Lumbosacral junction pedicle-probing technique for implant corridors in cats: feasibility and limitations

Objective: To describe a pedicle-probing technique for determining safe implant corridors at the seventh lumbar vertebra (L7)-first sacral vertebra (S1) in cats and evaluate the feasibility, safety, positioning, and trajectory of drill tracts created with this technique. Methods: CT of lumbosacral spine was performed in 13 feline cadavers to determine safe pedicle corridors. Using the pedicle-probing technique, drill tracts were created in the pedicles of L7 and S1 with a blunt probe followed by a drill bit. Postoperative grading of pedicle drill tracts for canal breach was performed on CT using a 4-point classification. Drill tract positioning, trajectory, and proximity to ventral S1 foramina were also evaluated. Results: At L7, 20 of 26 drill tracts (76.9%) were fully contained within the pedicle, 3 (11.5%) had > 50% of their diameter within the pedicle, 1 (3.8%) had < 50% of its diameter within the pedicle, and 2 (7.7%) were fully within the vertebral canal. At S1, 24 drill tracts (92.3%) were fully contained within the pedicle, and 2 (7.7%) had > 50% of their diameter within the pedicle. Conclusions: The pedicle-probing technique was associated with a high rate of vertebral canal breach at L7, whereas a greater proportion of drill tracts at S1 were fully contained within the pedicles. Clinical Relevance: The pedicle-probing technique can facilitate safe implant corridors at L7-S1 in cats; however, a high rate of breaches at L7 and variations in drill tract positioning and trajectory emphasize technical difficulty.