Primary temporary AO plate reconstruction of the mandible

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.

Pre-contoured reconstruction plate fabricated via three-dimensional printed bending support

A mandibular continuity defect can be repaired using either a prosthetic device or autogenous bone. A titanium reconstruction plate can be used with a localized or vascularized flap over the defect of the mandible. Unfortunately, the plate may fail due to plate exposure, screw loosening, fracture, or infection, and will need to be removed. Plate exposure though the skin or mucosa is one of the main reasons for failure. In the present work, the authors introduced a lingually positioned reconstruction plate fabricated via three-dimensional printed bending support. This custom reconstruction plate can avoid plate re-exposure as well as reduce surgical errors and operation time.

Novel finite element-based plate design for bridging mandibular defects: Reducing mechanical failure

INTRODUCTION

When the application of a free vascularised flap is not possible, a segmental mandibular defect is often reconstructed using a conventional reconstruction plate. Mechanical failure of such reconstructions is mostly caused by plate fracture and screw pull-out. This study aims to develop a reliable, mechanically superior, yet slender patient-specific reconstruction plate that reduces failure due to these causes.

PATIENTS AND METHODS

Eight patients were included in the study. Indications were as follows: fractured reconstruction plate (2), loosened screws (1) and primary reconstruction of a mandibular continuity defect (5). Failed conventional reconstructions were studied using finite element analysis (FEA). A 3D virtual surgical plan (3D-VSP) with a novel patient-specific (PS) titanium plate was developed for each patient. Postoperative CBCT scanning was performed to validate reconstruction accuracy.

RESULTS

All PS plates were placed accurately according to the 3D-VSP. Mean 3D screw entry point deviation was 1.54 mm (SD: 0.85, R: 0.10-3.19), and mean screw angular deviation was 5.76° (SD: 3.27, R: 1.26-16.62). FEA indicated decreased stress and screw pull-out inducing forces. No mechanical failures appeared (mean follow-up: 16 months, R: 7-29).

CONCLUSION

Reconstructing mandibular continuity defects with bookshelf-reconstruction plates with FEA underpinning the design seems to reduce the risk of screw pull-out and plate fractures.

Patient-specific finite element models of the human mandible: Lack of consensus on current set-ups

The use of finite element analysis (FEA) has increased rapidly over the last decennia and has become a popular tool to design implants, osteosynthesis plates and prostheses. With increasing computer capacity and the availability of software applications, it has become easier to employ the FEA. However, there seems to be no consensus on the input variables that should be applied to representative FEA models of the human mandible. This review aims to find a consensus on how to define the representative input factors for a FEA model of the human mandible. A literature search carried out in the PubMed and Embase database resulted in 137 matches. Seven papers were included in this current study. Within the search results, only a few FEA models had been validated. The material properties and FEA approaches varied considerably, and the available validations are not strong enough for a general consensus. Further validations are required, preferably using the same measuring workflow to obtain insight into the broad array of mandibular variations. A lot of work is still required to establish validated FEA settings and to prevent assumptions when it comes to FEA applications.

Clinical Study of Reconstruction Plates Used in the Surgery for Mandibular Discontinuity Defect

BACKGROUND/AIM

Postresective mandibular reconstruction is common in cases of oral and mandibular tumors. However, complications such as plate fracture and/or plate exposure can occur. The purpose of this study was to analyze complications and survival of reconstructive plates used to correct mandibular defects caused by oral cancer.

PATIENTS AND METHODS

Clinical and radiological data from 34 patients were analyzed. Only discontinuous mandibular defect cases were included in this study. All cases were classified using the Hashikawa's CAT and Eichner's classification methods. Then, we determined whether these classifications and clinical treatment methods were significantly related to complications.

RESULTS

Complications after mandibular reconstruction occurred in 10 of 34 patients, specifically, two plate fractures, one screw fracture, and seven plate exposures occurred. The plate fractures occurred 5 and 6 months after operation, and the screw fracture occurred 39 months after operation. Using the Hashikawa's CAT classification, the two cases of plate fracture were one of AT type and the other of T type, and the screw fracture was AT type. Using Eichner's classification, all three cases of plate and screw fractures were B2 type.

CONCLUSION

We suggest that plate and screw fractures were caused by the type of mandibular defect and bite force.

Influence of Backscatter Radiation on Cranial Bone Fixation Devices

Postoperative radiation can cause ulcer formation, leading to the denudation of skin over alloplastic materials. The influence of backscatter radiation from fixation devices has not been investigated. The aim of this study is to evaluate backscatter dose variations for different cranial bone fixation devices in an experimental model designed to simulate postoperative radiotherapy. The authors assessed the radiation backscatter doses associated with resorbable (PLLA-PGA) and titanium plates. The samples were irradiated with 6 and 10 MV photon beams from a linear accelerator. Measurements were obtained using an ionization chamber and radiochromic films cut from the same batch. As a result, the backscatter radiation of water and PLLA-PGA proportionally decreased as the depth increased. However, the backscatter radiation of the titanium plate increased just above the plate. This depth lies in the region of the scalp. Each material showed a dose of radioactivity that was higher at 10 MV than that at 6 MV. These devices showed a significant difference, which suggested that these materials amplified the dose compared with water at 6 MV. In conclusion, it is supposed that PLLA-PGA should be used to fix the cranium to decrease the potential for radiation ulcers.

Mechanical stress in plates for bridging reconstruction mandibular defects and purposes of double plate reinforcement

PURPOSE

To evaluate the biomechanical performance of a commercially available bridging plate (2.4) as well as screws and bone simulating the reconstruction of hemimandibular defects and to indicate alternatives of reinforcement to prevent plate fractures either by strength or fatigue.

MATERIAL AND METHODS

Two common hemimandibular defects are investigated using computed finite element analysis (FEA) approach. Simplified and refined computational models are developed for the geometry of the screw. Conditions of non-locking and locking plate-screw interfaces are considered. Static loads of 120 N are applied. Von Mises stresses and fatigue are calculated. As reinforcement, a second complete or partial plate is placed onto the original plate.

RESULTS

Results demonstrate that reconstruction plates are often subjected to excessive stress that may lead to fracture either by strength or by fatigue. An attached complete or partial second plate is able to reduce stress in the plate, in screws and bone so that stress remains below the allowable limit of the materials.

CONCLUSION

A simplified technique of attaching a whole or sectioned second plate onto the original plate can reduce the stress calculated and may reduce the frequency of plate fractures for the patient's comfort, security and financial savings.

Reconstruction plates used in the surgery for mandibular discontinuity defect

OBJECTIVES

The purpose of this study was to analyze the survival rate of reconstruction plates that were used to correct mandibular discontinuity defects.

MATERIALS AND METHODS

We analyzed clinical and radiological data of 36 patients. Only discontinuous mandibular defect cases were included in the study. Reconstruction plate survival rate was analyzed according to age, gender, location of defect, defect size, and whether the patient underwent a bone graft procedure, coronoidectomy, and/or postoperative radiation therapy (RT).

RESULTS

Plate-related complications developed in 8 patients, 7 of which underwent plate removal. No significant differences were found in plate survival rate according to age, gender, location of defect, defect size, or whether a bone graft procedure was performed. However, there were differences in the plate survival rate that depended on whether the patient underwent coronoidectomy or postoperative RT. In the early stages (9.25±5.10 months), plate fracture was the most common complication, but in the later stages (35.75±17.00 months), screw loosening was the most common complication.

CONCLUSION

It is important to establish the time-related risk of complications such as plate fracture or screw loosening. Coronoidectomy should be considered in most cases to prevent complications. Postoperative RT can affect the survival rate and hazard rate after a reconstruction plate is fitted.

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.

Comparison of Mechanical Stability between Fibular Free Flap Reconstruction versus Locking Mandibular Reconstruction Plate Fixation

Background

The fibular free flap has been used as the standard methods of segmental mandibular reconstruction. The objective of mandibular reconstruction not only includes restored continuity of the mandible but also the recovery of optimal function. This paper emphasizes the advantage of the fibular free flap reconstruction over that of locking mandibular reconstruction plate fixation.

Methods

The hospital charts of all patients (n=20) who had a mandibular reconstruction between 1994 and 2013 were retrospectively reviewed. Eight patients had plate-only fixation of the mandible, and the remaining 12 had vascularized fibular free flap reconstruction. Complications and outcomes were reviewed and compared between the 2 groups via statistical analysis.

Results

Overall complication rates were significantly lower in the fibular flap group (8.3%) than in the plate fixation group (87.5%; p =0.001). Most (7/8) patients in the plate fixation group had experienced plate-related late complications, including plate fracture or exposure. In the fibular flap group, no complications were observed, except for a single case of donor-site wound dehiscence (1/12).

Conclusion

The fibular free flap provides a more stable support and additional soft tissue support for the plate, thereby minimizing the risk of plate-related complications. Fibular free flap is the most reliable option for mandibular reconstruction, and we believe that the flap should be performed primarily whenever possible.

Recent developments of functional scaffolds for craniomaxillofacial bone tissue engineering applications

Autogenous bone grafting remains a gold standard for the reconstruction critical-sized bone defects in the craniomaxillofacial region. Nevertheless, this graft procedure has several disadvantages such as restricted availability, donor-site morbidity, and limitations in regard to fully restoring the complicated three-dimensional structures in the craniomaxillofacial bone. The ultimate goal of craniomaxillofacial bone reconstruction is the regeneration of the physiological bone that simultaneously fulfills both morphological and functional restorations. Developments of tissue engineering in the last two decades have brought such a goal closer to reality. In bone tissue engineering, the scaffolds are fundamental, elemental and mesenchymal stem cells/osteoprogenitor cells and bioactive factors. A variety of scaffolds have been developed and used as spacemakers, biodegradable bone substitutes for transplanting to the new bone, matrices of drug delivery system, or supporting structures enhancing adhesion, proliferation, and matrix production of seeded cells according to the circumstances of the bone defects. However, scaffolds to be clinically completely satisfied have not been developed yet. Development of more functional scaffolds is required to be applied widely to cranio-maxillofacial bone defects. This paper reviews recent trends of scaffolds for crania-maxillofacial bone tissue engineering, including our studies.

Mandibular reconstruction using a poly(L-lactide) mesh combined with autogenous particulate cancellous bone and marrow: a prospective clinical study

The purpose of this study was to evaluate the stability and viability of mandibular bone regeneration using a poly(L-lactide) (PLLA) mesh and autogenous particulate cancellous bone and marrow (PCBM). Sixty-two procedures were undertaken at eight hospitals (22 malignant tumours, 30 benign tumours, five cysts, two osteomyelitis, two trauma, and one atrophy of the alveolar ridge); the success rate was 84%. The follow-up period was between 9 and 200 months (mean 88.2 months). Consequently, bone regeneration at 6 months postoperation was excellent in 35 cases (57%), good in 17 cases (27%), and poor in 10 cases (16%). In six of the 'poor' cases, the PLLA mesh was removed due to local infection early after surgery. Bone resorption>20% was observed in only one of 46 cases with a follow-up term of >1 year. There were no signs of any other adverse effects except in one case where a section of the tray broke off late in the follow-up period. It is concluded that this method is stable and effective due to favourable morphological and functional recovery and low invasiveness. It may thus be a useful alternative procedure for mandibular reconstruction.

The development of a new mandibular osteosynthesis plate: an application of the Ashby approach

Mandible fractures are among the most common bone injuries in facial traumas. Currently, mandibular fracture repair is carried out with an appropriate osteosynthesis plate. These osteosynthesis plates are also used to provide mastication function as soon as possible after operation. Therefore, the plates employed should ensure functional, mechanical, and morphological rehabilitation. Many researchers have reported that the titanium osteosynthesis plates currently used for mandibular defects are often subject to excessive stress. This excessive stress may lead to unexpected fractures of the plates. Unexpected fractures have been indicated as a mechanical weakness of titanium osteosynthesis plates. The aim of the present study is to investigate the mechanical stability and deformation behaviour of commercially available titanium mandibular osteosynthesis plates, as well as to design and develop a new osteosynthesis plate with better mechanical stability. In the first stage of this investigation, an analytical study was carried out to determine the optimum cross-sectional shape for the new plates. Subsequently, the cross-sectional shapes for the new plates were validated by numerical methods. Finally, the project was completed by manufacturing the plates and conducting static mechanical experiments of the developed plates. The mandibular osteosynthesis plates developed here are shown to exhibit improved mechanical stability.

Scope and limitations of methods of mandibular reconstruction: a long-term follow-up

Surgical treatment of cancers of the oral cavity often requires resection of the mandible, which sacrifices continuity, thereby implying considerable loss of function and aesthetics. The aim of the present study was to compare different methods of mandibular reconstruction for long-term results, complications, and factors associated with failure. During the 10-year period (1995-2005), 102 patients (73 men and 29 women, mean age 55 years, range 11-83) had a continuity resection of the mandible as described by Jewer et al. as follows: lateral continuity defect (n=53), central/lateral continuity defect (n=24), lateral/central/lateral continuity defect (n=14), central continuity defect (n=6), hemimandibular continuity defect (n=4) and central/hemimandibular continuity defect (n=1). The gap in the mandible was bridged with a titanium reconstruction plate in 73 patients, four of whom required a temporomandibular joint prosthesis. In 29 patients the mandibles were reconstructed with free autologous bone grafts fixed with miniplates. The overall 1-year success rate was 64%; 66% for the 73 patients who had miniplate/bone fixation and 63% in the 29 whose defects were bridged with a reconstruction plate. Complications were associated with the reconstruction plate in 39%. The most common complications were extraoral exposure (16%), intraoral exposure (10%), loose osteosynthesis screws (5%), fractures of the reconstruction plate (5%), and extra/intraoral exposure (1%). All fractures were noted at least 6 months postoperatively. There was no increased risk (p=0.67) depending on the osteosynthesis device used (miniplate or reconstruction plate). The risk of failure of the reconstruction plate was significantly higher in men (p=0.002) and smokers (p=0.004), whereas no increased risk was apparent for the anatomical site of the defect. Radiation reduced the 1-year success rate from 64% to 45% but not significantly so (p=0.67). There were no significant differences between the reconstruction methods. Alloplastic reconstruction devices are the treatment of choice for many patients.

Reconstruction of head and neck defects: a systematic approach to treatment

Reconstruction of composite maxillofacial defects after tumor excision or trauma is difficult. The role of the reconstructive surgeon is to have a diverse armamentarium of reconstructive options to enable an aesthetic and functional reconstruction while minimizing the morbidity to the patient. This article will present a systematic review of composite maxillofacial reconstruction with free tissue transfer.

Biomechanical testing of different osteosynthesis systems for segmental resection of the mandible

PURPOSE

This investigation assessed the mechanical behavior of 3 different locking and nonlocking reconstruction systems-Unilock 2.4, Reconstruction 2.4, and Reconstruction 2.7-with regard to plate and screw fracture.

MATERIALS AND METHODS

Five different plate/screw configurations (Unilock 2.4-locking screws, Unilock 2.4 -conventional screws, Reconstruction 2.4-conventional screws, Reconstruction 2.7-conventional screws, and Unilock 2.4-locking screws with a 1-mm gap; Synthes, Umkirch, Germany) were tested on synthetic mandibles. All mandibles were resected on the left side between the canine and third molar, reconstructed, and loaded cyclically between 30 and 300 N up to 250,000 cycles or until screw or plate failure occurred.

RESULTS

No screw fractures were observed. All plates fractured close to the distal fragment. The Unilock plates fixed with locking screws withstood significantly more cycles until failure than the Reconstruction plates 2.4 fixed with conventional MF-Cortex screws. No significant differences were found in the other groups. Only 2 of the 34 plates tested, both of the Reconstruction 2.7 system, reached the runout limit.

CONCLUSIONS

Unilock plates fixed with locking screws have a higher long-term stability than the Reconstruction 2.4 system. A 1-mm gap between the plate and mandible does not lead to early screw failure in the Unilock 2.4 system with locking screws. The Reconstruction 2.7 system seems superior if well contoured, because 2 of those plates reached the runout limit; however, this system is not as easy to handle as the 2.4 systems, and good contouring is difficult to achieve. Therefore, we consider the Unilock 2.4 system with locking screws the best choice.

Fracture of titanium plates used for mandibular reconstruction following ablative tumor surgery

PURPOSE

The purpose of this study was to identify reasons for fracture of titanium mandibular reconstruction plates, when used to bridge lateral mandibular defects after ablative tumor surgery.

MATERIALS AND METHODS

Sixteen titanium reconstruction plates from sheep mandibles were examined to identify reasons for the plate fractures. The broken plates and the seemingly unbroken plates were examined separately. The plates were removed from the mandibular bone and inspected by dye penetrant examination, metallography, optical microscope, scanning electron microscope, and energy dispersive X-ray spectrometer. Furthermore, axial load fatigue tests were performed in two different environments, air and physiologic salt solution, 0.9% NaCl, to compare titanium behavior in air and the human body.

RESULTS

The site of crack initiation was the inner curvature of the reconstruction plate, and the cracks initiated as a result of stress concentration in the shoulder fillet of the plate. The cracks grew in a cyclic manner under masticatory loading of the mandible and the plate. The plate fracture occurred by means of fatigue. The corrosive environment did not affect the failure of the titanium plate, and the fracture was not caused by hydrogen embrittlement. The results revealed that the fatigue properties of the plates may have been impaired by the residual stresses generated in plate bending.

CONCLUSIONS

Adjustive bending of the plates, in the surgical operation, may thus be an important cause of fracture of the reconstruction plates, because of generated residual stresses, which affect the mean stress in fatigue loading. To make the plates function without failure the plates should match closely with the three-dimensional shape of the mandible, to avoid any bending in the operative phase.

Bridging mandibular continuity defects with miniplates: an experimental study

Various miniplate fixation techniques were studied in dogs to determine whether the use of miniplate fixation provides sufficient stability in mandibular continuity defects. Continuity resections measuring 15 mm were made on the mandibles of 16 dogs and were bridged using 4 miniplate fixation techniques, each replicated 4 times. All dogs were placed on a normal diet throughout the postoperative period. Clinical and radiological examinations were carried out 6 weeks later. We found that the group with both double miniplates and bicortical screws was stable, whereas the groups utilizing either a single miniplate or monocortical screws were not. The results of this study indicate that using a combination of double miniplates and bicortical screws to bridge defects after mandibular resection produces stable and predictable results.

Analysis of mechanical stress in reconstruction plates for bridging mandibular angle defects

INTRODUCTION

The objective of the present study was to evaluate the mechanical stress in reconstruction plates and the screw-plate-bone interface used in bridging a mandibular angle defect by means of the finite element method (FEM). The influence of plate geometry as well as the configuration and the diameter of the screws on the mechanical stress distribution was to be determined at the same time and was used as the basis for developing suggestions to optimize the design of the reconstruction plates.

MATERIAL

Based on the geometrical data of a human mandible, an angle defect bridged by a titanium reconstruction plate was generated and exposed to chewing force. First a reconstruction plate was tightly fixed with M2.7 titanium screws. Then, plate design, screw configuration and screw diameter were varied. The mechanical stress was calculated according to von Mises stress hypothesis.

RESULTS

In the standard reconstruction plate, the result of the finite element analysis revealed stress resulting from the simulated functional loadings which far exceeded the strengths of the components. Possible clinical consequences could be a fatigue fracture of the plate itself, gradual loosening of the osteosynthesis screws and loss of bone. The stress can be reduced to less than half by increasing the diameter of the screw threads 1.5 fold.

CONCLUSION

Maximizing the interface between bone and reconstruction plate had a favourable effect. As a consequence of the large interface and a triangular or square configuration of the screws, the stresses could be substantially reduced, the plate could be made thinner and thus better adapted to the mandible. As a preliminary result, the newly designed reconstruction plate could be thinned in areas subject to less mechanical stress.

Computergestützte Kaukraftanalyse bei Patienten mit Unterkieferkontinuitätsresektionen

BACKGROUND

Surgical treatment of tumors of the oral cavity often requires a segmental resection of the mandible. This always implies a considerable loss in function and aesthetics. The aim of the present study was to measure the chewing force obtained by patients after mandibular resection.

PATIENTS AND METHODS

In a group of 20 patients (twelve males, eight females, average age 59 years), chewing force were registered by means of a computerized measurement device. In 16 patients, the defect was bridged by a reconstruction plate, in three with an iliac bone graft stabilized by miniplates, and in one patient with only two miniplates.

RESULTS

The maximum value in the molar region was 186 N und the minimum was 28 N. The average bite force in the molar region reached 81.1 N (+/-46.1) with 42.9 N (+/-35.7) in the front region. The highest value was registered in a patient with an iliac bone graft without soft tissue defect. The lowest was found in patients with bony chin defects.

CONCLUSION

Based on these results, a reduction of 76% in the molar region and 59% in the incisor region was observed. These values might be helpful in providing a more realistic definition of the functional loadings found in patients after mandibular resection, which in turn may help in the development of new reconstruction devices.

[On the indications for and morbidity of segmental resection of the mandible for squamous cell carcinoma in the lower oral cavity]

BACKGROUND

Segmental resection of the mandibula in oral cancer surgery leads to both functional and aesthetic problems. The decision to preserve or resect the mandible depends on the vicinity of the lesion to the bone. Consequently, based on the rules of safety margins to all planes that are recommended for soft tissues, each lesion that is closer than 10 mm to the mandible needs resection of the bone.

PATIENTS AND METHODS

To establish data-based treatment modalities, a retrospective study was initiated and the results from all preoperative staging investigations of 152 patients with intraoral squamous cell carcinoma who underwent continuity or marginal resection of the mandible were evaluated. The histological outcome of the resected bone was compared to the staging results. Functional rehabilitation and long-term follow-up including survival rates were evaluated. The study reports on typical complications following segmental resection such as fracture of the reconstruction plate and demonstrates experiences with secondary microsurgical reconstructive surgery.

RESULTS

Mainly in cases of stage T1 and T2 carcinomas which are closer than 10 mm to the bone and clinically do not show any infiltration to the mandible, a marginal resection seems to be adequate. The decision about the extension of mandibular resection can be based on intraoperative cross sectional investigation of the periosteum. The survival rate of patients with intraoral carcinomas close to the mandible who underwent marginal mandibulectomy seems to be the same as in cases of continuity resection. A more conservative management of mandibular resection seems to be adequate and a data-based concept to standardize therapy of mandibular resection is presented.

Postoperative Radiotherapy After Titanium Plate Mandibular Reconstruction for Oral Cavity Cancer

OBJECTIVE

To study the impact of postoperative radiotherapy (RT) on titanium plate mandibular reconstruction.

METHODS

Between 1997 and 2002, 66 patients with oral cavity cancers had immediate titanium plate mandibular reconstruction. Thirty-four patients (51.5%) received postoperative RT and 32 patients were treated with surgery alone. Follow-up ranged from 12 to 58 months (median, 24 months).

RESULTS

Sixteen of 66 patients (24.2%) had major complications. Ten of 34 patients (29.4%) who received RT had complications compared with 6 of 32 patients (18.8%) after surgery alone (P = 0.312). The plate was removed in 11 patients (16.7%). The success rate of titanium plate reconstruction was 27 of 34 patients (79.4%) who received RT and 28 of 32 patients (87.5%) after surgery alone (P = 0.378).

CONCLUSION

The addition of postoperative RT did not increase the risk of complications or the likelihood of successful titanium plate 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.

Material analysis of AO plate fracture cases

PURPOSE

The clinical observation of fracture cases and material evaluation of fractured titanium plates were performed to investigate the causes of fracture.

PATIENTS AND METHODS

Fracture of titanium plates occurred in 4 patients of the 110 mandibular reconstructions. We clinically and experimentally evaluated plate fracture cases among cases in which primary reconstruction using titanium plates was performed after the mandibular resection.

RESULTS

Titanium plate fracture was frequently observed in L-type defect cases in which angle-type plates were used, and fracture mainly occurred in the anterior region of the mandibular angle. Material analysis suggested that the occurrence of fracture can be prevented by eliminating constricted parts on the internal side of the plates.

CONCLUSIONS

The causes of fracture were thought to be the use of plates under the conditions of comparatively frequent repeated application of stress or fatigue fracture caused by stress concentration, depending on the form of the plate.

Comparative study of locking plates in mandibular reconstruction after ablative tumor surgery: THORP versus UniLOCK system

PURPOSE

This retrospective study compared 2 types of rigid locking plates (THORP and UniLOCK; Stratec Medical, Oberdorf, Switzerland) in 107 patients undergoing reconstruction for bridging mandibular defects following ablative tumor surgery.

PATIENTS AND METHODS

From January 1993 to December 2000, 107 patients were reconstructed following ablative tumor surgery with 57 THORP plates and 50 UniLOCK plates. Study follow-up ranged from 18 to 87 months (average, 32 months). Complications were categorized into delayed wound healing, infection, plate exposure, and plate fracture, taking into account the type and timing of reconstruction.

RESULTS

Overall type and number of complications show no statistically significant differences between THORP and UniLOCK groups. Infection was the most frequent type of complication (THORP, 30; UniLOCK, 32). Others included delayed wound healing (THORP, 13; UniLOCK, 12), plate exposure (THORP, 8; UniLOCK, 7), and plate fracture (THORP, 5; UniLOCK, 1). Plates were removed in 22 THORP and 11 UniLOCK plates. The most frequent reason for plate removal in both groups was infection. Other reasons for plate removal include tumor recurrence, plate fracture, plate exposure, or a combination of reasons.

CONCLUSIONS

THORP and UniLOCK plates do not present statistically significant differences in the parameters studied. Nevertheless, the UniLOCK group had slightly better results. Considering that the THORP system is much bulkier and its screws bigger, our results lead to the conclusion that bridging osteosynthesis with a 2.4 UniLOCK system is adequate for plate reconstruction of mandibular defects.

Use of Kirschner wire in mandible reconstruction: a case report and review of the literature

Reconstruction of massive defects in head the and neck usually requires different tissues such as skin, bone, and muscle in three-dimensional organization. Therefore, reconstruction of mandibular defects in particular include many difficulties for the head and neck, and for reconstructive surgeons. Various techniques and materials are available, and each has some advantages and disadvantages. But no materials or methods have all the reconstructive requirements. The surgeon's choice of techniques should be safe, simple, economic, and effective. We present a patient with a massive facial defect that was reconstructed successfully by using a 2-mm K wire with a free transverse rectus abdominis myocutaneous flap, and we also review the literature about the use of K wires in mandible fixation and reconstruction. We think that K wires should be kept in mind as a readily available, easily applicable, safe, inexpensive, and stable prosthetic material for mandible reconstruction, especially in cases with advanced disease.

Fracture of mandibular reconstruction plates used after tumor resection

PURPOSE

We assessed the incidence of fractured plates after primary temporary AO plate reconstruction of the mandible following tumor resection.

PATIENTS AND METHODS

One hundred ten patients were retrospectively evaluated according to the extent of the tumor, anatomic location of the reconstruction, type of plate, additional use of radiotherapy or flap surgery (or both), and the incidence of fractured plates.

RESULTS

Fractured plates occurred in 8 of 110 patients. Most occurred less than 6 months after surgery. All of the 8 patients had a malignant tumor; 2 had received radiation therapy and 4 had skin flaps placed. The fractured plate was the straight type in 1 patient and the angular type in 7 patients. Among patients who had fractured plates, the average number of remaining teeth was 12.8 in the maxilla and 9.5 in the mandible.

CONCLUSIONS

Fractured plates were more common among patients with oral cancer with a segmental defect that did not cross the midline in whom an angular-type plate was used and no bone grafting was performed.

A comparative study on four screw-plate locking systems in sheep: a clinical and radiological study

Four mandibular screw-plate locking systems were studied in sheep. Three to four centimetres angular continuity resections of the mandible were performed and the defects bridged with pre-bent angular reconstruction plates fixed with four screws in the body part and three in the ramus. Each type was used four times. Clinical and radiological examinations were carried out 1 and 2 months later. All sheep were able to eat and ruminate normally throughout the postoperative period. Radiology revealed that 6/16 plates and 5/112 screws fractured during the follow-up period. In one type, no fracture occurred. Screw fracture was confined to just one reconstruction system. Six of 16 mandibles showed slight to moderate bone resorption under the plate. The results point to the internal shortcomings of the systems tested.

Tratamento cirúrgico do ameloblastoma com reconstrução de mandíbula com enxerto de crista ilíaca não vascularizado: estudo de sete casos

OBJETIVO: Determinar a validade do enxerto autólogo de crista ilíaca não vascularizado no tratamento cirúrgico do ameloblastoma de mandíbula. MÉTODO: Nos Serviços de Cirurgia de Cabeça e Pescoço e Semiologia Bucal do Complexo Hospitalar Heliópolis, de 1980 a 2000, foram tratados 31 pacientes com ameloblastoma de mandíbula, dos quais sete receberam enxerto de crista ilíaca autólogo, fixos com placa de titânio do sistema A-0 (quatro casos) e aço inox (três casos), sendo portadores da variedade folicular (seis casos) e plexiforme (um caso). RESULTADOS: Nesta análise, foi utilizado o Teste de Hipótese para a média populacional com a variança desconhecida, houve exposição da placa em três casos (40%) quando a neoplasia ultrapassava a linha média e em quatro casos (60%) não incidiu nenhuma complicação. CONCLUSÕES: Apesar da incidência de exposição de placa, o método é indicado na reconstrução da mandíbula de pacientes com ameloblastoma.