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Chapter 25: Vertebral Fracture and Luxation Repair 213

Table 25.1 Recommended insertion angles and landmarks for bicortical spinal
implants.
Location Insertion angle from Landmarks for insertion
vertical
T10 22° (20–25°) Tubercle of ribs and base of accessory
T11 28° (25–35°) process
T12 30.5° (25–35°)
T13 44.5° (40–45°)
L1–L6 60° (55–65°) Junction between pedicle and
transverse process
Source: Watine et al. [5].

part of the lamina. Bone stock for implants is limited to the gener­
ally small and narrow vertebral body. Rib head disarticulation can
be performed if needed for improved implant position.
Alternatively, ribs may be utilized for certain types of fixation
methods such as cerclage wiring to augment spinal stapling. The
approach has to consider the thoracic cavity and the possible crea­
tion of an iatrogenic pneumothorax. If the pleural space is opened,
air can often be evacuated in conjunction with closure of the surgi­
cal site via a large‐gauge over‐the‐needle catheter or temporary
chest tube. Lumbar vertebrae have distinct articular, transverse,
and accessory processes, which provide helpful anatomical land­
marks for implantation. General guidelines for insertion angles
and landmarks for traditional bicortical implants are available
(Table 25.1) but should be supplemented with CT images of the
individual patient [5]. While the larger insertion angle for lumbar
vertebrae (60° from vertical) provide maximum bone purchase
based on imaging studies, this angle is challenging to achieve with
a standard open approach due to soft tissue interference. Often the
Figure 25.6 A locking compression plate (LCP) is applied to the ventral angle is reduced to 30–45° to accommodate musculature without
aspect of the cervical spine with monocortical screw fixation. dramatic loss of bone purchase.
placed into the bone near the endplate on both sides of a disc space. Positioning and Approach
While they are available in different lengths and sizes, their primary For a standard dorsal approach, the patient is positioned in ventral
application has been for cervical spondylomyelopathy rather than recumbency and a bean bag and suction are used to maintain a
cervical vertebral column trauma. straight body position. Additionally, tape can be used to further
improve patient stability. It is important to maintain the spine as
straight as possible to allow proper angling of pins into the vertebral
Thoracolumbar Injury column. A liberal standard dorsal approach to the affected thoracic
Vertebral column trauma most commonly affects the thoracolum­ or lumbar segments is performed. If the integrity of the vertebral
bar spine, with a high incidence of injury at the thoracolumbar canal has been compromised, extra caution must be employed to
junction. Fractures or luxations of the cranial thoracic spine are rare avoid inadvertent iatrogenic injury during elevation of the muscu­
due to the inherent stability and protection afforded by the muscu­ lature. The approach must reach ventral enough to expose the rib
lature of thoracic limbs and rib cage. The natural lever arm of the heads of the thoracic vertebrae or the base of the transverse pro­
lumbar spine against the less mobile thoracic spine creates a stress cesses of the lumbar vertebrae to observe pertinent landmarks and
riser at the thoracolumbar junction. aid in implant placement.
Hyperflexion injuries are overrepresented, leading to caudal end­
plate fractures and luxations at the affected disc space. Rotational Implant Selection
forces can lead to articular process fractures, while hyperextension can Implant size is based on vertebral pedicle width and vertebral body
cause fractures of the vertebral lamina. Fractures of ribs and spinous dimensions. Vertebrae of large dogs typically accept 3.5 mm screws
and transverse processes, while not affecting the spinal cord directly, or ⅛ inch pins, while smaller dogs usually require 2.7 mm screws or
must be taken as evidence of significant trauma and initiate a thor­ 3/32 inch pins. Depending on the implant type, the surgeon has a
ough evaluation of the integrity of the affected vertebral column. certain degree of freedom with implant sizes, for example when
using a pin–PMMA construct in a large‐breed dog, ⅛ inch pins
Anatomical Considerations can be placed for the main fixation with additional 3/32 inch pins.
The anatomy of thoracic vertebrae poses several challenges to In screw constructs, cortical screws are preferred over cancellous
instrumentation. The articular processes become less distinct in screws owing to their larger core and increased stiffness. In
the cranial thoracic vertebrae and rib head articulations obscure the PMMA construct, positive‐profile end‐threaded pins are