Clinical Evaluation of Magnesium Alloy Osteosynthesis in the Mandibular Head

Long-term outcomes of open treatment of condylar head fractures using cannulated headless bone screws-a retrospective analysis

The treatment of mandibular fractures affecting the condylar head (CHF) can be either closed or open. In the case of an open approach, the headless bone screw (HBS) is an option. This study was performed to investigate the efficacy of osteosynthesis with HBS using three-dimensional radiographic imaging and clinical evaluation over long-term follow-up. This was a single-centre retrospective study. Clinical parameters and three-dimensional radiographic scans were collected during follow-up, DICOM datasets were segmented, and model analysis was conducted. Forty-five patients who received a HBS and met the eligibility criteria were included. There were significant improvements in all clinical parameters (mouth opening, protrusion, laterotrusion; all P < 0.05) except for the laterotrusion of the unaffected side (P = 0.071). Mean volume and surface area changes (from postoperative (mean 1.9 days) to final follow-up (mean 1675 days)) were 127.2 mm3 and -22.4 mm2, respectively, and were not statistically significant (P = 0.18 and P = 0.51). There were radiographic signs of condylar remodelling. Nine HBS in nine patients required removal due to the screw penetrating the articular surface of the healing condylar head. This single-centre retrospective study found good functional outcomes using HBS for CHF, with a screw removal rate of 20%.

Two versus three magnesium screws for osteosynthesis of mandibular condylar head fractures: a finite element analysis

OBJECTIVES

Previous finite element analyses (FEA) have shown promising results for using two titanium screws in treating mandibular condylar head fractures but limited mechanical stability of a two-screw osteosynthesis with magnesium screws. Given the potential benefits of magnesium screws in terms of biocompatibility and resorption, this study aimed to compare two- and three-screw osteosynthesis solutions for a right condylar head fracture (AO CMF type p) with magnesium screws with a FEA.

MATERIALS AND METHODS

A previously validated finite element model simulating a 350 N bite on the contralateral molars was used to analyze von Mises stress within the screws, fragment deformation, and fracture displacement. All screws were modeled with uniform geometric specifications mirroring the design of Medartis MODUS® Mandible Hexadrive cortical screws.

RESULTS

The three-screw configuration demonstrated lower values for all three parameters compared to the two-screw scenario. There was a 30% reduction in maximum von Mises stress for the top screw and a 46% reduction for the bottom screw.

CONCLUSIONS

Fracture treatment with three magnesium screws could be a valuable and sufficiently stable alternative to the established treatment with titanium screws. Further studies on screw geometry could help improve material stability under mechanical loading, enhancing the performance of magnesium screws in clinical applications.

CLINICAL RELEVANCE

The use of magnesium screws for osteosynthesis of mandibular condylar head fractures offers the benefit of reducing the need for second surgery for hardware removal. Clinical data is needed to determine whether the advantages of resorbable screw materials outweigh potential drawbacks in condylar head fracture treatment.

Personalized Temporomandibular Joint Total Alloplastic Replacement as a Solution to Help Patients with Non-Osteosynthesizable Comminuted Mandibular Head Fractures

Background: Treatment methods for mandibular head fractures are controversial, although effective techniques for open reduction and rigid fixation (ORIF) have been known since the late 1990s. Notably, some forms of posttraumatic comminution of the mandibular head can be reduced or fixed. Methods: This study presents a personalized treatment to cure patients with nonreduced comminuted fractures of the mandibular head: total temporomandibular joint alloplastic replacement (18 patients). The reference group included patients who underwent ORIF (11 patients). Results: Personalized alloplastic joint replacements resulted in a more stable mandibular ramus after three months compared with ORIF. Conclusions: The authors recommend not performing osteosynthesis when the height of the mandibular ramus cannot be stably restored or when periosteal elevation from most of the mandibular head is necessary for ORIF. Personalized TMJ replacement should be considered in such patients. Personalized medicine allows patients to maintain a normal mandibular ramus height for a long period of time.

Titanium vs PEO Surface-Modified Magnesium Plate Fixation in a Mandible Bone Healing Model in Sheep

Titanium plates are the current gold standard for fracture fixation of the mandible. Magnesium alloys such as WE43 are suitable biodegradable alternatives due to their high biocompatibility and elasticity modulus close to those of cortical bone. By surface modification, the reagibility of magnesium and thus hydrogen gas accumulation per time are further reduced, bringing plate fixation with magnesium closer to clinical application. This study aimed to compare bone healing in a monocortical mandibular fracture model in sheep with a human-standard size, magnesium-based, plasma electrolytic-oxidation (PEO) surface modified miniplate fixation system following 4 and 12 weeks. Bone healing was analyzed using micro-computed tomography and histological analysis with Movat's pentachrome and Giemsa staining. For evaluation of the tissue's osteogenic activity, polychrome fluorescent labeling was performed, and vascularization was analyzed using immunohistochemical staining for alpha-smooth muscle actin. Bone density and bone mineralization did not differ significantly between titanium and magnesium (BV/TV: T1: 8.74 ± 2.30%, M1: 6.83 ± 2.89%, p = 0.589 and T2: 71.99 ± 3.13%, M2: 68.58 ± 3.74%, p = 0.394; MinB: T1: 26.16 ± 9.21%, M1: 22.15 ± 7.99%, p = 0.818 and T2: 77.56 ± 3.61%, M2: 79.06 ± 4.46%, p = 0.699). After 12 weeks, minor differences were observed regarding bone microstructure, osteogenic activity, and vascularization. There was significance with regard to bone microstructure (TrTh: T2: 0.08 ± 0.01 mm, M2: 0.06 ± 0.01 mm; p = 0.041). Nevertheless, these differences did not interfere with bone healing. In this study, adequate bone healing was observed in both groups. Only after 12 weeks were some differences detected with larger trabecular spacing and more vessel density in magnesium vs titanium plates. However, a longer observational time with full resorption of the implants should be targeted in future investigations.

Three-dimensional measurements of symmetry for the mandibular ramus

BACKGROUND

The study examines a sample of patients presenting for viscerocranial computer tomography that does not display any apparent signs of asymmetry, assesses the three-dimensional congruency of the mandibular ramus, and focuses on differences in age and gender.

METHODS

This cross-sectional cohort study screened viscerocranial CT data of patients without deformation or developmental anomalies. Segmentations were obtained from the left and right sides and superimposed according to the best-fit alignment. Comparisons were made to evaluate three-dimensional congruency and compared between subgroups according to age and gender.

RESULTS

Two hundred and sixty-eight patients were screened, and one hundred patients met the inclusion criteria. There were no statistical differences between the left and right sides of the mandibular ramus. Also, there were no differences between the subgroups. The overall root mean square was 0.75 ± 0.15 mm, and the mean absolute distance from the mean was 0.54 ± 0.10 mm.

CONCLUSION

The mean difference was less than one millimetre, far below the two-millimetre distance described in the literature that defines relative symmetry. Our study population displays a high degree of three-dimensional congruency. Our findings help to understand that there is sufficient three-dimensional congruency of the mandibular ramus, thus contributing to facilitating CAD-CAM-based procedures based on symmetry for this specific anatomic structure.

Newly Developed Resorbable Magnesium Biomaterials for Orbital Floor Reconstruction in Caprine and Ovine Animal Models-A Prototype Design and Proof-of-Principle Study

BACKGROUND

orbital floor fractures have not been reconstructed using magnesium biomaterials.

METHODS

To test technical feasibility, ex vivo caprine and ovine heads (n = 5) were used. Head tissues were harvested from pubescent animals (n = 5; mean age: 3.2 years; mean mass: 26.3 kg) and stored below 11 degrees for 7-10 days. All procedures were performed in a university animal resource facility. Two experienced maxillofacial surgeons performed orbital floor procedures in both orbits of all animals in a step-by-step preplanned dissection. A transconjunctival approach was chosen to repair the orbital floor with three different implants (i.e., magnesium implants; titanium mesh; and polydioxanone or PDO sheets). The position of each implant was evaluated by Cone-beam computed tomography (CBCT).

RESULTS

Axial, coronal, and sagittal plane images showed good positioning of the magnesium plates. The magnesium plates had a radiographic visibility similar to that of the PDO sheets but lower than that of the titanium mesh.

CONCLUSIONS

The prototype design study showed a novel indication for magnesium biomaterials. Further testing of this new biomaterial may lead to the first resorbable biomaterial with good mechanical properties for extensive orbital wall defects.

Two-screw osteosynthesis of the mandibular condylar head with different screw materials: a finite element analysis

This study compared the biomechanical behavior of titanium, magnesium, and polylactic acid screws for two-screw osteosynthesis of mandibular condylar head fractures using finite element analysis. Von Mises stress distribution, fracture displacement, and fragment deformation were evaluated. Titanium screws performed the best in terms of carrying the highest load, resulting in the least fracture displacement and fragment deformation. Magnesium screws showed intermediate results, while PLA screws were found to be unsuitable with stress values exceeding their tensile strength. These findings suggest that magnesium alloys could be considered a suitable alternative to titanium screws in mandibular condylar head osteosynthesis.

Current Frequency of Mandibular Condylar Process Fractures

There are significant discrepancies in the reported prevalence of condylar process fractures among all mandibular fractures (16.5-56%) in the available literature. In addition, it seems that the actual number of difficult-to-treat fractures of the mandibular head is unknown. The purpose of this study is to present the current incidence of the different types of mandibular process fractures with a special focus on mandibular head fractures. The medical records of 386 patients with single or multiple mandibular fractures were reviewed. Of the fractures found, 58% were body fractures, 32% were angle fractures, 7% were ramus fractures, 2% were coronoid process fractures, and 45% were condylar process fractures. The most common fracture of the condylar process was a basal fracture (54% of condylar fractures), and the second most common fracture was a fracture of the mandibular head (34% of condylar process fractures). Further, 16% of patients had low-neck fractures, and 16% had high-neck fractures. Of the patients with head fractures, 8% had a type A fracture, 34% had a type B fracture, and 73% had a type C fracture. A total of 89.6% of the patients were surgically treated with ORIF. Mandibular head fractures are not as rare as previously thought. Head fractures occur twice as often in the pediatric population than in adults. A mandibular fracture is most likely related to a mandible head fracture. Such evidence can guide the diagnostic procedure in the future.

Methodology: workflow for virtual reposition of mandibular condyle fractures

BACKGROUND

Even though mandibular condyle fractures have a high clinical relevance, their treatment remains somewhat challenging. Open reduction and internal fixation are difficult due to narrow surgical approaches, poor overview during reduction, and a possible risk of facial nerve damage. In times of technical endeavors in surgery, there is a trend towards the usage of stable CAD-CAM-implants from additive manufacturing or titanium laser sintering. Up until now, there have not been any reports of fracture treatment of the mandibular condyle using this technique.

RESULTS AND CONCLUSION

We present a workflow for virtual repositioning of the fractured mandibular condyle, to manufacture patient-specific implants for osteosynthesis with the intention of use of resorbable metal alloys in the future.

Titanium or Biodegradable Osteosynthesis in Maxillofacial Surgery? In Vitro and In Vivo Performances

Osteosynthesis systems are used to fixate bone segments in maxillofacial surgery. Titanium osteosynthesis systems are currently the gold standard. However, the disadvantages result in symptomatic removal in up to 40% of cases. Biodegradable osteosynthesis systems, composed of degradable polymers, could reduce the need for removal of osteosynthesis systems while avoiding the aforementioned disadvantages of titanium osteosyntheses. However, disadvantages of biodegradable systems include decreased mechanical properties and possible foreign body reactions. In this review, the literature that focused on the in vitro and in vivo performances of biodegradable and titanium osteosyntheses is discussed. The focus was on factors underlying the favorable clinical outcome of osteosyntheses, including the degradation characteristics of biodegradable osteosyntheses and the host response they elicit. Furthermore, recommendations for clinical usage and future research are given. Based on the available (clinical) evidence, biodegradable copolymeric osteosyntheses are a viable alternative to titanium osteosyntheses when applied to treat maxillofacial trauma, with similar efficacy and significantly lower symptomatic osteosynthesis removal. For orthognathic surgery, biodegradable copolymeric osteosyntheses are a valid alternative to titanium osteosyntheses, but a longer operation time is needed. An osteosynthesis system composed of an amorphous copolymer, preferably using ultrasound welding with well-contoured shapes and sufficient mechanical properties, has the greatest potential as a biocompatible biodegradable copolymeric osteosynthesis system. Future research should focus on surface modifications (e.g., nanogel coatings) and novel biodegradable materials (e.g., magnesium alloys and silk) to address the disadvantages of current osteosynthesis systems.

The Osteosynthesis of the Mandibular Head, Does the Way the Screws Are Positioned Matter?

Currently, an increasing number of medical centers are treating mandibular head fractures surgically. Dedicated screws for compression osteosynthesis have been developed. However, due to the very limited size of the fractured bones and the considerable technical difficulties accompanying the execution of the fixation, there is little room for correction of the positioning and reinsertion of the screws. Therefore, knowing the optimal position of the fixation material is crucial for therapeutic success. The aim of this study is the evaluation of fixation screw position on the mandibular ramus height obtained in the treatment of the condylar head fracture. A total of 57 patients were included in this study. The loss of mandibular ramus height on computed tomography twelve months after mandibular head osteosynthesis was evaluated in relation to the initial distance of the screws from the fracture line, the angle of insertion of the screw into the bone, and the size of the protrusion to the inner side of the condyle. The relationship of the proximity of the screw to the fracture line, angulation, and the size of the protrusion with the loss of ramus height was confirmed. Conclusions: the optimal location for the superior screw is approx. 4 mm below the fracture line (with any angulation), inferior screw is approx. 8 mm (with any angulation), and anterior screw position is approx. 4-5 mm distant from fracture line with the best angulation of 130 degrees to the lateral mandible ramus surface in the coronal plane.

Bone Union Quality after Fracture Fixation of Mandibular Head with Compression Magnesium Screws

For some years now, fixation devices created with resorbable magnesium alloys for the mandibular head have been clinically available and are beginning to be used. It is thus valuable to evaluate the quality of unions in these cases. The aim of this study was radiological comparison of magnesium versus titanium open reduction and rigid fixations in the mandible condylar head. Thirty-one patients were treated for fractures of the mandibular head with magnesium WE43 alloy headless compression screws (diameter 2.3 mm) and, as a reference group, 29 patients were included with similar construction titanium screws (diameter 1.8 mm). The 12-month results of the treatment were evaluated by the texture analysis of CT. Near similar treatment results were found with magnesium screws in traditional titanium fixation. Magnesium screws result in a higher density of the bone structure in the mandibular head. Conclusions: The quantitative evaluation of bone union after surgical treatment of mandibular head fracture with magnesium compression headless screws indicates that stable consolidation was achieved. Undoubtedly, the resorption process of the screws was found to be incomplete after 12 months, evidenced by a marked densification of the bone structure at the fracture site.