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Biomechanical comparison of different plating techniques in

repair of mandibular angle fractures

Alper Alkan, DDS, PhD,a Nkhet elebi, DDS,b Bora zden, DDS, PhD,c Burcu Bas, DDS,b

and Samet Inal, DDS,b

Kayseri and Samsun, TurkeyERCIYES UNIVERSITY AND ONDOKUZ MAYIS UNIVERSITY

Objective. The purpose of this study was to evaluate the biomechanical behaviors of different miniplate fixationtechniques for treatment of fractures of the mandibular angle.Study design. Twenty sheep hemimandibles were used to evaluate 4 different plating techniques. The groups werefixated with Champy technique, biplanar plate placement, monoplanar plate placement, and 3-dimensional (3D)curved angle strut plate. A custom-made 3-point biomechanical test model was used for the samples. Each group wastested with compression forces by an Instron Lloyd LRX machine. The biomechanical behavior of the groups for theforces (N) that caused displacement of 1.75 mm were compared using the Instron software program and displacementgraphics.Results. The variance analyses showed that biplanar plate placement had more favorable biomechanical behaviorthan Champy technique and monoplanar plate placement (P .05). In addition, the 3D curved angle strut plate

technique had more favorable biomechanical behavior than the Champy technique (P

.05) but was not significantlydifferent from biplanar or monoplanar plate placement techniques (P .05).Conclusion. The study demonstrated that 3D strut plates or dual miniplate techniques had greater resistance tocompression loads than the Champy technique. In addition, biplanar plate orientation may provide a more favorablebiomechanical behavior than monoplanar plate placement. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod2007;104:752-6)

The angle is one of the most frequent fractured sitesafter traumatic events involving the mandible.1 Theoptimal treatment of angle fractures remains controver-sial.2 Apart from conservative measures, several surgi-cal methods may be applied to treat mandibular frac-tures.3 Current trends use a variety and combination oftransorally placed small plates secured with monocor-tical screws for the fixation of angle fractures.4

Miniplate osteosynthesis allows early exercise and hasthe advantage of using plates that are easy to adapt.5 Itis a standard treatment for fractures of the mandibularangle. The purpose of the present study was to evaluatethe biomechanical behavior of 4 different types of rigidfixation systems with miniplates that are used currentlyto reconstruct mandibular angle fractures.

MATERIALS AND METHODSTwenty hemimandibles taken from similar sheep

(mean weight 40 kg, fed on the same diet, collectedfrom the same abattoir, and slaughtered similarly) wereused in this investigation. The mandibles were strippedof their soft tissues and divided in the anterior midlinebetween the central incisors. The specimens were keptmoist and refrigerated until all testing was complete.Because of the difficulty in placing the mandibles in thebiomechanical experimental test jig, all coronoid pro-cesses were removed. The models were sectioned in auniform manner with a saw from the retromolar regionon a line that connected to the angle of the mandible.The hemimandibles were randomly divided into 4groups of 5 and fixated with 4 different plating tech-niques (Figs. 1-4; Table I). Titanium 4-hole noncom-pression miniplates (Electron Medical, Trimed, Tur-key) were used in groups 1, 2, and 3. To minimize thevariables in this investigation, all the screws were 5 mmin length, fabricated titanium, and self-tapping. Thefractured segments were all repositioned. Miniplatesand screws were situated in the proper position, andrigid fixation was noted in all groups. The plates wereadapted with pliers and screwed in with a screwdriver.The fragments were stabilized manually during thesestages. A custom-made 3-point biomechanical testmodel which was used in our previous biomechanical

aAssociate Professor, Department of Oral and Maxillofacial Surgery,Faculty of Dentistry, Erciyes University.bResearch Assistant, Department of Oral and Maxillofacial Surgery,Faculty of Dentistry, Ondokuz Mays University.cAssistant Professor, Department of Oral and Maxillofacial Surgery,Faculty of Dentistry, Ondokuz Mays University.Received for publication Jan 3, 2007; returned for revision Jan 27,2007; accepted for publication Mar 17, 2007.1079-2104/$ - see front matter 2007 Mosby, Inc. All rights reserved.doi:10.1016/j.tripleo.2007.03.014

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studies6,7 was adapted to an Instron Lloyd LRX ma-chine, and the samples were fixed from the mandibularcondyle and incisor regions (Fig. 5). The mandibleswere then loaded at the mandibular angle with a com-pression force (N) that simulated masticatory loads,ranging from 0 to 700 N. The experimental end pointwas defined as failure (loss of integrity of the bone-

screw-plate system). The Instron equipment recordedforce versus displacement. A 1.75 mm displacementpoint was defined as the end point, and the loads thatcreated this magnitude of displacement were measuredon the displacement graphics. One-way analysis of

variance was used to test the hypothesis that meanswere equal when comparing the 4 different platingtechniques in terms of noncategoric scale variables.Once it was determined that differences existed amongthe means, pair-wise multiple comparisons were madeusing the Duncan multiple range test.

RESULTSTwenty hemimandibles were analyzed in this exper-

iment, with 5 in each group. Standardization of allexperimental factors except the fixation techniques wasensured. No miniplate fixation system or hemimandible

failures (breakage or fracture) were observed within the0 to 700 N test range. The mean loads that created 1.75mm displacement are shown in Table II. Pair-wisemultiple comparisons are shown in Table III. The vari-ance analyses showed that biplanar plate placementhad more favorable biomechanical behavior than theChampy technique and monoplanar plate placement(P .05). In addition, the 3D curved angle strut platetechnique had more favorable biomechanical behaviorthan the Champy technique (P .05), whereas it wasnot significantly different from biplanar or monoplanarplate placement techniques (P .05).

Fig. 1. Reconstruction with Champy technique.

Fig. 2. Reconstruction with biplanar plate placement.

Fig. 3. Reconstruction with monoplanar plate placement.

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DISCUSSION

Internal rigid fixation alleviates the need for pro-tracted periods of fixation and are associated with fewcomplications and compliance problems.8 The evolu-tion of internal fixation was aided by the discovery ofbiocompatible materials that resisted corrosion, such asvitallium and titanium. Currently, titanium is the metalof choice for fixation plates, mainly because of its highbiocompability, ease ofmanipulation, and the potentialfor no second surgery.9 Titanium miniplates providerigid fixation for mandibular fractures. They can beeasily adapted to the bone curvature and require only asimple surgical procedure. Although a spectrum of

techniques for treatment of angle fractures withminiplates has been proposed in the literature, no con-

sensus exists as to the optimal miniplate fixation mo-dality.

Using a 3-point loading model and animal sourcedhemimandibles, the present investigation evaluated 4different miniplate techniques that are most commonlyused by maxillofacial surgeons. Because of similaritiesin size and thickness to human mandibles, we usedfresh sheep mandibles. In a series of biomechanicalstudies on mandibular fractures, Haug et al.10,11,12 usedpolyurethane mandibles which replicate cancellousbone, have a dense outer core that replicates corticalbone, and are able to provide more uniform sampling.

Fig. 4. Reconstruction with 3-dimensional curved angle strutplate.

Table I. Fixation techniquesGroup Fixation techniques

1 Champy technique (a single miniplate placedjust above the external superior obliqueline)

2 Biplanar plate placement (plates positionedin 2 planes)

3 Monoplanar plate placement (platespositioned in 1 plane)

4 3-dimensional curved angle strut plate(Mondeal Medical Systems, Tuttlingen,Germany)

Fig. 5. Custom-made 3-point biomechanical test model.

Table II. Some descriptive statistics of the groups (N)Group Mean (N) SD SE Min. Max.

1 55.55 22.68 10.14 37.037 92.592 188.89 80.08 35.79 92.59 277.773 81.61 30.95 13.84 55.55 277.774 155.55 74.77 33.44 74.074 277.77

SD, standard deviation; SE, standard error.

Table III. Pair-wise multiple comparisons of the meanloads of the groupsGroup Load (N)

1 55.55a

2 188.89c

3 81.61ab

4 155.55bc

Pair-wise multiple comparisons of the mean loads of the groups at1.75 mm displacement.Groups with different superscriptsabc are different from each other.

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However, complex mandibular anatomy and the thick-ness of cortical bone in animal mandibles play a part inthe strength of any fixation techniques. Fresh sheephemimandibles are easy to obtain for the investigationof biomechanics of the many and varied fixation sys-tems. They have previously been used for biomechani-

cal research.13,14 Our choice of jig and method ofloading were used in our previous biomechanical stud-ies of plating techniques for fractures of the mandibularcondyle6 and designed to replicate three main forcesthat act on the mandible in function.

The adult human man may generate between 300 and400 N maximal bite force.15 This magnitude is reducedwhen a fracture has occurred in the masticatory sys-tem.16 For this reason, when attempting to evaluate thebiomechanics of various fixation techniques, it is im-portant to consider clinically relevant parameters toprovide meaningful information to the clinician. In the

literature, there are only a few investigations that eval-uate the bite forces of the postsurgical population.16-19

Ellis et al.17-19 found that the bite forces in the acutepostoperative period of the patients treated for mandib-ular angle fractures and orthognathic surgery patientsare much less than it is recorded later in the postoper-ative period or in the nonoperated population. Based onthe studies of bite force in postoperative patients, Hauget al.10 postulated that meaningful mechanical behav-iour would be obtained within the ranges of 0 to 100 Nrange for incisal edge loading and 0 to 200 N forcontralateral molar loading, in their biomechanical

evaluation of mandibular angle fracture plating tech-niques with synthetic polyurethane replica mandibles.In the present study, we considered the loads up to 300N, so a 1.75 mm displacement point was used as theend point. This end point was also used in our previousbiomechanical study of plating techniques for fracturesof the mandibular condyle.6

Champy recommended a single noncompressionminiplate ventral to the oblique line for mandibularangle fractures.20 Some clinical studies confirmed theeffectiveness of the Champy thechnique.21-23 In a clin-ical study, Ellis et al.22 evaluated the results in patients

treated for fractures of the mandibular angle with asingle miniplate. They concluded that using a singleminiplate is a simple and reliable technique with arelatively small number of major complications. Al-though this technique has been documented with lowcomplication rates by numerous authors,21-23 it leads toan opening of the lower fracture line, lateral displace-ment of the fragments at the inferior mandibular border,and a posterior open bite on the fracture side.24 Inaddition, this distraction gap can also contribute toinfection.5 The present biomechanical study showedthat Champy technique had less favorable biomechani-

cal behavior than biplanar plate placement and 3Dcurved angle strut plate.

The need for a second miniplate to be applied to thelower border of the mandible has been discussed re-cently.21,25 This method is used to achieve a goodanatomic repositioning and stable fixation of the frac-

ture, in which one plate is applied at the superior borderand a second at the inferior border of the mandible. Itreduces the separation of the fracture line and lateraldisplacement of the lower mandibular border.24 Allbiomechanical tests in which a second miniplate hasbeen fixed to the mandibular margin revealed less mo-bile fracture ends.21,26,27

In the present study, in accordance with the litera-ture, biplanar plate orientation provided greater biome-chanical stability than the monoplanar one. Although2-miniplate fixation of mandibular angle fractures hadmore biomechanical advantages in the present study,

extremely high complication rates are reported in theliterature.27 When using an intraoral approach,2-miniplate fixation technique necessitates reflection ofall soft tissues from the mandible, increasing intraop-erative trauma. When using an extraoral approach toplace the second miniplate on the inferior border, itincreases the risk of bacterial contamination, scarring,postoperative edema, hematoma, and marginal mandib-ular nerve demage. In addition, 2-miniplate fixationprolongs the operation time.

Although the second and third groups were bothfixated with dual miniplates in our study, biplanar plate

orientation provided greater biomechanical stability thanthe monoplanar one. This difference may arise from thelocation of the superior miniplate, which was settledabove the superior oblique ridge. It was previouslyreported that plate placement in biplanar orientation issuperior to monoplanar plate placement when appliedto either a monocortical or a bicortical plating tech-nique.15 Additionally, it is confirmed in the literaturethat greater biomechanical stability is obtained with aminiplate placed obliquely than horizontally.7 In a pre-vious biomechanical study of comparing several fixa-tion methods used in sagittal split osteotomy,7 we

found that the miniplate fixed obliquely with 2 bicor-tical screws in the proximal segment provided the mostbiomechanical stability of the miniplate groups. Ourfindings were in accordance with the literature.

The 3D strut plate is a single plate composed of 2curved miniplates buttressed with perpendicular strutbars.8 Its geometry allows an increased number ofscrews, stability in 3 dimensions, and malleability.4

Strut plates provide increased torsional stability, so it istypically used for symphyseal fractures, which are un-der a greater degree of torsional strain than the otherareas of mandible.2 Feledy et al.8 examinated the utility

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of a single 2.0-mm matrix miniplate for mandibularangle fracture management clinically and compared thestability of it with 2 2.0-mm miniplates in a simulatedfracture setting. The matrix miniplate demonstrated abetter stability and more resistance to fracture move-ment. Clinically, in a series of 22 consecutive patients,

they found no cases of nonunion, malunion, or platefailure. They also recommended that the matrixminiplate provided sufficient stability for fracture heal-ing.8 Guimond et al.4 also confirmed advantages ofthese plates in mandibular angle fractures. In thepresent investigation, we found that 3D curved anglestrut plate technique had more favorable biomechanicalbehavior than the Champy technique. On the otherhand, no significant differences were found biome-chanically between 3D strut plate and dual miniplatefixation techniques.

The present study demonstrated that 3D strut plates

or dual miniplate techniques had greater resistance tocompression loads than the Champy technique, statis-tically. In addition, biplanar plate orientation may pro-vide a more favorable biomechanical behavior thanmonoplanar plate placement.

The authors thank Assoc. Prof. Dr. Vedat Ceyhan fromthe Department of Agricultural Economics, OndokuzMayis University, for his help with statistical analysis.

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Reprint requests:

Dr. Nukhet CelebiDis Hekimligi FakultesiOndokuz Mayis Universitesi55139, Kurupelit, SamsunTurkeynukh@hotmail.com

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