Symptoms of sleep disordered breathing in children with craniofacial malformations

STUDY OBJECTIVE

The purpose of this study was to investigate the frequency of sleep disordered breathing (SDB) symptoms in a clinical sample of children with congenital craniofacial malformations (CFM) followed at a tertiary medical center and non-selected for sleep problems.

METHODS

Cross-sectional study of 575 children aged 2-18 years followed at the Craniofacial Anomalies Program between March 2007 and May 2011. The Sleep-Related Breathing Disturbance scale of the Pediatric Sleep Questionnaire was used to screen for SDB, snoring, and sleepiness. A cutoff value ≥ 0.33 of the total answered questions identified children with positive screening for SDB symptoms.

RESULTS

Overall, 25% of children screened positive for SDB, 28% for snoring, and 20% for sleepiness. In children with non-syndromic CFM, those with Robin sequence had the highest frequency of SDB, snoring, and sleepiness (43%, 44%, and 38%, respectively). In children with syndromic CFM, velocardiofacial/ DiGeorge syndrome had the highest frequency of SDB and sleepiness (48% and 43%, respectively). Children with Treacher Collins had the highest frequency of snoring (83%). The presence of cleft palate was not associated with an increased frequency of SDB symptoms. Nevertheless, children with syndromic CFM, compared to those with non-syndromic CFM, had a higher SDB score (0.27 ± 0.21 vs.0.21 ± 0.19, p = 0.003) and were more likely to have sleepiness (26% vs. 18%, p = 0.05).

CONCLUSIONS

Congenital craniofacial malformations in children are associated with high risk for SDB symptoms. Our findings should encourage a high index of suspicion for SDB in children with CFM, with a low threshold for further testing and close follow-up.

CITATION

Moraleda-Cibrián M; Edwards SP; Kasten SJ; Berger M; Buchman SR; O'Brien LM. Symptoms of sleep disordered breathing in children with craniofacial malformations.

Deferoxamine administration delivers translational optimization of distraction osteogenesis in the irradiated mandible

BACKGROUND

The authors' laboratory has previously demonstrated that deferoxamine promotes angiogenesis and bone repair in the setting of radiation therapy coupled with distraction osteogenesis. However, clinically relevant effects of deferoxamine administration on union rate and micro-computed tomographic and biomechanical parameters are unknown. The authors posit that administration of deferoxamine will increase union rate, mineralization, and strength of the regenerate in an irradiated distraction osteogenesis model.

METHODS

Sprague-Dawley rats were randomized into three groups: distraction osteogenesis-control, distraction osteogenesis-radiation therapy, and distraction osteogenesis-radiation therapy-deferoxamine. All animals underwent an osteotomy and distraction osteogenesis across a 5.1-mm distraction gap. Irradiated animals received 35-Gy human-equivalent radiation therapy 2 weeks before surgery, and deferoxamine was injected postoperatively in the regenerate site of treatment animals. Animals were killed on postoperative day 40, and mandibles were harvested to determine rates of bony union and micro-computed tomographic and biomechanical parameters.

RESULTS

Compared with irradiated mandibles, deferoxamine-treated mandibles exhibited a higher union rate (11 percent versus 92 percent, respectively). Across micro-computed tomographic and biomechanical parameters, significant diminutions were observed with administration of radiation therapy, whereas deferoxamine therapy resulted in significant restoration to levels of controls, with select metrics exhibiting significant increases even beyond controls.

CONCLUSIONS

The authors' data confirm that deferoxamine restores clinically relevant metrics of bony union and micro-computed tomographic and biomechanical parameters in a model of irradiated distraction osteogenesis in the murine mandible. Their findings support a potential use for deferoxamine in treatment protocols to allow predictable and reliable use of distraction osteogenesis as a viable reconstructive option in patients with head and neck cancer.

Validation of Histologic Bone Analysis Following Microfil Vessel Perfusion

The ability to examine bone vascularity using Micro-Computed Tomography (μCT) following vessel perfusion with Microfil^® and to subsequently perform histologic bone analysis in the same specimen would provide an efficient method by which the vascular and cellular environment of bone can be examined simultaneously. The purpose of this report is to determine if the administration of Microfil^® precludes accurate histologic assessment of bone quality via osteocyte count and empty lacunae count. Sprague-Dawley rats (n=6) underwent perfusion with Microfil^®. Left hemi-mandibles were harvested, decalcified and underwent vascular analysis via μCT prior to sectioning and staining with Gomori's Trichrome. Quantitative Histomorphometric evaluation was performed. Ninety-five percent confidence intervals were used to determine statistical differences from an established set of controls (n=12). Histologic analyses were successfully performed on specimens that had undergone previous perfusion. Quantitative measures of bone cellularity of perfused versus control specimens revealed no statistical difference in osteocyte count per high-power field (95.33 versus 94.66; 95 percent CI,-7.64 to 6.30) or empty lacunae per high-power field (2.73 versus 1.89, 95 percent CI, -1.81 to 0.13). Here we report a statistical validation allowing for histological analysis of cell counts in specimens in which Microfil^® perfusion has previously been performed.

The effect of Amifostine prophylaxis on bone densitometry, biomechanical strength and union in mandibular pathologic fracture repair

BACKGROUND

Pathologic fractures (Fx) of the mandibles are severely debilitating consequences of radiation (XRT) in the treatment of craniofacial malignancy. We have previously demonstrated Amifostine's effect (AMF) in the remediation of radiation-induced cellular damage. We posit that AMF prophylaxis will preserve bone strength and drastically reverse radiotherapy-induced non-union in a murine mandibular model of pathologic fracture repair.

MATERIALS AND METHODS

Twenty-nine rats were randomized into 3 groups: Fx, XRT/Fx, and AMF/XRT/Fx. A fractionated human equivalent dose of radiation was delivered to the left hemimandibles of XRT/Fx and AMF/XRT/Fx. AMF/XRT/Fx was pre-treated with AMF. All groups underwent left mandibular osteotomy with external fixation and setting of a 2.1mm fracture gap post-operatively. Utilizing micro-computed tomography and biomechanical testing, the healed fracture was evaluated for strength.

RESULTS

All radiomorphometrics and biomechanical properties were significantly diminished in XRT/Fx compared to both Fx and AMF/XRT/Fx. No difference was demonstrated between Fx and AMF/XRT/Fx in both outcomes.

CONCLUSION

Our investigation establishes the significant and substantial capability of AMF prophylaxis to preserve and enhance bone union, quality and strength in the setting of human equivalent radiotherapy. Such novel discoveries establish the true potential to utilize pharmacotherapy to prevent and improve the treatment outcomes of radiation-induced late pathologic fractures.

Parathyroid hormone reverses radiation induced hypovascularity in a murine model of distraction osteogenesis

BACKGROUND

Radiation treatment results in a severe diminution of osseous vascularity. Intermittent parathyroid hormone (PTH) has been shown to have an anabolic effect on osteogenesis, though its impact on angiogenesis remains unknown. In this murine model of distraction osteogenesis, we hypothesize that radiation treatment will result in a diminution of vascularity in the distracted regenerate and that delivery of intermittent systemic PTH will promote angiogenesis and reverse radiation induced hypovascularity.

MATERIALS AND METHODS

Nineteen Lewis rats were divided into three groups. All groups underwent distraction of the left mandible. Two groups received radiation treatment to the left mandible prior to distraction, and one of these groups was treated with intermittent subcutaneous PTH (60 μg/kg, once daily) beginning on the first day of distraction for a total duration of 21 days. One group underwent mandibular distraction alone, without radiation. After consolidation, the rats were perfused and imaged with micro-CT angiography and quantitative vascular analysis was performed.

RESULTS

Radiation treatment resulted in a severe diminution of osseous vascularity in the distracted regenerate. In irradiated mandibles undergoing distraction osteogenesis, treatment with intermittent PTH resulted in significant increases in vessel volume fraction, vessel thickness, vessel number, degree of anisotropy, and a significant decrease in vessel separation (p < 0.05). No significant difference in quantitative vascularity existed between the group that was irradiated, distracted and treated with PTH and the group that underwent distraction osteogenesis without radiation treatment.

CONCLUSIONS

We quantitatively demonstrate that radiation treatment results in a significant depletion of osseous vascularity, and that intermittent administration of PTH reverses radiation induced hypovascularity in the murine mandible undergoing distraction osteogenesis. While the precise mechanism of PTH-induced angiogenesis remains to be elucidated, this report adds a key component to the pleotropic effect of intermittent PTH on bone formation and further supports the potential use of PTH to enhance osseous regeneration in the irradiated mandible.

Temporalis muscle morphomics: the psoas of the craniofacial skeleton

BACKGROUND

The psoas muscle has been shown to predict patient outcomes based on the quantification of muscle area using computed tomography (CT) scans. The accuracy of morphomic analysis on other muscles has not been clearly delineated. In this study, we determine the correlation between temporalis muscle mass, psoas muscle area, age, body mass index (BMI), and gender.

METHODS

Temporalis and psoas muscle dimensions were determined on all trauma patients who had both abdominal and maxillofacial CT scans at the University of Michigan between 2004 and 2011. Age, BMI, and gender were obtained through chart review. Univariate and multivariate analyses were performed to determine the relative relationship between morphomic data of the temporalis and psoas muscles and the ability of such information to correspond with clinical variables, such as BMI, age, and gender.

RESULTS

A total of 646 patients were included in the present study. Among the 249 (38.5%) women and 397 (61.5%) men, the average age was 49.2 y. Average BMI was 27.9 kg/m². Total psoas muscle area directly correlated with mean temporalis muscle thickness (r = 0.57, P < 0.001). There was an indirect correlation between age and psoas muscle area (r = -0.52, P < 0.001) and temporalis muscle thickness (r = -0.36, P < 0.001). Neither psoas nor temporalis measurements correlated strongly with BMI (r = 0.18, P < 0.001; r = 0.14, P = 0.002), although stronger correlations were found in a more "frail," subgroup as defined by a BMI of <20 (r = 0.59, P = 0.002).

CONCLUSIONS

We demonstrate that dimensions of the temporalis muscle can be quantified and may serve as a proxy for age. Going forward, we aim to assess the utility of temporalis and psoas morphomics in predicting complication rates among trauma patients admitted to the hospital to predict outcomes in the future.

Reconciling the effects of inflammatory cytokines on mesenchymal cell osteogenic differentiation

Therapies using mesenchymal stem cells are a popular current avenue for development and utilization, especially in the fields of de novo tissue engineering (Sanchez-Ramos J, Song S, Cardozo-Pelaez F, et al. Adult bone marrow stromal cells differentiate into neural cells in vitro. Exp Neurol 2000;164:247.) or tissue regeneration after physical injury (Kitoh H, Kitakoji T, Tsuchiya H, et al. Transplantation of marrow-derived mesenchymal stem cells and platelet-rich plasma during distraction osteogenesis-a preliminary result of three cases. Bone 2004;35:892; Shumakov VI, Onishchenko NA, Rasulov MF, Krasheninnikov ME, Zaidenov VA. Mesenchymal bone marrow stem cells more effectively stimulate regeneration of deep burn wounds than embryonic fibroblasts. Bull Exp Biol Med 2003;136:192; Bruder SP, Fink DJ, Caplan AI. Mesenchymal stem cells in bone development, bone repair, and skeletal regeneration therapy. J Cell Biochem 1994;56:283.). The osteogenic potential of these cells is of particular interest, given their recent usage for the closure of critical-sized bone defects and other nonhealing bone scenarios such as a nonunion. Recent literature suggests that inflammatory cytokines can significantly impact the osteogenic potential of these cells. A review of relevant, recent literature is presented regarding the impact of the inflammatory cascade on the osteogenic differentiation of these cells and how this varies across species. Finally, we identify areas of conflicting or absent evidence regarding the behavior of mesenchymal stem cells in response to inflammatory cytokines.

Deferoxamine expedites consolidation during mandibular distraction osteogenesis

BACKGROUND

A limitation of mandibular distraction osteogenesis (DO) is the length of time required for consolidation. This drawback subjects patients to possible pin-site infections, as well as a prolonged return to activities of normal daily living. Developing innovative techniques to abridge consolidation periods could be immensely effective in preventing these problematic morbidities. Deferoxamine (DFO) is an angiogenic activator that triggers the HIF-1α pathway through localized iron depletion. We previously established the effectiveness of DFO in enhancing regenerate vascularity at a full consolidation period (28 days) in a murine mandibular DO model. To investigate whether this augmentation in vascularity would function to accelerate consolidation, we progressively shortened consolidation periods prior to μCT imaging and biomechanical testing (BMT).

MATERIALS AND METHODS

Three time points (14d, 21d and 28d) were selected and six groups of Sprague-Dawley rats (n = 60) were equally divided into control (C) and experimental (E) groups for each time period. Each group underwent external fixator placement, mandibular osteotomy, and a 5.1 mm distraction. During distraction, the experimental groups were treated with DFO injections into the regenerate gap. After consolidation, mandibles were imaged and tension tested to failure. ANOVA was conducted between groups, and p < 0.05 was considered statistically significant.

RESULTS

At 14 days of consolidation the experimental group demonstrated significant increases in bone volume fraction (BVF), bone mineral density (BMD) and ultimate load (UL) in comparison to non-treated controls. The benefit of treatment was further substantiated by a striking 100% increase in the number of bony unions at this early time-period (C:4/10 vs. E:8/10). Furthermore, metrics of BVF, BMD, Yield and UL at 14 days with treatment demonstrated comparable metrics to those of the fully consolidated 28d control group.

CONCLUSION

Based on these findings, we contend that augmentation of vascular density through localized DFO injection delivers an efficient means for accelerating bone regeneration without significantly impacting bone quality or strength.

Distraction osteogenesis following low-dose hyperfractionated irradiation in the rat mandible

PURPOSE

The investigators hypothesized that low-dose hyperfractionated radiation would impair mandibular distraction osteogenesis (DO) in a murine mandibular model.

MATERIALS AND METHODS

Male Sprague-Dawley rats underwent fractionated radiation (30 Gy) of the left mandible. After a 2-week recovery period, an external frame distractor was applied and gradual distraction of the mandible was performed. Tissue was harvested after a 28-day consolidation period. Gross, radiologic, and histologic evaluations were undertaken. Control animals underwent surgery for an identical time frame without preoperative radiation.

RESULTS

Animals subjected to preoperative radiation (n = 10) showed suboptimal bone formation, including bone atrophy, incomplete bridging of the distraction gap, and gross bony defects or nonunion, compared with controls (n = 10). Although physical lengthening was achieved, irradiation consistently led to a detrimental effect on the normal process of DO.

CONCLUSION

This set of experiments establishes a valuable rodent model to evaluate the effects of radiation on DO and may help to formulate strategies to optimize DO before it is widely applied in oncologic reconstruction.

Stem cell therapy remediates reconstruction of the craniofacial skeleton after radiation therapy

This study utilized transplanted bone marrow stromal cells (BMSCs) as a cellular replacement therapy to remedy radiation-induced injury and restore impaired new bone formation during distraction osteogenesis (DO). BMSC therapy brought about the successful generation of new bone and significantly improved both the rate and quality of a bony union of irradiated, distracted [X-ray radiation therapy (XRT)/DO] murine mandibles to the level of nonirradiated DO animals. The bone mineral density and bone volume fraction were also significantly improved by the BMSC replacement therapy showing no difference when compared to nonirradiated animals. Finally, a biomechanical analysis examining the yield, failure load, and ultimate load also demonstrated a significantly improved structural integrity in BMSC-treated XRT/DO mandibles over XRT/DO alone. These results indicate that administration of BMSCs intraoperatively to a radiated distraction gap can function as an adequate stimulant to rescue the ability for irradiated bone to undergo DO and produce a healed regenerate of a vastly superior quality and strength. We believe that the fundamental information on the optimization of bone regeneration in the irradiated mandible provided by this work has immense potential to be translated from the bench to the bedside to lead to improved therapeutic options for patients suffering from the disastrous sequelae of radiation therapy.

Early detection of burn induced heterotopic ossification using transcutaneous Raman spectroscopy

INTRODUCTION

Heterotopic ossification (HO), or the abnormal formation of bone in soft tissue, occurs in over 60% of major burn injuries and blast traumas. A significant need exists to improve the current diagnostic modalities for HO which are inadequate to diagnose and intervene on HO at early time-points. Raman spectroscopy has been used in previous studies to report on changes in bone composition during bone development but has not yet been applied to burn induced HO. In this study, we validate transcutaneous, in-vivo Raman spectroscopy as a methodology for early diagnosis of HO in mice following a burn injury.

METHODS

An Achilles tenotomy model was used to study HO formation. Following tenotomy, mice were divided into burn and sham groups with exposure of 30% surface area on the dorsum to 60° water or 30° water for 18s respectively. In-vivo, transcutaneous Raman spectroscopy was performed at early time points (5 days, 2 and 3 weeks) and a late time point (3 months) on both the tenotomized and non-injured leg. These same samples were then dissected down to the bone and ex-vivo Raman measurements were performed on the excised tissue. Bone formation was verified with Micro CT and histology at corresponding time-points.

RESULTS

Our Raman probe allowed non-invasive, transcutaneous evaluation of heterotopic bone formation. Raman data showed significantly increased bone mineral signaling in the tenotomy compared to control leg at 5 days post injury, with the difference increasing over time whereas Micro CT did not demonstrate heterotopic bone until three weeks. Ex-vivo Raman measurements showed significant differences in the amount of HO in the burn compared to sham groups and also showed differences in the spectra of new, ectopic bone compared to pre-existing cortical bone.

CONCLUSIONS

Burn injury increases the likelihood of developing HO when combined with traumatic injury. In our in-vivo mouse model, Raman spectroscopy allowed for detection of HO formation as early as 5 days post injury. Changes in bone mineral and matrix composition of the new bone were also evidenced in the Raman spectra which could facilitate early identification of HO and allow more timely therapy decisions for HO patients.

Raman spectroscopy demonstrates Amifostine induced preservation of bone mineralization patterns in the irradiated murine mandible

PURPOSE

Adjuvant radiotherapy in the management of head and neck cancer remains severely debilitating. Fortunately, newly developed agents aimed at decreasing radiation-induced damage have shown great promise. Amifostine (AMF) is a compound, which confers radio-protection to the exposed normal tissues, such as bone. Our intent is to utilize Raman spectroscopy to demonstrate how AMF preserves the mineral composition of the murine mandible following human equivalent radiation.

METHODS

Sprague Dawley rats were randomized into 3 experimental groups: control (n=5), XRT (n=5), and AMF-XRT (n=5). Both XRT and AMF groups underwent bioequivalent radiation of 70Gy in 5 fractions to the left hemimandible. AMF-XRT received Amifostine prior to radiation. Fifty-six days post-radiation, the hemimandibles were harvested, and Raman spectra were taken in the region of interest spanning 2mm behind the last molar. Bone mineral and matrix-specific Raman bands were analyzed using one-way ANOVA, with statistical significance at p<0.05.

RESULTS

The full-width at half-maximum of the primary phosphate band (FWHM) and the ratio of carbonate/phosphate intensities demonstrated significant differences between AMF-XRT versus XRT (p<0.01) and XRT versus control (p<0.01). There was no difference between AMF-XRT and control (p>0.05) in both Raman metrics. Computer-aided spectral subtraction further confirmed these results where AMF-XRT was spectrally similar to the control. Interestingly, the collagen cross-link ratio did not differ between XRT and AMF-XRT (p<0.01) but was significantly different from the control (p<0.01).

CONCLUSION

Our novel findings demonstrate that AMF prophylaxis maintains and protects bone mineral quality in the setting of radiation. Raman spectroscopy is an emerging and exceptionally attractive clinical translational technology to investigate and monitor both the destructive effects of radiation and the therapeutic remediation of AMF on the structural, physical and chemical qualities of bone.

Role of parathyroid hormone therapy in reversing radiation-induced nonunion and normalization of radiomorphometrics in a murine mandibular model of distraction osteogenesis

BACKGROUND

The use of mandibular distraction osteogenesis (MDO) for tissue replacement after oncologic resection or for defects caused by osteoradionecrosis has been described but, in fact, has seen limited clinical utility. Previous laboratory work has shown that radiation (XRT) causes decreased union formation, decreased cellularity, and decreased mineral density in an animal model of MDO. Our global hypothesis is that radiation-induced bone damage is partly driven by the pathologic depletion of both the number and function of osteogenic cells. Parathyroid hormone (PTH) is a U.S. Food and Drug Administration-approved anabolic hormonal therapy that has demonstrated efficacy for increasing bone mineral density for the treatment of osteoporosis. We postulate that intermittent systemic administration of PTH will serve as an anabolic stimulant to cellular function that will act to reverse radiation-induced damage and enhance bone regeneration in a murine mandibular model of DO.

METHODS

A total of 20 isogenic male Lewis rats were randomly assigned into 3 groups. Group 1 (XRT-DO, n = 7) and group 2 (XRT-DO-PTH, n = 5) received a human bioequivalent dose of 70 Gy fractionated over 5 days. All groups including group 3 (DO, n = 8) underwent a left unilateral mandibular osteotomy with bilateral external fixator placement. Four days later, mandibular DO was performed at a rate of 0.3 mm every 12 hours to reach a maximum gap of 5.1 mm. Group 2 was injected PTH (60 μg/kg) subcutaneously daily for 3 weeks following the start of MDO. On postoperative day 41, all left hemimandibles were harvested. Micro-CT at 45-μm voxel size was performed and radiomorphometrics parameters of bone mineralization were generated. Union quality was evaluated on a 4-point qualitative grading scale. Radiomorphometric data were analyzed using 1-way ANOVA, and union quality assessment was analyzed via the Mann-Whitney test. Statistical significance was considered at p ≤ .05.

RESULTS

Groups 1 and 2 appropriately demonstrated clinical signs of radiation-induced stress ranging from alopecia to mucositis. Union quality was significantly higher in PTH-treated XRT-DO animals, compared with XRT-DO group animals (p = .02). Mineralization metrics, including bone volume fraction (BVF) and bone mineral density (BMD), also showed statistically significant improvement. The groups that were treated with PTH showed no statistical differences in union or radiomorphometrics when compared with DO in nonradiated animals.

CONCLUSION

We have successfully demonstrated the therapeutic efficacy of PTH to stimulate and enhance bone regeneration in our irradiated murine mandibular model of DO. Our investigation effectively resulted in statistically significant increases in BMD, BVF, and clinical unions in PTH-treated mandibles. PTH demonstrates immense potential to treat clinical pathologies where remediation of bone regeneration is essential.

Localized deferoxamine injection augments vascularity and improves bony union in pathologic fracture healing after radiotherapy

BACKGROUND

Medically based efforts and alternative treatment strategies to prevent or remediate the corrosive effects of radiotherapy on pathologic fracture healing have failed to produce clear and convincing evidence of success. Establishing an effective pharmacologic option to prevent or treat the development of non-unions in this setting could have immense therapeutic potential. Experimental studies have shown that deferoxamine (DFO), an iron-chelating agent, bolsters vascularity and subsequently enhances normal fracture healing when injected locally into a fracture callus in long bone animal models. Since radiotherapy is known to impede angiogenesis, we hypothesized that the pharmacologic addition of DFO would serve to mitigate the effects of radiotherapy on new vessel formation in vitro and in vivo.

MATERIALS AND METHODS

In vitro investigation of angiogenesis was conducted utilizing HUVEC cells in Matrigel. Endothelial tubule formation assays were divided into four groups: Control, Radiated, Radiated+Low-Dose DFO and Radiated+High-Dose DFO. Tubule formation was quantified microscopically and video recorded for the four groups simultaneously during the experiment. In vivo, three groups of Sprague-Dawley rats underwent external fixator placement and fracture osteotomy of the left mandible. Two groups received pre-operative fractionated radiotherapy, and one of these groups was treated with DFO after fracture repair. After 40 days, the animals were perfused and imaged with micro-CT to calculate vascular radiomorphometrics.

RESULTS

In vitro, endothelial tubule formation assays demonstrated that DFO mitigated the deleterious effects of radiation on angiogenesis. Further, high-dose DFO cultures appeared to organize within 2h of incubation and achieved a robust network that was visibly superior to all other experimental groups in an accelerated fashion. In vivo, animals subjected to a human equivalent dose of radiotherapy (HEDR) and left mandibular fracture demonstrated quantifiably diminished μCT metrics of vascular density, as well as a 75% incidence of associated non-unions. The addition of DFO in this setting markedly improved vascularity as demonstrated with 3D angiographic modeling. In addition, we observed an increased incidence of bony unions in the DFO treated group when compared to radiated fractures without treatment (67% vs. 25% respectively).

CONCLUSION

Our data suggest that selectively targeting angiogenesis with localized DFO injections is sufficient to remediate the associated severe vascular diminution resulting from a HEDR. Perhaps the most consequential and clinically relevant finding was the ability to reduce the incidence of non-unions in a model where fracture healing was not routinely observed.

Radiomorphometric quantitative analysis of vasculature utilizing micro-computed tomography and vessel perfusion in the murine mandible

Purpose Biomechanical, densitometric, and histological analyses have been the mainstay for reproducible outcome measures for investigation of new bone formation and osseous healing. Here we report the addition of radiomorphometric vascular analysis as a quantitative measure of vascularity in the murine mandible. To our knowledge this is the first description of using micro-computed tomography (micro-CT) to evaluate the temporal and spatial pattern of angiogenesis in the craniofacial skeleton. Methods The vessel perfusion technique was performed on 10 Sprague-Dawley rats using Microfil (MV-122, Flow Tech; Carver, MA). After decalcification, hemimandibles were imaged using high-resolution micro-CT. Six separate radiomorphometric vascular metrics were calculated. Results Radiomorphometric values were analyzed using three different thresholds on micro-CT. Experimentally, 1000 Hounsfield units was found to be the optimal threshold for analysis to capture the maximal vascular content of the bone. Data from seven hemimandibles were analyzed. Minimal statistical variance in each of the quantitative measures of vascularity resulted in reproducible metrics for each of the radiomorphometric parameters. Conclusions We have demonstrated that micro-CT vascular imaging provides a robust methodology for evaluation of vascular networks in the craniofacial skeleton. This technique provides 3D quantitative data analysis that differs significantly from laser Doppler and microsphere methods, which simply measure flow. This technique is advantageous over labor-intensive 2D conventional analyses using histology and X-ray microangiography. Our data establish the appropriate thresholding for optimal vascular analyses and provide baseline measurements that can be used to analyze the role of angiogenesis in bone regeneration and repair in the craniofacial skeleton.

The effects of high dose and highly fractionated radiation on distraction osteogenesis in the murine mandible

The ability of irradiated tissue to support bony growth remains poorly defined, although there are anecdotal cases reported showing mixed results for the use of mandibular distraction osteogenesis after radiation for head and neck cancer. Many of these reports lack objective measures that would allow adequate analysis of outcomes or efficacy. The purpose of this experiment was to utilize a rat model of mandibular distraction osteogenesis after high dose and highly fractionated radiation therapy and to evaluate and quantify distracted bone formation under these conditions. Male Sprague–Dawley rats underwent 12 fractions of external beam radiation (48 Gray) of the left mandible. Following a two week recovery period, an external frame distractor was applied and gradual distraction of the mandible was performed. Tissue was harvested after a twenty-eight day consolidation period. Gross, radiologic and histological evaluations were undertaken. Those animals subjected to pre-operative radiation showed severe attenuation of bone formation including bone atrophy, incomplete bridging of the distraction gap, and gross bony defects or non-union. Although physical lengthening was achieved, the irradiated bone consistently demonstrated marked damaging effects on the normal process of distraction osteogenesis. This murine model has provided reliable evidence of the injurious effects of high dose radiation on bone repair and regeneration in distraction osteogenesis utilizing accurate and reproducible metrics. These results can now be used to assist in the development of therapies directed at mitigating the adverse consequences of radiation on the regeneration of bone and to optimize distraction osteogenesis so it can be successfully applied to post-oncologic reconstruction.

Deferoxamine reverses radiation induced hypovascularity during bone regeneration and repair in the murine mandible

BACKGROUND

Deferoxamine (DFO) is an iron-chelating agent that has also been shown to increase angiogenesis. We hypothesize that the angiogenic properties of DFO will improve bone regeneration in distraction osteogenesis (DO) after x-ray radiation therapy (XRT) by restoring the vascularity around the distraction site.

MATERIAL AND METHODS

Three groups of Sprague-Dawley rats underwent distraction of the left mandible. Two groups received pre-operative fractionated XRT, and one of these groups was treated with DFO during distraction. After consolidation, the animals were perfused and imaged with micro-CT to calculate vascular radiomorphometrics.

RESULTS

Radiation inflicted a severe diminution in the vascular metrics of the distracted regenerate and consequently led to poor clinical outcome. The DFO treated group revealed improved DO bone regeneration with a substantial restoration and proliferation of vascularity.

CONCLUSIONS

This set of experiments quantitatively demonstrates the ability of DFO to temper the anti-angiogenic effect of XRT in mandibular DO. These exciting results suggest that DFO may be a viable treatment option aimed at mitigating the damaging effects of XRT on new bone formation.

Chiari malformation associated with craniosynostosis

OBJECT

Chiari malformation (CM) Type I is frequently associated with craniosynostosis. Optimal management of CM in patients with craniosynostosis is not well-established. The goal of this study was to report on a series of pediatric patients with both craniosynostosis and CM and discuss their management.

METHODS

The authors searched the medical records of 383 consecutive patients treated for craniosynostosis at a single institution over a 15-year period to identify those with CM. They recorded demographic data as well as surgical treatment and outcomes for these patients. When MR imaging was performed, cerebellar tonsillar descent was recorded and any other associated findings, such as hydrocephalus or spinal syringes, were noted.

RESULTS

A total of 29 patients with both CM and craniosynostosis were identified. Of these cases, 28% had associated occipital venous abnormalities, 45% were syndromic, and 52% also had hydrocephalus. Chiari malformation was more likely to be present in those patients with isolated lambdoid synostosis (55%), multisuture synostosis (35%), and pansynostosis (80%), compared with patients with coronal synostosis (6%) or sagittal synostosis (3%). All patients underwent surgical repair of craniosynostosis: 16 had craniosynostosis repair as well as CM decompression, and 13 patients did not undergo CM decompression. Of the 7 patients in whom craniosynostosis repair alone was performed, 5 had decreased tonsillar ectopia postoperatively and 5 had improved CSF flow studies postoperatively. Both patients with a spinal syrinx had imaging-documented syrinx regression after craniosynostosis repair. In 12 patients in whom CM was diagnosed after primary craniosynostosis repair, 5 had multiple cranial vault expansions and evidence of elevated intracranial pressure. In 5 cases, de novo CM development was documented following craniosynostosis repair at a mean of 3.5 years after surgery.

CONCLUSIONS

Chiari malformation is frequently seen in patients with both multi- and single-suture lambdoid craniosynostosis. Chiari malformation, and even a spinal cord syrinx, will occasionally resolve following craniofacial repair. De novo development of CM after craniosynostosis repair is not unusual.

Bone regeneration in distraction osteogenesis demonstrates significantly increased vascularity in comparison to fracture repair in the mandible

BACKGROUND

Tissue analysis of bone regenerate has suggested an intense vascular response after mandibular distraction osteogenesis (DO). Quantifying and three-dimensionally imaging this vascular response could be of immense clinical import in efforts to advance the utility of bone regeneration and repair. Conventional quantification of vascular responses has heretofore focused on inexact, cumbersome measurements of blood flow and histologic vessel counting. Using micro-computed tomography after vessel perfusion, we posit that quantitative vascular metrics will be significantly higher in mandibular DO compared with those observed in fracture repair (FxR) after bony union.

METHODS

Sprague-Dawley rats underwent mandibular osteotomy and external fixator placement. A DO group (n=9) underwent a 5.1-mm distraction, whereas a FxR group (n=12) had a 2.1-mm fixed gap set. Forty days after surgery, Microfil was perfused into the vasculature, and imaging ensued. Vascular radiomorphometrics were calculated for the regions of interest. Independent-samples t-test was performed for comparison, with statistical significance set at P≤0.05.

RESULTS

Stereological analysis demonstrated statistically significant increases in the distracted vasculature compared with fracture repair: vessel volume fraction (5.4% versus 2.8%, P=0.030) and vessel number (0.86 versus 0.50 mm, P=0.014).

CONCLUSIONS

We report robust and quantifiable increases in vascular density in DO compared with FxR. Our findings support a significant distinction between the regenerative processes of mandibular DO from the reparative mechanisms controlling fracture healing. A better understanding of the differences between the 2 types of bone formation may enable clinicians to selectively optimize therapeutic outcomes in the future.