Strut plate for fractures of the mandibular condylar process
Management of fractures in the different subregions of the condylar process is still a controversial topic. The topography of these subregions is delineated in the updated AO CMF Classification. Dislocation and displacement of the condyle bearing fragment, subsequent to neck or base fracture or condylar head fragment, occur in a multitude of patterns. Moreover, the status of dentition, degree of dislocation, condition of the patient, concomitant fractures of the mandible, and bimaxillary or panfacial fractures are all decisive factors when choosing either open or closed fracture treatment. Transfacial or transcutaneous surgical access to these anatomic zones is challenging due to the delicate location and presence of the marginal branch and the main stem of the facial nerve.
The three subregions of condylar head, condylar neck, and base of the condylar process are identified using specific landmarks and reference lines (Fig 1):
- The posterior ramus line (base line) running along the posterior border of the ascending ramus.
- The sigmoid notch line running through the deepest point of the sigmoid notch and perpendicular to the posterior ramus line.
- The condylar head reference line running perpendicular to the posterior ramus line below the lateral pole of the condylar head. The height of the lateral pole is determined by the diameter of a circle (2-D) or a sphere (3-D), whose arc best fits with the upper lateral boundaries of the lateral pole.
Nonetheless, during the last decade, open reduction and internal fixation techniques have been increasingly applied in treatment concepts accompanied by the development of standardized surgical approaches, instrumentation and osteosynthesis hardware. To circumvent the facial nerve and its branches, an endoscopically-assisted transoral approach has been advocated. From a biomechanical standpoint, a two mini-plate fixation for fractures of the base of the condylar process or the condylar neck was considered necessary to secure enough stability, and regarded most handy in application via the external or transoral route.
Along these lines of refinement and innovation, in 2011 a family of specialized implants was developed with the idea of providing optimized, single-plate solutions with sufficient strength and ease of use for fracture configurations at the level of the condylar base or the condylar neck. These include:
- the Lambda Plate
- the Trapezoidal Plate
The Lambda Plate is particularly suitable for fractures within the narrow-neck zone of the condylar process with its limited lateral bone surface. The linear upper fixation arm can be placed far cranially to extend over fracture lines even in the high neck. Though the plate may be applied within a wide vertical range down to the height of the mandibular foramen, it should not be overlapped by the anterior arm. The Lambda Plate comes in a left and right version. The converging midportion of the plate provides the required stability. The preferred surgical approach is external.
The Trapezoidal Plate is designed in a grid shape with two parallel rods at the top and the base connecting two larger merging bars at the sides. The distance between the holes at the top determines the uppermost placement position of the plate. Usually this will correspond to the width of the lower neck. The trapezoidal plate is conically molded to match with the curved lateral surface of the transitional zone between the base of the condylar process and the neck. The plate is applicable in a large diagonal field spanning downwards below the level of the sigmoid notch. The plate allows for external or transoral surgical approaches.
The newest plate type is the Strut Plate, consisting of a criss crossed framework of slender beams with an overall conical molding. This three-dimensional structure provides exceptional resistance to lateral bending stresses and supports the condylar process fragments most efficiently. The terrace like plate hole arrangement at the top of the plate facilitates a placement up into the midneck region, since it coincides with the natural backward angulation of the condylar process. The plate placement zone moves best parallel to the posterior border of the ascending ramus thus precluding any interference with the mandibular foramen or canal.
The Strut Plate comes in a left and right version and is commonly applied via an external approach. A transoral use is conditional on the rare prerequisite that the condyle bearing fragment is stable upon reduction.
Case: Mandible Fracture
Case provided by Carl-Peter Cornelius, Munich, Germany
An 84-year-old female patient with a triple fracture in the edentulous atrophic mandible (Luhr Class II): displaced condylar based fractures bilaterally in combination with a fracture in the anterior body on the right. Prosthetic restoration with full dentures.
Fig 1 Preoperative 3-D CT scans:
a) Frontal view. Right anterior body fracture associated with slight widening of the mandibular arch.
b) Dorsal view. Shortening of both rami due to lateral override displacement and medial angulation of both condylar bearing fragments, partial medial dislocation out of the fossa of the right condylar head.
c) Right lateral view. Lateral override of posteriorly displaced condyle bearing fragment and decreased ramus height.
d) Left lateral view. Lateral override position and posteromedial angulation of condyle bearing fragment.
e) Intraoperative situation. Reduced condyle bearing fragments fixed with strut plates via retromandibular transparotid approaches.
f) Intraoperative situation, showing the mandible after fracture reduction and right paramedian plate osteosynthesis.
g) Intraoperative situation. Reduced condyle bearing fragments fixed with strut plates via retromandibular transparotid approaches.
h) Intraoperative situation. Reestablished occlusion, with full dentures in place.
Fig 3: Postoperative panoramic x-ray
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