Introduction

Based on the many authors data, and on our own clinical experience, we can say that one of the most pressing problems of modern maxillofacial surgery is the problem of treating patients with the mandible fractures and post-traumatic deformities [1, 2]. Moreover, according to statistics, there is both an increase in the number of such patients and a bad-prognosis of the injuries [3, 4, 5].

There are currently many systems and methods for fixing mandible fragments both conservative and surgical in maxillofacial surgery. All of them have advantages and disadvantages, certain indications and contraindications. At the same time, in recent years, there has been a tendency to reduce using the conservative methods as independent fixation methods. In fact, now we can talk about using the conservative methods mainly as an accessorial fixation [6, 7, 8].

The principle of functioning of modern systems for bone fragments fixation is based on the unified theory of osteosynthesis, developed in 1958 by a group of Swiss scientists (M. Muller), who created the Association of Osteosynthesis and the Association for the Study of Internal Fixation (AO/ASIF International). The guidelines developed by this group describe the principles to be followed to ensure the mandible shape and functionality optimal restoration during treatment (Spissl B., 1976, Prein J., Kellman R., 1987, Yaremchuk M. J., 1992). These principles can be summarized in 4 points:

1) the bone fragments anatomical reposition;

2) the bone fragments functionally stable fixation;

3) the blood supply bone fragments saving by using atraumatic techniques;

4) early, active and painless mobilization.

The most important factor that ensures the success of patients with mandibular fractures treatment is fragments adequate immobilization, which is carried out by fixing bone fragments using various devices and techniques. In accordance with modern opinion, to ensure the most complete functional and stable mandible fragments immobilization — it is preferable using internal fixation methods. In this case, the stabilizing devices are fixed directly on the bone fragments with the creation of a fixed implant-bone complex [9, 10]. Methods of internal fixation include osteosynthesis with metal spines, osteosynthesis with a wire suture, and osteosynthesis using bone plates.

The main disadvantage of the methods of osteosynthesis using as a stitch and as a spine is the difficulty to achieve stable fragments fixation by these methods. At the same time, it is known that such post-traumatic complications as osteomyelitis and the false joints formation are a direct consequence of the fragments instability [11, 12]. The combination of the bone stitch and the Kirschner spines provides a somewhat stronger fragments fixation, but does not exclude the main bone stitch disadvantage — the larger fragment sinking-down downwards and the appearance of a false triangular defect [13].

Studies of recent decades suggest that for the most ensured achievement of the bone fragments stability and as for the preservation of blood flow in the fracture area, as for the optimization of the rehabilitation period, it is preferable using bone plates as osteofixers [14, 15, 9].

Materials and methods

We have proposed individual bone plates that ensure the mandible fragments fixation without offence the basic principles of stability and additional injury to the soft parotid tissues. The plates shape allows to avoid their modeling during surgery by repeatedly bending in different planes. In addition to the fact that such a modeling process significantly increases labor costs and operation time, it contributes to a noticeable deterioration in the plate strength properties and the development of fatigue changes in it [10]. A consequence of plate technical characteristics degenerative transformations may be the loss of the fragments fixation stability and the development of a chronic osteomyelitic process in the fracture zone [15, 16].

To substantiate the design of the bone plates, the final element method with followed by solid-state modeling was used [2].

In particular, on the conducted model basis we proposed a bone plate for fixing fragments in the mandible angle fractures of the by intraoral access. In the patients with mandible body other part fractures treatment, we consider it appropriate to use individually made X-shaped plates as bone fixing structures. The individual plates modeling, focused on the surface relief of the fixed bone fragments. It allows to exclude the plates correction directly during surgery. Intraoral access seems preferable due to less trauma and greater aesthetics due to the absence of incisions on the face. With intraoral access, there is no intersection of large blood vessels, there is no need for exfoliation of a significant array of soft tissues, and the masticatory muscles are less injured. In this regard, the recovery of tissues in the postoperative period is easier, the inflammatory reaction is less expressed.

In the advertised plate (Fig. 1), three parts could be conditionally distinguished: two fixing and an intermediate one. The shorter fixing part (about 15 mm) is attached in the retromolar region, on the distal fragment [B]. Its fixation is carried out by means of two intraosseous screws, for which there are holes on the plate [D] with a diameter of 2 mm. The length of the second fixing part [C] depends on the individual anatomical features and is located on the outer oblique line.

Fig. 1. Individual extracorporeal plate for fixation of fragments in the area of the mandibular angle by intraoral access.

a — intermediate part; b — distal fixing part; c — medial fixing part; d — hole for fixing intraosseous screws.

The length of the intermediate part [A] is a variable value, as is the angle at which the fixing parts are located relative to each other.

The technique of the fragments fixing is aprescribed bellow. After antiseptic preparation and achieving adequate anesthesia, an incision is made along the inner slope of the pterygoid-mandibular fold and further to the last molar, then along the distal surface of its crown and anteriorly along the buccal surface to the level of the next interdental papilla. Then the mandible mucous membrane, submucosal layer and periosteum in the vertical direction to the transitional fold are dissected. Thus, the stepwise muco-periosteal flap is cut out.

The flap is peeled off, skeletonizing the mandible fragments with the help of a rasp. The fragments are reposed, focusing on the congruence of the wound surfaces of the fragments and the anatomical comparison of the dentition of the maxilla and mandible. To ensure the correct ratio of the dentition, we recommend the use of orthodontic screws.

Then make sure that the modeling of the bone plate is correct, checking the density of its fit to the bone tissue and the accuracy of matching the bone relief, and fix the plate with intraosseous screws. To do this, channels for screws are formed in series perpendicular to the plane of the cortical plate using a drill of the appropriate diameter, in accordance with the generally accepted method. The cutting tool is operated under continuous cooling with antiseptic solutions to avoid bone burns.

Perform fixation of the bone plate with intraosseous screws in accordance with the general principles of bone plates fixation, controlling the bone fragments congruence and the comparison of tooth rows (Fig. 2). The bite after the end of fixation should be established without effort, by natural jaw movement.

Fig. 2. Fracture of the lower mandibular angle on the right: the fragments were fixed with an individual extraosseous plate and intraosseous Stryker screws; the plate tightly adjoins the bone.

a — individual extra-bone plate; b — fixing screws; c — fracture gap.

Then the muco-periosteal flap is placed in place and fixed with a non-absorbable thread. Many authors recommend leaving a rubber graduate in the wound for 2-3 days to prevent the occurrence of a hematoma. We prefer not to do this, given the low trauma of the intervention and the moderation of bleeding during intraoral access, as well as the risk of postoperative infection of the wound with oral microflora. To prevent the occurrence of severe hematoma, we recommend the use of cryotherapy in the early postoperative period.

Until now, the doctor's tactics in relation to the tooth located in the fracture gap are still controversial. Many authors believe that the mandatory removal of such a tooth is necessary to prevent the development of an inflammatory process in the fracture area, slow consolidation of fragments and ensure adequate reposition of bone fragments. We consider it mandatory to remove the tooth from the fracture gap in the case of significant destruction of its crown part by the carious process, due to inflammatory phenomena in the area of the root tips, with an incorrect position of the tooth in the dental arch. At the same time, an intact tooth that occupies the correct position and has an antagonist, despite the fact that its periodontal fissure contacts the fracture fissure only tangentially, can, in our opinion, be preserved, provided that adequate endodontic treatment and canal filling are carried out.

On the Figure 3 the mandible radiograph in the lateral projection of patient K., 20 years old, is shown. The fracture fissure is visible in the mandible angle area, passing through the periodontal fissure of the tooth 4.8. It is visible that both roots of the tooth 4.8 are located in the fracture fissure. There is no contact with the tooth 1.8 due to the incorrect position of the latter in the dental arch. On palpation, the tooth is mobile. Such a tooth, in our opinion, is subject to removal from the fracture fissure.

Fig. 3. An open fracture of the lower jaw angle on the right in patient K., 20 years old.

a — radiograph of the lower jaw in profile on the right: the fracture line passes through the periodontal gap of the 4.8 tooth (shown by the arrow); b — general radiograph of the bones of the facial skeleton in the postoperative period, direct projection.

A — extra-bone plate; B — fragments of the lower jaw.

During the surgical intervention under general anesthesia, the tooth 4.8 was removed. According to the procedure described above, an operation of osteosynthesis was performed with the fixation of bone fragments by means of an individual bone plate (Fig. 4). The bite was restored. The postoperative period was uneventful. The stitches were removed on the tenth day after surgery.

Fig. 4. Scheme of the fracture in the area of the body of the lower jaw on the right.

1 — fracture line, 2 — diagram of the incision on the eve of the oral cavity according to the authors’ method.

If it is necessary to remove a tooth from the fracture fissure, the doctor often faces the task of preventing atrophy of the mandible alveolar part to ensure functional dental prosthetics in the postoperative period. To solve this problem, we proposed to fix the mandible fragments with simultaneous plasty of the bone defect that occurred after the tooth was removed from the fracture fissure.

We suggest using a trapezoidal incision, rather than a linear one, to access the fracture fissure located within the mandible boundaries, when it becomes necessary to remove a tooth fracture from the fissure that is not subject to treatment. The use of such an incision ensures the formation of a muco-periosteal flap, the base facing the transition fold, wide access to the fragments to be fixed, and visual control of the bone defect that occurs after tooth extraction. Incisions are made from the interdental papillae on both sides of the tooth to be removed at obtuse angles and extend slightly above the transition fold by 1.5 cm in both directions (Fig. 5).

After skeletonizing the fragments, the tooth is removed from the fracture gap, the pathologically altered tissues are removed from the well, the fracture gap is revised, removing small bone fragments.

According to the generally accepted method, the fragments are repositioned, focusing on the congruence of the fragments and the anatomical comparison of the dentition. To hold the bite, use orthodontic screws with elastic traction, or wire ligatures. After making sure that the bite is adequately restored, the fragments are fixed with individual bone plates and intraosseous screws. After achieving the stability of the fragments, the bone defects formed as a result of the removal of the tooth and bone fragments are filled with blocks of bone-plastic material soaked in blood.

The previously formed muco-periosteal flap is mobilized by dissecting the periosteum at its base and moving it, completely blocking the hole of the removed tooth, thus ensuring isolation of the bone wound from the infected contents of the oral cavity. The flap is fixed with a non-absorbable suture material.

Conclusion

Our observations show that by the sparing surgical techniques (intraoral access) using in combination with the individual bone plates and simultaneous bone grafting usage gives the opportunity to significantly optimize the patient's rehabilitation process, reduce the period of disability, reduce the risk of various complications and create conditions for subsequent restoration of the dentition with dental implants.

The participation of the authors:

Concept and design of the study — A.L. Savelyev, M.G. Samutkina

Data collection and processing — A.L. Savelyev, M.G. Samutkina

Text writing — A.L. Savelyev, M.G. Samutkina

Editing — A.L. Savelyev

The authors declare no conflicts of interest.