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Miniplate osteosynthesis of mandible fractures
m MINIPLATE OSTEOSYNTHESIS OF MANDIBLE FRACTURES LAWRENCE MARENTETTE, MD
Plate osteosynthesis has become standard treatment for patients with fractures of the mandible by affording anatomic reduction, rigid fixation, and immediate function. Miniplate osteosynthesis offers several advantages over compression osteosynthesis. Intraoral plate placement eliminates facial scars and the potential for injury to the marginal mandibular branch of the facial nerve. It also allows for simultaneous reduction, fixation, and occlusal adjustment. The results of miniplate osteosynthesis are comparable to compression osteosynthesis, and this technique should be considered standard in the treatment of patients with mandibular fractures.
The traditional fixation of mandibular fractures included maxiUomandibular fixation, wire fixation with supplemental maxillomandibular fixation, and external fixation. With the advent of rigid internal fixation, compression plates afforded a treatment modality in which fracture stabilization was adequately achieved, yet by eliminating the need for maxillomandibular fixation, allowed function of the mandible and adequate oral nutrition. Compression plates are placed along the inferior border of the mandible in a bicortical fashion, requiring a tension band, either in the form of an arch bar or a tension band plate placed high in the mandible. In addition to the symphyseal/parasymphyseal region, compression plates are traditionally placed through an extraoral approach, thereby placing at risk the marginal mandibular branch of the facial nerve as well as producing a visible neck scar. Michelet attempted to develop a system of miniature plates and screws to produce adequate fracture stability. The plates were placed in random fashion on the mandible with varying degrees of success. Professor Maxine Champy refined the technique and developed the miniplate osteosynthesis technique for mandibular fracture fixation. 1 His principles involve the placement of monocortical miniplates placed high on the mandible to neutralize tension or spreading forces along the alveolar border and use the compression forces along the inferior border of the mandible. The plates are designed via the intraoral root. Intraoral placement avoids external scars and potential injury to the marginal mandibular branch of the facial nerve while allowing simultaneous fracture reduction and fixation and exact occlusal adjustment. In his initial work, Champy performed biomechanical studies on cadaver mandibles in which he placed plates at varying positions on the mandibles and then subjected them to fractures induced by mechanical testing. Likewise, he tested the biting strength of volunteers in varying areas of the symphysis, parasymphysis, body, and angle regions. Based on his experimental results, he de-
From the Department of Otolaryngology, University of Michigan Medical Center, Ann Arbor, MI 48109-7633. Address reprint requests to Lawrence Marentette, MD, Department of Otolaryngology, University of Michigan Medical Center, 1904 Taubman, 1500 E Medical Center Dr, Ann Arbor, MI 48109°7633 Copyright © 1995 by W.B. Saunders Company 1043-1810/95/0602-0007505.00/0 86
signed an ideal line of osteosynthesis on which plates should be placed, that would neutralize tension and use compression (Fig 1).
PLATE PLACEMENT Miniplates are placed via the intraoral route. In the symphyseal and parasymphyseal area the approach is identical to that used for a genioplasty. The incision is made in the mucosa greater than 7 cm away from the gingival mucosal junction. This is carried down through the mucosa and submucosa to the periosteum, which is likewise incised. A subperiosteal dissection is then carded down to the inferior border of the mandible. The mental nerves are identified and preserved on each side of the dissection. In the body area an incision is made in an identical fashion, 7 m m or greater from the gingival mucosal junction. The incision is made perpendicular to the body of the mandible, superior to the mental foramen, preserving the nerve. A subperiosteal dissection is also performed and the fracture site is exposed only enough to allow plate placement. In the angle region, the approach is that of a sagittal split ramus osteotomy. An incision is made along the buccal surface of the mandible, extending from the level of the maxillary tuberos-
1
':
,
-
-
___
FIGURE 1. The proper position for miniplate fixation of mandible fractures, "Champy's Ideal Line of Osteosynthesis."
OPERATIVE TECHNIQUES IN OTOLARYNGOLOGY--HEAD AND NECK SURGERY, VOL 6, NO 2 (JUN), 1995: PP 86-88
FIGURE 2. The second miniplate is applied by using monocortical screws (inferiorly, bicortical screws may be used safely) along the inferior ideal osteosynthesis line. This is above the inferior border. In the symphyseal region, two miniplates are necessary to overcome the torsional forces acting in this area. ity, curving inferiofly and anteriorly along the buccal surface, extending anterior toward the first molar approximating that of the external oblique line. The dissection is carried out in a subperiosteal fashion, which exposes the angle fracture. The area in the retromolar trigone is also exposed medially.
SYMPHYSEAL/PARASYMPHYSEAL FRACTURES After exposure of the fracture site, two plates are placed to provide adequate stabilization. The first plate is placed along the inferior border of the mandible along the ideal line of osteosynthesis. Two screws are placed on each side of the fracture site. The second plate is placed approximately 5 mm above the first plates also with two screws on each side of the fracture site (Fig 2).
BODY FRACTURES After achieving fracture site exposure, at least a four-hole miniplate is placed along the ideal line of osteosynthesis, which in this region corresponds to the area immediately
FIGURE 4. A second miniplate may be placed below the first for added stability. It should be placed below the inferior alveolar canal. below the tooth roots and above the mandibular canal (Fig 3). After plate placement, the fracture site stability is checked and if the question remains regarding stability, then a second plate is placed below the mandibular canal (Fig 4).
ANGLE FRACTURES After adequate exposure of fractures of the mandibular angle, the fracture site is reduced. Often this requires fracture site reduction followed by placement in intermaxillary fixation to allow adequate stability of the proximal fragment. The fracture site anatomically is reduced and the occlusion is placed into eccentric occlusion. The plate is then bent and contoured to follow the course of the oblique line. Two screws are placed on each side of the fracture site, thereby producing fracture site stability. A second plate is placed along the line of osteosynthesis on the buccal cortex. The screws need to be inserted through a transbuccal approach using a transbuc-
I
FIGURE 3. A single miniplate is placed along the ideal osteosynthesis line of tension, using at least a four-hole plate, although a longer plate is preferable. This is approximately 1.5 to 2 crown heights below the gingival margin. This corresponds to the area between the tooth roots and the inferior alveolar canal. Monocortical screws are used, placing them sequentially, one at a time. Transbuccal application may be necessary. MARENTETTE
,f
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FIGURE 5. Oblique line and superior buccal plates. 87
cal trocar system (Fig 5). As an alternative technique, the buccal plate may be placed first that provides adequate fracture site stability. After this, maxillomandibular fixation may be released and any oblique line plate may be contoured and placed in an easier fashion.
DISCUSSION Miniplate osteosynthesis affords a reliable method of providing internal fixation of mandibular fractures without the need for intermaxillary fixation. The technique has the advantage of allowing intraoral plate fixation while simultaneously adjusting the occlusion. The complication rate of intraoral rigid fixation application is equal to that of external a p p r o a c h fracture site fixation. Miniplate osteosynthesis affords the advantage of using smaller plates than those used with compression osteosynthesis, thereby making plate removal caused by asymmetries of the mandible from larger plates unnecessary. In summary, miniplate osteosynthesis is a reliably
88
proven technique that affords rigid fixation of mandibular fracture sites via the intraoral route, avoiding scarring on the face and potential for damage to the marginal mandibular branch of the facial nerve. It also allows for a simultaneous correction of the occlusion as well as fracture site reduction. Miniplate osteosynthesis may not be indicated in noncompliant patients in w h o m a regular diet is required. In these patients, consideration should be given to compression plate osteosynthesis. For patients who would be compliant with soft diet for 6 weeks, miniplate osteosynthesis should be considered as one of the treatments of choice.
REFERENCE 1. ChampyM, WilkA, SchnebelenJ: Die behandlung der mandibularfrakturen mittels osteosynthese ohne mtermaxillareruhigsteUung nach der techmk yon F.X. Michelet. Deutsche Zahn-, Mund-, und Kieferheflkundemlt Zentral blatt 63:339,1975
MINIPLATE OSTEOSYNTHESIS
Plate osteosynthesis has become standard treatment for patients with fractures of the mandible by affording anatomic reduction, rigid fixation, and immediate function. Miniplate osteosynthesis offers several advantages over compression osteosynthesis. Intraoral plate placement eliminates facial scars and the potential for injury to the marginal mandibular branch of the facial nerve. It also allows for simultaneous reduction, fixation, and occlusal adjustment. The results of miniplate osteosynthesis are comparable to compression osteosynthesis, and this technique should be considered standard in the treatment of patients with mandibular fractures.
The traditional fixation of mandibular fractures included maxiUomandibular fixation, wire fixation with supplemental maxillomandibular fixation, and external fixation. With the advent of rigid internal fixation, compression plates afforded a treatment modality in which fracture stabilization was adequately achieved, yet by eliminating the need for maxillomandibular fixation, allowed function of the mandible and adequate oral nutrition. Compression plates are placed along the inferior border of the mandible in a bicortical fashion, requiring a tension band, either in the form of an arch bar or a tension band plate placed high in the mandible. In addition to the symphyseal/parasymphyseal region, compression plates are traditionally placed through an extraoral approach, thereby placing at risk the marginal mandibular branch of the facial nerve as well as producing a visible neck scar. Michelet attempted to develop a system of miniature plates and screws to produce adequate fracture stability. The plates were placed in random fashion on the mandible with varying degrees of success. Professor Maxine Champy refined the technique and developed the miniplate osteosynthesis technique for mandibular fracture fixation. 1 His principles involve the placement of monocortical miniplates placed high on the mandible to neutralize tension or spreading forces along the alveolar border and use the compression forces along the inferior border of the mandible. The plates are designed via the intraoral root. Intraoral placement avoids external scars and potential injury to the marginal mandibular branch of the facial nerve while allowing simultaneous fracture reduction and fixation and exact occlusal adjustment. In his initial work, Champy performed biomechanical studies on cadaver mandibles in which he placed plates at varying positions on the mandibles and then subjected them to fractures induced by mechanical testing. Likewise, he tested the biting strength of volunteers in varying areas of the symphysis, parasymphysis, body, and angle regions. Based on his experimental results, he de-
From the Department of Otolaryngology, University of Michigan Medical Center, Ann Arbor, MI 48109-7633. Address reprint requests to Lawrence Marentette, MD, Department of Otolaryngology, University of Michigan Medical Center, 1904 Taubman, 1500 E Medical Center Dr, Ann Arbor, MI 48109°7633 Copyright © 1995 by W.B. Saunders Company 1043-1810/95/0602-0007505.00/0 86
signed an ideal line of osteosynthesis on which plates should be placed, that would neutralize tension and use compression (Fig 1).
PLATE PLACEMENT Miniplates are placed via the intraoral route. In the symphyseal and parasymphyseal area the approach is identical to that used for a genioplasty. The incision is made in the mucosa greater than 7 cm away from the gingival mucosal junction. This is carried down through the mucosa and submucosa to the periosteum, which is likewise incised. A subperiosteal dissection is then carded down to the inferior border of the mandible. The mental nerves are identified and preserved on each side of the dissection. In the body area an incision is made in an identical fashion, 7 m m or greater from the gingival mucosal junction. The incision is made perpendicular to the body of the mandible, superior to the mental foramen, preserving the nerve. A subperiosteal dissection is also performed and the fracture site is exposed only enough to allow plate placement. In the angle region, the approach is that of a sagittal split ramus osteotomy. An incision is made along the buccal surface of the mandible, extending from the level of the maxillary tuberos-
1
':
,
-
-
___
FIGURE 1. The proper position for miniplate fixation of mandible fractures, "Champy's Ideal Line of Osteosynthesis."
OPERATIVE TECHNIQUES IN OTOLARYNGOLOGY--HEAD AND NECK SURGERY, VOL 6, NO 2 (JUN), 1995: PP 86-88
FIGURE 2. The second miniplate is applied by using monocortical screws (inferiorly, bicortical screws may be used safely) along the inferior ideal osteosynthesis line. This is above the inferior border. In the symphyseal region, two miniplates are necessary to overcome the torsional forces acting in this area. ity, curving inferiofly and anteriorly along the buccal surface, extending anterior toward the first molar approximating that of the external oblique line. The dissection is carried out in a subperiosteal fashion, which exposes the angle fracture. The area in the retromolar trigone is also exposed medially.
SYMPHYSEAL/PARASYMPHYSEAL FRACTURES After exposure of the fracture site, two plates are placed to provide adequate stabilization. The first plate is placed along the inferior border of the mandible along the ideal line of osteosynthesis. Two screws are placed on each side of the fracture site. The second plate is placed approximately 5 mm above the first plates also with two screws on each side of the fracture site (Fig 2).
BODY FRACTURES After achieving fracture site exposure, at least a four-hole miniplate is placed along the ideal line of osteosynthesis, which in this region corresponds to the area immediately
FIGURE 4. A second miniplate may be placed below the first for added stability. It should be placed below the inferior alveolar canal. below the tooth roots and above the mandibular canal (Fig 3). After plate placement, the fracture site stability is checked and if the question remains regarding stability, then a second plate is placed below the mandibular canal (Fig 4).
ANGLE FRACTURES After adequate exposure of fractures of the mandibular angle, the fracture site is reduced. Often this requires fracture site reduction followed by placement in intermaxillary fixation to allow adequate stability of the proximal fragment. The fracture site anatomically is reduced and the occlusion is placed into eccentric occlusion. The plate is then bent and contoured to follow the course of the oblique line. Two screws are placed on each side of the fracture site, thereby producing fracture site stability. A second plate is placed along the line of osteosynthesis on the buccal cortex. The screws need to be inserted through a transbuccal approach using a transbuc-
I
FIGURE 3. A single miniplate is placed along the ideal osteosynthesis line of tension, using at least a four-hole plate, although a longer plate is preferable. This is approximately 1.5 to 2 crown heights below the gingival margin. This corresponds to the area between the tooth roots and the inferior alveolar canal. Monocortical screws are used, placing them sequentially, one at a time. Transbuccal application may be necessary. MARENTETTE
,f
J f
FIGURE 5. Oblique line and superior buccal plates. 87
cal trocar system (Fig 5). As an alternative technique, the buccal plate may be placed first that provides adequate fracture site stability. After this, maxillomandibular fixation may be released and any oblique line plate may be contoured and placed in an easier fashion.
DISCUSSION Miniplate osteosynthesis affords a reliable method of providing internal fixation of mandibular fractures without the need for intermaxillary fixation. The technique has the advantage of allowing intraoral plate fixation while simultaneously adjusting the occlusion. The complication rate of intraoral rigid fixation application is equal to that of external a p p r o a c h fracture site fixation. Miniplate osteosynthesis affords the advantage of using smaller plates than those used with compression osteosynthesis, thereby making plate removal caused by asymmetries of the mandible from larger plates unnecessary. In summary, miniplate osteosynthesis is a reliably
88
proven technique that affords rigid fixation of mandibular fracture sites via the intraoral route, avoiding scarring on the face and potential for damage to the marginal mandibular branch of the facial nerve. It also allows for a simultaneous correction of the occlusion as well as fracture site reduction. Miniplate osteosynthesis may not be indicated in noncompliant patients in w h o m a regular diet is required. In these patients, consideration should be given to compression plate osteosynthesis. For patients who would be compliant with soft diet for 6 weeks, miniplate osteosynthesis should be considered as one of the treatments of choice.
REFERENCE 1. ChampyM, WilkA, SchnebelenJ: Die behandlung der mandibularfrakturen mittels osteosynthese ohne mtermaxillareruhigsteUung nach der techmk yon F.X. Michelet. Deutsche Zahn-, Mund-, und Kieferheflkundemlt Zentral blatt 63:339,1975
MINIPLATE OSTEOSYNTHESIS