Displacement and Strain of the Obturator Nerve During Neurodynamic Testing with Various Limb Positions and Sensitizing Maneuvers in Cadavers

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2021-12

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Background: The obturator nerve can be injured during surgery or trauma. Neurodynamic testing of the obturator nerve is theorized to identify obturator nerve involvement post injury using varying limb positions and sensitizing maneuvers. Sensitizing maneuvers for the obturator nerve are theorized to enhance neurodynamic testing of the obturator nerve. There is no objective evidence to support the use of sensitizing maneuvers during neurodynamic testing of the obturator nerve. Objective: The objective of this study was to evaluate the displacement and strain of the obturator nerve within the pelvis at end range hip abduction during various hip positions (hip neutral, hip flexion, hip extension) and sensitizing maneuvers (hip external rotation, knee extension, knee flexion). Design: One-Way Repeated Measures Design. Methods: Nine cadavers aged 79.6 ± 10.6 years were selected by consecutive sampling, and metal markers were glued to the exposed obturator nerves in situ. Cadavers were secured in a sidelying slumped knee bend position. Radiographic images of the obturator nerve markers were taken to examine displacement and strain during end range hip abduction incorporating various limb positions (hip neutral, hip extension, hip flexion) and sensitizing maneuvers (hip external rotation, knee flexion, knee extension). The images were digitized, and displacement and strain values were calculated by a customized MATLAB program. Statistical analyses were performed using SPSS. Results: The obturator nerve was significantly displaced distally 3.31 ± 2.14 mm (p=0.003), laterally 3.36 ± 3.18 mm (p=0.013) and altered strain -2.96 ± 2.72 % (p=0.018) with hip extension and displaced distally during hip neutral 2.76 ± 2.46 mm (p=0.015). Sensitizing maneuvers displaced the obturator nerve proximally from the reference position -4.11 ± 4.66 with a median of -3.88 mm compared to hip external rotation 2.36 ± 4.83 mm with a median of 2.16 mm (p=0.008). Hip external rotation was significantly different when compared between groups to knee flexion 4.89 ± 5.32 with a median of 3.59 (p=0.008). Conclusion: Neurodynamic testing of the obturator nerve resulted in significant distal displacement during end range hip abduction incorporating hip neutral position, while incorporating hip extension resulted in displacement distally and laterally with altered strain values. The obturator nerve is displaced proximally with hip external rotation and distally to the knee flexion position when compared to hip external rotation.

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