Cholera toxin subunit B (CTB) is a highly sensitive retrograde neuroanatomical tracer. With the new availability of fluorescent Alexa Fluor (AF) conjugates of CTB, multiple neuroanatomical connections can be reliably studied and compared in the same animal. Here we provide a protocol that describes the use of AF-CTB for studying connections in the central nervous system of rats. The viscous properties of CTB allow small and discreet injection sites yet still show robust retrograde labeling. Furthermore, the AF conjugates are extremely bright and photostable, compared with other conventional fluorescent tracers. This protocol can also be adapted for use with other neuroanatomical tracers. Including a 7-d survival period, this protocol takes approximately 11 to 12 d to complete in its entirety.

Objective: To evaluate the accuracy and safety of a novel patient-specific drill guide template for stabilizing the thoracolumbar vertebrae of dogs. Study design: Cadaveric experimental study and prospective case series. Sample population: Cadaveric canine thoracolumbar vertebral specimens (n = 3) and clinical cases of thoracolumbar spinal instability (n = 4). Methods: Computed tomography data of the thoracolumbar spines were obtained before surgery, and images were imported into imaging software. Optimum screw trajectories were selected for each vertebra, and drill guide templates were designed and fabricated with a 3-dimensional printing system. Drill guide templates were applied to cadaveric spine and clinical cases. Computed tomography imaging was performed after surgery, and planned and postoperative trajectories were compared to estimate the accuracy and safety of the drill guide templates. Results: Twenty-two drill holes were made in cadaveric spinal specimens. All drill holes were completely located in the bone. The overall mean screw deviation was 0.88 AE 0.36 mm. In clinical cases, 29 screws were placed in thoracolumbar vertebrae. Most (89.6%) of these screws were placed without evidence of vertebral canal invasion. One (3.5%) screw perforated the bone structure. The overall mean screw deviation was 1.16 AE 0.56 mm. Conclusion: Drill guide templates were useful for accurate intraoperative screw navigation in thoracolumbar fixation in small dogs. Clinical significance: The use of drill guide templates can be considered as an aid to safety and accuracy of screw placement in canine thoracolumbar instabilities.

Canine bone marrow-derived mononuclear cells yielded an apparently homogeneous population of MSCs after expansion in culture. Expanded canine MSCs constitutively expressed neuron or astrocyte specific proteins. Furthermore, increases of intracellular cAMP concentrations induced increased expression of GFAP on canine MSCs, which suggests that these cells may have the capacity to respond to external signals. Canine MSCs may hold therapeutic potential for treatment of dogs with neurologic disorders.

Atlantoaxial instability (AAI)/subluxation commonly occurs in small breed dogs. Ventral stabilization techniques using screws and/or pins and a plate or, more commonly, polymethylmethacrylate are considered to provide the most favorable outcome. However, the implantation of screws of sufficient sizes for long-term stability becomes challenging in toy breed dogs (e.g. <2 kg). We herein report the application of 3D printing technology to implant trajectory planning and implant designing for the surgical management of AAI in 18 dogs. The use of our patient-specific drill guide templates resulted in overall mean screw corridor deviations of less than 1 mm in the atlas and axis, which contributed to avoiding iatrogenic injury to the surrounding structures. The patient-specific titanium plate was effective for stabilizing the AA joint and provided clinical benefits to 83.3% of cases (15/18). Implant failure requiring revision surgery occurred in only one case, and the cause appeared to be related to the suboptimal screw-plate interface. Although further modifications are needed, our study demonstrated the potential of 3D printing technology to be effectively applied to spinal stabilization surgeries for small breed dogs, allowing for the accurate placement of screws and minimizing peri- and postoperative complications, particularly at anatomical locations at which screw corridors are narrow and technically demanding.

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