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

Daniel P. Beaver DVM, DACVS1,2, Gary W. Ellison DVM, MS, DACVS3, Daniel D. Lewis DVM, DACVS4, Robert L. Goring DVM, DACVS5,6, Paul S. Kubilis MS7, and Curt Barchard DVM8
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  • 1 Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610- 0126.
  • | 2 Present address is Affiliated Veterinary Specialists, PA, 275 Corporate Way, Suite 100, Orange Park, FL 32073.
  • | 3 Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610- 0126.
  • | 4 Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610- 0126.
  • | 5 Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610- 0126.
  • | 6 Present address is Affiliated Veterinary Specialists, PA, 275 Corporate Way, Suite 100, Orange Park, FL 32073.
  • | 7 Wildlife Research Lab, Florida Game and Fresh Water Fish Commission, 4005 S Main St, Gainesville, FL 32601.
  • | 8 Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610- 0126.

Abstract

Objective—To identify risk factors for successful surgical management of dogs with atlantoaxial subluxation (AAS).

Design—Retrospective study.

Animals—46 dogs managed surgically for AAS.

Procedure—Age at onset of clinical abnormalities, duration of clinical abnormalities prior to surgery, radiographic appearance of the dens, type (dorsal or ventral procedure) and number (1 or 2) of surgeries performed, grade of postoperative atlantoaxial joint reduction, and neurologic status prior to surgery (preoperative), when dogs were discharged from the hospital (postoperative), and during a follow-up evaluation (final) were obtained from the dogs' medical records. Risk factors for surgical success and degree of neurologic improvement were identified and analyzed for predictive potential.

Results—Age at onset of clinical abnormalities ≤ 24 months 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.

Conclusions and Clinical Relevance—Age at onset of clinical abnormalities, duration of clinical abnormalities prior to surgery, and preoperative neurologic status are risk factors for success of surgical management of AAS in dogs. (J Am Vet Med Assoc 2000; 216:1104–1109)

Abstract

Objective—To identify risk factors for successful surgical management of dogs with atlantoaxial subluxation (AAS).

Design—Retrospective study.

Animals—46 dogs managed surgically for AAS.

Procedure—Age at onset of clinical abnormalities, duration of clinical abnormalities prior to surgery, radiographic appearance of the dens, type (dorsal or ventral procedure) and number (1 or 2) of surgeries performed, grade of postoperative atlantoaxial joint reduction, and neurologic status prior to surgery (preoperative), when dogs were discharged from the hospital (postoperative), and during a follow-up evaluation (final) were obtained from the dogs' medical records. Risk factors for surgical success and degree of neurologic improvement were identified and analyzed for predictive potential.

Results—Age at onset of clinical abnormalities ≤ 24 months 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.

Conclusions and Clinical Relevance—Age at onset of clinical abnormalities, duration of clinical abnormalities prior to surgery, and preoperative neurologic status are risk factors for success of surgical management of AAS in dogs. (J Am Vet Med Assoc 2000; 216:1104–1109)