Functional Evaluation of the Behavior of Masticatory Muscles in Zygomaticomaxillary Complex Fracture: A Prospective Study.

AIMS: The purpose of this study is to functionally evaluate the behavior of the masticatory muscles (masseter and temporalis) following zygomaticomaxillary complex (ZMC) fractures by assessing bite force, electromyography (EMG), and mandibular movements. MATERIALS AND METHODS: Group I consisted of 20 patients with unilateral ZMC fractures who were treated surgically with one-, two-, or three-point fixations at the frontozygomatic, infraorbital, or zygomaticomaxillary buttress region as per clinical and radiological assessments. Group II control group included 20 normal patients. The muscle activity was functionally evaluated before and after the surgery for a period of 6 months. The evaluation consisted of bite force measurement, EMG analysis of masseter and temporalis muscles, and measurements of mandibular movements. RESULTS: There was an increase in bite force and EMG activity throughout the evaluated postoperative period, but at the end of 6 months, the values were still below the control levels for majority of the patients. Maximum mouth opening increased considerably after the surgery. CONCLUSION: According to bite force and EMG, the masticatory musculature returned to near normal levels by the 3rd month after the surgery. CLINICAL SIGNIFICANCE: Management of fractures of the zygoma by open reduction and fixation raises the question of the location of fixation points owing to the action of masseter and temporalis on the ZMC. This study supports the current clinical concept of minimized fixation in treating ZMC fractures.

Electromyographic study in patients with surgically treated facial fractures.

This study, using surface electromyography, analyzed the activity of the masseter muscles of 30 patients with facial bone fractures that were surgically treated. Evaluations were made before surgery and in the 7th, 30th, and 60th days after surgery. The value of each measure and the average of 3 maximum voluntary isometric contractions lasting 5 seconds each were registered, and statistical analyses were performed. Patients had a mean age of 31 years and an average of 1.33 fractures. They were grouped according to the type of fracture as follows: mandibular (50%), zygomatic complex (33%), maxilla (10%), and associated fractures (6.7%). There was a lower masseter activity in the preoperative period, when compared with normal values in all groups of fractures. There was a sharp drop in the masseter activity in the postoperative period of 7 days, and all groups showed recovery of activity in 60 days but still below the normal value referenced in the literature. The mean values of the masseter activity, in descending order, were from the zygomatic complex, mandibular, maxillary, and associated fractures. The unilateral mandibular fractures showed higher values than the bilateral fractures in most of the evaluations. There was a highly significant difference in the comparison of the evolution of the masseter activity on both sides, for mandibular and zygomatic complex fractures, and the pairwise comparison showed significant difference between most groups. It was concluded that facial fractures and surgical procedures had negative effects in the muscle activity as observed using electromyography.

The tolerance of the maxilla to blunt impact.

This study reports the results of 38 infraorbital maxilla impacts performed on male cadavers. Impacts were performed using an unpadded, cylindrical impactor (3.2 kg) at velocities between 1 and 5 m/s. The peak force and acoustic emission data were used to develop a statistical relationship of fracture risk as a function of impact force. Acoustic emission sensors were used to provide a noncensored measure of the maxilla tolerance and were essential due to the increase in impactor force after fracture onset. Parametric and nonparametric techniques were used to estimate the risk of fracture tolerance. The nonparametric technique produced an estimated 50% risk of fracture between 970 and 1223 N. The results obtained from the parametric and nonparametric techniques were in good agreement. Peak force values achieved in this study were similar to those of previous work and were unaffected by impactor velocity. The results of this study suggest that an impact to the infraorbital maxilla is a load-limited event due to compromise of structural integrity.

Outcomes in pediatric facial fractures: early follow-up in 177 children and classification scheme.

A comprehensive study of adverse outcomes after pediatric facial fractures has not been published. This study aimed to determine the incidence and classify adverse outcomes after facial fractures in children while reporting our early results. A retrospective chart review was performed on facial fracture patients identified in the Craniofacial Trauma Database of the Children's Hospital of Pittsburgh and seen in follow-up from 2003 to 2007. An Adverse Outcome Classification Scheme was developed: type 1, outcomes resulting from the fracture; type 2, outcomes resulting from fracture treatment; and type 3, outcomes resulting from the interaction between the fracture, its treatment, and subsequent growth and development. Fisher exact or χ analyses were completed. A total of 177 pediatric facial fracture patients were identified with 13.3 months of average follow-up. Mean age was 9.8 years (range, 0.4-18.7 y). Of these patients, 41.8% underwent surgery and 57 patients (32.2%) had adverse outcomes (type 1, 14.1%; type 2, 11.3%; and type 3, 15.8%); 26.3% of these had multiple adverse outcomes. Isolated fractures resulted in fewer adverse outcomes and fewer multiple adverse outcomes compared with combined fractures (26.6% versus 45.3%, P = 0.015; 4% versus 18.9%, P = 0.002). Patients treated operatively exhibited more types 1, 2, and 3 and multiple adverse outcomes compared to those treated conservatively (P < 0.01). In our pediatric cohort, 32.2% of patients had an adverse outcome. With longer follow-up and growth and development studies, we will likely see an increase in the incidence of type 3 adverse outcomes. We recommend, whenever possible, conservative treatment of pediatric facial fractures.

Optimal palatal configuration for miniscrew applications.

OBJECTIVE: To test the hypothesis that palatal bone is not able to support titanium miniscrews (11 mm in length and 2 mm in diameter) when subjected to forces normally generated during orthodontic treatment. MATERIALS AND METHODS: The miniscrew-palatal bone system was modeled and analyzed using the commercial finite element method software ANSYS Multiphysics 10.0; tests were done in both a state of total osseointegration and in the absence of it. Calculations were carried out in both cases in configurations where the miniscrew was inserted into two different palatal regions: in the first it was anchored in one layer of cortical bone and in the underlying trabecular bone; in the second, two layers of cortical bone and the trabecular bone in between were involved. Two different loads were taken into account, 240 gf and 480 gf, both of which are within the normal range for orthodontic treatment, and applied to the miniscrew heads. RESULTS: The results demonstrated that the miniscrew inserted into the palate can be anchored to bone and loaded within normal orthodontic force range without exceeding the stress levels that lead to bone fracture. The osseointegrated system was characterized by a lower level of stress than the nonosseointegrated one, but anchorage within the second layer of cortical bone markedly reduced the stress on the trabecular bone, thereby improving the stability of the implant, also in the absence of osseointegration. CONCLUSIONS: The hypothesis is rejected. Miniscrews loaded within the normal orthodontic force range do not exceed the stress levels that lead to bone fracture.

Investigation of infraorbital nerve injury following zygomaticomaxillary complex fractures.

The aim of this study was to investigate the severity of infraorbital nerve injury following zygomaticomaxillary complex fractures and to estimate the treatment methods facilitating its functional recovery. A total of 478 patients with unilateral zygomaticomaxillary complex fractures were treated. Infraorbital nerve sensory disturbances were diagnosed in 64.4% of the patients. Injury of the infraorbital nerve was expressed as asymmetry index, which was calculated as a ratio between the affected side and the intact side electric pain detection thresholds at the innervation zone skin before treatment and 14 days, 1, 3, 6 and 12 months postoperatively. A mean asymmetry index of 0.6 +/- 0.03 and 1.9 +/- 0.5 was registered for 57 (11.9%) patients with hyperalgesia and for 251 (52.5%) patients with hypoalgesia, respectively. As a result of retrospective analysis of infraorbital nerve sensory disturbances and its functional recovery, infraorbital nerve injury severity was classified as mild, moderate and severe. It was found that the dynamics and outcome of the functional infraorbital nerve recovery depend on the severity of the injury and the presence of infraorbital canal damage. Function was completely recovered within 3 months after treatment in cases with mild nerve injury. In moderate cases, complete recovery was seen within 6 months and in 34.6% of the severe cases, within a 12-month period after treatment when infraorbital nerve decompression was performed according to the stated indication. Treatment based on infraorbital nerve injury classification offers a better prognosis for complete recovery of the infraorbital nerve function.

Anatomical Thin Titanium Mesh Plate Structural Optimization for Zygomatic-Maxillary Complex Fracture under Fatigue Testing.

This study performs a structural optimization of anatomical thin titanium mesh (ATTM) plate and optimal designed ATTM plate fabricated using additive manufacturing (AM) to verify its stabilization under fatigue testing. Finite element (FE) analysis was used to simulate the structural bending resistance of a regular ATTM plate. The Taguchi method was employed to identify the significance of each design factor in controlling the deflection and determine an optimal combination of designed factors. The optimal designed ATTM plate with patient-matched facial contour was fabricated using AM and applied to a ZMC comminuted fracture to evaluate the resting maxillary micromotion/strain under fatigue testing. The Taguchi analysis found that the ATTM plate required a designed internal hole distance to be 0.9 mm, internal hole diameter to be 1 mm, plate thickness to be 0.8 mm, and plate height to be 10 mm. The designed plate thickness factor primarily dominated the bending resistance up to 78% importance. The averaged micromotion (displacement) and strain of the maxillary bone showed that ZMC fracture fixation using the miniplate was significantly higher than those using the AM optimal designed ATTM plate. This study concluded that the optimal designed ATTM plate with enough strength to resist the bending effect can be obtained by combining FE and Taguchi analyses. The optimal designed ATTM plate with patient-matched facial contour fabricated using AM provides superior stabilization for ZMC comminuted fractured bone segments.

An ultrastructural study on indirect trauma of dental pulp caused by maxillofacial impact injury in dogs.

BACKGROUND: Indirect injuries of adjacent tissues and organs usually accompany maxillofacial impact injuries. However, studies on indirect dental pulp injury are rare. This study was designed to determine the characteristics of indirect dental pulp injury caused by impact injury of mandible in dogs. METHODS: Eighteen dogs were divided equally into six groups with random allocation. Right mandible of each dog was impacted but teeth were not injured directly. Then, the animals were killed at appointed time points and ultrastructural changes in dental pulp of assigned teeth of each dog were investigated with transmission electron microscope. RESULTS: Dental pulp of the fourth premolar of right mandible was injured very severely, but irreversible necrosis did not occur in the end. Dental pulp of the second premolar of right mandible was injured less severely and reversibly. Dental pulp of the second premolar of left mandible was injured mildly and temporarily. CONCLUSION: In the indirect injury of dental pulp caused by maxillofacial impact injury, the injured area is relatively extensive. The effect of the trauma decreases progressively and sharply as the distance to the impact site increases. Ultrastructural changes in the damaged nerves take place early.

Electromyography assessment in zygomaticomaxillary complex fractures.

OBJECTIVE: The aim of this study was to assess the activity of the masseter and temporalis muscles using surface electromyography (EMG) in patients with zygomaticomaxillary complex (ZMC) fractures. PATIENTS AND METHODS: This prospective study was carried out on 25 patients who had ZMC fractures. Fifteen patients were managed by open reduction and rigid fixation (ORIF) using titanium miniplates. This study, using surface electromyography, analyzed the activity of the masseter and temporalis muscles of 25 patients with ZMC fractures; 15 of them were surgically treated under general anesthesia (GA). Evaluations were made before surgery and 6 weeks after surgery by recording the mean of muscle contraction of 20 motor unit action potential (MUAP) against resistance, and statistical analyses were performed. RESULTS: A significant EMG difference between the normal and ZMC fracture sides was found (P < 0.0001) for both masseter and temporalis muscles and was significantly improved after ORIF. However, postoperative EMV values of the repaired side was significantly less than measured postoperatively in the normal side (P < 0.0001) for both muscles. CONCLUSION: ZMC fractures significantly diminish muscular activity of the masseter and temporalis and even though significant recovery of muscle activity was revealed after 6 weeks, it is still less than normal activity, highlighting the importance of postoperative rehabilitation.

Facial injury: a review of biomechanical studies and test procedures for facial injury assessment.

A review of biomechanical studies that have attempted to measure fracture tolerances of facial bones has been carried out. The particular bones of interest were the mandible, the zygoma, the maxilla and the nasal bones. Numerical values have been given for the peak force and pressure fracture tolerances for these bones. A study of these values illustrates just how variable the bone strength of various individuals is. A review of various methods that have attempted to measure and quantify the physical effects of a blow to the face has also been carried out. Three major types of test procedure exist, namely frangible elements, peak force and pressure sensing elements and deformable elements. Frangible and deformable elements generally replace the face of a standard test dummy, fracturing and deforming at appropriate impact force levels, respectively. These surrogate face forms are used for two different reasons; either they are used to measure the damage to the human face for some impact scenario or they are simply used to better simulate the response of the whole head to impact by simulating the compliance of the face. Peak force and pressure sensing elements take the form of piezoelectric sensors and pressure-sensitive, colour 'Fuji film'. Both these methods are complicated and really only suitable for research purposes only. Finally, it is recommended that a mathematical model approach be used to establish the principal injury mechanism and support further development of an acceptable face form test.

Human maxilla bone response to 30 degrees oriented impacts and comparison with frontal bone impacts.

The aims of this study were to compare the responses of human maxilla and frontal bones under 30 degrees-oriented impacts. Maxilla and frontal bones of the same subject were impacted by a guided horizontal steel cylinder. Linear acceleration time histories and force time histories were plotted and corridors were proposed for maxilla bone response. Sensitivity of head dynamics in regard to impact energy level and localization showed the protection of the intracranial contents by the facial bones crushing. Injury risk curves were established for impact on frontal bone, showing a 50% risk injury for impact energy of 265 J or impact force of 7500 N.

Biomechanical mechanisms of orbital wall fractures - a transient finite element analysis.

As the biomechanical mechanisms of orbital wall fractures are still under research, three different fracture mechanisms were tested in a finite element based investigation. In contrast to earlier studies, a finer skeletal model and a transient dynamic simulation were used to test pure hydraulic, pure buckling and a mixed force transmission. Results showed that each set-up led to different orbital fracture patterns, which correlate well with clinical findings. Therefore the conclusion is that different mechanisms may act together explaining the variety of clinical fracture situations. Biomechanical testing has proven to be appropriate in answering questions regarding fracture mechanisms.

Biomechanical evaluation of Le Fort I maxillary fracture plating techniques.

PURPOSE: This study used a biomechanical model to examine fundamental questions about rigid plate fixation treatment for maxillary Le Fort I fractures. Specifically, we sought to elucidate the principal strain patterns generated in miniplates and bite force transducers secondary to all masticatory forces, as well as the amount of permanent deformations incurred due to these loading forces. MATERIALS AND METHODS: Forty polyurethane synthetic maxillary and mandibular replicas were used to simulate the mandible and maxilla. Ten replicas were controls (group A). The other 30 were divided into 3 groups (10 each), according to the fixation techniques of 3, 2, and 1 miniplates each side (groups B-D), that were osteotomized in the Le Fort I fracture line on the maxilla. Different forces of masseter medial pterygoid, temporalis, and lateral pterygoid muscles were loaded onto the replicas to simulate different functional conditions (anterior incisor, premolar, and molar clenching). Rosette strain gauges were attached at predefined points on the plates and the bite force transducer to compare the stability and bite force of the different fixation methods for maxillary Le Fort I fractures. RESULTS: Statistically significant differences were found for the deformation of the plates among fixation techniques. The order of stability for each technique was: group B greater than group C greater than group D. In regard to bite force, no difference was found between those found with group A and group B (P > .05), whereas the bite forces of groups C and D were less than those of group A (P < .05). CONCLUSIONS: The fixation of 3 miniplates on each side provides sufficient stability and restores the bite force to the level of the intact maxilla. "The ideal fixation" with 2 miniplates on each side restores 90% of the bite force, and there were more deformations of the miniplates with the "ideal fixation" compared to those found with group B. Group D fixation produced the worst effects for the treatment of maxillary Le Fort I fractures with a weak bite force and insufficient stability.

Mucociliary clearance and sense of smell following management of Le Fort maxilla fractures.

OBJECTIVE: To assess mucociliary transport and olfaction in patients after Le Fort fractures. STUDY DESIGN: Forty-one patients were enrolled who had sustained a Le Fort fracture during the preceding five years. Control group consisted of students. Olfaction and mucociliary transport were examined in all subjects. A capillary with saccharine was placed on the inferior nasal concha, and time was recorded in which the subject tasted sweetness in the mouth. Results were subject to statistical analysis. Patients with allergy, sinus disease and smokers were excluded from the examination. RESULTS: Disturbance of mucociliary transport and olfaction turned out to be statistically dependent on the type of fracture and management. CONCLUSIONS: Le Fort fracture might be complicated by compromised mucociliary clearance and olfactory disturbances.

[Growth disorders following fractures of the midface in children]. / Wachstumsstörungen nach Frakturen des Mittelgesichtes im Kindesalter.

12 patients who had suffered mid face fractures during their childhood were examined for skeletal deformities of the facial skull. The cephalometric data showed that neither the position nor the inclination of the maxilla were significantly different from normal anatomy. No correlation was found between the age, the severity of injuries and surgical treatment and resulting deformities.

[Changes in the condyle path following fractures with dislocation of the maxilla]. / Veränderungen der Kondylenbahnen nach Frakturen mit Dislokation des Oberkiefers.

In spite of rigid internal fixation with miniplates after midfacial fractures, dislocation of the previously mobilized fragment in the dorsal direction is conceivable. Thus, the mandible would be forced into a dorsal position over the occlusion. As a result, changes of the condyle paths, such as limitations or deviations from the normal, would be possible. Six patients, who had sustained midfacial fractures with mobilization or dislocation of the maxilla, were followed up. The condyle paths were recorded at the earliest time possible after rigid internal fixation and after removal of the miniplates. We used the electronic computer-assisted registration system (ECRS), which allows three-dimensional registration without occlusal interferences. The patterns of the TMJ movements were not impaired, arguing against the dorsal transposition of the maxilla. The extent of the movements during the first postoperative weeks, however, was significantly reduced in some cases, even if intermaxillary fixation was not carried out. In our opinion, this is due to the periarticular infiltration and a varying elasticity of the articular capsule in different directions.