“Risk factors affecting the outcome of surgery for atlantoaxial subluxation in dogs: 46 cases (1978–1998).”

Beaver et al.

JAVMA 2000.

Results—Age at onset of clinical abnormalities ≤ 24months was significantly associated with greater odds of a successful first surgery and final outcome and a lower postoperative neurologic grade. Duration of clinical abnormalities ≤ 10 months was significantly associated with greater odds of a successful final outcome and a lower final neurologic grade. A preoperative neurologic grade of 1 or 2 was significantly associated with a lower final neurologic grade. Potential risk factors that did not affect odds of a successful outcome included type of surgery performed, grade of atlantoaxial joint reduction, radiographic appearance of the dens, or need for a second surgery.

“A Modified Ventral Fixation for Surgical Management of Atlantoaxial Subluxation in 19 Dogs.”

Platt et al.

Vet Surg 2004

Results—Adequate reduction and stabilization was achieved in all dogs based on radiographic assessment immediately after surgery. Improved neurologic outcome occurred in 16 dogs at 1 month and in 15 dogs at follow-up; 2 dogs died of post-operative complications within 24 hours of surgery. One dog was euthanatized at the owners’ request because of recurrent neck pain associated with implant failure after 1 month. Two dogs required surgery to remove broken and migrated implants, but further stabilization was not necessary.

After elevation and retraction of the longus colli muscles, and exposure of the C1–C2 joint by capsulotomy, a 1.5 or 2.0mm cortical bone screw was placed in the caudal half of the body of C2. A new (sharp) burr was used to drill the hole so that minimal pressure was required. The screw length was estimated from radiographs to allow the head and a short segment of the threaded portion to remain exposed with the tip of the screw in the dorsal cortex (Fig 1). Orthopedic wire was twisted around the head of the screw and caudoventral traction applied and maintained, reducing the luxation and holding the cranial aspect of C2 body stationary.

A second screw was then inserted into the cranial half of the C2 vertebral body and a traction wire attached to it. A small burr was then used to remove the easily accessible C1–C2 articular cartilage (Fig 2). Traction was maintained while two 0.035 Kirschner wires were passed from medial to lateral as transarticular pins, angled laterally and proximally toward the alar process of C1 as previously described.10 These wires were cut approximately 1 cm ventral to the body of C2. Three additional cortical bone screws were inserted, after tapping, in the ventral arch of C1, again leaving the heads and a short segment of the threaded portion exposed. A cancellous bone graft was obtained from the greater tubercle of the humerus and placed in the joint space.10 PMMA was molded over the exposed ends of the implants

“Outcomes and Complications Associated With Ventral Screws, Pins, and Polymethyl Methacrylate for Atlantoaxial Instability in 12 Dogs.”

Sanders et al.

JAAHA 2004.

Clinical outcomes and complications of a technique used for atlantoaxial stabilization were evaluated in a group of 12 dogs. At surgery, the atlantoaxial joint was realigned and rigidly fixated using cortical bone screws, K-wire, and polymethyl methacrylate. Results in nine dogs were graded as excellent. Results in two dogs were judged as good. One dog was euthanized 17 months after surgery for recurrent cervical pain. Eight dogs had no postoperative complications. Cortical bone screws were inserted into the medial aspect of each wing of the atlas caudal to the transverse foramen in a craniolateral direction. In all dogs, except for case no. 1, Steinman pins or Kwires were cut to bridge the distance between the screws. The entire apparatus was encased in PMM.

“A Modified Ventral Approach to the Atlantoaxial Junction in the Dog.”

Shores et al.

Vet Surg 2007.

Gelpi or Weitlaner retractors were positioned to retract the right carotid sheath to the left side and to separate the sternothyroideus and sternocephalicus muscles giving better visualization of the paired longus colli muscles, on the ventral surface of the cervical vertebrae, Adapting the Cechner approach to the AA junction requires only extending the division between the right sternocephalicus and the right sternothyroideus muscles cranially. As the sternothyroideus muscle is retracted medially, the larynx and its associated neural, vascular, and glandular (thyroid and parathyroid glands) structures are retracted with it and therefore away from the surgical field.

“Diagnosis and treatment of a chronic atlanto-occipital subluxation in a dog.”

Rylander et al.

JAAHA 2007

6 year Lab cross 6 weeks after being HBC.  Removal of compressive part of occipital bone improved the dog's condition