Establishment of a new method for quantitative diagnosis of zygomatic complex fractures with three dimensional CT
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《中华医药杂志》英文版
Establishment of a new method for quantitative diagnosis of zygomatic complex fractures with three dimensional CT (pdf)
1 Department of Oral and Maxillofacial Surgery, the Ninth Affiliated Hospital of Shanghai Second Medical University,Shanghai 200011,China
2 Department of Stomatology, the Affiliated Hospital of Xuzhou Medical College,Xuzhou,Jiangsu Province 221002,China
Correspondence to SUN Yu-hua,Department of Stomatology, the Affiliated Hospital of Xuzhou Medical College,Xuzhou,Jiangsu Province 221002,China
E-mail:endoscope-syh@yahoo.com.cn
[Abstract] Objective To establish an available CT metrical method for quantitative diagnosis of zygomatic complex fractures and deformities.Methods Three dimensional CT images of 15 patients with zygomatic fractures were measured and analyzed by computer-assisted measurement system and software of e-film before and after operation to diagnose the displacement in three dimension and deformities of the fractures. The displacement in three dimensions of the fractured zygoma was obtained before operation. CT data was copied from PACS of the Ninth Hospital of Shanghai and measurement was carried on personal computer. Anthropology points of other bones including contra-lateral non-fractured zygomatic bone were used in this method. The distance of the two point on zygomatic bone and other bone in the same lateral was get first, then the difference of the two distance of the fractured lateral and the non-fractured contra-lateral respectively was calculated as the displacement of the fractured bone of the patient. At last, we use paired t test to compare the data of the displacement of the zygomatic bone before operation with those after operation and then evaluation thus consists of two sides: clinical therapy of the patient and practice value of the CT metrical method were established.Results Using anthropology points, computer-assisted measuring system and e-film software, a new method was established to access the displacement of the zygomatic fractures.Displacement of zygomatic fractures was approximately diagnosed by measuring different angle of 3D CT photographs. The main directions of the displacement of the fractured zygoma concerned in this project are backward (mean 5.48 mm) and interward ( mean 1.40 mm). Sometimes they were accompanied with a rotation displacement. After operation most of the displacements are disappeared as a result ( P<0.01) and all the patients got a one step healing of the bone. Their appearances are symmetry in three dimension and function of open mouth and bite are satisfied. Conclusions The 3D-CT measurement with e-film software newly built by the author is an accurate, reliable and feasible method in clinic for diagnosing zygomatic fractures. A new classification of the zygomatic complex fracture is recommended in this paper
[Key words] zygomatic-maxillary complex fracture; RIF; CT measurement
INTRODUCTION
Zygomatic-maxillary complex(ZMC)which is located in the midface laterally determined the cubic structure of the facial figure in three dimension:the width, protrude and height of the face[1].The malar bone play an important role in the maintenance of the function of appearance, attachment of masticatory muscles and as a transmitting of occlusal force. But it is the most likely bone in the facial region to be fractured in the accidents because of its prominent shape. Statistics data indicated that the incidence rate of the ZMC fracture is about 18%~43.9%, which is more than other bone in the midface region. With the rapidly increasing traffic accidents, both the incidence rate of the ZMC fracture and the severe degree are in an ascending trend recently. Zygomatic bone has a close relationship with its neighbor bone such as maxillofacial bone, temporal bone, frontal bone and sphenoid bone. So ZMC fractures are often accompanied by adjacent bone fracture especially when the trauma is caused by a direct strong force with high velocity. Based on the instance above, there are lots of terms for such fractures: zygomatic complex fracture, orbital maxillary zygomatic fracture, zygomatic maxillary complex fracture, zygomatic -lateral orbital fracture, orbital zygomatic fracture etc.[1～5], of which zygomatic complex fracture is often used. Symptoms caused by the fracture such as collapse of lateral face, trismus, diplopia and numbness in the suborbital region will at last have a bad effect on the normal live and social activities of the patients if can not be treated correctly in time. Because of having not reduction or fixation in time, inappropriate treatment, after the swell time, the abnormal healing, absorption of the fractured bone, contraction of the scar will create the late deformities of malar bone, its adjacent organ and soft tissue as well. This is called following deformities of zygomatic complex fracture. The incidence rate of asymmetry of the face after operation of zygomatic complex fracture is about 12.4%～22%[6,7]. Severe deformities can bring the patients huge psychological stress and the dysfunctions of the face as well. So, improvements of the therapy effect of the fractured zygomatic bone will have a very important meaning for the rehabilitation of such patients.
With the development of the computed tomography from the fourth generation to the fifth generation and the electronic bundle computed tomography, the measurement function of CT has been applied to clinical work gradually and extensively. Survey of the normal bone and quantitative diagnosis of the fractured bone and heredity abnormalities are the most interested area by now.
Zygomatic fracture disconnected all the junctures with other bone and the displacement can result in insufficiency of the malar protrude and changes in the width of the midface. Fractures have not been treated with a correct reduction and fixation within three months is called old or late fractures [8]. Such fractures can not be operated easily to get a symmetrical midface because of absorption at the fracture line and rebuilding of the scar after the experienced reduction there will be about 10%～15% deformities remained still [9～10]. We use the computer-aided CT measurement to get a quantitative diagnosis before operation to improve the veracity of the reduction. According to our experience, this method is indicated to be useful for cut down the remained abnormalities after the operation.
PATIENTS AND METHODS
Clinical Data
All the fifteen cases are the unilateral zygomatic fractures,11 male and 4 female. The ages are from 24 to 71 years old with an average of 36. Among them 12 patients were injured by traffic accidents and 2 by labour wound, 1 by sports movement. All the patients got a primary healing after an operation of open reduction and rigid internal fixation with pure titanium plate. The follow up periods are from 3 to 9 months. Satisfying results were achieved both in appearance and in function side.
Establishment of Coordination
X axis is the line passed through the both central points (point A and point B) of the two condyles. The direction of the line is right.
Y axis is the line passed the point of the nose in the image and is upright to the X axis. The crossing point is defined as the original point O.
Definition of Figure Point and Angular of Bone (Figure 1~4 )
The concave point behind the zygomatic bone (C): the most concaved point behind the root of the temporal process of the zygomatic bone.
The concave point entad to the zygomatic bone (D): the most inferior point of the orbital surface of the zygomatic bone.
The most protrude point of the zygomatic bone (E): the most fronterior and outside point of the zygomatic point.
The front point of the zygomatic bone (F): the most fronterior point of the zygomatic point.
The lateral point of the zygomatic point (G): the most lateral point of the zygomatic point.
The central point of the zygomatic point (H): the geometrically central point of the zygomatic.
Observation Index
X: displacement toward the central line, central direction is positive, lateral direction is negative;
Y: backward displacement;
Z: downward displacement.
Using the Software
Run the windows XP and installs the e-film application programme (Figure 1),place the data disk with dicom style into the CD driver. Using the metrical functions of the e-film software we can get the distances of any two points and the angles between the two lines on the images.
Calculating the Displacements
Compare the distance of the two marked points on the suffered lateral with the distance of the two marked points on the healthy lateral. The difference of the two distances is the displacement of the fractured bone. Measure the angle between the marked line of the zygomatic bone with the X or Y axis of the coordinator system described above. Calculate the difference of the two counterpart angles on the suffered zygomatic bone and the healthy zygomatic bone separately, we get the rotation of the fractured bone. The results can provide the surgeon a quantitative guide before the operation and an evaluation index of the treatment as well.
RESULTS
Evaluating Effect of Reduction
All the patients had a CT examination a week after operation. Using the healthy lateral as index, we measure the remained displacement of the fractured bone in three dimension with the method described above. Compare the results with the displacement before operation to have an evaluation on the effect of the surgery (Table 1).
The mean backward displacement before operation is 5.48 mm,after operation it became 1.40 mm only. Have a t-test of the two group of displacement data, the t value is 13.26, and P<0.01, which suggest a significant difference statistically.
The mean entad displacement before operation is 2.92 mm, after it reduced to 1.20 mm only. The t value of the two group of displacement data is 8.76, and P<0.01, which showed a statistically significant difference.
Most of the vertical displacements of the fractured zygomatic bone are slightly downward except one case is 2.8 mm. There is no statistical difference between these groups.
We take the criterion of the displacement not to be more than 2 mm both in backward direction and lateral direction for symmetry in three dimension [10～12].If one is more than 2 mm, and another is less than 2 mm, the figure is basic symmetry. If the two displacements are still more than 2 mm after operation, it is asymmetry in three dimension.
Among the 19 cases, only one patient is in basic symmetry. Others achieved a three dimensional symmetry. There is no patient in asymmetry.
Evaluations of Maxillofacial Appearance after Operation
Take photos of the patients at a face upward position three months after operation to see the restoration of the soft tissue. The figures are symmetry either (Figure 4~8). The width of the midface of one patient is slightly increased because of the incrassation of soft tissue.
Figure 1 Software appearance
Figure 2 Mark point
Figure 3 Coordinating Figure 4 Measuring Figure 5 Before operation Figure 6 After operation Figure 7 Before operation Figure 8 After operation
Note:Female, 22 years, 20 days after traffic accidents
Table 1 Comparing the Displacement Before Operation with After Operation (mm)
DISCUSSION
The zygomatic complex fracture is often accompanied by the backward and displacement entad of the bone. Sometimes there will be a rotation and downward displacement. The distance and direction of displacement suggested the severity of the trauma and the magnitude and direction of the force causing the wound.
The therapy results of corrections of the deformities of the zygomatic complex fracture are usually not satisfying. Although we have high definition CT for diagnosis and modern cranio-maxillofacial surgery techniques are utilized for reduction and fixation, there are still facial deformities, encephalocele and remained dysfunction of masticatory muscles[13,14].The reasons may be the error of reduction caused by the bone defects and absorption of the bone near the fracture line. And the lack of definite criterion for reduction, stiffness of soft tissue, irregular incrassation and the influence of scar will have effect on the results.
Different patients may have different severities in the zygomatic complex fractures. So only comparing the combined symptoms after operation without considering the difference severity of difference patients will not produce a good result to evaluate the therapy method.
So we bring forward a new classification of zygomatic complex fracture based on the degree of severity. Light fracture or Ⅰ° fracture means the displacement not more than 2 mm in any direction. The moderate fracture or Ⅱ° fracture means the displacement between 2 mm and 5 mm in any direction. The severe fracture or Ⅲ° fracture means the displacement between 5 mm and 8 mm in any direction. The extremely fracture or Ⅳ° fracture means the displacement more than 8 mm in any direction.
The displacement presents the different magnitude of the energy in the trauma. Compare the combined symptoms and the treatment results of the patients in the group of same severity will be much more meaningful. For Ⅰ° degree fracture, we cannot do operation if there is no malfunctions and wait for the natural healing. Fractures more than Ⅰ° should be operated and fixed through minimal incision or semi-coronal incision, even coronal incision if necessary. The fixation position may be suborbital rim, zygomatic maxillary buttress, zygomatic frontal suture and zygomatic temporal suture. For Ⅲ or IV degree fractures having decreased sight power or combined with frontal bone fracture or temporal bone fracture, consultation to the department of ophthalmology and department of neurology surgery is very necessary and helpful.
We use the e-film software and CT data from the Affiliated Ninth Hospital of the Shanghai Second Medical University to get the displacement of the fractured bone after measuring the difference of the protrude of the malar bone between the fractured lateral and the healthy lateral. During operation, we can drill two holes on the two ends of the fractured bone separately. Then we make an exactly quantitative reduction of the bone according to the quantitative diagnosis before operation.
According to the literature, there are a lot of methods for improvement of the accuracy of reductions of the fracture. There are computer aided design and simulation system for operation, computer aided stereo navigation system and techniques of three dimensional rapid prototyping of head model as well. The computer aided design and simulation system for operation can provide us a quantitative or a semi-quantitative diagnosis for the fracture or the deformities. It can also simulate the process of the operation and predict the result of the surgery as well. But the quantitative results cannot be directly applied to the operation process yet by now. Failkov[9] reported a stereo orientation system with occlusion plate and a lathe-hedd fixed by an earplug. In this system, he had the CT scan of the patients with the lathe-hedd with which he made the quantitative movement of the fractured bone. This method increase the difficult of the operation at the same time and was restricted for the patients having an unsteady occlusion plane because of the fractured maxillary, the patients with trismus and the patients very young. Others reported the computed aided stereo navigation system with magnetic sensor and infrared ray positioning devices[14～17].But the technique is too complex and costs too much. We use the CT measurement system combined with the mark point method during operation for the treatment of the severe zygomatic complex fractures. We can get a quantitative diagnosis before operation and make an exactly quantitative movement during surgery. The method is relatively simple and adds no more pain to the patients and is supported by the good clinical report to be well.
A study by Gruss [13]indicated that the sink or protrude of the malar bone is the reason of insufficiency of the reconstruction of the protrude and shape in midface region. He thought that exact reconstruction of the relationship of zygomatic bone with the skull base and midface is the key point of the treatment of complex fractures in midface region and the abnormalities caused by old zygomatic complex fractures. He suggested the coronal images of computed tomography to evaluate the difference degree of the bilateral sink and protrude. Because the rotation of the bone always takes the zygomatic frontal suture as the axis, the displacement is the smallest one, in this region, the largest one in suborbital region and zygomatic maxillary region. We find that the main reason of the zygomatic complex fracture and deformities is the disappearance of the figure protruding point caused by the displacement of the convex point of the malar bone. The operation is the process to reconstruction of the convex point.
The evaluation of the effect of the operation of the reduction on the zygomatic complex fractures, measurement and compare the protrude degree can also be practiced through the computed aided reverse engineering which can provide the images of fractured lateral from the images of healthy lateral only. The results are much more apparent.
The incrassation of the soft tissue can compensate the insufficient of the reduction of the fractured bone in some cases. In one case, because of such incrassation the width of the midface increased slightly after operation. This phenomenon indicates that the abnormalities of soft tissue are other important reasons of the complications after operation. To resolve such problem, we can take a second stage surgery to abrade a part of the bone surface or implant a pad with biomaterials such as medpore. We can use the rapid prototyping techniques to simulate the operation on the head model, move the bone pieces and implant the bone or shape the titanium plate as well of the patients who suffered a severe comminuted zygomatic complex fractures. In these cases, measurement becomes difficult because of the disappearance of the figure point and lots of displaced bone pieces.
We find that the quantitative diagnosis is too difficult for severe comminuted zygomatic complex fractures. The reasons may be as following:(1) the body of the malar bone is round and connected tightly with adjacent bones;(2) the displacement of the bone pieces are in all directions and the mark point cannot be determined;(3) often combined with counter lateral zygomatic fractures which make the reference point impossible;(4) the coordination cannot be established on the deviated central line because of the trauma force from one lateral to the other lateral. But for most of the cases suffered unilateral zygomatic complex fractures, this simple and credible method is can provide the surgeon the quantitative diagnosis and thus has a very important value in practice.
REFERENCES
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2. Shaw GY,Khan J. Precise repair of orbital maxillary zygomatic fractures. Arch Otolaryngol Head Neck Surg,1994,120:613-619.
3. Makowski GJ, Van Sickels JE,Antonio S, et al. Evaluation of results with three point visualization of zygomaticomaxillary complex fractures. Oral Surg Oral Med Oral Pathal,1995,80:624-628.
4. Zingg M, Chowdhury K, Ladrach K,et al. Treatment of 813 zygoma lateral orbital complex fractures. Arch Otolaryngol Head Neck Surg,1991,117:611-620.
5. Jackson IT. Classification and treatment of orbito_zygomatic and orbito-ethmoid fractures:The place of bone grafting and plate fixation. Clin Plast Surg,1989,16:77-91.
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12. Wagner A,Millesi W, Watzinger F, et al. Clinical experience with interactive teleconsultation and teleassistance in craniomaxillofacial surgical procedures.J Oral Maxillofac Surg,1999,33:1413.
13. Gruss JS,Van Wyck L,Phillips JH,et al.The importance of zygomatic arch in complex midface fracture repair and correction of posttraumatic orbitozygomatical deformities.Plast Reconstruc Surg,1990,85:878.
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(Editor Emilia)(SUN Yu-hua1,2,TANG You-sh)
1 Department of Oral and Maxillofacial Surgery, the Ninth Affiliated Hospital of Shanghai Second Medical University,Shanghai 200011,China
2 Department of Stomatology, the Affiliated Hospital of Xuzhou Medical College,Xuzhou,Jiangsu Province 221002,China
Correspondence to SUN Yu-hua,Department of Stomatology, the Affiliated Hospital of Xuzhou Medical College,Xuzhou,Jiangsu Province 221002,China
E-mail:endoscope-syh@yahoo.com.cn
[Abstract] Objective To establish an available CT metrical method for quantitative diagnosis of zygomatic complex fractures and deformities.Methods Three dimensional CT images of 15 patients with zygomatic fractures were measured and analyzed by computer-assisted measurement system and software of e-film before and after operation to diagnose the displacement in three dimension and deformities of the fractures. The displacement in three dimensions of the fractured zygoma was obtained before operation. CT data was copied from PACS of the Ninth Hospital of Shanghai and measurement was carried on personal computer. Anthropology points of other bones including contra-lateral non-fractured zygomatic bone were used in this method. The distance of the two point on zygomatic bone and other bone in the same lateral was get first, then the difference of the two distance of the fractured lateral and the non-fractured contra-lateral respectively was calculated as the displacement of the fractured bone of the patient. At last, we use paired t test to compare the data of the displacement of the zygomatic bone before operation with those after operation and then evaluation thus consists of two sides: clinical therapy of the patient and practice value of the CT metrical method were established.Results Using anthropology points, computer-assisted measuring system and e-film software, a new method was established to access the displacement of the zygomatic fractures.Displacement of zygomatic fractures was approximately diagnosed by measuring different angle of 3D CT photographs. The main directions of the displacement of the fractured zygoma concerned in this project are backward (mean 5.48 mm) and interward ( mean 1.40 mm). Sometimes they were accompanied with a rotation displacement. After operation most of the displacements are disappeared as a result ( P<0.01) and all the patients got a one step healing of the bone. Their appearances are symmetry in three dimension and function of open mouth and bite are satisfied. Conclusions The 3D-CT measurement with e-film software newly built by the author is an accurate, reliable and feasible method in clinic for diagnosing zygomatic fractures. A new classification of the zygomatic complex fracture is recommended in this paper
[Key words] zygomatic-maxillary complex fracture; RIF; CT measurement
INTRODUCTION
Zygomatic-maxillary complex(ZMC)which is located in the midface laterally determined the cubic structure of the facial figure in three dimension:the width, protrude and height of the face[1].The malar bone play an important role in the maintenance of the function of appearance, attachment of masticatory muscles and as a transmitting of occlusal force. But it is the most likely bone in the facial region to be fractured in the accidents because of its prominent shape. Statistics data indicated that the incidence rate of the ZMC fracture is about 18%~43.9%, which is more than other bone in the midface region. With the rapidly increasing traffic accidents, both the incidence rate of the ZMC fracture and the severe degree are in an ascending trend recently. Zygomatic bone has a close relationship with its neighbor bone such as maxillofacial bone, temporal bone, frontal bone and sphenoid bone. So ZMC fractures are often accompanied by adjacent bone fracture especially when the trauma is caused by a direct strong force with high velocity. Based on the instance above, there are lots of terms for such fractures: zygomatic complex fracture, orbital maxillary zygomatic fracture, zygomatic maxillary complex fracture, zygomatic -lateral orbital fracture, orbital zygomatic fracture etc.[1～5], of which zygomatic complex fracture is often used. Symptoms caused by the fracture such as collapse of lateral face, trismus, diplopia and numbness in the suborbital region will at last have a bad effect on the normal live and social activities of the patients if can not be treated correctly in time. Because of having not reduction or fixation in time, inappropriate treatment, after the swell time, the abnormal healing, absorption of the fractured bone, contraction of the scar will create the late deformities of malar bone, its adjacent organ and soft tissue as well. This is called following deformities of zygomatic complex fracture. The incidence rate of asymmetry of the face after operation of zygomatic complex fracture is about 12.4%～22%[6,7]. Severe deformities can bring the patients huge psychological stress and the dysfunctions of the face as well. So, improvements of the therapy effect of the fractured zygomatic bone will have a very important meaning for the rehabilitation of such patients.
With the development of the computed tomography from the fourth generation to the fifth generation and the electronic bundle computed tomography, the measurement function of CT has been applied to clinical work gradually and extensively. Survey of the normal bone and quantitative diagnosis of the fractured bone and heredity abnormalities are the most interested area by now.
Zygomatic fracture disconnected all the junctures with other bone and the displacement can result in insufficiency of the malar protrude and changes in the width of the midface. Fractures have not been treated with a correct reduction and fixation within three months is called old or late fractures [8]. Such fractures can not be operated easily to get a symmetrical midface because of absorption at the fracture line and rebuilding of the scar after the experienced reduction there will be about 10%～15% deformities remained still [9～10]. We use the computer-aided CT measurement to get a quantitative diagnosis before operation to improve the veracity of the reduction. According to our experience, this method is indicated to be useful for cut down the remained abnormalities after the operation.
PATIENTS AND METHODS
Clinical Data
All the fifteen cases are the unilateral zygomatic fractures,11 male and 4 female. The ages are from 24 to 71 years old with an average of 36. Among them 12 patients were injured by traffic accidents and 2 by labour wound, 1 by sports movement. All the patients got a primary healing after an operation of open reduction and rigid internal fixation with pure titanium plate. The follow up periods are from 3 to 9 months. Satisfying results were achieved both in appearance and in function side.
Establishment of Coordination
X axis is the line passed through the both central points (point A and point B) of the two condyles. The direction of the line is right.
Y axis is the line passed the point of the nose in the image and is upright to the X axis. The crossing point is defined as the original point O.
Definition of Figure Point and Angular of Bone (Figure 1~4 )
The concave point behind the zygomatic bone (C): the most concaved point behind the root of the temporal process of the zygomatic bone.
The concave point entad to the zygomatic bone (D): the most inferior point of the orbital surface of the zygomatic bone.
The most protrude point of the zygomatic bone (E): the most fronterior and outside point of the zygomatic point.
The front point of the zygomatic bone (F): the most fronterior point of the zygomatic point.
The lateral point of the zygomatic point (G): the most lateral point of the zygomatic point.
The central point of the zygomatic point (H): the geometrically central point of the zygomatic.
Observation Index
X: displacement toward the central line, central direction is positive, lateral direction is negative;
Y: backward displacement;
Z: downward displacement.
Using the Software
Run the windows XP and installs the e-film application programme (Figure 1),place the data disk with dicom style into the CD driver. Using the metrical functions of the e-film software we can get the distances of any two points and the angles between the two lines on the images.
Calculating the Displacements
Compare the distance of the two marked points on the suffered lateral with the distance of the two marked points on the healthy lateral. The difference of the two distances is the displacement of the fractured bone. Measure the angle between the marked line of the zygomatic bone with the X or Y axis of the coordinator system described above. Calculate the difference of the two counterpart angles on the suffered zygomatic bone and the healthy zygomatic bone separately, we get the rotation of the fractured bone. The results can provide the surgeon a quantitative guide before the operation and an evaluation index of the treatment as well.
RESULTS
Evaluating Effect of Reduction
All the patients had a CT examination a week after operation. Using the healthy lateral as index, we measure the remained displacement of the fractured bone in three dimension with the method described above. Compare the results with the displacement before operation to have an evaluation on the effect of the surgery (Table 1).
The mean backward displacement before operation is 5.48 mm,after operation it became 1.40 mm only. Have a t-test of the two group of displacement data, the t value is 13.26, and P<0.01, which suggest a significant difference statistically.
The mean entad displacement before operation is 2.92 mm, after it reduced to 1.20 mm only. The t value of the two group of displacement data is 8.76, and P<0.01, which showed a statistically significant difference.
Most of the vertical displacements of the fractured zygomatic bone are slightly downward except one case is 2.8 mm. There is no statistical difference between these groups.
We take the criterion of the displacement not to be more than 2 mm both in backward direction and lateral direction for symmetry in three dimension [10～12].If one is more than 2 mm, and another is less than 2 mm, the figure is basic symmetry. If the two displacements are still more than 2 mm after operation, it is asymmetry in three dimension.
Among the 19 cases, only one patient is in basic symmetry. Others achieved a three dimensional symmetry. There is no patient in asymmetry.
Evaluations of Maxillofacial Appearance after Operation
Take photos of the patients at a face upward position three months after operation to see the restoration of the soft tissue. The figures are symmetry either (Figure 4~8). The width of the midface of one patient is slightly increased because of the incrassation of soft tissue.
Figure 1 Software appearance
Figure 2 Mark point
Figure 3 Coordinating Figure 4 Measuring Figure 5 Before operation Figure 6 After operation Figure 7 Before operation Figure 8 After operation
Note:Female, 22 years, 20 days after traffic accidents
Table 1 Comparing the Displacement Before Operation with After Operation (mm)
DISCUSSION
The zygomatic complex fracture is often accompanied by the backward and displacement entad of the bone. Sometimes there will be a rotation and downward displacement. The distance and direction of displacement suggested the severity of the trauma and the magnitude and direction of the force causing the wound.
The therapy results of corrections of the deformities of the zygomatic complex fracture are usually not satisfying. Although we have high definition CT for diagnosis and modern cranio-maxillofacial surgery techniques are utilized for reduction and fixation, there are still facial deformities, encephalocele and remained dysfunction of masticatory muscles[13,14].The reasons may be the error of reduction caused by the bone defects and absorption of the bone near the fracture line. And the lack of definite criterion for reduction, stiffness of soft tissue, irregular incrassation and the influence of scar will have effect on the results.
Different patients may have different severities in the zygomatic complex fractures. So only comparing the combined symptoms after operation without considering the difference severity of difference patients will not produce a good result to evaluate the therapy method.
So we bring forward a new classification of zygomatic complex fracture based on the degree of severity. Light fracture or Ⅰ° fracture means the displacement not more than 2 mm in any direction. The moderate fracture or Ⅱ° fracture means the displacement between 2 mm and 5 mm in any direction. The severe fracture or Ⅲ° fracture means the displacement between 5 mm and 8 mm in any direction. The extremely fracture or Ⅳ° fracture means the displacement more than 8 mm in any direction.
The displacement presents the different magnitude of the energy in the trauma. Compare the combined symptoms and the treatment results of the patients in the group of same severity will be much more meaningful. For Ⅰ° degree fracture, we cannot do operation if there is no malfunctions and wait for the natural healing. Fractures more than Ⅰ° should be operated and fixed through minimal incision or semi-coronal incision, even coronal incision if necessary. The fixation position may be suborbital rim, zygomatic maxillary buttress, zygomatic frontal suture and zygomatic temporal suture. For Ⅲ or IV degree fractures having decreased sight power or combined with frontal bone fracture or temporal bone fracture, consultation to the department of ophthalmology and department of neurology surgery is very necessary and helpful.
We use the e-film software and CT data from the Affiliated Ninth Hospital of the Shanghai Second Medical University to get the displacement of the fractured bone after measuring the difference of the protrude of the malar bone between the fractured lateral and the healthy lateral. During operation, we can drill two holes on the two ends of the fractured bone separately. Then we make an exactly quantitative reduction of the bone according to the quantitative diagnosis before operation.
According to the literature, there are a lot of methods for improvement of the accuracy of reductions of the fracture. There are computer aided design and simulation system for operation, computer aided stereo navigation system and techniques of three dimensional rapid prototyping of head model as well. The computer aided design and simulation system for operation can provide us a quantitative or a semi-quantitative diagnosis for the fracture or the deformities. It can also simulate the process of the operation and predict the result of the surgery as well. But the quantitative results cannot be directly applied to the operation process yet by now. Failkov[9] reported a stereo orientation system with occlusion plate and a lathe-hedd fixed by an earplug. In this system, he had the CT scan of the patients with the lathe-hedd with which he made the quantitative movement of the fractured bone. This method increase the difficult of the operation at the same time and was restricted for the patients having an unsteady occlusion plane because of the fractured maxillary, the patients with trismus and the patients very young. Others reported the computed aided stereo navigation system with magnetic sensor and infrared ray positioning devices[14～17].But the technique is too complex and costs too much. We use the CT measurement system combined with the mark point method during operation for the treatment of the severe zygomatic complex fractures. We can get a quantitative diagnosis before operation and make an exactly quantitative movement during surgery. The method is relatively simple and adds no more pain to the patients and is supported by the good clinical report to be well.
A study by Gruss [13]indicated that the sink or protrude of the malar bone is the reason of insufficiency of the reconstruction of the protrude and shape in midface region. He thought that exact reconstruction of the relationship of zygomatic bone with the skull base and midface is the key point of the treatment of complex fractures in midface region and the abnormalities caused by old zygomatic complex fractures. He suggested the coronal images of computed tomography to evaluate the difference degree of the bilateral sink and protrude. Because the rotation of the bone always takes the zygomatic frontal suture as the axis, the displacement is the smallest one, in this region, the largest one in suborbital region and zygomatic maxillary region. We find that the main reason of the zygomatic complex fracture and deformities is the disappearance of the figure protruding point caused by the displacement of the convex point of the malar bone. The operation is the process to reconstruction of the convex point.
The evaluation of the effect of the operation of the reduction on the zygomatic complex fractures, measurement and compare the protrude degree can also be practiced through the computed aided reverse engineering which can provide the images of fractured lateral from the images of healthy lateral only. The results are much more apparent.
The incrassation of the soft tissue can compensate the insufficient of the reduction of the fractured bone in some cases. In one case, because of such incrassation the width of the midface increased slightly after operation. This phenomenon indicates that the abnormalities of soft tissue are other important reasons of the complications after operation. To resolve such problem, we can take a second stage surgery to abrade a part of the bone surface or implant a pad with biomaterials such as medpore. We can use the rapid prototyping techniques to simulate the operation on the head model, move the bone pieces and implant the bone or shape the titanium plate as well of the patients who suffered a severe comminuted zygomatic complex fractures. In these cases, measurement becomes difficult because of the disappearance of the figure point and lots of displaced bone pieces.
We find that the quantitative diagnosis is too difficult for severe comminuted zygomatic complex fractures. The reasons may be as following:(1) the body of the malar bone is round and connected tightly with adjacent bones;(2) the displacement of the bone pieces are in all directions and the mark point cannot be determined;(3) often combined with counter lateral zygomatic fractures which make the reference point impossible;(4) the coordination cannot be established on the deviated central line because of the trauma force from one lateral to the other lateral. But for most of the cases suffered unilateral zygomatic complex fractures, this simple and credible method is can provide the surgeon the quantitative diagnosis and thus has a very important value in practice.
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(Editor Emilia)(SUN Yu-hua1,2,TANG You-sh)