The Sphenozygomatic Suture as a Key Site for Osteosynthesis of the Orbitozygomatic Complex in Panfacial Fractures: A Biomechanical Study in Human Cadavers Based on Clinical Practice:

Efficacy of Altered Two-Point Fixation in Zygomaticomaxillary Complex Fracture

PURPOSE

To reconstruct a zygomaticomaxillary complex (ZMC) fracture, zygomaticofrontal (ZF) suture is the most reliable site to assess anatomical alignment and to secure rigidity. It has been chosen primary site to be fixed, but approach through the lateral eyebrow incision may leave a visible scar. This study suggests altered two-point fixation of ZMC fracture without accessing the ZF suture.

METHODS

In the retrospective study, a total of 40 patients with ZMC fracture were divided into two groups (group 1, two-point fixation and group 2, three-point fixation). Patient demographics and follow-up were evaluated, and degree of reduction including cortical gaps of ZF and inferior orbital (IO) area, protruding difference of zygoma, and malar difference using asymmetry index were measured through preoperative and postoperative CT.

RESULTS

Preoperatively, the means of ZF displacement, IO displacement, protruding difference of zygoma, and facial asymmetry index between the groups were not statistically different. The result was the same after the operation. However, all variables were significantly different before and after surgery within each group. Moreover, mean operation time was significantly different between groups (P value = 0.026).

CONCLUSION

Altered two-point fixation in ZMC fracture excluding incision approaching the ZF provides surgical efficacy and similar surgical outcomes to three-point fixation but offers reduced operation time and fewer complications.

Review of In Vivo Bone Strain Studies and Finite Element Models of the Zygomatic Complex in Humans and Nonhuman Primates: Implications for Clinical Research and Practice

The craniofacial skeleton is often described in the clinical literature as being comprised of vertical bony pillars, which transmit forces from the toothrow to the neurocranium as axial compressive stresses, reinforced transversely by buttresses. Here, we review the literature on bony microarchitecture, in vivo bone strain, and finite-element modeling of the facial skeleton of humans and nonhuman primates to address questions regarding the structural and functional existence of facial pillars and buttresses. Available bone material properties data do not support the existence of pillars and buttresses in humans or Sapajus apella. Deformation regimes in the zygomatic complex emphasize bending and shear, therefore conceptualizing the zygomatic complex of humans or nonhuman primates as a pillar obscures its patterns of stress, strain, and deformation. Human fossil relatives and chimpanzees exhibit strain regimes corroborating the existence of a canine-frontal pillar, but the notion of a zygomatic pillar has no support. The emerging consensus on patterns of strain and deformation in finite element models (FEMs) of the human facial skeleton corroborates hypotheses in the clinical literature regarding zygomatic complex function, and provide new insights into patterns of failure of titanium and resorbable plates in experimental studies. It is suggested that the "pillar and buttress" model of human craniofacial skeleton function be replaced with FEMs that more accurately and precisely represent in vivo function, and which can serve as the basis for future research into implants used in restoration of occlusal function and fracture repair. Anat Rec, 299:1753-1778, 2016. © 2016 Wiley Periodicals, Inc.

Efficacy and Safety of Biodegradable Osteofixation Devices in Oral and Maxillofacial Surgery: a Systematic Review

The use of osteofixation devices should be evidence-based if uncomplicated bone healing is to be achieved. Numerous studies describe and claim the advantages of biodegradable over titanium devices as a bone fixation method. Here, we systematically review the available literature to determine the clinical efficacy and safety of biodegradable devices compared with titanium devices in oral and maxillofacial surgery. In addition, related general aspects of bone surgery are discussed. We conducted a highly sensitive search in the databases of MEDLINE (1966–2005), EMBASE (1989–2005), and CENTRAL (1800–2005) to identify eligible studies. Eligible studies were independently evaluated by two assessors using a quality assessment scale. The study selection procedure revealed four methodologically ‘acceptable’ articles. Owing to the different outcome measures used in the studies, it was impossible to perform a meta-analysis. Therefore, the major effects regarding the stability and morbidity of fracture fixation using titanium and biodegradable fixation systems were qualitatively described. Any firm conclusions regarding the fixation of traumatically fractured bone segments cannot be drawn, due to the lack of controlled clinical trials. Regarding the fixation of bone segments in orthognathic surgery, only a few controlled clinical studies are available. There does not appear to be a significant short-term difference between titanium and biodegradable fixation systems regarding stability and morbidity. However, definite conclusions, especially with respect to the long-term performance of biodegradable fixation devices used in maxillofacial surgery, cannot be drawn. Abbreviations: CENTRAL, Cochrane Central Register of Controlled Trials; MeSH, Medical Subject Heading; VAS, Visual Analogue Scale; and W, weight.

Radiological evaluation of sphenozygomatic suture fixation for restoration of orbital volume: A retrospective study

PURPOSE

Lateral displacement of fracture zygomaticomaxillary complex (ZMC) can cause significant increase in orbital volume leading to enophthalmos. The aim of this study was to radiologically evaluate the efficacy of sphenozygomatic (SZ) suture fixation for restoration of orbital volume after elevation of the temporalis in cases of fracture ZMC where the fixation of zygomatic arch (ZA) was deemed necessary through latero-posterior approach.

MATERIALS & METHODS

43 operated cases of fracture ZMC using 4-point fixation were divided into two groups. Group I (n = 24) cases had undergone reduction and fixation of SZ suture as fourth point of fixation by elevating temporalis muscle using hemicoronal approach. Group II (n = 19) cases had undergone reduction and fixation of Infraorbital (IO) rim as fourth point of fixation using preseptal transconjunctival approach. Both the groups were analyzed separately and compared for restoring the increased orbital volume on CT.

RESULTS

Difference in the pre-surgical orbital volume of both the groups was found to be statistically insignificant [p = .678]. In group I, the average bony orbital volume significantly reduced by 3.6 cc from 25.5 cc to 21.9 cc [p = .000] post-surgically. In group II, the average bony orbital volume reduced by 1.5 cc from 25.6 cc to 24.1 cc post-surgically There was a significant difference in the reduction of the increased orbital volume among the 2 groups (Group I: 3.6 cc, group II: 1.5 cc). The amount of reduction was more and statistically significant [p = .000] in the group I than group II.

CONCLUSION

SZ suture fixation is reliable in reducing fractures ZMC and restoring the increased orbital volume where the fixation of zygomatic arch (ZA) was deemed necessary through latero-posterior approach.

Using the "bottom-up and outside-in" sequence for panfacial fracture management: does it provide a clinical significance?

Panfacial fractures usually refer to simultaneous facial fractures, which affect the upper, middle, and lower thirds of the face. The management of panfacial fracture is complex because of the lack of reliable landmarks. Literature has shown many approaches for management of panfacial fractures. Every segment of bone has a precise function in the repair. Therefore, the "bottom-up and outside-in" sequence is the most widely used approach in the management of panfacial fractures. These facial fractures present remarkable challenges for both experienced and inexperienced surgeons. This article aimed to report a case of a panfacial fracture (mandibular condylar and symphysis fractures associated with an atypical Le Fort III fracture) in a 48-year-old man. The patient was successfully treated using bottom-up and outside-in sequence by accessing all facial injuries. Postoperatively, radiograph examination revealed good reduction and fixation of titanium plates, and physical examination revealed good functional and esthetic outcomes.

Not only "nurture", but also "nature", influence the outcome of zygoma repair

The present study aims to elucidate the relationship between preoperative deviation patterns of fractured zygomas and treatment outcomes. Forty-five randomly selected patients with tri-pod type zygoma fractures were classified into a medial rotation group and a lateral rotation group, depending on preoperative deviation patterns. A minimum of 6 months after the operation, symmetry of the cheek was evaluated by three plastic surgeons using a VAS system. The evaluated scores were compared between the two groups. Furthermore, simulation of postoperative secondary deformity was performed by applying hypothetically defined relapse forces on CAD models produced by referring to the CT data of 20 patients. The deviation values obtained by the simulation were compared between the two groups. The results demonstrate that VAS scores were higher for the lateral rotation group than for the medial rotation group and that the deviation values were higher for the medial rotation group than for the lateral rotation group. It is concluded that treatment outcomes of zygoma fractures are affected by preoperative deviation patterns. Cases with medial rotation are likely to present poorer outcomes than those with lateral rotation.

Digital surgical templates for managing high-energy zygomaticomaxillary complex injuries associated with orbital volume change: a quantitative assessment

PURPOSE

This study sought to introduce 3-dimensional (3D) virtual surgical planning and digital rapid-prototyping templates for zygomaticomaxillary complex (ZMC) injuries associated with orbital volume change and to evaluate the surgical outcomes quantitatively.

PATIENTS AND METHODS

Eight patients who underwent open reduction and fixation for a ZMC injury with orbital volume change were studied. Computed tomographic (CT) scan of the zygomaticomaxillary area was performed before the operation in each case. Scanned data were converted into 3D models using Mimics software (Materialise, Brussels, Belgium) for surgical designs. Virtual surgical reductions and correlated guiding templates were designed using Mimics and Magics software (Materialise). The operations were performed with the help of prefabricated templates to reduce the fractures. A postoperative CT scan of each patient was obtained within 2 weeks after surgery, and quantitative measurements were made to assess the surgical outcomes. Preoperative volumes of the bilateral orbits were compared, and concordance with postoperative volumes of the bilateral orbits was assessed. Twenty-one pairs of distances from 7 marker points to 3 reference planes were measured to assess postoperative facial symmetry.

RESULTS

Volumes of the injured orbits were significantly different from volumes of the uninjured orbits preoperatively (P < .05), whereas bilateral orbital volumes showed no statistically significant difference postoperatively (P > .05). In addition, 19 of the 21 pairs of bilateral distances showed no significant difference postoperatively (P > .05).

CONCLUSIONS

Quantitative assessment showed that digitally designed, rapid-prototyping templates for ZMC fractures have a positive impact on restoring facial symmetry and concordance of bilateral orbital volumes.

Maxillary fragment stabilization after Le Fort I fracture with 1 screw pair per plate

PURPOSE

The aim of the present study was to determine whether plates with only 1 screw pair can be used for Le Fort I fracture management. Good postoperative results motivated the direct application of mandible fixation principles to the fractured midface region without additional experimental research. However, the amount and distribution of the forces in the midface region is different from those on the mandible.

MATERIALS AND METHODS

Testing was conducted on plastic anatomic models. The validity of the experimental model was tested before the fixation techniques were compared. Standard miniplates and miniscrews were used for fixation of the maxilla. The model surface strain analysis was conducted using the noncontact object grating method, which enabled the surface strain measurement without direct influence on the measured model.

RESULTS

In 2 screw pair fixation, the outer screw pair has little effect on the local strain distribution, but it lowers the contact forces along the crack. One screw pair fixation is stable enough for fixation, but it has a greater strain peak at the crack edges.

CONCLUSION

Our results showed that 1 screw pair per plate was enough for stable fixation, and 2 or more screw pairs should only be used when the bone fragment at the fracture site cannot sufficiently transmit forces along the crack.

Combined fixation with plates and transmalar Kirschner wires for zygomatic fractures

After repair of a fractured zygoma, the fixed zygoma occasionally becomes displaced. This phenomenon--generally called "relapse"--is a complication that can be prevented by fixing plural sites with plates. However, this impairs blood supply to the bone, which causes atrophy. To solve this dilemma, we developed a new concept for fixing the zygoma. Fractured zygomas are fixed by combining plate fixation at a single site with transmalar fixation with Kirschner wires. This secures stability of the fixed zygoma without impairing its blood supply. We evaluated the stability of fractured zygomas fixed by our method by doing dynamic experiments using simulation models. The stresses at the screw-bone interfaces were significantly reduced by the additional transmalar fixation with wire, indicating that zygomas fixed by our method are less likely to relapse than zygomas fixed with a single plate. We also reviewed the outcomes of patients treated by our method, which indicates its clinical usefulness.

Experimental evaluation of relapse-risks in operated zygoma fractures

OBJECTIVES

Prevention of relapse, or postoperative dislocation, of the fixed zygoma is necessary to achieve optimal results in the treatment of zygoma fractures. Assuming that the occurrence of intensified stresses on mastication at the screw-bone interface (SBI) constitutes the essential cause of the relapse, we evaluated the stresses for three different fixation methods-fixation at the frontal process (FP), inferior orbital rim (IOR), and zygomatico-maxillary buttress (ZMB).

METHODS

We used 10 computer-aided design (CAD) models simulating zygoma fractures in the experiment. For each CAD model, we fixed the fractured zygoma with four screws and one mini-plate at the FP, IOR, or ZMB. After applying a 5.5kg force simulating mastication, we calculated the intensity and distribution patterns of the stresses occurring at the SBIs of the fixation screws using the finite element method. Thereby, we evaluated dynamic stability of the fixed zygoma for each of the three fixation methods.

RESULTS

Greater stresses occur at the SBIs with IOR fixation than at those with FP and ZMB fixation. Although the stresses occurring at the SBIs on mastication demonstrated evenly distributed patterns with the FP and ZMB fixation, the stresses demonstrated concentration on one screw with the IOR fixation.

CONCLUSIONS

The fixed zygoma is more likely to cause relapse with the IOR fixation than with the FP or ZMB fixation. Hence, in performing zygoma fixation at the IOR, care should be taken to minimize the likelihood of postoperative relapse that is caused by skewed distribution of the stresses on the fixation screws.

Appropriate diameter for screws to fix the maxilla following Le Fort I osteotomy: An investigation utilizing finite element analysis

BACKGROUND

After Le Fort I osteotomy, there is sometimes a secondary deformity (relapse), with the lower segment deviating from the intraoperatively fixed position. It is hyopothesized that the structural stability of the reconstructed maxilla is affected by the diameter of the fixation screws. The present study aims to elucidate the relationship between the diameters of the screws and the structural stability of the maxilla after Le Fort I osteotomy.

METHODS

3D models were produced on a workstation from 20 dry skulls and a Le Fort I operation was simulated on them. The upper and lower segments of the divided maxilla in each of the 20 models were connected using four plates and 16 screws. Five different diameters of the fixation screws were tested. Thus altogether 100 models were produced. A 180N load was applied to the molar region for each model. Using finite element analysis, the resultant stresses and deviations of the lower segments were calculated. Finally, referring to these values, the relationships between screw diameters and stability of the lower segment were evaluated.

RESULT

The stability of the lower segment was greatest when the diameter of the fixation screws was equal to the thickness of the bone at each fixation site.

CONCLUSION

In performing Le Fort I osteotomy, it is recommended that bone thickness is measured at each fixation site in advance, and the diameter of the fixation screws matched accordingly; thereby optimum stability of the reconstructed maxilla can be anticipated.

Computed tomography pseudofractures of the mid face and skull base

Thin-section multislice CT delineates numerous normal skull-base and mid-facial bony discontinuities. These represent sutures, fissures and neurovascular foramina or channels, and should be differentiated from fractures. This pictorial review describes and illustrates the characteristic location and multiplanar CT appearances of these structures. Their clinical significance in terms of pathological processes and surgical planning are discussed.

Simplified Repair of Zygomatic Fractures through a Transconjunctival Approach

OBJECTIVE

To describe a simplified technique of zygomatic fracture repair.

DESIGN

Retrospective, noncomparative case series with description of a surgical technique.

PARTICIPANTS

Twenty consecutive patients with zygomatic fractures undergoing repair with the described technique.

INTERVENTION

Fracture repair was accomplished with a technique that used a T-bar screw for reduction through a transconjunctival approach.

MAIN OUTCOME MEASURE

Successful fracture reduction.

RESULTS

Twenty patients with zygomatic fractures underwent successful reduction with the simplified technique. No complications were observed.

CONCLUSIONS

The use of the T-bar through a transconjunctival approach is a simplified and effective technique for zygomatic fracture repair.

Biomechanical analysis of the rigid fixation of zygoma fractures: an experimental study

In this experimental study, the goal was to test the sufficiency of actual fixation plates in zygomatic complex fractures and the efficiency of a modified plate at the zygomaticofrontal suture in a suitable model, which was designed for biomechanical study. To address this issue, a zygomatic fracture model produced by using a cadaveric cranium was simulated and the fractures were fixed by the actual and modified fixation materials. The force simulating masseter muscle pull was applied with the Lloyd material testing apparatus, and the rotation of the zygoma was determined using displacement transducers. In this study, there were three different experimental groups. Although miniplates at the zygomaticomaxillary buttress and microplates at the infraorbital rim were used in all three groups, three different plates (miniplate, microplate, and modified plate) were used at the frontozygomatic suture in these groups. Rotational displacement of the zygoma with the effects of simulated masseter muscle force was determined. According to the results obtained, microplates are not effective in stabilizing the frontozygomatic suture when the masseter muscle forces are within physiological range. Although miniplates stabilize zygomatic complex fractures, it was shown that modified microplates, which have no ondulation along the plate border, have a higher resistance to rotation than that of the conventional plates. The rotation angle at the instant of fracture with microplates was 4.59 degrees, and that with miniplates was 1.26 degrees. The maximum rotation angle with modified microplates was 0.32 degrees. Modified microplates designed for the fixation of fractures in the zygomatico-orbital region have been shown to be suitable in a well-designed experimental model and might be appropriate for clinical use.