The critical threshold of blood flow associated with spinal cord ischemia in a modified rabbit model developed by ligation of lumbar arteries.

STUDY DESIGN

Animal study.

OBJECTIVES

To investigate the influence of lumbar arteries ligation on spinal cord blood flow (SCBF), and to determine by what proportion the SCBF decrease would cause spinal cord ischemia (SCI) in rabbit model.

SETTING

Sir Run Run Shaw Hospital, Zhejiang University School of Medicine.

METHODS

SCI model was established by ligation of lumbar arteries in rabbits. 20 rabbits were divided into four groups: group A, sham surgery without ligation; group B, ligation at 3 levels; group C, ligation at 4 levels; group D, ligation at 5 levels. The SCBF was measured with laser doppler flowmetry, motor function was assessed using modified Tarlov grading system, and neurophysiological integrity was detected with motor-evoked potential (MEP), followed by histological observation on the seventh day after operation.

RESULTS

Lumbar arteries ligation at 3 levels led to average 40% decrease of SCBF, and spinal cord remained functional, electrophysiological and histological normal. Lumbar arteries ligation at 4 levels resulted in average 50% decrease of SCBF, slight motor dysfunction, prolonged latency of MEP and decreased cell volume of neuron, rabbits presented mild spinal cord injury. Lumbar arteries ligation at 5 levels caused average 60% decrease of SCBF, complete paraplegia, loss of MEP waveform and neuron karyopyknosis, rabbits presented severe SCI.

CONCLUSION

More ligation of bilateral lumbar arteries leads to lower SCBF and increase the risk of SCI in rabbits, SCBF decreased by more than 50% could cause SCI. MEP associated significantly with SCBF, suggesting the usefulness of MEP to monitoring SCBF in surgery.