Functional evaluation outcomes correlate with histomorphometric changes in the rat sciatic nerve crush injury model: a comparison between sciatic functional index (SFI) and kinematic analysis

抄録

【Background/Purpose】

 Establishing a correlation between biomechanical functions and histomorphometric data in the rat sciatic nerve crush injury model would be important for accurate evaluation of the regeneration state without sacrificing animals; however, the existence of such correlation remains uncertain. Sciatic functional index (SFI) is a gold standard for functional evaluation, but intrinsic shortcomings cannot be overlooked. Kinematic analysis is recognized as a reliable and sensitive approach for functional evaluation, and ankle angle is most commonly used. Studies utilizing the toe angle for functional evaluation are scarce, and its changes following surgery remain unknown. This study aimed to define a correlation of ankle angle, toe angle, and SFI with histomorphometric data and to determine which of these parameters reflects the changes in histomorphometric data with time more accurately.

 

【Methods or Cases】

 Six rats were designated as the control group. Out of 30 rats that received surgery, six animals were randomly selected on the first, second, third, fourth, and sixth week after surgery for measurements of ankle and toe angles in the “toe-off” phase, and evaluation of SFI. In parallel, histomorphometric analysis was performed to determine the number of myelinated nerve fibers, the diameter of myelinated nerve fiber, the axon diameter, and the thickness of myelin sheath. Furthermore, we investigated changes in ankle angle, toe angle, SFI and histomorphometric data with time, and the correlation of ankle angle, toe angle, and SFI with histomorphometric data.

 

【Results】

 changes in SFI, ankle angle, and toe angle highly correlate with histomorphometric data but correlation coefficients of toe angle are significantly the highest and those of SFI are the lowest.

 

【Discussion/Conclusion】

SFI, ankle angle and toe angle parameters correlated with histomorphometric data in rat sciatic nerve crush injury model. Ankle angle and toe angle are capable of reflecting histomorphometric data more accurately than SFI.

 

【Ethical consideration, Informed consent】

This research was approved by the animal experimentation committee of Kyoto University, and all experiments were performed in accordance with the Guidelines of the Animal Experimentation Committee, Kyoto University.