Computed Tomographic Evaluation of Safe Corridors for Pin Placement in Rabbit Thoracolumbar Vertebrae and Sacrum.

Abstract

Objective:  The aim of this study was to identify safe corridors for pin placement in the terminal thoracic vertebrae, lumbar vertebrae and sacrum of rabbits using computed tomography (CT) in cadaveric models.

Study design:  Computed tomographic imaging of 25 adult New Zealand white rabbit (Oryctolagus cuniculi) cadavers was evaluated. Safe insertion corridors at the cranial and caudal end cortical sections (ECS) of the vertebrae were determined using a multiplanar reconstruction software. Pins were placed to allow maximal bone purchase within the safe corridors. Post-procedure CT imaging was performed to evaluate the pin position.

Results:  The median safe corridor height in the thoracic and lumbar cranial ECS (2.54 mm; 1.39-3.97 mm) was significantly lower than that of caudal ECS (3.98 mm; 1.66-5.53 mm; p < 0.001). The mean widths of the left and right sacral safe corridors were not significantly different. Of the 99 pins placed, 70.7% of the pins were appropriately placed without vertebral canal impingement. Errors included partial canal impingement (12.1%), complete canal impingement (5.1%), inadequate bone purchase (7.1%), placement into the intervertebral disc space (1.0%) or in the incorrect ECS than intended (4.0%). The odds ratio of successful pin insertion without canal impingement was 2.77 (95% confidence interval, 1.04-7.43; p < 0.05) times higher in the caudal ECS than in the cranial ECS.

Conclusion:  The corridor identified in this study can be used as a guideline for pin placement in the thoracic and lumbar vertebrae of New Zealand white rabbits. Further biomechanical studies are required.