Journal of Cranio-Maxillo-Facial Surgery xxx (2014) 1e4
Contents lists available at ScienceDirect
Journal of Cranio-Maxillo-Facial Surgery journal homepage: www.jcmfs.com
Development plates for stable internal fixation: Study of mechanical resistance in simulated fractures of the mandibular condyle ride Sebastia ~o Celegatti Filho a, Danillo Costa Rodrigues b, Andrezza Lauria b, *, To Roger William Fernandes Moreira b, Simonides Consani a a b
Department of Dental Materials, School of Dentistry of Piracicaba, State University of Campinas (UNICAMP), Piracicaba, SP, Brazil Department of Oral and Maxillofacial Surgery, School of Dentistry of Piracicaba, State University of Campinas (UNICAMP), Piracicaba, SP, Brazil
a r t i c l e i n f o
a b s t r a c t
Article history: Paper received 26 May 2014 Accepted 22 October 2014 Available online xxx
Objective: To develop Y-shaped plates with different thicknesses to be used in simulated fractures of the mandibular condyle. Ten plates were developed in Y shape, containing eight holes, and 30 synthetic polyurethane mandible replicas were developed for the study. Material and methods: The load test was performed on an Instron Model 4411 universal testing machine, applying load in the mediolateral and anterior-posterior positions on the head of the condyle. Two-way ANOVA with Tukey testing with a 5% significance level was used. Results: It was observed that when the load was applied in the medial-lateral plate of greater thickness (1.5 mm), it gave the highest strength, while in the anteroposterior direction, the plate with the highest resistance was of the lesser thickness (0.6 mm). A plate with a thickness of 1.5 mm was the one with the highest average value for all displacements. In the anteroposterior direction, the highest values of resistance were seen in the displacement of 15 mm. Conclusion: After comparing the values of the biomechanical testing found in the scientific literature, it is suggested that the use of Y plates are suitable for use in subcondylar fractures within the limitations of the study. © 2014 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Keywords: Bone plates Internal fixation of fractures Mandibular condyle
1. Introduction Maxillofacial traumas are common and can cause significant functional and esthetic alterations. The main objectives of treatment for facial fractures are restoration of the structures and function, which requires adequate fracture reduction and immobilization. This will consolidate the bone segments, without which important sequelae may ensue, significantly altering the quality of life of patients (Singh et al., 2012). Mandibular condyle fractures are the most common among mandibular fractures and are the ones associated with the highest number of controversies regarding treatment (Villareal et al., 2004; Zrounba et al., 2014). According to Ellis and Throckmorton, 2005, condylar process fractures in facial traumas may be responsible for 25%e35% of all mandibular fractures.
* Corresponding author. Av. Limeira 901, PO Box 52, CEP 13414-903, Piracicaba, SP, Brazil. Tel.: þ55 19 2106 5274. E-mail address: [email protected] (A. Lauria).
The choice of treatment is directly linked to the type of fracture, the patient's age and the degree of functional impairment due to the fracture. Fractures of the mandibular condyle can be corrected using closed techniques (conservative treatment) or open (surgical treatment) (Gealh et al., 2009; Kyzas et al., 2012). Since there is no fixed protocol that governs the treatment of condylar fractures, open and closed reduction can be proposed, and the treatment depends on the individual case and the surgeon (Zachariades et al., 2006). With the advent of stable internal fixation by using plates and titanium screws, which allows stabilization of fractures, a growing interest in open reduction of fractures of the mandibular condyle has emerged (Gealh et al., 2009; Haug et al., 2002). The advantages of surgical treatment of condylar fractures consist of anatomical reduction of the fragments, occlusal stability, restoration of early function, and better facial symmetry, restoring the posterior facial dimension in cases in which there is shortening of the mandible (Manganello and Silva, 2002). In the medical literature, there are several methods of open reduction and internal fixation for fractures of the condylar process
http://dx.doi.org/10.1016/j.jcms.2014.10.029 1010-5182/© 2014 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Celegatti Filho TS, et al., Development plates for stable internal fixation: Study of mechanical resistance in simulated fractures of the mandibular condyle, Journal of Cranio-Maxillo-Facial Surgery (2014), http://dx.doi.org/10.1016/j.jcms.2014.10.029
2
T.S. Celegatti Filho et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2014) 1e4
(Choi et al., 2001) that include attachments with Kirschner wires, miniplates and compressive screws (Wagner et al., 2002; Zrounba et al., 2014). Based on data obtained by authors who have studied different techniques of fixation with plate models (6-hole straight miniplate (Haug et al., 2002); trapezoidal mini-plate (Meyer et al., 2007); rigid fixation trapezoidal mini-plate (Dominik et al., 2011); straight mini-plate with 4 holes, fixing one or two plates (Asprino et al., 2006); and straight mini-plate with 4 holes fixing two separate plates or two overlapping plates (Gealh et al., 2009)), this study aims to evaluate the mechanical strength through a compression test of Toride brand Y-shaped plates (Toride Indústria rcio Ltda., Mogi Mirim, Sa ~o Paulo, Brazil) with different e Come thicknesses, to be used in the techniques of stable internal fixation of fractures of the neck of the mandibular condyle. 2. Material and methods Thirty synthetic polyurethane mandibular replicas (Nacional ~o Paulo, Brazil) were used to carry out this study. Ossos, Jaú, Sa Synthetic replicas were preferred to eliminate variables associated with the mandibles of human cadavers and animal bone sources. The synthetic mandibular replicas were split evenly so that the fracture line was at the lowest point of the sigmoid chamfer up to half the height of the posterior border of the mandible, simulating a subcondylar fracture (Gealh et al., 2009; Asprino et al., 2006). The sectioning of the posterior hemimandible branch was performed with a saw disk (ADES HSS Ø 50.0 0.3 13.0 mm). For this study, 30 stable internal fixation plates with a Y geometry and eight holes were used. The experimental samples were equally divided into three groups of 10 hemimandibles, the first group being fixed on plates 0.6 mm in thickness of (yellow), the second set with plates 1.0 mm in thickness (green) and the third group with plates 1.5 mm in thickness (blue) (Fig. 1A and B). The plates and screws used the rcio Ltda., Mogi Toride 2.0 mm system (Toride Indústria e Come ~o Paulo, Brazil). All groups were subjected to linear loads Mirim, Sa in the mediolateral and anteroposterior directions performed on an Instron Model 4411 universal testing machine (Instron Corp., Norwood, MA) (Fig. 2A and B). In linear compressive loading, values were considered in Newtons (N) obtained from displacements of 5, 10, 15 and 20 mm. Statistical analysis was performed to quantitatively compare the compressive load averages (N) in the mediolateral and anteroposterior directions for displacements of 5, 10, 15 and 20 mm in the linear loading test. The values were analyzed using the SAS 8.0 statistical program (SAS Institute, Cary, NC, USA). Exploratory analysis of the data was initially performed, and a 2-factor analysis of variance (for plate thickness and displacement) and Tukey test (5%) were used. 3. Results In comparing the thicknesses of each plate at every displacement level in the medial-lateral direction (Table 1), the 5-mm and 10-mm levels demonstrated the highest thickness values of 1.0 and 1.5 mm, with no statistical difference between them. At both levels, the 0.6-mm thickness showed the lowest value, with no statistical difference from the others. At the levels of 15 and 20 mm, the highest load value was obtained with the 1.5-mm thickness and the lowest statistical difference value with the 0.6-mm thickness. The level of 10 mm yielded intermediate values. When the compression load was applied in the anteroposterior direction, the two-factor analysis of variance showed a significant difference between the thicknesses and displacements (Table 2). In comparing the thicknesses of each plate in every displacement level, the 5-mm level showed the highest values with the 0.6- and
Fig. 1. A. Hemi-mandibular fracture and plate models. B. Color definition of plates. Yellow indicates 0.6 mm; green, 1.0 mm; and blue, 1.5 mm.
1.5-mm thicknesses. The 1.0 mm thickness showed a lower value. At the 10-mm level, the highest load value was obtained with the 0.6-mm thickness. The 1.0- and 1.5-mm thicknesses had the lowest values. At the 15-mm level, the highest load value was obtained with the 0.6-mm thickness and the lowest with the 1.0-mm thickness. In the anteroposterior compression test, none of the plate thicknesses reached the load in the 20-mm displacement. 4. Discussion Fractures of the condylar region are common and may be responsible for 25%e35% of all mandibular fractures (Villareal et al., 2004). Open reduction with the use of stable internal fixation in condylar fractures has become the standard surgical procedure, with the aim of restoring premature function, restoring occlusion and providing stability of the fracture. Different fixation techniques are used for such goals (Dominik et al., 2011). Surgical procedures for treatment of fractures in the region of the mandibular condyle have produced excellent results when the diagnosis was favorable for the use of stable internal fixation with the installation of plates and screws (Ellis and Throckmorton, 2005). In addition, a meta-analysis by Kyzas et al. (2012) suggested that the use of internal fixation in condylar fractures may be as good or better than conservative management. Choi et al. (2001) in their study conducted a comparison of three different fixation techniques for the mandibular condyle (a plate, a dynamic compression mini-plate, and 2 plates). Cases of plate fracture and loss of screws were observed in the first two groups, in which only one plate was used for fixation. However, when the technique with two plates was used, there was no case of inadequate stability, confirming that the use of two plates promotes a
Please cite this article in press as: Celegatti Filho TS, et al., Development plates for stable internal fixation: Study of mechanical resistance in simulated fractures of the mandibular condyle, Journal of Cranio-Maxillo-Facial Surgery (2014), http://dx.doi.org/10.1016/j.jcms.2014.10.029
T.S. Celegatti Filho et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2014) 1e4
3
Table 2 Anteroposterior compressive load (N) of plates with different thicknesses and different displacements. Thickness
Displacement 5 mm
0.6 mm 1.0 mm 1.5 mm
34.3 (4.0) 29.1 (3.3) 33.4 (6.7)
10 mm cA cB cA
98.2 (15.1) 74.4 (13.0) 73.7 (13.9)
15 mm bA bB bB
147.9 (16.3) 109.9 (0.4) 138.0 (41.7)
20 mm aA aC aB
-
Distinct lowercase letters in line and uppercase letters in columns significantly differ by the Tukey test (p < 0.05).
Fig. 2. A. solid works drawing showing the mediolateral loading. B. Solid works drawing showing the anteroposterior loading.
functional fixation to neutralize the functional stress imposed on the neck of the mandibular condyle. In the same research field, different studies have demonstrated that the use of two plates for the fixation of fractures of the mandibular condyle provided greater resistance for the fixation system (Choi et al., 2001; Wagner et al., 2002; Asprino et al., 2006; Ellis, 2002). However, there are clinical situations in which the use of the osteosynthesis technique using two plates for fixing the condylar fractures is not possible, due to the lack of space in the proximal segment. Thus, this study developed and analyzed the mechanical performance of a Y-shaped plate, for use in stable internal fixation of a fracture of the condyle in situations in which the use of two plates is not possible.
Table 1 Medial-lateral compressive load (N) on plates with different thicknesses and with different levels of displacement. Thickness
Displacement
0.6 mm 1.0 mm 1.5 mm
15.8 (3.3) 23.0 (6.9) 24.5 (6.2)
5 mm
10 mm bB cA cA
23.8 (4.8) 38.3 (10.9) 43.1 (11.2)
15 mm aB bA bA
22.4 (5.8) 41.7 (10.2) 50.4 (12.1)
20 mm aC aB aA
14.4 (4.5) 35.5 (5.6) 49.3 (10.5)
bC bB aA
Distinct lowercase letters in line and uppercase letters in columns significantly differ by the Tukey test (p < 0.05).
The mechanical compression load test performed in this study was chosen in order to compare the results with those of similar studies, but with different types of fixation plates (Haug et al., 2002; Asprino et al., 2006). The study evaluated the effect of mechanical loading compression on the fixation of Y plates in 2.0-mm systems in thicknesses of 0.6, 1.0 and 1.5 mm in simulated subcondylar fractures in polyurethane hemi-mandibles with compression load applications in the mediolateral and anteroposterior directions. Asprino et al. in 2006 assessed the mechanical fixation strength with one or two straight plates with 4 holes in the region of the condylar fracture in polyurethane hemimandible with loading in the medial-lateral direction. The authors obtained an average ultimate load for one plate with monocortical screws of 7.15N, for one plate with bicortical screws the value was 8.23N and for two plates with monocortical, the value was 12.34N. Thus, the results were better with two plates and eight monocortical screws in the medial-lateral direction; although the authors stated that bicortical screws provide greater resistance. Still, the average load applied in the medial-lateral direction with plates 1.0 mm in thickness and bicortical and monocortical screws was smaller than the present results for plates of 1.0 and 1.5 mm, and similar to the two straight plates 1.0 mm in thickness and monocortical screws. This comparison between plates in different studies with a similar mechanical test shows that the configuration of the Y-shaped plates increases the ability of the plate to withstand greater compressive forces, even with a smaller thickness when compared with straight plates. In the same type of research, Haug et al. (2002) studied the fixation of a plate in fracture on the base of the condyle with four different models of straight plates of a 2.0-mm system (without specifying their thickness) in the polyurethane hemi-mandibles. The load application was in the medial-lateral direction and different resistant values were shown. In this study, the miniplates demonstrated the best strength results in the medial-lateral direction, but were lower than those obtained in similar study (Asprino et al., 2006) when they were compared with two fixation plates. In relation to the present study, all averages of resistance obtained in these studies (Haug et al., 2002; Asprino et al., 2006) were lower than those presented by the three Y-shaped plates. Analyzing the geometry of the plates, it is possible to affirm that the vertex of the Y plate was attached right on the fracture, providing a greater torsional resistance of the plate towards the medial-lateral load. Besides this favorable factor, the choice of the screws was also of the utmost importance, because the branch unit of the plate remained fixed near the head of the condyle, with one 12-mm top screw and one 10-mm screw below, providing a greater thread area. Furthermore, below the bottom plate, six screws of 8 mm were placed, 3 in each branch of the plate, giving greater stability to the fixation, and helping to achieve higher strength values. The use of bicortical screws for plate fixation seems to agree with the study of Ellis III in 2002, who reported that bicortical screws provide an increased contact area in condyle fractures and therefore greater mechanical strength.
Please cite this article in press as: Celegatti Filho TS, et al., Development plates for stable internal fixation: Study of mechanical resistance in simulated fractures of the mandibular condyle, Journal of Cranio-Maxillo-Facial Surgery (2014), http://dx.doi.org/10.1016/j.jcms.2014.10.029
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T.S. Celegatti Filho et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2014) 1e4
The resistance to the displacement and distribution of forces introduced by the fixation of the subcondylar fractures demonstrated that the posterior extension of the trapezoidal plates increased the resistance of displacement of the fixation system relative to the plates without extension (Assis, 2010). It was observed, when comparing studies, that the results were similar in the medial-lateral and the anterior-posterior direction with trapezoidal plates of 1.5 mm and 2.0 mm with, and without prolongation. This situation probably occurred because both the trapezoidal plates, as well as those of the Y shape, were installed in the same regions of the fracture. The evaluation of Dominik et al. (2011) on the mechanical stability of the animal condylar fracture by fixation with different plate models (Trilok trapezoidal, conventional trapezoidal and two straight conventional plates, all of the 2.0-mm system) proved that the systems could produce favorable results. However, the Trilok rigid plate presented the advantage of absence of loosening the screws during the compressive load test, which was also seen with the screws fixated on the conventional Y plates in this study. Although the results of the mechanical strength obtained with the Y-shaped plates have been positive, one should not consider that this plate model has better mechanical properties when compared with the fixation materials available on the market. Confirmation is still needed regarding the biological behavior, and longitudinal clinical studies are necessary to evaluate the in vivo behavior of the Y plates. However, in situations in which it is not possible to fix two separated plates in the proximal segment of the condyle fracture, the Y-shaped plate shows a reasonable alternative for fixation according to the molds used in this study. Despite the mechanical resistance values observed in vitro in the medical literature and the suggestion that the use of the Y-shaped plates could be useful in subcondylar fractures, it is not yet feasible to transfer the results directly to in vivo situations. 5. Conclusion According to the methodology and considering the limitations of this study, Y-shaped plates are suitable for stable internal fixation of condylar fractures since in mechanical tests, they showed similar behavior in comparison to the plates conventionally used in condylar fractures. Disclosure There are no disclose with any commercial associations, current and within the past five years, that might pose a potential,
perceived, or real conflict of interest. These include grants, patent licensing arrangements, consultancies, stock or other equity ownership, advisory board memberships, or payments for conducting or publicizing the study.
Conflicts of interest The authors confirm that there are no conflicts of interest in the present study.
References Asprino L, Consani S, Moraes M: A comparative biomechanical evaluation of mandibular condyle fracture plating techniques. J Oral Maxillofac Surg 64: 452e456, 2006 Assis AF: Mechanical and photoelastic analysis of internal fixation systems used for treatment of subcondylar mandibular fractures. Piracicaba e Brazil: School of Dentistry of Piracicaba, State University of Campinas (UNICAMP), 2010 PhD Thesis [Portuguese] Choi B-H, Yi C-K, Yoo J-H: Clinical evaluation of 3 types of plate osteosynthesis for fixation of condylar neck fractures. J Oral Maxillofac Surg 59: 734e737, 2001 Dominik H, Annett M, Leonhardt H, Alexander N, Gerd R, Günter L: Biomechanical study of the delta plate and the TriLock delta condyle trauma plate. J Oral Maxillofac Surg 69: 2619e2625, 2011 Ellis III E: A biomechanical evaluation of mandibular condyle fracture plating techniques. J Oral Maxillofac Surg 60, 2002 [Discussion] Ellis III E, Throckmorton GS: Treatment of mandibular condylar process fractures: biological considerations. J Oral Maxillofac Surg 63: 115e134, 2005 Gealh WC, Costa JV, Ferreira GM, Iwaki-Filho L: Comparative study of the mechanical resistance of 2 separate plates and 2 overlaid plates used in the fixation of the mandibular condyle: an in vitro study. J Oral Maxillofac Surg 67: 738e743, 2009 Haug RH, Peterson GP, Goltz M: A biomechanical evaluation of mandibular condyle fracture plating techniques. J Oral Maxillofac Surg 60: 73e80, 2002 Kyzas PA, Saeed S, Tabbenor O: The treatment of mandibular condyle fractures: a meta-analysis. J Craniomaxillofac Surg 40: 438e452, 2012 Manganello LC, Silva AAF: Mandibular condylar fractures: classification and treatment. Rev Bras Otorrinolaringol 68: 749e754, 2002 [Portuguese] Meyer C, Martin E, Kahn JL, Zink S: Development and biomechanical testing of a new osteosynthesis plate (TCP) designed to stabilize mandibular condyle fractures. J Craniomaxillofac Surg 35: 84e90, 2007 Singh V, Malkunje L, Mohammad S, Singh N, Dhasmana S, Das SK: The maxillofacial injuries: a study. Natl J Maxillofac Surg 3(2): 166e171, 2012 lez C: Mandibular Villareal PM, Monje F, Junquera LM, Mateo J, Morillo AJ, Gonza condyle fractures: determinants of treatment and outcome. J Oral Maxillofac Surg 62: 155e163, 2004 Wagner A, Krach W, Schicho K, Undt G, Ploder O, Ewers R: A 3-dimensional finite element analysis investigating the biomechanical behavior of the mandible and plate osteosynthesis in cases of fractures of the condylar process. Oral Surg Oral Med Oral Pathol Oral Endod 94: 678e686, 2002 Zachariades N, Mezitis M, Constintine M, Demetrius P, Spanou A: Fractures of the mandibular condyle: a review of 466 cases. J Craniomaxillofac Surg 34: 421e432, 2006 Zrounba H, Lutz JC, Zink S, Wilk A: Epidemiology and treatment outcome of surgically treated mandibular condyle fractures. A five years retrospective study. J Craniomaxillofac Surg 42: 879e884, 2014
Please cite this article in press as: Celegatti Filho TS, et al., Development plates for stable internal fixation: Study of mechanical resistance in simulated fractures of the mandibular condyle, Journal of Cranio-Maxillo-Facial Surgery (2014), http://dx.doi.org/10.1016/j.jcms.2014.10.029
Contents lists available at ScienceDirect
Journal of Cranio-Maxillo-Facial Surgery journal homepage: www.jcmfs.com
Development plates for stable internal fixation: Study of mechanical resistance in simulated fractures of the mandibular condyle ride Sebastia ~o Celegatti Filho a, Danillo Costa Rodrigues b, Andrezza Lauria b, *, To Roger William Fernandes Moreira b, Simonides Consani a a b
Department of Dental Materials, School of Dentistry of Piracicaba, State University of Campinas (UNICAMP), Piracicaba, SP, Brazil Department of Oral and Maxillofacial Surgery, School of Dentistry of Piracicaba, State University of Campinas (UNICAMP), Piracicaba, SP, Brazil
a r t i c l e i n f o
a b s t r a c t
Article history: Paper received 26 May 2014 Accepted 22 October 2014 Available online xxx
Objective: To develop Y-shaped plates with different thicknesses to be used in simulated fractures of the mandibular condyle. Ten plates were developed in Y shape, containing eight holes, and 30 synthetic polyurethane mandible replicas were developed for the study. Material and methods: The load test was performed on an Instron Model 4411 universal testing machine, applying load in the mediolateral and anterior-posterior positions on the head of the condyle. Two-way ANOVA with Tukey testing with a 5% significance level was used. Results: It was observed that when the load was applied in the medial-lateral plate of greater thickness (1.5 mm), it gave the highest strength, while in the anteroposterior direction, the plate with the highest resistance was of the lesser thickness (0.6 mm). A plate with a thickness of 1.5 mm was the one with the highest average value for all displacements. In the anteroposterior direction, the highest values of resistance were seen in the displacement of 15 mm. Conclusion: After comparing the values of the biomechanical testing found in the scientific literature, it is suggested that the use of Y plates are suitable for use in subcondylar fractures within the limitations of the study. © 2014 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Keywords: Bone plates Internal fixation of fractures Mandibular condyle
1. Introduction Maxillofacial traumas are common and can cause significant functional and esthetic alterations. The main objectives of treatment for facial fractures are restoration of the structures and function, which requires adequate fracture reduction and immobilization. This will consolidate the bone segments, without which important sequelae may ensue, significantly altering the quality of life of patients (Singh et al., 2012). Mandibular condyle fractures are the most common among mandibular fractures and are the ones associated with the highest number of controversies regarding treatment (Villareal et al., 2004; Zrounba et al., 2014). According to Ellis and Throckmorton, 2005, condylar process fractures in facial traumas may be responsible for 25%e35% of all mandibular fractures.
* Corresponding author. Av. Limeira 901, PO Box 52, CEP 13414-903, Piracicaba, SP, Brazil. Tel.: þ55 19 2106 5274. E-mail address: [email protected] (A. Lauria).
The choice of treatment is directly linked to the type of fracture, the patient's age and the degree of functional impairment due to the fracture. Fractures of the mandibular condyle can be corrected using closed techniques (conservative treatment) or open (surgical treatment) (Gealh et al., 2009; Kyzas et al., 2012). Since there is no fixed protocol that governs the treatment of condylar fractures, open and closed reduction can be proposed, and the treatment depends on the individual case and the surgeon (Zachariades et al., 2006). With the advent of stable internal fixation by using plates and titanium screws, which allows stabilization of fractures, a growing interest in open reduction of fractures of the mandibular condyle has emerged (Gealh et al., 2009; Haug et al., 2002). The advantages of surgical treatment of condylar fractures consist of anatomical reduction of the fragments, occlusal stability, restoration of early function, and better facial symmetry, restoring the posterior facial dimension in cases in which there is shortening of the mandible (Manganello and Silva, 2002). In the medical literature, there are several methods of open reduction and internal fixation for fractures of the condylar process
http://dx.doi.org/10.1016/j.jcms.2014.10.029 1010-5182/© 2014 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Celegatti Filho TS, et al., Development plates for stable internal fixation: Study of mechanical resistance in simulated fractures of the mandibular condyle, Journal of Cranio-Maxillo-Facial Surgery (2014), http://dx.doi.org/10.1016/j.jcms.2014.10.029
2
T.S. Celegatti Filho et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2014) 1e4
(Choi et al., 2001) that include attachments with Kirschner wires, miniplates and compressive screws (Wagner et al., 2002; Zrounba et al., 2014). Based on data obtained by authors who have studied different techniques of fixation with plate models (6-hole straight miniplate (Haug et al., 2002); trapezoidal mini-plate (Meyer et al., 2007); rigid fixation trapezoidal mini-plate (Dominik et al., 2011); straight mini-plate with 4 holes, fixing one or two plates (Asprino et al., 2006); and straight mini-plate with 4 holes fixing two separate plates or two overlapping plates (Gealh et al., 2009)), this study aims to evaluate the mechanical strength through a compression test of Toride brand Y-shaped plates (Toride Indústria rcio Ltda., Mogi Mirim, Sa ~o Paulo, Brazil) with different e Come thicknesses, to be used in the techniques of stable internal fixation of fractures of the neck of the mandibular condyle. 2. Material and methods Thirty synthetic polyurethane mandibular replicas (Nacional ~o Paulo, Brazil) were used to carry out this study. Ossos, Jaú, Sa Synthetic replicas were preferred to eliminate variables associated with the mandibles of human cadavers and animal bone sources. The synthetic mandibular replicas were split evenly so that the fracture line was at the lowest point of the sigmoid chamfer up to half the height of the posterior border of the mandible, simulating a subcondylar fracture (Gealh et al., 2009; Asprino et al., 2006). The sectioning of the posterior hemimandible branch was performed with a saw disk (ADES HSS Ø 50.0 0.3 13.0 mm). For this study, 30 stable internal fixation plates with a Y geometry and eight holes were used. The experimental samples were equally divided into three groups of 10 hemimandibles, the first group being fixed on plates 0.6 mm in thickness of (yellow), the second set with plates 1.0 mm in thickness (green) and the third group with plates 1.5 mm in thickness (blue) (Fig. 1A and B). The plates and screws used the rcio Ltda., Mogi Toride 2.0 mm system (Toride Indústria e Come ~o Paulo, Brazil). All groups were subjected to linear loads Mirim, Sa in the mediolateral and anteroposterior directions performed on an Instron Model 4411 universal testing machine (Instron Corp., Norwood, MA) (Fig. 2A and B). In linear compressive loading, values were considered in Newtons (N) obtained from displacements of 5, 10, 15 and 20 mm. Statistical analysis was performed to quantitatively compare the compressive load averages (N) in the mediolateral and anteroposterior directions for displacements of 5, 10, 15 and 20 mm in the linear loading test. The values were analyzed using the SAS 8.0 statistical program (SAS Institute, Cary, NC, USA). Exploratory analysis of the data was initially performed, and a 2-factor analysis of variance (for plate thickness and displacement) and Tukey test (5%) were used. 3. Results In comparing the thicknesses of each plate at every displacement level in the medial-lateral direction (Table 1), the 5-mm and 10-mm levels demonstrated the highest thickness values of 1.0 and 1.5 mm, with no statistical difference between them. At both levels, the 0.6-mm thickness showed the lowest value, with no statistical difference from the others. At the levels of 15 and 20 mm, the highest load value was obtained with the 1.5-mm thickness and the lowest statistical difference value with the 0.6-mm thickness. The level of 10 mm yielded intermediate values. When the compression load was applied in the anteroposterior direction, the two-factor analysis of variance showed a significant difference between the thicknesses and displacements (Table 2). In comparing the thicknesses of each plate in every displacement level, the 5-mm level showed the highest values with the 0.6- and
Fig. 1. A. Hemi-mandibular fracture and plate models. B. Color definition of plates. Yellow indicates 0.6 mm; green, 1.0 mm; and blue, 1.5 mm.
1.5-mm thicknesses. The 1.0 mm thickness showed a lower value. At the 10-mm level, the highest load value was obtained with the 0.6-mm thickness. The 1.0- and 1.5-mm thicknesses had the lowest values. At the 15-mm level, the highest load value was obtained with the 0.6-mm thickness and the lowest with the 1.0-mm thickness. In the anteroposterior compression test, none of the plate thicknesses reached the load in the 20-mm displacement. 4. Discussion Fractures of the condylar region are common and may be responsible for 25%e35% of all mandibular fractures (Villareal et al., 2004). Open reduction with the use of stable internal fixation in condylar fractures has become the standard surgical procedure, with the aim of restoring premature function, restoring occlusion and providing stability of the fracture. Different fixation techniques are used for such goals (Dominik et al., 2011). Surgical procedures for treatment of fractures in the region of the mandibular condyle have produced excellent results when the diagnosis was favorable for the use of stable internal fixation with the installation of plates and screws (Ellis and Throckmorton, 2005). In addition, a meta-analysis by Kyzas et al. (2012) suggested that the use of internal fixation in condylar fractures may be as good or better than conservative management. Choi et al. (2001) in their study conducted a comparison of three different fixation techniques for the mandibular condyle (a plate, a dynamic compression mini-plate, and 2 plates). Cases of plate fracture and loss of screws were observed in the first two groups, in which only one plate was used for fixation. However, when the technique with two plates was used, there was no case of inadequate stability, confirming that the use of two plates promotes a
Please cite this article in press as: Celegatti Filho TS, et al., Development plates for stable internal fixation: Study of mechanical resistance in simulated fractures of the mandibular condyle, Journal of Cranio-Maxillo-Facial Surgery (2014), http://dx.doi.org/10.1016/j.jcms.2014.10.029
T.S. Celegatti Filho et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2014) 1e4
3
Table 2 Anteroposterior compressive load (N) of plates with different thicknesses and different displacements. Thickness
Displacement 5 mm
0.6 mm 1.0 mm 1.5 mm
34.3 (4.0) 29.1 (3.3) 33.4 (6.7)
10 mm cA cB cA
98.2 (15.1) 74.4 (13.0) 73.7 (13.9)
15 mm bA bB bB
147.9 (16.3) 109.9 (0.4) 138.0 (41.7)
20 mm aA aC aB
-
Distinct lowercase letters in line and uppercase letters in columns significantly differ by the Tukey test (p < 0.05).
Fig. 2. A. solid works drawing showing the mediolateral loading. B. Solid works drawing showing the anteroposterior loading.
functional fixation to neutralize the functional stress imposed on the neck of the mandibular condyle. In the same research field, different studies have demonstrated that the use of two plates for the fixation of fractures of the mandibular condyle provided greater resistance for the fixation system (Choi et al., 2001; Wagner et al., 2002; Asprino et al., 2006; Ellis, 2002). However, there are clinical situations in which the use of the osteosynthesis technique using two plates for fixing the condylar fractures is not possible, due to the lack of space in the proximal segment. Thus, this study developed and analyzed the mechanical performance of a Y-shaped plate, for use in stable internal fixation of a fracture of the condyle in situations in which the use of two plates is not possible.
Table 1 Medial-lateral compressive load (N) on plates with different thicknesses and with different levels of displacement. Thickness
Displacement
0.6 mm 1.0 mm 1.5 mm
15.8 (3.3) 23.0 (6.9) 24.5 (6.2)
5 mm
10 mm bB cA cA
23.8 (4.8) 38.3 (10.9) 43.1 (11.2)
15 mm aB bA bA
22.4 (5.8) 41.7 (10.2) 50.4 (12.1)
20 mm aC aB aA
14.4 (4.5) 35.5 (5.6) 49.3 (10.5)
bC bB aA
Distinct lowercase letters in line and uppercase letters in columns significantly differ by the Tukey test (p < 0.05).
The mechanical compression load test performed in this study was chosen in order to compare the results with those of similar studies, but with different types of fixation plates (Haug et al., 2002; Asprino et al., 2006). The study evaluated the effect of mechanical loading compression on the fixation of Y plates in 2.0-mm systems in thicknesses of 0.6, 1.0 and 1.5 mm in simulated subcondylar fractures in polyurethane hemi-mandibles with compression load applications in the mediolateral and anteroposterior directions. Asprino et al. in 2006 assessed the mechanical fixation strength with one or two straight plates with 4 holes in the region of the condylar fracture in polyurethane hemimandible with loading in the medial-lateral direction. The authors obtained an average ultimate load for one plate with monocortical screws of 7.15N, for one plate with bicortical screws the value was 8.23N and for two plates with monocortical, the value was 12.34N. Thus, the results were better with two plates and eight monocortical screws in the medial-lateral direction; although the authors stated that bicortical screws provide greater resistance. Still, the average load applied in the medial-lateral direction with plates 1.0 mm in thickness and bicortical and monocortical screws was smaller than the present results for plates of 1.0 and 1.5 mm, and similar to the two straight plates 1.0 mm in thickness and monocortical screws. This comparison between plates in different studies with a similar mechanical test shows that the configuration of the Y-shaped plates increases the ability of the plate to withstand greater compressive forces, even with a smaller thickness when compared with straight plates. In the same type of research, Haug et al. (2002) studied the fixation of a plate in fracture on the base of the condyle with four different models of straight plates of a 2.0-mm system (without specifying their thickness) in the polyurethane hemi-mandibles. The load application was in the medial-lateral direction and different resistant values were shown. In this study, the miniplates demonstrated the best strength results in the medial-lateral direction, but were lower than those obtained in similar study (Asprino et al., 2006) when they were compared with two fixation plates. In relation to the present study, all averages of resistance obtained in these studies (Haug et al., 2002; Asprino et al., 2006) were lower than those presented by the three Y-shaped plates. Analyzing the geometry of the plates, it is possible to affirm that the vertex of the Y plate was attached right on the fracture, providing a greater torsional resistance of the plate towards the medial-lateral load. Besides this favorable factor, the choice of the screws was also of the utmost importance, because the branch unit of the plate remained fixed near the head of the condyle, with one 12-mm top screw and one 10-mm screw below, providing a greater thread area. Furthermore, below the bottom plate, six screws of 8 mm were placed, 3 in each branch of the plate, giving greater stability to the fixation, and helping to achieve higher strength values. The use of bicortical screws for plate fixation seems to agree with the study of Ellis III in 2002, who reported that bicortical screws provide an increased contact area in condyle fractures and therefore greater mechanical strength.
Please cite this article in press as: Celegatti Filho TS, et al., Development plates for stable internal fixation: Study of mechanical resistance in simulated fractures of the mandibular condyle, Journal of Cranio-Maxillo-Facial Surgery (2014), http://dx.doi.org/10.1016/j.jcms.2014.10.029
4
T.S. Celegatti Filho et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2014) 1e4
The resistance to the displacement and distribution of forces introduced by the fixation of the subcondylar fractures demonstrated that the posterior extension of the trapezoidal plates increased the resistance of displacement of the fixation system relative to the plates without extension (Assis, 2010). It was observed, when comparing studies, that the results were similar in the medial-lateral and the anterior-posterior direction with trapezoidal plates of 1.5 mm and 2.0 mm with, and without prolongation. This situation probably occurred because both the trapezoidal plates, as well as those of the Y shape, were installed in the same regions of the fracture. The evaluation of Dominik et al. (2011) on the mechanical stability of the animal condylar fracture by fixation with different plate models (Trilok trapezoidal, conventional trapezoidal and two straight conventional plates, all of the 2.0-mm system) proved that the systems could produce favorable results. However, the Trilok rigid plate presented the advantage of absence of loosening the screws during the compressive load test, which was also seen with the screws fixated on the conventional Y plates in this study. Although the results of the mechanical strength obtained with the Y-shaped plates have been positive, one should not consider that this plate model has better mechanical properties when compared with the fixation materials available on the market. Confirmation is still needed regarding the biological behavior, and longitudinal clinical studies are necessary to evaluate the in vivo behavior of the Y plates. However, in situations in which it is not possible to fix two separated plates in the proximal segment of the condyle fracture, the Y-shaped plate shows a reasonable alternative for fixation according to the molds used in this study. Despite the mechanical resistance values observed in vitro in the medical literature and the suggestion that the use of the Y-shaped plates could be useful in subcondylar fractures, it is not yet feasible to transfer the results directly to in vivo situations. 5. Conclusion According to the methodology and considering the limitations of this study, Y-shaped plates are suitable for stable internal fixation of condylar fractures since in mechanical tests, they showed similar behavior in comparison to the plates conventionally used in condylar fractures. Disclosure There are no disclose with any commercial associations, current and within the past five years, that might pose a potential,
perceived, or real conflict of interest. These include grants, patent licensing arrangements, consultancies, stock or other equity ownership, advisory board memberships, or payments for conducting or publicizing the study.
Conflicts of interest The authors confirm that there are no conflicts of interest in the present study.
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Please cite this article in press as: Celegatti Filho TS, et al., Development plates for stable internal fixation: Study of mechanical resistance in simulated fractures of the mandibular condyle, Journal of Cranio-Maxillo-Facial Surgery (2014), http://dx.doi.org/10.1016/j.jcms.2014.10.029
