mechanical behavior of CaP and CaP/polymer composites for applications in bone replacement and repair

Repair of load-bearing defects resulting from disease or trauma remains a critical barrier for bone tissue engineering. Calcium phosphate (CaP) scaffolds are among the most extensively studied for this application. However, CaPs are reportedly too weak for use in such defects and, therefore, have been limited to non-load-bearing applications. This paper reviews the compression, flexural and tensile properties of CaPs and CaP/polymer composites for applications in bone replacement and repair. This review reveals interesting trends that have not, to our knowledge, previously been reported. Data are classified as bulk, scaffolds, and composites, then organized in order of decreasing strength. This allows for general comparisons of magnitudes of strength both within and across classifications. Bulk and scaffold strength and porosity overlap significantly and scaffold data are comparable to bone both in strength and porosity. Further, for compression, all composite data fall below those of the bulk and most of the scaffold. Another interesting trend revealed is that strength decreases with increasing β-tricalcium phosphate (β-TCP) content for CaP scaffolds and with increasing CaP content for CaP/polymer composites. The real limitation for CaPs appears not to be strength necessarily, but toughness and reliability, which are rarely characterized. We propose that research should focus on novel ways of toughening CaPs and discuss several potential strategies.

Calcium phosphate cements in skull reconstruction: a meta-analysis

BACKGROUND

This work addresses the controversy regarding the indications and results of calcium phosphate cements in skull reconstruction through a meta-analysis of the published literature.

METHODS

A PubMed search for articles reporting the use of calcium phosphate cements for skull reconstruction was performed. Data collected included age, volume of cement, defect size, material used, length of follow-up, placement in communication with paranasal sinuses or in irradiated fields, and complications.

RESULTS

Nineteen articles met the authors' inclusion criteria. The mean rates of complications were as follows: total complications, 13 percent (range, 0 to 62 percent); major complications, 9 percent (range, 0 to 62 percent); minor complications, 2 percent (range, 0 to 5 percent); infection, 5 percent (range, 0 to 22 percent); reoperation, 14 percent (range, 0 to 62 percent); and secondary surgery for contour correction, 1 percent (range, 0 to 12 percent). There was significant heterogeneity in the estimated rate of total and major complications, infection, and reoperation (p < 0.001), but minor complications and secondary contour correction had less heterogeneity (p = 0.58 and p = 0.78, respectively). Radiotherapy and communication with the paranasal sinuses significantly increased the complication rate (p < 0.05). Duration between surgery and complications averaged 17.5 months (range, 1 to 89 months).

CONCLUSIONS

When mean complication rate and complication range of calcium phosphate cements in our meta-analysis were compared with previous large cranioplasty studies using methylmethacrylate or autogenous bone, calcium phosphate fared no better, and sometimes fared worse, than these other modalities. Calcium phosphate, therefore, should only be used selectively, and prospective long-term studies are needed to further refine its role in skull reconstruction.

Human adipose-derived side population stem cells cultured on demineralized bone matrix for bone tissue engineering

BACKGROUND

Tissue engineering of new bone relies on the combination and application of osteoconductive, osteoinductive, and osteogenic elements. Natural scaffolds, such as demineralized bone matrix (DBM), contain collagenous networks with growth factors such as bone morphogenetic protein-2. Stem cells from readily available sources, including discarded adipose tissue, have the propensity to differentiate into bone. The present study examines a multi-component technique consisting of a novel side population of adipose stem cells cultured on DBM for tissue engineering applications.

METHODS

Adipose-derived side population stem cells were cultured on DBM for up to 14 days. Cell proliferation, alkaline phosphatase activity, extracellular matrix protein production, and calcium-containing mineral deposit formation were assayed. Ectopic bone formation in a rat model was also evaluated.

RESULTS

Side population stem cells attached to and proliferated on DBM while generating markers of new bone formation. When these cell/substrate composites were implanted into an ectopic model, newly formed bone was 30% greater than that of DBM alone.

CONCLUSIONS

Novel populations of adipose-derived stem cells cultured on DBM compose a system that develops new bone matrix in vitro and in vivo. This strategy provides a novel approach using naturally occurring materials for bone repair in tissue engineering applications.

Vascularized mastoid bone flap cranioplasty after translabyrinthine vestibular schwannoma surgery

OBJECTIVE

We describe a novel technique of cranioplasty using a vascularized mastoid bone flap in patients after translabyrinthine excision of vestibular schwannomas (VS). Postoperative outcomes in terms of pinna and postauricular deformity are evaluated.

STUDY DESIGN

Retrospective study.

SETTING

Tertiary referral center.

RESULTS

Seventeen patients underwent cranioplasty with bone flap after translabyrinthine VS excision. At minimum follow-up of 12 months, none had a cerebrospinal fluid (CSF) leak. The measured pinna projections between the operated and non-operated sides had a mean difference of 0.80 mm (+/-1.70), which is not statistically significant (p > 0.05). The mean depth of the postauricular depressions was 1.38 mm (+/-0.93). Over the same period, 10 patients underwent translabyrinthine VS surgery without cranioplasty. In this group, there was a significant difference of 4.71 mm (+/-1.53) in mean pinna underprojections on the operated sides compared with the non-operated sides. Compared with patients who have undergone cranioplasty, the retroauricular depressions were significantly deeper (p < 0.05) with a mean depth of 2.92 mm (+/-1.21).

CONCLUSIONS

Vascularized mastoid cortical bone flap cranioplasty is a simple and effective technique to ameliorate the pinna and retroauricular deformities after translabyrinthine VS excision without increased surgical cost or the use of alloplastic materials.

Craniofacial reconstruction with bone and biomaterials: review over the last 11 years

This review aims to compare bone grafts and different biomaterials for reconstruction of craniofacial bones in congenital defects, after trauma, and after tumour surgery. A Pubmed search was performed and publications over the last 11 years describing reconstructions of craniofacial bones in non-load-bearing areas were reviewed. Only human studies using bone grafts and biomaterials were included. Studies on skull base reconstruction, distraction osteogenesis, free and pedicled bone flaps and bone-anchored epithesis were excluded. Out of 83 studies, three were prospective, 65 retrospective and 15 studies were case reports. There were seven comparative studies found and some efforts on statistical analysis were made. Except for a few studies, the statistical significant differences in outcomes were found to be related to size and location of bone defects rather than reconstruction method and biomaterial used. An increasing number of alloplastic materials have been available as alternatives to the gold standard autologous bone transplantation for craniofacial bone repair. Comparative studies with statistical analyses on differences in success rates between different biomaterials or bone grafts for specific indications are needed.

Long-term results following titanium cranioplasty of large skull defects

Object

Decompressive craniectomy is an established procedure to lower intracranial pressure. Therefore, cranioplasty remains a necessity in neurosurgery as well. If the patient's own bone flap is not available, the surgeon can choose between various alloplast grafts. A review of the literature proves that 4–13.8% of polymethylmethacrylate plates and 2.6–10% of hydroxyapatite-based implants require replacement. In this retrospective study of large skull defects, the authors compared computer-assisted design/computer-assisted modeled (CAD/CAM) titanium implants for cranioplasty with other frequently used materials described in literature.

Methods

Twenty-six patients underwent cranioplasty with CAD/CAM titanium implants (mean diameter 112 mm). With the aid of visual analog scales, the patients' pain and cosmesis were evaluated 6–12 years (mean 8.1 years) after insertion of the implants.

Results

None of the implants had to be removed. Of all patients, 68% declared their outcomes as excellent, 24% as good, 0.8% as fair, and 0% as poor. There was no resulting pain in 84% of the patients, and 88% were satisfied with the cosmetic result, noting > 75 mm on the visual analog scale of cosmesis. All patients would have chosen cranioplasty again, stating an improvement in their quality of life by the calvarial reconstruction. Nevertheless, follow-up images obtained in 4 patients undergoing removal of meningiomas was only suboptimal.

Conclusions

With the aid of CAD technology, all currently used alloplastic materials are suited even for large skull defect cranioplasty. Analysis of the authors' data and the literature shows that cranioplasty with CAD/CAM titanium implants provides the lowest rate of complications, reasonable costs, and acceptable postoperative imaging. Polymethylmethacrylate is suited for primary cranioplasty or for long-term follow-up imaging of tumors. Titanium implants seem to be the material of choice for secondary cranioplasty of large skull defects resulting from decompressive craniectomy after trauma or infarction. Expensive HA-based ceramics show no obvious advantage over titanium or PMMA.

DELAYED EXTRUSION OF HYDROXYAPATITE CEMENT AFTER TRANSPETROSAL RECONSTRUCTION

OBJECTIVE

Use of hydroxyapatite cement has been advocated for closure of transpetrosal defects to decrease the incidence of cerebrospinal fluid leaks. We previously identified delayed extrusion of this cement as a significant complication associated with this closure technique and now update our long-term experience.

METHODS

In our retrospective review, we identified 1231 patients who underwent transpetrosal procedures by our multidisciplinary cranial base team between 1984 and 2005. Of the subgroup of 177 patients who had hydroxyapatite cement used during the closure of the procedure, 13 patients (7.3%) experienced delayed extrusion of hydroxyapatite cement.

RESULTS

Extrusion occurred in 3 patients within 12 months and in 10 patients within 68 to 140 months. Twelve patients presented with draining fistulae and concomitant Staphylococcus aureus infection; 1 patient presented asymptomatically with a large temporal lobe abscess identified on surveillance magnetic resonance imaging. All 13 patients underwent reoperation, including 1 who underwent a second procedure.

CONCLUSION

Delayed extrusion of hydroxyapatite cement resulted in significant morbidity to our patients and often presented in an indolent manner. We recommend serial examination and imaging studies in patients who have had transpetrosal closures with hydroxyapatite cement. Because of the complication rates associated with hydroxyapatite cement, we have discontinued its use.