Three-dimensional titanium miniplates for fixation of subcondylar mandibular fractures: Comparison of five designs using patient-specific finite element analysis

https://doi.org/10.1016/j.jcms.2017.12.020Get rights and content

Abstract

Purpose

The purpose of the current study is to compare the performance of five designs of three-dimensional titanium miniplates (lambda, strut, delta, rhombic and trapezoid) for fixation of subcondylar mandibular fracture.

Materials and methods

Three-dimensional models were constructed for the five miniplates with their screws and integrated into a virtually fractured mandible that was derived from a computed tomographic image of living human. Patient-specific finite element models were analyzed to compare the performances of the miniplates. Miniplates were compared for titanium hardware volume, condylar head displacement, bone strains and miniplates' stresses.

Results

Least condylar head displacement, and thereby best fixation primary stability, was found in the trapezoid miniplate. On the other hand, the greatest displacements were found in lambda and strut miniplates. Bone strains, as an indicator of secondary stability, predicted high strains in bone around the screws affixing the delta miniplate. Therefore, high risk of failure due to screws loosening is expected when using the delta miniplate. Stresses in miniplates were excessive in the strut and lambda miniplates, which implies a high risk of miniplate fracture.

Conclusions

The current findings predicted significant differences in performance among the different designs of three-dimensional miniplates. The trapezoid miniplate seems to have the best performance, as it provided the greatest rigidity with relatively low bone strains.

Introduction

The mandible is the most vulnerable bone to fractures in the maxillofacial complex. Mandibular fractures amounted to 42% of all maxillofacial fractures in a recent prevalence study in a European population (Boffano et al., 2015). One type of mandibular fractures is condyle fractures, which can be classified according to the anatomical position of fracture into three subgroups: intracapsular condylar head fracture, extracapsular condylar neck fracture, and extracapsular subcondylar (condylar base) fractures (Loukota et al., 2005, Wermker, 2009). Condyle extra-capsular fractures comprised 26% of mandibular fractures in the same previously mentioned European study, ranking first among all types of mandibular fractures. In another study using the data from one hospital in Texas over a 17-year period of time (Morris et al., 2015), condyle and subcondylar fractures accounted for 18.4% of maxillofacial fractures, ranking third after angle and symphysis fractures. These figures seem to be largely dependent on the geographical areas and populations. Interesting trends for mandibular fractures were recently reported by Zhou et al. (2016), who stated that condylar fractures are unlikely to be associated with angular fractures. Likewise, angular fractures are associated with a lower risk of condylar fractures.

Several treatment approaches are used for the management of subcondylar mandibular fractures in adults. Primarily the treatment could be either closed reduction with maxillomandibular fixation (MMF) or open reduction with internal fixation (ORIF). The treatment of choice remains a controversial issue (Kyzas et al., 2012, Vesnaver et al., 2012, Shiju et al., 2015), and some surgeons still prefer the closed reduction with MMF (Neff et al., 2014, Kommers et al., 2015). However, ORIF could be necessary and is indicated in fractures with a high degree of displacement (Hackenberg et al., 2014, Cranford et al., 2016). Another controversial issue, which is the focus of the current study, concerns the best design and arrangement of titanium miniplates to be used in ORIF in order to achieve maximum stability of fixed bony fragments.

Previous studies have shown that the performance of one straight miniplate is suboptimal and that the use of two straight miniplates with nonparallel configuration performs better in biomechanical models (Choi et al., 1999, Wagner et al., 2002, Meyer et al., 2006, Tominaga et al., 2006, Parascandolo et al., 2010, Aquilina et al., 2013). However, the limited surgical access to the condyle area and the small dimensions of bone fragments require the use of minimum hardware. Two straight miniplates, each fixed with four screws, may significantly weaken bone fragments, and would be more difficult to handle during surgery. These limitations have encouraged the emergence of new single miniplates with three-dimensional designs that distribute the fixing screws in a nonparallel fashion. Such miniplates are the Delta miniplate (Medartis, Basel, Switzerland), trapezoid miniplate (Synthes CMF, PA and Medartis), and Lambda miniplate (Synthes CMF and Medicon, Tullingen, Germany). Several studies selected some of these miniplates and compared their performances, and sometimes yielded contradictory results due to the different methodologies and conditions between the studies (Lauer et al., 2007a, de Jesus et al., 2014, Hakim et al., 2014, Zrounba et al., 2014, Murakami et al., 2017). The most inclusive and recent study, conducted by Murakami et al. (2017), did not present information related to the displacement of fracture fragments. Therefore, it is difficult to conclude from that study which miniplate provides the most rigid fixation. They investigators focused on stresses in miniplates, which indicates only whether the miniplate will fracture before the other miniplates under certain loads, a problem that is rarely encountered in practice.

In the current study, we aimed to assess the performance of five single three-dimensional (3D) miniplates for fixation of subcondylar mandible fractures using finite element (FE) analysis. Assessment measures included displacements of fracture fragments, strains in bone, and stresses in titanium miniplates.

Section snippets

Construction of 3D models

Computed tomography (CT) of a living human was used to generate a surface model of mandibular bone. Segmentation was performed using the segmentation module in Mechanical Finder V7.0 (RCCM, Osaka, Japan). The left part of the mandible was used for simulations, and the condylar base was cut with a space of 0.25 mm between the fragments. Three-dimensional surface models were developed for five commercially available miniplates using the computer-aided design software Autodesk Inventor

Hardware volume

The analyzed miniplates are significantly different in total volume of miniplate and screws (Fig. 3). Delta and rhombic miniplates have noticeably smaller volumes than other miniplates. These two small miniplates are almost the half of the volume of lambda or strut miniplates. On the other hand, the lambda and strut miniplates have the largest volumes among all miniplates.

Rigidity of osteosynthesis

The FE models yielded significant differences in rigidity among the miniplates. For assessment of rigidity, displacement

Discussion

The mandible is subject to heavy functional forces that generate internal tensile and compressive strains. It is advocated that the successful osteosynthesis of mandibular fractures can only be achieved by moderating the injurious tensile strains (Champy et al., 1978). Efforts have been made to determine the tension and compression lines at the condyle area (Meyer et al., 2002), and it was found that tension lines run below and parallel to the sigmoid notch of the ramus. These biomechanical

Conclusion

The findings of the current study suggest that the trapezoid plate has the best performance among the available three-dimensional miniplates. Further comparative mechanical and clinical studies are needed to confirm this observation.

References (38)

Cited by (30)

  • Biomechanical evaluation of various internal fixation patterns for unilateral mandibular condylar base fractures: A three-dimensional finite element analysis

    2022, Journal of the Mechanical Behavior of Biomedical Materials
    Citation Excerpt :

    Finite element simulation is a numerical method used for biomechanical analysis conventionally, which could help us to get access to quantitative values of stress, strain and displacement in study structures when loads are applied to them. Most relevant FEAs aimed to compare the biomechanical parameters of subcondylar fracture models with different titanium-plate geometries, but did not focus on the selection of device material and exact implanting position (Albogha et al., 2018; de Jesus et al., 2014; Ergezen and Akdeniz, 2020; Murakami et al., 2017). We comprehensively compared different materials and positions of internal fixation in order to improve surgical techniques for condylar base fractures.

  • Application of the lambda plate on condylar fractures: Finite element evaluation of the fixation rigidity for different fracture patterns and plate placements

    2022, Injury
    Citation Excerpt :

    Some fine element analysis studies indicate that in fractures at the condylar neck, the lambda plate may provide better stability compared to other standard plates [11]. In contrast, for condylar base fractures, the results are contradictory [12–14]. Nevertheless, the biomechanical behavior of this relatively new plate design and the stability achieved when applied to different fracture patterns are more or less unknown.

View all citing articles on Scopus
View full text