Distraction osteogenesis in the irradiated mandible. A case report

Evaluation of Transport Distraction Osteogenesis in Maxillofacial Region

Introduction

Transport distraction osteogenesis (TDO) is a novel reconstructive modality for mandibular ablative defects, precluding donor site morbidity. Assessing of TDO regenerate that could assist in modifying the distraction strategy for patient specific needs.

Materials and Methods

Present study enrolled 17 patients with mandibular defects of size < 12 cm, divided in two groups ≤35 years (A) and > 35 years (B); and assessed the TDO regenerate by clinically examining intra as well as post operatively, using orthopantomogram (OPG), ultrasonography (USG), color Doppler (CD) and cone beam computed tomography (CBCT).

Results

Group B had a longer latency period (p = 0.001) and consolidation period (p = 0.002) than group A. Paired sample correlation study of clinical defect and TDO regenerate (p 0.004) indicate that a better length of regenerate is possible with TDO in mandibular defects. OPG, USG and CBCT shown a significant difference in bone mineralization observed within different age groups except for CD. USG representing earlier detection of mineralization than OPG over the consolidation period.

Conclusion

Use of TDO for reconstruction of mandibular defects is advantageous as the regenerated bone and soft tissues matches the existing anatomical tissues. Evaluation by USG, OPG and CBCT could aid in providing patient specific protocols for TDO in Maxillofacial region.

Acquired Facial, Maxillofacial, and Oral Asymmetries—A Review Highlighting Diagnosis and Management

Facial asymmetry refers to the absence of, or the deviation from the regular mirror image of facial structures, relative to a referenced midline axis. It can be attributed to a wide spectrum of deformities, including congenital, developmental, or acquired conditions, which can originate either prenatally or postnatally. Though highly prevalent, asymmetry commonly goes undiagnosed due to its subtle or relative nature. Among the spectrum of conditions, acquired cases are triggered postnatally, in previously normal individuals, thus subjecting them to sudden, eventful psychological and psychosocial disharmony. When detected early, timely management may help intervene progressive growth of these conditions. This, therefore, emphasizes the need for a thorough diagnostic workup including medical/dental history, clinical examinations, study models, photographic and radiographic records for a case-by-case basis to prevent severe functional and aesthetic complications. Recently, advanced diagnostic procedures, such as stereophotogrammetry, 3D stereolithographic models, skeletal scintigraphy (radionucleotide scans), 3D computed tomographic scans, cone-beam computed tomography, and magnetic resonance imaging, have provided innovative diagnostic instruments for numerous craniofacial defects. This descriptive review aims at focusing on the factors leading to frequently encountered conditions of acquired facial asymmetry and highlights their clinical evaluation, conservative and surgical interventions by a multi-disciplinary team of clinicians.

Distraction Osteogenesis in Craniofacial Surgery: Past, Present, and Future

ABSTRACT

Distraction osteogenesis (DO) is considered one of the treatments of choice for the surgical correction of malformations of the craniofacial skeleton. This is due to its ability to generate bone at the distraction site along with the accompanying soft tissue changes, the possibility to combine DO with traditional orthognathic procedures and the successful reported long-term outcomes following its application to various craniofacial deformities. The aim of this review is to present an overview of the literature on the evolution of DO applications in craniofacial surgery through the last 35 years.

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.

Is Distraction Osteogenesis of the Irradiated Craniofacial Skeleton Contraindicated?

BACKGROUND

Craniofacial distraction osteogenesis (DO) is a common treatment modality today. Despite its numerous advantages, however, concerns have been expressed regarding the use of DO in the irradiated setting.

METHODS

A systematic review was performed to identify all published reports of patients who underwent DO of the irradiated craniofacial skeleton. The following parameters were of particular interest: postoperative complications, specifically, insufficient bone formation, fracture, and hardware exposure (intraoral and cutaneous), as well as the need for additional bone grafting.

RESULTS

The initial search retrieved a total of 183 articles of which 20 articles (38 patients) met predetermined inclusion criteria. The most common site of distraction was the mandible (76.3%). The median radiation dose was 50.7 Gy (range, 30-70 Gy). Bone defects ranged from 30 to 80 mm (median, 42.5 mm). Complications were encountered in 19 patients (50%), with insufficient bone formation being most common (9 patients; 23%). The overall incidence of complications was not significantly associated with radiation dosage (P = 0.79). The remaining procedural and demographic variables also failed to meet statistical significance when compared against the overall complication rate (P = 0.27-0.97).

CONCLUSION

The complication rate associated with craniofacial DO of the irradiated skeleton does not appear to be substantially higher than what is reported for DO in the nonirradiated setting. As such, patients should be offered this treatment modality, particularly in light of the fact, that it offers the option to decrease patient morbidity as well as treatment complexity.

Clinical Use of Deferoxamine in Distraction Osteogenesis of Irradiated Bone

The deleterious effects of radiotherapy, including hypovascularity and hypocellularity, have made distraction of irradiated bones challenging. Animal studies, however, have demonstrated adjunctive measures such as the administration of deferoxamine to significantly improve bone regeneration across irradiated distraction gaps. In this report, the authors demonstrate, for the first time, enhanced bone formation following deferoxamine application in a patient following distraction of a previously irradiated maxilla. Computed tomography imaging of the pterygomaxillary buttress on the side of administration revealed significantly increased bone area and density relative to the contralateral buttress. This is the first presentation of clinical deferoxamine use to promote bone formation following irradiated bone distraction and highlights the promise for this adjunctive measure to make outcomes after distraction of irradiated bone more reliable.

Comparing calvarial transport distraction with and without radiation and fat grafting

The purpose of this study is to: a) assess transport distraction to reconstruct cranial defects in radiated and non-radiated fields b) examine adipose grafting's effect on the bony regenerate and overlying wound, and c) elucidate sources of bone formation during transport distraction osteogenesis. Twenty-three male New Zealand white rabbits (3 months; 3.5 kg) were used, 10 non-irradiated and 13 irradiated (17 treatment, 6 control) with a one-time fraction of 35 Gy. A 16 × 16 mm defect was abutted by a 10 × 16 mm transport disc 5 weeks after irradiation, and 11 animals were fat grafted at the distraction site. Latency (1 day), distraction (1.5 mm/day), and consolidation (4 weeks) followed. Fluorochromes were injected subcutaneously and microCT, fluorescence, and histology assessed. In distracted animals without fat grafting, bone density measured 701.87 mgHA/ccm and 2271.95 mgHA/ccm in irradiated and non-irradiated animals. In distracted animals with fat grafting, bone density measured 703.23 mgHA/ccm and 2254.27 mgHA/ccm in irradiated and non-irradiated animals. Fluorescence revealed ossification emanating from the dura, periosteum, and transport segment with decreased formation in irradiated animals. Transport distraction is possible for cranial reconstruction in irradiated fields but short-term osseous fill is significantly diminished. Adipose grafting enhances wound healing in previously irradiated fields but does not enhance ossification.

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.

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.

A low-grade myofibroblastic sarcoma in the abdominal cavity

Background

Rhabdomyosarcoma is the most common malignant tumor in the nasal and paranasal sinus area at childhood. Multimodal treatment for this disorder has severe side effects due to normal tissue damage. As a result of this treatment, facial growth retardation and oral abnormalities such as malformation of teeth and microstomia can cause esthetic and functional problems.

Case reports

Two cases are presented of patients with severe midfacial hypoplasia and reduced oral function as a result of treatment of rhabdomyosarcoma of the nasopharyngeal and nasal–tonsil region. With a combined surgical (osteotomy, distraction osteogenesis, implants) and prosthetic (implant-based overdenture) treatment, esthetics and function were improved.

"Transport distraction osteogenesis for reconstruction of mandibular defects": our experience

INTRODUCTION

Mandibular defects usually involve a combination of osseous and soft tissue deficiency and are among the most challenging problems in maxillofacial surgery, many options are available for mandibular reconstruction. One of the options discussed in literature recently being distraction osteogenesis.

AIM AND OBJECTIVE

The aims and objectives of the study were to evaluate clinically the technique of distraction osteogenesis to reconstruct mandibular defects, using indigenous transport distractors, and to evaluate the efficacy of Indigenous transport distraction osteogenesis device.

MATERIALS AND METHODS

A prospective, experimental study was designed to examine the use of transport distraction osteogenesis in the treatment of defects of the mandible. Four patients with defects of the mandible were subjected to distraction osteogenesis with indigenously manufactured distraction device. The regenerate was assessed clinically and radiographically.

RESULTS

The results showed that the regenerate was clinically as hard as the adjacent unaffected mandible and radiologic evidence of bone regeneration was observed. The major advantage being regeneration of hard tissue and soft tissue components without the morbidity of donor site, so that functional rehabilitation of the patient is possible.

CONCLUSION

Thus from our study it is shown that transport distraction osteogenesis using indigenous distractors is a reliable yet affordable option for reconstruction of mandibular defects.

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

BACKGROUND

The use of mandibular distraction osteogenesis (MDO) for tissue replacement after oncologic resection in head and neck cancer could have immense therapeutic ramifications. We have previously demonstrated significantly decreased mechanical and microdensitomeric metrics of our MDO regenerate after 36-Gy radiation. Quantitative histomorphometry, a third metric, would permit objective investigation of the effects of radiation on tissue and cellular composition. Our hypothesis is that radiation-induced cellular depletion and diminution in function impair optimal bone regeneration.

METHODS

Five rats received radiation to the left mandible; 5 received none. All animals underwent surgical placement of external fixators, creation of mandibular osteotomies, distraction to a 5.1-mm gap width, and consolidation. Point counting and color thresholding were performed.

RESULTS

There was a significant increase in empty lacunae and a corresponding diminution in osteocytes after radiation. Whereas the volume fraction of mineralized, mature bone was not different, that of nonmineralized, immature osteoid was significantly increased in the radiated group compared with that in the nonradiated group.

CONCLUSIONS

Our findings confirm our prior 2 metrics. Actually, all 3 diverse metrics--microdensitometry, biomechanical analysis, and histomorphometry--corroborate our hypothesis of cellular depletion and diminution of function as the potential mechanism of radiation-induced attenuation in the distracted regenerate. Furthermore, our findings of tissue and cellular changes in the irradiated regenerate elucidate the pathophysiology of decreased bone quality when amalgamated with our previous results. Therapeutic agents may now be introduced, and their effects on the irradiated regenerate critically measured, so that MDO may be used as a viable reconstructive option in patients with head and neck cancer.

Advances in temporomandibular joint reconstruction

PURPOSE OF REVIEW

This article reviews the reconstructive techniques commonly employed in temporomandibular joint (TMJ) surgery with an emphasis on recent developments in the field.

RECENT FINDINGS

TMJ reconstruction remains one of the most challenging tasks faced by surgeons who operate in the head and neck, with a variety of autogenous and alloplastic techniques available. The role of alloplastic TMJ reconstruction needs to be reassessed in light of recent literature showing excellent long-term functional outcomes, which reflect advances in prosthetic materials and surgical technique. More recently, transport distraction osteogenesis has been applied to reconstruction of the ramus-condyle unit with promising early results suggesting it may ultimately become the standard of care in selected patients providing a cost-effective approach with low morbidity and excellent functional outcomes.

SUMMARY

The myriad of available TMJ reconstructive options reflect the fact that it remains an evolving field. Although no gold standard currently exists, the various techniques each have their own proponents and potential advantages and drawbacks. Ultimately, the reconstructive surgeon must consider the ablative defect and underlying pathology, the needs of the individual patient, the resources of the providing institution and the capabilities of the surgical team.

Alteration in volumetric bone mineralization density gradation patterns in mandibular distraction osteogenesis following radiation therapy

BACKGROUND

The use of mandibular distraction osteogenesis for tissue replacement after oncologic resection or for deformations secondary to radiotherapy could have immense therapeutic ramifications. Radiotherapy, however, drastically impairs bone healing, potentially precluding the use of mandibular distraction osteogenesis as a durable reconstructive option. The authors have previously demonstrated significantly decreased mechanical and histologic metrics of the mandibular distraction osteogenesis regenerate after 36 Gy. The authors' goal is to now investigate the effect of these same radiation dosages on bone densitometrics using micro-computed tomographic scanning.

METHODS

Six Sprague-Dawley rats received 36-Gy fractionated radiotherapy sessions to the left mandible; six received none. All animals had external fixators placed, creation of osteotomies, distraction, and consolidation. Mandibles were scanned with micro-computed tomographic scanning. Volumetric density and microdensitometric measurements were analyzed.

RESULTS

There was a significant difference in volumetric bone mineralization patterns in irradiated animals. Bone volume fraction and bone mineral density, however, demonstrated no significant differences.

CONCLUSIONS

The authors discovered a significant increase of low mineralized, immature bone and a significant decrease of highly mineralized, mature bone in the irradiated regenerate. These findings corroborate the authors' hypothesis that radiation induces a diminution in cell function, impairing optimal bone regeneration. Overall densitometrics, however, were unchanged according to micro-computed tomographic measurements, despite documented significant changes in biomechanical and histologic metrics. An optimal radiation dose must now be sought that demonstrates a higher degree of reproducible degradation, but not irreversible destruction, in all three outcomes. Such an approach will allow formulation of therapeutic interventions designed to enhance mandibular distraction osteogenesis so that it may be used as a viable reconstructive option.

Biomechanical assessment of regenerate integrity in irradiated mandibular distraction osteogenesis

BACKGROUND

The role of mandibular distraction osteogenesis for reconstructing mandibular defects following radiation therapy depends on the quality of attenuated bone healing in the regenerate. This study investigated the regenerate properties after radiation therapy using yield and breaking load. The authors hypothesized that both would be significantly reduced in mandibular distraction osteogenesis following radiation therapy compared with mandibular distraction osteogenesis alone.

METHODS

Male Sprague-Dawley rats underwent left mandibular fractionated 36-Gy preoperative external beam radiation therapy and then 2 weeks of recovery (n = 7) or no radiation therapy (n = 10) before surgery. External fixators were secured and unilateral osteotomies were created behind the third molar, followed by 4 days of latency and then mandibular distraction osteogenesis: 0.3 mm every 12 hours for 8 days (5.1 mm) and 4 weeks of consolidation. Unoperated controls received no radiation therapy (n = 13). Mandibles were tension tested at 0.5 mm/second to failure, and yield and breaking load were determined.

RESULTS

There was a significantly lower breaking load for mandibular distraction osteogenesis following radiation therapy compared with mandibular distraction osteogenesis, alone, but there was no significant difference in yield between the groups. Both groups had significantly lower breaking load and yield when compared with unoperated controls.

CONCLUSIONS

The lowered breaking load in mandibular distraction osteogenesis following radiation therapy reflects the reduced biomechanical quality of the regenerate, despite evidence of radiographic union. These data show that radiographic union is not an adequate outcome measure for regenerate healing and support the need to define quantitative bone-healing metrics in mandibular distraction osteogenesis following radiation therapy before implementation in head and neck reconstruction.

Current Options in Head and Neck Reconstruction

LEARNING OBJECTIVES

After studying this article, the participant should be able to: 1. Understand current trends in the treatment of head and neck cancer. 2. Discuss the challenges of reconstructing head and neck defects 3. Understand the different reconstructive options available for specific anatomical regions of the head and neck.

BACKGROUND

Reconstructive surgery of the head and neck is both technically challenging and rewarding. In the past 20 years, significant advances in this field have improved surgical outcomes and patient function. The development and subsequent refinement of microvascular techniques, in particular, have been a major reason for this progression.

METHODS

In this article, the authors review the current options available in head and neck reconstruction. Because a large number of major craniocervicofacial defects result from oncologic resection, the authors have focused their review on this particular subject. By dividing their discussion into different anatomical sites, the authors hope to cover all major aspects of this broad topic.

RESULTS

Free tissue transfer has revolutionized head and neck reconstruction. The most widely used free flaps include the fibula, radial forearm, anterolateral thigh, and rectus abdominis. Restoration of both form and function is the ultimate goal.

CONCLUSIONS

Although defects of the head and neck region present a challenge, successful cosmetic and functional results have been achieved with both local and free tissue flaps. The flexibility of free tissue transfer, however, has dominated this area and continues to be the method of choice for reconstruction of sizable defects.