Discussion
The present study presented the state-of-the-art with presentation of a meta-analysis of the last ten years of publications of clinical studies on the use of 1-point fixation for fractures of the ZMC, both with the use of non-absorbable plates and bioabsorbable. The results of these studies showed in a general way that the use of 1-point fixation presented good results in the short, medium and long term, showing fracture stability, with or without open reduction. Complication rates were low and patients’ satisfaction with aesthetics was considerable.
The studies of the present work also showed that the use of three-dimensional photogrammetric analysis and the ultrasound-guided technique can greatly favor the procedure and, in addition, they also showed that the use of biodegradable plates can offer good advantages, given that they showed equal stability of the fracture when compared with conventional plates. In this sense, achieving satisfactory results in the treatment of complex fractures of the middle and zygomatic maxillary face involves a series of decisions that include the approach of the zygomatic arch as the main point of treatment. In addition, a distinct pattern of fractures can generate more challenges to achieve satisfactory results.
The ZMC plays a fundamental role in the structure, function and aesthetic appearance of the facial skeleton. They can be responsible for approximately 40% of midface fractures. They are the second most common facial bone fracture after injuries to the nasal bones [3]. The fracture complex results from a direct impact on malar eminence and results in three distinct fracture components that interrupt the anchorage of the zygoma. In addition, the fracture components can result in temporal muscle shock, trismus (difficulty in chewing) and compromise the foramen / infraorbital nerve, resulting in hypesthesia in its sensory distribution [4].
In this context, a study performed a four-year retrospective review of all patients treated for ZMC fractures in the department of oral and maxillofacial surgery. A total of 245 patients were identified for fractures of the ZMC. Closed or open reduction methods were performed in order to treat the preservation of normal facial structure, sensory function, globe position and chewing functionality. Significant facial asymmetry that requires surgical revision occurs in 3-4% of patients. Postoperative infection rates have proved to be extremely low, and these infections almost always resolve with oral antibiotics. Thus, the long-term prognosis after repair of ZMC fractures is usually very good [5].
In this scenario, no clinical consensus was reached regarding the number of fixation points required when performing open reduction and internal fixation. A retrospective study of 211 patients over a 20-year period looked at the usefulness of single-point fixation in the treatment of ZMC fractures. The average follow-up time was 3.4 months. Of the 211 patients, 162 with ZMC fractures were treated with single-point fixation. During the follow-up period, 1 patient suffered tooth loss because of a root present in the fracture line, 7 experienced intraoral exposure of the plaque, with 2 subsequently in exchange for the plaque and 8 developed wound infection. No patient required orthognathic surgery or cheek implant for malar asymmetry. No patient developed hypoglobus or enophthalmia, and none required a review of the internal fracture fixation [6]. Despite this, there is still controversy as to the ideal degree of exposure, reduction and anatomical fixation required during open reduction and internal fixation of fractures of the ZMC [7].
In addition, a prospective controlled study functionally assessed the behavior of the masticatory muscles (masseter and temporal) after fractures of the ZMC, evaluating the strength of the bite, the electromyography (EMG) and the mandibular movements. Group I consisted of 20 patients with unilateral fractures of the ZMC who were treated surgically with fixations of one, two or three points in the frontozygomatic, infraorbital or zygomatic maxillary buttress region. The control group in group II included 20 normal patients. Muscle activity was functionally assessed before and after surgery for a period of 6 months. The evaluation consisted of measuring the bite force, EMG analysis of the masseter and temporal muscles and measures of the mandibular movements. There was an increase in bite strength and electromyographic activity over the evaluated postoperative period, but at the end of 6 months, the values ​​were still below the control levels for most patients. The maximum mouth opening increased considerably after surgery. According to the bite force and the EMG, the masticatory muscles returned to almost normal levels in the third month after surgery, mainly with 1-point fixation. Thus, this study supports the current clinical concept of minimized fixation in the treatment of ZMC fractures [8].
In addition, fracture of the zygomatic tripod is relatively common and usually requires open fixation with internal reduction through several incisions. However, the lateral incisions of the eyebrow sometimes leave unpleasant scars and, therefore, one point fixation can be used through a bucco-gingival incision to not leave scars in selected cases. Thus, a 5-year retrospective study with 30 patients compared the fixation of 1 point in the ZMC with the fixation of 2 points in the ZM and frontozygomatic (FZ) areas in tripod fractures. We investigated 14 patients with fixation of 1 point in the ZMC (group 1), 1 of whom had bilateral tripod fractures and 16 patients with fixation of 2 points in the ZM and FZ area (group 2). Of the 16 patients in group 2, 10 (63%) complained of ugly scars at the site of the lateral incision of the eyebrow, while none of the patients in group 1 complained of external scars. None of the patients complained of bone movement and pain in the FZ area in both groups. In group 2, 4 of 16 patients (25%) complained of palpability in the FZ area, while none in group 1 complained of palpability. The satisfaction score for the surgery was 9.4 ± 1.6 in group 1 and 7.7 ± 2.6 in group 2 (p <0.05). In addition, two patients underwent surgery to remove plaque in group 2. None of the patients in group 1 complained of aesthetic problems, without fixation in the FZ area [9].
Zygoma is an important buttress of the medial-facial skeleton, which is often injured due to its prominent location. Zygoma fractures are classified according to Knight and North based on the direction of anatomical displacement and the pattern created by the fracture. In fractures of the ZMC, many incisions, such as the lateral eyebrow, upper lateral blepharoplasty, transconjunctival, subciliary, subciliary, subversal, intraoral and direct percutaneous approaches are useful [13].
Therefore, a study analyzed the cases of lateral incision of the forehead and fixation of 1 point and introduced the criteria for applying this selective approach. Among 70 patients with tripod fractures, 14 patients (20%) underwent the 1-point fixation technique through lateral incisions of the forehead. The preoperative and postoperative displacements of the infra-orbital border were measured radiologically. Of these patients, 7 cases (50%) were type III, 6 cases (43%) type IV and 1 (7%) type V, according to Knight. and North Classification. Simple fracture of the infra-orbital border was observed in 10 patients (71%) and crushed fracture was observed in 4 patients (29%). In 11 patients, the front zygomatic sutures were fixed with square microplates with 4 holes and 0.5 mm thick, and straight mini plates with 4 holes and 1.0 mm thick were used in 3 patients. Of the 14 tripod fractures, 6 (43%) were associated with floor fractures. Seven had displacement of the infraorbital border (range 2.0-7.6 mm; mean, 4.6 +/- 0.8 mm), and the other 7 had no displacement of the infraorbital border. After surgery, the deformities of the steps at the infraorbital edges were improved. All 14 patients were satisfied with the postoperative appearance [10].
Another 2019 retrospective study evaluated the results of stability and aesthetic appearance of fixing a point using a three-dimensional photogrammetric analysis. In nine months of medical record analysis, 34 patients with ZMC fractures were treated by fixing a point on the ZM buttress using non-sintered hydroxyapatite (u-HA) / poly-L-lactide (PLLA) plates. The differences in the inter-malar height of the soft tissues between the fractured side and the non-fractured side were assessed by photogrammetric analysis with a three-dimensional camera (Morphius®) preoperatively and 1 week, 1 and 3 months after surgery. All patients achieved satisfactory bone stability and a symmetrical malar appearance. There was no statistically significant difference between 1 and 3 months after surgery. The comparison of differences in inter-malar bone height revealed a statistically significant difference between before and 6 months after surgery (p <0.01). Therefore, the use of three-dimensional photogrammetric analysis for fixation to a point of the ZM buttress using a u-HA / PLLA plate produced reliable, satisfactory and safe clinical results in patients with ZMC fractures [14].
In addition, a prospective study with 24 patients analyzed the precision and postoperative stability of the 1-point ultrasound-guided fixation in the ZM buttress for the treatment of ZMC fractures, without fracture separation in the frontal process of the zygomatic bone. The authors used titanium plates in the first 6 cases and biodegradable plates in the remaining 18 cases. The results suggested that the fixation of 1 point guided by ultrasound in the ZM buttress can provide an accurate reduction of the fractures of the ZMC without the separation of the frontal process of the fracture of the zygomatic bone. In addition, fracture stability has been established, even with the use of biodegradable plates [15].
Also, a randomized study with 20 patients performed to compare the fracture stability of the ZMC using biodegradable plates and titanium miniplates with fixation at one point. Patients with fractures of the ZMC were randomly selected and divided into two groups, which were divided into two subgroups. Group I patients were treated with a titanium miniplate in the zygomatic buttress and group II was treated with bio-resorbable plates. The fixation of a point was carried out in the zygomatic buttress or in the frontozygomatic suture and it was observed that the site has been the most preferred site for rigid internal fixation in terms of stability, aesthetics and prevention of rotation of the fracture segment, vertical or horizontal axis. There was no significant difference in postoperative results between two groups, but the system still bioresorbable has some advantage over the titanium system, as these plates reabsorb for a period of time and do not interfere with growth and postoperative radiotherapy [16].
Still, the reduction and fixation of the zygomatic arch is a key point in the treatment of complex fractures of the middle face and zygomatic maxillary. High-impact frontal trauma can cause posterior displacement of the zygomatic bone, with a sagittal fracture of the root of the zygomatic arch extending posteriorly to the glenoid fossa. The fixation of the mini-plate and screw of this fracture requires a great detachment of soft tissues, being technically more difficult for an adequate fixation and increasing the risk of damage to the soft tissues. Therefore, a study described an operative approach for fixing this type of fracture using an adaptation of the delay screw technique. After the initial reduction of the zygomatic bone, the proximal segment of the zygomatic arch containing the sagittal fracture is anatomically reduced and a 2.0 mm titanium screw is placed with a lower inclination of 10 ° to 15 ° in the mastoid cells of the temporal bone, thus avoiding the placement of intracranial screws. Thus, excellent results in reduction and long-term stability were presented, it facilitates the surgical procedure, reduces the risk of damage to soft tissues and can reduce costs in comparison with the conventional mini-plate and fixation by screws [17].