Impact of order of movement on nerve strain and longitudinal excursion: a biomechanical study with implications for neurodynamic test sequencing.
ABSTRACT It is assumed that strain in a nerve segment at the end of a neurodynamic test will be greatest if the joint nearest that nerve segment is moved first in the neurodynamic test sequence. To test this assumption, the main movements of the median nerve biased neurodynamic test were applied in three different sequences to seven fresh-frozen human cadavers. Strain and longitudinal excursion were measured in the median nerve at the distal forearm. Strain and relative position of the nerve at the end of a test did not differ between sequences. The nerve was subjected to higher levels of strain for a longer duration during the sequence where wrist extension occurred first. The pattern of excursion was different for each sequence. The results highlight that order of movement does not affect strain or relative position of the nerve at the end of a test when joints are moved through comparable ranges of motion. When used clinically, different neurodynamic sequences may still change the mechanical load applied to a nerve segment. Changes in load may occur because certain sequences apply increased levels of strain to the nerve for a longer time period, or because sequences differ in ranges of joint motions.
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ABSTRACT: Stretch tests are attractive in the diagnosis of nerve root or peripheral nerve lesion. Interpretation of the test results is often difficult since the distribution of tensile forces along the nerve caused by the test manoeuvre is not known. In this study the effect on median nerve tension of 22 positions of the arm was measured with ‘buckle’ force transducers. With the elbow in full extension and the hand in neutral position, altering the position of the shoulder significantly influenced tension in the proximal part of the median nerve; tension in the distal part was not influenced. With the shoulder in 90 ° abduction, dorsiflexion of the hand combined with an extended elbow resulted in an increased tension in both distal and proximal parts of the median nerve. Dorsiflexion of the hand combined with flexion of the elbow caused an increase in tension only in the distal part. At all sites of the median nerve the median nerve upper limb tension test caused a significantly higher tension than the radial and ulnar nerve upper limb tension tests. This study provides insight in the normal distribution of tensile forces along the median nerve and can have clinical consequences. For differentiating nerve root from peripheral nerve lesions a specific provocative tension test for the median nerve is advocated. The results of this study provide a theoretical basis for differentiating between lesions in the proximal and distal parts of the median nerve.Clinical Biomechanics. 01/1995;
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ABSTRACT: Stretch-induced neuropathy of the brachial plexus and median nerve in conventional perioperative care remains a relatively frequent and poorly understood complication. Guidelines for positioning have been formulated, although the protective effect of most recommendations remains unexamined. The similarity between the stipulated potentially dangerous positions and the components of the brachial plexus tension test (BPTT) justified the analysis of the BPTT to quantify the impact of various arm and neck positions on the peripheral nervous system. Four variations of the BPTT in three different shoulder positions were performed in 25 asymptomatic male participants. The impact of arm and neck positions on the peripheral nervous system was evaluated by analyzing the maximal available range of motion, pain intensity, and type of elicited symptoms during the BPTT. Cervical contralateral lateral flexion, lateral rotation of the shoulder and fixation of the shoulder girdle in a neutral position in combination with shoulder abduction, and wrist extension all significantly reduced the available range of motion. Elbow extension also challenged the nervous system substantially. A cumulative impact could be observed when different components were simultaneously added, and a neutralizing effect was noted when an adjacent region allowed for unloading of the nervous system. The experimental findings support the experientially based guidelines for positioning. Especially when simultaneously applied, submaximal joint positions easily load the nervous system, which may substantially compromise vital physiologic processes in and around the nerve. Therefore, even when the positioning of all upper limb joints is carefully considered, complete prevention of perioperative neuropathy seems almost inconceivable.Anesthesiology 08/2002; 97(1):75-81. · 5.16 Impact Factor
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ABSTRACT: Five fresh-frozen transthoracic cadaver specimens (ten upper extremities) were dissected in order to measure excursion and strain of the median nerve at the wrist and the elbow in association with different positions of the shoulder, elbow, wrist, and fingers. The relationships between motions of the joints and excursion and strain at the wrist and the elbow as well as between excursion and strain were also determined. When the wrist was moved from 60 degrees of extension to 65 degrees of flexion, the median nerve at the wrist underwent a mean total excursion of 19.6 millimeters (9.2 +/- 1.38 millimeters [mean and standard deviation] in extension and 10.4 +/- 1.50 millimeters in flexion). The change in strain was not measurable secondary to nerve-wrinkling. Motion of the fingers from hyperextension to full flexion caused a mean total excursion of 9.7 millimeters (6.3 +/- 1.31 millimeters in hyperextension and 3.4 +/- 1.04 millimeters in flexion) and a change in strain of 19.0 per cent. This change in strain became more pronounced when the wrist and the fingers moved in synergy. Such strain, if constant, has been shown to decrease microvascular perfusion and nerve conduction in rabbits. With motion of the shoulder, the mean total excursion of the median nerve at the elbow was 9.1 millimeters (4.4 +/- 1.64 millimeters in abduction and 4.7 +/- 1.81 millimeters in adduction) and the change in strain was 13.3 per cent. With motion of the elbow, the mean total excursion was 12.3 millimeters (12.3 +/- 4.20 millimeters in flexion and zero millimeters in the resting position) and the change in strain was not measurable because of the wrinkle effect in flexion. With motion of the wrist, the mean total excursion was 5.6 millimeters (4.3 +/- 1.95 millimeters in extension and 1.25 +/- 0.81 millimeters in flexion) and the change in strain was 14.8 per cent. With motion of the fingers, the mean total, excursion was 3.4 millimeters (2.6 +/- 1.13 millimeters in hyperextension and 0.80 +/- 0.92 millimeter in flexion) and the change in strain was 10.3 per cent. Motion of the wrist and the fingers induced profound excursion of the median nerve at the wrist, whereas motion of the shoulder and the elbow induced marked excursion of the median nerve at the elbow. These excursions were much more pronounced when a number of joints were moved in a composite manner. Any factor that might limit normal excursion, such as scarring, could induce strains that could adversely affect the function of the median nerve. The finding that the position and movement of the limb had a profound effect on excursion and strain of the median nerve at the wrist and the elbow may aid in the understanding of the pathophysiology of median-nerve neuropathy.The Journal of Bone and Joint Surgery 01/1997; 78(12):1897-903. · 3.23 Impact Factor