March 2005
Dr Gerhard Steenkamp

A 12 year-old Maltese is presented to you with an unstable fracture of the caudal mandible, 5weeks post surgery. The dog sustained the original fracture during a dogfight.

A Evaluate the accompanying radiograph with reference to the fracture repair
technique used to stabilise the caudal mandibular fracture.

B Why did treatment fail in this case?

C Explain the basic principles behind interfragmentary wire usage.

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Memorandum

A Single wires should always be used for interfragmentary wiring. In this case a single wire was twisted double before it was used for the original fracture repair. Twisting a wire on itself does not improve the strength of the wire and the multfilament nature thereof increases the surface area with resultant increased bacterial adhesion. There is secondary infection with bone loss in the fracture line surrounding the distal (caudal) root of the mandibular molar (409) tooth. Furthermore, there appears to be a fragment of non-vital bone (sequestrum) ventral to the distal root of the 409.

B Fractures extending through the tooth socket is associated with the highest incidence of complications. Infection is the main complication, as oral bacteria will enter the bone through the defect left between tooth root and socket. It is well known that teeth provides stability at a fracture site, but when the fracture involves the tooth socket the involved tooth should always be removed before stabilising the fracture to prevent osteomyelitis of the fracture site. In this case there is non-union and only little callus formation due to infection and sequestrum formation.

C Interfragmentory wires (intraosseus or interosseus wiring) can only be used in stable fractures with no bone loss. It is only in very stable, well interdigitating fractures that a single wire can be used. This wire should be placed perpendicular to the fracture line if possible.
In all other cases two wires should be used. The wires should never be placed parallel to each other as it does not achieve stability and can create a fulcrum around which the jaw will move. These wires should be placed with a diverging angle between them. Both scenarios may be combined with a tape/canvas mussle for further support.

Due to the marked bone loss in the case presented, I preferred to perform a cancellous bone graft and miniplate fixation of the mandible. All of this was done after the affected teeth were extracted, the area curetted and thoroughly lavaged. The patient was on intravenous antibiotic therapy peri-operative and send home on oral antibiotics as indicated by an antibiogram.

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