Transverse sliding of the median nerve beneath the flexor retinaculum

Ultrasonographical Evaluation of the Median Nerve Mobility in Carpal Tunnel Syndrome: A Systematic Review and Meta-Analysis

Diagnostic ultrasound is widely used for evaluating carpal tunnel syndrome (CTS), an entrapment neuropathy of the median nerve (MN). Decreased mobility of the MN inside the carpal tunnel has been reported in CTS, and various methods have been used to evaluate MN mobility; however, there is still no conclusive understanding of its connection with CTS. The purpose of this study is to conduct a systematic review and meta-analysis of the current published literature on ultrasonographic evaluations of transverse and longitudinal MN displacement and to identify the relationship between MN mobility and CTS. This study was conducted in accordance with the 2020 PRISMA statement and the Cochrane Collaboration Handbook. Comparative studies that investigated differences in MN displacement between CTS patients and healthy controls were retrieved by searching the Cochrane Library, Embase and PubMed. A total of 15 case–control studies were included. Nine of 12 studies evaluating transverse MN displacement and 4 of 5 studies evaluating longitudinal MN gliding showed that the MN was less mobile in CTS patients than in healthy subjects. Despite the large heterogeneity among the 15 included studies, this systematic review and meta-analysis provide evidence that the mobility of the MN is significantly reduced in both transverse and longitudinal planes in CTS patients compared to healthy controls. Five of the 15 included studies reported that a decrease in transverse or longitudinal MN displacement in CTS was correlated with clinical symptoms or with severity as measured by a nerve conduction study (NCS).

Novel Motor-Sparing Ultrasound-Guided Neural Injection in Severe Carpal Tunnel Syndrome: A Comparison of Four Injectates

Nerve hydrodissection uses fluid injection under pressure to selectively separate nerves from areas of suspected entrapment; this procedure is increasingly viewed as potentially useful in treating carpal tunnel syndrome (CTS). The usage of normal saline (NS), 5% dextrose water (D5W), platelet-rich plasma (PRP), and hyaluronic acid (HA) as primary injectates for hydrodissection without an anesthetic can limit anesthetic-related toxicity and preserve the motor functions of the median nerve. Here, we describe a novel motor-sparing neural injection and compare the effect of these four injectates for severe CTS. We retrospectively reviewed the outcomes of 61 severe CTS cases after a single neural injection with NS, D5W, PRP, or HA. Outcomes were evaluated on the 1st and 6th months postinjection, including the Boston Carpal Tunnel Questionnaire (BCTQ) scores and the nerve cross-sectional area (CSA). The results revealed that PRP, D5W, and HA were more efficient than NS at all measured time points ( $p<0.05$ ), except for CSA at the 1st month between the NS and D5W groups. Single-injections of PRP and D5W seemed more effective than that of HA within 6 months postinjection for symptom and functional improvement (6th-month BCTQ-symptom, D5W vs. HA, $p=0.047$ ; 1st-month BCTQ-symptom, PRP vs. HA, $p=0.018$ ; 1st- and 6th-month BCTQ-function, D5W vs. HA, $p=0.002$ and 0.016, respectively; 1st-month BCTQ-function, PRP vs. HA, $p<0.001$ ). For reducing CSA, PRP and HA seemed more effective than D5W ( $\text{HA}>\text{PRP}>\text{D}5\text{W}$ on the 1st month and HA vs. D5W, $p=0.001$ ; $\text{PRP}>\text{HA}>\text{D}5\text{W}$ on the 6th month and PRP vs. D5W, $p=0.012$ ).

The Morphological and Dynamic Changes of Ultrasound in the Evaluation of Effects of Oral Steroids Treatment for Patients with Carpal Tunnel Syndrome

The role of oral steroids in carpal tunnel syndrome (CTS) remains elusive. This study aims to depict the ultrasound findings and conceivable mechanisms in relation to the efficacy of oral steroids for patients with CTS by measuring the morphological and motion changes in the median nerve. In this study, CTS patients were randomized to the oral steroid group (14 participants and 22 wrists) or nicergoline group (22 participants and 35 wrists) for 4 weeks. Both treatment arms were given global symptom score (GSS) measurements and completed an ultra-sound at baseline and at 2- and 4-weeks post-treatment. In the nerve conduction study (NCS), distal motor latency (DML) was used to assess the treatment response at baseline and 4 weeks post-treatment. The cross-sectional area (CSA) and amplitude (AMP) evaluated by the maximum lateral sliding displacement represented the morphological and dynamic changes in the median nerve, respectively. The results showed that AMP, CSA, GSS, and DML were significantly im-proved in the steroid group, as compared to the nicergoline group at weeks 2 and 4 (p < 0.05). The mean improvement in ultrasound parameters CSA (15.03% reduction) and AMP (466.09% increase) was better than the DML (7.88% reduction) parameter of NCS, and ultrasound changes were detectable as early as 2 weeks after oral steroid administration. Ultrasounds can serve as a tool for the quantitative measurement of treatment effects and can potentially elucidate the pathogenesis of CTS in a non-invasive and more effective manner.

Quantitative stiffness of the median nerve, flexor tendons, and flexor retinaculum in the carpal tunnel measured with acoustic radiation force impulse elastography in various wrist and finger positions

Despite the high prevalence and clinical importance of soft-tissue disorders, objective methods for evaluation of the biomechanical properties of soft tissues are lacking. This study aimed to quantitatively evaluate stiffness, an important biomechanical characteristic of soft tissue, using acoustic radiation force impulse (ARFI) elastography. The shear wave velocity (SWV, m/s) values of soft tissue structures within the carpal tunnel (CT) were measured in various combinations of wrist and finger positions.Twenty-six healthy adults were enrolled in this study. We measured the cross-sectional area of the median nerve (MN) and the SWV values of several structures within the CT at the CT inlet level. Measurement of SWV of the MN, flexor digitorum superficialis (FDS), flexor digitorum profundus (FDP), and transverse carpal ligament (TCL) were conducted in six wrist/finger motion combinations.When the wrist and fingers were in neutral positions (position A), the mean SWV was lowest for the MN (mean ± standard deviation, 2.3 ± 0.5 m/s), followed by the FDS (2.9 ± 0.2), FDP (3.2 ± 0.3), and TCL (3.3 ± 0.4). The SWV was significantly different among the six different wrist/finger positions for all structures (P < .001). However, the MN cross-sectional area was not significantly different (P = .527). The SWV values for the MN, FDS, and FDP increased significantly as the wrist/finger positions the stress on the tendons increased (from position B to F) compared with a neutral position, while the SWV of the TCL was significantly higher for in all positions compared with neutral, except for wrist neutral, finger extension. The SWV values for the MN, FDS, and TCL gradually increased as stress increased.The intra-CT structures are under increased stress during wrist and finger motions than when the hand is in a neutral position. We have used ARFI elastography to gain insight into the pathophysiology of CTS.

The influence of wrist posture, grip type, and grip force on median nerve shape and cross-sectional area

During grasping, the median nerve undergoes mechanical stress in the carpal tunnel which may contribute to carpal tunnel syndrome. This study investigated the effects of wrist posture, grip type, and grip force on the shape and cross-sectional area of the median nerve. Ultrasound examination was used to obtain cross-sectional images of the dominant wrist of 16 healthy subjects (8 male) at the proximal carpal tunnel during grasping. The cross-sectional area, circularity, and axis lengths of the median nerve were assessed in 27 different conditions (3 postures × 3 grip types × 3 force levels). There were no significant changes in median nerve cross-sectional area (P > 0.05). There were significant interactions across posture, grip type, and grip force affecting nerve circularity and axis lengths. When the wrist was flexed, increasing grip force caused the median nerve to shorten in the mediolateral direction and lengthen in the anteroposterior direction (P < 0.04), becoming more circular. These effects were significant during four finger pinch grip and chuck grip (P < 0.05) but not key grip (P > 0.07). With the wrist extended, the nerve became more flattened (less circular) as grip force increased during four finger pinch grip and chuck grip (P < 0.04) but not key grip (P > 0.3). Circularity was lower during the four finger pinch compared to chuck or key grip (P < 0.03). The findings suggest that grip type and wrist posture significantly alter the shape of the median nerve. Clin. Anat. 30:470-478, 2017. © 2017 Wiley Periodicals, Inc.

Ultrasound of the Carpal Tunnel and Median Nerve

The authors describe a protocol for measuring the carpal tunnel and median nerve in a reproducible manner using ultrasound, as well as the variability of ultrasound measurements of the median nerve in the carpal tunnel on repeated testing. Measurements of the median nerve in the wrist and carpal tunnel and measurements of the carpal tunnel were taken on 23 wrists using high-resolution ultrasound following a specified protocol. These measurements were repeated a short time later to enable the initial measurements to be tested for reproducibility and stability. The same person obtained all measurements for the purposes of this study; thus, the results represent findings in an intraobserver variability study. Good correlation between the test and retest measurements was demonstrated, with r2 values between 0.72 and 0.98. Paired t test demonstrated no significant difference between the test and retest measurements. The study shows that repeated ultrasound measurements of the cross-sectional areas of the carpal tunnel, median nerve at the proximal edge of the carpal tunnel, distal to the carpal tunnel and at the level of the proximal wrist crease can all be satisfactorily reproduced when a strict ultrasound protocol is adhered to.

Assessment of Median Nerve Mobility by Ultrasound Dynamic Imaging for Diagnosing Carpal Tunnel Syndrome

Carpal tunnel syndrome (CTS) is the most common peripheral neuropathy and is characterized by median nerve entrapment at the wrist and the resulting median nerve dysfunction. CTS is diagnosed clinically as the gold standard and confirmed with nerve conduction studies (NCS). Complementing NCS, ultrasound imaging could provide additional anatomical information on pathological and motion changes of the median nerve. The purpose of this study was to estimate the transverse sliding patterns of the median nerve during finger movements by analyzing ultrasound dynamic images to distinguish between normal subjects and CTS patients. Transverse ultrasound images were acquired, and a speckle-tracking algorithm was used to determine the lateral displacements of the median nerve in radial-ulnar plane in B-mode images utilizing the multilevel block-sum pyramid algorithm and averaging. All of the averaged lateral displacements at separate acquisition times within a single flexion–extension cycle were accumulated to obtain the cumulative lateral displacements, which were curve-fitted with a second-order polynomial function. The fitted curve was regarded as the transverse sliding pattern of the median nerve. The R² value, curvature, and amplitude of the fitted curves were computed to evaluate the goodness, variation and maximum value of the fit, respectively. Box plots, the receiver operating characteristic (ROC) curve, and a fuzzy c-means clustering algorithm were utilized for statistical analysis. The transverse sliding of the median nerve during finger movements was greater and had a steeper fitted curve in the normal subjects than in the patients with mild or severe CTS. The temporal changes in transverse sliding of the median nerve within the carpal tunnel were found to be correlated with the presence of CTS and its severity. The representative transverse sliding patterns of the median nerve during finger movements were demonstrated to be useful for quantitatively estimating median nerve dysfunction in CTS patients.

Biphasic motion of the median nerve in the normal Asian population

BACKGROUND

The biomechanical interaction between the median nerve and the flexor tendons is an important consideration in Carpal tunnel syndrome (CTS). We aim to quantify the displacement and compressive deformation pattern of the median nerve in various stages of finger flexion in the normal population at the inlet of the carpal tunnel.

METHODS

Transverse ultrasounds images were taken at the carpal tunnel inlet during full-extension, mid-flexion and full flexion. The displacement, distance, Feret's diameter, and perimeter of the median nerve were calculated and compared between each position.

RESULTS

Biphasic median nerve motion was observed, with a displacement of 2.84 ± 3.49 mm in the ulnar direction from full-extension to mid-flexion (Phase I) and a further 0.93 ± 3.04 mm from mid-flexion to full flexion (Phase II). Of 49 hands, 37 (75.5%) exhibited ulnar displacement in Phase I while 12 (24.5%) exhibited radial displacement. Feret's diameter (5.95 ± 1.08 mm) and perimeter (13.28 ± 2.09) of the median nerve were greatest in the mid-flexed position.

CONCLUSION

In a healthy Asian population, the median nerve has a biphasic motion during finger flexion, with maximal deformation in the mid-flexed position.

Carpal tunnel syndrome: US strain imaging for diagnosis

PURPOSE

To determine the feasibility of two-dimensional (2D) ultrasonographic (US) strain imaging for quantifying and mapping mechanical behaviors of the median nerve, flexor retinaculum, and flexor tendons within the carpal tunnel in normal and carpal tunnel syndrome (CTS) disease states during active finger motion.

MATERIALS AND METHODS

This prospective study was approved by the institutional review board; all subjects gave written informed consent and had both of their hands examined. Ten wrists in 10 healthy volunteers (age range, 35-51 years) and 16 wrists in 12 patients with CTS (age range, 37-55 years) were examined. In the patients, CTS had been confirmed on the basis of clinical symptoms and results of electrophysiologic studies. Raw US signals were acquired and were cross correlated to enable estimation of 2D incremental displacements, from which 2D strains were computed. The median nerve was characterized by the axial normal strain, while the flexor tendons and the flexor retinaculum were characterized by the shear strain. Temporal mean values (mean cumulative strain [MCS] values) and standard deviations (standard deviations of the cumulative strain [SDCS]) of the spatially averaged cumulative strains in each tissue region over the entire cycle of finger motion were compared by using an unpaired two-tailed Student t test.

RESULTS

MCS for patients with CTS and volunteers was similar. The SDCS for the shear strain of the flexor retinaculum was significantly lower (P < .001) in patients with CTS than in healthy volunteers, while that for the axial strain of the median nerve was higher in healthy volunteers than in patients with CTS (P = .0065).

CONCLUSION

US strain imaging can be used to quantify and map tissue kinematics in the carpal tunnel and to differentiate abnormal from normal median nerves in the wrist.

Comparison of the effects of flexion and extension of the thumb and fingers on the position and cross-sectional area of the median nerve

Objective

To assess the separate effects of thumb and finger extension/flexion on median nerve position and cross-sectional area.

Methods

Ultrasonography was used to assess median nerve transverse position and cross-sectional area within the carpal tunnel at rest and its movement during volitional flexion of the individual digits of the hand. Both wrists of 165 normal subjects (11 men, 4 women, mean age, 28.6, range, 22 to 38) were studied.

Results

Thumb flexion resulted in transverse movement of the median nerve in radial direction (1.2±0.6 mm), whereas flexion of the fingers produced transverse movement in ulnar direction, which was most pronounced during flexion of the index and middle fingers (3.2±0.9 and 3.1±1.0 mm, respectively). Lesser but still statistically significant movements were noted with flexion of the ring finger (2.0±0.8 mm) and little finger (1.2±0.5 mm). Flexion of the thumb or individual fingers did not change median nerve cross-sectional area (8.5±1.1 mm²).

Conclusions

Volitional flexion of the thumb and individual fingers, particularly the index and middle fingers, produced significant transverse movement of the median nerve within the carpal tunnel but did not alter the cross-sectional area of the nerve. The importance of these findings on the understanding of the pathogenesis of the carpal tunnel syndrome and its treatment remains to be investigated.

Ultrasonography of peripheral nerves

Over the last decade, neuromuscular ultrasonography has emerged as a useful tool for the diagnosis of peripheral nerve disorders. This article reviews sonographic findings of normal nerves, including key quantitative ultrasound measurements that are helpful in the evaluation of focal and possibly generalized peripheral neuropathies. It also discusses several recent articles outlining the evidence base for the use of this technology, as well as new findings in compressive, traumatic, and generalized neuropathies. Ultrasonography is well suited for use in electrodiagnostic laboratories, where physicians, experienced in both the clinical evaluation of patients and the application of hands-on technology, can integrate findings from the patient's history, physical examination, electrophysiological studies, and imaging for diagnosis and management.

Interventions in the disturbances in the motor and sensory environment

Treatment of peripheral nervous system (PNS) pathology presents intervention challenges to every therapist. Many of the current and future interventions will be directed at restoring the normal anatomy, function, and biomechanical properties of the PNS, restoring normal neural physiology and ultimately patient function and quality of life. Present interventions use mechanical (movement) or electrical procedures to affect various properties of the peripheral nerve. The purpose of this article was to apply basic science to clinical practice. The pathology and accompanying structural and biomechanical changes in the PNS will be presented in three specific areas commonly encountered in the clinic: nerve injury and laceration; compression neuropathies; and neuropathic pain and neural tension dysfunction. The intent is to address possible interventions exploring the clinical reasoning process that combines basic science and evidence-based best practice. The current lack of literature to support any one intervention requires a strong foundation and understanding of the PNSs' structure and function to refine current and develop new intervention strategies. Current evidence will be presented and linked with future considerations for intervention and research. During this interlude of development and refinement, best practice will rely on sound clinical reasoning skills that incorporate basic science to achieve a successful outcome when treating these challenging patients.

Transverse plane tendon and median nerve motion in the carpal tunnel: ultrasound comparison of carpal tunnel syndrome patients and healthy volunteers

Background

The median nerve and flexor tendons are known to translate transversely in the carpal tunnel. The purpose of this study was to investigate these motions in differential finger motion using ultrasound, and to compare them in healthy people and carpal tunnel syndrome patients.

Methods

Transverse ultrasounds clips were taken during fist, index finger, middle finger and thumb flexion in 29 healthy normal subjects and 29 CTS patients. Displacement in palmar-dorsal and radial-ulnar direction was calculated using Analyze software. Additionally, the distance between the median nerve and the tendons was calculated.

Results

We found a changed motion pattern of the median nerve in middle finger, index finger and thumb motion between normal subjects and CTS patients (p<0.05). Also, we found a changed motion direction in CTS patients of the FDS III tendon in fist and middle finger motion, and of the FDS II and flexor pollicis longus tendon in index finger and thumb motion, respectively (p<0.05). The distance between the median nerve and the FDS II or FPL tendon is significantly greater in patients than in healthy volunteers for index finger and thumb motion, respectively (p<0.05).

Conclusion

Our results suggest a changed motion pattern of the median nerve and several tendons in carpal tunnel syndrome patients compared to normal subjects. Such motion patterns may be useful in distinguishing affected from unaffected individuals, and in studies of the pathomechanics of carpal tunnel syndrome.

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

BACKGROUND

During 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.

METHODS

Twenty-five participants (mean age 37.2 years 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 12-5 MHz linear array transducer, as well as using predictive equations.

FINDINGS

Median nerves in symptomatic wrists were larger than healthy wrists by 4.2 mm(2) (left) and 4.1 mm(2) (right) proximally to less than 1.4 mm(2) distally. In healthy wrists, left-right tendon excursion differences ranged from 0.7 mm to 4.3 mm depending on the motion while left to right differences in symptomatic wrists ranged over 22.2 mm. 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.

INTERPRETATION

Spectral 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.

Median nerve deformation and displacement in the carpal tunnel during index finger and thumb motion

The purpose of this study was to investigate the deformation and displacement of the normal median nerve in the carpal tunnel during index finger and thumb motion, using ultrasound. Thirty wrists from 15 asymptomatic volunteers were evaluated. Cross-sectional images during motion from full extension to flexion of the index finger and thumb were recorded. On the initial and final frames, the median nerve, flexor pollicis longus (FPL), and index finger flexor digitorum superficialis (FDS) tendons were outlined. Coordinate data were recorded and median nerve cross-sectional area, perimeter, aspect ratio of the minimal-enclosing rectangle, and circularity in extension and flexion positions were calculated. During index finger flexion, the tendon moves volarly while the nerve moves radially. With thumb flexion, the tendon moves volarly, but the median nerve moves toward the ulnar side. In both motions, the area and perimeter of the median nerve in flexion were smaller than in extension. Thus, during index finger or thumb flexion, the median nerve in a healthy human subject shifts away from the index finger FDS and FPL tendons while being compressed between the tendons and the flexor retinaculum in the carpal tunnel. We are planning to compare these data with measurements in patients with carpal tunnel syndrome (CTS) and believe that these parameters may be useful tools for the assessment of CTS and carpal tunnel mechanics with ultrasound in the future.

Service development and evaluation of a new carpal tunnel syndrome education class

Introduction

A carpal tunnel syndrome (CTS) education class was developed to enhance both patient care and the treatment pathway. In order to determine the efficiency and efficacy of the management of patients with CTS within a class setting, the results were assessed and reviewed over a one-year period.

Methods

Patients referred to Guys and St Thomas' Hand Therapy Department over a one-year period with CTS were provided with an appointment for the CTS class. All attendees completed an initial assessment form and a 1:1 assessment by a physiotherapist. A computer-based presentation was delivered within the class and patients were provided with prefabricated wrist splints in a neutral position and an education leaflet. Eighty-nine patients were followed up by a telephone call at six weeks and completed a telephone outcome form. A discharge letter was completed and sent to the referrer advising of the patients' outcome with further treatment recommendations if appropriate.

Results

At six-week telephone follow-up, 42 (47%) patients required no further treatment, 37 (42%) patients were recommended for further investigation, and 10 (11%) patients either had or planned to have carpal tunnel decompression.

Discussion

The new CTS class provides an efficient and effective treatment pathway for patients with CTS. It enables a comprehensive assessment and treatment application within the same session and aids early identification of other pathologies that may require intervention or appropriate onward referral.

Dynamics of intracarpal tunnel pressure in patients with carpal tunnel syndrome

PURPOSE

To measure pressure within the carpal tunnel (intracarpal tunnel pressures) in patients with carpal tunnel syndrome and determine the effect of quantified active hand use on both the magnitude and location of peak pressures, before and after division of the transverse carpal ligament.

METHODS

We measured intracarpal tunnel pressures intraoperatively in 12 patients with carpal tunnel syndrome at 5 standardized locations based on the distance between each patient's proximal pisiform and hook of hamate (HH) before endoscopic division of the ligament, using a semiconductor gauge pressure sensor inserted from proximal to distal into the tunnel under fluoroscopic control. At each location, pressure was recorded with fingers extended, fingers flexed, and 50% maximum grip using a grip dynamometer. Additional hand use activities, including maximum key and pulp pinch using a pinch dynamometer, 25% maximum grip, and maximum grip, were performed by a subset of these patients. After ligament division, we measured pressures during the same hand activities at a single location, HH. We analyzed the effect of hand activity, measurement location, and ligament division using repeated measures analysis of variance.

RESULTS

Compared with fingers extended (mean pressure, 56 mm Hg), all pinch and grip activities caused significant increases in pressure at HH, with a mean peak pressure of 1151 mm Hg during maximum grip. After endoscopic release, pressures decreased significantly at HH for all hand activities.

CONCLUSIONS

In patients with carpal tunnel syndrome, intracarpal tunnel pressures during active hand use are substantially greater than previously reported. Peak pressures occur at the HH, where the tunnel is most constricted and the median nerve is most compressed in carpal tunnel syndrome.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Ultrasound assessment of the displacement and deformation of the median nerve in the human carpal tunnel with active finger motion

BACKGROUND

Peripheral nerves are mobile structures, stretching and translating in response to changes in the position of adjuvant anatomic structures. The objective of this study was to develop a novel method to characterize the relative motion and deformation of the median nerve on cross-sectional ultrasound images of the carpal tunnel during active finger motion.

METHODS

Fifteen volunteers without a history of carpal tunnel syndrome or wrist trauma were recruited. An ultrasound scanner and a linear array transducer were used to evaluate the motion of the median nerve and the flexor tendons within the carpal tunnel during motion from full extension to full flexion by the four fingers (fist motion) and by the long finger alone. The displacement of the median nerve relative to the long-finger flexor digitorum superficialis tendon as well as the perimeter, cross-sectional area, circularity, and aspect ratio of a minimum enclosing rectangle of the median nerve were measured. The data were compared between single-digit motion and fist motion and between extension and flexion positions.

RESULTS

The distance between the long-finger flexor digitorum superficialis tendon and the median nerve with isolated long-finger flexion was decreased in the ulnar-radial direction and increased in the palmar-dorsal direction as compared with the distance with four-finger flexion (p < 0.01). Compared with the values with fist motion, the aspect ratio was decreased and the circularity was increased with long-finger motion (p < 0.01).

CONCLUSIONS

This report presents a method with which to assess displacement and deformation of the median nerve on a cross-sectional ultrasound image during different finger motions. This method may be useful to assess pathological changes within the carpal tunnel, and we plan to perform a similar study of patients with carpal tunnel syndrome on the basis of these preliminary data.

The excursion of the median nerve during nerve gliding exercise: an observation with high-resolution ultrasonography

The purpose of this study was to assess the relationship between the positioning of upper extremity and gliding distance of the median nerve during passive and active motion of the wrist and fingers. The longitudinal gliding of the medial nerve in the forearm was measured in 34 healthy subjects by ultrasonographic dynamic images. Those images were analyzed in a cross-correlation algorithm advocated by Dilley et al. (2001). In this experiment, passive extension of the wrist and fingers was applied manually by an examiner in four positions (elbow flexion and extension with forearm pronation, and elbow flexion and extension with forearm supination), two types of active finger motions (Hook and Grasp) were performed by the subjects. The distally oriented median nerve gliding ranged from 1.9 (in elbow extension with forearm pronation) to 3.0mm (in elbow flexion with forearm supination) during passive extension of the wrist and fingers. There was a statistically significant difference in nerve gliding between the positions (p=0.001). During active digital movement, the proximally oriented nerve gliding was observed from 0.8 (in the hook) to 1.3mm (in the grasp). There was a significant difference in nerve gliding between the two ways of active finger motions (p=0.001). On the basis of the data obtained from this study, it is concluded that forearm supination is the preferred position for the passive median nerve gliding exercise because of large distally oriented nerve gliding. The active digital motion with full finger grip may be an effective procedure to produce proximally oriented median nerve gliding.

The effect of wrist position on the relative motion of tendon, nerve, and subsynovial connective tissue within the carpal tunnel in a human cadaver model

The purpose of this study was to measure the effect of wrist position on the relative motion of the middle finger flexor digitorum superficialis (FDS) tendon, subsynovial connective tissue (SSCT), median nerve, and flexor retinaculum during simulated active finger motion. The relative motion of each tissue was measured by fluoroscopy in 10 human cadavers. Measurements were obtained for wrist positions of neutral (0 degree extension), 30 and 60 degrees of flexion, and 30 and 60 degrees of extension. The shear strain index (SSI) was defined as the difference in motion between two tissues (tendon, SSCT, or nerve) divided by tendon excursion, expressed as a percentage. The motion of the tendon, SSCT, and nerve in the 60 degree flexed position was significantly less than the motion in all other wrist positions (p < 0.001). The SSI at 60 degrees of flexion for tendon-SSCT and tendon-nerve were significantly increased compared with all other positions (p < 0.001). Because the SSCT and tendon are physically connected, a decrease in SSCT motion relative to the tendon would increase the shear strain on the SSCT with tendon motion. Thus, this result suggests that the SSCT may be predisposed to shear injury from activity done in 60 degrees of wrist flexion.

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+/-15 y), and 37 healthy controls (8 men, 29 women; mean age, 48+/-10 y).

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+/-2.8 mm) than patients (8.3+/-2.6 mm) with the elbow extended (P=.013), but not with the elbow flexed (controls, 12.5+/-2.5 mm; patients, 10.2+/-3.1 mm; 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.

Preservation of the ulnar bursa within the carpal tunnel: does it improve the outcome of carpal tunnel surgery? A randomized, controlled trial

BACKGROUND

It was hypothesized that preserving a layer of gliding tissue, the parietal layer of the ulnar bursa, between the contents of the carpal tunnel and the soft tissues incised during carpal tunnel surgery might reduce scar pain and improve grip strength and function following open carpal tunnel decompression.

METHODS

Patients consented to randomization to treatment with either preservation of the parietal layer of the ulnar bursa beneath the flexor retinaculum at the time of open carpal tunnel decompression (fifty-seven patients) or division of this gliding layer as part of a standard open carpal tunnel decompression (sixty-one patients). Grip strength was measured, scar pain was rated, and the validated Patient Evaluation Measure questionnaire was used to assess symptoms and disability preoperatively and at eight to nine weeks following the surgery in seventy-seven women and thirty-four men; the remaining seven patients were lost to follow-up.

RESULTS

There was no difference between the groups with respect to age, sex, hand dominance, or side of surgery. Grip strength, scar pain, and the Patient Evaluation Measure score were not significantly different between the two groups, although there was a trend toward a poorer subjective outcome as demonstrated by the questionnaire in the group in which the ulnar bursa within the carpal tunnel had been preserved. Preserving the ulnar bursa within the carpal tunnel did, however, result in a lower prevalence of suspected wound infection or inflammation (p = 0.04).

CONCLUSIONS

In this group of patients, preservation of the ulnar bursa around the median nerve during open carpal tunnel release produced no significant difference in grip strength or self-rated symptoms. We recommend incision of the ulnar bursa during open carpal tunnel decompression to allow complete visualization of the median nerve and carpal tunnel contents.

Pathomechanics of peripheral nerve loading. Evidence in carpal tunnel syndrome

Peripheral nerve injury is a common occurrence, with carpal tunnel syndrome (CTS) receiving the most attention. Nerve dysfunction associated with compression syndromes results from an interruption or localized interference of microvascular function due to structural changes in the nerves or surrounding tissues. This article reviews the physiologic, pathophysiologic, and histologic effects of compressing peripheral nerves in animal models, and then examines the evidence for similar processes in humans using CTS as a model.

Tendon and nerve displacement at the wrist during finger movements

BACKGROUND

Repetitive motion of the hand has been suggested as a major factor of pathogenesis of cumulative trauma disorders (e.g., carpal tunnel syndrome). The purpose of this study was to investigate the 3D displacement of the median nerve and extrinsic finger flexor tendons (flexor digitorum superficialis; flexor digitorum profundus) as a function of flexion/extension of metacarpophalangeal joints of the index and middle fingers.

METHODS

Shim markers were placed on the median nerve, flexor digitorum superficialis, and flexor digitorum profundus tendons at the wrist region of seven cadaveric specimens for the purpose of digitization of tendon and nerve locations. The metacarpophalangeal joint of the index or middle finger was moved from 15 degrees extension to 75 degrees of flexion while the markers were digitized at increments of 15 degrees. Marker displacements were determined in the longitudinal, radial-ulnar, and dorsal-palmar directions.

FINDINGS

Movement of metacarpophalangeal joint of the index or middle finger caused tendon and nerve displacements in the longitudinal, radial-ulnar, and dorsal-palmar directions. The longitudinal displacements of the median nerve and the flexor tendons were linearly correlated with angular movement of the metacarpophalangeal joint. The maximum longitudinal displacements of the flexor digitorum superficialis tendon, flexor digitorum profundus tendon, and median nerve were, on average, 14.7 mm, 11.9 mm, and 3.0 mm, respectively, for the index finger; and 18.4 mm, 14.5 mm, and 4.0 mm, respectively, for the middle finger. The radial-ulnar and dorsal-palmar displacements were irregular and relatively small. The maximum displacements in these transverse directions fell in the range of 1.4-5.1 mm for the median nerve and 1.9-7.3 mm for the flexor tendons.

INTERPRETATIONS

Finger flexor tendons and median nerve move not only concurrently, but also differentially, in all anatomical directions. Tendon and nerve movement during prolonged repetitive hand movement may cause hand disorders such as carpal tunnel syndrome.

The Effect of Low-dose External Beam Radiation on Extraneural Scarring after Peripheral Nerve Surgery in Rats

OBJECTIVE

Scar tissue is an inevitable result of peripheral nerve surgery. A variety of substances have been used to prevent epineurial scarring. In this study, the effect of low-dose radiation therapy on epineurial scarring was investigated.

METHODS

Seventy-eight male Sprague-Dawley rats were studied. A total of 60 rats were subjected to one of three types of surgical procedure on the sciatic nerve, as follows: Procedure 1, external neurolysis (n = 20); Procedure 2, abrasive injury (n = 20); and Procedure 3, anastomosis (n = 20). On the left sciatic nerves, 700 cGy external beam radiation was administered 24 hours after surgery, and the right sciatic nerves served as a control group (surgery only). Eighteen animals without surgical intervention were used to establish the fibrotic effect of radiotherapy on normal nerves. A neurological examination was performed weekly. Six weeks after surgery, the extent of extraneural scarring was examined by gross microdissection by means of a numerical grading scheme and histological analysis. Cellular density and surface measurements of scar tissue were also evaluated.

RESULTS

The dissection around the nerve was easier in rats treated with low-dose radiation compared with the control group. Furthermore, grading scores in both nerve adherence and nerve separability were significantly lower in treated nerves than in the control group (P < or = 0.05). Low-dose radiotherapy decreased the scores of cellular density and surface measurement of scar tissue (P < or = 0.05). In normal nerves, radiotherapy did not produce any fibrotic effects and the density of fibroblasts/fibrocytes was also very low.

CONCLUSION

In the case of surgery or local trauma to peripheral nerve, the use of low-dose radiation therapy may be a safe method of limiting postoperative epineurial scar formation.

Longitudinal sliding of the median nerve in patients with carpal tunnel syndrome

In nerve compression syndromes restricted nerve sliding may lead to increased strain, possibly contributing to symptoms. Ultrasound was used to examine longitudinal median nerve sliding in 17 carpal tunnel syndrome patients and 19 controls during metacarpophalangeal joint movement. Longitudinal movement in the forearm averaged 2.62 mm in controls and was not significantly reduced in carpal tunnel syndrome (CTS) patients (mean=2.20 mm). In contrast, CTS patients had a 40% reduction in transverse nerve movement at the wrist on the most, compared to least, affected side and nerve areas were enlarged by 34%. Normal longitudinal sliding in the patients indicates that nerve strain is not increased and will not contribute to symptoms.

Sonography of peripheral nerves: technique, anatomy, and pathology

Sonography provides a unique method for evaluating peripheral nerves because of its high spatial resolution, its ability to follow structures over long distances in a limb, and its dynamic nature that allows movement of patient and transducer. When combined with the wide availability and relatively low cost, sonography is an excellent modality for peripheral nerve assessment. The authors review the techniques used in assessment of peripheral nerves, the relevant anatomy, and common pathologic processes.

[The distal radius and surrounding soft tissues--ultrasound anatomy and ultrasound pathology in the adult and child]

BACKGROUND

The aim of the study was to evaluate the ultrasonographic anatomy of the distal forearm (i.e. distal radius and surrounding soft tissue) and the typical changes occurring during growth, in adults and children.

MATERIAL AND METHODS

The ultrasonographic anatomy was evaluated in 10 healthy adults aged between 20 and 60 years, and 20 healthy children aged between 2 and 18 years. Particular attention was paid to dynamic examination comparing both limbs, and isolated investigations of functional tendon.

RESULTS

An anatomical description of the tissues of the distal forearm was possible at all ages. During growth, secondary ossification centres and the transitional osteochondral region of the growth plate need particular consideration.

DISCUSSION AND CONCLUSION

Both in children and adults, ultrasonography can provide valuable information in the evaluation of acute trauma, follow-up of fractures and osteosynthesis, suspected osteomyelitis and chronic disorders. In children, special attention must be paid to the development of the epiphyseal region, as reflected by ossification centre, growth plate and articular cartilage.

Sonographic evaluation of the normal hypothenar compartment musculature

PURPOSE

We propose a standardized sonographic examination technique to evaluate the muscles of the hypothenar region and describe their normal sonographic appearance.

METHODS

The hypothenar region was studied with sonography in 20 healthy volunteers using 5-12-MHz linear-array transducers. The assessment included dynamic testing.

RESULTS

All hypothenar muscles could be identified in all subjects and their courses followed entirely. In addition, their function could be assessed by scanning during active and passive movements.

CONCLUSIONS

Knowledge of the normal sonographic anatomy of the hypothenar region is essential for evaluation of pathologic conditions.

The effect of a standard activity on the size of the median nerve as determined by ultrasound visualization

The purpose of this study was to determine whether a standardized hand activity would produce changes in the cross-sectional diameter of the median nerve. Ultrasound measures of proven reliability of the cross-sectional diameter of the median nerve in the wrist were taken. These measures were taken before activity and immediately after the activity, after 5 minutes, and after 10 minutes. The median nerves of 40 normal subjects showed an increase in cross-sectional diameter immediately after hand activity then returned to a size close to the preactivity size within 10 minutes. The cross-sectional area of the carpal canal did not change significantly after the hand activity was performed. Female gender and body mass index over 25 were associated with significantly larger size increases in the median nerve. This preliminary study suggests that ultrasound is sensitive to the effects of activity upon the hand.

Measuring longitudinal nerve motion using ultrasonography

While it is known that peripheral nerves slide longitudinally in response to limb movements, the clinical relevance of this phenomenon remains largely speculative. This technical note introduces a new application for noninvasive measurement of longitudinal movement of peripheral nerves. The rationale for developing the technique is given including a brief overview of nerve motion theories and how these are related to clinical practice. Current ultrasound applications for nerves and tissue motion are outlined and details of the Doppler measurement procedure are described. Limitations of the technique and potential future applications are discussed. Spectral Doppler ultrasound may provide an effective method for noninvasive quantification of longitudinal nerve motion.

The hypothenar fat-pad flap for reconstructive repair after scarring of the median nerve at the wrist joint

Because of the loss of mobility, scarring of the median nerve in the carpal tunnel can lead to chronic pain syndrome of the wrist joint, with reduced sensation, muscular dystrophy and severe limitation of the use of the hand. This syndrome most often appears following open carpal tunnel release. Nine patients with scarring of the median nerve in the carpal tunnel were treated with a hypothenar fat-pad flap. Eight of them showed a significant reduction in pain, with improved sensation, trophism and strength. The procedure is suitable as a salvage procedure for restoring a sliding pathway and for cushioning the median nerve in the presence of recurrent lesions in the carpal tunnel.

Displacement and strain of the median nerve at the wrist

Median nerve displacement and strain in the carpal tunnel region were measured as functions of wrist position and carpal tunnel pressure in 5 cadaver forearms during simulated active finger flexion. The positions of spherical stainless-steel markers embedded within the median nerve and flexor digitorum superficialis of the long finger were measured in 3 dimensions by a radiographic direct linear transformation technique. Each limb was tested in 3 wrist positions (60 degrees extension, neutral, and 60 degrees flexion) and 4 carpal tunnel pressures (0, 30, 60, and 90 mmHg). Carpal tunnel pressure was controlled with a balloon angiocatheter inserted deep to the flexor digitorum profundus. The ratio of median nerve to flexor tendon excursion was linear and was affected by wrist position but not carpal tunnel pressure. Patterns of strain in the median nerve proximal to the flexor retinaculum were different from those of strain within the carpal tunnel. Nerve strains were affected by wrist position, but carpal tunnel pressure had no effect. The hydrostatic pressure effect associated with carpal tunnel syndrome does not appear to influence median nerve kinetics or kinematics for the wrist positions studied.

Changes in the carpal tunnel due to action of the flexor tendons: visualization with magnetic resonance imaging

Successive cross-sectional areas (CSA) of the carpal tunnel were measured with the fingers in both extension and full flexion in 12 healthy volunteers using magnetic resonance imaging. During flexion, lumbrical muscles could be observed to move into the carpal tunnel up to different levels in all volunteers. For each of the volunteers, the level of the hook of hamate was used as the reference level. The mean CSA measured at this level was considerably larger in flexion than in extension: 191 mm2 (SD, +/- 26) and 169 mm2 (SD, +/- 15), respectively (p = .004). In three volunteers, no difference in CSA between extension and flexion was measured at the hamate level, despite the presence of lumbrical muscles, whereas in these same volunteers at levels more distal, the CSA clearly increased during flexion. The mean CSA for extension and flexion distal and just proximal to the smallest level differed significantly, but the absence of expansion was noticed only at the smallest level. Other changes that were frequently observed during flexion were fat compression, flattening and displacement of the median nerve, and pressure on the superficial and deep flexor tendons.

Restricted motion of the median nerve in carpal tunnel syndrome

Motion of the median nerve was compared on an axial ultrasonographic image in the mid-carpal tunnel in 30 wrists of 15 women with bilateral idiopathic carpal tunnel syndrome and 30 wrists of 15 healthy women. During passive flexion and extension of the index finger, the control wrists had transverse sliding of the nerve beneath the flexor retinaculum (1.75 +/- 0.49 mm), which was regarded as a physiological phenomenon. In contrast, the wrists of patients with carpal tunnel syndrome had significantly less sliding (0.37 +/- 0.34 mm; P = 0.0001), which indicates that physiological motion of the nerve is restricted. This decrease in nerve mobility may be of significance in the pathophysiology of carpal tunnel syndrome.

Median nerve displacement through the carpal canal

We determined the direct relationships between wrist position and displacement of the median nerve during active contraction of the flexor tendons at the wrist with an intact, transected transverse carpal ligament (TCL). Nine fresh cadavers were mounted in an apparatus to allow variable wrist position. Excursions of the tendons and displacement of the median nerve were measured by tracking markers with a video camera. Each limb was tested at 0 degree, 30 degrees, and 60 degrees of wrist extension before and after release of the TCL. Excursion of the flexor tendons required for full finger flexion ranged from 2.3 to 3.1 cm (mean, 3 cm). Median nerve displacement ranged from 0.9 to 1.4 cm (mean, 1 cm). The relationship between median nerve and flexor tendon excursion was consistently linear. Finger motion alone allows for median nerve displacement after surgery in the carpal tunnel.