Correlation analysis of demographic and anthropometric factors, hip flexion angle and conus medullaris displacement with unilateral and bilateral straight leg raise.

Purpose: It has been shown that the conus medullaris displaces significantly and consistently in response to both unilateral and bilateral SLRs. Point of interest is represented by whether the magnitude of this displacement can be predicted in asymptomatic subjects. The purpose was to investigate whether any correlations existed between demographic and anthropometric factors and hip flexion angle with magnitude of conus medullaris displacement with the unilateral and bilateral SLR. This was done following the notion that there is the possibility that cord movement may contain aspects of predictability in asymptomatic subjects.

Methods: Using the same methods as in our previous MRI studies, we further investigated whether any correlations existed between age, height, weight, BMI or hip flexion angle and magnitude of conus medullaris displacement with the unilateral and bilateral SLR.

Results: Moderate to strong positive correlation was found between degree of hip flexion and magnitude of conus medullaris caudal displacement with unilateral and bilateral SLRs and CuMeD. A negligible inverse correlation between subjects' height and magnitude of conus medullaris displacement in response to unilateral SLR was found, while no correlation (r < 0.1) emerged with bilateral SLR and CuMeD. No correlation was found for other values such as age, weight or BMI.

Conclusions: The data show that in in vivo and structurally intact asymptomatic volunteers, the degree of hip flexion may have strong predictive values for magnitude of neural displacement in response to unilateral and bilateral SLRs. This provides further justification to its quantification in clinical settings. Magnitude of conus medullaris displacement in response to unilateral and bilateral SLRs is not likely to be predicted from easily clinically collectable measures such as age, height, weight and BMI. This study offers information relevant to investigation of prediction of neuromechanical responses in neurodynamic tests.