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Underdevelopment of the mandible (microgenia, retrognathia): causes, symptoms, diagnosis, treatment

 
, medical expert
Last reviewed: 07.07.2025
 
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Congenital complete absence of the lower jaw or its individual fragments, as well as a "double" jaw, are extremely rare in practice. Usually, the surgeon encounters either underdevelopment or excessive development of the lower jaw, i.e. microgenia or progenia.

The prevalence and severity of these deformations in different patients varies greatly. It can be total, subtotal, partial; symmetrical (bilateral) and asymmetrical. Therefore, when analyzing the deformation of the lower jaw in our clinic, it is proposed to distinguish its components: microramia (shortening of the jaw branch), microbodia (shortening of the body of the jaw), as well as macroramigo and macrobodia. This allows us to accurately determine the essence of the deformations and purposefully specify the treatment plan.

The diagnostic signs and treatment of these deformations have been studied and described in detail by V. F. Rudko, A. T. Titova, and others. V. F. Rudko points out that when diagnosing underdevelopment of the lower jaw, one must be guided by three main criteria: external manifestations of deformation, the state of the bite, and radiological manifestations.

Congenital unilateral microgenia is usually combined with underdevelopment of the entire half of the face, macrostoma, etc., and with microgenia acquired in early childhood, the primary shortening of the jaw is combined with secondary deformations of adjacent healthy parts of the face.

Symptoms of underdevelopment of the lower jaw (micrognathia, retrognathia)

With combined deformations of the jaws according to the microgenia type, pathological changes in the ENT organs can be observed in the form of a deviated nasal septum, chronic rhinitis, and decreased sense of smell.

The most significant changes in the outer ear are observed in congenital microgenia. Such patients sometimes have a completely absent auricle and external auditory canal, impaired patency of the auditory (Eustachian) tube, adhesive or chronic purulent otitis, significant hearing impairment, and individual indicators of external respiration function (decreased VC and increased MV).

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Treatment of underdevelopment of the lower jaw (micrognathia, retrognathia)

Underdevelopment of the lower jaw can be treated surgically only after the doctor has made sure that orthodontic treatment cannot give the desired result. Therefore, even before hospitalization of the patient, it is necessary to consult him with a highly qualified orthodontist. In this case, it is necessary, firstly, to establish the degree of functional and cosmetic disorders in order to compare it with the degree of the always inevitable surgical risk and the expected effect of the planned surgical intervention. This circumstance must be taken into account in all reconstructive surgeries in the maxillofacial area.

Secondly, it is necessary to decide on the optimal time for the planned intervention. In this regard, the opinions of scientists are quite clear. For example, A. A. Limberg recommends early interventions in case of underdevelopment of the lower jaw.

V. F. Rudko rightly believes that early correction of the jaw shape allows solving the following problems:

  1. creating conditions for its more correct further growth;
  2. prevention of the development of secondary deformation of the upper jaw and the entire facial part of the skull;
  3. elimination of an existing cosmetic defect of the face. If underdevelopment of the lower jaw is combined with ankylosis of the temporomandibular joint, the surgeon must eliminate microgenia and ankylosis at the same time.

There are various methods of surgical treatment of underdevelopment of the lower jaw. In some cases, surgical interventions are performed in the form of moving the entire lower jaw forward by placing a piece of costal cartilage between the posterior edge of the articular head and the anterior edge of the bony protrusion at the external auditory canal; if retrognathia is combined with deforming arthrosis, V. Heiss (1957) placed an articular disc behind the articular head without damaging the disc ligament.

Unfortunately, such a retrocondylar spacer (cartilage, disc) can disrupt the function of the joint and ultimately cause inflammation of the entire joint and its ankylosis. This does not give us grounds to recommend such an intervention. A more promising option may be lengthening the entire alveolar process according to O. Hofer (1942) or H. Kole (1959).

Operations capable of lengthening the body of the lower jaw are often used: according to the method of G. Eiselsperg (1913), M. Grayr (1913), P. Gadd (1910), V. Kasanjian (1924) or other interventions that simultaneously solve two problems: lengthening the body of the lower jaw and eliminating open (or reverse) bite.

Unfortunately, all of them are associated with inevitable dissection of the mucous membrane of the gum, and therefore with infection of the dissected bone tissue, the possibility of developing postoperative osteomyelitis, and an unpredictable outcome. Therefore, they can only be carried out "under the cover" of effective antibacterial prophylaxis before and after surgery.

In this regard, less “threatening” are operations on the branch of the jaw, but carried out through the submandibular approach, i.e. extraorally: osteotomy according to V. Blair (1920), A. A. Limberg (1924), A. Lindemann (1922), G. Pertes (1958), M. Wassmund (1953). G. Perthes, E. Sclossmann (1958), A. I. Evdokimov (1959), A. Smith (1953) (Fig. 277).

Further development of the idea of interventions on the branches of the lower jaw was found in the works of V. Caldvell, W. Amoral (1960), H. Obwegesser (1960). Dal Pont (1961; Fig. 276, 279), as well as in works on this problem in 1961-1996: K. Thoma (1961), K. Chistensen (1962), V. Convers (1963), N. P. Gritsaya, V. A. Sukachev (1977, 1984), A. G. Katz (1981, 1984) and others.

Extraoral access also has significant disadvantages: the possibility of injury to the branches of the facial nerve, branches of the external carotid artery, parenchyma of the parotid salivary gland; leaving a "trace" of the operation - a scar on the skin. Therefore, in recent years, operations on the branches are increasingly carried out through intraoral access, but against the background of studying (before the operation) the sensitivity of the oral microflora to antibiotics and introducing the most suitable of them immediately before and after the operation.

M. M. Soloviev. V. N. Trizubov et al. (1991) in case of mesial bite, when the gap along the sagittal line between the central incisors reaches 10 mm or more, in order to normalize the bite, an intervention is performed simultaneously on both jaws - horizontal osteotomy of the upper jaw and bilateral osteotomy in the area of the branches of the lower jaw with their subsequent counter movement. We believe that this can be done under two absolutely necessary conditions: the absence of indicators of a decrease in the general resistance of the body (background diseases) in the patient and the presence of not only extensive experience in the surgeon, but also all the necessary instruments so that the operation is completed in the shortest possible time, with minimal blood loss of the patient, against the background of highly professional anesthetic support for such a traumatic operation, during which all 12 pairs of cranial nerves will respond. In this case, it is advisable to use the most gentle osteotomy techniques.

In the case of a combination of microgenia with ankylosis of the temporomandibular joint, the branch of the lower jaw is lengthened simultaneously and the articular head is formed using lyophilized homobone or an autograft - the coronoid process, metatarsal bone with the metatarsophalangeal joint, or rib.

In recent years, endoprostheses made of tantalum or titanium, etc., have also been frequently used.

Various defects in the area of the chin alone can be eliminated by the method of H. Obwegesser, V. Convers. D. Smith, using bone taken from the chin area or the body of the jaw, a plastic implant, crushed cartilage, Filatov stem, fat, etc.

If the patient's bite is not disturbed, it is possible to limit oneself to the removal of the chin bone protrusion on the underdeveloped side and the movement of the skin-muscle flap in the desired direction; unfortunately, in patients under 15-16 years of age, such an operation does not achieve the desired result: after 2 years, some flattening of the healthy side is revealed (due to its continued growth and the lag in the development of the opposite side), which then requires correction.

Surgical intervention is often supplemented with orthodontic and orthopedic treatment.

To prevent various errors and complications during operations for underdevelopment of the lower jaw, the following recommendations must be followed.

  1. After a thorough analysis of all the results obtained during the examination of the patient (anamnesis, palpation, laboratory tests, panoramic radiography, tomography, etc.), it is necessary to draw up a well-founded and clearly formulated treatment plan, taking into account the age and gender of the patient, his general condition, the degree of deformation of the lower jaw and adjacent areas of the face.
  2. If the patient is over 15 years old, and the shortening of the lower jaw does not exceed 1 cm, in the absence of protrusion of the upper jaw and preservation of the bite, contour plastic surgery should be limited.
  3. If the lower jaw is shortened by more than 1 cm, which causes external disfigurement of the face and malocclusion, it is necessary to correct the position of the lower jaw (at any age), and then perform contour plastic surgery and orthodontic correction of the bite.
  4. Lengthening of the jaw body using bone grafting should be performed after the completion of the main period of formation of the facial part of the skull, i.e. in children over 12-13 years old.
  5. If lengthening of the lower jaw is necessary, the following questions must be answered:
    • Which part of the jaw needs to be lengthened?
    • Is it enough to perform a plastic osteotomy for this or will a bone transplant be necessary?
    • What will be the source of the transplant (auto-, xeno-, allograft)?
    • Will there be a connection between the wound and the oral cavity during the operation? Will there be a need for antibacterial therapy?
    • What is the microflora of the oral cavity and to which antibiotics is it most sensitive?
    • How will the mandible and transplant be immobilized after surgery?
    • How will the patient be fed and what diet will he be on (sippy cup, Nesmeyanov spoon, etc.)?
    • What type of pain relief is optimal for this patient?
    • Who exactly will provide individual care and feeding for the patient in the first days after surgery?

Horizontal osteotomy of the jaw branch

It is better to perform horizontal osteotomy of the jaw branch through a vertical intraoral incision in front of it. The fragments of the branch can be fastened with a polyamide thread or chromic catgut. In recent years, surgeons have almost never used vertical osteotomy of the jaw branch.

Step osteotomy of the body of the jaw

Step osteotomy of the body of the jaw can be performed through an intraoral approach, avoiding external incisions, possible injury to the marginal branch of the mandible of the facial nerve and noticeable postoperative scarring of the skin.

This is a rather traumatic and complex operation, so it must be performed by an experienced surgeon.

Vertical osteotomy of the body of the jaw

Vertical osteotomy of the jaw body (with subsequent osteoplasty) is best performed immediately behind the dental arch, where the mucous membrane covering the retromolar region and the anterior edge of the branch is sufficiently mobile and also easily separated. This avoids communication of the wound with the oral cavity. To strengthen the bone sapling, chromium-plated (long-lasting) catgut No. 6-8 can be used, and to fix the separated fragments, dental wire splints with hooks for intermaxillary fastening or titanium mini-plates can be used.

Vertical L-shaped osteotomy of the ramus and body of the jaw

The vertical L-shaped osteotomy begins in the area of the anterior section of the jaw branch at the level of the mandibular foramen, then goes down along the projection of the mandibular canal and dissects the underlying section of the branch and the angle of the jaw into anterior and posterior fragments, and in the case of intervention on the body of the jaw - into upper and lower; at the level of the second premolar or first molar, the dissection line is turned downwards and brought to the lower edge of the jaw. A similar intervention is performed on the opposite side. Then the chin is pulled forward to the required level and, having drilled holes above and below the cut line of the body of the jaw, its fragments are connected with steel wire, polyamide thread or long-term non-absorbable catgut.

Arthroplasty using double or triple de-epidermized skin flap according to Yu. I. Vernadsky

Arthroplasty using a double or triple de-epidermized skin flap according to Yu. I. Vernadsky is indicated only in cases of relatively mild (up to 5 mm) underdevelopment of the jaw due to ankylosis.

Interosseous pad from Filatov stem according to A. A. Limberg

The interosseous pad made of Filatov's stem according to A. A. Limberg requires multi-stage surgical treatment, so it is better not to use it, especially in children and weakened adults.

If a more significant forward advancement of the jaw branch is required, it is better to use a bone or bone-cartilage graft instead of soft tissue pads.

The cosmetic and functional effectiveness of operations (for microgenia and ankylosis) using bone plastic transplantation is significantly higher even in the long term.

Restoration of the jaw branch by free transplantation of an autologous rib with the creation of a joint in the area of the squama of the temporal bone according to A. T. Titova

The operation is indicated in cases of microgenia caused by branchial arch syndrome II or osteomyelitic destruction of the jaw branch in childhood.

After isolating the remaining part of the jaw branch from the scar tissue (if any), the coronoid process is crossed horizontally, the branch is lowered and the jaw is moved forward until the chin is in the correct position.

A pocket with a blind bottom is created using soft tissues in the area of the coronoid process. In order to create a bed for placing the autorib graft (with its cartilaginous part facing up), the soft tissues in the area of the subcoronoid fossa of the temporal bone between the zygomatic process and the squama of the temporal bone are stratified.

The bone end of the sapling is placed on the angle of the jaw, previously deprived of the cortical bone plate, and sutured. The wound is sutured layer by layer, then a bone clamp is applied to stretch the jaw for 10-12 days (if there is a spacer between the teeth) and an M. M. Vankevich splint is made.

In this form of microgenia, arthroplasty according to V.S. Yovchev can also be used.

After osteoplasty for microgenia, the patient must be referred to an orthodontist or orthopedist to correct the bite.

Outcomes and complications of treatment of underdevelopment of the lower jaw (microgenia, retrognathia)

According to available data, engraftment after contour plastic surgery with crushed autocartilage is observed in 98.4% of patients, and restoration of natural facial contours or maximum cosmetic effect is achieved in 80.5% of patients.

When autodermal subcutaneous transplants and xenogeneic protein membranes are implanted, the cosmetic effect in the immediate period (1-2 years) after the operation is satisfactory, but gradually decreases due to the resorption of the transplant and its inadequate replacement with connective tissue.

After surgical jaw lengthening, complications occur in an average of 20% of patients in the form of sequestration of the ends of the lower jaw segments, necrosis of the entire or part of the seedling. The cause of these complications is infection of the seedling bed due to perforation of the oral mucosa when exposing the ends of the bone defect and moving it to the correct position.

Prevention of complications of underdevelopment of the lower jaw (micrognathia, retrognathia)

Prevention of inflammatory complications consists of targeted antibacterial therapy, starting from the first hours after surgery.

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