Distraction Osteogenesis of Radiation-Induced Orbitozygomatic Hypoplasia

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.

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.

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.

Sequential maxillary bifocal transport distraction osteogenesis after radiotherapy

Maxillary defects secondary to ablative surgery are common, and functional maxillary reconstruction is challenging. Adjuvant radiotherapy further complicates reconstructive surgical planning. In this article, successful functional reconstruction of a partial maxillary defect was achieved using segmental osteotomy, sequential bifocal distraction osteogenesis, and prosthodontic treatment. The current evidence is reviewed, and the surgical planning and technique are described in detail.

Regenerate healing outcomes in unilateral mandibular distraction osteogenesis using quantitative histomorphometry

BACKGROUND

The authors' goal was to ascertain regenerate bone-healing metrics using quantitative histomorphometry at a single consolidation period.

METHODS

Rats underwent either mandibular distraction osteogenesis (n = 7) or partially reduced fractures (n = 7); their contralateral mandibles were used as controls (n = 11). External fixators were secured and unilateral osteotomies performed, followed by either mandibular distraction osteogenesis (4 days' latency, then 0.3 mm every 12 hours for 8 days; 5.1 mm) or partially reduced fractures (fixed immediately postoperatively; 2.1 mm); both groups underwent 4 weeks of consolidation. After tissue processing, bone volume/tissue volume ratio, osteoid volume/tissue volume ratio, and osteocyte count per high-power field were analyzed by means of quantitative histomorphometry.

RESULTS

Contralateral mandibles had statistically greater bone volume/tissue volume ratio and osteocyte count per high-power field compared with both mandibular distraction osteogenesis and partially reduced fractures by almost 50 percent, whereas osteoid volume/tissue volume ratio was statistically greater in both mandibular distraction osteogenesis specimens and partially reduced fractures compared with contralateral mandibles. No statistical difference in bone volume/tissue volume ratio, osteoid volume/tissue volume ratio, or osteocyte count per high-power field was found between mandibular distraction osteogenesis specimens and partially reduced fractures.

CONCLUSIONS

The authors' findings demonstrate significantly decreased bone quantity and maturity in mandibular distraction osteogenesis specimens and partially reduced fractures compared with contralateral mandibles using the clinically analogous protocols. If these results are extrapolated clinically, treatment strategies may require modification to ensure reliable, predictable, and improved outcomes.