Further Standardization in the Aneurysm Clip: The Effects of Occlusal Depth on the Outcome of Spinal Cord Injury in Rats.

STUDY DESIGN: Experimental study.

OBJECTIVE: To evaluate the relationship between clip occlusal depth and functional and histological outcome measures in a rat model of thoracic spinal cord injury (SCI).

SUMMARY OF BACKGROUND DATA: Aneurysm clip compression is a proven model of contusion-compression SCI, but the relationship between clip depth and outcomes in thoracic SCI is unknown.

METHODS: A single aneurysm clip was applied to the spinal cord at thoracic vertebra 10 for 1 minute with an occlusal depth of 2, 6, or 10 mm. The actual compression force was measured using a self-made pulling method. Locomotor function was assessed for 28 days using Basso, Beattie, and Bresnahan (BBB) and inclined plane test (IPT) scores. We then used hematoxylin-eosin and Luxol fast blue staining to histologically quantify cavitation formation, preserved white matter, and preserved grey matter.

RESULTS: Greater occlusal compression depths caused greater actual compression forces and worsened functional and histological recovery. The 2- and 10-mm clip injury groups had significantly different BBB and ITP scores; cavitation, preserved white matter, and preserved grey matter volumes; and actual force measures (P < 0.05).

CONCLUSION: Our findings show that the occlusal depth of clip compression correlates with actual compression force and recovery impairment.

LEVEL OF EVIDENCE: 1.