A representative method for treating fractures in the maxillofacial region is internal fixation using a monocortical plate. This method was first devised by Michelet et al. [1] and modified and generalized by Champy et al. [2]. Materials used for internal fixation require adequate resistance, sufficient ductility, and biocompatibility. Titanium plates are the most commonly used materials for internal fixation because they can be properly deformed according to their anatomical shape and are sufficiently hard to resist local forces. In addition, the titanium screw used together is initially maintained by the mechanical bonding force with the bone; over time, a direct connection between the screw and bone is added, which is beneficial for bone healing. However, the need to remove these miniplates remains controversial. Although some surgeons say that plate removal is necessary after a certain period of time has elapsed after surgery, others believe that metal plate removal is unnecessary if there are no clinical symptoms [3].

It is rare for a fracture to recur in the same area of the maxillofacial region, and related studies are lacking. Previous studies have reported that most refractures in the maxillofacial region occur on the side opposite to the existing surgical site [4-6]. In addition, there are no reports of cases where refracture occurred in the same area without removing the metal plate after fixation with a titanium plate or screws in the case of a primary fracture.

Herein, we report the cases where refracture occurred at the same site owing to a similar injury mechanism after intraosseous fixation with a titanium plate and screws for zygomaticomaxillary fractures.

Two patients whose records were used in this study provided signed informed consent.

Case 1

A 22-year-old male patient visited the emergency room of Gachon University Gil Hospital with an injury to the left facial area caused by an assault by another person (Table 1). Facial bone computed tomography (CT) revealed that the left zygomaticomaxillary complex was fractured and displaced posteromedially (Fig. 1A, B).

Fig. 1. Pre/postoperative 3D reconstruction CT images of Case 1 (initial fracture). (A, B) Preoperative 3D CT showing a depressed left zygomaxillary complex with multiple bony segments. (C, D) Postoperative 3D CT showing the reduced state of the fractured bone with improved alignment. CT, computed tomography; 3D, three-dimensional.

Nine days after the injury, an anterior incision was made from the left canine to the first molar under general anesthesia and the fracture site was confirmed by dissection and elevation of the periosteum. The fracture fragment was reduced anterolaterally using a zygoma elevator, internal fixation was performed using a titanium miniplate, and periosteum and mucosal suturing were performed. Postoperatively, the fracture site was symmetrically well restored, and no complications were observed (Fig. 1C, D).

Fifteen months after the operation, the patient revisited the emergency room of our hospital with the same injury and was diagnosed with refracture of the left zygomaticomaxillary complex (Fig. 2A, B). The refracture site was accompanied by deformation of the metal plate (Fig. 3), and there was no comminuted fracture around the metal plate or screw, and a simple fracture similar to the previous injury appeared. As a result of overlapping the CT images after the first and second fracture operations, displacement of the bone fragment due to the fracture was observed, and the existing metal plate did not appear to have a special effect on the fracture pattern (Fig. 4). Under general anesthesia, an incision was made along the scar at the existing surgical site, and the metal plate was removed and refixed (Fig. 2C, D). No complications occurred postoperatively.

Fig. 2. Pre/postoperative 3D reconstruction CT images of Case 1 (refracture). (A, B) Preoperative 3D CT showing left zygomaxillary complex fracture with deformation of the previous titanium plate. (C, D) Postoperative 3D CT showing the reduced state of the fractured bone. CT, computed tomography; 3D, three-dimensional.

Fig. 3. Intraoperative photos of Case 1. (A) Intraoperative photograph showing the normal shape of the titanium plate immediately after the reduction and fixation of the initial fracture. (B) Intraoperative photograph showing L-plate deformation after refracture.

Fig. 4. Superimposition of the postoperative initial fracture and preoperative refracture showing displacement of fracture fragments. (A) Axial view. (B) Coronal view.

Case 2

A 31-year-old male patient was admitted to the emergency room of Gachon University Gil Hospital because of a traumatic injury to the right side of his face sustained during a traffic accident (Table 1). A fracture of the right zygomaticomaxillary complex was confirmed on facial bone CT (Fig. 5A, B). One day after the injury, the fracture site was reduced under general anesthesia, and internal fixation was performed using a titanium plate. After surgery, the fracture site was symmetrically restored, and no complications were observed (Fig. 5C, D). The metal plate at the surgical site was not removed, and 10 years after the operation, the right facial part was injured in a traffic accident while driving a motorcycle and was diagnosed as a refracture of the right zygomaticomaxillary complex (Fig. 6A, B). The right zygomatic arch was refractured, and a typical fracture pattern was observed in the plate at the zygomaticomaxillary buttress area with deformation and posteromedial displacement of the bone fragment. The frontozygomatic suture area was maintained without the deformation of the existing metal plate or displacement of the fracture site. After removing the existing metal plate using an intraoral approach, the bone fragment was reduced, and fixation was performed using a metal plate (Fig. 6C, D). No special treatments were applied to the frontozygomatic suturing area. No postoperative complications were observed.

Fig. 5. Pre/postoperative 3D reconstruction CT images of Case 2. (A, B) Preoperative 3D CT showing zygomaxillary complex fracture. (C, D) Postoperative 3D CT showing the reduced state of the fractured bone. CT, computed tomography; 3D, three-dimensional.

Fig. 6. Pre/postoperative 3D reconstruction CT images of Case 2 (refracture). (A, B) Preoperative 3D CT showing a zygomaxillary complex fracture with deformation of the previous plate. (C, D) Postoperative 3D CT showing reduction state of the fractured bone. CT, computed tomography; 3D, three-dimensional.

The fracture site undergoes inflammatory, reparative, and bone-remodeling phases during healing. The callus is formed and its strength increases during the reparative phase [7]. When the peripheral callus forms a bridge at the fracture site, movement between the fracture fragments is significantly reduced, resulting in cortical healing. Afterwards, the callus is remodeled and completely removed. A fractured area represents a continuous increase in the strength and stiffness [8]. Eventually, it has the same strength as before the fracture. Refracture means that an external force is applied to the part where the fracture occurred, causing the fracture to occur again. Goracy and Stratigos [9] classified refractures into true and parafocal refractures according to the fracture site. True refracture was defined as a fracture occurring at the site where the original fracture occurred and a fracture occurring again at the site where the callus was formed or where the bone was improperly formed. Parafocal refracture was defined as a fracture occurring around the previous fracture site and not around the callus formation site. When a fracture occurs, a callus is formed at the fracture site and heals as it matures; however, the surrounding bone is mechanically and structurally altered, reducing its strength. The area where the callus is formed has greater strength than the surrounding bone over time. When trauma is applied to the existing fracture site, the fracture appears in the surrounding bone with reduced strength, not in the area where the callus is formed, and is observed parallel to the existing fracture line [9].

The degree of healing of fractures can be confirmed by radiographs. However, in the radiographs, there is difficulty in confirming the exact state due to artifacts caused by metal plates or screws. Therefore, we could judge the degree of healing of the fracture site with the area, which is not internally fixed with metal plates or screws, posterior wall of maxillary sinus.

The healing period of a fracture varies depending on the severity and characteristics of the individual patient. Kawai et al. [10] evaluated the degree of fracture fusion over time using follow-up radiography. It was reported that patients aged <18 years showed significant changes within 1–2 months after fracture and 2–3 months in older adult patients [10]. Therefore, a significant union of fractures can occur approximately 3 months after surgery.

The cases in this study were refractures that occurred 15 and 119 months after surgery. The location of the refracture was the same; however, the location of the fracture line did not coincide exactly with that of the first fracture. This is thought to be because the maxillary sinus is adjacent to the zygomaticomaxillary complex; thus, the thickness of the bone is anatomically thin and composed of a relatively complex shape.

The strength of the miniplate inserted into the jawbone depends on the thickness and number of plates. In laboratory studies, the yield strength of miniplates has been reported to be approximately 100 N in the vertical direction and 230–250 N in the horizontal direction [11,12]. This is sufficient strength to resist masseter muscle pulling in cases of unilateral maxillary-cheek bone fracture. However, if an additional external force is applied to the miniplate insertion site, deformation or fracture of the metal plate can occur. In this case, an additional external force was applied to the metal plate owing to an assault by another person and a traffic accident involving a driver, and refracture and deformation of the metal plate occurred. No additional complications were observed at the screw insertion site. Although both patients had refractures of the same cause, the displacement of the fracture fragment was smaller in the second fracture than that in the first. This reduced the effect on the actual fracture because the plate absorbed some of the external force and was deformed.

In addition, in all cases, refracture occurred after the initial fracture site was sufficiently healed, and it is predicted that the bonding force between the titanium screw and bone was formed, which is thought to have been a factor in preventing additional fractures at the screw site.

The removal of metal plates remains controversial. The cause of metal plate removal was the patient’s request, which accounted for the largest percentage, followed by infection and pain [13]. Through these cases, it is thought that if an external force is applied to the same area in the presence of a metal plate, it will reduce the severity of refracture; thus, removing the metal plate without clinical symptoms is considered unnecessary.

In this study, we confirmed that fractures accompanied by the deformation of the metal plate occurred when refracture occurred in the same area without removal after fixation using a metal plate in zygomaticomaxillary complex fracture. Therefore, additional research is necessary to determine the fracture pattern when a force strong enough to cause the fracture of a metal plate is applied.

None.

The authors declare that they have no competing interests.