Finger position alters the median nerve properties within the carpal tunnel: a pre-post MRI comparison study

Efficacy of splinting the wrist and metacarpophalangeal joints for the treatment of Carpal tunnel syndrome: an assessor-blinded randomised controlled trial

OBJECTIVES

To compare the efficacy of a traditional cock-up splint, which supports the wrist only, with a modified splint that supports the wrist and the metacarpophalangeal (MCP) joints of the medial four digits in the treatment of carpal tunnel syndrome (CTS).

DESIGN

An assessor-blind randomised controlled trial.

SETTING

Hospital-based hand therapy clinics.

PARTICIPANTS

Fifty-nine adults with mild-to-moderate CTS were randomly assigned to wear a wrist splint (control group) or an MCP splint (intervention group) for 6 weeks.

OUTCOME MEASURES

The standardised outcome measures used included grip and pinch strength, the static two-point discrimination test, Phalen's manoeuvre test, Tinel's sign and the Boston CTS Questionnaire.

RESULTS

Both groups improved significantly from splint use in some clinical features. The wrist splint and the MCP splint groups had significant improvements in lateral pinch strength (p=0.032 and p=0.002, respectively), two-point discrimination of the thumb (p=0.003 and p=0.041, respectively), two-point discrimination of the index (p=0.035 and p=0.023, respectively) and the Phalen's manoeuvre symptoms (p=0.025 and p=0.002, respectively). The MCP splint group had additional improvements over the wrist splint group in tip pinch (p=0.012) and Palmar pinch (p=0.011) strength.

CONCLUSION

Splinting is a practical and effective intervention option for improving the symptoms of CTS. A wrist splint that incorporates the MCP joints is more effective than the traditional wrist-only splint, with long-lasting improvements that remained consistent after 6 months of the splint intervention. Using the more effective MCP splint may consequently reduce disability, facilitate return to work and lower the associated costs.

TRIAL REGISTRATION NUMBER

ISRCTN13189602.

In vivo evidence of lumbricals incursion into the carpal tunnel in healthy hands: An ultrasonographic cross sectional study

INTRODUCTION

During finger flexion, the tendons of flexor digitorum profundus migrate proximally, along with their attached lumbrical muscles. This incursion was suggested to extend into the Carpal Tunnel. Ultrasonographic imaging can be used to assess in vivo soft tissue behavior and incursion.

PURPOSE OF THE STUDY

To clinically quantify the lumbrical muscles incursion in different finger positions.

STUDY DESIGN

Cross sectional, observational study.

METHODS

The lumbricals of 20 healthy adults with no history of hand injuries were evaluated with neuromuscular ultrasound imaging (n = 160 lumbricals). The lumbrical muscles migration was measured as the participants actively moved their fingers from full extension to 50% flexion, and 100% flexion.

RESULTS

Of the 160 lumbricals measures, the incursion occurred at 18.1% of fingers at 50% finger flexion, and increased to 79.4% during full finger flexion. The lumbricals migrated a total of 2.99 cm after full finger flexion, and ended up 0.76 cm (SD = 0.86 cm) inside the Carpal Tunnel. The metacarpophalangeal joint range of motion of the index finger at the point where the lumbricals entered the distal border of the Transverse Carpal Ligament was 84.4° (SD = 6.8°). The Carpal Tunnel cross-sectional area during finger extension was 1.68 (0.35) cm², and increased to 1.81 (0.33) cm² after full finger flexion.

CONCLUSION

This study showed direct evidence of lumbrical incursion into the Carpal Tunnel during finger flexion. The cross-sectional area of the Carpal Tunnel increased during full finger flexion in comparison to full finger extension, supplementing the evidence of increase content within the Carpal Tunnel. The findings of this study have significant clinical implications for the conservative treatment of the Capral Tunnel Syndrome.

Comparative efficacy of the dorsal application of Kinesio tape and splinting for carpal tunnel syndrome: A randomized controlled trial

BACKGROUND

Carpal tunnel syndrome (CTS) symptoms are problematic especially when signs and symptoms are not substantial enough to require surgical intervention. Conservative treatments have mixed effectiveness, yet are one of the best options for mild to moderate CTS. Kinesio tape is an emerging modality, as it provides biomechanical support while allowing movement.

PURPOSE

The purpose of this study was to determine the efficacy of dorsal application of Kinesio tape on occupational performance as measured by pain and function in individuals with mild to moderate CTS, as compared with the accepted nonsurgical intervention of general cockup orthosis and lumbrical stretching exercises versus sham tape.

STUDY DESIGN

Single-blind randomized controlled trial.

METHODS

Forty-four participants (68 wrists) with CTS were randomized to one of three interventions: Kinesio tape group, sham group, or standard protocol group. Each completed baseline and four subsequent measurements of numeric pain rating scale, visual analog scale (VAS), Boston Carpal Tunnel Questionnaire (BCTQ), grip and pinch, with application of intervention every three days. Daily symptom journals were completed, standard protocol group recorded wearing schedule and exercises.

RESULTS

In the forearm and wrist, a significant reduction in median numeric pain rating scale pain scores in Kinesio tape group was observed (r = 0.76, P = .01; r = 0.77, P = .01; respectively), but not in the standard protocol group (r = 0.51, P = .17; r = 0.53, P = .11) and sham group (r = 0.46, P = .30; r = 0.39, P = .43) with a minimal clinically important difference of 1.0. In the Kinesio tape group, the forearm (24%) and wrist (36%) reached the clinical significance as compared with the standard protocol forearm (18%) and wrist (32%). The minimal clinically important difference for pain reduction on the visual analog scale was 1.64. Kinesio tape and sham group had significant improvement in function, but not the standard protocol group.

DISCUSSION

This study provides promising evidence for the use of Kinesio tape as a possible conservative intervention for management of symptoms in individuals with mild to moderate CTS. The study also illuminates new considerations of younger, active individuals reporting signs and symptoms of CTS as well as mechanism of effects on pain reduction.

CONCLUSIONS

Kinesio tape provided additional improvement in pain and function as compared to the standard approach.

Median nerve travel and deformation in the transverse carpal tunnel increases with chuck grip force and deviated wrist position

Background

We assessed median nerve travel and deformation concurrently to better understand the influence of occupational risk factors on carpal tunnel dynamics, including forceful chuck gripping and deviated wrist positions.

Methods

Fourteen healthy right-hand dominant participants performed a chuck grip in 6 experimental conditions: two relative force levels (10% and 40% of maximum voluntary effort); three wrist positions (15° radial deviation, 0° neutral, 30° ulnar deviation). Chuck grip forces were measured with a load cell while the transverse cross-section of the carpal tunnel was imaged via ultrasound at the distal wrist crease. Images of the median nerve were analyzed in ImageJ to assess cross-sectional area, circularity, width, and height as well as travel in the anterior-posterior and medial-lateral axes.

Results

We found a main effect of deviated wrist position on both anterior-posterior and medial-lateral travel, with the greatest nerve travel occurring in 30° ulnar deviation. There was also a significant interaction between chuck grip force and deviated wrist position on cross-sectional area. Specifically, the area decreased with 40% vs. 10% chuck grip force when the wrist was in 30° ulnar deviation; however, there were no changes in 0° neutral and 15° radial deviation.

Discussion

Overall, we demonstrated that forceful chuck gripping in deviated wrist positions influenced carpal tunnel dynamics, resulting in both migratory and morphological changes to the median nerve. These changes may, in turn, increase local strain and stress with adjacent structures in the carpal tunnel. Future studies mapping contact stress between structures may further elucidate injury development of work-related carpal tunnel syndrome.

In vivo tissue interaction between the transverse carpal ligament and finger flexor tendons

The transverse carpal ligament (TCL) is a component of the flexor pulley system of the wrist, keeping the flexor tendons in place by resisting their volar displacement. The purpose of this study was to investigate the in vivo biomechanical interaction between the TCL and flexor tendons in response to tendon tensioning with the wrist at various postures. In eight healthy subjects, the flexor digitorum superficialis and profundus tendons were tensioned by isometrically applying loads (5, 10, and 15N) to the index finger while the wrist posture was at 20° extension, neutral, 20° flexion, and 40° flexion. The TCL and flexor tendons were imaged at the distal carpal tunnel cross section using ultrasound. The volar-dorsal positions of the tendons, TCL arch height, and TCL-tendon distances were calculated. With increasing wrist flexion, the flexor tendons moved volarly, the TCL arch height increased, and the TCL-tendon distances decreased, indicating that the flexor tendons contacted the TCL and pushed it volarly. The TCL-tendon interaction was amplified by the combination of finger loading and wrist flexion. This study provides in vivo evidence of the biomechanical interaction between the TCL and flexor tendons. Repetitive TCL-tendon interactions may implicate the interacting tissues and the median nerve resulting in tissue maladaptation and nerve compression.

Development of Kinematic Graphs of Median Nerve during Active Finger Motion: Implications of Smartphone Use

Background

Certain hand activities cause deformation and displacement of the median nerve at the carpal tunnel due to the gliding motion of tendons surrounding it. As smartphone usage escalates, this raises the public’s concern whether hand activities while using smartphones can lead to median nerve problems.

Objective

The aims of this study were to 1) develop kinematic graphs and 2) investigate the associated deformation and rotational information of median nerve in the carpal tunnel during hand activities.

Methods

Dominant wrists of 30 young adults were examined with ultrasonography by placing a transducer transversely on their wrist crease. Ultrasound video clips were recorded when the subject performing 1) thumb opposition with the wrist in neutral position, 2) thumb opposition with the wrist in ulnar deviation and 3) pinch grip with the wrist in neutral position. Six still images that were separated by 0.2-second intervals were then captured from the ultrasound video for the determination of 1) cross-sectional area (CSA), 2) flattening ratio (FR), 3) rotational displacement (RD) and 4) translational displacement (TD) of median nerve in the carpal tunnel, and these collected information of deformation, rotational and displacement of median nerve were compared between 1) two successive time points during a single hand activity and 2) different hand motions at the same time point. Finally, kinematic graphs were constructed to demonstrate the mobility of median nerve during different hand activities.

Results

Performing different hand activities during this study led to a gradual reduction in CSA of the median nerve, with thumb opposition together with the wrist in ulnar deviation causing the greatest extent of deformation of the median nerve. Thumb opposition with the wrist in ulnar deviation also led to the largest extent of TD when compared to the other two hand activities of this study. Kinematic graphs showed that the motion pathways of median nerve during different hand activities were complex.

Conclusion

We observed that the median nerve in the carpal tunnel was rotated, deformed and displaced during the hand activities that people may be performed when using a smartphone, suggesting an increased risk of carpal tunnel syndrome (CTS). In addition, the kinematic graphs of median nerve developed in the present study provide new clues for further studies on the pathophysiology of CTS, and alerting smartphone users to establish proper postural habits when using handheld electronic devices.

Morphological and positional changes of the carpal arch and median nerve during wrist compression

BACKGROUND

The carpal tunnel is a fibro-osseous structure containing the median nerve and flexor tendons. Its cross-sectional area has been shown to increase during compressive force application to the carpal bones in modeling and in vitro studies. The purpose of this study was to investigate the morphological and positional changes of the carpal arch and median nerve while in vivo compressive force was applied in the radioulnar direction across the wrist.

METHODS

Ultrasound images of the carpal tunnel and its contents were captured for 11 healthy, female volunteers at the distal tunnel level prior to force application and during force application of 10 and 20N.

FINDINGS

With applied force, the carpal arch width significantly decreased, while the carpal arch height and area significantly increased (P<0.001). The median nerve shape became more rounded as the compressive force magnitude increased, reflected by decreases in the nerve's flattening ratio and increases in its circularity (P<0.001). The applied force also resulted in nerve displacement in the radial-volar direction.

INTERPRETATION

This study demonstrates that noninvasively applying radioulnar compressive force across the wrist may potentially provide relief of median nerve compression to patients suffering from carpal tunnel syndrome.