Computed tomographic study of safe implantation corridors in rabbit lumbar vertebrae.

Objectives: A study was performed to evaluate the lumbar vertebrae of domestic rabbits using computed tomography (CT) in order to identify safe corridors for implant insertion.

Methods: Computed tomography imaging of 20 adult New Zealand white rabbits was evaluated using three-dimensional multiplanar reconstruction, and safe corridors were determined. Following corridor determination, implant placement was performed, and imaging was repeated.

Results: The cranial and caudal endplates contained the majority of the vertebral bone stock, and were an average of 3.14 and 3.30 mm in length, respectively. The mean safe corridor angle was 62.9 degrees (range: 58.8-66.7), and the mean width of the corridor was 2.03 mm (range: 1.60- 2.07). Post-placement imaging revealed that 35% of the pins demonstrated errors of placement, most commonly canal impingement.

Conclusions: The results of the corridor evaluation indicate that an insertion angle of approximately 60 degrees relative to the sagittal midline is appropriate for implant insertion in the lumbar vertebrae of New Zealand white rabbits. Additionally, due to the hourglass shape of rabbit vertebrae, the endplates provide maximal bone stock for implant purchase, so insertion should be attempted in these regions. However, the high percentage of errors in placement indicate the need to more clearly define entry points to access the canal, and highlight the challenges of appropriate placement in the small bones of rabbits.