Mandibular reconstruction using a titanium plate: the impact of radiation therapy on plate preservation

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.

Mandibular reconstruction in head and neck cancer: which is the gold standard?

INTRODUCTION

The aim of this study is to perform a systematic review to compare the outcomes of the different surgical options for mandibular reconstruction in head and neck cancer.

MATERIAL AND METHODS

93 articles were selected. Four groups were identified: titanium plate without flaps, titanium plate covered by soft tissue flap, bone tissue flaps and double flaps. We compared patients' characteristics, site of mandibulectomy, type of reconstruction and complications.

RESULTS

4697 patients were reported. The groups were not homogeneous regarding the type of defect and the treatment history. A significant difference in terms of post-operative complications was found between group 1 and group 2 (p < 0.00001), and between group 2 and group 3 (p < 0.00001). Total complications rate for group 4 was significantly higher when compared to group 3 (p < 0.00001), but no significant difference was found with group 2.

CONCLUSION

These results suggest that mandibular reconstruction using a microvascular bone flap is the best surgical option in patients without significant comorbidities.

A novel alloplastic grid reconstruction plate for the mandible - Retrospective comparative clinical analysis of failure rates and specific complications

PURPOSE

This study aimed to investigate the effect of three different osteosynthesis plate systems on failure rates and complications after continuity-interrupting mandibular resections with alloplastic reconstructions.

MATERIALS AND METHODS

Records of respective patients from 2010 to 2020 were analyzed retrospectively. The analyses included the osteosynthesis plate type (2.4 MANDIBULAR (RP1: MANDIBULAR [Medicon®, Tuttlingen, Germany]; RP2: Modus® Reco 2.5 [Medartis®, Basel, Switzerland]; and RP3: Modus 2 Mandible [Medartis®, Basel, Switzerland]), extent & location of the defect, age, sex, radiotherapy, and nicotine abuse. In case of failure, timepoint, and the problem, namely oral/extraoral dehiscence, screw loosening, and plate fractures that led to removal, were analyzed. Complications were classified according to Clavien-Dindo system.

RESULTS

A total of 136 patients were included. The mean follow-up time was 18 ± 26 months. Survival rates after 1, 2, and 5 years were 69.9%, 66.9%, and 64.7%, respectively. Although survival was not significantly associated with the reconstruction system, the most frequent complications were seen in cases of RP1 & RP2 when compared to RP3 (p = 0.033). In brief, dehiscences were seen significantly less often in cases of RP3 (12.5%) when compared to RP1 (44.7%) and RP2 (26.9%; p = 0.024). Fractures of the osteosynthesis systems occurred in 3 of 4 cases (75%) with RP1, in 1 of 4 cases (25%) using RP2, and in no single case using the RP3 system (p = 0.03). Most of the observed complications occurred up to 12 months postoperatively. A total plate survival rate of 64.7% and a total plate complication rate of 47.8% were seen.

CONCLUSION

In conclusion, it seems that RP3 should be preferred over RP1 and RP2 regarding failure rates and complications.

Plate-related complication and health-related quality of life after mandibular reconstruction by fibula flap with reconstruction plate or miniplate versus anterolateral thigh flap with reconstruction plate

BACKGROUND

Plate-related complications are major long-term complications in mandible reconstruction. There are controversies regarding the use of a reconstruction plate versus miniplates and a bone flap versus a soft tissue flap with a bridging plate. Direct comparisons of a fibula flap and an anterolateral thigh flap, the applicability between a reconstruction plate and miniplate, and the correlation between plate-related complications and quality of life remain unclarified. Therefore, this study aimed to the explore complications of different flaps and plates and how they impact the patients' quality of life.

METHODS

We retrospectively reviewed the medical records of a total of 205 patients aged >18 years who underwent segmental mandibulectomy and reconstruction using fibula flap with reconstruction plate (FR; n = 86), fibula flap with miniplate (FM; n = 61), and anterolateral thigh flap with reconstruction plate (AR; n = 58) due to cancer ablation, osteoradionecrosis, or benign tumor excision between August 2010 and December 2019. Data on characteristics, complications, and health-related quality of life were collected and analyzed.

RESULTS

The plate-related complication rate was the highest in the AR group (37.9%), then in the FR group (25.6%), and was the lowest in the FM group (13.1%; p = 0.0079). The plate exposure rate was the highest in the AR group (24.1%), then in the FR group (15.7%), and was the lowest in the FM group (4.9%; p = 0.0128). The plate fracture and dislodge rates for the AR group were both higher than those for the FR and FM groups (24.1% versus 9.3% versus 9.8%, respectively; p = 0.023). The AR group had worse complication-free survival (hazard ratio [HR]: 3.61, 95% CI: 1.99-6.56, and p < 0.0001) than the FR and FM groups. Osteoradionecrosis (HR: 6.19, 95% CI: 2.11-18.21, and p = 0.0009) and postoperative radiotherapy (HR: 2.87, 95% CI: 1.34-6.12, and p = 0.0402) were both independent adverse factors for complication-free survival, whereas patient treated primarily (HR: 0.35, 95% CI: 0.17-0.73, and p = 0.0048) was an independent protective factor. Plate-related complication negatively impacted the quality of life based on pain scores (β: -0.56, SE: 0.26, and p = 0.034).

CONCLUSIONS

Using a fibular flap fixed with miniplates and avoiding the use of a reconstruction plate may yield a reduced plate exposure rate and better health-related quality of life, particularly for patients with osteoradionecrosis or those who need postoperative radiotherapy.

Prognostic factors and related complications/sequalae of squamous cell carcinoma located in the gingivobuccal complex

Background

Gingivobuccal complex (GBC) was a relatively new concept of oral subsite that was comprises of the upper and/or lower gingiva, gingival buccal sulcus, and adjacent buccal mucosa. Squamous cell carcinoma (SCC) of the GBC had a poor prognosis, with few studies analyzing this particular entity. The objective of this study was to analyze the risk factors affecting the prognosis and complications/sequalae of gingivobuccal complex cancer.

Methods

Between December 2014 and August 2019, a total of 122 patients diagnosed with primary gingivobuccal complex cancer in Beijing Stomatological Hospital, Capital Medical University were enrolled in the study. Through outpatient reviewed and telephone followed-up for 2-5 years postoperatively, postoperative relapse and complications/sequalae were assessed. The primary outcome parameter was 2-year disease-free survival.

Results

The most common central site of the tumor was the buccal mucosa (45.1%), followed by the lower gingiva (36.9%). The most diseases were pT4a (45.1%) and there was lymph node invasion (pN+) in 41.8% of patients. Moderate differentiated squamous carcinoma (77.9%) accounted for the vast majority of the histopathological differentiation. A total of 62.3% of tumors invaded the bone, while, 5.7% invaded the skin layer. Survival analysis found that 44.3% of patients experienced relapse within two years postoperatively and the mortality rate after relapse was 75.9%. Almost 60.0% of the tumors involving the maxilla and/or mandible developed relapse. Cox proportional hazards model found that pN stage (p= 0.002) and bone invasion (p= 0.007) were significant independent predictors of 2-year disease-free survival. Importantly, 63.1% of patients had postoperative (and postradiotherapy) complications/sequalae. It was noteworthy that 18 of 43 patients (41.9%) who implanted with titanium plates had hardware-related complications/sequalae, and the most of them were titanium plate exposure (61.1%).

Conclusions

Squamous cell carcinoma of the gingivobuccal complex cancer, as a new subsite worthy of attention in oral cancer, has a high complication/sequalae rate, high relapse rate and poor prognosis.

Trial registration

Prospective, Observational, Real-world Oral Malignant Tumors Study (clinicaltrials.gov identifier: NCT02395367). The approval of the Institutional Review Board of the Beijing Stomatological Hospital of Capital Medical University (Approval number: CMUSH-IRB-KJPJ-2015-08)

Dental implants rehabilitation in a patient with head and neck radiotherapy for osteosarcoma in the jaw. A clinical case report

A 52-year-old female patient with a diagnostic of osteosarcoma in the mandible, in which it was necessary a reconstruction with a microvascularized osteomyocutaneous fibula bone. Coadjuvant chemotherapy was scheduled. Two years later, 4 osseointegrated implants (OII) were placed in the fibula a 2 OII in the right mandible, using a splint guided surgery. The final prosthodontic consisted in a metal ceramic restoration using CAD/ CAM technology.

Key words:Oral rehabilitation, oral cancer, head and neck radiotherapy, oral oncology.

Complications After Soft Tissue With Plate vs Bony Mandibular Reconstruction: A Systematic Review and Meta-analysis

OBJECTIVE

Mandibular reconstruction for segmental defects is a well-studied topic. However, there are conflicting data on the risks of delayed plate-related complications. The objective of this systematic review and meta-analysis was to assess long-term plate-related complications following reconstruction of the mandible with soft tissue and a plate as compared with immediate vascularized bony reconstruction.

DATA SOURCES

A medical librarian created search strategies with a combination of keywords and controlled vocabulary in Ovid Medline (1946-), Embase (1947-), Scopus (1960-), Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and Clinicaltrials.gov.

REVIEW METHODS

Candidate articles were independently reviewed by 2 authors. Inclusion/exclusion criteria were uniformly applied. Articles were considered eligible if they included adequate reporting of plate extrusion and/or fracture and had follow-up ≥12 months.

RESULTS

A total of 2379 patients were included. The risk of plate fracture was low in cases of soft tissue with a plate (5%; 95% CI, 0.03-0.08) and osseous reconstruction (1%). The risk of extrusion following soft tissue and plate reconstruction was 20% (95% CI, 0.15-0.27). In the osseous reconstruction group, the risk of extrusion was 10% (95% CI, 0.06-0.18). Revision surgery was performed twice as often following soft tissue with a plate as compared with vascularized bony reconstruction (32% [95% CI, 0.25-0.40] vs 14% [95% CI, 0.09-0.21], respectively).

CONCLUSION

Delayed plate-related complications remain a significant problem following segmental defect reconstruction. Soft tissue and plate reconstruction techniques may increase the risk of plate removal and revision surgery.

A small number of residual teeth after the mandibular resection of oral cancer is associated with titanium reconstruction plate exposure

Objective

Reconstruction plates are used to treat patients with a segmental mandibular defect after oral cancer surgery. Reconstruction plate failure analysis has rarely focused on occlusion, which conducts a mechanical force to the mandible and the plate. To determine the prognostic factors, we retrospectively evaluated patients who underwent reconstruction of a mandibular segmental defect with a reconstruction plate and assessed the number of residual paired teeth.

Material and Methods

From among 390 patients with oral cancer who visited University of Tsukuba Hospital (Tsukuba, Japan) between 2007 and 2017, we selected and analyzed the data of 37 patients who underwent segmental resection of the mandible and reconstruction with reconstruction plates. Prognostic factors evaluated were patient age, sex, TNM classification, plate manufacturer, treatment with radiotherapy or chemotherapy, whether the patient had diabetes or smoked, and whether the patient had a small number of residual paired teeth, plate length, and use of a fibular‐free flap. Among these 37 patients, eight reconstruction plates had intraoral or extraoral exposure and were removed in 5 years.

Results

Kaplan–Meier and log‐rank analyses revealed that the prognosis for the 5‐year plate exposure‐free rate was significantly poorer for patients with a small number of residual teeth than for patients with no teeth or those with a large number of residual teeth (.01). Univariate Cox regression analysis revealed that a small number of residual teeth was a significant prognostic factor in the loss of a reconstruction plate (hazard ratio: 5.63; 95% confidence interval [1.10, 25.85]; .04).

Conclusions

A small number of residual teeth after the segmental resection of oral cancer is significantly involved in reconstruction plate survival and may be important in predicting reconstruction plate prognosis.

Study of Quality of Life in Patients with Soft Tissue Reconstruction Following Mandibulectomy

Purpose

To study the effect of mandibulectomy with soft tissue reconstruction on quality of life (QOL) and functions of speech and swallowing.

Methodology

Quality of life of 66 patients was evaluated by using EORTC QLQ-C30 and EORTC-HN35 questionnaires. Speech was evaluated objectively by Dr. Speech software version 4 and subjectively by a single speech therapist along with swallowing. Patients were evaluated preoperatively and 6 months after treatment.

Results

Out of 66 patients, 57 followed up postoperatively. Comparison of preoperative and postoperative QOL, speech, and swallowing was done by using paired 't' test or Wilcoxon signed-rank test as per distribution. When evaluated by EORTC QLQ-C30 and EORTC-HN35, statistically significant difference was found in the domains of physical function, fatigue, nausea-vomiting, dyspnea and appetite loss, pain, nutrition, swallowing speech and dry mouth. Significant difference was found in speech (maximum intensity) and most of the domains of swallowing.

Conclusion

In EORTC QLQ-C30 questionnaire, all functional scales showed deterioration with maximum in physical function. Symptom scales showed worsening but significant improvement was found in pain when evaluated by EORTC-HN35. However, the global health status/QL was found to be improved marginally.

Mandibular reconstruction using customized three-dimensional titanium implant

Mandibular defects lead to severe deformation and functional deficiency. Vascularized osteocutaneous tissue has been widely used to reconstruct the mandible. However, it is technically challenging to shape this type of grafts in such a manner that they resemble the configuration of the mandible. A 48-year-old female patient who underwent anterolateral thigh (ALT) flap coverage after a tongue cancer excision was diagnosed with a tumor recurrence during the follow-up. A wide excision mandibulectomy and mandibular reconstruction with an ALT flap and a titanium implant were performed. The prefabricated titanium implant was fixed to the condyle. Then, an ALT flap was harvested from the ipsilateral thigh and anastomosed. After confirming that the circulation of the flap was intact, the implant was fixed to the parasymphysis. On the radiograph taken after the surgery, the prosthesis was well positioned and overall facial shape was acceptable. There was no postoperative complication during the follow-up period, 1 year and 2 months. The prefabricated implant allows the restoration of facial symmetry without harvesting autologous bone and it is a safe and effective surgical option for mandibular reconstruction.

Trismus in patients with head and neck cancer: etiopathogenesis, diagnosis and management

BACKGROUND

Trismus indicates severely restricted mouth opening of any aetiology. A mouth opening of 35 mm or less should be regarded as trismus. Aim of this study was to review the etiopathogenesis, incidence, treatment and prevention of trismus in patients with head and neck cancer.

OBJECTIVE OF REVIEW

Trismus is frequently seen in patients suffering from malignant tumours of the head and neck. The reported prevalence of trismus in those patients varies considerably in the literature and ranges from 0 to 100% depending on the tumour site and extension. Trismus may worsen or remain the same over time, or the symptoms may reduce, even in the absence of treatment. When a patient presents with trismus after tumour treatment, it is important to determine whether the trismus is the result of the treatment, or is the first sign of a recurrence. Restricted mouth opening may impede inspection of the oral cavity as needed for dental care, and particularly for oncologic follow-up.

CONCLUSIONS

Mouth opening after radiotherapy (RT) decreases on average by approximately 20% compared to mouth opening prior to RT. The prevalence of trismus increases with increasing doses of RT to mastication structures. The use of intensity-modulated RT seems to lower the percentage and severity of RT-induced trismus. Treatment of trismus can be conservative (with either medical or physical therapy) or surgical. Exercise therapy is the mainstay of treatment and exercise should start as soon as possible after treatment. The prevention of trismus, rather than its treatment, is the most important objective.

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.

Risk factors and surgical refinements of postresective mandibular reconstruction: a retrospective study

Background. Postresective mandibular reconstruction is common in cases of oral and mandibular tumors. However, complications such as infection, plate exposure, or plate fracture can occur. We identified several significant risk factors of complications after reconstructive surgery and compared the effectiveness of different surgical techniques for reducing the incidence of complications. Methods. This study is a retrospective analysis of 28 oromandibular cancer cases that required reconstructive surgery between January 1999 and December 2011 at Kobe University Graduate School of Medicine in Japan. All cases were classified using Hashikawa's CAT and Eichner's classification methods. Then, we determined whether these classifications and different treatment or surgical methods were significantly related to complications. Results. Complications after mandibular reconstruction occurred in 10/28 patients (36%). Specifically, five patients had plate fractures, four had plate exposures, and one had an infection. Radiation therapy and closure without any flaps were significantly related to infection or plate exposure. The wrap-around technique of securing reconstruction plates was used in 14 cases, whereas the run-through technique was used in two cases. Conclusions. The success of mandibular reconstruction depends on both mechanical and biological factors, such as the location of defects, presence of occlusions, and the amount of vascularization of the flap.

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.

Estimation of dose enhancement to soft tissue due to backscatter radiation near metal interfaces during head and neck radiothearpy - A phantom dosimetric study with radiochromic film

The objective of this study was to investigate the dose enhancement to soft tissue due to backscatter radiation near metal interfaces during head and neck radiotherapy. The influence of titanium-mandibular plate with the screws on radiation dose was tested on four real bones from mandible with the metal and screws fixed. Radiochromic films were used for dosimetry. The bone and metal were inserted through the film at the center symmetrically. This was then placed in a small jig (7 cm × 7 cm × 10 cm) to hold the film vertically straight. The polymer granules (tissue-equivalent) were placed around the film for homogeneous scatter medium. The film was irradiated with 6 MV X-rays for 200 monitor units in Trilogy linear accelerator for 10 cm × 10 cm field size with source to axis distance of 100 cm at 5 cm. A single film was also irradiated without any bone and metal interface for reference data. The absolute dose and the vertical dose profile were measured from the film. There was 10% dose enhancement due to the backscatter radiation just adjacent to the metal-bone interface for all the materials. The extent of the backscatter effect was up to 4 mm. There is significant higher dose enhancement in the soft tissue/skin due to the backscatter radiation from the metallic components in the treatment region.

Biocompatibility and bone formation with porous modified PMMA in normal and irradiated mandibular tissue

A cemented mandibular endoprosthesis is a potentially viable option for mandibular reconstruction after ablative surgery. The commonly used PMMA cement has the inherent weakness of a lack of bioactivity. Improvement by the addition of porosities and bioactive compounds like calcium phosphates may resolve this issue.

OBJECTIVE

The objective of this study was to assess the bone and tissue response to two modified PMMA cements with post-operative radiation as an additional influencing factor.

MATERIALS & METHODS

An in vivo animal study was performed using a mandibular rabbit model. A porous PMMA cement (A) and a porous cement incorporated with Beta-tricalcium phosphate particles (b-TCP) (B) were placed in bilateral mandibular defects with exposed roots and mandibular nerve of 20 animals. Half of the animals underwent additional post-operative radiation.

RESULTS

The animals were healthy with only a minor complication in one rabbit. Temperature analysis showed no significant risk of thermal necrosis with the maximal in vivo cement temperature at 37.8°C. Histology demonstrated: (1) good bone ingrowth around the defect as well as within the pores of the cement and defect bridging was achieved in 70% of the specimens after 12-15 weeks of implantation, (2) no pulpal injury with minor secondary cementum response, (3) an intact mandibular nerve with no inflammation, (4) extensive degradation and resorption of the b-TCP particles by 12-15 weeks, and (5) presence of an intervening thin fibrous tissue at the bone-to-cement interface. Histomorphometrical analysis revealed that there was no difference between the different cements and the presence or absence of post-operative radiation. The 12-15 weeks specimens showed significantly more bone ingrowth and bone maturity than the 4-7 weeks specimens.

CONCLUSION

Both modified PMMA cements have good biocompatibility, bioactivity and support bone ingrowth and additional post-operative radiation did not show any negative effects.

Effects of radiation therapy on craniofacial and dental implants: a review of the literature

OBJECTIVES

The theories of the effects of radiation therapy on craniofacial and dental implants have been challenged by new models. Animal and clinical studies differ on the importance of dose effect and implant location regarding implant survival. Our purpose was to explore the risks of irradiation regarding dose levels, timing of radiation, implant location, and material.

STUDY DESIGN

A systematic search of the literature was performed to identify studies reporting animal and human data on the success of implants in irradiated versus nonirradiated bone.

RESULTS

Eleven animal studies exploring histomorphometric, biomechanical, and histologic features of implants in irradiated bone were summarized. Sixteen human clinical studies evaluating craniofacial (n = 8) and dental (n = 8) implants in irradiated bone were summarized. No meta-analyses of dental implants in irradiated bone were found. Efficacy studies comparing different implant types in irradiated bone were not found.

CONCLUSION

Studies from both animal subjects and human patients indicate that irradiated bone has a greater risk of implant failure than nonirradiated bone. This increase in risk may be up to 12 times greater; however, studies making these comparisons are of poor to moderate quality, so the magnitude of this difference should be accepted with caution.

Reconstruction of large defects postmandibulectomy for oral cancer using plates and myocutaneous flaps: a long-term follow-up

A series of 28 consecutive cases of mandibular reconstruction by means of reconstructive plates and myocutaneous flaps were reviewed. In all cases mandibular resection was indicated for treatment of squamous cell carcinoma of the oral cavity: 25 pelviglossomandibulectomies (resulting in large defects from the angle of the mandible), 2 Commando operations (resulting in lateral defects) and 1 anterior sectional mandibulectomy (resulting in an anterior defect). Tumour stages were T1-T2 (4 cases) and T3-T4 (24 cases). Success was defined as plate maintenance 6 months' postoperatively/postradiotherapy. The overall success rate was 32.2%. Lateral-centre-lateral (L-C-L) defects had 32% success, L (lateral) defects had 50% success and in the single case of a C (centre) defect, the plate was not maintained. Stainless steel reconstruction plates showed a similar success rate as titanium plates (30% versus 34%). In cases not submitted to radiotherapy there were more maintained plates than in cases that received radiotherapy (45.5% versus 23.6%). Reconstruction plates are not effective in bridging large defects of the resected mandible. Only in selected cases that are not eligible for microvascular free flaps should plates and myocutaneous flaps be considered as an option for mandibular reconstruction.

Long-term outcome and factors influencing bridging plates for mandibular reconstruction

Vascularized bone grafts have become the preferred method of mandibular reconstruction. However, the technique is considered to increase both the operating time and blood loss, which might be associated with an increased morbidity and mortality. We conducted a retrospective analysis of 100 consecutive patients who underwent immediate bridging plate reconstruction. The median follow-up duration was 70 months. The 5-year overall survival rate was 69.9%. Cox multivariate analysis revealed that red blood cell transfusion was an independent prognostic factor for the overall survival. The plate survival with no complications was 62.2% at 5 years. Anterolateral defects and preoperative radiotherapy emerged as an independent adverse factor for plate survival. The use of bridging plates is an option for lateral mandibular reconstruction with no preoperative irradiation to avoid the risk from blood transfusion.

Effect of mandibular titanium reconstructive plates on radiation dose

BACKGROUND

The effects of the mandibular titanium alloy plates on the radiation-tissue interactions are not clearly defined. Photon beam radiation may be modified after striking a metal plate used to reconstruct the mandible after oncologic surgery. The purpose of this study was to determine, in a human mandible model, the effects of a titanium alloy plate on the radiation dose received at the bone/titanium (plate and screws) interface and bone/soft tissue interface.

METHODS

We used an adult male human head and neck ex vivo model. A medical grade titanium alloy 6-hole plate, 2.4 mm, was fixed in the midline of the mandible. The mandible was then irradiated using 6 MV photon beams. Thermoluminescent dosimeters were used to measure the radiation doses anterior and posterior to the mandible. The experiment was then repeated without the plate and screws.

RESULTS

The difference between the average doses received by the mandible reconstructed with plate/screws and a mandible without plate/screws was +2.1% at the buccal aspect of the mandible and +3.0% at the lingual aspect; respective P values were.741 and .323. Thus, these differences were not statistically significant.

CONCLUSION

In this study, we did not observe any significant influence of titanium alloy plate/screws on the radiation doses received by tissues anterior or posterior to the mandible.

Effect of metal reconstruction plates on cobalt-60 dose distribution: a predictive formula and clinical implications

PURPOSE

We sought to create a predictive formula for the dose perturbations caused by head and neck reconstruction plates in the delivery of postoperative radiotherapy with 60Co beams.

MATERIALS AND METHODS

The dose perturbation effects of Vitallium and Titanium reconstruction plates and flat metal plates of aluminum (13Al), stainless steel (26Fe), tin (50Sn) and lead (82Pb) irradiated with a 60Co beam were measured in polystyrene phantoms using a film dosimetry system. We then used these results to create formulas to predict the effect of a metal reconstruction plate dependent upon its effective atomic number.

RESULTS

Percentage dose increases secondary to back scattering were 10% at 1 mm in front of the Vitallium plate and 40% at the plate while the percentage dose decrease was 29% at the plate and 10% 1 mm behind the plate. For the Titanium plate, the percentage dose increase was 5% at 1 mm in front the plate and 25% at the plate while the percentage dose decrease was 20% at the plate and 5% 1 mm behind the plate. For flat plates the percentage dose increases and decreases, respectively, at the plate surfaces were: 13Al (8%, 6%), 26Fe (35%, 16%), 50Sn (60%, 24%), and 82Pb (85%, 13%). A second order polynomial predicting the back scatter and shadowing effects was created, Y = a + bZ + cZ2, where Z is the effective atomic number of the plate while a, b, and c are the following constants: for back scatter a = 0.854 +/- 0.082, b = 0.0212 +/- 0.0044, c = -0.00011 +/- 0.00004 and for shadowing a = 1.108 +/- 0.021, b = -0.0141 +/- 0.0011, c = 0.00014 +/- 0.00001.

CONCLUSIONS

It is possible to predict the effect of a metal reconstruction plate upon the delivered postoperative radiotherapy dose. The dose perturbations around the plate only exist for a few millimeters, but this is substantially greater than the thickness of a normal tissue or tumor cell. Perhaps a coating of a low effective atomic number, biologically inert, substance might allow for greater dose homogeneity and decrease the risks of plate failure or tumor recurrence.

An analysis of factors influencing the outcome of postoperative irradiation for squamous cell carcinoma of the oral cavity

PURPOSE

To analyze factors influencing outcome in patients who received postoperative irradiation for advanced squamous cell carcinoma of the oral cavity.

METHODS AND MATERIALS

Between October 1964 and November 1993, 134 patients with 135 previously untreated primary invasive squamous cell carcinomas of the oral cavity (excluding the lip) were treated postoperatively with continuous courses of external-beam irradiation at the University of Florida. All patients had a minimum follow-up of 2 years (analysis, December 1995). No patient was lost to follow-up.

RESULTS

The 10-year actuarial rates of primary site, neck, and local-regional control were 79%, 88%, and 71%, respectively. Recurrence of cancer above the clavicles developed in 35 patients. Ninety-four percent of the recurrences were within the primary field of irradiation (anterior to the plane of the spinal cord); there were 24 recurrences at the primary site and nine in the upper neck alone. There were no failures in the neck area behind the plane of the spinal cord (i.e., the "posterior strip"). Two failures occurred in the low neck below the level of the thyroid notch. In univariate analyses, factors that affected local-regional control included pathologic stage (I-II vs. III-IV, p = 0.04), margin status (invasive cancer at the margin vs. other, p = 0.0007), multifocal tumor (p = 0.05), perineural invasion (p = 0.04), and number of indications for postoperative irradiation (p = 0.05). Extracapsular nodal extension was marginally significant (p = 0.07). In multivariate analysis, positive margins and number of indications remained significant. These factors were used to define relatively favorable (< 4 indications, margins not positive) and unfavorable (> or = 4 indications and/or margins positive for invasive cancer) groups. For both favorable and unfavorable groups, there were nonsignificant trends toward improved local-regional control for patients who began irradiation within 45-50 days, compared with those whose irradiation began later. There were also nonsignificant trends toward improved control for patients treated with shorter overall irradiation treatment courses. An analysis was also performed on the effects of duration of the overall "treatment package" (from the date of surgery until the last day of irradiation). For patients with unfavorable tumors, there was a significantly higher probability of local-regional control for patients whose overall "treatment package" was < or = 100 days (60% vs. 14%, p = 0.04). The 5-year rate of distant metastasis as the sole site of failure was 8% and was predicted by pathologic N stage (N0-N1, 3%; N2-N3, 16%, p = 0.02), as well as the presence (20%) or absence (6%) of extracapsular nodal extension (p = 0.06). The 5-year freedom-from-relapse rate was 63%. The 5-year survival and cause-specific survival rates were 50% and 67%, respectively. Four severe radiation injuries occurred (3%).

CONCLUSION

This paper provides data that define relatively favorable and unfavorable groups of patients in the postoperative setting. Patients with four or more indications for irradiation and/or invasive cancer at the surgical margins have a worse outcome than patients who do not have these negative factors; this is true in spite of the fact that the unfavorable group received higher doses of radiation. Attention should be focused on not only the interval between surgery and irradiation, but also time-dose parameters and the overall duration of the treatment "package."