Quantitative histomorphometric assessment of regenerate cellularity and bone quality in mandibular distraction osteogenesis after radiation therapy

Effects of ionizing radiation on woven bone: influence on the osteocyte lacunar network, collagen maturation, and microarchitecture

OBJECTIVES

Evaluate the effects of ionizing radiation on microarchitecture, the osteocyte lacunar network, and collagen maturity in a bone repair site.

MATERIALS AND METHODS

Bone defects were created on tibias of 20 New Zealand rabbits. After 2 weeks, the animals were randomly divided into (n = 10) NoIr (nonirradiated group) and Ir (irradiated group). In the Ir, the animals received single-dose irradiation of 30 Gy on the tibia and were euthanized after 2 weeks. Bone microarchitecture parameters were analyzed by using micro-CT, and the osteocyte lacunar network, bone matrix, and collagen maturation by histomorphometric analysis. The data were analyzed using unpaired Student's t test (α = 0.05).

RESULTS

Trabecular thickness in Ir was lower than that in NoIr (P = 0.028). No difference was found for bone volume fraction and bone area. Lacunae filled with osteocytes were more numerous (P < 0.0001) in NoIr (2.6 ± 0.6) than in Ir (1.97 ± 0.53). Empty lacunae were more prevalent (P < 0.003) in Ir (0.14 ± 0.10) than in NoIr (0.1 ± 0.1). The mean osteocyte lacunae size was higher (P < 0.01) in Ir (15.4 ± 4.41) than in NoIr (12.7 ± 3.7). Picrosirius red analysis showed more (P < 0.05) mature collagen in NoIr (29.0 ± 5.3) than in Ir (23.4 ± 4.5). Immature collagen quantification revealed no difference between groups.

CONCLUSIONS

Ionizing radiation compromised bone formation and an impairment in bone repair in irradiated woven bone was observed.

CLINICAL RELEVANCE

Before radiotherapy, patients usually need surgical intervention, which may be better performed, if clinicians understand the repair process in irradiated bone, using novel approaches for treating these individuals.

Comprehensive Treatment of Facial Deformity Due to Radiotherapy in Rhabdomyosarcoma Patients: Distraction Osteogenesis and Free Flaps Surgical Technique

Radiotherapy is essential for achieving and maintaining local control in head and neck rhabdomyosarcoma patients. However, radiotherapy may cause outgrowth disturbances of facial bone and soft tissue, resulting in facial asymmetry.Several studies have shown that the management of irradiated bones still remains challenging. The possibility of obtaining functional and aesthetic results when managing facial deformities due to radiation therapy with distraction osteogenesis combined with free flaps reconstruction is not common and not well documented in recent literature.In this report, we present the long-term results of distraction osteogenesis and soft tissue reconstruction via microvascular free flap to correct the facial hypoplasia of a young patient who underwent radiation therapy for rhabdomyosarcoma.This is the first presentation of 26 years long-term results in a patient who also underwent free flaps reconstruction as ancillary surgery for esthetic good results.

Amifostine Treatment Mitigates the Damaging Effects of Radiation on Distraction Osteogenesis in the Murine Mandible

According to the American Society of Clinical Oncology, in 2012, more than 53,000 new cases of head and neck cancers (HNCs) were reported in the United States alone and nearly 12,000 deaths occurred relating to HNC. Although radiotherapy (XRT) has increased survival, the adverse effects can be unrelenting and their management is rarely remedial. Current treatment dictates surgical mandibular reconstruction using free tissue transfer. These complex operations entail extended hospitalizations and attendant complications often lead to delays in initiation of adjuvant therapy, jeopardizing prognosis as well as quality of life. The creation of new bone by distraction osteogenesis (DO) generates a replacement of deficient tissue from local substrate and could have immense potential therapeutic ramifications. Radiotherapy drastically impairs bone healing, precluding its use as a reconstructive method for HNC. We posit that the deleterious effects of XRT on bone formation could be pharmacologically mitigated. To test this hypothesis, we used a rodent model of DO and treated with amifostine, a radioprotectant, to assuage the XRT-induced injury on new bone formation. Amifostine had a profound salutary effect on bone regeneration, allowing the successful implementation of DO as a reconstructive technique. The optimization of bone regeneration in the irradiated mandible has immense potential for translation from the bench to the bedside, providing improved therapeutic options for patients subjected to XRT.

Bone marrow stem cells assuage radiation-induced damage in a murine model of distraction osteogenesis: A histomorphometric evaluation

The purpose of this study is to determine if intraoperatively placed bone marrow stem cells (BMSCs) will permit successful osteocyte and mature bone regeneration in an isogenic murine model of distraction osteogenesis (DO) following radiation therapy (XRT). Lewis rats were split into three groups, DO only (Control), XRT followed by DO (xDO) and XRT followed by DO with intraoperatively placed BMSCs (xDO-BMSC). Coronal sections from the distraction site were obtained, stained and analyzed via statistical analysis with analysis of variance (ANOVA) and subsequent Tukey or Games-Howell post-hoc tests. Comparison of the xDO-BMSC and xDO groups demonstrated significantly improved osteocyte count (87.15 ± 10.19 vs. 67.88 ± 15.38, P = 0.00), and empty lacunae number (2.18 ± 0.79 vs 12.34 ± 6.61, P = 0.00). Quantitative analysis revealed a significant decrease in immature osteoid volume relative to total volume (P = 0.00) and improved the ratio of mature woven bone to immature osteoid (P = 0.02) in the xDO-BMSC compared with the xDO group. No significant differences were found between the Control and xDO-BMSC groups. In an isogenic murine model of DO, BMSC therapy assuaged XRT-induced cellular depletion, resulting in a significant improvement in histological and histomorphometric outcomes.

Role of parathyroid hormone in regeneration of irradiated bone in a murine model of mandibular distraction osteogenesis

BACKGROUND

The purpose of this study was to measure the histologic and histomorphometric effects of parathyroid hormone (PTH) treatment on irradiated bone undergoing distraction osteogenesis (DO).

METHODS

Thirty-four rats were divided into 3 groups. The control group underwent DO and the radiation control group underwent radiotherapy (RT) before DO. The PTH group underwent RT and received PTH during DO. Quantitative histology and histomorphometry were performed.

RESULTS

RT resulted in a depletion of osteocytes and increase in empty lacunae. Treatment with PTH resulted in an increase in osteocyte counts and decrease in empty lacunae (p < .05), restoring osteocytes to levels seen in nonradiated bone (p = .121). RT decreased bone volume to tissue volume (BV-TV) ratio and increased osteoid volume to tissue volume (OV-TV) ratio, signifying increased immature bone formation. PTH treatment restored OV-TV ratio to that observed in nonradiated bone.

CONCLUSION

PTH treatment of irradiated bone enhanced bone regeneration and restored osteocyte counts and OV-TV ratio to levels comparable to nonradiated bone. © 2016 Wiley Periodicals, Inc. Head Neck 39: 464-470, 2017.

Prophylactic amifostine prevents a pathologic vascular response in a murine model of expander-based breast reconstruction

BACKGROUND

Although expander-based breast reconstruction is the most commonly used method of reconstruction worldwide, it continues to be plagued with complication rates as high as 60% when radiotherapy is implemented. We hypothesized that quantitative measures of radiotherapy-induced vascular injury can be mitigated by utilizing amifostine in a murine model of expander-based breast reconstruction.

METHODS

30 rats were divided into three groups: expander placement (Control), expander placement followed by radiotherapy (XRT), and expander placement followed by radiotherapy with amifostine (AMF/XRT). All groups underwent placement of a sub-latissimus tissue expander. After a 45 day recovery period, all groups underwent vascular perfusion and micro-CT analysis.

RESULTS

Micro-CT analysis was used to calculate vessel volume fraction (VVF), vessel number (VN), and vessel separation (VSp). A significant increase in VN was seen in the XRT group as compared to the Control (p = 0.021) and the AMF/XRT (p = 0.027). There was no difference between Control and AMF/XRT (p = 0.862). VVF was significantly higher in XRT than either Control (p = 0.043) and AMF/XRT (p = 0.040), however no difference was seen between Control and AMF/XRT (p = 0.980). VSp of XRT was smaller when compared to both Control and AMF/XRT specimens (p = 0.05 and p = 0.048, respectively), and no difference was seen between Control and AMF/XRT (p = 0.339).

CONCLUSIONS

Amifostine administered prior to radiotherapy preserved vascular metrics similar to those of non-radiated specimens. Elevated vascularity demonstrated within the XRT group was not seen in either the Control or AMF/XRT groups. These results indicate that amifostine protects soft tissue in our model from a radiotherapy-induced pathologic vascular response.

A Histomorphometric Analysis of Radiation Damage in an Isogenic Murine Model of Distraction Osteogenesis

PURPOSE

The devastation radiation therapy (XRT) causes to endogenous tissue in patients with head and neck cancer can be a prohibitive obstacle in reconstruction of the mandible, demanding a better understanding of XRT-induced damage and options for reconstruction. This study investigated the cellular damage caused by radiation in an isogenic murine model of mandibular distraction osteogenesis (DO). The authors posited that radiation would result in fewer osteocytes, with increased empty lacunae and immature osteoid.

MATERIALS AND METHODS

Twenty Lewis rats were randomly assigned to a DO group (n = 10) or a XRT/DO group (n = 10). These groups underwent an osteotomy and mandibular DO across a 5.1-mm gap. XRT was administered to the XRT/DO group at a fractionated human equivalent dose of 35 Gy before surgery. Animals were sacrificed on postoperative day 40 and mandibles were harvested and sectioned for histologic analysis.

RESULTS

Bone that underwent radiation showed a significantly decreased osteocyte count and complementary increase in empty lacunae compared with non-XRT bone (P = .019 and P = .000). In addition, XRT bone exhibited increased immature osteoid and decreased mature woven bone compared with nonradiated bone (P = .001 and P = .003, respectively). Furthermore, analysis of the ratio of immature osteoid to woven bone volume exhibited a significant increase in the XRT bone, further showing the devastating damage from XRT (P = .001).

CONCLUSION

These results clearly show the cellular diminution that occurs as a result of radiation. This foundational study provides the groundwork on which to investigate cellular therapies in an immuno-privileged model of mandibular DO.

Impact of radiation history, gender and age on bone quality in sites for orthodontic skeletal anchorage device placement

AIMS

Stability of orthodontic miniscrew implants is prerequisite to their success and durability in orthodontic treatment. As investigations revealed a positive correlation of miniscrew stability to periimplant bone quality, it has been the aim of this study to analyze the bone structure of resection preparations of human mandibles histologically by investigating the samples according to age, gender and exposure to radiotherapy.

METHODS

Inflammation- and tumor-free alveolar bone sections from human mandibles (n = 31) with previously diagnosed carcinoma, chronic osteomyelitis or cysts were analyzed histomorphologically and histomorphometrically as to the dimension of trabeculae in cancellous areas. Group A investigated the impact of a history of radiation therapy, group B of gender and group C contrasted biopsies from individuals aging under 60 or over 60 years. Statistics were performed using the Kruskal-Wallis-test.

RESULTS

Radiation, gender and age did not significantly influence bone density. The mean bone density averaged 40.7 ± 15.0% of spongiosa for the total collective with a median age of 58.4 years ± 14.7 years.

CONCLUSIONS

Our findings provide new information on bone quality, thus contributing to a more precise evaluation of the parameters affecting and those not affecting miniscrew implant stability. On the basis of these results, the formulation of clinical guidelines for risk assessment of therapeutic approaches in patients prior to insertion of orthodontic skeletal anchorage devices seems to be conceivable.

New approach for the treatment of osteoradionecrosis with pentoxifylline and tocopherol

Osteoradionecrosis (ORN) of the jaw is a significant complication of radiotherapy for oral cavity cancer. In addition to antibiotic medication, treatment options such as hyperbaric oxygen therapy, surgical approaches, and combined therapy with pentoxifylline and tocopherol have been recently introduced. In this review article, we will discuss the definition and classifications of osteoradionecrosis, its etiology and pathophysiology, previous treatment options, oral and maxillofacial complications of radiotherapy, basic information on pentoxifylline and tocopherol, recent reports of pentoxifylline and tocopherol combined therapy, and, finally, ORN-induced animal models and future approaches.

Vascular analysis as a proxy for mechanostransduction response in an isogenic, irradiated murine model of mandibular distraction osteogenesis

INTRODUCTION

Head and neck cancer is a debilitating and disfiguring disease. Although numerous treatment options exist, an array of debilitating side effects accompany them, causing physiological and social problems. Distraction osteogenesis (DO) can avoid many of the pathologies of current reconstructive strategies; however, due to the deleterious effects of radiation on bone vascularity, DO is generally ineffective. This makes investigating the effects of radiation on neovasculature during DO and creating quantifiable metrics to gauge the success of future therapies vital. The purpose of this study was to develop a novel isogenic rat model of impaired vasculogenesis of the regenerate mandible in order to determine quantifiable metrics of vascular injury and associated damage.

METHODS

Male Lewis rats were divided into two groups: DO only (n=5) AND Radiation Therapy (XRT)+DO (n=7). Afterwards, a distraction device was surgically implanted into the mandible. Finally, they were distracted a total of 5.1mm. Animals were perfused with a radiopaque casting agent concomitant with euthanasia, and subsequently demineralization, microcomputed tomography, and vascular analysis were performed.

RESULTS

Vessel volume fraction, vessel thickness, vessel number, and degree of anisotropy were diminished by radiation. Vessel separation was increased by radiation.

CONCLUSION

The DO group experienced vigorous vessel formation during distraction and neovascularization with a clear, directional progression, while the XRT/DO group saw weak vessel formation during distraction and neovascularization. Further studies are warranted to more deeply examine the impairments in osteogenic mechanotransductive pathways following radiation in the murine mandible. This isogenic model provides quantifiable metrics for future studies requiring a controlled approach to immunogenicity.

Amifostine preserves osteocyte number and osteoid formation in fracture healing following radiotherapy

PURPOSE

Radiation is known to decrease osteocyte count and function, leading to bone weakening. A treatment strategy to mitigate these consequences could have immense therapeutic ramifications. The authors previously reported significantly decreased osteocyte count and mineralization capacity in a rat model of fracture healing after radiotherapy. They hypothesized that amifostine (AMF) would preserve osteocyte number and function in this model.

MATERIALS AND METHODS

Thirty-six rats were divided into 3 groups: fracture, radiated fracture, and radiated fracture with AMF. Radiated groups underwent human-equivalent radiotherapy to the mandible before fixator placement and mandibular osteotomy. The AMF group received a subcutaneous injection before each dose of radiotherapy. After 40 days, mandibles were harvested for histologic processing. Quantification of osteocyte count (Oc), empty lacunae (EL), and osteoid ratio (osteoid volume [OV] to tissue volume [TV]) was performed and the results were compared using analysis of variance (P < .05).

RESULTS

Radiated fractures showed significantly decreased Oc, increased EL, and a decreased capacity to produce new osteoid at the fracture site as measured with OV/TV compared with nonradiated fractures. In mandibles treated with AMF, these metrics were not statistically different than the control, indicating a preservation of osteocyte number and function.

CONCLUSIONS

These results support the hypothesis that AMF preserves osteocyte number and function, thereby preventing the pernicious effects of radiotherapy on the cellular environment of fracture healing. Based on these findings, the authors encourage future investigation of this promising therapy for use in the prevention of pathologic fractures and osteoradionecrosis.

Parathyroid hormone therapy mollifies radiation-induced biomechanical degradation in murine distraction osteogenesis

OBJECTIVE

Descriptions of mandibular distraction osteogenesis for tissue replacement after oncologic resection or for defects caused by osteoradionecrosis have been limited. Previous work demonstrated radiation decreases union formation, cellularity and mineral density in mandibular distraction osteogenesis. The authors posit that intermittent systemic administration of parathyroid hormone will serve as a stimulant to cellular function, reversing radiation-induced damage and enhancing bone regeneration.

METHODS

Twenty male Lewis rats were randomly assigned to three groups: group 1 (radiation and distraction osteogenesis, n = 7) and group 2 (radiation, distraction osteogenesis, and parathyroid hormone, n = 5) received a human-equivalent dose of 35 Gy of radiation (human bioequivalent, 70 Gy) fractionated over 5 days. All groups, including group 3 (distraction osteogenesis, n = 8), underwent a left unilateral mandibular osteotomy with bilateral external fixator placement. Distraction osteogenesis was performed at a rate of 0.3 mm every 12 hours to reach a gap of 5.1 mm. Group 2 was injected with parathyroid hormone (60 µg/kg) subcutaneously daily for 3 weeks after the start of distraction osteogenesis. On postoperative day 40, all left hemimandibles were harvested. Biomechanical response parameters were generated. Statistical significance was considered at p ≤ 0.05.

RESULTS

Parathyroid hormone-treated mandibles had significantly higher failure load and higher yield than did untreated mandibles. However, these values were still significantly lower than those of nonirradiated mandibles.

CONCLUSIONS

The authors have successfully demonstrated the therapeutic efficacy of parathyroid hormone to stimulate and enhance bone regeneration in their irradiated murine mandibular model of distraction osteogenesis. Anabolic regimens of parathyroid hormone, a U.S. Food and Drug Administration-approved drug on formulary, significantly improve outcomes in a model of postoncologic craniofacial reconstruction.

Quantitative histologic evidence of amifostine-induced cytoprotection in an irradiated murine model of mandibular distraction osteogenesis

BACKGROUND

Head and neck cancer management requires adjuvant radiotherapy. The authors have previously demonstrated the damaging effect of a human equivalent dose of radiation on a murine mandibular model of distraction osteogenesis. Using quantitative histomorphometry, the authors' specific aim was to objectively measure amifostine radioprotection of the cellular integrity and tissue quality of an irradiated and distracted regenerate.

METHODS

Sprague-Dawley rats were assigned randomly into two groups: radiotherapy/distraction osteogenesis and amifostine/radiotherapy/distraction osteogenesis, which received amifostine before radiotherapy. Both groups received a fractionated human equivalent dose of radiation prior to left mandibular osteotomy with fixator placement. Distraction to 5.1 mm was followed by a 28-day consolidation period. Quantitative histomorphometry was performed on left hemimandibles for osteocytes, empty lacunae, bone volume-to-tissue volume ratio, and osteoid volume-to-tissue volume ratio.

RESULTS

Amifostine/radiotherapy/distraction osteogenesis exhibited bony bridging as opposed to radiotherapy/distraction osteogenesis fibrous unions. Quantitative histomorphometry analysis revealed statistically significant higher osteocyte count and bone volume-to-tissue volume ratio in amifostine-treated mandibles compared with irradiated mandibles. There was a corresponding decrease in empty lacunae and the ratio of osteoid volume-to-tissue volume between both groups.

CONCLUSIONS

The authors have successfully established the significant osseous cytoprotective and histoprotective capacity of amifostine for distraction osteogenesis in the face of radiotherapy. The amifostine-sparing effect on bone cellularity correlated with increased bony unions and elimination of fibrous union. The authors posit that the demonstration of similar efficacy of amifostine in the clinic may allow the successful implementation of distraction osteogenesis as a viable reconstructive option for head and neck cancer in the future.

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.

Amifostine remediates the degenerative effects of radiation on the mineralization capacity of the murine mandible

BACKGROUND

Radiotherapy, a cornerstone of head and neck cancer treatment, causes substantial morbidity to normal adjoining bone. The authors assessed the radioprotective effect of amifostine therapy on the mineralization of the mandible using micro-computed tomography. They hypothesized that amifostine would safeguard the mandible from radiation-induced disruption of the mineralization process and the associated failure of new bone creation.

METHODS

Male Sprague-Dawley rats were randomized into three groups: control (n = 8), radiation therapy (n = 5), and amifostine (n = 8). Animals in the radiation therapy and amifostine groups underwent human bioequivalent radiation of 70 Gy in five fractions to the left hemimandible. Fifty-six days after irradiation, the hemimandibles were harvested for radiomorphometric analyses.

RESULTS

Amifostine-treated animals exhibited less alopecia, mucositis, and weight loss in addition to increased cortical density in comparison with those treated with radiation therapy. Bone and tissue mineral densities showed statistically significant improvement in amifostine versus radiation therapy, and no difference was observed between amifostine and control groups. Detailed micro-computed tomographic analysis further demonstrated significant differences in the mineralization profile when comparing radiation therapy and amifostine. Amifostine maintained regions of lower mineralization consistent with the preservation of normal remodeling.

CONCLUSIONS

The authors have successfully demonstrated the ability of amifostine pretreatment to protect the natural mineralization profile of bone. This reflects the capacity of amifostine prophylaxis to safeguard the normal surrounding mandible from the impediments of collateral damage imposed by irradiation. Further study can correlate these findings with the potential use of amifostine to prevent the devastating associated morbidities of radiotherapy such as pathologic fractures and osteoradionecrosis.

Dose-response effect of human equivalent radiation in the murine mandible: part I. A histomorphometric assessment

BACKGROUND

The authors' laboratory previously demonstrated that radiation significantly alters new bone formation in the murine mandible, impeding the use of distraction osteogenesis as a viable reconstructive option after radiotherapy in head and neck cancer. The authors hypothesize that the deleterious effects of radiation on regenerate formation results from a dose-response depletion of essential osteogenic cells. The authors' specific aim was to use quantitative histomorphometry to objectively measure the human equivalent dose-response effects of radiation on the integrity of the mandible's cellular and tissue composition.

METHODS

Twenty Sprague-Dawley rats were randomized into three radiation dosage groups: low (5.91 Gy), middle (7 Gy), and high (8.89 Gy), delivered in five daily fractions. These dosages approximated 75, 100, and 150 percent, respectively, of the biological equivalent dose the mandible experiences in the clinical regimen of head and neck cancer patients. Hemimandibles were harvested 56 days after radiation and stained with Gomori trichrome. Quantitative histomorphometry was performed using Bioquant software and analysis with a one-way analysis of variance Kruskal-Wallis test.

RESULTS

The authors' data revealed a statistically significant diminution in the mean number of osteocytes. The authors also demonstrated a corresponding significant increase in the mean values of empty lacunae. Both of these quantitative histomorphometric changes demonstrated a dose-response relationship.

CONCLUSIONS

The authors' study supports their hypothesis that radiation induces a dose-response depletion in osteocytes and an increase in empty lacunae. These reliable and reproducible metrics can now be used to determine the efficacy of therapies aimed at safeguarding the cells essential for optimal bone regeneration and potentially enhance the use of distraction osteogenesis in head and neck cancer patients.