Atlanto-axial ventral stabilisation using 3D-printed patient-specific drill guides for placement of bicortical screws in dogs

Authors: 
C Toni, B Oxley, S Behr
J Small Anim Pract. 2020 Aug 12. doi: 10.1111/jsap.13188.

Objective: To report outcome and complications following atlanto-axial stabilisation by polymethylmethacrylate applied to screws placed using 3D-printed patient-specific drill guides.

Materials and methods: Case series of dogs treated with this technique between May 2016 and August 2018 including pre- and post-operative modified Frankel score, imaging and complications. Screw placement was graded using a modified Zdichavsky classification based on post-operative CT. Telephone follow-up was obtained for surviving dogs.

Results: Twelve cases were included. At presentation, modified Frankel score was 3 in five dogs and 4 in seven dogs on presentation. Of 61 bicortical screws placed, 57 (93%) were fully contained within the pedicle and vertebral body and four (7%) partially breached the medial pedicle wall. Post-operative CT revealed good alignment of C1 and C2 in all planes. Reversible perioperative adverse events were described in five of 12 dogs and two dogs were euthanased shortly after discharge. At 18 to 50 days after surgery eight dogs had improved neurological status. Neurological status remained unchanged in the remaining two dogs. All dogs were reported ambulatory and pain-free at telephone follow-up (median 405 days post-surgery, range 180 to 780 days).

Clinical significance: This technique resulted in safe bicortical screw placement in dogs with atlanto-axial subluxation.

Small animal: