RESEARCH REPORT PLATFORM PRESENTATION

DIAGNOSTIC ULTRASOUND ASSESSMENT OF SCIATIC NERVE MOVEMENT DURING NEURAL MOBILISATION. Hing W¹, Ellis R¹, Allen S²; ¹Physical Rehabilitation Research Centre, Auckland University of Technology, New Zealand. ²Horizon Scanning, Auckland University of Technology, New Zealand

PURPOSE: The aim of this project is to assess movement of the sciatic nerve, using real-time ultrasound imaging during neural mobilisation techniques. The study assesses whether sciatic nerve movement occurs during neural mobilisation. RELEVANCE: Peripheral nerves must be able to dynamically move in relation to their surrounding tissues for efficient function. Pathological adherence or compression of peripheral nerves may impact on their ability to effectively move in respect to surrounding tissues, which may result in neural damage and dysfunction. A ‘slider’ is a neurodynamic technique designed to promote movement of peripheral nerves. Essentially tension is taken up from one end of the nerve trunk whilst it is simultaneously released from the opposite end. This sequence is then reversed allowing longitudinal sliding to occur. In pathological situations where nerve movement may be reduced, it would potentially be helpful to quantify movement loss or restriction and also to allow comparison of relative neural movement pre- and post-intervention. Objective measurement of nerve movement using real-time ultrasound, may be extremely useful clinically. There are numerous studies which have measured longitudinal nerve movement, of upper limb nerves using real-time ultrasound. As for the sciatic nerve, there appears to be no ultrasound studies that make any quantifiable analysis or measurement. PARTICIPANTS: Subjects (n=15) who met the inclusion criteria were seated in a custom built standardised rig, specifically designed to maintain the subject in a slump position. METHODS: Ultrasound images from a Philips HD11 ultrasound machine using a linear array probe (5-12 MHz, 55mm) were collected. Two standardised positions of a) the mid-point of the posterior thigh (mid-thigh nerve bed) and b) at the level of the popliteal crease were visualised. At each of these positions recordings within the transverse plane and the longitudinal plane were collected. The video loops were then converted to digital format using conversion software. For the purpose of this study, a neurodynamic ‘slider’ was utilised in order to allow movement of the sciatic nerve. ANALYSIS: A method of frame-by-frame cross-correlation analysis (Dilley et al. 2001) was utilised to determine and measure the relative in-vivo nerve movement between successive frames in the sequence of ultrasound images. RESULTS: Transverse movement of (mean±SD) 4.42±0.89mm vertical and 7.29±2.33mm horizontal was measured at the popliteal crease compared with 0.69±0.31mm vertical and 0.83±0.43mm horizontal measured at the mid-thigh nerve bed location. Longitudinal nerve movement measured 0.87±0.09mm at the popliteal crease compared to 2.18±0.59mm at mid-thigh nerve bed. CONCLUSIONS: In line with the ‘convergence theory,’ a greater degree of transverse movement (versus longitudinal movement) was measured at the popliteal crease location while the opposite was observed at the mid-thigh nerve bed. This research confirms that varying degrees of transverse and longitudinal movement do occur and supports the suggestion that neural mobilisation can be effective in the treatment of altered neurodynamics. IMPLICATIONS: This research may validate the claim that its effectiveness is due to movement of peripheral nerves in relation to surrounding tissues. Therefore, if the hypothesis of this project is accepted, then there may be a wider implication for ultrasound imaging of neural mobilisation in pathological populations. KEYWORDS: diagnostic ultrasound, neural, mobilisation. FUNDING ACKNOWLEDGEMENTS: New Zealand Society of Physiotherapy and the Auckland University of Technology. CONTACT: wayne.hing@aut.ac.nz

ETHICS COMMITTEE: AUTEC – Auckland University of Technology Ethics Committee