ORIGINAL ARTICLE
Effect of Surgical Treatment of Mandibular Fracture: Electromyographic Analysis, Bite Force, and Mandibular Mobility André Oliveira Pepato, DDS, MS,* Marcelo Palinkas, DDS, MD,† Simone Cecilio Hallak Regalo, DDS, PhD,‡ Eduardo Henrique Pantosso de Medeiros, DDS, MS,* Paulo Batista de Vasconcelos, DDS, MS,‡ Cássio Edvard Sverzut, DDS, PhD,* Selma Siéssere, DDS, PhD,‡ and Alexandre Elias Trivellato, DDS, PhD* Abstract: This study aimed to examine individuals undergoing surgery for the treatment of the fractured mandibular angle, using bite force, mandibular mobility, and electromyographic (EMG) analysis in many different clinical conditions, after 2 months postoperatively. Bite force was recorded with a digital dynamometer, model IDDK. The EMG activity (Myosystem-Br1) included the analysis of the masseter and temporal muscles. Mandibular mobility was measured using a digital pachymeter. The subjects were divided into 3 groups: G1, mandibular angle fracture (n = 7); G2, condylar process fracture (n = 5); and G3, control (n = 12). Data were tabulated and submitted to statistical analysis using the repeated-measure test carried out over time and the Student’s t-test (P < 0.05), using the Statistical Package for the Social Sciences software, version 19 (SPSS Inc, Chicago, IL). G1 and G2 had an increase in bite force. In G1, there was a regular decrease in the EMG activity in the second postoperative month. G2 presented an irregular pattern in EMG data during the period tested. Regarding the mandibular mobility, both groups obtained amplitude of all mandibular movements with a high percentage, when compared with control. A good functional recovery was achieved by the individuals who had a mandible angle fracture or condylar process fracture, after 2 postoperative months. Key Words: Electromyography, bite force, mandibular motion range, mandibular angle fracture, condylar process fracture (J Craniofac Surg 2014;25: 1714–1720)
The fractures that affect the mandibular angle and condyle are common in modern society with an incidence ranging from 23% to 42% among all mandibular fractures.2–9 The functional restriction of the mandibular due to fracture can be very harmful to an individual. The functions performed by this structure, such as speaking, chewing, and swallowing, should be quickly recovered to improve the quality of life.10 Many concepts can involve the management of mandibular fractures; however, there are controversies about the most adequate treatment made up of arguments based on the surgeon’s affinity with the technique used rather than on scientific information.7–11 The behavior analysis of trauma to the skeletal muscle after surgical treatment using internal fixation is of great value to uncover and clarify the changes suffered in the masticatory system that may involve mandibular mobility, muscular activity, and masticatory force as well as indicate the method of a successful, individualized treatment.12 The behavior analysis of the individuals with dentoskeletal trauma, after a surgical treatment using internal fixation, helps reveal and explain the changes, which occur in the masticatory system involving the mandibular mobility, the muscular activity, and the bite force, and determine a successful method for an individualized treatment. The analysis and diagnosis of muscle function have been performed by different methodologies, with a special focus on electromyogram (EMG), which can be used to detect and record the electrical activity of skeletal muscle fibers, showing when a muscle is activated and also determining the coordination of muscle action in the masticatory process in posttrauma follow-up.13–15
T
he mandible is the second region of the maxillofacial skeleton most commonly fractured because of its position, prominence, thin bone thickness in cross section, and the presence of third molars.1
From the Departments of *Oral, Maxillofacial Surgery and Periodontology, †Restorative Dentistry, and ‡Morphology, Stomatology and Basic Pathology, School of Dentistry of Ribeirão Preto, University of São Paulo, Sao Paulo, Brazil. Received November 13, 2013. Accepted for publication March 13, 2014. Address correspondence and reprint requests to Marcelo Palinkas, DDS, MD, Avenida do Café, s/n- Campus University of São Paulo, 14040-904 Ribeirão Preto, Sao Paulo, Brazil; E-mail: [email protected] The authors report no conflicts of interest. Copyright © 2014 by Mutaz B. Habal, MD ISSN: 1049-2275 DOI: 10.1097/SCS.0000000000000968
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FIGURE 1. Preoperative examination image of the mandibular angle fracture.
The Journal of Craniofacial Surgery • Volume 25, Number 5, September 2014
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
The Journal of Craniofacial Surgery • Volume 25, Number 5, September 2014
Effect of Mandibular Fracture Surgery
FIGURE 2. Preoperative examination image of the condylar process fracture.
A gap should be filled regarding the evaluation and understanding of the masticatory muscle behavior in facial trauma situations and as a result of the various forms of treatment and different surgical procedures used. Therefore, with a better understanding of these aspects, it is possible to combine a more suitable surgical treatment with a faster functional recovery for the individual subjected to trauma.
MATERIALS AND METHODS Sample
FIGURE 4. Postoperative radiographic image of the mandibular angle.
associated with MAFs in G1 was possible because there was no statistically significant difference from the subjects sustaining MAFs alone. The control group, consisting of 12 individuals (6 males and 6 females), with an average age of 20 years, was composed with the exclusive purpose of obtaining reference normality values to verify the progress of the patients submitted to surgery after facial trauma.
Surgical Procedure
Patients were informed about the purposes and stages of the study, and they all provided written consent form previously approved by the Brazilian National Council of Health (process no. 2007.1.1371.58.2) in accordance with Resolution 466/12. The study protocol was consistent with the tenets of the Declaration of Helsinki. To participate in this research, the patients necessarily followed the following criteria: unilateral condylar process fractures (CPFs), or isolated mandibular angle fractures (MAFs) associated or not with symphysis fractures or parasymphysis fractures treated surgically with rigid internal fixation, normo-occlusion, absence of braces, without temporomandibular dysfunction, presence of all teeth (except third molars), no comorbidities, not presenting extensive excoriations and lacerations on the face, and no limitation of mouth opening. The treated patients were divided into 2 groups: G1 (MAF group) with MAFs associated or not with symphysis or parasymphysis fractures with 7 patients (6 males and 1 female) with an average age of 24.1 years and G2 (CPF group) with unilateral CPFs with 5 patients (4 males and 1 female) with an average age of 27.4 years. The inclusion of patients sustaining symphysis or parasymphysis fractures
All the surgeries were performed by the same team of the Department of Oral and Maxillofacial Surgery from the School of Dentistry of Ribeirão Preto, University of São Paulo, in Santa Casa Hospital, with general anesthesia. Fractures were diagnosed through clinical assessment and radiographic or magnetic resonance images (Figs. 1, 2). The unilateral CPFs in the G2-CPF were classified according the study of Ellis et al.12 The retromandibular approach was used when the isolated condylar process fractures were present, and only intraoral approaches were used in cases of MAFs associated or not with symphysis or parasymphysis fractures. All MAFs were treated according to the Champy technique, and fracture fixation was performed using 1 non–compressive bone plate system (Neortho; Curitiba, Paraná, Brazil), specifically with the size of 2.0 mm. Additional symphysis or parasymphysis fractures were fixed by two 2-0 mm system non– compressive bone plates (Figs. 3, 4). The surgical technique for the CPF was the same in all cases. The fractures were fixed using 2 bone plates without compression and 2.0-mm screws (Figs. 5, 6). After the surgery, nonsteroidal anti-inflammatory drugs and analgesics were prescribed for 3 days. The patients were discharged from the hospital
FIGURE 3. Postoperative image of the mandibular angle.
FIGURE 5. Surgical image of the CPF.
© 2014 Mutaz B. Habal, MD
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
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FIGURE 8. Pachymeter Mitutoyo.
FIGURE 6. Postoperative radiographic image of the condylar process.
on the first day after the surgery. Liquid diet was recommended during the first 2 weeks, followed by soft diet for the next third and fourth weeks. General diet was allowed after the fourth week postoperatively.
Bite Force, Electromyographic Data, and Mandibular Mobility In the first place, all patients were submitted to a clinical examination to analyze the postoperative clinical progress. Next, the patients were referred to the EMG laboratory of the Department of Physiology, Stomatology and Basic Pathology, University of São Paulo for EMG examinations, bite-force measurements, and analyses of mandibular mobility. These clinical data were obtained every postoperative week in the first month, and another assessment was performed when the second month postoperative data were achieved. The EMG data and bite-force measurements were collected with the patients sitting on a comfortable chair (office-like), with the arms extended along the body and the hands lying on their thighs. The maximal molar bite force was captured using a digital dynamometer, model IDDK (Kratos; Cotia, Sao Paulo, Brazil), with a 1000-N capacity, adapted to the oral cavity (Fig. 7). The dynamometer has a high-precision charge cell and electronic circuit to indicate the force and supply precise measurements, easily viewed on a digital display. The biosecurity control was applied when the 2 rods with plastic disks on each end of the dynamometer were
FIGURE 7. Dynamometer, model IDDK.
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cleaned with alcohol and disposable latex finger cots covered it (Wariper; Cambuci, Sao Paulo, Brazil). Detailed instructions were given to the patients, and bite tests were performed on the first molar (both sides) and central incisors regions before the recordings were made to ensure the reliability of the procedure. Then, the patients were asked to bite the dynamometer 3 times with maximum molar bite force, with a 2-minute rest interval. The values of maximum bite force were obtained from the averages of these values. Digital pachymeter (Mitutoyo, Santo Amaro, São Paulo, Brazil) was used to measure the mandibular mobility (Fig. 8), considering the maximum standards for mouth opening as well as the right and left lateral movement and protrusion. The Myosystem-Br1 apparatus (DataHomins Ltda, Uberlândia, Minas Gerais, Brazil) was used to evaluate the EMG activity of the masticatory muscles bilaterally. The electrodes were positioned in the ventral region of masseter and the anterior portion of temporal muscles, and a stainless-steel circular electrode was also used as a reference electrode, adhered to the skin over the frontal bone region (Fig. 9). The EMG data were analogically amplified with a gain of 1000 filtered with a pass band of 0.01 to 1.5 kHz and sampled by a 12-bit analog-to-digital converter with a 2-kHz sampling rate. The signals were digitally filtered with a pass-band filter of 10 to 500 Hz during the data processing. Surface differential active electrodes (two 10-mm–long and 2-mm–wide silver chloride bars, separated by a distance of 10 mm with an input impedance of 10 G and a common-mode rejection ratio of 130 dB at 60 Hz) were used in the study. The skin region where electrodes were placed was cleaned with alcohol and shaved when necessary to eliminate pollution or oily residues, which could interfere with the results of the research.
FIGURE 9. Myosystem-BR1.
© 2014 Mutaz B. Habal, MD
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
The Journal of Craniofacial Surgery • Volume 25, Number 5, September 2014
difference was found when the mean bite forces of fractured and nonfractured sides were compared in the first and last evaluations, regardless of the group. Regarding the EMG activity, in G1, the values were higher in the former evaluation and declining throughout the study period. This pattern of activity occurred for the masseter and temporal muscles bilaterally in the evaluations, at rest and during posture movements. Conversely, in G2, the values followed a different and, to some extent, irregular pattern. The EMG activity for both temporal muscles reassumed a higher value in the second month in the evaluation at rest, opening and closing, as well as the right and left laterality and protrusion. No statistically significant difference was found when comparing the EMG activity of the fractured and nonfractured sides, regardless of the group (Tables 2, 3). Mandibular motion range was almost fully recovered by G1 (MAF) at the second postoperative month. The mean of the mouth opening represented 92.64% of the value obtained by the control group and right laterality achieved 91.65%. In addition, the left laterality and protrusion fully recovered the normal values. G2 (CPF) achieved 81.1% for mouth opening and 89.66% for the right laterality. The left laterality was fully recovered at the second month; however, protrusion was only 74.36% of the value obtained by the control group (Tables 4, 5).
TABLE 1. Mean Bite Force Measurements (N) of G1 and G2 in the 2-Month Period G1 (MAF) Time 1 wk 2 wk 3 wk 4 wk 2 mo Control Significance
Right Molar 51 111 161 171 261 540
G2 (CPF)
Left Molar
± 1.78 ± 2.17 ± 2.50 ± 2.75 ± 5.20 ± 7.68 *
Right Molar
80 ± 2.30 120 ± 2.17 171 ± 4.53 210 ± 3.75 301 ± 6.14 590 ± 8.45 *
200 220 250 280 290 540
Left Molar
± 4.56 ± 3.60 ± 3.10 ± 6.76 ± 5.88 ± 7.68 *
Effect of Mandibular Fracture Surgery
210 ± 3.20 340 ± 5.65 320 ± 2.36 320 ± 8.17 340 ± 6.73 590 ± 8.45 *
The asterisk symbol denotes significance for P < 0.05.
The muscular activity was evaluated using EMG recordings of the masseter and temporal muscles, bilaterally, at rest (5 s), opening and closing of the mouth (5 s), right and left laterality (5 s), protrusion (5 s) as well as dental clenching with a sheet of paraffin (Parafilm M; Pechinery Plastic Packaging, Batavia, IL) and clenching in maximum voluntary contraction (4 s). Data were normalized by clenching in the maximum voluntary contraction.
RESULTS
DISCUSSION
Data were tabulated and submitted to statistical analysis using independent-samples t-test and repeated-measures test (Statistical Package for the Social Sciences software 19.0, Chicago, IL). A 95% level of significance (P < 0.05) was adopted. In the mean bite force in all measured regions, compared with the regions of the right molars, those on the left side increased during the 2-month period for both groups, with a statistically significant difference (P < 0.05) over a period (Table 1). No statistically significant
The quantitative assessment of the strength of mandibular elevator muscles is a well-recognized clinical parameter16; also, maximum occlusal force is one parameter of masticatory function that is relatively easy to measure.17 In healthy subjects and in patients, significant relationships between occlusal forces and facial morphology have been found; in patients, occlusal forces are related to dental conditions, the kind of prosthetic reconstruction, the presence of temporomandibular and craniomandibular disorders, or
TABLE 2. Mean Normalized EMG Measurements of the Muscles RM, LM, RT, and LT for G1 (MAF) in the 2-Month Period for R and the Clinical Conditions, O/C, RL, LL, and P Period Clinical Conditions
R
O/C
RL
LL
P
Muscle RM LM RT LT RM LM RT LT RM LM RT LT RM LM RT LT RM LM RT LT
1 Wk 0.35 0.56 0.56 0.43 0.47 0.68 0.54 0.51 0.48 0.73 0.66 0.43 0.41 0.62 0.57 0.53 0.46 0.64 0.55 0.47
± 0.11 ± 0.14 ± 0.16 ± 0.09 ± 0.12 ± 0.20 ± 0.15 ± 0.10 ± 0.18 ± 0.14 ± 0.14 ± 0.08 ± 0.14 ± 0.16 ± 0.16 ± 0.08 ± 0.14 ± 0.15 ± 0.14 ± 0.09
2 Wk 0.17 0.31 0.43 0.33 0.31 0.46 0.51 0.39 0.55 0.42 0.77 0.37 0.19 0.40 0.70 0.49 0.27 0.42 0.58 0.34
± 0.05 ± 0.07 ± 0.14 ± 0.11 ± 0.09 ± 0.10 ± 0.16 ± 0.15 ± 0.36 ± 0.13 ± 0.24 ± 0.14 ± 0.05 ± 0.10 ± 0.21 ± 0.13 ± 0.05 ± 0.10 ± 0.20 ± 0.13
3 Wk 0.16 0.19 0.44 0.32 0.25 0.27 0.42 0.37 0.21 0.30 0.48 0.35 0.15 0.20 0.41 0.35 0.24 0.26 0.40 0.29
± 0.08 ± 0.06 ± 0.17 ± 0.08 ± 0.08 ± 0.10 ± 0.14 ± 0.09 ± 0.08 ± 0.12 ± 0.17 ± 0.10 ± 0.06 ± 0.05 ± 0.14 ± 0.07 ± 0.09 ± 0.08 ± 0.13 ± 0.06
4 Wk
2 Mo
0.17 ± 0.08 0.20 ± 0.06 0.35 ± 0.09 0.21 ± 0.05 0.25 ± 0.06 0.31 ± 0.06 0.48 ± 0.10 0.33 ± 0.09 0.26 ± 0.09 0.30 ± 0.09 0.49 ± 0.14 0.26 ± 0.10 0.16 ± 0.05 0.22 ± 0.06 0.38 ± 0.10 0.29 ± 0.09 0.35 ± 0.12 0.48 ± 0.19 0.39 ± 0.12 0.23 ± 0.07
0.10 ± 0.04 0.08 ± 0.01 0.22 ± 0.76 0.13 ± 0.03 0.25 ± 0.11 0.15 ± 0.04 0.35 ± 0.13 0.21 ± 0.08 0.14 ± 0.06 0.19 ± 0.08 0.27 ± 0.09 0.16 ± 0.06 0.08 ± 0.01 0.10 ± 0.02 0.19 ± 0.06 0.18 ± 0.04 0.13 ± 0.01 0.16 ± 0.06 0.19 ± 0.07 0.12 ± 0.03
Control 0.07 ± 0.09 ± 0.09 ± 0.13 ± 0.15 ± 0.17 ± 0.17 ± 0.19 ± 0.11 ± 0.13 ± 0.19 ± 0.13 ± 0.12 ± 0.10 ± 0.19 ± 0.19 ± 0.11 ± 0.16 ± 0.11 ± 0.11 ±
0.01 0.01 0.01 0.01 0.29 0.03 0.03 0.02 0.02 0.03 0.08 0.01 0.02 0.01 0.04 0.04 0.01 0.04 0.02 0.01
Significance * * NS * NS * NS * NS * NS NS * * * * * * * *
The asterisk symbol denotes significance for P < 0.05; NS, not significant for P < 0.05. LL, left laterality; LM, left masseter; LT, left temporal; NS, not significant for P < 0.05; O/C, opening/closing; P, protrusion; R, rest mandibular; RL, right laterality; RM, right masseter; RT, right temporal.
© 2014 Mutaz B. Habal, MD
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
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TABLE 3. Mean Normalized EMG Measurements of the Muscles RM, LM, RT, and LT for G2 (CPF) in the 2-Month Period for R and the Clinical Conditions, O/C, RL, LL, and P Period Clinical Conditions
R
O/C
RL
LL
P
Muscle RM LM RT LT RM LM RT LT RM LM RT LT RM LM RT LT RM LM RT LT
1 Wk 0.26 0.31 0.26 0.14 0.34 0.48 0.51 0.18 0.23 0.36 0.24 0.12 0.33 0.41 0.29 0.14 0.25 0.40 0.26 0.12
2 Wk
± 0.10 ± 0.12 ± 0.09 ± 0.02 ± 0.12 ± 0.23 ± 0.25 ± 0.03 ± 0.10 ± 0.17 ± 0.06 ± 0.02 ± 0.19 ± 0.17 ± 0.08 ± 0.02 ± 0.10 ± 0.17 ± 0.08 ± 0.02
0.16 0.17 0.34 0.11 0.32 0.43 0.39 0.18 0.17 0.23 0.35 0.11 0.21 0.20 0.34 0.16 0.28 0.43 0.33 0.12
3 Wk
± 0.06 ± 0.05 ± 0.16 ± 0.02 ± 0.10 ± 0.17 ± 0.16 ± 0.07 ± 0.07 ± 0.09 ± 0.13 ± 0.03 ± 0.08 ± 0.07 ± 0.16 ± 0.04 ± 0.11 ± 0.17 ± 0.16 ± 0.03
0.11 0.14 0.13 0.14 0.21 0.27 0.17 0.24 0.42 0.23 0.18 0.13 0.15 0.15 0.14 0.19 0.24 0.24 0.15 0.10
± 0.03 ± 0.02 ± 0.02 ± 0.03 ± 0.04 ± 0.06 ± 0.02 ± 0.09 ± 0.19 ± 0.04 ± 0.05 ± 0.03 ± 0.02 ± 0.01 ± 0.01 ± 0.04 ± 0.08 ± 0.05 ± 0.01 ± 0.02
4 Wk
2 Mo
0.10 ± 0.03 0.13 ± 0.05 0.15 ± 0.05 0.11 ± 0.03 0.29 ± 0.09 0.43 ± 0.19 0.17 ± 0.04 0.18 ± 0.06 0.17 ± 0.08 0.18 ± 0.05 0.17 ± 0.05 0.09 ± 0.02 0.14 ± 0.02 0.16 ± 0.04 0.15 ± 0.04 0.16 ± 0.04 0.20 ± 0.03 0.31 ± 0.10 0.13 ± 0.03 0.12 ± 0.02
0.12 ± 0.04 0.11 ± 0.04 0.30 ± 0.19 0.18 ± 0.06 0.22 ± 0.04 0.29 ± 0.10 0.41 ± 0.16 0.25 ± 0.06 0.15 ± 0.05 0.27 ± 0.11 0.53 ± 0.36 0.17 ± 0.06 0.17 ± 0.05 0.19 ± 0.05 0.27 ± 0.15 0.23 ± 0.06 0.29 ± 0.05 0.38 ± 0.18 0.29 ± 0.15 0.20 ± 0.11
Control 0.07 ± 0.09 ± 0.09 ± 0.13 ± 0.15 ± 0.17 ± 0.17 ± 0.19 ± 0.11 ± 0.13 ± 0.19 ± 0.13 ± 0.12 ± 0.10 ± 0.19 ± 0.19 ± 0.11 ± 0.16 ± 0.11 ± 0.11 ±
0.06 0.01 0.01 0.01 0.29 0.03 0.03 0.02 0.02 0.03 0.08 0.01 0.02 0.01 0.04 0.04 0.01 0.04 0.02 0.01
Significance * * NS * NS * NS NS * * * * NS NS NS NS * * NS NS
The asterisk symbol denotes significance for P < 0.05; NS, not significant for P < 0.05.
fractures of the bones involved in the masticatory apparatus. In addition, significant relationships between occlusal force and masticatory performance have been demonstrated.16 Bite force evaluation revealed a gradual increase from postoperative measurements to the second month postoperatively in G1 (MAF) in agreement with the study of Tate et al.10 These studies found that, at 6 weeks postoperatively, values close to 50% to 60% of molar force were obtained within a control group. Similarly, the G1 (MAF) at 2 months postoperatively achieved values close to 50% of bite force compared with the control group. In addition, the control group examined by Gerlach and Schwarz18 could only generate approximately 176 N, 245 N, and 205 N at the central incisors, left molar, and right molar, respectively. In the current study, the values of mandibular motion range for the G1 (MAF) were within the reference levels during the first week postoperatively; conversely, G2 (CPF) achieved values close to 80% of that presented by the control group only at the second month postoperatively. Throckmorton and Ellis19 found that, at 6 weeks after unilateral CPFs treated by open or closed technique, all patients’ excursive movements were significantly smaller than those of controls. Palmieri et al20 investigated unilateral CPFs treated either by open and closed techniques. They found that, at 6 weeks postoperatively, the patients treated by closed methods
had an average of 4.4-mm greater interincisal dimension than did the patients treated by open methods. However, this same investigation showed little difference in mandibular motion between the groups from 6 weeks to 3 years after the injury. We agree with the authors that some hipomobility may be caused by joint and incisional pain or possibly because scarring occurred during healing of the surgical site. Electromyography as a method of analyzing muscle function has evolved over the last 50 years. Most extensively used in EMG are the surface electrodes. Surface electrodes are readily available and easily applied and free of discomfort.21 By means of surface EMG, Ribeiro et al22 evaluated the isolated fractures of the zygomatico-orbital complex. These authors observed an increase in EMG activity for the right masseter as well as the left and right temporal muscles and a decrease in EMG activity for the left masseter muscle when compared with the control group. The authors concluded that the EMG activity values decreased until the sixth month after surgery, after which the normal pattern was reestablished. During maximum voluntary teeth clenching, the temporalis muscles are given the function of stabilization action, whereas the masseter muscles perform the main clench activity.22 Moreover, an imbalance of the left-right standardized activity may result in
TABLE 4. Mean Mandibular Motion Range Measurements of G1 (MAF) in the 2-Month Period 1 Wk Mouth opening Right laterality Left laterality Protrusion
25.60 5.15 6.08 2.93
± 2.37 ± 0.69 ± 0.78 ± 0.30
2 Wk 29.25 6.43 7.47 3.74
± 2.60 ± 1.30 ± 0.68 ± 0.37
3 Wk 35.12 7.92 8.40 4.31
± 3.71 ± 1.50 ± 0.76 ± 0.51
4 Wk 38.64 8.49 8.59 5.79
± 3.95 ± 1.29 ± 0.73 ± 0.78
2 Mo 45.25 8.15 8.48 6.70
± 3.08 ± 1.32 ± 0.67 ± 0.57
Control
Significance
48.8 ± 1.47 8.9 ± 0.54 8.32 ± 0.61 4.71 ± 0.41
* * * *
All values are expressed as millimeters. The asterisk symbol denotes significance for P < 0.05.
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© 2014 Mutaz B. Habal, MD
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
The Journal of Craniofacial Surgery • Volume 25, Number 5, September 2014
Effect of Mandibular Fracture Surgery
TABLE 5. Mean Mandibular Motion Range Measurements of G2 (CPF) in the 2-Month Period 1 Wk Mouth opening Right laterality Left laterality Protrusion
22.43 5.35 5.43 2.15
± 1.43 ± 0.83 ± 1.46 ± 0.98
2 Wk
3 Wk
4 Wk
24.37 ± 2.02 5.30 ± 0.76 7.50 ± 1.54 1.94 ± 0.92
25.75 ± 0.84 5.22 ± 1.12 9.02 ± 1.25 1.31 ± 0.62
28.99 ± 1.56 7.40 ± 1.28 7.18 ± 1.51 3.43 ± 1.21
2 Mo 39.62 7.98 9.00 3.50
± 2.37 ± 0.93 ± 1.03 ± 0.76
Control
Significance
48.85 ± 1.47 8.9 ± 0.54 8.32 ± 0.61 4.71 ± 0.41
* * * *
All values are expressed as millimeters. The asterisk symbol denotes significance for P < 0.05.
abnormal loads over the temporomandibular joints. Neuromuscular adaptations occur within the masticatory system after bilateral fractures of the mandibular condylar processes.5 According to these authors, individuals with bilateral CPFs selectively increase the EMG output in the posterior temporalis fibers. The effect of this increased activity is to provide a posteriorly directed vector onto the coronoid process, which, all other things being equal, can rotate the anterior portion of the mandible superiorly, bringing the incisors into contact. In addition, the authors affirm that these neuromuscular adaptations are called into play to position the mandible early after injury.23 Thus, the only mechanism whereby the mandible can be positioned into a normal occlusal relationship early after injury is by complex neuromuscular adaptations in the muscles of mastication. The temporalis muscle has the predominant role in the balancing of the mandibular movements. The muscle determines the muscular tone in the postural jaw position, and it has to do more with speed function than with force.15 The temporal muscle contracts at closure of the mouth, being considered a positioner of the mandibular condyle24 by adjusting the direction of the movements with better synchronization. Ahlgren et al,25 using needle EMG, reported that the middle and posterior portions of the temporal muscle in postural resting condition showed EMG activity, whereas the anterior portion was found to be inactive, allowing mandibular stability in healthy subjects. In traumatic situations such as condylar fracture and jaw surgery, the individual stress may appear and lead to functional changes of the masticatory muscles, promoting muscle hyperactivity,26 which was observed in this work with our results, where the G1 values were higher in the first evaluation and declining throughout the study period. In this study, we found a decreased EMG activity in the temporal muscles bilaterally at the second month postoperatively in both temporal muscles. Besides, we believe that, despite the vertical height reestablishment after open surgery, these neuromuscular adaptations still occur in CPF by traumatic or operative trauma to the masseter muscles and to protective neuromuscular mechanisms of masticatory system (splinting components are activated or deactivated to take forces of the damaged bone). Interestingly, we observed that, while comparing the fractured side versus the nonfractured side separately, there were no statistically significant differences in the molar bite force mean and on the EMG activity. This behavior makes the authors expect bilateral masticatory muscles’ protective neuromuscular mechanisms, not considering the side of the fracture. Both current groups of subjects achieved good functional recovery in mandibular motion range. Every bite force measurement was approximately 50% to 55% of the control group except for the incisor bite force in G2 (CPF). In addition, EMG activity indices measured in the G1 (MAF) subjects declined almost in a linear pattern until the second month; however, G2 (CPF) assumed a more irregular pattern, especially for the temporal muscles. In EMG averages and maximum bite force analysis of the patients in groups G1 (MAF) and G2 (CPF) as well as the comparison of the right and
left sides (all periods), higher values for the nonfractured sides were found, but this difference was not statistically significant and the results were in agreement with those in the study of Richardson et al,27 where no statically significant difference was found when comparing the bite force and EMG activity of fractured and nonfractured sides, regardless of the group. This is probably caused by the fact the technique of fixation of condylar fractures of the mandibular angle has the ability to restore balance and function of the stomatognathic system.28 The authors agree that this study should be repeated with a large sample and with a larger longitudinal assessment during subsequent healing phases. On the basis of this study, the authors concluded that a good functional recovery was achieved by the individuals who had a mandible angle fracture or condylar process fracture, after 2 postoperative months. ACKNOWLEDGMENTS The authors thank the State of São Paulo Foundation (FAPESP) for technical, scientific, and financial support, which were essential for this study (process no. 2007.1.1371.58.2).
REFERENCES 1. Ogundare BO, Bonnick A, Bayley N. Pattern of mandibular fractures in an urban major trauma center. J Oral Maxillofac Surg 2003;61:713–718 2. Schierle HP, Schmelzeisen R, Rahn B, et al. One- or two-plate fixation of mandibular angle fractures? J Craniomaxillofac Surg 1997;25:162–168 3. Fox AJ, Kellman RM. Mandible angle fractures: two-miniplate fixation and complications. Arch Facial Plast Surg 2003;5:464–469 4. Gabrielli MAC, Gabrielli MFR, Marcantonio E, et al. Fixation of mandibular fractures with 2.0-mm miniplates: review of 191 cases. J Oral Maxillofac Surg 2003;61:430–436 5. Ellis E3rd, Throckmorton GS. Treatment of mandibular condylar process fractures: biological considerations. J Oral Maxillofac Surg 2005;63:115–134 6. Brasileiro BF, Passeri LA. Epidemiological analysis of maxillofacial fractures in Brazil: a 5-year prospective study. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2006;1:28–34 7. Ellis E3rd. Management of fractures through the angle of the mandible. Oral Maxillofac Surg Clin North Am 2009;21:163–174 8. de Matos FP, Arnez MFM, Sverzut CE, et al. A retrospective study of mandibular fracture in a 40-month period. Int J Oral Maxillofac Surg 2010;39:10–15 9. Shen L, Li P, Li J, et al. Management of superolateral dislocation of the mandibular condyle: a retrospective study of 10 cases. J Craniomaxillofac Surg 2014;42:53–58 10. Tate GS, Ellis E3rd, Throckmorton G. Bite forces in patients treated for mandibular angle fractures: implications for fixation recommendations. J Oral Maxillofac Surg 1994;52:734–736 11. Gear AJ, Apasova E, Schmitz JP, et al. Treatment modalities for mandibular angle fractures. J Oral Maxillofac Surg 2005;63:655–663
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12. Ellis E 3rd, Throckmorton GS, Palmieri C. Open treatment of condylar process fractures: assessment of adequacy of repositioning and maintenance of stability. J Oral Maxillofac Surg 2000;58:27–34 13. Bither S, Mahindra U, Halli R, et al. Electromyographic analysis of anterior temporalis and superficial masseter muscles in mandibular angle fractures—a pilot study. Oral Maxillofac Surg 2012;16:299–304 14. De Rossi M, Santos CM, Migliorança R,et al. All on Four Fixed Implant Support Rehabilitation: a masticatory function study. Clin Implant Dent Relat Res [published ahead of print January 10, 2013] doi: 10.1111/cid.12031 15. Cecílio FA, Regalo SC, Palinkas M, et al. Ageing and surface EMG activity patterns of masticatory muscles. J Oral Rehabil 2010;37:248–255 16. Ferrario VF, Sforza C, Zanotti G, et al. Maximal bite forces in healthy young adults as predicted by surface electromyography. J Dent 2004;32:451–457 17. Ellis E3rd, Throckmorton GS. Bite forces after open and close treatment of mandibular condylar process fractures. J Oral Maxillofac Surg 2001;59:389–395 18. Gerlach KL, Schwarz A. Bite forces in patients after treatment of mandibular angle fractures with miniplate osteosynthesis according to Champy. Int J Oral Maxillofac Surg 2002;31:345–358 19. Throckmorton GS, Ellis E3rd. Recovery of mandibular motion after closed and open treatment of unilateral mandibular condylar process fractures. Int J Oral Maxillofac Surg 2000;29:421–427 20. Palmieri C, Ellis E3rd, Throckmorton G. Mandibular motion after closed and open treatment of unilateral mandibular condylar process fractures. J Oral Maxillofac Surg 1999;57:764–775
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21. Soderberg GL, Knutson LM. A guide for use and interpretation of kinesiologic electromyographic data. Phys Ther 2000;80:485–498 22. Ribeiro MC, Regalo SC, Pepato AO, et al. Bite force, electromyography, and mandible mobility during the 6-month period after surgical treatment for isolated fractures of the zygomatico-orbital complex. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2011;111:e1–e7 23. Sforza C, Tartaglia GM, Lovecchio N. Mandibular movements at maximum mouth opening and EMG activity of masticatory and neck muscles in patients rehabilitated after a mandibular condyle fracture. J Craniomaxillofac Surg 2009;37:327–333 24. Rancan SV, Bataglion C, Bataglion SA, et al. Acupuncture and temporomandibular disorders: a 3-month follow-up EMG study. J Altern Complement Med 2009;15:1307–1310 25. Ahlgren J, Sonesson B, Blitz M. An electromyographic analysis of the temporalis function of normal occlusion. Am J Orthod 1985;87:230–239 26. Pepato AO, Palinkas M, Regalo SCH, et al. Analysis of masticatory efficiency by electromyographic activity of masticatory muscles after surgical treatment of zygomatic-orbital complex fractures. Int J Stomatol Occlusion Med 2013;6:85–90 27. Richardson K, Gonzalez Y, Crow H, et al. The effect of oral motor exercises on patients with myofascial pain of masticatory system. Case series report. N Y State Dent J 2012; 78:32–37 28. Ghazal G, Jaquiéry C, Hammer B. Non-surgical treatment of mandibular fractures—survey of 28 patients. J Oral Maxillofac Surg 2004;33:141–145
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Effect of Surgical Treatment of Mandibular Fracture: Electromyographic Analysis, Bite Force, and Mandibular Mobility André Oliveira Pepato, DDS, MS,* Marcelo Palinkas, DDS, MD,† Simone Cecilio Hallak Regalo, DDS, PhD,‡ Eduardo Henrique Pantosso de Medeiros, DDS, MS,* Paulo Batista de Vasconcelos, DDS, MS,‡ Cássio Edvard Sverzut, DDS, PhD,* Selma Siéssere, DDS, PhD,‡ and Alexandre Elias Trivellato, DDS, PhD* Abstract: This study aimed to examine individuals undergoing surgery for the treatment of the fractured mandibular angle, using bite force, mandibular mobility, and electromyographic (EMG) analysis in many different clinical conditions, after 2 months postoperatively. Bite force was recorded with a digital dynamometer, model IDDK. The EMG activity (Myosystem-Br1) included the analysis of the masseter and temporal muscles. Mandibular mobility was measured using a digital pachymeter. The subjects were divided into 3 groups: G1, mandibular angle fracture (n = 7); G2, condylar process fracture (n = 5); and G3, control (n = 12). Data were tabulated and submitted to statistical analysis using the repeated-measure test carried out over time and the Student’s t-test (P < 0.05), using the Statistical Package for the Social Sciences software, version 19 (SPSS Inc, Chicago, IL). G1 and G2 had an increase in bite force. In G1, there was a regular decrease in the EMG activity in the second postoperative month. G2 presented an irregular pattern in EMG data during the period tested. Regarding the mandibular mobility, both groups obtained amplitude of all mandibular movements with a high percentage, when compared with control. A good functional recovery was achieved by the individuals who had a mandible angle fracture or condylar process fracture, after 2 postoperative months. Key Words: Electromyography, bite force, mandibular motion range, mandibular angle fracture, condylar process fracture (J Craniofac Surg 2014;25: 1714–1720)
The fractures that affect the mandibular angle and condyle are common in modern society with an incidence ranging from 23% to 42% among all mandibular fractures.2–9 The functional restriction of the mandibular due to fracture can be very harmful to an individual. The functions performed by this structure, such as speaking, chewing, and swallowing, should be quickly recovered to improve the quality of life.10 Many concepts can involve the management of mandibular fractures; however, there are controversies about the most adequate treatment made up of arguments based on the surgeon’s affinity with the technique used rather than on scientific information.7–11 The behavior analysis of trauma to the skeletal muscle after surgical treatment using internal fixation is of great value to uncover and clarify the changes suffered in the masticatory system that may involve mandibular mobility, muscular activity, and masticatory force as well as indicate the method of a successful, individualized treatment.12 The behavior analysis of the individuals with dentoskeletal trauma, after a surgical treatment using internal fixation, helps reveal and explain the changes, which occur in the masticatory system involving the mandibular mobility, the muscular activity, and the bite force, and determine a successful method for an individualized treatment. The analysis and diagnosis of muscle function have been performed by different methodologies, with a special focus on electromyogram (EMG), which can be used to detect and record the electrical activity of skeletal muscle fibers, showing when a muscle is activated and also determining the coordination of muscle action in the masticatory process in posttrauma follow-up.13–15
T
he mandible is the second region of the maxillofacial skeleton most commonly fractured because of its position, prominence, thin bone thickness in cross section, and the presence of third molars.1
From the Departments of *Oral, Maxillofacial Surgery and Periodontology, †Restorative Dentistry, and ‡Morphology, Stomatology and Basic Pathology, School of Dentistry of Ribeirão Preto, University of São Paulo, Sao Paulo, Brazil. Received November 13, 2013. Accepted for publication March 13, 2014. Address correspondence and reprint requests to Marcelo Palinkas, DDS, MD, Avenida do Café, s/n- Campus University of São Paulo, 14040-904 Ribeirão Preto, Sao Paulo, Brazil; E-mail: [email protected] The authors report no conflicts of interest. Copyright © 2014 by Mutaz B. Habal, MD ISSN: 1049-2275 DOI: 10.1097/SCS.0000000000000968
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FIGURE 1. Preoperative examination image of the mandibular angle fracture.
The Journal of Craniofacial Surgery • Volume 25, Number 5, September 2014
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
The Journal of Craniofacial Surgery • Volume 25, Number 5, September 2014
Effect of Mandibular Fracture Surgery
FIGURE 2. Preoperative examination image of the condylar process fracture.
A gap should be filled regarding the evaluation and understanding of the masticatory muscle behavior in facial trauma situations and as a result of the various forms of treatment and different surgical procedures used. Therefore, with a better understanding of these aspects, it is possible to combine a more suitable surgical treatment with a faster functional recovery for the individual subjected to trauma.
MATERIALS AND METHODS Sample
FIGURE 4. Postoperative radiographic image of the mandibular angle.
associated with MAFs in G1 was possible because there was no statistically significant difference from the subjects sustaining MAFs alone. The control group, consisting of 12 individuals (6 males and 6 females), with an average age of 20 years, was composed with the exclusive purpose of obtaining reference normality values to verify the progress of the patients submitted to surgery after facial trauma.
Surgical Procedure
Patients were informed about the purposes and stages of the study, and they all provided written consent form previously approved by the Brazilian National Council of Health (process no. 2007.1.1371.58.2) in accordance with Resolution 466/12. The study protocol was consistent with the tenets of the Declaration of Helsinki. To participate in this research, the patients necessarily followed the following criteria: unilateral condylar process fractures (CPFs), or isolated mandibular angle fractures (MAFs) associated or not with symphysis fractures or parasymphysis fractures treated surgically with rigid internal fixation, normo-occlusion, absence of braces, without temporomandibular dysfunction, presence of all teeth (except third molars), no comorbidities, not presenting extensive excoriations and lacerations on the face, and no limitation of mouth opening. The treated patients were divided into 2 groups: G1 (MAF group) with MAFs associated or not with symphysis or parasymphysis fractures with 7 patients (6 males and 1 female) with an average age of 24.1 years and G2 (CPF group) with unilateral CPFs with 5 patients (4 males and 1 female) with an average age of 27.4 years. The inclusion of patients sustaining symphysis or parasymphysis fractures
All the surgeries were performed by the same team of the Department of Oral and Maxillofacial Surgery from the School of Dentistry of Ribeirão Preto, University of São Paulo, in Santa Casa Hospital, with general anesthesia. Fractures were diagnosed through clinical assessment and radiographic or magnetic resonance images (Figs. 1, 2). The unilateral CPFs in the G2-CPF were classified according the study of Ellis et al.12 The retromandibular approach was used when the isolated condylar process fractures were present, and only intraoral approaches were used in cases of MAFs associated or not with symphysis or parasymphysis fractures. All MAFs were treated according to the Champy technique, and fracture fixation was performed using 1 non–compressive bone plate system (Neortho; Curitiba, Paraná, Brazil), specifically with the size of 2.0 mm. Additional symphysis or parasymphysis fractures were fixed by two 2-0 mm system non– compressive bone plates (Figs. 3, 4). The surgical technique for the CPF was the same in all cases. The fractures were fixed using 2 bone plates without compression and 2.0-mm screws (Figs. 5, 6). After the surgery, nonsteroidal anti-inflammatory drugs and analgesics were prescribed for 3 days. The patients were discharged from the hospital
FIGURE 3. Postoperative image of the mandibular angle.
FIGURE 5. Surgical image of the CPF.
© 2014 Mutaz B. Habal, MD
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FIGURE 8. Pachymeter Mitutoyo.
FIGURE 6. Postoperative radiographic image of the condylar process.
on the first day after the surgery. Liquid diet was recommended during the first 2 weeks, followed by soft diet for the next third and fourth weeks. General diet was allowed after the fourth week postoperatively.
Bite Force, Electromyographic Data, and Mandibular Mobility In the first place, all patients were submitted to a clinical examination to analyze the postoperative clinical progress. Next, the patients were referred to the EMG laboratory of the Department of Physiology, Stomatology and Basic Pathology, University of São Paulo for EMG examinations, bite-force measurements, and analyses of mandibular mobility. These clinical data were obtained every postoperative week in the first month, and another assessment was performed when the second month postoperative data were achieved. The EMG data and bite-force measurements were collected with the patients sitting on a comfortable chair (office-like), with the arms extended along the body and the hands lying on their thighs. The maximal molar bite force was captured using a digital dynamometer, model IDDK (Kratos; Cotia, Sao Paulo, Brazil), with a 1000-N capacity, adapted to the oral cavity (Fig. 7). The dynamometer has a high-precision charge cell and electronic circuit to indicate the force and supply precise measurements, easily viewed on a digital display. The biosecurity control was applied when the 2 rods with plastic disks on each end of the dynamometer were
FIGURE 7. Dynamometer, model IDDK.
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cleaned with alcohol and disposable latex finger cots covered it (Wariper; Cambuci, Sao Paulo, Brazil). Detailed instructions were given to the patients, and bite tests were performed on the first molar (both sides) and central incisors regions before the recordings were made to ensure the reliability of the procedure. Then, the patients were asked to bite the dynamometer 3 times with maximum molar bite force, with a 2-minute rest interval. The values of maximum bite force were obtained from the averages of these values. Digital pachymeter (Mitutoyo, Santo Amaro, São Paulo, Brazil) was used to measure the mandibular mobility (Fig. 8), considering the maximum standards for mouth opening as well as the right and left lateral movement and protrusion. The Myosystem-Br1 apparatus (DataHomins Ltda, Uberlândia, Minas Gerais, Brazil) was used to evaluate the EMG activity of the masticatory muscles bilaterally. The electrodes were positioned in the ventral region of masseter and the anterior portion of temporal muscles, and a stainless-steel circular electrode was also used as a reference electrode, adhered to the skin over the frontal bone region (Fig. 9). The EMG data were analogically amplified with a gain of 1000 filtered with a pass band of 0.01 to 1.5 kHz and sampled by a 12-bit analog-to-digital converter with a 2-kHz sampling rate. The signals were digitally filtered with a pass-band filter of 10 to 500 Hz during the data processing. Surface differential active electrodes (two 10-mm–long and 2-mm–wide silver chloride bars, separated by a distance of 10 mm with an input impedance of 10 G and a common-mode rejection ratio of 130 dB at 60 Hz) were used in the study. The skin region where electrodes were placed was cleaned with alcohol and shaved when necessary to eliminate pollution or oily residues, which could interfere with the results of the research.
FIGURE 9. Myosystem-BR1.
© 2014 Mutaz B. Habal, MD
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The Journal of Craniofacial Surgery • Volume 25, Number 5, September 2014
difference was found when the mean bite forces of fractured and nonfractured sides were compared in the first and last evaluations, regardless of the group. Regarding the EMG activity, in G1, the values were higher in the former evaluation and declining throughout the study period. This pattern of activity occurred for the masseter and temporal muscles bilaterally in the evaluations, at rest and during posture movements. Conversely, in G2, the values followed a different and, to some extent, irregular pattern. The EMG activity for both temporal muscles reassumed a higher value in the second month in the evaluation at rest, opening and closing, as well as the right and left laterality and protrusion. No statistically significant difference was found when comparing the EMG activity of the fractured and nonfractured sides, regardless of the group (Tables 2, 3). Mandibular motion range was almost fully recovered by G1 (MAF) at the second postoperative month. The mean of the mouth opening represented 92.64% of the value obtained by the control group and right laterality achieved 91.65%. In addition, the left laterality and protrusion fully recovered the normal values. G2 (CPF) achieved 81.1% for mouth opening and 89.66% for the right laterality. The left laterality was fully recovered at the second month; however, protrusion was only 74.36% of the value obtained by the control group (Tables 4, 5).
TABLE 1. Mean Bite Force Measurements (N) of G1 and G2 in the 2-Month Period G1 (MAF) Time 1 wk 2 wk 3 wk 4 wk 2 mo Control Significance
Right Molar 51 111 161 171 261 540
G2 (CPF)
Left Molar
± 1.78 ± 2.17 ± 2.50 ± 2.75 ± 5.20 ± 7.68 *
Right Molar
80 ± 2.30 120 ± 2.17 171 ± 4.53 210 ± 3.75 301 ± 6.14 590 ± 8.45 *
200 220 250 280 290 540
Left Molar
± 4.56 ± 3.60 ± 3.10 ± 6.76 ± 5.88 ± 7.68 *
Effect of Mandibular Fracture Surgery
210 ± 3.20 340 ± 5.65 320 ± 2.36 320 ± 8.17 340 ± 6.73 590 ± 8.45 *
The asterisk symbol denotes significance for P < 0.05.
The muscular activity was evaluated using EMG recordings of the masseter and temporal muscles, bilaterally, at rest (5 s), opening and closing of the mouth (5 s), right and left laterality (5 s), protrusion (5 s) as well as dental clenching with a sheet of paraffin (Parafilm M; Pechinery Plastic Packaging, Batavia, IL) and clenching in maximum voluntary contraction (4 s). Data were normalized by clenching in the maximum voluntary contraction.
RESULTS
DISCUSSION
Data were tabulated and submitted to statistical analysis using independent-samples t-test and repeated-measures test (Statistical Package for the Social Sciences software 19.0, Chicago, IL). A 95% level of significance (P < 0.05) was adopted. In the mean bite force in all measured regions, compared with the regions of the right molars, those on the left side increased during the 2-month period for both groups, with a statistically significant difference (P < 0.05) over a period (Table 1). No statistically significant
The quantitative assessment of the strength of mandibular elevator muscles is a well-recognized clinical parameter16; also, maximum occlusal force is one parameter of masticatory function that is relatively easy to measure.17 In healthy subjects and in patients, significant relationships between occlusal forces and facial morphology have been found; in patients, occlusal forces are related to dental conditions, the kind of prosthetic reconstruction, the presence of temporomandibular and craniomandibular disorders, or
TABLE 2. Mean Normalized EMG Measurements of the Muscles RM, LM, RT, and LT for G1 (MAF) in the 2-Month Period for R and the Clinical Conditions, O/C, RL, LL, and P Period Clinical Conditions
R
O/C
RL
LL
P
Muscle RM LM RT LT RM LM RT LT RM LM RT LT RM LM RT LT RM LM RT LT
1 Wk 0.35 0.56 0.56 0.43 0.47 0.68 0.54 0.51 0.48 0.73 0.66 0.43 0.41 0.62 0.57 0.53 0.46 0.64 0.55 0.47
± 0.11 ± 0.14 ± 0.16 ± 0.09 ± 0.12 ± 0.20 ± 0.15 ± 0.10 ± 0.18 ± 0.14 ± 0.14 ± 0.08 ± 0.14 ± 0.16 ± 0.16 ± 0.08 ± 0.14 ± 0.15 ± 0.14 ± 0.09
2 Wk 0.17 0.31 0.43 0.33 0.31 0.46 0.51 0.39 0.55 0.42 0.77 0.37 0.19 0.40 0.70 0.49 0.27 0.42 0.58 0.34
± 0.05 ± 0.07 ± 0.14 ± 0.11 ± 0.09 ± 0.10 ± 0.16 ± 0.15 ± 0.36 ± 0.13 ± 0.24 ± 0.14 ± 0.05 ± 0.10 ± 0.21 ± 0.13 ± 0.05 ± 0.10 ± 0.20 ± 0.13
3 Wk 0.16 0.19 0.44 0.32 0.25 0.27 0.42 0.37 0.21 0.30 0.48 0.35 0.15 0.20 0.41 0.35 0.24 0.26 0.40 0.29
± 0.08 ± 0.06 ± 0.17 ± 0.08 ± 0.08 ± 0.10 ± 0.14 ± 0.09 ± 0.08 ± 0.12 ± 0.17 ± 0.10 ± 0.06 ± 0.05 ± 0.14 ± 0.07 ± 0.09 ± 0.08 ± 0.13 ± 0.06
4 Wk
2 Mo
0.17 ± 0.08 0.20 ± 0.06 0.35 ± 0.09 0.21 ± 0.05 0.25 ± 0.06 0.31 ± 0.06 0.48 ± 0.10 0.33 ± 0.09 0.26 ± 0.09 0.30 ± 0.09 0.49 ± 0.14 0.26 ± 0.10 0.16 ± 0.05 0.22 ± 0.06 0.38 ± 0.10 0.29 ± 0.09 0.35 ± 0.12 0.48 ± 0.19 0.39 ± 0.12 0.23 ± 0.07
0.10 ± 0.04 0.08 ± 0.01 0.22 ± 0.76 0.13 ± 0.03 0.25 ± 0.11 0.15 ± 0.04 0.35 ± 0.13 0.21 ± 0.08 0.14 ± 0.06 0.19 ± 0.08 0.27 ± 0.09 0.16 ± 0.06 0.08 ± 0.01 0.10 ± 0.02 0.19 ± 0.06 0.18 ± 0.04 0.13 ± 0.01 0.16 ± 0.06 0.19 ± 0.07 0.12 ± 0.03
Control 0.07 ± 0.09 ± 0.09 ± 0.13 ± 0.15 ± 0.17 ± 0.17 ± 0.19 ± 0.11 ± 0.13 ± 0.19 ± 0.13 ± 0.12 ± 0.10 ± 0.19 ± 0.19 ± 0.11 ± 0.16 ± 0.11 ± 0.11 ±
0.01 0.01 0.01 0.01 0.29 0.03 0.03 0.02 0.02 0.03 0.08 0.01 0.02 0.01 0.04 0.04 0.01 0.04 0.02 0.01
Significance * * NS * NS * NS * NS * NS NS * * * * * * * *
The asterisk symbol denotes significance for P < 0.05; NS, not significant for P < 0.05. LL, left laterality; LM, left masseter; LT, left temporal; NS, not significant for P < 0.05; O/C, opening/closing; P, protrusion; R, rest mandibular; RL, right laterality; RM, right masseter; RT, right temporal.
© 2014 Mutaz B. Habal, MD
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TABLE 3. Mean Normalized EMG Measurements of the Muscles RM, LM, RT, and LT for G2 (CPF) in the 2-Month Period for R and the Clinical Conditions, O/C, RL, LL, and P Period Clinical Conditions
R
O/C
RL
LL
P
Muscle RM LM RT LT RM LM RT LT RM LM RT LT RM LM RT LT RM LM RT LT
1 Wk 0.26 0.31 0.26 0.14 0.34 0.48 0.51 0.18 0.23 0.36 0.24 0.12 0.33 0.41 0.29 0.14 0.25 0.40 0.26 0.12
2 Wk
± 0.10 ± 0.12 ± 0.09 ± 0.02 ± 0.12 ± 0.23 ± 0.25 ± 0.03 ± 0.10 ± 0.17 ± 0.06 ± 0.02 ± 0.19 ± 0.17 ± 0.08 ± 0.02 ± 0.10 ± 0.17 ± 0.08 ± 0.02
0.16 0.17 0.34 0.11 0.32 0.43 0.39 0.18 0.17 0.23 0.35 0.11 0.21 0.20 0.34 0.16 0.28 0.43 0.33 0.12
3 Wk
± 0.06 ± 0.05 ± 0.16 ± 0.02 ± 0.10 ± 0.17 ± 0.16 ± 0.07 ± 0.07 ± 0.09 ± 0.13 ± 0.03 ± 0.08 ± 0.07 ± 0.16 ± 0.04 ± 0.11 ± 0.17 ± 0.16 ± 0.03
0.11 0.14 0.13 0.14 0.21 0.27 0.17 0.24 0.42 0.23 0.18 0.13 0.15 0.15 0.14 0.19 0.24 0.24 0.15 0.10
± 0.03 ± 0.02 ± 0.02 ± 0.03 ± 0.04 ± 0.06 ± 0.02 ± 0.09 ± 0.19 ± 0.04 ± 0.05 ± 0.03 ± 0.02 ± 0.01 ± 0.01 ± 0.04 ± 0.08 ± 0.05 ± 0.01 ± 0.02
4 Wk
2 Mo
0.10 ± 0.03 0.13 ± 0.05 0.15 ± 0.05 0.11 ± 0.03 0.29 ± 0.09 0.43 ± 0.19 0.17 ± 0.04 0.18 ± 0.06 0.17 ± 0.08 0.18 ± 0.05 0.17 ± 0.05 0.09 ± 0.02 0.14 ± 0.02 0.16 ± 0.04 0.15 ± 0.04 0.16 ± 0.04 0.20 ± 0.03 0.31 ± 0.10 0.13 ± 0.03 0.12 ± 0.02
0.12 ± 0.04 0.11 ± 0.04 0.30 ± 0.19 0.18 ± 0.06 0.22 ± 0.04 0.29 ± 0.10 0.41 ± 0.16 0.25 ± 0.06 0.15 ± 0.05 0.27 ± 0.11 0.53 ± 0.36 0.17 ± 0.06 0.17 ± 0.05 0.19 ± 0.05 0.27 ± 0.15 0.23 ± 0.06 0.29 ± 0.05 0.38 ± 0.18 0.29 ± 0.15 0.20 ± 0.11
Control 0.07 ± 0.09 ± 0.09 ± 0.13 ± 0.15 ± 0.17 ± 0.17 ± 0.19 ± 0.11 ± 0.13 ± 0.19 ± 0.13 ± 0.12 ± 0.10 ± 0.19 ± 0.19 ± 0.11 ± 0.16 ± 0.11 ± 0.11 ±
0.06 0.01 0.01 0.01 0.29 0.03 0.03 0.02 0.02 0.03 0.08 0.01 0.02 0.01 0.04 0.04 0.01 0.04 0.02 0.01
Significance * * NS * NS * NS NS * * * * NS NS NS NS * * NS NS
The asterisk symbol denotes significance for P < 0.05; NS, not significant for P < 0.05.
fractures of the bones involved in the masticatory apparatus. In addition, significant relationships between occlusal force and masticatory performance have been demonstrated.16 Bite force evaluation revealed a gradual increase from postoperative measurements to the second month postoperatively in G1 (MAF) in agreement with the study of Tate et al.10 These studies found that, at 6 weeks postoperatively, values close to 50% to 60% of molar force were obtained within a control group. Similarly, the G1 (MAF) at 2 months postoperatively achieved values close to 50% of bite force compared with the control group. In addition, the control group examined by Gerlach and Schwarz18 could only generate approximately 176 N, 245 N, and 205 N at the central incisors, left molar, and right molar, respectively. In the current study, the values of mandibular motion range for the G1 (MAF) were within the reference levels during the first week postoperatively; conversely, G2 (CPF) achieved values close to 80% of that presented by the control group only at the second month postoperatively. Throckmorton and Ellis19 found that, at 6 weeks after unilateral CPFs treated by open or closed technique, all patients’ excursive movements were significantly smaller than those of controls. Palmieri et al20 investigated unilateral CPFs treated either by open and closed techniques. They found that, at 6 weeks postoperatively, the patients treated by closed methods
had an average of 4.4-mm greater interincisal dimension than did the patients treated by open methods. However, this same investigation showed little difference in mandibular motion between the groups from 6 weeks to 3 years after the injury. We agree with the authors that some hipomobility may be caused by joint and incisional pain or possibly because scarring occurred during healing of the surgical site. Electromyography as a method of analyzing muscle function has evolved over the last 50 years. Most extensively used in EMG are the surface electrodes. Surface electrodes are readily available and easily applied and free of discomfort.21 By means of surface EMG, Ribeiro et al22 evaluated the isolated fractures of the zygomatico-orbital complex. These authors observed an increase in EMG activity for the right masseter as well as the left and right temporal muscles and a decrease in EMG activity for the left masseter muscle when compared with the control group. The authors concluded that the EMG activity values decreased until the sixth month after surgery, after which the normal pattern was reestablished. During maximum voluntary teeth clenching, the temporalis muscles are given the function of stabilization action, whereas the masseter muscles perform the main clench activity.22 Moreover, an imbalance of the left-right standardized activity may result in
TABLE 4. Mean Mandibular Motion Range Measurements of G1 (MAF) in the 2-Month Period 1 Wk Mouth opening Right laterality Left laterality Protrusion
25.60 5.15 6.08 2.93
± 2.37 ± 0.69 ± 0.78 ± 0.30
2 Wk 29.25 6.43 7.47 3.74
± 2.60 ± 1.30 ± 0.68 ± 0.37
3 Wk 35.12 7.92 8.40 4.31
± 3.71 ± 1.50 ± 0.76 ± 0.51
4 Wk 38.64 8.49 8.59 5.79
± 3.95 ± 1.29 ± 0.73 ± 0.78
2 Mo 45.25 8.15 8.48 6.70
± 3.08 ± 1.32 ± 0.67 ± 0.57
Control
Significance
48.8 ± 1.47 8.9 ± 0.54 8.32 ± 0.61 4.71 ± 0.41
* * * *
All values are expressed as millimeters. The asterisk symbol denotes significance for P < 0.05.
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© 2014 Mutaz B. Habal, MD
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
The Journal of Craniofacial Surgery • Volume 25, Number 5, September 2014
Effect of Mandibular Fracture Surgery
TABLE 5. Mean Mandibular Motion Range Measurements of G2 (CPF) in the 2-Month Period 1 Wk Mouth opening Right laterality Left laterality Protrusion
22.43 5.35 5.43 2.15
± 1.43 ± 0.83 ± 1.46 ± 0.98
2 Wk
3 Wk
4 Wk
24.37 ± 2.02 5.30 ± 0.76 7.50 ± 1.54 1.94 ± 0.92
25.75 ± 0.84 5.22 ± 1.12 9.02 ± 1.25 1.31 ± 0.62
28.99 ± 1.56 7.40 ± 1.28 7.18 ± 1.51 3.43 ± 1.21
2 Mo 39.62 7.98 9.00 3.50
± 2.37 ± 0.93 ± 1.03 ± 0.76
Control
Significance
48.85 ± 1.47 8.9 ± 0.54 8.32 ± 0.61 4.71 ± 0.41
* * * *
All values are expressed as millimeters. The asterisk symbol denotes significance for P < 0.05.
abnormal loads over the temporomandibular joints. Neuromuscular adaptations occur within the masticatory system after bilateral fractures of the mandibular condylar processes.5 According to these authors, individuals with bilateral CPFs selectively increase the EMG output in the posterior temporalis fibers. The effect of this increased activity is to provide a posteriorly directed vector onto the coronoid process, which, all other things being equal, can rotate the anterior portion of the mandible superiorly, bringing the incisors into contact. In addition, the authors affirm that these neuromuscular adaptations are called into play to position the mandible early after injury.23 Thus, the only mechanism whereby the mandible can be positioned into a normal occlusal relationship early after injury is by complex neuromuscular adaptations in the muscles of mastication. The temporalis muscle has the predominant role in the balancing of the mandibular movements. The muscle determines the muscular tone in the postural jaw position, and it has to do more with speed function than with force.15 The temporal muscle contracts at closure of the mouth, being considered a positioner of the mandibular condyle24 by adjusting the direction of the movements with better synchronization. Ahlgren et al,25 using needle EMG, reported that the middle and posterior portions of the temporal muscle in postural resting condition showed EMG activity, whereas the anterior portion was found to be inactive, allowing mandibular stability in healthy subjects. In traumatic situations such as condylar fracture and jaw surgery, the individual stress may appear and lead to functional changes of the masticatory muscles, promoting muscle hyperactivity,26 which was observed in this work with our results, where the G1 values were higher in the first evaluation and declining throughout the study period. In this study, we found a decreased EMG activity in the temporal muscles bilaterally at the second month postoperatively in both temporal muscles. Besides, we believe that, despite the vertical height reestablishment after open surgery, these neuromuscular adaptations still occur in CPF by traumatic or operative trauma to the masseter muscles and to protective neuromuscular mechanisms of masticatory system (splinting components are activated or deactivated to take forces of the damaged bone). Interestingly, we observed that, while comparing the fractured side versus the nonfractured side separately, there were no statistically significant differences in the molar bite force mean and on the EMG activity. This behavior makes the authors expect bilateral masticatory muscles’ protective neuromuscular mechanisms, not considering the side of the fracture. Both current groups of subjects achieved good functional recovery in mandibular motion range. Every bite force measurement was approximately 50% to 55% of the control group except for the incisor bite force in G2 (CPF). In addition, EMG activity indices measured in the G1 (MAF) subjects declined almost in a linear pattern until the second month; however, G2 (CPF) assumed a more irregular pattern, especially for the temporal muscles. In EMG averages and maximum bite force analysis of the patients in groups G1 (MAF) and G2 (CPF) as well as the comparison of the right and
left sides (all periods), higher values for the nonfractured sides were found, but this difference was not statistically significant and the results were in agreement with those in the study of Richardson et al,27 where no statically significant difference was found when comparing the bite force and EMG activity of fractured and nonfractured sides, regardless of the group. This is probably caused by the fact the technique of fixation of condylar fractures of the mandibular angle has the ability to restore balance and function of the stomatognathic system.28 The authors agree that this study should be repeated with a large sample and with a larger longitudinal assessment during subsequent healing phases. On the basis of this study, the authors concluded that a good functional recovery was achieved by the individuals who had a mandible angle fracture or condylar process fracture, after 2 postoperative months. ACKNOWLEDGMENTS The authors thank the State of São Paulo Foundation (FAPESP) for technical, scientific, and financial support, which were essential for this study (process no. 2007.1.1371.58.2).
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