Fractures of the atrophic mandibule

These mandibles have a reduced cross section, with smaller contact areas (limited interfragmentary stability) of the fractured ends and poorly vascularized, dense, and sclerotic bone. These characteristics prolong healing times, so complications can be expected. A high rate (20%) of nonunion was reported.

Because the relation between the height of the mandible and the incidence of complications in fracture healing is obvious, there is a need for such a classification with special respect to fracture treatment. The existing classifications of mandibular atrophy were developed mainly for prosthodontics or implantology and are not related to the special concerns of fracture treatment.

Traditional treatment

1. Closed Reduction and Fixation by Intraoral Appliances
   Fixation by means of Gunning splints or the patient’s dentures is indicated for nondisplaced or only minimally displaced fractures. Usually the dentures do not fit because of edema and hematoma in the floor of the mouth and the vestibule. Therefore the lower dentures must be trimmed and relined with an elastic dental compound to avoid ulceration of the mucosa. If the dentures are missing, impressions are taken and a Gunning splint consisting of two independent acrylic base plates and bite blocks is constructed. An external headgear supports the dentures or the Gunning splint. The jaw should be immobilized for 4 to 8 weeks. The splints allow stagnation of food debris and do not allow adequate oral hygiene. This method does not provide full immobilization.

2. Direct Circumferential Wiring and Fixation of the Lower Part of a Gunning Splint by Means of Circummandibular Wires

3. Interosseous Wiring

4. Extraoral Pin Fixation

5. Primary Bone Grafting

Fixation by palte osteosynthesis

Bilateral fractures of such extremely atrophied mandibles are still the most problematic. The goals of the new treatment principle were to avoid the well-known disadvantages of existing methods (such as, interosseous wiring and circumferential wiring, which were associated with high complication rates) and to avoid long-term immobilization of the jaws by means of complicated and uncomfortable intra-extraoral prosthodontic appliances.

Fractures of the edentulous atrophic mandible were the original indications for compression plating when this treatment principle was introduced to maxillofacial surgery by Luhr on October 30, 1967. Autogenous cancellous or corticocancellous iliac bone usually was used, together with compression plating. Because of donor site morbidity in relation to iliac bone graft one may choose a rib graft. Primary rib grafting can be chosen for treating problematic cases of fracture of the extremely atrophic mandible. However, one must realize that autogenous rib grafting in the older patient, who frequently has cardiopulmonary impairment, is a major surgical intervention with the potential risk of general complications. Patients for this kind of treatment therefore must be selected carefully.

Noncompression plating is used more commonly now. The type of plate used varies in different centers. Miniplate osteosynthesis has been used, with a 3.9% reoperation rate.

Complications and how to avoid them

The most frequent complication in the treatment of fractures of the edentulous atrophic mandible is nonunion.

(稳定固定、压力承载、保护骨膜)

• Because stability is the most important factor in fracture healing, particularly in fractures of the edentulous atrophic mandible, axial load bearing plating is preferred in this problem area as the simplest way to achieve the required rigidity with minimal inconvenience to the patient.
• Place the plate from lateral along the inferior border to avoid injury to the mandibular nerve. Avoid the placement of plates from inferior on the lower border of the mandible, however, because the strong pull of the suprahyoid muscles can result in an “out of plane” bending of the plate with a lack of rigidity.
• Stripping of the periosteum from the bone should be avoided, and supraperiosteal placement of plates and screws is recommended, especially when a locking plate system is used, which prevents the plate to be strongly pushed to the underlining surface.

Bilateral fractures of the atrophic mandibular body

Usually a gross displacement of the chinbearing segment downward and backward is found because of the pull of the suprahyoid musculature, particularly when there are bilateral fractures of the horizontal rami. Simple manual reduction is rarely possible, and reduction usually requires significant traction on the chin area by a sharp single hook inserted transcutaneously into the lingual side of the chin. These remarkable forces required for fracture reduction emphasize the amount of mechanical stress the osteosynthesis
must later withstand.

Frequently, the patient’s lower dentures are broken or missing or no longer fit because of the massive edema and hematoma of the floor of the mouth. Therefore dentures rarely can be used as a guide for proper reduction.

Because any reference to the individual curvature of the mandibular arch is missing, there is the danger of incorrect plate contouring to the bone if only one of the fractures is plated first. Note that the fracture line at the inner surface of the mandible is not visualized. When the screws of this plate (with an incorrect contour to the bone) are tightened, this may result in severe displacement of the fracture end at the opposite fracture site. To avoid this, we strongly recommend initial exposure of all the fractures. The fractures then are reduced and the plates contoured to the bone surfaces of both fractures. The two screws near the fracture line should be inserted only partially in each of the plates. When they are tightened finally, observe the opposite fracture line. If a tendency to displacement of the other fragments is seen, remove the first plate and recontour it before placing it again. Then tighten the screws of both sides of the fracture alternately.

Treatment of nonunion in fracture of the atrophic mandibule

Nonunion is a common complication, particularly in a Class III atrophic mandible. Nonunion is even worse when the nonunion is bilateral.

• Evaluation of treatment outcomes should be based on measurementsof the height of the mandible at the fracture site and a fracture-related classification of the degree of atrophy. In a large series of such fractures, compression plating had a 97% success rate.
• Although other types of osteosynthesis seem to have a similar success rate, osteosynthesis with load-bearing plates seems to be the treatment of choice.
• Primary autogenous bone grafting is an alternative conducive to uncomplicated healing and should be considered for selected cases of fracture of the extremely atrophied mandible.

Exerpted from Maxillofacial surgery by Peter Brennan.