Nerve Excursion Research Articles

Altered tibial nerve biomechanics in patients with diabetes mellitus

Hyperglycemia associated with diabetes mellitus (DM) has adverse impacts on peripheral nerve connective tissue structure, and there is preliminary evidence that nerve biomechanics may be altered. Ultrasound imaging was utilized to quantify the magnitude and timing of tibial nerve excursion during ankle dorsiflexion in patients with DM and matched healthy controls. Tibial nerve longitudinal excursion at the ankle and knee was reduced, and timing was delayed at the ankle in the DM group. Severity of neuropathy was correlated with larger reductions in longitudinal excursion. Nerve cross-sectional area was increased at the ankle in the DM group. Larger tibial nerve size within the tarsal tunnel in patients with DM may restrict longitudinal excursion, which was most evident with more severe neuropathy. It is hypothesized that these alterations may be related to painful symptoms during functional activities that utilize similar physiological motions through various biomechanical and physiological mechanisms.

Femoral Nerve Strain at L4–L5 Is Minimized by Hip Flexion and Increased by Table Break When Performing Lateral Interbody Fusion

Anatomic studies have demonstrated that nerves and blood vessels have excursion with extremity range of motion. We have measured femoral nerve excursion with the lateral lumbar transpsoas interbody fusion (LLIF) procedure with changes in table flexion and ipsilateral hip flexion on both sides of 5 cadavers. To determine the effect of hip range of motion on femoral nerve strain near the L4-L5 disc space because it pertains to the LLIF procedure. Postoperative thigh symptoms are common after the LLIF procedure. Although nerve strain in general has been shown to impair function, it has not been tested specifically with LLIF. Five cadavers were placed in the lateral position as though undergoing the L4-L5 LLIF procedure. Radiographical markers were implanted into the femoral nerve. Lateral and anteroposterior fluoroscopic images were recorded with 0° initial table flexion and the hip at 0, 20, 40, and 60° flexion. The table was flexed to 40°, and the process repeated. Examination was repeated on the contralateral side and nerve strain and excursion were calculated. Table flexion results in preloading the femoral nerve when approaching L4-L5. Nerve strain was highest with the table flexed to 40° and the hip at 0° (average, 6%-7%). Strain in the femoral nerve decreased with increasing hip flexion for both table flexion angles. Anterior displacement of the nerve by approximately 1.5 mm was noted at 40° table flexion compared with 0°. Strain values with table flexion of 40° approached those associated with reduced neural blood flow in animal studies. Table flexion should be minimized to the extent possible when performing L4-L5 LLIF. Additionally, hip flexion to 60° can neutralize the neural strain that occurs with aggressive table flexion. N/A.

Normative sciatic nerve excursion during a modified straight leg raise test

Minimal data exists on how much sciatic nerve motion occurs during straight leg raise (SLR). The purpose of this study was to report preliminary normative ranges of sciatic nerve excursion using real time ultrasound during a modified SLR.The sciatic nerve was scanned in the posterior thigh in sixteen asymptomatic participants (age range 19–68 years). Nerve excursion was measured in transverse and longitudinal planes during knee extension from 90° to 0°, with the hip flexed to 30° and 60°. The ultrasound data was analysed off-line using cross correlation software. Results demonstrated that most nerves moved superficially during knee extension, a large proportion (10/16) moved laterally. Longitudinal excursion ranged from 6.4 to 14.7 mm (mean (SD) 9.92 mm (2.2)) in 30° hip flexion, and 5.1–20.2 mm (mean (SD) 12.4 mm (4.4)) in 60° hip flexion. Mean nerve excursion was significantly greater in 60° hip flexion (p = 0.02).There is a large between-subject variation in sciatic nerve excursion during this modified SLR in asymptomatic subjects. Mean nerve excursion was found to be higher with the hip pre-positioned in greater flexion, suggesting that pre-loading may not consistently reduce excursion.

Impact of Movement Sequencing on Sciatic and Tibial Nerve Strain and Excursion During the Straight Leg Raise Test in Embalmed Cadavers

Laboratory study, repeated-measures design. To quantify differences in sciatic and tibial nerve biomechanics (strain and excursion) during common variations of the straight leg raise (SLR) test. Hip flexion and ankle dorsiflexion are the primary movement components of the SLR. It has been suggested that the nervous system is loaded differently when ankle dorsiflexion is added before or after hip flexion. There are, however, no data to either support or refute this suggestion. Strain and excursion in the sciatic and tibial nerve were measured in the hip, knee, and ankle regions during 2 movement sequences for the SLR test in 10 embalmed cadavers. The proximal-to-distal sequence consisted of hip flexion followed by ankle dorsiflexion; the distal-to-proximal sequence consisted of ankle dorsiflexion followed by hip flexion. In the SLR end position, strain and excursion were comparable for both sequences for the sciatic and tibial nerve at the knee (P>.24). Strain in the tibial nerve at the ankle was greater with the proximal-to-distal sequence (P = .008), but the actual difference was small (0.8%). The pattern of strain increase and nerve excursion varied between sequences (P≤.009), with nerve strain increasing earlier and being maintained longer in regions closest to the joint that was moved first in the movement sequence. Varying the movement sequence does not substantially impact excursion and strain in the end position of the SLR. Therefore, if neurodynamic test sequencing is useful in the differential diagnosis of neuropathies, it is not likely due to differences in strain in the end position of testing.

Tibial Nerve Excursion During Lumbar Spine and Hip Flexion Measured with Diagnostic Ultrasound

Ultrasound imaging provides a method for non-invasive in vivo measurement of nerve motion resulting from joint movement. This study measured the proximal excursion of the tibial branch of the sciatic nerve at the popliteal fossa during forward bending in healthy subjects. Long-axis image sequences of the nerve were analysed using frame-by-frame cross-correlation software that calculated the longitudinal and axial movement of the nerve. Proximal excursion was calculated from the hypotenuse of these values. The mean proximal excursion recorded was 12.2 mm (SD 2.2 mm, n = 24). The reliability of three repeat measurements was found to be excellent (ICC 0.97, 95% CI 0.93–0.99; SEM 0.7 mm, n = 21). The protocol described provides a reliable method for analysing tibial nerve movement that could prove useful in future clinical studies.

The pattern of tibial nerve excursion with active ankle dorsiflexion is different in older people with diabetes mellitus

BackgroundThe peripheral nervous system has an inherent capability to tolerate the gliding (excursion), stretching (increased strain), and compression associated with limb motions necessary for functional activities. The biomechanical properties during joint movements are well studied but the influence of other factors such as limb pre-positioning, age and the effects of diabetes mellitus are not well established for the lower extremity. The purposes of this pilot study were to compare the impact of two different hip positions on lower extremity nerve biomechanics during an active ankle dorsiflexion motion in healthy individuals and to determine whether nerve biomechanics are altered in older individuals with diabetes mellitus. MethodsUltrasound imaging was used to quantify longitudinal motion of the tibial nerve and transverse plane motion of the tibial and common fibular nerves in the popliteal fossa during active ankle movements. FindingsIn healthy individuals, ankle dorsiflexion created mean tibial nerve movement of 2.18mm distally, 1.36mm medially and 3.98mm superficially. When the hip was in a flexed position there was a mean three-fold reduction in distal movement. In people with diabetes mellitus there was significantly less distal movement of the tibial nerve in the neutral hip position and less superficial movement of the nerve in both hip positions compared to healthy individuals. InterpretationWe have documented reductions in tibial nerve excursion due to limb pre-positioning thought to pre-load the nervous system using a non-invasive methodology. Thus, lower limb pre-positioning impacts nerve biomechanics during ankle motions common in functional activities. Additionally, our findings indicate that nerve biomechanics have the potential to be altered in older individuals with diabetes mellitus compared to younger healthy individuals.

Repeatability of measuring sciatic nerve excursion during a modified passive straight leg raise test with ultrasound imaging

The purpose of this study was to establish the reliability of a frame-by-frame cross correlation method of assessing longitudinal sciatic nerve excursion motion using real time ultrasound imaging during a modified passive straight leg raise (SLR) test. Eighteen asymptomatic participants (age range 19–68 years) lay on their sides on a purpose made jig and the sciatic nerve in the posterior thigh was imaged during knee extension at 30° and then 60° of hip flexion (HF). Participants were re-tested ≥48 h later. The ultrasound images were analysed off-line using cross correlation software. Results demonstrated excellent repeatability of in vivo sciatic nerve excursion during a modified SLR (HF30° ICC 0.92, CI 0.79–0.97, SEM 0.69; HF60° ICC 0.96, CI 0.89–0.99, SEM 0.87). The authors also identify points of good practise to ensure an accurate as possible measurement of nerve excursion using this method. These include breaking down larger movements into sub-components, visually tracking the moving nerve during the tracking procedure, and ensuring the optimal image is captured prior to analysis. The use of ultrasound imaging in lower limb nerve dysfunction will enhance the understanding of how nerves move in vivo during neurodynamic testing, as well as being able to identify possible alteration to nerve movements in patients with neuropathic pain states.

Comparison of Longitudinal Sciatic Nerve Movement With Different Mobilization Exercises: An In Vivo Study Utilizing Ultrasound Imaging

Controlled laboratory study using a single-group, within-subjects comparison. To determine whether different types of neural mobilization exercises are associated with differing amounts of longitudinal sciatic nerve excursion measured in vivo at the posterior midthigh region. Recent research focusing on the upper limb of healthy subjects has shown that nerve excursion differs significantly between different types of neural mobilization exercises. This has not been examined in the lower limb. It is important to initially examine the influence of neural mobilization on peripheral nerve excursion in healthy people to identify peripheral nerve excursion impairments under conditions in which nerve excursion may be compromised. High-resolution ultrasound imaging was used to assess sciatic nerve excursion at the posterior midthigh region. Four different neural mobilization exercises were performed in 31 healthy participants. These neural mobilization exercises used combinations of knee extension and cervical spine flexion and extension. Frame-by-frame cross-correlation analysis of the ultrasound images was used to calculate nerve excursion. A repeated-measures analysis of variance and isolated means comparisons were used for data analysis. Different neural mobilization exercises induced significantly different amounts of sciatic nerve excursion at the posterior midthigh region (P<.001). The slider exercise, consisting of the participant performing simultaneous cervical spine and knee extension, resulted in the largest amount of sciatic nerve excursion (mean ± SD, 3.2 ± 2.0 mm). The amount of excursion during the slider exercise was slightly greater (mean ± SD, 2.6 ± 1.5 mm; P = .002) than it was during the tensioner exercise (simultaneous cervical spine flexion and knee extension). The single-joint neck flexion exercise resulted in the least amount of sciatic nerve excursion at the posterior midthigh (mean ± SD, -0.1 ± 0.1 mm), which was significantly smaller than the other 3 exercises (P<.001). These findings are consistent with the results of previous research that has examined median nerve excursion associated with different neural mobilization exercises. Such nerve excursion supports theories of nerve motion associated with cervical spine and extremity movement, as generalizable to the lower limb.

Laxity of the Ulnar Nerve During Elbow Flexion and Extension

To evaluate the dynamic anatomy of the ulnar nerve at the elbow. We studied 11 fresh cadavers. We placed metal clips on the ulnar nerve at three locations: at the medial epicondyle (point A), 3 cm proximal to the epicondyle (point B), and 14 cm proximal to the epicondyle (point C). The distances from the medial epicondyle to points A, B, and C on the ulnar nerve and between each pair of points were measured in full elbow extension and flexion. With full elbow flexion, there was no movement of the ulnar nerve at point A (adjacent to the medial epicondyle). Point A and the adjacent distal ulnar nerve moved as a unit with the forearm around the medial epicondyle. Proximal to the cubital tunnel, there was significant ulnar nerve excursion (P < .01) at points B (0.7 ± 0.3 cm) and C (0.2 ± 0.2 cm). There was differential excursion of the ulnar nerve at points B and C relative to the medial epicondyle. The distances between the markers revealed that the nerve did not stretch to account for the discrepant distances of the 3 points, but a slack region of the nerve proximal to the medial epicondyle was taken up with flexion. Release of the intermuscular septum and the canal of Struthers did not influence movement of the nerve. With elbow flexion, the ulnar nerve did not move appreciably in the distal-proximal direction directly at the cubital tunnel, but maximal excursion was in the fatty region proximal to the elbow. This slack region of the nerve was taken up during flexion, whereas only 2 mm of motion occurred through the canal of Struthers. The slack region might predispose to subluxation of the nerve. Conversely, decreased laxity might result in increased traction of the nerve, contributing to cubital tunnel syndrome. Therapeutic II.

Measurement of tibial nerve excursion during ankle joint dorsiflexion in a weight‐bearing position with ultrasound imaging

BackgroundThe ability of peripheral nerves to stretch and slide is thought to be of paramount importance to maintain ideal neural function. Excursion in peripheral nerves such as the tibial can be measured by analysis of ultrasound images. The aim of this study was to assess the degree of longitudinal tibial nerve excursion as the ankle moved from plantar flexion to dorsiflexion in a standardised weight-bearing position. The reliability of ultrasound imaging to measure tibial nerve excursion was also quantified.MethodsThe tibial nerve was imaged over two separate sessions in sixteen asymptomatic participants in a weight-bearing position. Longitudinal nerve excursion was calculated from a three-second video loop captured by ultrasound imaging using frame-by-frame cross-correlation analysis. Intraclass correlation coefficients (ICC) with 95% confidence intervals (CI) were used to assess the intra-rater reliability. Standard error of the measurement (SEM) and smallest real difference (SRD) were calculated to assess measurement error.ResultsMean nerve excursion was 2.99 mm SEM ± 0.22 mm. The SRD was 0.84 mm for session 1 and 0.66 mm for session 2. Intra-rater reliability was excellent with an ICC = 0.93.ConclusionsAssessment of real-time ultrasound images of the tibial nerve via frame-by-frame cross-correlation analysis is a reliable non-invasive technique to assess longitudinal nerve excursion. The relationship between foot posture and nerve excursion can be further investigated.

Measurement of longitudinal tibial nerve excursion during ankle joint dorsiflexion: an in‐vivo investigation with ultrasound imaging

Background A key mechanical function of peripheral nerves is their ability to slide in relation to the surrounding tissues. This function is of paramount importance to maintain ideal neural function [1]. Advances in ultrasound imaging and the development of specific software (crosscorrelation analysis) have made it possible to analyse real-time ultrasound images, allowing for quantification of in-vivo peripheral nerve movement [2]. Cross-correlation analysis has been utilised in numerous upper extremity in-vivo neural investigations [3-5]. No study has investigated in-vivo longitudinal nerve excursion at the ankle joint. The aims of this study were to quantify the degree of longitudinal tibial nerve excursion as the ankle moved from dorsiflexion to plantarflexion and assess the between session intra-rater reliability of the ultrasound imaging technique.

Scientific study of the extent of transverse movement of the median nerve at the wrist during active wrist extension in static positions of the upper limb tension test one

Objective. Longitudinal glide of the median nerve is affected in typical entrapment neuropathies such as carpal tunnel syndrome. The upper limb tension test one (ULTT1) is used by clinicians to assess patients’ responses to passive movements that affect the median nerve. ULTT1 is thought to mainly assess the longitudinal glide of the median nerve; however, transverse glide of the nerve at the wrist may be a more sensitive measure of an entrapment neuropathy. Method. Sixteen wrists of four male and 11 female healthy volunteers were studied with ultrasound imaging in this small original study. Images were collected in eight different combinations of shoulder, elbow and forearm posture. In each posture the wrist was moved from full flexion to 30° of extension. Results Nerve excursion from full wrist flexion to 30° of extension was mainly in a radio-dorsal direction. It ranged from a minimum of 1.8 mm (SD ± 2.0 mm) up to 3.57 mm (SD ± 1.86 mm) of transverse movement, and 0.22 mm (SD ± 0.59 mm) of volar movement to 0.96 mm (SD ± 0.76 mm) of dorsal movement. In all eight of the positions tested, forearm supination led to greater transverse movement of the nerve at the wrist. Conclusions Transverse movement of the median nerve is most marked with forearm supination, irrespective of other changes in the kinetic chain. The nerve moves dorsally in all movements except when the forearm flexors are off-loaded in elbow extension and elbow flexion. These findings confirm the transverse movement of the median nerve at the wrist, during active wrist extension within positions of the ULTT, but that the shoulder and elbow position have little impact on the degree of movement.

Tendon and nerve excursion in the carpal tunnel in healthy and CTD wrists

BackgroundDuring hand and finger motions, friction between flexor digitorum superficialis tendon and the median nerve is thought to play a role in the development of cumulative trauma disorders. This study investigated three methods to determine excursions of the flexor digitorum superficialis tendon and median nerve using several motions. MethodsTwenty-five participants (mean age 37.2years SD 13.4) were classified as healthy (n=16), self-reported distal upper extremity cumulative trauma disorders (6), or wheelchair users (3). Static carpal tunnel measurements were taken and displacements of the index flexor digitorum superficialis tendon and median nerve were determined via the velocity time integral and post hoc integration of the Doppler ultrasound waveform using a 12–5MHz linear array transducer, as well as using predictive equations. FindingsMedian nerves in symptomatic wrists were larger than healthy wrists by 4.2mm2 (left) and 4.1mm2 (right) proximally to less than 1.4mm2 distally. In healthy wrists, left–right tendon excursion differences ranged from 0.7mm to 4.3mm depending on the motion while left to right differences in symptomatic wrists ranged over 22.2mm. Ultrasound measures of tendon excursion overestimated those determined using predictive equations and were poorly correlated.The ratio of median nerve excursion to tendon excursion was lower in finger only motions compared to wrist motions with or without finger motion. InterpretationSpectral Doppler ultrasound imaging provided insights into tendon excursion that was not apparent with mathematical modeling. The difference in excursion between finger motions and wrist motions could be beneficial in therapeutic techniques.

Suprascapular Neuropathy

Suprascapular neuropathy is a relatively uncommon but significant cause of shoulder pain and dysfunction. The suprascapular nerve follows a tortuous course from the neck to the posterior shoulder. There are several potential causes of nerve entrapment along this path, particularly at the vulnerable suprascapular and spinoglenoid notches, where nerve excursion is limited by bony and ligamentous constraints. Additional extrinsic compression may be caused by glenohumeral joint-related ganglion cysts or soft-tissue masses. Traction neuropathy may occur following excessive nerve excursion during overhead sports or as a result of massive, retracted rotator cuff tears in older patients. Diagnosis is based on a careful history, physical examination, focused imaging, and electrodiagnostic studies. In the absence of a clear structural compression or overtensioning of the nerve, treatment initially should be nonsurgical, with activity modification and physical therapy. Discrete nerve compression or failure of nonsurgical measures warrants early surgical intervention. Arthroscopic alternatives to the traditional open suprascapular and/or spinoglenoid notch decompressions have the benefit of simultaneously diagnosing and addressing intra-articular and/or subacromial pathology while minimizing morbidity. In most patients, both open and arthroscopic approaches provide reliable pain relief and improvements in function; return of strength and muscle bulk is less predictable.

Different Nerve-Gliding Exercises Induce Different Magnitudes of Median Nerve Longitudinal Excursion: An In Vivo Study Using Dynamic Ultrasound Imaging

Controlled laboratory study using single-group, within-subject comparisons. To determine in an in vivo study whether different types of nerve-gliding exercises are associated with different amounts of longitudinal nerve excursion. Different types of nerve-gliding exercises have been proposed. It is assumed that different exercises produce different amounts of excursion and strain in the peripheral nervous system. Although this has been confirmed in cadaveric experiments, in vivo studies are lacking. High-resolution ultrasound was used to measure longitudinal excursion of the median nerve in the upper arm during 6 different nerve-gliding exercises. Nerve mobilization techniques that involved the elbow and neck were evaluated in 15 asymptomatic volunteers (mean +/- SD age, 30 +/- 8 years). Nerve longitudinal excursion was calculated using a frame-by-frame cross-correlation analysis. A repeated-measures analysis of variance was used to analyze the data. Different exercises induced different amounts of longitudinal nerve excursion (P<.0001). The "sliding technique" was associated with the largest excursion (mean +/- SD, 10.2 +/- 2.8 mm; P = .0001). The amount of nerve movement associated with the "tensioning technique" (mean +/- SD, 1.8 +/- 4.0 mm) was smaller than the nerve excursion induced with individual movements of the neck or elbow (mean +/- SD range, -3.4 +/- 0.9 to 5.6 +/- 2.1 mm; P = .0001). These findings confirm that different types of neurodynamic techniques have different mechanical effects on the nervous system. Recognition of these differences may assist in the selection of treatment techniques. Having demonstrated differences in mechanical effects, future research will have to evaluate whether these different techniques are also associated with different physiological and therapeutic effects.

Median Nerve Excursion in Response to Wrist Movement After Endoscopic and Open Carpal Tunnel Release

To compare the perioperative kinematic effects of endoscopic versus open carpal tunnel release on longitudinal excursion (gliding) and volar displacement (bowstringing) of the median nerve at the wrist region in patients with idiopathic primary carpal tunnel syndrome. Sixteen hands of 13 patients were randomly assigned into 2 groups (group 1, endoscopic; group 2, open carpal tunnel release). For the measurement of gliding and bowstringing of the median nerve, a metallic marker was used. Before and after the division of the transverse carpal ligament, longitudinal excursion and volar displacement of the median nerve were calculated based on fluoroscopic imaging for each wrist. Movement was analyzed for the measurement of the marker locations. The mean prerelease median nerve excursion during wrist range of motion was 20 mm (range, 10-28) in group 1 and 21 mm (range, 16-31 mm) in group 2. The mean postrelease median nerve excursion during wrist range of motion was 20 mm (range, 13-29) in group 1 and 18 mm (range, 8-26 mm) in group 2. There was no statistically significant difference in pre- and postrelease longitudinal excursion changes between the groups (p = .916 and p = .674, respectively). The mean prerelease volar displacement of the median nerve during wrist range of motion was 3 mm in group 1 and 4 mm in group 2; the postrelease mean values were 2 mm and 5 mm, respectively. There was no statistically significant difference between the groups with regard to pre- and postrelease volar displacement changes of the median nerve (p = .372 and p = .103, respectively). This study demonstrated that the endoscopic release and open carpal tunnel release produce similar perioperative effects on longitudinal and volar movements of the median nerve.

Excursion and Strain of the Superficial Peroneal Nerve During Inversion Ankle Sprain

Traction is presumed to be the mechanism of injury to the superficial peroneal nerve in an inversion ankle sprain, but it is not known whether the amount of strain caused by nerve traction is sufficient to cause nerve injury. We hypothesized that the superficial peroneal nerve would experience significant excursion and strain during a simulated inversion sprain, that sectioning of the anterior talofibular ligament would increase excursion and strain, and that an impact force would produce strain in a range that can structurally alter the nerve. Differential reluctance transducers were placed in the superficial peroneal nerve in sixteen lower-extremity cadaver specimens to measure excursion and strain in situ. Static weight was applied to the foot in increments starting at 0.454 kg and ending at 4.54 kg. The anterior talofibular ligament was sectioned, and the measurements were repeated. A final impact force of 4.54 kg was applied to each specimen. Two-way repeated-measures analysis of variance was used to evaluate differences in excursion and strain. The mean excursion and strain of the superficial peroneal nerve increased with increases in the applied weight in both the group with the intact anterior talofibular ligament and the group in which it had been sectioned. Nerve excursion was greater in the sectioned-ligament group than in the intact-ligament group with all applied weights (p < 0.05). The mean nerve strain was greater in the sectioned-ligament group (range, 5.5% to 12.9%) than in the intact-ligament group (range, 3.0% to 11.6%) with application of the 0.454, 0.908, 1.362, and 1.816-kg weights (p < 0.05). With the ligament sectioned, the 4.54-kg impact force produced significantly higher mean nerve excursion and strain than did the 4.54-kg static weight (p < 0.05). The magnitude of strain with the impact force was in the lower range of values that have been shown to structurally alter peripheral nerves. The superficial peroneal nerve is at risk for traction injury during an ankle inversion sprain and is at additional risk with more severe sprains or with an insufficient anterior talofibular ligament.

Reduced Longitudinal Excursion of the Median Nerve in Carpal Tunnel Syndrome

Hough AD, Moore AP, Jones MP. Reduced longitudinal excursion of the median nerve in carpal tunnel syndrome. Objective To determine if longitudinal excursion of the median nerve is reduced in patients with carpal tunnel syndrome (CTS). Design Case-control study. Setting University human movement laboratory. Participants Nineteen patients with CTS (8 men, 11 women; mean age, 57±15y), and 37 healthy controls (8 men, 29 women; mean age, 48±10y). Interventions Not applicable. Main Outcome Measures Longitudinal excursion of the median nerve, and the ratio of nerve to flexor digitorum superficialis tendon excursion at the carpal tunnel evoked by finger extension. Measurements were taken using a validated Doppler ultrasound technique, and tests were conducted with the elbow positioned in extension and flexion. Results Mean longitudinal excursion of the median nerve was significantly greater in controls (11.2±2.8mm) than patients (8.3±2.6mm) with the elbow extended ( P=.013), but not with the elbow flexed (controls, 12.5±2.5mm; patients, 10.2±3.1mm; P=.089). Mean nerve/tendon excursion ratios were significantly greater in controls (.32±.07) than patients (.23±.06), with the elbow extended ( P<.001), and flexed (controls, .36±.06; patients, .28±.10; P=.019). Discriminant analysis identified that 11 (58%) of the 19 patients and 3 (8%) of the 37 controls showed a nerve/tendon excursion ratio of .25 or less when tested with the elbow in extension. Conclusions Reduced longitudinal excursion of the median nerve at the carpal tunnel was identified in a substantial proportion of patients with CTS. Further studies are merited to determine if reduced median nerve excursion at the carpal tunnel is clinically relevant in CTS, and can be influenced by movement-based interventions.

Workshop: Clinical implications for clinicians treating patients with non-specific arm pain, whiplash and carpal tunnel syndrome

Nerve sheath inflammation without significant axonal degeneration can result in c fibres (both axons in continuity and the nervi nervorum) becoming spontaneously active and mechanically sensitive. This may help explain the painful responses when examining neural dynamics in patients with non specific arm pain, carpal tunnel syndrome and arm pain following whiplash injury, when longitudinal nerve excursion (measured using ultrasound imaging), appears to be within normal ranges. These findings have implications for the clinical examination and treatment of these patients groups.

Structure and Biomechanics of Peripheral Nerves: Nerve Responses to Physical Stresses and Implications for Physical Therapist Practice

The structural organization of peripheral nerves enables them to function while tolerating and adapting to stresses placed upon them by postures and movements of the trunk, head, and limbs. They are exposed to combinations of tensile, shear, and compressive stresses that result in nerve excursion, strain, and transverse contraction. The purpose of this appraisal is to review the structural and biomechanical modifications seen in peripheral nerves exposed to various levels of physical stress. We have followed the primary tenet of the Physical Stress Theory presented by Mueller and Maluf (2002), specifically, that the level of physical stress placed upon biological tissue determines the adaptive response of the tissue. A thorough understanding of the biomechanical properties of normal and injured nerves and the stresses placed upon them in daily activities will help guide physical therapists in making diagnoses and decisions regarding interventions.