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Angle of insertion and confirmation of angles measured after in vitro implantation during laminar vertebral stabilization in vertebral columns obtained from canine cadavers

Sebastian C. Knell Dr med vet1, Patrick Kircher Prof Dr med vet, PhD2, Matthias Dennler Dr med vet3, Pierre M. Montavon Prof Dr med vet4, Katja Voss Dr med vet5, and Karin Hurter Dr med vet6
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  • 1 Department of Small Animal Surgery, Vetsuisse Faculty, University of Zurich, 8057 Zurich, Switzerland.
  • | 2 Section for Diagnostic Imaging, Vetsuisse Faculty, University of Zurich, 8057 Zurich, Switzerland.
  • | 3 Section for Diagnostic Imaging, Vetsuisse Faculty, University of Zurich, 8057 Zurich, Switzerland.
  • | 4 Department of Small Animal Surgery, Vetsuisse Faculty, University of Zurich, 8057 Zurich, Switzerland.
  • | 5 University Veterinary Teaching Hospital Sydney, Faculty of Veterinary Science, University of Sydney, Sydney, NSW 2006, Australia.
  • | 6 Department of Small Animal Surgery, Vetsuisse Faculty, University of Zurich, 8057 Zurich, Switzerland.

Abstract

Objective—To determine angles of insertion for laminar vertebral fixation of L1 and L2 by use of a locking plate in dogs and to confirm screw placement by use of computed tomography (CT).

Sample—Vertebral specimens harvested from 8 canine cadavers.

Procedures—The point of insertion and minimum and maximum insertion angles for laminar and facet screws for laminar vertebral stabilization were determined by use of CT. A precontoured locking plate was then placed by use of 1 locking screw in the lamina of each lumbar vertebra and 1 nonlocking screw in the facet joint. The position and angle of the screws were examined by use of CT, and penetration into the vertebral canal was recorded.

Results—Mean ± SD insertion angles for L1 and L2 were 18 ± 4° and 21 ± 5° toward the vertebral canal and 11 ± 4.4° and 10 ± 3° in a dorsal direction, respectively. Insertion angles for the facet joint were between 24 ± 4° ventrally and 12 ± 2° dorsally. Insertion of the screw did not penetrate the vertebral canal for 23 of 24 (96%) screws. For 23 of 24 inserted screws, the previously determined angle was maintained and purchase of bone and cortices was satisfactory.

Conclusions and Clinical Relevance—Placement of laminar and facet screws in canine vertebrae was possible and can be performed safely if angles of insertion determined pre-operatively via CT are maintained.

Abstract

Objective—To determine angles of insertion for laminar vertebral fixation of L1 and L2 by use of a locking plate in dogs and to confirm screw placement by use of computed tomography (CT).

Sample—Vertebral specimens harvested from 8 canine cadavers.

Procedures—The point of insertion and minimum and maximum insertion angles for laminar and facet screws for laminar vertebral stabilization were determined by use of CT. A precontoured locking plate was then placed by use of 1 locking screw in the lamina of each lumbar vertebra and 1 nonlocking screw in the facet joint. The position and angle of the screws were examined by use of CT, and penetration into the vertebral canal was recorded.

Results—Mean ± SD insertion angles for L1 and L2 were 18 ± 4° and 21 ± 5° toward the vertebral canal and 11 ± 4.4° and 10 ± 3° in a dorsal direction, respectively. Insertion angles for the facet joint were between 24 ± 4° ventrally and 12 ± 2° dorsally. Insertion of the screw did not penetrate the vertebral canal for 23 of 24 (96%) screws. For 23 of 24 inserted screws, the previously determined angle was maintained and purchase of bone and cortices was satisfactory.

Conclusions and Clinical Relevance—Placement of laminar and facet screws in canine vertebrae was possible and can be performed safely if angles of insertion determined pre-operatively via CT are maintained.

Contributor Notes

Address correspondence to Dr. Knell (sknell@vetclinics.uzh.ch).