Effect of mandibular titanium reconstructive plates on radiation dose

Hardware Complication Risks in Head and Neck Cancer Patients Undergoing Reconstructive Surgery With Segmental Mandibulectomy

BACKGROUND

The primary objective of this study was to ascertain the risk factors associated with hardware complications following segmental mandibular reconstruction in head and neck cancer patients. Additionally, we sought to develop a nomogram model that enables accurate risk prediction.

METHODS

Patients who underwent segmental mandibulectomy with immediate free or local regional tissue transfer between January 2016 and December 2020 were reviewed. Hardware complications were defined. Patient demographics and perioperative parameters were analyzed.

RESULTS

A total of 510 patients were analyzed. Postoperative radiation therapy (OR = 2.296, 95% CI = 1.339-3.938, p = 0.003), postoperative wound infection (OR = 2.367, 95% CI = 1.472-3.806, p < 0.001), and debridement for flap-related complications (OR = 5.484, 95% CI = 3.269-9.199, p < 0.001) were identified as independent risk factors. The nomogram model demonstrated good discriminatory ability.

CONCLUSION

This comprehensive analysis identified three independent risk factors, and the nomogram provides a valuable tool for predicting the risks. Further research is needed to validate these findings and explore preventive strategies.

Management of metallic implants in radiotherapy

The number of patients with metallic implant and treated with radiotherapy is constantly increasing. These hardware are responsible for the deterioration in the quality of the CT images used at each stage of the radiation therapy, during delineation, dosimetry and dose delivery. We present the update of the recommendations of the French society of oncological radiotherapy on the pros and cons of the different methods, existing and under evaluation, which limit the impact of metallic implants on the quality and safety of radiation treatments.

Tissue response after implantation of pure titanium and bioresorbable screws in scapula with postoperative irradiation: an experimental study on rats

OBJECTIVE

The study focuses on the comparison of tissue reaction to titanium and bioresorbable implants with and without postoperative irradiation on an animal model.

MATERIALS AND METHODS

Thirty-nine LEW/W rats were randomly assigned to experimental or control groups. One titanium and one bioresorbable screw (poly-L-lactide [PLLA] and L- and D-lactide poly-L/D-lactide [PDLLA]) were implanted into the left scapulas of 24 rats. Half of them received 30 Gy to the operation site and the other half received 42 Gy. In the control groups, 3 rats received 30 Gy, and 6 rats received 42 Gy to the scapula area without operation; and 6 rats had implants inserted as in the experimental group, but received no postoperative irradiation. The scapulas were removed 14 or 30 days after irradiation and a histologic analysis was performed.

RESULTS

The host tissue reaction to titanium and PLLA-PDLLA screws without postoperative irradiation was of similar intensity. In irradiated animals, the inflammatory tissue reaction was more evident around the titanium screws than around the bioresorbable screws, irrespective of the radiation dose and of the time that elapsed from the irradiation. The reaction was more evident on the 14th day than on the 30th day after the last radiation dose (70 and 86 days after surgery, respectively). The intensity of the inflammatory tissue reaction, irrespective of the implant type, was more intense in the group irradiated with 42 Gy.

CONCLUSIONS

PLLA-PDLLA implants appear to cause less tissue reaction after irradiation and could be safer reconstructive devices than titanium implants for patients undergoing surgery and adjuvant radiotherapy for cancer.

Monte Carlo simulation and film dosimetry for electron therapy in vicinity of a titanium mesh

Titanium (Ti) mesh plates are used as a bone replacement in brain tumor surgeries. In the case of radiotherapy, these plates might interfere with the beam path. The purpose of this study is to evaluate the effect of titanium mesh on the dose distribution of electron fields. Simulations were performed using Monte Carlo BEAMnrc and DOSXYZnrc codes for 6 and 10 MeV electron beams. In Monte Carlo simulation, the shape of the titanium mesh was simulated. The simulated titanium mesh was considered as the one which is used in head and neck surgery with a thickness of 0.055 cm. First, by simulation, the percentage depth dose was obtained while the titanium mesh was present, and these values were then compared with the depth dose of homogeneous phantom with no titanium mesh. In the experimental measurements, the values of depth dose with titanium mesh and without titanium mesh in various depths were measured. The experiments were performed using a RW3 phantom with GAFCHROMIC EBT2 film. The results of experimental measurements were compared with values of depth dose obtained by simulation. In Monte Carlo simulation, as well as experimental measurements, for the voxels immediately beyond the titanium mesh, the change of the dose were evaluated. For this purpose the ratio of the dose for the case with titanium to the case without titanium was calculated as a function of titanium depth. For the voxels before the titanium mesh there was always an increase of the dose up to 13% with respect to the same voxel with no titanium mesh. This is because of the increased back scattering effect of the titanium mesh. The results also showed that for the voxel right beyond the titanium mesh, there is an increased or decreased dose to soft tissues, depending on the depth of the titanium mesh. For the regions before the depth of maximum dose, there is an increase of the dose up to 10% compared to the dose of the same depth in homogeneous phantom. Beyond the depth of maximum dose, there was a 16% decrease in dose. For both 6 and 10 MeV, before the titanium mesh, there was always an increase in dose. If titanium mesh is placed in buildup region, it causes an increase of the dose and could lead to overdose of the adjacent tissue, whereas if titanium mesh is placed beyond the buildup region, it would lead to a decrease in dose compared to the homogenous tissue.

Effects of neurosurgical titanium mesh on radiation dose

The purpose of this study was to determine the dosimetric impact of a neurosurgical titanium mesh in patients treated with 6- and 18-MV photon beams. The effects of a 0.4-mm-thick titanium mesh on the dose profile at 3 regions within a solid water phantom were measured using extended dose range-2 (EDR2) film for 6- and 18-MV photon beams. All measurements were performed with the titanium mesh placed at a depth of 1.5 cm in the phantom. Films were exposed immediately above the mesh, immediately below the mesh, and at a depth of 5 cm from the surface of the phantom. The films were scanned using a scanning densitometer. In the region directly above the titanium mesh, there was an increase in dose of 7.1% for 6-MV photons and 4.9% for 18-MV photons. Directly below the titanium mesh, there was an average decrease in dose of 1.5% for 6-MV photons and an increase of 1.0% for 18-MV photons. At 5-cm depth, for 6- and 18-MV photons, there was a decrease in dose of 2.2% and 0.6%, respectively. We concluded that for cranial irradiation with high-energy photons, the dosimetric impact of a 0.4-mm titanium mesh is small and does not require modification in treatment parameters.

Mandibular reconstruction in 2004: an analysis of different techniques

PURPOSE OF REVIEW

The field of mandibular reconstruction has evolved dramatically over the past fifty years. Numerous advances in microsurgical technique, plating technology and instrumentation, and an understanding of donor site angiosomes have made consistent and reliable mandibular reconstruction possible. Refinements in technique continue to improve the functional and aesthetic outcomes of oromandibular reconstruction. This review discusses the current state-of-the-art techniques for mandibular reconstruction and highlights the latest innovations in technique.

RECENT FINDINGS

The most common indication for oromandibular reconstruction remains ablative surgery for advanced neoplastic processes of the oral cavity and oropharynx. Reconstruction of these complex three-dimensional composite bony and soft-tissue defects is paramount for rehabilitation of form and function. Vascularized osseous free tissue transfer is the state-of-the-art for mandibular reconstruction. The long-term excellent functional and aesthetic outcomes of this technique have recently been reported. The most commonly used free flaps for mandibular reconstruction are the fibula, iliac crest, and scapula. Each of these typically accepts endosseous implants improving functional outcomes. The use of mandibular reconstruction plates and coverage with a soft-tissue flap remains a reconstructive option for selected patients. The latest refinements in technique include temporary intraoperative external fixation, the use of periosteal free flaps, distraction osteogenesis, and development of biodegradable biopolymer scaffolds for mandibular defects.

SUMMARY

Oromandibular reconstruction, although a challenge for the head and neck reconstructive surgeon, is now reliable and highly successful with excellent long-term functional and aesthetic outcomes.