Experience with AO reconstruction plates after partial mandibular resection involving its continuity

Parameter optimization in a finite element mandibular fracture fixation model using the design of experiments approach

Only a few mandibular bone finite element (FE) models have been validated in literature, making it difficult to assess the credibility of the models. In a comparative study between FE models and biomechanical experiments using a synthetic polyamide 12 (PA12) mandible model, we investigate how material properties and boundary conditions affect the FE model's accuracy using the design of experiments approach. Multiple FE parameters, such as contact definitions and the materials' elastic and plastic deformation characteristics, were systematically analyzed for an intact mandibular model and transferred to the fracture fixation model. In a second step, the contact definitions for the titanium screw and implant (S-I), implant and PA12 mandible (I-M), and interfragmentary (IF) PA12 segments were optimized. Comparing simulated deformations (from 0 to -5 mm) and reaction forces (from 10 to 1'415 N) with experimental results showed a strong sensitivity to FE mechanical properties and contact definitions. The results suggest that using the bonded definition for the screw-implant contact of the fracture plate is ineffective. The contact friction parameter set with the highest agreement was identified: titanium screw and implant μ = 0.2, implant and PA12 mandible μ = 0.2, interfragmentary PA12 mandible μ = 0.1. The simulated reaction force (RMSE = 26.60 N) and surface displacement data (RMSE = 0.19 mm) of the FE analysis showed a strong agreement with the experimental biomechanical data. The results were generated through parameter optimization which means that our findings need to be validated in the event of a new dataset with deviating anatomy. Conclusively, the predictive capability of the FE model can be improved by FE model calibration through experimental testing. Validated preoperative quasi-static FE analysis could allow engineers and surgeons to accurately estimate how the implant's choice and placement suit the patient's biomechanical needs.

The Value of Three-Dimensional Modeling on Repositioning and Soft Tissue Filling in Microsurgical Reconstruction of Secondary Mandibular Defects: A Retrospective Study

Purpose

Secondary mandibular defect reconstruction is a challenging operation. It is performed rather rarely, as in most of the cases a primary reconstruction is preferable. Restoration of function and symmetry, in secondary reconstruction of mandibular defects, requires accurate repositioning of segments and appropriate soft tissue filling. The purpose of this study is to estimate the value of three-dimensional (3D) digital modeling to meet the above requirements, in secondary microsurgical reconstruction of mandibular defects.

Methods

Five cases of mandibular defects, with various degrees of asymmetry and dysfunction, were restored secondarily, with fibula flaps, after virtual reconstruction on a 3D model derived from their computed tomography, with the utilization of CAD-CAM software. Software reproduced symmetrical 3D models by mirroring the healthy side. Occlusion was restored by fine adjustments on 3D models and finally a reconstruction plate was pre-bent on them, prior to its sterilization for use in surgery. Three out of the five cases received an osteo-cutaneous flap, while in the other two patients, an osseous flap was used. Lower face symmetry, mouth opening, and main patient’s complaints were evaluated pre- and postoperatively to assess the value of the 3D modeling.

Results

All flaps survived. Hematoma occurred in two patients and was resolved after evacuation. In two patients, a fistula observed, was attributed to screw loosening, and treated after a surgical debridement and screw replacement. Intraoral exposure in the posterior part of the fibula flap was recorded in one patient, possibly from wound dehiscence due to tension of the intraoral tissue, and successfully covered with an ipsilateral nasolabial flap. The resulting symmetry and function were satisfactory in all the patients.

Conclusion

Secondary mandibular defects are often related with cosmetic disfigurement, misalignment of mandibular segments, and mandibular malfunction. For the correction of mandibular continuity, symmetry, and restoration of function, preoperative 3D modeling may be an important tool, according to our results.

Biomechanical In Vitro Study on the Stability of Patient-Specific CAD/CAM Mandibular Reconstruction Plates: A Comparison Between Selective Laser Melted, Milled, and Hand-Bent Plates

Study Design

An experimental in vitro study.

Objective

Plate fractures are a recurrent problem in alloplastic mandibular reconstruction. Hypothetically it can be assumed that computer-aided design (CAD)/computer-aided manufacturing (CAM) reconstruction plates have a higher stability than conventional hand-bent plates. The aim of the study was to compare additive and subtractive fabricated CAD/CAM mandibular reconstruction plates as well as conventional plates with regard to their biomechanical properties.

Methods

In a chewing simulator, plates of 2 conventional locking plate systems and 2 CAD/CAM-fabricated plate systems were compared. The plates were loaded in a fatigue test. The maximum number of cycles until plate fracture and the plate stiffness were compared.

Results

While all conventional plates fractured at a maximum load between 150 and 210 N (Newton) after a number of cycles between 40 000 and 643 000, none of the CAD/CAM plates broke despite a nearly doubled load of 330 N and 2 million cycles. Both CAD/CAM systems proved to be significantly superior to the hand-bent plates. There was no difference between the 2 CAD/CAM systems.

Conclusions

Concerning the risk of plate fracture, patient-specific CAD/CAM reconstruction plates appear to have a significant advantage over conventional hand-bent plates in alloplastic mandibular reconstruction.

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.

Nonvascularized Iliac Bone Reconstruction for the Mandible Without Maxillofacial Skin Scarring

PURPOSE

There are many methods to reconstruct the mandible, but they are often accompanied by trauma, which can lead to scarring of the maxillofacial skin. The purpose of this study was to show the utility of a minimally invasive method for reconstruction of the mandible with nonvascularized iliac bone grafts without a skin scar, as well as to evaluate the success rate and complications.

PATIENTS AND METHODS

This was a retrospective case series. We retrospectively analyzed patients who underwent transoral resection of benign mandibular pathologies, followed by nonvascularized iliac bone graft reconstruction. The primary outcome variable was the success rate of the bone grafts. Secondary outcome variables were postoperative complications at the grafted bone recipient and donor sites, the long-term absorptivity of grafted bone, and the type of mandibular defect. We computed descriptive statistics or performed the χ² test for each variable.

RESULTS

Overall, 54 patients were included in the study, including 21 male and 33 female patients, with an age range of 10 to 65 years. The complete survival rate was 87.0% (47 of 54 patients), and the partial survival rate was 98.1% (53 of 54). The average bone absorption rate 3 years after surgery was 1.8 to 30.7%. We propose a new classification method for mandibular defects based on the extent of the tumor, location of the osteotomy, and degree of surgical difficulty.

CONCLUSIONS

Intraoral nonvascularized iliac bone grafting is a highly successful minimally invasive method for mandibular reconstruction. It is also one of the best methods for mandibular reconstruction in patients with benign mandibular tumors without soft tissue involvement.

Salvage Secondary Reconstruction of the Mandible with Vascularized Fibula Flap

Primary restoration of the mandibular continuity remains the standard of care for defects, and yet several constraints preclude this objective. Interim reconstructions with plate and nonvascular bone grafts have high failure rates. The secondary reconstruction, when becomes inevitable, remains a formidable task. This retrospective study evaluates various issues to address secondary reconstruction. Twenty-one patients following mandibulectomy presented with various complications between 2012 and 2016 were included in the study. The profile of primary reconstruction includes reconstruction plate ( n  = 9), reconstruction plate with rib graft ( n  = 3), soft tissue only reconstruction ( n  = 4), free fibula ( n  = 2), inadequate growth of reconstructed free fibula during adolescence ( n  = 1), nonvascular bone graft alone ( n  = 1), and no reconstruction ( n  = 1). All had problems or complications related to unsatisfactory primary reconstruction such as plate fracture, recurrent infection, plate exposure, deformity, malocclusion, and failed fibula reconstruction. All were reconstructed with osteocutaneous free fibula flap with repair of soft-tissue loss. All flaps survived and had satisfactory outcome functionally and aesthetically. Dental rehabilitation was done in four patients. One flap was reexplored for thrombosis and salvaged. The challenges in secondary reconstruction include difficulty in recreating true defects, extensive fibrosis and loss of planes, unanticipated soft-tissue and skeletal defects, reestablishing the contour and occlusion, insufficient bone strength, dearth of suitable recipient vessels, nonpliable skin, tissue contraction to accommodate new mandible, need of additional flap for defect closure, and postirradiation effects. Notwithstanding them, the reasonable successful outcome can be attainable.

Infantile myofibromatosis treated by mandibulectomy and staged reconstruction with submental flap and free fibula flap: a case report

BACKGROUND

Infantile myofibromatosis is the most common benign fibrous tumor in infants. Three different types have been reported in the literature. The most commonly affected areas are the head, the neck and the trunk. Our patient showed a very high level of mandibular destruction resistant to all mandibular sparing treatment strategies requiring segmental mandibulectomy and complex reconstruction.

CASE PRESENTATION

We describe a rare case of multicentric infantile myofibromatosis with mandibular bone destruction. The treatment required a succession of chemotherapy, a subtotal transoral resection and a hemi-mandibulectomy. The mandibular reconstruction was staged with initial bridging titanium plate with a submental flap, followed later by a fibula free flap.

CONCLUSION

Mandibular involvement by myofibromatosis is rare, and the extend of bone destruction and reconstruction make this case unique. To our knowledge, this is the only reported case of fibula free flap mandibular reconstruction in a patient with infantile myofibromatosis , as well as one of the youngest reported submental island flaps for any pathology. We describe the clinical presentation and management, including relevant imaging, histopathology, medical and surgical treatment as well as a review of relevant literature.

The fitting accuracy of pre-bend reconstruction plates and their impact on the temporomandibular joint

BACKGROUND

Various causes for bone defects of the lower jaw have been described. As a result, patients often suffer from compromised aesthetics and a loss of, or reduction in, important physiological functions, such as swallowing, breathing, and speaking. A change in the shape of the lower jaw can impair the natural occlusion and leads to an atypical or modified position of the temporomandibular joint. Titanium reconstruction plates are the standard approach to jaw reconstruction, and are used for temporary bridging of a jaw defect or fixation of a bone graft. Conventionally these plates are intraoperatively adjusted to the mandible by the surgeon. Computer-aided manufacturing, computer-aided design, and rapid prototyping have gained increasing importance in the field of medicine, as they allow the production of individual models of the lower jaw, with the possibility of preoperatively bending the reconstruction plates. In this retrospective study, the accuracy of pre-bent titanium plates and their effect on the temporomandibular joint situation in comparison with intraoperatively curved plates will be discussed.

MATERIALS AND METHODS

Patients who attended our department for lower jaw reconstruction between March 2013 and February 2015 were included in this retrospective study. Within that time 20 patients were treated with pre-bent reconstruction plates (group 1). 20 comparable patients were selected with reconstruction and conventional intraoperative bending (group 2). To evaluate the accuracy of the plates and the condylar position, postoperative cone beam computed tomograms and computed tomograms were used to assess the bone-plate distance at 12 defined points and four angles in axial reconstruction. The results were compared, statistically evaluated, and discussed.

RESULTS

Regarding the maximum bone-plate distances and the sum of distances, there was a significant difference between the accuracy of the pre-bent and the conventionally bent reconstruction plates (p = 0.022, p = 0.048). Regarding the condylar position, there was no significant difference between both methods (p = 0.867).

CONCLUSION

The results of this study show that a better fitting accuracy can be achieved using pre-bent plates. Preparation of the plates proves to be advantageous and meaningful, especially in complex bone defects and deformations of the lower jaw. Nevertheless, concerning the position of the temporomandibular joint, no significant difference could be ascertained between the shown methods, contradicting several studies.

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.

The Epidemiology, treatment, and complication of ameloblastoma in East-Indonesia: 6 years retrospective study

Background

Ameloblastoma is a neoplasm classified as a benign epithelial odontogenic tumor of the jaws, grow slowly and are locally invasive. The aim of the present study was to investigate the incidence, treatment, and complication of patients with ameloblastoma in East-Indonesia during six years retrospective study.

Material and Methods

This retrospective study included 84 patients who were diagnosed with ameloblastoma from 2011 to 2016. There were 56 patients with treatment data available. Data from each patient, including gender, age, histologic type, the size of the tumor, radiologic form, tumor location, type of treatment, and complication were reviewed and analyzed retrospectively.

Results

Fourteen patients were diagnosed with unicystic ameloblastoma (25%), thirty two patients with multicystic follicular ameloblastoma (57%) and ten patients with an unspecified multicystic ameloblastoma (18%). A total of about 35 patients were treated conservatively (62.5%) and 21 patients were treated radically (37.5%). Swelling was present as a pre-operative complication in all 56 cases (100%). There were no complaints concerning speech.

Conclusions

The majority findings of the histologic type were multicystic ameloblastoma and their location were in the mandible. Most ameloblastoma were treated conservatively and reconstructions were made with only titanium plates and not bone graft.

Key words:Ameloblastoma, epidemiology, east Indonesia.

Reconstruction of the bony chin using sagittal split osteotomies of the remaining mandible - A new technique for a special indication: Case report

There are several indications for resecting the bony chin, such as squamous cell carcinoma, sarcoma, or benign tumors of the jaw such as ameloblastoma. Several techniques for reconstruction of the bony chin, such as the use of metal plates and also revascularized free bone grafts of the iliac crest, fibula, or scapula, are common. In the case of poor vascular supply, however, alternative techniques may be necessary. In this report, a new technique is described using pedicled bone flaps from both sagittally split mandibular stumps following chin resection. These flaps were pedicled on the mylohyoid muscles and advanced to restore the continuity of the mandible. An advantage of this procedure was minimization of the soft tissue defect, making repair easier. Morbidity of the resection and reconstruction was thus reduced, and recovery of the patient was very quick.

Hardware Removal in Craniomaxillofacial Trauma: A Systematic Review of the Literature and Management Algorithm

Background

Craniomaxillofacial (CMF) fractures are typically treated with open reduction and internal fixation. Open reduction and internal fixation can be complicated by hardware exposure or infection. The literature often does not differentiate between these 2 entities; so for this study, we have considered all hardware exposures as hardware infections. Approximately 5% of adults with CMF trauma are thought to develop hardware infections. Management consists of either removing the hardware versus leaving it in situ. The optimal approach has not been investigated. Thus, a systematic review of the literature was undertaken and a resultant evidence-based approach to the treatment and management of CMF hardware infections was devised.

Materials and Methods

A comprehensive search of journal articles was performed in parallel using MEDLINE, Web of Science, and ScienceDirect electronic databases. Keywords and phrases used were maxillofacial injuries; facial bones; wounds and injuries; fracture fixation, internal; wound infection; and infection. Our search yielded 529 articles. To focus on CMF fractures with hardware infections, the full text of English-language articles was reviewed to identify articles focusing on the evaluation and management of infected hardware in CMF trauma. Each article’s reference list was manually reviewed and citation analysis performed to identify articles missed by the search strategy. There were 259 articles that met the full inclusion criteria and form the basis of this systematic review. The articles were rated based on the level of evidence. There were 81 grade II articles included in the meta-analysis.

Result

Our meta-analysis revealed that 7503 patients were treated with hardware for CMF fractures in the 81 grade II articles. Hardware infection occurred in 510 (6.8%) of these patients. Of those infections, hardware removal occurred in 264 (51.8%) patients; hardware was left in place in 166 (32.6%) patients; and in 80 (15.6%) cases, there was no report as to hardware management. Finally, our review revealed that there were no reported differences in outcomes between groups.

Conclusions

Management of CMF hardware infections should be performed in a sequential and consistent manner to optimize outcome. An evidence-based algorithm for management of CMF hardware infections based on this critical review of the literature is presented and discussed.

Mandible reconstruction: History, state of the art and persistent problems

BACKGROUND

Mandibular reconstruction has been experiencing an amazing evolution. Several different approaches are used to reconstruct this bone and therefore have a fundamental role in the recovery of oral functions.

OBJECTIVES

This review aims to highlight the persistent problems associated with the approaches identified, whether bone grafts or prosthetic devices are used. A brief summary of the historical evolution of the surgical procedures is presented, as well as an insight into possible future pathways.

STUDY DESIGN

A literature review was conducted from September to December 2012 using the PubMed database. The keyword used was "mandible reconstruction." Articles published in the last three years were included as well as the relevant references from those articles and the "historical articles" were referred. This research resulted in a monograph that this article aims to summarize.

RESULTS

Titanium plates, bone grafts, pediculate flaps, free osteomyocutaneous flaps, rapid prototyping, and tissue engineering strategies are some of the identified possibilities. The classical approaches present considerable associated morbidity donor-site-related problems.

CONCLUSION

Research that results in the development of new prosthetics devices is needed. A new prosthetic approach could minimize the identified problems and offer the patients more predictable, affordable, and comfortable solutions.

CLINICAL RELEVANCE

This review, while affirming the evolution and the good results found with the actual approaches, emphasizes the negative aspects that still subsist. Thus, it shows that mandible reconstruction is not a closed issue. On the contrary, it remains as a research field where new findings could have a direct positive impact on patients' life quality. The identification of the persistent problems reveals the characteristics to be considered in a new prosthetic device. This could overcome the current difficulties and result in more comfortable solutions. Medical teams have the responsibility to keep patients informed about the predictable problems related with each elected approach, even understanding that a perfect reconstruction is a secondary goal when compared with maintenance of life.

Reconstruction of osteomyelitis defects of the craniofacial skeleton

Osteomyelitis of the craniofacial skeleton closely resembles osteomyelitis elsewhere in the body in its pathophysiology and medical management; subsequent reconstruction after debridement remains distinctly challenging. The goals of reconstruction must include the restoration of the complex and readily visible morphology of the cranium and face, as well as the adequate return of vital sensory, expressive, and digestive functions. In this article, the various reconstructive modalities will be discussed including pedicled and nonpedicled flaps with or without an osseous component, nonvascularized bone grafts, alloplastic implants, and bone regeneration using protein therapy. Although reconstruction of craniofacial defects after osteomyelitis commonly proves formidable, the satisfactory return of form and function remains a plausible reconstructive goal.

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.

Increased plate and osteosynthesis related complications associated with postoperative concurrent chemoradiotherapy in oral cancer

BACKGROUND

Plate osteosynthesis is a widely used technique in head and neck reconstructive surgery. The objective of this study was to determine whether postoperative chemoradiotherapy, which was recently introduced for high-risk head and neck cancer, affects plate and osteosynthesis related complications.

METHODS

Fifty-two consecutive patients, who had undergone plate osteosynthesis for mandibular reconstruction between October 2003 and September 2006, were included in the study. The patients were divided into 3 groups: (1) surgery alone (n = 19), (2) surgery with postoperative radiotherapy (n = 14), and (3) surgery with concurrent chemoradiotherapy (n = 19). Outcome measures included any bone or plate related complications.

RESULTS

The plate and osteosynthesis related complications occurred in 10.5% of patients in surgery-alone group, 28.6% in surgery with postoperative radiation group, and 63.2% in surgery with postoperative concurrent chemoradiotherapy group. The differences in the complication rates among these 3 groups were statistically significant (p = .003). In univariate analysis, postoperative radiation (p = .007) and concurrent chemotherapy (p = .003) were found to be significantly associated with complications. In multivariate analysis, only concurrent chemotherapy was found to be statistically significant (p = .002) with odds ratio of 7.72.

CONCLUSION

Postoperative concurrent chemoradiotherapy significantly increases plate and osteosynthesis related complications in oral cancer.

Adaquate fixation of plates for stability during mandibular reconstruction

PURPOSE

To determine the most appropriate plate fixation for dispersing the stress around screws in mandibular reconstruction.

MATERIAL AND METHODS

Forty-eight three-dimensional reconstructed mandibular models with Central (C) or right Lateral (L) defects were created and divided into three groups, fixed with: (1) two screws on each side, (2) three screws on the left side with the third (middle one) located distally, or (3) three screws on the left side with the third (middle one) located proximally. A 300N vertical load was applied to the left molar region. The maximum stress was calculated using a finite element method and statistically evaluated.

RESULTS

Stress was concentrated around the screw at the distal end of the mandibular halves on the loaded side ('crucial screw'). For the C defect, stress concentrated around the 'crucial screw' was greater when there were only two screws for fixation (20.55MPa) than when there were three screws (16.17MPa; p=0.022). No significant difference was found between the two groups with three screws for fixation. For the L defect on the other hand, stress on the 'crucial screw' was relatively greater when there were three screws for fixation (18.9MPa) than when there were only two screws for (12.83MPa; p=0.051). No significant difference was found between the two groups with three screws for fixation. As for the reconstruction plate, the stresses on the plates were not different among the various screw groups for fixation nor among the C and L defects.

CONCLUSION

This paradoxical result is explained by plate bowing. Thus in large defects screw positions should take into consideration the potential for plate bowing.

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.

Staged protocol for resection, skeletal reconstruction, and oral rehabilitation of children with jaw tumors

PURPOSE

The purpose of this study was to evaluate a staged protocol for resection of jaw tumors and reconstruction including implants in pediatric patients.

PATIENTS AND METHODS

Nine children were evaluated retrospectively. Data included age at resection, tumor type, use of adjuvant therapy, type of bone graft, and number of implants. Occurrence of postoperative infection, tumor margins, recurrence, plate fractures, number of bone grafts, implants restored, and failures were recorded.

RESULTS

Ages ranged from 3.5 to 16 years with 2 maxillary and 7 mandibular tumors. Diagnoses included giant cell lesion (n = 3), osteosarcoma (n = 2), myofibroma (n = 1), ossifying fibroma (n = 1), desmoplastic fibroma (n = 1), and ameloblastoma (n = 1). No patients experienced postoperative infection, wound dehiscence, or jaw instability after en bloc resection. One patient had recurrence of a giant cell lesion. To date (mean, 56 months; range, 24 to 93 months), there have been no additional recurrences. There was 1 plate fracture. Eight patients underwent iliac bone grafts (stage 2), and in 1 patient, the mandible regenerated. There were no graft infections or wound dehiscences. Three patients required additional bone grafting for implant placement. Twenty-three implants were placed in 7 patients without complications, and 21 implants have gone to second stage. One implant failed to osseointegrate. Six patients have had prostheses placed and loaded for a mean of 26 months (range, 5 to 64 months). One patient is scheduled for prosthetic restoration and 2 for implant placement.

CONCLUSION

Pediatric maxillofacial tumors can be successfully treated by resection, rigid fixation, and delayed reconstruction with minimal morbidity and a high success rate.

Mandibular reconstruction: a clinical and radiographic animal study on the use of autogenous scaffolds and platelet-rich plasma

This paper reports on an experimental animal study evaluating a method of mandibular reconstruction. After a successful pilot study, 28 goats underwent a continuity resection of the mandibular angle. Primary reconstruction was carried out using specially designed osteosynthesis plates and screws. The defect was bridged by the original cortical scaffold, filled with an autogenous bone graft from the iliac crest. To accelerate bone healing, platelet-rich plasma (PRP) was mixed with the particulate bone graft in 14 goats. All goats had uneventful healing. The osteosynthesis plates and screws withstood immediate loading for periods varying from 3 weeks to 3 months. The use of PRP appeared to enhance bone healing considerably.

Torsional strength of the radius after osteofasciocutaneous free flap harvest with and without primary bone plating

The osteocutaneous radial forearm free flap (OCRFFF) has not gained widespread popularity in mandibular reconstruction, primarily because of concerns about pathologic fracture of the weakened radius. This study examines the effectiveness of plate fixation of the radius bone after harvest of the OCRFFF as a mechanism to minimize donor-site morbidity and increase the usefulness of the OCRFFF. Matched pairs of fresh human cadaveric radius bones were used in this study. Two study groups were designed. The first group was used to define the amount of strength lost after a typical bone graft harvest. The second group was designed to demonstrate how much torsional strength was regained by the application of an orthopedic reconstruction plate. Statistically significant results were obtained for both groups. In group 1, the strength of the cut bones compared with that of the unaltered bones was significantly decreased by 82% (P = 0.016). In group 2, the cut bones reinforced with a plate were 75% stronger (P = 0.002) than the bones that were only cut. Although the radius bone is significantly weakened by the harvest of a graft, much of this strength can be regained with plate fixation of the radius.

Functional reconstruction of the mandible: a modified titanium mesh system

This paper describes a method for mandibular reconstruction utilizing autogenous cancellous bone in a titanium mesh. The mesh is designed preoperatively based on a duplicate of the patient's mandible which is modified to simulate an anatomically correct edentulous segment in the region to be reconstructed. The duplicate mandible is articulated with a maxillary dental cast, and a locating splint is fabricated for intraoperative use to aid the positioning of the mesh in relation to the upper teeth. The method facilitates future rehabilitation with dental implants and results in a symmetric and highly functional reconstruction of the mandible.

Long-term evaluation of patients undergoing immediate mandibular reconstruction

BACKGROUND

Immediate reconstruction following segmental mandibulectomy is an accepted surgical technique. The benefits and patient selection criteria need to be established.

PATIENTS AND METHODS

Forty-seven patients who underwent immediate reconstruction of the mandible were followed for up to 14 years. Survival, complication rates, and functional results were analyzed.

RESULTS

Median survival was 39 months and actuarial 5-year survival was 40%. Two patients died in the postoperative period, and 9 suffered major reconstruction-related complications. The majority of these complications were related to the use of reconstruction plates, and occurred when the mandibular defect included the arch or when the plates were covered by pectoralis flaps. Half of the patients interviewed were able to eat a regular diet.

CONCLUSIONS

Mandibular reconstruction can be performed safely and expeditiously in nearly all patients undergoing segmental mandibulectomy. Functional results and long-term survival will be acceptable in many cases.

Effect of screw number on reconstruction plating

Recently sacrificed bovine ribs and a hydraulic press were used to evaluate the effect that the number of screws has upon reconstruction plating. Reconstructed segments were subjected to five trials each for one, two, three, four, five, six, seven, and eight screws with increasing weights until failure. Increasing the number of screws increased the amount of weight resisted up to four screws per segment after which no additional benefits were realized (P < .001).

Bridging lower jaw defects with AO plates: comparison of THORP and 3-DBRP systems

Two reconstruction plate systems, the 3-dimensionally-bendable reconstruction plate (3-DBRP) and the titanium hollow screw and reconstruction plate (THORP) were compared in clinical use. Fewer complications in patients were observed with the THORP system than with the 3-DBRP system. In general, both systems are reliable and approved. In cases of extensive defects, however, the THORP system appears to be more effective because of its larger size and its better anchorage.