Authors of section

Author

Boaz Arzi

Executive Editor

Amy Kapatkin

General Editor

Frank Verstraete

Open all credits

Plate fixation

1. Principles

Defect nonunion fractures are managed in 1 stage when teeth are not present.

definition

If the teeth are present a two-stage approach is performed:

  • Stage 1: full-mouth dental radiographs, periodontal treatment and extractions of periodontally affected teeth. Periodontally affected teeth are common in the fracture area, especially in small breed dogs and cats.
  • Stage 2: approximately four weeks later, mandibular reconstruction using a regenerative approach is performed.

Note: a staged approach allows the soft tissue inflammation to subside before definitive repair of the nonunion

Restoration of occlusion and normal anatomy is crucial to avoid long term complications such as malocclusion, malunion, continued nonunion, refracture, facial asymmetry and loss of function.

Plate fixation in a mandible defect nonunion in a dog

2. Single stage approach

When a single stage approach is used, debridement and reconstruction are performed at the same time.

3. Two-stage approach

Pharyngeal intubation is needed to assess and maintain occlusion throughout and following the surgery.

Pharyngeal intubation in a dog

The mandible and maxilla should be closed in the desired occlusion. This will align the bones into normal occlusion

The technique uses 26 or 28 gauge wire. The wires are looped around all four canine teeth and twisted together to lock the mouth in normal occlusion.

Mouth locked in normal occlusion in a dog mandible with a defect nonunion

A standard ventral approach to the mandible is performed with the patient in dorsal recumbency.

The incision should expose enough intact bone to place at least two screws on both sides of the fracture.

Dog mandible nonunion defect ventral approach

4. Reduction

Fracture reduction is accomplished with 1-2 periosteal elevators placed at the fracture site to lever the caudal fragment into reduction to restore the normal anatomy. Bone holding forceps and sometimes digital reduction can be used.

Dog mandible defect nounion reduction

5. Fixation

Plate selection and preparation

The first choice is a 2.0mm titanium locking plate (a and b in the illustration).

If this is not available, for a medium or large breed dog, a single 2.4/3mm titanium locking mandibular reconstruction plate can be used (c). For small breed dogs and cats, a 2.0mm titanium mandibular reconstruction plate is used (d).

Dog mandible defect nonunion plate selection

If the locking plate is used, it is minimally contoured using bending pliers.

Dog mandible defect nonunion plate preparation

If the mandibular reconstruction plate is used, it is anatomically contoured in 3 dimensions using the appropriate bending pliers.

Note: 3D printed models of the skulls based on CT can be used to precontour the plates prior to surgery. Precontouring the plates saves time in the operating room and ensures the appropriate plate is available for surgery.

Dog mandible defect nonunion plate anatomical contour

The length of the plate should allow for 2-3 bicortical locking screws on both sides of the fracture.

Dog mandible defect nonunion plate positioning

Plate application

The plate is applied to span the fracture site and screw placement must avoid the mandibular tooth roots. The plate is placed ventral to the tooth roots and above the mandibular canal. A single plate is sufficient to stabilize the mandible.

Note: In small dogs and cats, due to limited bone stock, the screws often penetrate the mandibular canal.

Dog mandible defect nonunion plate application

Plate fixation

The plate is held in place using bone holding forceps. A locking drill guide is screwed into the plate to allow precise drilling of the hole.

Dog mandible defect nonunion plate fixation

The rostral screw closest to the fracture site should be inserted first alternating as illustrated until all screws are inserted.

Dog mandible defect nonunion plate fixation screw placement

The screw length is determined by a depth gauge measurement. Preoperative CT measurements can be used to estimate the screw length for planning purposes.

Dog mandible screw length measurement

The defect is filled with a Compression Resistant Matrix (CRM) or similar scaffold infused with rhBMP2 at a dose of 0.5mg/ml at a soak volume of 50%.

The infused scaffold is placed to fit snugly at the defect site.

If rhBMP2 is not available, cancellous autograft can be used instead.

After handling rhBMP2 it is important to change surgical gloves and not reuse any instruments that touched the rhBMP2.

Dog mandible defect nonunion plate fixation and defect filling with a compression resistant matrix (CRM)

6. Closure

The soft tissues are closed in 3 layers.

The first layer includes all the surrounding muscles, known as the soft tissue envelope, which will recruit progenitor cells that are critical for bone regeneration. The second layer is the subcutaneous tissue and the last layer is the skin.

Dog mandible defect nonunion plate fixation closure

7. Case example 1

Defect nonunion fracture in a small breed dog. The fracture gap is bridged with a 2.0mm titanium locking plate.

Case example of dog mandible defect nonunion plate fixation

Defect nonunion fracture in a small breed dog. The fracture gap has been filled with compression resistant matrix soaked with rhBMP2.

Case example of dog mandible defect nonunion compression resistant matrix application

8. Case example 2

2.4 reconstruction plate with cancellous autograft repair of a defect nonunion in a Labrador retriever.

Case example of dog mandible defect nonunion plate fixation

9. Aftercare

Multimodal analgesia is recommended. Non-steroidal medication for 10-14 days and opioids for the first 5 days post-surgery as needed. Antibiotic therapy is prescribed for a period of 10-14 days following surgery.

Soft food should be fed for the first 14 days, followed by a gradual return to eating kibble over 2 weeks. Rough play (i.e., tug of war) should be avoided for the first 3 months after surgery.

Suture removal is performed 10-14 days after surgery.

A radiographic recheck is performed every 6 weeks until the fracture is healed. The plate is not removed after the fracture is healed.