The zygomatic bone is located in the middle third of the face and determines the three-dimensional structure of the facial contour, i.e., the horizontal width, anterior prominence, and vertical height of the midface. Because of its prominent position, it is one of the most vulnerable sites for fracture in head and facial trauma. The zygomatic bone is closely related to the anatomical adjacency of adjacent bones, and a fracture of the zygomatic bone, especially if caused by high velocity direct violence, will inevitably lead to fracture of adjacent bones. The orbital and maxillary bones are most closely related to the zygomatic bone anatomically and are therefore most frequently involved. Based on the above, there are different terms to express these fractures, including: zygomatic complex fracture, orbitozygomatic maxillary fracture, zygomatic maxillary complex fracture, zygomatic lateral orbital complex fracture, and orbitozygomatic fracture. The term orbitozygomatic fracture is mostly used in the current literature. The orbitozygomatic fracture is not fixed by timely repositioning or improper treatment in early stage due to various reasons, and when the swelling subsides, the deformity of the fracture segment due to deformity healing, absorption, scar contracture pulling, causing deformity of the later orbitozygomatic bone and adjacent organs and soft tissue structures, which is called secondary deformity of orbitozygomatic fracture and seriously affects the facial appearance and function.
1, the anatomical characteristics of the orbitozygomatic region orbitozygomatic bone is extremely close in anatomical relationship, the zygomatic bone itself is the outer edge of the orbit, one of the important components of the lower edge, its own position is extremely important to maintain the normal anatomical shape of the orbital bone and orbital volume.
(1) The normal anatomy of the zygomatic bone is located on both sides of the middle 1/3 of the face and plays an important role in maintaining the width, anterior prominence, and vertical height of the face. The zygomatic bone can be divided into two parts: the zygomatic body and the zygomatic arch, and the sutures of the domicile are connected to the frontal bone, temporal bone, pterygoid bone, and maxilla. The zygomatic arch maintains the forward projection of the zygomatic body, and its position between the zygomatic process of the temporal bone and the anterior zygomatic body determines the anterior-posterior, vertical, and horizontal position of the zygomatic bone in relation to the skull base, and constitutes the lateral facial scaffold. The breakage of the lateral facial scaffold directly affects the position of the medial facial scaffold connected by the zygomatic arch. The accurate repair of the zygomatic arch is of great importance in the repair of the complex facial middle 1/3 fractures and orbitozygomatic fractures.
Starting from the lacrimal fossa of the maxilla, outward through the zygomatic body to the zygomatic prominence of the temporal bone constitutes the transverse arch of the face. The accurate repair of the transverse arch is extremely important to maintain the anterior prominence of the zygomatic bone and facial symmetry, and the height of the zygomatic arch determines the width of the face. The deep and superficial layers of the temporal fascia are attached to the outer edge of the frontal eminence of the zygoma and the upper edge of the zygomatic arch. The cheek muscle attaches to the lower edge of the zygomatic arch. The former is important for maintaining the position of the zygomatic bone, while the latter is the most important deformogenic force leading to the fracture displacement of the zygomatic bone after trauma.
(2) Traumatic anatomical features of the zygomatic bone The deformation displacement of the zygomatic bone after fracture is directly related to the magnitude and direction of the traumatic force and the pulling of the chewing muscle. Fractures caused by moderate force mostly occur at the separation of the zygomatic bone from the adjacent bone at the suture junction, which is called ZygomaticComplex fracture or “Three Pillar Fracture”. Severe violence can result in multiple fractures of the entire zygomatic bone, i.e., comminuted fractures. The fracture of the zygomatic complex may result in multiple axial rotational displacements, in addition to upward, anterior, and lateral translations. In the repair of orbitozygomatic fracture deformity healing, it is important to understand the normal anatomical position of the zygomatic bone and its displacement in different quadrants after fracture for accurate anatomical repositioning after osteotomy.
(3) Biomechanical structure of the orbitozygomatic bone and adjacent maxillofacial bones Understanding the biomechanical structure of the maxillofacial bones is an important guide to the selection of osteotomy reconstruction and fixation sites for secondary deformities of the orbitozygomatic bone. Light transmission studies of dry skulls revealed that the middle 1/3 of the facial skeleton is composed of thin and unevenly thickened bone plates. The thicker part of the bone is called buttresses (or Pillars). The maxillofacial buttresses include a vertical and a horizontal buttress system, through which the facial skeleton is constructed as a solid whole to resist a significant degree of violence.
(1) The vertical pillar system of the face The vertical pillars of the face consist of four.
(1) Anteriorly, the Naso-Frontal buttress, which runs anteriorly through the cuspids and the maxillary alveolar ridge along the outer edge of the plagiocephalic foramen up through the medial orbital anterior lacrimal ridge and the maxillary nasal eminence to above the medial orbital rim.
②Laterally, the zygomatic buttress (Zygomatic buttress). From the alveolar ridge above the maxillary first molar upward along the lateral orbital rim to the zygomatic process of the frontal bone and along the temporal process of the zygomatic bone through the zygomatic arch to the temporal bone.
(iii) Posteriorly, the pterygo-maxillary buttress, which runs from the maxillary eminence and pterygo-plate to the skull base.
(iv) Mandibular buttress, from the mandibular body, mandibular ascending branch, and condyle to the temporomandibular joint fossa at the base of the skull.
(2) Horizontal pillar system of the face.
(1) The frontal bone, including the upper portion of the horizontal pillar composed of the supraorbital rim on both sides.
(2) the horizontal pillars of the face: ① the frontal bones, including the inferior orbital rim on both sides and the nasal bones forming the middle part of the horizontal pillars
(3) The palate and the maxillary alveolar ridge form the lower horizontal pillar.
The vertical and horizontal pillars of the maxillofacial skeleton are like the reinforced concrete framework in architecture, which plays a role in linking and reinforcing the maxillofacial skeleton. When a fracture occurs in the maxillofacial bone, the fracture and displacement of the struts often occur. These struts provide an important reference mark for the accurate repositioning of the jaw fracture repair, and are also the choice of the site for strong internal fixation with a small splint. The direction of the small splint must be consistent with the stress direction of each strut in order to obtain an accurate and reliable fixation.
2. The main clinical manifestations and pathogenesis of secondary deformities of orbitozygomatic fractures.
2.1 Concave deformity of the zygomatic maxilla. Depending on the cause of the injury, different degrees of secondary depression deformity can occur. The typical deformities are outward displacement of the zygomatic complex, protrusion of the zygomatic arch, depression of the zygomatic maxilla, widening of the affected side, and downward displacement of the zygomatic prominence, with obvious asymmetry of the bilateral sides.
2.2 Subluxation of the orbital zygomatic fracture is often accompanied by different degrees of inversion of the eyeball. When the eyeball is posteriorly displaced by more than 5 mm, a pronounced entropion deformity can occur.
There are many theories of its pathogenesis, including.
(i) Herniation of intraorbital fat into the maxillary sinus.
(ii) Increase in orbital bone volume due to fracture displacement.
(iii) Fat atrophy or necrosis.
(iv) Posterior displacement of the eye due to scar pulling of the retrobulbar tissue.
(⑤) Insertional obturation or fibrosis of the extraocular muscles.
There is a consensus that post-traumatic entropion is the result of an imbalance between the orbital contents and the bony volume of the orbital bone. Under normal conditions, the specific three-dimensional morphology and size of the orbital bone acts as a limiting constraint on the morphological position of the orbital contents, maintaining the normal anterior protrusion of the eye. When an orbital zygomatic fracture occurs, in addition to the common orbital floor fracture, it is often accompanied by fractures of the medial and lateral orbital walls. The displacement of the fracture fragment not only leads to an increase in the bony volume, but also changes the normal morphology of the orbital contents. Intraocular invagination can be corrected by “retrieving” the “out of place” orbital contents and repositioning them within the normal anatomic definition of the orbital bone. In addition to the above intraocular invagination, there may be varying degrees of downward displacement of the eye due to fracture collapse of the infraorbital rim and orbital floor.
2.3 Adjacent soft tissue deformities after orbitozygomatic fracture are accompanied by different degrees of adjacent soft tissue deformities, such as facial scarring, soft tissue defects, internal and external canthus displacement, etc. Especially if the injury is accompanied by severe contusion and avulsion injury of the face at the time, it often leads to serious facial deformities, which makes treatment more difficult.
2.4 Functional impairment includes.
(i) diplopia, reduced or complete loss of visual acuity, and associated dysfunction due to extraocular muscle imbalance.
(ii) Restriction of mouth opening.
③ sensory numbness or hypoesthesia in the infraorbital region.
④Frontal muscle paralysis or paresis.
3. Etiology and characteristics of secondary deformity of orbitozygomatic fracture.
Due to various reasons, the orbitozygomatic fracture is not effectively treated in time or improperly treated is the main reason for the occurrence of secondary deformity of orbitozygomatic fracture.
The main aspects include the following.
① Early surgical treatment of orbitozygomatic fractures is delayed due to concomitant other fatal injuries, such as severe craniocerebral injuries. It is now recognized that the best time to operate for orbitozygomatic fractures is after the vital signs are stable at the time of injury. Surgery at this time is not only less difficult and less costly, but if treated properly the results are far better than those of phase II surgery, and it is possible to reconstruct the “pre-injury appearence” (Preinjury appearence), if delayed to more than 3w and fibrous healing or even bony healing of the broken bone occurs, the surgery becomes more difficult and the results are difficult to achieve. compared with those treated in the first stage.
② Misdiagnosis or omission occurred due to severe craniofacial swelling at that time, and the examination was not careful and comprehensive, which is another cause of secondary deformity of orbitozygomatic fracture.
(iii) Improper treatment. For unstable fractures with displacement, incision and reliable strong internal fixation were not taken at that time, resulting in inadequate repositioning or unreliable fixation after repositioning, and postoperative displacement secondary to muscle pulling or scar contracture, resulting in deformity of varying degrees at a later stage.
④Surgical complications. Despite the use of advanced techniques and tools in the early stage, some patients still have deformities of varying degrees secondary to the seriousness of the injury at the time and require further revision after surgery.
The diagnosis of secondary deformity of orbitozygomatic fracture has obvious features. It is not difficult to determine the orbitozygomatic fracture, but for the design and implementation of the surgical plan, further auxiliary examinations must be done.
4.1 Radiographs Radiographs should be a routine adjunct to the examination of secondary deformities of the orbitozygomatic fracture. The most commonly used are the tile position and the chin apex position. The tile position helps to diagnose fractures of the maxilla, maxillary sinus, orbital floor, infraorbital rim, zygomatic bone and zygomatic arch, and to understand the healing of the deformity of the zygomatic bone and the presence of herniation of the orbital contents into the maxillary sinus, as well as to observe the presence of fractures of the nasal bone and supraorbital rim. The fracture displacement of the zygomatic arch can be determined by the chin-top position. The fractures of the orbital wall can be roughly understood by orbital tomography. To accurately diagnose fractures of the orbital wall, axial and coronal CT examinations of the orbital bone are required, because some fractures that are not severe on the X-ray may actually occur in the deeper part of the orbit, including the posterior part of the orbital floor, the superior part of the orbital wall, and even the lateral wall of the orbit. The fracture may be more severe in the deeper part of the orbit, including the posterior part of the orbital floor, the superior part of the orbital wall, and even the lateral wall of the orbit.
CT scans, especially the thin axial and coronal tomography provided by high definition CT, can usually identify all major deformities of the traumatized orbital bone, including fractures of the orbital wall and displacement of intraorbital soft tissues into the adjacent anatomical space, providing a reliable basis for the diagnosis of the etiology and surgical design of intraocular invagination. In the past 10 years, CT imaging has been widely used to study the causes of post-traumatic entropion and has made significant progress.
4.3 Three-dimensional reconstruction Three-dimensional reconstruction has been successfully used in the diagnosis and surgical design of various congenital craniomaxillofacial deformities and post-traumatic deformities. Compared with planar CT scan imaging, 3D reconstruction imaging has the characteristics of intuitive and three-dimensional, and the deformity displacement of the orbitozygomatic fracture can be understood at a glance, which helps in the design and implementation of surgery. Although 3D CT is highly intuitive, it still has its limitations in the diagnosis of orbital fractures, as it cannot understand the displacement of the intraorbital soft tissues, and the thin orbital floor and intraorbital wall often make 3D reconstructive imaging of this region very difficult.
5. The modern surgical treatment of secondary deformities of orbitozygomatic fractures is based on the craniomaxillofacial surgical technique founded by Tessier, which consists of the following steps.
5.1 Adequate exposure of the fracture site For severe secondary deformities of the orbitozygomatic fracture, the surgical approach is mostly made through a coronal scalp incision, a submarginal lower eyelash incision, and an intraoral gingival-buccal sulcus incision. In individual patients with significant trauma scar on the zygomatic surface of the infraorbital rim, an incision can also be made through the scar to access the infraorbital rim, orbital floor, and zygomatic maxillary surface without the need for a separate submasculature incision.
5.1.1 Scalp coronal incision: This approach can fully reveal the supraorbital rim, nasal bone, outer orbital rim, zygomatic arch and the upper part of the zygomatic body, and the scar is concealed, so it is the most commonly chosen incision. When using a coronal scalp incision, the key is to protect the frontal branch of the facial nerve from injury. During surgery, the incision should be deep under the capitellar tendon membrane, peel off the surface of the periosteum, lift the superficial temporal fascia along with the scalp when reaching the superior edge of the temporalis muscle, peel off the superficial temporal fascia and the superficial layer of the deep temporal fascia downward, and when approaching the superior edge of the zygomatic arch, the temporal fat pad is visible. The frontal branch of the facial nerve can be properly protected by continuing to dissect downward within the superficial temporal fat pad to reveal the zygomatic arch.
5.1.2 Trans-lower lid incision Manson et al. 1987 proposed a lower lid muscle flap approach via an incision under the eyelash margin. The incision is located 2 to 3 mm below the eyelash margin and extends outward to 8 to 10 mm beyond the outer canthus. The orbicularis oculi muscle is first dissected downward between the orbital septum and the infraorbital rim to 2-3 mm, then the periosteum is incised anterior to the infraorbital rim, and the subperiosteum is dissected to reveal the orbital floor, outer orbital rim, zygomatic bone, and upper maxillary component. When incising the periosteum of the infraorbital rim, the incision should be located anterior to the infraorbital rim to avoid damage to the orbital septum. The orbital septum is attached to the lateral portion of the infraorbital rim in front of the infraorbital rim, and the periosteum must be cut below the septal attachment to avoid postoperative longitudinal shortening of the lower lid.
5.1.3 Intraoral gingival-buccal sulcus approach This approach was first used by Converse (1950) to fully expose the zygomatic bone, maxilla, and infraorbital rim. Care is taken to protect the infraorbital neurovascular bundle and to avoid damage to the opening of the parotid duct. During the repositioning and fixation of the secondary deformity of the orbitozygomatic fracture, this incision allows the repositioning of the maxillary pillar of the zygomatic bone to be examined to prevent any remaining rotational displacement and to provide reliable fixation.
4.2 Osteotomy of the orbitozygomatic fracture For healed orbitozygomatic fracture deformity, the design of the osteotomy is very important to re-establish the symmetry of the face and to correct the inward ocular deformity. In cases where bony healing has not occurred between the broken ends of the bone due to a short post-injury period or soft tissue impaction, a simple approach is to make an incision along the fracture line. However, in cases where firm bony healing has occurred, a special osteotomy is required depending on the healing of the deformity.
In the repair of secondary deformities of the orbitozygomatic fracture, accurate repositioning of the zygoma helps to reconstruct the normal orbital volume. In normal conditions, the equator of the eye is located exactly in the plane from the outer edge of the orbit to the anterior edge of the cardboard of the inner orbital wall. After zygomatic fracture, external rotation displacement of the zygomatic bone or fracture defect of the outer orbital wall can lead to a significant increase in the posterior lateral space of the equator of the eye. The orbital zygomatic bone fracture can be repositioned by osteotomy to correct the external rotation of the outer orbital wall and repair by bone grafting in the outer orbital wall, which can effectively reduce the enlarged orbital cavity, and then correct the inward orbital deformity by deep intraorbital bone grafting.
5.3 After osteotomy and restoration of the secondary deformity of the orbitozygomatic fracture, a reliable strong internal fixation must be used to ensure the stability of the postoperative restoration. The purpose of strong internal fixation is to.
(i) refix the fracture block in its normal anatomic position after osteotomy.
(2) To reconstruct the pre-traumatic load path of the maxillofacial skeleton before the injury.
To meet these two requirements, the correct fixation site and the correct orientation of the titanium plate must be selected. Usually the fixation site is at the zygomatic-frontal suture, zygomatic arch, infraorbital rim and zygomatic-supramaxillary pillar. At the same time, the direction of the splint must be the same as the stress direction of the pillar, so that the splint is not easily fatigued and the titanium nail is not easily loosened to ensure the continuous and reliable fixation.
5.4 Osteotomy and reconstruction of the orbital wall When the deformity of the orbit-zygomatic fracture heals and is repositioned by osteotomy, different degrees of defects are bound to remain at the fractured end, the size of which is related to the degree of deformity displacement and the magnitude of the osteotomy. At the same time, fracture defects of the orbital wall require simultaneous bone grafting to reconstruct the normal orbital morphology and volume. Rontal et al. concluded that the lateral portion of the orbital floor is a safe area to begin the control of the orbital floor, and can be safely dissected 25 mm posteriorly along the inferior and lateral orbital margins, and 30 mm posteriorly from the superior orbital margin and anterior lacrimal crest without damaging important intraorbital structures. The orbital rim and anterior lacrimal crest can be peeled back 30 mm without damaging important intraorbital structures. In the correction of severe entropion, a 360° dissection of the orbital periosteum around the orbital bone is usually required to allow for adequate anterior displacement of the eye. During dissection, the orbital soft tissues must be fully released from the fractured orbital wall and the soft tissues embedded in the fracture line or in the adjacent sinus cavity must be repositioned while maintaining the integrity of the orbital periosteum to prevent rupture and spillage of intraorbital fat.
In orbital wall bone graft repair, the purpose of repair is to reduce the enlarged orbital cavity, reconstruct the normal orbital volume and normal anatomical shape, regardless of the repair material used. Secondary deformities of the orbital zygomatic fracture, not only fractures of the orbital floor and lateral orbital wall, but also depressed fractures of the internal orbital wall, should be repaired simultaneously. Repair of the orbital floor alone, especially if the bone graft is located anterior to the equator or equator of the eye, can only raise the vertical height of the eye, but it is difficult to move the eye forward. In order to adapt to the anatomical shape of the orbital bone, the implant bone should be trimmed and shaped accordingly, sometimes two or more bone pieces should be overlapped and fixed, trimmed and implanted in the orbit. To prevent displacement of the implanted bone, titanium nails or plates can be used for fixation. Because of the thick dense bone, the autologous cranial outer plate is not easily absorbed after implantation and has good curvature suitable for facial bone reconstruction, plus it is often located in the same operation field with other operations, so it is convenient to take, the amount of bone supply is large, the scar left by taking bone from other parts is avoided, and there are few complications, so it is an ideal material for bone implantation.
5.5 Resuspension of soft tissues to restore the secondary deformity of the orbitozygomatic fracture, due to the fracture of tissue structure and nerve injury during the trauma, resulting in the soft tissue of the zygomatic-cheek area sagging and the displacement of the inner and outer canthus, coupled with the loss of most of the soft tissue support structure due to extensive subperiosteal stripping when the fracture site is exposed Phillips et al. first recognized this problem and emphasized the importance of resuspension of soft tissues. Suspension can be achieved by suturing the soft tissue periosteal composite to the adjacent periosteum, to a small adjacent splint, or by drilling holes through the adjacent bone. The soft tissues of the zygomatic-cheek region can also be elevated and fixed by suturing the cap tendon of the temporoparietal flap to the deep temporal fascia at the temporal line. For older patients with sagging facial soft tissues, in addition to re-suspension and fixation of the affected soft tissues, the soft tissues on the opposite side should be suspended accordingly, otherwise, asymmetry of the soft tissues on both sides of the face may result.