Locking Reconstruction Plate 2.4 and Mini Plate 2.0 System
This plating system offers a solution for mandible and maxilla fracture treatment in canines. The Mini Plate 2.0 is available in thicknesses of 1.0 mm/1.25 mm/1.5 mm/2.0 mm to address a variety of stability requirements. Furthermore, one screw size (2.0 mm) fits all Mini Plate 2.0 options (Fig 1) with the possibility of using a 2.4 mm cortex emergency screw when needed.
For larger dog breeds, the Locking Reconstruction Plate 2.4, with a thickness of 2.5 mm, should be the choice for fracture fixation in the mandible. This plate takes 2.4 mm and 3.0 mm locking screws, 2.4 mm cortex screws, and optional 2.7 mm locking cortex emergency screws (Fig 2). To fulfill the shape variation of the jawbones over the various dog breeds, the plates can be contoured in all three dimensions with appropriate instrumentation for perfect fitting. To prevent soft-tissue irritation, the plates have a low profile and highly polished surface.
Locking Design
The locking design increases the bone-plate construct stability by using angular stable screws. At the same time, it decreases the risk of screw back-out and subsequent loss of fracture reduction over time. The threaded Mini Plate holes accept both cortex and locking 2.0 mm PlusDrive screws. This configuration allows an angulation of the cortex screws of 13-18 from the central axis. The Reconstruction Locking Plate has a closely spaced hole-design pattern for optimized fracture fixation in minimal bone stock with locking screws or cortex screws.
Case: Cocker Spaniel
(Case provided by Randy Boudrieau, Massachusetts, USA)
A 4-year-old castrated male cocker spaniel was admitted with a complex odontoma (confirmed by biopsy and histopathology) of the left mandible of 1.5 years duration. The CT image (Fig 3) shows the complex odontoma, and indicates an inhomogeneous mineral density within the mandible causing thinning/ disruption of the lateral cortex and tooth roots. The contiguous images demonstrated abnormal tissue spanning from PM3 to M1 of the left mandible.
Surgical reconstruction
A 12-hole Locking Reconstruction Plate 2.4 was contoured and secured to the ventrolateral mandibular border with three 3.0 mm locking screws inserted cranially and caudally. The most rostral 2 screws penetrated the canine tooth (a pulpectomy was first performed, since this is the only available point of screw purchase rostrally in the dog as the canine tooth fills the entire mandible at this location). The plate was then removed to facilitate resection of a 5 cm segment of the mandible from PM2 to M2 by transverse osteotomy between the teeth using an oscillating saw, obtaining 0.5-1 cm margins from the tumor. The plate was re-applied using the previous screw holes. The gingival margin was closed. An additional 16-hole, Mini Plate (intermediate size: 1.3 mm) was secured along the alveolar bone with four 2.0 mm locking screws cranially to the defect, and three 2.0 mm locking screws caudally. Two screws rostrally penetrated the canine tooth. The plate was anchored caudally to the coronoid crest of the ramus.
A block of compressive resistant matrix (CRM) was cut to fill this bone void, which was soaked with 2 mg of rhBMP-2. Fig 4 shows an intraoperative view of the 2 plates secured to the mandible and the CRM in place within the bone defect. The soft tissues were closed routinely. Immediate postoperative x-rays show the fixation (ventrodorsal view and lateral oblique view) (Fig 5). The radiopaque CRM can be observed spanning the 5 cm defect.
Follow-up x-rays at 7 months postoperatively (ventrodorsal view and lateral oblique view) (Fig 6) show healing of the defect (and resorption of the CRM), which was documented with a Jamshidi biopsy of the center of the original gap (Fig 7). The biopsy was performed at the same time as partial plate removal (Mini Plate) due to the intraoral plate exposure.
Long-term follow up of this dog was obtained in-hospital 26 months postoperatively (both plates were fully removed at 20 months postoperatively) (Fig 8), and via telephone follow-up 6 years postoperatively. At that time the dog was euthanized for an unrelated issue. However, the dog had done well with the mandibular reconstruction throughout this time frame.
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