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].