The skull and mandible

image of The skull and mandible
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Head trauma may result in fractures of the calvaria, the maxilla, the mandible and the detention, or any combination of these. This chapter covers principles of maxillofacial fracture treatment, techniques for managing maxillofacial fractures, management of specific fractures, fractures of the calvaria. Intraoral techniques; Mandibular symphyseal wiring; Application of external skeletal fixation to the mandible or maxilla; Ventral approach and plate application to the mandibular body; Surgical approach to the temporomandibular joint and condylectomy.

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Image of 17.1
17.1 Schematic view of the canine skull showing normal dental occlusion. The mandibular canine tooth is positioned in the middle of the space between the maxillary lateral incisor and canine tooth (rostral dotted line) and the cusp of the mandibular fourth premolar is positioned between the maxillary third and fourth premolars (caudal dotted line). Drawn by Vicki Martin Design, Cambridge, UK and reproduced with her permission.
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17.2 Biomechanics of mandibular fractures. (a) A fracture perpendicular to the long axis of the body of the mandible will tend to open at the dorsal end of the fracture line. (b–c) For oblique fractures, stability will depend on the angle and direction of the obliquity. (b) A fracture line that runs from dorsocaudal to ventrorostral is favourable because muscle forces compress the fracture line and it will be inherently stable. (c) A fracture line that is oriented from dorsorostral to ventrocaudal is unfavourable because muscle forces lead to distraction of the rostral fragment. Drawn by Vicki Martin Design, Cambridge, UK and reproduced with her permission.
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17.3 Lateral view of the skull showing the three primary lines of buttress support. The lines of the buttress support follow the thicker sections of bone (as identified by transillumination). A = the medial (or rostral) nasomaxillary buttress; B = the lateral zygomaticomaxillary buttress; C = the caudal pterygomaxillary buttress.
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17.4 The application of a tape muzzle. Three pieces of adhesive tape are used for the basic muzzle. (a) The first piece encircles the muzzle (sticky side out). (b) A second strip of tape is then placed around the back of the head with each end running alongside the muzzle (sticky side out). The ends should be of sufficient length to fold back behind the ears again after a third piece of tape has been applied. (c) A third strip of tape is placed around the muzzle (sticky side down) to bind in the second piece. The ends of the second piece are now folded back on themselves and anchored behind the head. (d) A fourth strip acting as a chin strap may be added. Drawn by Vicki Martin Design, Cambridge, UK and reproduced with her permission.
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17.5 Maxillomandibular ESF in a 3-year-old cat. Wires are driven laterally across the maxilla and mandible, avoiding the tooth roots. Following reduction of the fracture the jaw is opened slightly and acrylic applied to link the ends of the pins. (Courtesy of T Gemmill)
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17.6 Intercanine acrylic bonding. Note that the mouth has been left partially open to allow the intake of liquidized food.
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17.7 Application of a BEARD. (a) A three-dimensional reconstructed CT image of a 9-week-old puppy with a fracture of the ramus of the mandible and separation of the mandibular symphysis. (b–c) A cerclage wire was placed to stabilize the symphysis and a BEARD. Note that an oesophagostomy tube has also been placed (b = lateral view; c = rostral view). (d) The position of the suture is shown in a cat. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.
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17.8 Application of a labial reverse suture through buttons. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.
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17.9 ESF of a mandibular body fracture. (a) Lateral and (b) dorsoventral radiographs of a dog with a fracture of the mandibular symphysis and an oblique fracture of the right mandibular body. (c) The mandibular body fracture was stabilized with the placement of ESF pins and (d) the application of an acrylic connecting bar. (e) The immediate postoperative radiograph shows the implant positioning, (f) which despite its cumbersome appearance is well tolerated by the dog. (Courtesy of P Witte)
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17.10 Bone plating of a mandibular body fracture. Preoperative (a) lateral and (b) dorsoventral radiographs of an oblique mandibular body fracture, and (c) the clinical appearance of the fracture. (d) The fracture was stabilized with biaxial locking plates. Immediate postoperative (e) lateral and (f) dorsoventral radiographs demonstrating the lateral and ventral locking plate placement.
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17.11 Circumferential wiring of a mandibular symphyseal fracture in a cat. (a) A small midline incision is made on the chin ventral to the canine teeth and a large bore (16 G) hypodermic needle is inserted through the incision to emerge intraorally through the mucosa just lateral and caudal to the canine tooth. (b) A 0.8 mm wire is passed through the needle to emerge orally. The procedure is then repeated on the opposite side, with the wire passed through the oral end of the needle to emerge ventrally. (c) The hypodermic needle is withdrawn and the loop of wire is pulled tight. (d) The fracture is reduced and the two ends of the wire are twisted together to stabilize the fracture. The wire is cut and the twisted ends are bent over to lie under the skin surface.
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17.12 (a) Transverse CT image of a cat at the level of the TMJs showing a fracture of the medial aspect of the right condyloid process. This is a common injury in cats and is often not appreciated on radiographs. (b) Three-dimensional reconstruction of the images of the same cat showing a concurrent median fracture of the hard palate and mandibular symphysis.
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17.13 (a) Cat with multiple fractures of the mandible and maxilla including a median fracture of the hard palate and a fracture of the mandibular symphysis. (b) Three-dimensional reconstructed CT image of the same cat. (c) Transverse CT image at the level of the TMJs showing fractures of the condyloid processes and the mandibular fossa region of the temporal bone on the right.
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17.14 Lateral radiograph of a cat with a fracture of the calvaria (arrowed).
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17.15 Exposure and reduction of fractures of the calvaria. Drawn by Vicki Martin Design, Cambridge, UK and reproduced with her permission.
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17.16 (a) Interdental wire placement on the mandible of a large-breed dog using 0.6 mm diameter orthopaedic wire in a Stout loop pattern. The loops should be placed on the lingual aspect. (b) The loops are then twisted tight and bent to lie flat interdentally. (c) ‘Cold-cure dental acrylic is applied over the interdental wiring. The acrylic is applied bilaterally on the premolars and on the lingual aspect only caudal to the first molar tooth. (d) ‘Cold-cure’ temporary crown and bridge material in a re-usable applicator gun.
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17.17 Ventral exposure of a mandibular body fracture (see text for details).
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17.18 Surgical exposure of the TMJ (see text for details).
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17.19 Site of condylectomy at the base of the neck of the condyloid process at the level of the mandibular notch (red line).
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