Hip abduction with hip extension produces the largest obturator nerve displacement: a cadaveric investigation.

BACKGROUND

The obturator nerve may be injured during surgery or trauma. Neurodynamic testing (NDT) is theorized to assist in obturator nerve injury identification, but the optimum hip position for NDT has not been biomechanically supported.

OBJECTIVES

This study evaluated the displacement and strain of the obturator nerve within the pelvis using three NDT positions of the hip (neutral, flexion, and extension) combined with hip abduction.

DESIGN

One-way repeated measures.

METHODS

Nine cadavers were selected by consecutive sampling, and metal markers were glued to the exposed intrapelvic obturator nerves in situ. Cadavers were secured in a side-lying slumped knee bend position, and fluoroscopic images of the intrapelvic obturator nerve were taken in a starting position. Images were repeated during three testing positions: end-range hip abduction with sagittal hip positions in neutral, flexion, and extension. Images were digitized, and displacement and strain values were calculated and compared. Alpha was set at 0.05, and data were analyzed.

RESULTS

The obturator nerve displaced distally from the starting position during end-range hip abduction with the sagittal hip position in neutral (mean = 2.76 ± 2.46 mm; p = 0.015) and extension (mean = 3.31 ± 2.14 mm; p = 0.003) but not with flexion. No lateral displacement or strain value differences were measured between the three testing positions (p = 0.948, p = 0.925, p = 0.359).

CONCLUSION

Obturator nerve NDT using end-range hip abduction with the sagittal hip position in neutral or extension significantly displaces the nerve distally, suggesting these positions may be most useful when performing NDT of the obturator nerve.