Carpal-tunnel pressure

Non-Surgical Carpal Arch Space Augmentation for Median Nerve Decompression

The carpal tunnel is a tightly bounded space, making the median nerve prone to compression and eventually leading to carpal tunnel syndrome. Carpal tunnel release surgery transects the transverse carpal ligament to expand the tunnel arch space, decompress the median nerve, and relieve the associated symptoms. However, the surgical procedure unavoidably disrupts essential anatomical, biomechanical and physiological functions of the wrist, potentially causing reduced grip strength, pillar pain, carpal bone instability, scar tissue formation, and perineural fibrosis. It is desirable to decompress the median nerve without surgically transecting the transverse carpal ligament. This paper is to review several approaches we have developed for nonsurgical carpal arch space augmentation (CASA), namely, radio ulnar wrist compression, muscle-ligament interaction, palmar pulling, and collagenolysis of the transverse carpal ligament. Briefly summarized is the research work on the CASA topic about theoretical considerations, in vitro and in situ experiment, computational modeling, and human subject studies with asymptomatic and carpal tunnel syndrome hands.

An Integrated Review of Carpal Tunnel Syndrome: New Insights to an Old Problem

Carpal tunnel syndrome (CTS) is a common entrapment neuropathy characterized by pain, numbness, and impaired function of the hand due to compression of the median nerve at the level of the wrist. Although CTS can develop from repetitive strain, injury, or medical conditions, there are also congenital and genetic risk factors that can predispose individuals to the condition. With respect to anatomical factors, some individuals are born with a smaller carpal tunnel, which increases their susceptibility to median nerve compression. Variations in specific genes, such as those encoding proteins involved in extracellular matrix remodeling, inflammation, and nerve function, have also been linked to an increased risk for CTS. CTS is associated with a high cost of health care maintenance and loss of work productivity. Therefore, it is vital that primary care physicians fully understand the anatomy, epidemiology, pathophysiology, etiology, and risk factors of CTS, so they can be proactive in prevention, diagnosing, and guiding proper treatment. This integrated review also provides insights into how biological, genetic, environmental, and occupational factors interact with structural elements to determine who is most likely to acquire and suffer from CTS. Keeping health practitioners abreast of all the factors that could impact CTS should go a long way in decreasing the health care and socioeconomic burden of CTS.

The effects of wrist position and radioulnar wrist compression on median nerve longitudinal mobility

BACKGROUND

Carpal tunnel syndrome is an entrapment neuropathy at the wrist characterized by compromised median nerve mobility. The purpose of this study was to investigate the effect of wrist position on median nerve longitudinal mobility in healthy subjects and the effect of radioulnar wrist compression on the median nerve mobility under non-neutral wrist positions.

METHODS

Dynamic B mode ultrasound images captured longitudinal median nerve motion in the carpal tunnel in 10 healthy subjects at wrist neutral position, 30-degree flexion, and 30-degree extension. In each position, RWC of 0, 5, 10, and 15 N were applied. One-way repeated measure analysis of variance (ANOVA), Post-hoc Tukey's tests, and the Friedman Test were used to show the significant differences of median nerve longitudinal mobility at different wrist positions and force conditions.

FINDINGS

Median nerve longitudinal mobility was found to be significantly influenced by wrist position (P < 0.05). The mobility under wrist neutral position was 3.02 mm/s, 38% higher than under wrist flexion (2.18 ± 0.60 mm/s), and 32% higher than under wrist extension (2.29 ± 0.43 mm/s). The impaired median nerve mobility was significantly restored under 10 N radioulnar wrist compression (P < 0.05), by 34.4% under wrist flexion (3.03 ± 0.85 mm/s), and 38.9% under wrist extension (3.07 ± 0.79 mm/s).

INTERPRETATION

Non-neutral wrist positions compromise median nerve longitudinal mobility, but moderate radioulnar compressive forces are beneficial in the recovery of median nerve longitudinal mobility, and may help to prevent symptoms associated with carpal tunnel syndrome.

Externally applied force helps reduce bowstring effect of flexors in patients with carpal tunnel release surgery

BACKGROUND

Patients with severe carpal tunnel syndrome (CTS) undergo carpal tunnel release (CTR) surgery to alleviate pressure in the carpal tunnel. However, the subsequent lack of the transverse carpal ligament (TCL) causes the bowstring phenomenon of the flexor tendons and increases the potential incidence of trigger finger.

OBJECTIVE

This study aimed to investigate the effects of various compressive forces on the flexor tendon and identify the appropriate force needed to mitigate the bowstring effect of those flexors.

DESIGN

Cross-sectional repeated measures comparison.

METHOD

Thirteen CTS patients who underwent CTR surgery were asked to flex the middle finger while applying different external compressive forces, just contact, 4N, and 8N force, over the carpal tunnel. Images of the flexor tendon within the carpal tunnel and at the metacarpal phalangeal (MCP) joint were recorded via ultrasound.

RESULT

Results show that the compression force limited the volar migration of the flexor tendon under maximal voluntary contraction (MVC) conditions. Entrance angles between the flexor tendon and metacarpal bone also decreased as the external compressive force increased.

CONCLUSIONS

Findings of this study may indicate that applying compression force on the carpal tunnel is useful for CTS patients and can inhibit the volar shift of the flexor digitorum superficialis (FDS) tendon after surgery, which may further prevent trigger finger.

Increased Risk of Carpal Tunnel Syndrome in People With Spinal Cord Injury: A Nationwide Longitudinal Follow-Up Study

OBJECTIVE

To investigate the long-term risk of carpal tunnel syndrome (CTS) in people with spinal cord injury (SCI).

DESIGN

Retrospective cohort study.

SETTING

Taiwan's Longitudinal Health Insurance Database 2005, containing data about 1 million people randomly sampled from among those registered in the National Health Insurance Program as of 2005.

PARTICIPANTS

The SCI group consisted of 1681 subjects with SCI, and the comparison group comprised 6724 propensity score-matched subjects without SCI (N=8405). The variables included in propensity-score matching were age, sex, comorbid conditions, and socioeconomic status.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

The occurrence of newly diagnosed CTS, defined by at least 1 hospital discharge or 2 outpatient visits with a diagnosis of CTS.

RESULTS

The incidence density of CTS in the SCI group was 7.55 per 1000 person-years (95% confidence interval [CI], 6.03-9.33), and in the comparison group, 4.61 per 1000 person-years (95% CI, 4.08-5.19). The hazard ratio (HR) of CTS for the SCI group was therefore 1.59 (95% CI, 1.24-2.03). Additionally, the HR of CTS for the cervical-SCI subgroup, 1.90 (95% CI, 1.21-2.97) was considerably higher than that of its noncervical counterpart, 1.47 (95% CI, 1.09-1.98).

CONCLUSIONS

People with both cervical and noncervical SCI have an increased risk of developing CTS, as compared with those without SCI. Moreover, the CTS risk appears to be higher for individuals with cervical SCI than their noncervical SCI counterparts.

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.

A non-invasive technique for evaluating carpal tunnel pressure with ultrasound vibro-elastography for patients with carpal tunnel syndrome: A pilot clinical study

Carpal tunnel syndrome (CTS) is a disorder that affects the median nerve at the wrist sufficient to cause impairment of nerve function. Elevated carpal tunnel pressure (CTP) leads to median nerve pathology, sensory, and motor changes in CTS patient. The techniques to quantify CTP used in clinic are invasive. This study aimed to investigate the feasibility of a noninvasive ultrasound vibro-elastography (UVE) to predict CTP in CTS patients and healthy individuals. The magnitudes of shear wave speed ratio (rSWS) of the 10 CTS patients (10 hands) and 6 healthy individuals (12 hands), and 10 cadaveric hands were compared using UVE. The ratios of intra to extra-carpal tunnel SWS in CTS patients was significantly higher than those in the healthy individuals (p = 0.0008) and cadaveric hands (p = 0.0015) with 500-g tendon tension. We estimated the CTP in the carpal tunnel using the mean rSWS of each group obtained from the present study and the linear approximation obtain from cadaveric hands data with 500-g tendon tension (y = 0.0036x + 1.1413). These results indicated that the elevated pressure applied to the 3rd flexor digitorum superficialis tendon in the carpal tunnel of CTS patients resulted in faster shear wave propagation. These results show that UVE was useful to indirectly estimate the CTP by measuring the rSWS; thus, they are potentially useful for the early diagnosis and assessment of CTS.

Modification of intra-carpal tunnel pressure after Z-lengthening of the transverse carpal ligament

Background Flexor retinaculum reconstruction techniques or simply Flexor Retinaculum Z-lengthening have been proposed to preserve Flexor Retinaculum continuity after carpal tunnel release. Their effectiveness is based solely on symptom relief. There has been no analysis of the effects on intra-carpal tunnel pressure of Flexor Retinaculum-lengthening techniques. Objective was to compare intra-carpal tunnel pressure outcomes between complete division and Z-lengthening of the Retinaculum in a cadaveric model of carpal tunnel release. Methods Experimental study of carpal tunnel pressure after surgical Flexor Retinaculum modification in 10 fresh-frozen forearm and hand cadaveric specimens. The Kyphon™ Balloon Kyphoplasty system was used to measure the pressure before and after infusing 1, 2, 3, 4 and 5 ml of saline solution when untreated (Flexor Retinaculum continuity stage I), when Z-lengthened (Flexor Retinaculum continuity stage II), and after complete Flexor Retinaculum division (Flexor Retinaculum continuity stage III). Finding Intra-carpal tunnel pressure increased with larger volume of infused saline solution, although mean pressures were lower after Z lengthening or complete division of the Retinaculum than at baseline. Analysis of linear regression coefficients indicated significant differences as a function of FR continuity stage (F(2,18) = 18.38, p < 0.001), while the Bonferroni test revealed significant differences in slopes between stages I and III (p = 0.003), between stages I and II (p < 0.02), but not between stages II and III (p > 0.05). Interpretation The effectiveness of carpal tunnel release and the reduction in intra-carpal tunnel pressures obtained by Z-lengthening of the FR were similar to those observed after its complete division, while preserving FR continuity.

Content validation of the Kamath and Stothard questionnaire for carpal tunnel syndrome diagnosis: a cognitive interviewing study

BACKGROUND

Accurate diagnosis of carpal tunnel syndrome (CTS) is essential for directing appropriate treatment; and for making decisions about work injury claims. The Kamath and Stothard Questionnaire (KSQ) is a self-reported tool used for the diagnosis of CTS. Comprehensibility and comprehensiveness of this questionnaire are critical to diagnostic performance and need to be established. The purpose of the study was to describe how potential respondents, clinicians, and measurement researchers interpret KSQ questions in order to identify and resolve potential sources of misclassification.

METHODS

Hand therapists, measurement researchers, participants with CTS, and a control group were interviewed using cognitive interviewing techniques (talk aloud, semi-structured interview probes) in Hamilton, Canada. All interviews were recorded and transcribed verbatim. A directed content analysis was done to analyze the interviews using a previously established framework.

FINDINGS

Eighteen participants were interviewed. Areas, where questions were unclear to some participants, were recorded and categorized into five themes: Clarity and Comprehension (52%), Relativeness (38%), Inadequate Response Definition (4%), Perspective Modifiers (4%), and Reference Point (2%). Respondents also identified several symptoms of CTS that are not covered by the KSQ that might be of diagnostic value, e.g., weakness and dropping items.

CONCLUSION

The content validity of the current iteration of the KSQ was not established. The problematic questions identified in the study have been reported to have low specificity and negative predictive values in a previous quantitative study. The content validity issues identified may explain the poor performance. Recommendations were made to modify the wording of the KSQ and the potential addition of three new questions. Future studies should determine whether the modified questionnaire can provide better diagnostic accuracy and psychometric properties. The results of this study may assist in ruling in or out CTS diagnosis to a wide variety of target audience, such as hand specialists, physical and occupational therapists, as well as family doctors.

Ultrasound-Guided Hydrodissection With Corticosteroid Injection in the Treatment of Carpal Tunnel Syndrome: A Pilot Study

OBJECTIVES

Corticosteroid injections can provide (temporary) relief in patients with mild to moderate carpal tunnel syndrome (CTS). Hydrodissection as part of an injection has been associated with positive clinical outcomes but data for CTS so far has been scarce. This study is designed to assess patient tolerance and secondarily provide pilot data on the added effect of hydrodissection.

METHODS

Twenty CTS patients were randomized to an ultrasound-guided betamethasone injection with hydrodissection (5 mL) or without (2 mL). Patient tolerance was assessed directly after intervention and patient-reported outcome after 4 and 24 weeks. Intra-group data were compared using Wilcoxon Signed Rank and inter-group with Wilcoxon rank-sum tests.

RESULTS

Tolerance and pain scores did not differ between the two groups. Symptom scores decreased in both groups, but to a lesser extent in the hydrodissection group with a mean difference of -0.8 versus -1.5 in the control group at 4 weeks (P = .02). At 6 months, this difference was no longer present (P = .81). No statistically significant differences were found between the hydrodissection and control groups in the function or pain scores at follow-up at either time point.

CONCLUSION

After injection, both symptomatic and functional scores improved, but the hydrodissected group did not show additional improvement. Data presented can be used to support larger studies to assess the value of hydrodissection in CTS management.

Shear wave elastography of the median nerve: A mechanical study

BACKGROUND

Shear wave elastography (SWE) shows promise in peripheral neuropathy evaluation but has potential limitations due to tissue size and heterogeneity. We tested SWE sensitivity to elasticity change and the effect of probe position in a median nerve cadaver model.

METHODS

Ten specimens were used to measure median nerve elasticity under increasing loads using SWE and indentation. Measurements were compared using repeated-measures analysis of variance.

RESULTS

Indentation and SWE-based longitudinal nerve elasticity increased with tensile loading (P < .01), showing a similar relationship. Acquisition in a transverse plane showed lower values compared with longitudinal measurements, mostly under higher loads (P = .03), as did postdissection elasticity (P = .02). Elasticity did not change when measured proximal to the carpal tunnel.

CONCLUSIONS

Longitudinal SWE is sensitive to changes in median nerve elasticity. Measuring elasticity of peripheral nerves noninvasively could elucidate intra-neural pathology related to compression neuropathies, and proof to be of added value as a diagnostic or prognostic tool.

Postoperative diagnostic potentials of median nerve strain and applied pressure measurement after carpal tunnel release

Bakground

The objective of this study is to investigate the prognostic values of median nerve strain and applied pressure measurement for the assessment of clinical recovery after carpal tunnel release.

Methods

Forty-five wrists, from 45 idiopathic carpal tunnel syndrome patients who treated with open carpal tunnel release, were evaluated by ultrasound. Median nerve strain, pressure applied to the skin, and ratio of pressure-strain were measured at the proximal part of the carpal tunnel. In addition, distal latencies in the motor and sensory nerve conductions studies and cross-sectional area of median nerve were measured. The parameters were compared before and after the open carpal tunnel release. According to patient recovery, the receiver operating characteristic curves were generated to evaluate the prognostic values of the parameters. The areas under the receiver operating characteristic curves were compared among parameters.

Results

There was a significant increase in the median nerve strain, and significant decreases in the pressure applied to the skin and ratio of pressure-strain after carpal tunnel release (P < 0.01). There were significant decreases in the distal latencies and the cross-sectional area after carpal tunnel release (P < 0.01). The areas under the curves were 0.689, 0.773, 0.811, 0.668, 0.637, and 0.562 for the pressure, strain, pressure-strain ratio, motor latency, sensory latency, and area, respectively.

Conclusions

The results suggest that elasticity of the median nerve and pressure around the nerve recover quickly after carpal tunnel release. Pressure-strain ratio was the most reliable parameter to reflect clinical recovery. The measurement of strain and applied pressure can be useful indicators to evaluate effectiveness of the carpal tunnel release.

Trial registration

Registered as NCT04027998 at ClinicalTrials.gov. Retrospectively registered on July 22, 2019.

The quantitative evaluation of the relationship between the forces applied to the palm and carpal tunnel pressure

Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy occurring in upper limbs. The etiology, however, has not been fully understood yet. Median nerve could be compressed by either increase of carpal tunnel pressure (CTP) or direct impingement when it is forced toward to carpal ligament especially in wrist flexion leading to CTS development. Thus, the increase of carpal tunnel pressure is considered an important role in CTS development. It has been identified that forces applied to the palm would affect the CTP. However, the quantitative relationship between palmar contact force and CTP is not known. The purpose of this study was to quantitatively evaluate the relationship between palmar contact force and CTP. Eight human cadaveric hands were used. The CTP was measured with a diagnostic catheter-based pressure transducer inserted into the carpal tunnel. A custom made device was used to apply forces to the palm for the desired CTP. Palmar contact forces corresponding to the determined CTP level were recorded respectively. The testing was repeated with different ranges of tension applied to the flexor digitorum superficialis tendon of the third finger. The tensions were constant at 50 g for the other flexor tendons and median nerve. The results showed that CTP increased linearly with the force applied to the palm. When CTP was 30 mmHg, mean values of the contact force to the palm was 293 g (SD: 15.2) including all tensions. These results would help to understand the effect of daily activities with hands on CTP.

The biomechanics of subsynovial connective tissue in health and its role in carpal tunnel syndrome

Carpal Tunnel Syndrome (CTS) is the most common surgically treated problem in the hand. Aside from the neuropathy itself, the most common findings are fibrosis of the subsynovial connective tissue (SSCT) and increased intra carpal tunnel pressure. Normally, the SSCT is a multilayer tissue interspersed among the carpal tendons and nerve. As the tendons move, successive SSCT layers are recruited, forming a gliding unit and providing a limit to differential movement. Exceeding this limit, damages the SSCT as has been shown in both cadavers and animal models. This damage leads to a non-inflammatory response with progressive fibrosis and nerve ischemia leaving the SSCT more susceptible to injury. Although the direct consequences for patients are not fully understood, ultrasound research shows that this fibrosis restricts median nerve displacement during tendon loading. This article aims to provide insights into the mechanical properties of SSCT described so far and place it in the context of CTS pathophysiology. A theoretical damage model concerning the SSCT is proposed showing a chain of events and vicious cycles that could lead to the nerve compression as it is found in CTS. Although not complete, this model could explain the pathophysiological pathway of idiopathic CTS.

The Anatomical Site of Constriction of the Median Nerve in Patients with Severe Idiopathic Carpal Tunnel Syndrome

During open carpal tunnel release in patients with severe idiopathic carpal tunnel syndrome, an area of constriction in the substance of the median nerve is frequently noted. In a prospective study of 30 patients, the central point of the constricted part of the nerve was determined intraoperatively and found to be, on average, 2.5 (range 2.2–2.8) cm from the distal wrist crease. This point always corresponded to the location of the hook of the hamate bone. These intraoperative findings were compared with the “narrowest” point of the carpal canal as determined by anatomical and radiological studies in the literature.

Postoperative Changes of Carpal Canal Pressure in Carpal Tunnel Syndrome: A Prospective Study with Follow-Up of 1 Year

Carpal canal pressures were measured in 103 patients with idiopathic carpal tunnel syndrome, before and after open release, with a postoperative follow-up of 1 year. Twenty-five normal subjects were used as controls. Pressures were measured with the wrists in three positions: neutral, full passive flexion and full passive extension. At each wrist position, the mean pre-operative pressures in the study group were significantly higher than in the control group. In both groups, the pressures were maximal with full passive extension and minimal in the neutral wrist position. Immediately after surgical release, there was a marked decrease of the carpal canal pressures. However, during the second postoperative month, there was a significant increase of the pressures at each wrist position, although these were still within the normal control range. This rise in pressures persisted to 12 months. These findings suggest that the carpal ligament reconstitutes by normal scar formation, but with lengthening such that the volume of the carpal canal is enlarged, so preventing a rise in pressure with return of the pre-operative problem.

Effect of grip type, wrist motion, and resistance level on pressures within the carpal tunnel of normal wrists

Elevated carpal tunnel pressure (CTP) has been associated with carpal tunnel syndrome. This study systematically evaluated the effect of wrist motion resistance and grip type on CTP during wrist motion typical of occupational tasks. CTP during four wrist motion patterns, with and without resistance, and with and without gripping, was measured in vivo in 14 healthy individuals. CTP measured during compound motions fell between that measured in the cardinal planes of wrist flexion/extension and radial/ulnar deviation. Generally, with no active gripping there was little pressure change due to wrist angular displacement or resistance level. However, concurrent active pinch or power grip increased CTP particularly in motions including extension. CTP typically did not increase during wrist flexion, and in fact often decreased. Extension motions against resistance when employing a pinch or power grip increase CTP more than motions with flexion. Results could help inform design or modification of wrist motion intensive occupational tasks. © 2014 The Authors.

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.

Pressure-morphology relationship of a released carpal tunnel

We investigated morphological changes of a released carpal tunnel in response to variations of carpal tunnel pressure. Pressure within the carpal tunnel is known to be elevated in patients with carpal tunnel syndrome and dependent on wrist posture. Previously, increased carpal tunnel pressure was shown to affect the morphology of the carpal tunnel with an intact transverse carpal ligament (TCL). However, the pressure-morphology relationship of the carpal tunnel after release of the TCL has not been investigated. Carpal tunnel release (CTR) was performed endoscopically on cadaveric hands and the carpal tunnel pressure was dynamically increased from 10 to 120 mmHg. Simultaneously, carpal tunnel cross-sectional images were captured by an ultrasound system, and pressure measurements were recorded by a pressure transducer. Carpal tunnel pressure significantly affected carpal arch area (p < 0.001), with an increase of >62 mm(2) at 120 mmHg. Carpal arch height, length, and width also significantly changed with carpal tunnel pressure (p < 0.05). As carpal tunnel pressure increased, carpal arch height and length increased, but the carpal arch width decreased. Analyses of the pressure-morphology relationship for a released carpal tunnel revealed a nine times greater compliance than that previously reported for a carpal tunnel with an intact TCL. This change of structural properties as a result of transecting the TCL helps explain the reduction of carpal tunnel pressure and relief of symptoms for patients after CTR surgery.

A non-invasive technique for estimating carpal tunnel pressure by measuring shear wave speed in tendon: a feasibility study

Although a close relationship between carpal tunnel pressure and median nerve dysfunction has been found, the current methods for pressure measurements are invasive, using a catheter in the carpal canal to monitor the pressure. A noninvasive method for quantifying carpal tunnel pressure would be useful as an alternative to the catheter method. In this study, a simplified experimental model was developed to measure the shear wave speed in a canine Achilles tendon under different tunnel pressures. The results showed that the speed of waves through the inside-tunnel tendon had a linear relationship with the pressure in the tunnel (first measurement: r=0.966, P<0.001; second measurement: r=0.970, P<0.001). This indicates that the tendon could serve as a strain gauge to evaluate the tunnel pressure by detecting the changes of wave propagation speed. However, further validations in human cadavers and clinical subjects are necessary.

Reliability and efficacy of the new massage technique on the treatment in the patients with carpal tunnel syndrome

We aimed to bring a more understandable and applicable technique to the literature instead of “massage therapy” in CTS. We compared our new technique with the splint wear, of which the efficacy in CTS has been proven with many studies. Eighty-four patients between 31 and 65 years of age were included in the study. The patients were divided into two equal groups. In the first group, splint and “Madenci” hand massage technique were applied, and in the second group only splint was applied. A splint was provided for all patients with tendon and nerve gliding exercises, and also when needed analgesic drugs were given. When the pretreatment and posttreatment parameters were compared via repetitive measurement analysis, it was found that PGA and MDPGA were significantly decreased in both groups (P = 0.001), whereas grip strength was significantly increased (P = 0.001). While no statistically significant difference was found between the groups regarding pretreatment values (P > 0.05), the posttreatment PGA, MDPGA, and grip strength scores were significantly improved in Group I compared to Group II (P < 0.05). To the best our knowledge, the present study is the first and largest study in the literature conducted on the massage technique that will contribute to the treatment of CTS. As this new massage technique is easy for self-application, cheap, and practical, every patient with CTS can apply the massage to him/herself easily.

Gliding resistance of flexor tendon associated with carpal tunnel pressure: a biomechanical cadaver study

The purpose of this study was to investigate the effect of carpal tunnel pressure on the gliding characteristics of flexor tendons within the carpal tunnel. Eight fresh human cadaver wrists and hands were used. A balloon was inserted into the carpal tunnel to elevate the pressure. The mean gliding resistance of the middle finger flexor digitorum superficialis tendon was measured with the following six conditions: (1) as a baseline, before balloon insertion; (2) balloon with 0 mmHg pressure; (3) 30 mmHg; (4) 60 mmHg; (5) 90 mmHg; (6) 120 mmHg. The gliding resistance of flexor tendon gradually increased as the carpal tunnel pressure was elevated. At pressures above 60 mmHg, the increase in gliding resistance became significant compared to the baseline condition. This study helps us to understand the relationship between carpal tunnel pressure, which is elevated in the patient with carpal tunnel syndrome (CTS) and tendon gliding resistance, which is a component of the work of flexion. These findings suggest that patients with CTS may have to expend more energy to accomplish specific motions, which may in turn affect symptoms of hand pain, weakness and fatigue, seen commonly in such patients.

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.

Pressure measurement in carpal tunnel syndrome : correlation with electrodiagnostic and ultrasonographic findings

OBJECTIVE

This study was done to evaluate the correlation between carpal tunnel pressure (CTP), electrodiagnostic and ultrasonographic findings in patients with carpal tunnel syndrome (CTS).

METHODS

CTP was measured during endoscopic carpal tunnel release (ECTR) for CTS using Spiegelberg ICP monitoring device with parenchymal type catheter. Neurophysiologic severity and nerve cross sectional area were evaluated using nerve conductive study and ultrasonography (USG) before ECTR in all patients.

RESULTS

Tests were performed in a total of 48 wrists in 39 patients (9 cases bilateral). Maximum CTP was 56.7 +/- 19.3 mmHg (Mean +/- SD) and 7.4 +/- 3.3 mmHg before and after ECTR, respectively. No correlation was found between maximum CTP and either neurophysiologic severity or nerve cross sectional area, whereas we found a significant correlation between the latter two parameters.

CONCLUSION

CTP was not correlated with neurophysiologic severity and nerve cross sectional area. Dynamic, rather than static, pressure in carpal tunnel might account for the basic pathophysiology of CTS better.

Investigation of segmental carpal tunnel pressure in patients with idiopathic carpal tunnel syndrome--is it necessary to release the distal aponeurotic portion of the flexor retinaculum in endoscopic carpal tunnel release surgery?

Segmental carpal tunnel pressure was measured in 12 hands of 11 idiopathic carpal tunnel syndrome patients before and after two-portal endoscopic carpal tunnel release. We aimed to determine at which part of the carpal tunnel the median nerve could be compressed, and to evaluate whether carpal tunnel pressure could be reduced sufficiently at all segments of the carpal tunnel after the surgery. Pressure measurements were performed using a pressure guide wire. The site with the highest pressure corresponded to the area around the hamate hook; the pressure in the area distal to the flexor retinaculum could be pathogenically high (more than 30 mmHg) before the surgery. The two-portal endoscopic carpal tunnel release achieved sufficient pressure reduction in all segments of the carpal tunnel when the flexor retinaculum and the fibrous structure between the flexor retinaculum and the palmar aponeurosis were completely released.

Historical review of carpal tunnel syndrome

The first description of median nerve compression in the carpal tunnel goes back to 1854, but it was only a century later that the term "carpal tunnel syndrome" (CTS) appeared in print. Until then, patients with symptoms, which we now know were due to CTS, were sometimes diagnosed as having acroparaesthesia, and at other times compression of the motor branch of the median nerve or the brachial plexus. The first description of an operation to open the carpal tunnel goes back to 1933, but only with Brain and Phalen was idiopathic CTS defined from both clinical and anatomopathological viewpoints. Since 1960, CTS has become the most frequently diagnosed of peripheral compression-induced neuropathies. The last part of this paper reports the latest theories giving an aetiological explanation of cases of CTS until now considered to be idiopathic.

Permeability of the subsynovial connective tissue in the human carpal tunnel: a cadaver study

BACKGROUND

The purpose of this study was to determine the permeability of the normal carpal tunnel subsynovial connective tissue.

METHODS

Subsynovial connective tissue samples (10mm(2)) were obtained from 10 fresh frozen human cadavers without a history of carpal tunnel syndrome. The thickness of the sample was measured using a charge-coupled device laser displacement system. Each specimen was tested for permeability in a closed pressure chamber at 13.8, 41.3, 68.9 and 96.5 kPa.

FINDINGS

Since permeated flow was very low in all specimens, the permeability could be calculated only for eight specimens at 96.5 kPa pressure and for three specimens at 68.9 kPa. The mean permeability at 96.5 kPa was mean 0.89 (SD 0.93)x10(-14)m(4)/Ns and at 68.9 kPa was mean 1.04 (SD 1.54)x10(-14)m(4)/Ns.

INTERPRETATION

The subsynovial connective tissue is the most characteristic tissue in the carpal tunnel; it is found in no other location in such abundance. It is well known that carpal tunnel syndrome is the result of increased pressure within the carpal tunnel. This lack of permeability in the subsynovial connective tissue may explain the predisposition of this region for pressure buildup and subsequent neuropathy.

Guidelines for wrist posture based on carpal tunnel pressure thresholds

OBJECTIVE

To develop work guidelines for wrist posture based on carpal tunnel pressure.

BACKGROUND

Wrist posture is considered a risk factor for distal upper extremity musculoskeletal disorders, and sustained wrist deviation from neutral at work may be associated with carpal tunnel syndrome. However, the physiologic basis for wrist posture guidelines at work is limited.

METHODS

The relationship of wrist posture to carpal tunnel pressure was examined in 37 healthy participants. The participants slowly moved their wrists in extension-flexion and radioulnar deviation while wrist posture and carpal tunnel pressure were recorded. The wrist postures associated with pressures of 25 and 30 mmHg were identified for each motion and used to determine the 25th percentile wrist angles (the angles that protect 75% of the study population from reaching a pressure of 25 or 30 mmHg).

RESULTS

Using 30 mmHg, the 25th percentile angles were 32.7 degrees (95% confidence interval [CI] = 27.2-38.1 degrees) for wrist extension, 48.6 degrees (37.7 -59.4 degrees) for flexion, 21.8 degrees (14.7-29.0 degrees) for radial deviation, and 14.5 degrees (9.6-19.4 degrees) for ulnar deviation. For 25 mmHg, the 25th percentile angles were 26.6 degrees and 37.7 degrees for extension and flexion, with radial and ulnar deviation being 17.8 degrees and 12.1 degrees, respectively.

CONCLUSION

Further research can incorporate the independent contributions of pinch force and finger posture into this model.

APPLICATION

The method presented can provide wrist posture guidelines for the design of tools and hand-intensive tasks.

Segmental carpal canal pressure in patients with carpal tunnel syndrome

PURPOSE

To clarify which part of the median nerve is the most compressed and to compare carpal canal pressure with the latency of the sensory nerve potential and the duration of symptoms.

METHODS

Fifteen patients with idiopathic carpal tunnel syndrome were studied using a pressure guidewire system to record canal pressure. The wire was introduced from the distal end of the carpal canal to 2 cm proximal to the distal wrist crease (DWC) and then retracted in 5-mm increments using an image intensifier to guide the progress. A nerve conduction study was performed, and all patients were asked how long the symptoms lasted.

RESULTS

Carpal canal pressure was significantly higher 5 to 15 mm distal to the DWC. The most compressed point was 10 mm distal to the DWC, with a pressure of 44.9 +/- 26.4 mm Hg. The correlation coefficient between the highest canal pressure and the latency was 0.393 and between highest canal pressure and duration of symptoms was 0.402.

CONCLUSIONS

Our study showed that the most compressed part of the median nerve in the carpal canal is 10 mm distal to the DWC. The carpal canal pressure was related to the latency and to the duration of symptoms.

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.

Stretch-activated channels: a mini-review. Are stretch-activated channels an ocular barometer?

All cells are subject to physical forces by virtue of their position in a dynamically changing environment. This review outlines the various putative 'mechanosensors', or sensors of pressure cells possess, and discusses in particular the role stretch-activated membrane channels play in pressure recognition and transduction. The widespread occurrence of these channels is discussed and these 'mechanosensors' are related to pressure-related diseases, in particular, glaucoma.

Effects of mechanical irritation on the autonomic part of the median nerve

The diagnosis of median nerve compression is generally based upon a prolonged nerve conduction velocity although this frequently is preceded by clinical symptoms for years. The present study was designed to identify indicators for early decompression of the median nerve in patients exhibiting symptoms compatible with carpal tunnel syndrome (CTS). Microvascular perfusion in finger tip skin and skin temperature were studied during dorsiflexion of the hand prior to and following a manual exercise test in control subjects and in patients with clinical symptoms and signs of CTS. Evaluation of the microcirculation was performed using photoplethysmography (PPG) and laser Doppler fluxmetry (LDF). Fingertip skin temperature was measured by thermography and was significantly reduced in patients after exercise (P < 0.001), whereas no significant change occurred in control subjects. During increasing degrees of dorsiflexion (0-75 degrees ) and after manual exercise, fingertip skin perfusion remained unchanged in both patients and control subjects. In conclusion, patients with low-grade CTS experience skin temperature reduction, presumably caused by increased sweating as opposed to a generally suspected vasoconstriction. These autonomic median nerve dysfunctions provide the physiological basis for the use of thermography in confirming low-grade CTS.

Conservative interventions for carpal tunnel syndrome

The assessment and conservative interventions in patients with carpal tunnel syndrome (CTS) are described in this paper. Information about surgical procedures and postoperative care has also been included. It is difficult to make definitive conclusions about the literature regarding success of treatment for CTS due to variations in outcome measures, severity of CTS, and inconsistencies in duration, dosage, and follow-up time for interventions. Based on what is known to date, this author recommends that patients with mild or moderate CTS be provided with a conservative program of splinting the wrist in neutral for nocturnal wear. In addition, intermittent exercise (nerve-gliding exercises) and activity modification, including avoidance of protracted periods of sustained gripping activities and awkward wrist positions, can be useful. This conservative program may be complemented by pain-relieving modalities during times of activity and supplemental participation in other exercise such as yoga. If symptoms are not relieved to the satisfaction of the patient, or they recur, then it is incumbent upon the therapist to refer the patient to a hand surgeon for injection or possible surgical decompression.

Canal pressures before, during, and after endoscopic release for idiopathic carpal tunnel syndrome

A special transducer was used to measure in situ carpal tunnel pressures in 20 patients who had surgery for idiopathic carpal tunnel syndrome (CTS) by one-portal endoscopic section of the flexor retinaculum. Pressures were elevated initially. The pressures were maximal (mean, 93 mm Hg) with full passive wrist extension. Peaks of high pressures, on average 97 mm Hg, were recorded with the Agee (MicroAire, Charlottesville, VA) endoscopic device in the canal. Release of the endoscopic flexor retinaculum resulted in a marked decrease of the pressures.

Vascular factors in carpal tunnel syndrome

An increase in hand and forearm volume was induced without hand movement in ten subjects who had carpal tunnel syndrome (CTS). A tester, unaware of sides affected by CTS, performed the Volume Provocation Test (VPT) by inflating a sphygmomanometer cuff around the upper arm to 15 mm Hg less than diastolic pressure for four minutes. Pre- and post-test volumes, intensity of discomfort, and quality and distribution of produced symptoms were recorded. The VPT induced significant increases of segment volumes bilaterally (P1 tailed <0.05), but not more on the side of strongest symptoms compared to the less affected, or asymptomatic side (P1 tailed = 0.07). Mean discomfort on the side of strongest symptoms (5.4/10) was significantly higher (P1 tailed <0.01) than on the contralateral side (2.4/10). In 44% of the affected arms, some or all of the subjects' nocturnal symptoms were reproduced after volume increase, suggesting that CTS is a vascular phenomenon in these patients.

Surgical treatment of common entrapment neuropathies in the upper limbs

Entrapment neuropathies of the upper extremity are common, debilitating conditions. Most patients with these neuropathies are readily diagnosed on purely clinical grounds and may be effectively managed with nonoperative measures. However, the broad differential diagnosis often necessitates electrodiagnostic testing and radiographic imaging to clarify the situation. This review focuses on three of the most common entrapment neuropathies in the upper limbs: carpal tunnel syndrome (median nerve entrapment at the wrist), cubital tunnel syndrome (ulnar nerve entrapment at the elbow), and radial tunnel syndrome (posterior interosseous nerve entrapment). Anatomical considerations, patient evaluation, indications for surgical intervention, options for surgical approaches, outcomes, and complications are discussed.

Correlation of segmental carpal tunnel pressures with changes in hand and wrist positions in patients with carpal tunnel syndrome and controls

We investigated pressures at 1 cm intervals along the carpal tunnel in 39 patients with carpal tunnel syndrome (CTS) and 12 controls. Pressures were measured for relaxed and gripping hand positions in combination with neutral, extended, and flexed wrist positions. Patient pressures exceeded control pressures, were below the previously reported 30 mmHg threshold for four of five locations in the relaxed neutral position and were typically greater in extension than in flexion. In the neutral position, both patient and control pressures were slightly above threshold levels just distal to the tunnel. Maximum intratunnel pressures were generally found in the central part of the tunnel and minimum pressures in the distal tunnel. Gripping hand pressures in the tunnel were lowest with the wrist flexed. In both controls and CTS patients, only in the neutral wrist and relaxed hand positions were pressures highest at the point where nerve conduction studies have indicated the nerve is most likely to be compromised (in the midpalm just distal to the distal margin of the carpal tunnel).

Effects of forearm pronation/supination on carpal tunnel pressure

The effects of forearm rotation and metacarpophalangeal (MP) flexion on carpal tunnel pressure were investigated in 17 healthy adults who had no evidence of carpal tunnel syndrome (CTS). Pressure was continuously recorded with a saline-filled catheter inserted into the carpal tunnel and connected to a pressure transducer while test subjects slowly rotated the forearm from full pronation to full supination. Forearm rotation was repeated with MP flexion of 0 degrees, 45 degrees, and 90 degrees. Both forearm rotation and MP flexion, and their interaction term, significantly affected carpal tunnel pressure and accounted for most of the variability in the data. Highest mean pressures (55 mmHg) were recorded in full supination and 90 degrees MP flexion and lowest pressures (12 mmHg) were recorded at 45 degrees pronation and 45 degrees MP flexion. These data may be useful in the design of tasks and hand tools in the management and prevention of CTS.

The effects of tendon load and posture on carpal tunnel pressure

Two pressure measurement techniques (catheter and bulb) were used to decompose the effects of tendon loads on carpal tunnel pressure (CTP). The catheter technique measures true hydrostatic pressure, whereas the bulb technique is a estimate of contact force or pressure on the median nerve. Eight cadaveric wrists were moved through a range of flexion-extension (0 degrees, 10 degrees, 20 degrees, 30 degrees, and 45 degrees of each) and radioulnar deviation (10 degrees and 20 degrees radial and 0 degrees, 10 degrees, 20 degrees, and 30 degrees ulnar) while CTPs were measured under 4 muscle loading conditions with the thumb, index, and long finger in a pinch-grip posture. The first of these was zero load. Then a 1-kg mass was applied in turn to both flexors of the index and long fingers, the palmaris longus (PL); and the flexor pollicis longus. The hydrostatic pressure was found to be affected by both wrist posture and tendon load. With no load, highest pressures were seen in wrist extension. Muscular loading elevated CPT, particularly the loading of palmaris longus with the wrist in extension and the digital flexors with the wrist flexed. Bulb pressure measurements, related to local contact forces by the digital flexors, indicated the highest loads on the median nerve with the wrist flexed. Palmaris longus loading created the highest pressures in extension and only moderate pressure in flexion, indicating that it may alter the geometry of the transverse carpal ligament. In view of the data from this study, it is necessary to incorporate measures of hydrostatic pressure and local contact forces to describe possible trauma to the median nerve in the carpal tunnel, as neither appears sufficient when used independently.

Intracarpal canal pressures: the role of finger, hand, wrist and forearm position

OBJECTIVE: The study examined the change in intracarpal canal pressure (ICCP) in relationship to finger, hand, wrist and forearm position. DESIGN: The study was an in vivo measurement of ICCP in seven subjects undergoing a standardized set of manoeuvres that systematically varied finger, hand, wrist, and forearm position. BACKGROUND: It has been known that the ICCP increased with extremes of wrist flexion and extension but the change in pressure in response to radial and ulnar deviation as well as hand and forearm position has not been reported. METHODS: The ICCP was measured using a slit catheter technique; each variation of position was repeated three times with continuous monitoring of ICCP, wrist angulation, and metacarpal-phalangeal joint angulation. RESULTS: The study demonstrated that ICCPs were lowest when the wrist is in a neutral position, the hand relaxed with fingers flexed and the forearm in a semi-pronated position. Wrist extension and flexion resulted in the greatest increase in ICCP followed by forearm pronation and supination. Radial and ulnar deviation also increased the pressure but to a lesser extent. CONCLUSIONS: The findings of this study support the concept that the wrist and forearm should be maintained in a neutral position during vocational and avocational activities in an effort to minimize pressure within the carpal tunnel and thereby reduce the risk of developing carpal-tunnel syndrome. RELEVANCE: It is desirable to know how the ICCP changes in response to change in hand, wrist, and forearm position so that work activities are designed to minimize the pressure within the carpal canal and thus maintain the viability of the median nerve within the carpal canal.

Position of the wrist associated with the lowest carpal-tunnel pressure: implications for splint design

Increased carpal-tunnel pressure has been implicated in the pathophysiology of carpal tunnel syndrome, but it is not known whether splints that immobilize the wrist in a functional position of extension minimize carpal tunnel pressure. To determine the position of the wrist that results in the lowest carpal-tunnel pressure, twenty control subjects and four patients who had carpal tunnel syndrome were evaluated with use of a new, dynamic method that continuously measures carpal tunnel pressure throughout the range of motion of the wrist. The pressure was measured by means of a pressure transducer connected to a flexible catheter that had been inserted into the carpal canal. The position of the wrist was measured simultaneously with use of a two-axis electrogoniometer. Aided by a computer monitor that displayed a moving line of real-time carpal-tunnel pressure, each subject was instructed to move the wrist throughout the range of motion and to adjust it to the position that corresponded to the lowest carpal-tunnel pressure. For the control subjects, the lowest carpal-tunnel pressure averaged 8 +/- 4 millimeters of mercury (1.07 +/- 0.53 kilopascals), and the average position of the wrist associated with the lowest pressure was 2 +/- 9 degrees of extension and 2 +/- 6 degrees of ulnar deviation.(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo measurement of carpal tunnel pressure in the functioning hand

We recorded directly the pressure within the carpal tunnel during nine different functional positions of the hand and wrist in 102 hands of 92 subjects. Carpal tunnel syndrome was present in 81 hands, and 21 served as controls. A significant rise in pressure was recorded not only with wrist flexion but also with wrist extension, making a fist, holding objects, and isolated isometric flexion of a finger against resistance. Intratunnel pressure dropped after 1 minute of hand and wrist exercises and remained below the resting pressure for over 15 minutes of continuous measurement. We did not observe a rebound phenomenon. Clinical Application: Non-surgical treatment of carpal tunnel syndrome should also include a significant reduction in making a fist, holding objects, pushing, and isolated finger work such as key punching and typing. Activities that require sustained contracture of finger flexor muscles (eg, grasp and hold) also should be avoided. Brief intermittent wrist and hand exercise is recommended to reduce the intratunnel pressure.

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.