Macrogenia

Macrogeny is one of the most severe facial deformations, accounting for 1.5 to 4.28% of all bite anomalies.

[ 1 ]

Symptoms of macrogenia

Depending on the degree of expression of the sagittal, vertical and transverse discrepancy of the dental arches with excessive symmetrical bilateral development of the lower jaw (progenia), V. A. Bogatsky distinguishes three degrees of this deformation:

• I degree: the bite is not disjointed or is disjointed only slightly - up to 2 mm: the mandibular angles are turned up to 135° (instead of 127° in the norm); the sagittal relationship between the sixth teeth of the upper and lower jaws is disturbed by no more than 5 mm, only individual teeth are abnormally located; the protrusion of the lower third of the face and the enlargement of the chin are outwardly noticeable.
• II degree: sagittal gap between incisors up to 1 cm; sagittal disturbance of the relationship between antagonist canines and antagonist sixth teeth reaches 1 cm; mandibular angles are turned up to 138°; individual teeth or groups of teeth are abnormally located; in some cases, narrowing of the upper jaw, open or deep bite of 1, 2 or 3 degrees is observed. Loss of chewing efficiency ranges from 68% (in the absence of a combination of progenia with open bite) to 76% (in its combination with open bite).
• Grade III: sagittal gap in the frontal area is more than 1 cm; sagittal disturbance of the relationship between the first antagonist molars reaches 1.1-1.8 cm; mandibular angles are rotated up to 145°; teeth are located abnormally; open or deep (reverse) bite is noted; loss of chewing efficiency is 72.5% in combination with open bite, and 87.5% in combination with deep bite.

Unlike other classifications of progenia, V. A. Bogatsky’s classification reflects sagittal, transverse and vertical discrepancies of dental arches, which is very important to take into account when planning an operation.

In combined deformations of the jaws according to the progenia type, a curvature of the nasal septum, chronic rhinitis, and deterioration of the patency of the nasal cavity for air flow are observed.

Changes in the external ear consist mainly of deformation of the external auditory canal (caused by excessive development of the head of the lower jaw); obstruction of the auditory tube (due to frequent rhinitis and diseases of the nasal part of the pharynx); adhesive and chronic purulent otitis, and disturbances in sound conduction (within 10-15 dB) are also noted.

Spirometry studies by I. M. Migovich (1998) have proven that most patients with progenia with open bite have impaired pulmonary ventilation, which obliges the surgeon to carry out a thorough examination and sanitation of the patients' respiratory tract before surgery.

A special local examination should begin with the production of a plaster facial mask, photographing the patient in three projections, taking impressions (with algelast or stomalgin) and producing two or three pairs of jaw and dental models from them.

Models are necessary to specify the size and shape of the dental arches, their relationship, and the nature of secondary deformations of the upper jaw. The models are used to develop a plan for the upcoming operation, as well as a method for the most rigid fixation of jaw fragments after osteotomy. One of the pairs of models is fixed in a wire articulator to "maneuver" the sawn jaw fragments in it, simulating their location after osteotomy. To do this, a section corresponding to the upcoming osteoectomy is sawed out of the model.

Teleradiography allows to obtain the most complete picture of the nature of the anomaly and the localization of the most deformed areas of the facial bones, as well as to determine which part of the bone (lower, upper jaw) is causing the deformation and which fragment needs to be removed or moved to obtain a normal profile and correct occlusion. In addition, this radiography method documents the profile relationship of soft tissues and facial bones, which is also important for subsequent evaluation of the operation result.

Treatment of macrogenia

Surgical treatment of mandibular prognathism is a complex task, since there are no sufficiently clear standard criteria that could be used to select a treatment method. Therefore, only thoughtful preoperative preparation of the patient ensures a sufficient effect of the operation.

Surgeons' opinions differ somewhat regarding age indications for surgical intervention in progenia. Some believe it can be performed at any age; others believe that operations are possible only starting from the age of 13.

We believe that if in case of significant underdevelopment of the lower jaw, surgical intervention should be performed as early as possible, then in case of moderately expressed progenia (grade I), the operation can be postponed until 13-15 years, i.e. until the growth of facial bones is complete. The less pronounced the degree of progenia deformation, the later the operation can be performed. In case of progenia grades II-III, the operation should be performed before the specified age.

Moderately expressed progenia (grade I) usually does not entail significant deformation of the upper jaw. Therefore, in such cases there is no need to rush to early surgery.

Outcome of surgical treatment of progenia

When assessing the outcome of treatment, it is necessary to take into account not only the ratio of the jaws, but also the height of the lower third of the face, the shape of the angles of the lower jaw, as well as the chin and middle parts of the face.

The desired facial proportions can only be achieved if, in addition to the main operation (on the body and branch of the jaw), the patient also undergoes additional corrective operations (contour plastic surgery, resection of the body of the lower jaw in the area of the chin or corners of the jaw, etc.).

Recurrence of progenia may occur as a result of insufficiently complete contact between the jaw fragments, a change in the direction of traction of the masticatory muscles, or as a result of macroglossia.

According to available data, insufficient adaptation of the bone surfaces of the jaw branch can lead to an open bite and be the cause of an early relapse - immediately after the removal of the intermaxillary fixation.

Due to the fragility of the young bone callus, the pull of the masticatory muscles causes the bone fragments to shift. This is more often observed after operations performed on the branch “blindly” and in the horizontal direction; in particular, after the Kosteeka operation, the upper fragment may shift forward and upward (under the action of the temporal muscle) and lose contact with the lower fragment.

Since macroglossia contributes to the occurrence of recurrent prognathia, open bite or pseudoarthrosis at the site of osteotomy of the body of the jaw, some authors recommend reducing the tongue (resecting part of it simultaneously with the implementation of osteoectomy in the area of the body of the jaw).

The insufficient effectiveness of the operation in cosmetic terms is due to the fact that after it, an excess amount of tissue is created on the face, gathering in an "accordion" as a result of the reduction of the lower jaw. This is especially pronounced in obese elderly patients.

Damage to one of the branches of the facial nerve may occur if the surgeon does not pierce the skin and underlying tissue with a scalpel before inserting the Kerger needle and does not insert a narrow metal instrument (spatula) into the resulting wound channel to protect the branch of the facial nerve. Unfortunately, this complication is often irreversible, despite the physiotherapy and medication used. In the event of persistent paralysis of a particular group of facial muscles, an appropriate corrective operation must be performed.

To prevent this complication, it is advisable to perform operations through intraoral access, especially when performing interventions on the proximal parts of the jaw.

When performing operations through extraoral access, it should be remembered that the mandibular angle in progenia is always somewhat higher than normal, and therefore the skin incision in the submandibular region should also be located somewhat lower than in the case of a normal phlegmon opening or other operations. Damage to the parotid salivary gland with subsequent formation of a salivary fistula on one or both sides after the Kosteeka operation occurs, according to the literature, in approximately 18% of patients. However, in each case, the fistulas disappear on their own.