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Modified Ventral Stabilization Using Positively Threaded Profile Pins and Polymethylmethacrylate for Atlantoaxial Instability in 49 Dogs


  • Presented in part at 2010 ACVS meeting, Seattle, WA and at 2012 ECVS 21st Annual Scientific Meeting, Barcelona, Spain.

Corresponding Author

Takeshi Aikawa BVSc, Diplomate JCVS, Aikawa Veterinary Medical Center, 4-3-1Nishi Otiai, Shinjyuku-ku, Tokyo 161-0031, Japan.




To describe diagnostic findings, complications, and long-term outcome of dogs with atlantoaxial instability (AAI) that had modified ventral stabilization with positively threaded profile pins and polymethylmethacrylate by 1 surgeon and to evaluate the potential prognostic indicators.

Study Design

Retrospective case series.


Dogs (n = 49) with AAI.


Medical records (2000–2010) of dogs with AAI that had modified ventral stabilization were reviewed. Data on pre- and postoperative neurologic status, diagnostic findings, and outcomes were retrieved. Age, neurologic grade, duration of clinical abnormalities, dens abnormalities, and MRI findings were evaluated as the potential predictors for recovery. Age and cancellous bone grafting were evaluated as the potential predictors of postoperative pin breakage.


Two dogs died during the perioperative period. In 47 dogs with follow up (median: 29 months; range, 4–110 months), 46 dogs (94%) improved neurologically after surgery, but 1 dog did not become ambulatory. There were no long term complications that resulted in serious neurologic deterioration or that required additional surgery. Partial pin breakage (1–5 pins) occurred in 16 dogs at 1–27.5 months (median, 5 months) without neurologic deterioration. Only the nonambulatory preoperative grade was significantly (P = .002) associated with non/incomplete recovery compared with ambulatory dogs.


Adequate stabilization of the vertebrae and improved neurologic status were achieved in most dogs with AAI using a modified ventral stabilization technique with positively threaded profile pins and polymethylmethacrylate.

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