Surgery
Procaine Penicillin (22 000 IU/kg IM), gentamicin sulfate (6.6 mg/kg IV)
and flunixin meglumine (1.1mg/kg IV) were administered preoperatively.
The horse was sedated with detomidine hydrochloride (0.1mg/kg IV) and
morphine (0.1mg/kg IV). General anaesthesia was induced with diazepam
(0.02mg/kg IV) associated with ketamine (2.2 mg/kg) and maintained with
isoflurane. The horse was positioned in dorsal recumbency with the head
and neck extended. A custom-made wedge was placed at the level of C3-C4
to stabilize the neck in a strict sagittal position with good alignment
of the cranial cervical vertebrae. The head was fixed to a separate
small table that could be adjusted independently from the surgery table
to create additional extension at the level of the atlantoaxial joint(Figure 2) . This enabled to improve the alignment of the two
main fragments and reduce the fracture. Radiography was used to
determine the amount of head extension needed.
After routine aseptic preparation and appropriate draping, a 20cm-skin
incision was made, centred over the axis. The cutaneous colli muscle was
bluntly dissected, and the sternohyoid and sternothyroid muscles were
separated at the midline to expose the trachea. Dissection was then
continued dorsally along the right side of the trachea until the longus
colli muscles were reached. The trachea was retracted towards the left
and two self-retaining retractors were placed to gain access to the
ventral aspect of the axis: A Ricard-Begoin retractor was placed at the
cranial end of the wound and a modified Beckman retractor at the caudal
end. The atlantoaxial and C2C3 joints were localized using radiography.
The aponeurosis of the longus colli muscles was incised from the cranial
to the caudal border of C2. Mayo scissors and a periosteal elevator were
used to divide the longus colli muscles. An Inge retractor was placed in
between the separated longus colli muscles to expose the ventral surface
of C2. The fracture line through the cranial mid-body of the axis was
palpated and visualized. Palpation and radiography confirmed correct
alignment of the axis and fracture reduction. The ventral spinous
process of the axis body was slightly flattened using a curved osteoma.
A 4.5mm five-hole T-LCP plate was contoured to fit the ventral aspect of
the axis. The first standard combi-hole was used as a landmark for plate
positioning and placed just caudal to the fracture line. The plate was
fixed to the cranial fragment using three locking head screws in the
stacked combi-holes. The screw lengths had been determined
preoperatively but even so, radiographs were taken strategically during
the procedure to make sure that the spinal canal was not entered during
drilling or screw placement. The caudal fragment was grasped with bone
forceps while a fourth locking head screw was placed through the second
standard combi-hole. The third, fourth and fifth standard combi-holes
were also filled with locking head screws. Finally, a 4.5mm cortical
screw was placed through the first standard combi-hole, instead of a
locking head screw, to avoid crossing the fracture line (Figure
3) . The wound was flushed abundantly with sterile saline solution. The
longus colli muscles and cutaneous colli muscles were apposed with a
simple continuous 2-0 polyglactin 910 suture. The skin was closed with
interrupted horizontal mattress 0 polydioxanone sutures and staples. The
wound was protected with a stent bandage and an antimicrobial adhesive
drape. Recovery was assisted with a single tail rope system and was
uneventful. A head and neck bandage was placed over the stent and the
horse was put back in the sling after recovery.