Serial overnight recordings of intracarpal canal pressure in carpal tunnel syndrome patients with and without wrist splinting

Carpal tunnel syndrome

Carpal tunnel syndrome (CTS) is the most common nerve entrapment disorder worldwide. The epidemiology and risk factors, including family burden, for developing CTS are multi-factorial. Despite much research, its intricate pathophysiological mechanism(s) are not fully understood. An underlying subclinical neuropathy may indicate an increased susceptibility to developing CTS. Although surgery is often performed for CTS, clear international guidelines to indicate when to perform non-surgical or surgical treatment, based on stage and severity of CTS, remain to be elucidated. Neurophysiological examination, using electrophysiology or ultrasonography, performed in certain circumstances, should correlate with the history and findings in clinical examination of the person with CTS. History and clinical examination are particularly relevant globally owing to lack of other equipment. Various instruments are used to assess CTS and treatment outcomes as well as the effect of the disorder on quality of life. The surgical treatment options of CTS - open or endoscopic - offer an effective solution to mitigate functional impairments and pain. However, there are risks of post-operative persistent or recurrent symptoms, requiring meticulous diagnostic re-evaluation before any additional surgery. Health-care professionals should have increased awareness about CTS and all its implications. Future considerations of CTS include use of linked national registries to understand risk factors, explore possible screening methods, and evaluate diagnosis and treatment with a broader perspective beyond surgery, including psychological well-being.

Evaluation of Factors Associated with Night Pain in Women Undergoing Carpal Tunnel Release

BACKGROUND

Night pain has important diagnostic and prognostic values in patients with carpal tunnel syndrome (CTS). We aimed to determine whether night pain is associated with certain patient characteristics in female patients undergoing carpal tunnel release.

METHODS

We recruited 75 women with the mean age of 54 years who were scheduled for carpal tunnel release. Diagnosis of CTS was made based on both the clinical symptoms and the results of electrophysiologic studies. Patient characteristics investigated as factors potentially associated with night pain were: age, body mass index (BMI), symptom duration, comorbidities such as diabetes mellitus (DM) and thyroid disease, electrophysiologic severity of CTS, and sleep position. We conducted a logistic regression analysis to examine the relationships between the presence of night pain and the different patients' demographic and clinical variables.

RESULTS

Absence of night pain was associated with increased age (odds ratio (OR), 0.918, 95% confidence interval (CI), 0.851 to 0.99) and presence of DM (OR, 0.196; 95% CI, 0.046 to 0.835). The other variables assessed were not found to be associated with presence or absence of night pain.

CONCLUSIONS

This study found that in women undergoing carpal tunnel release, older patients or those having DM are slightly less likely to have night pain. As night pain is an important prognostic factor for CTS, further studies are warranted to determine whether the absence of night pain could affect outcome assessment of CTS in the elderly or patients with DM.

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.

Description, reliability and validity of a novel method to measure carpal tunnel pressure in patients with carpal tunnel syndrome

Elevated carpal tunnel pressure is an important pathomechanism in carpal tunnel syndrome (CTS). Several invasive methods have been described for direct measurement of carpal tunnel pressure, but all have two important limitations. The pressure gauge requires sterilisation between uses, which makes time-efficient data collection logistically cumbersome, and more importantly, the reliability of carpal tunnel pressure measurements has not been evaluated for any of the methods in use. This technical note describes a new method to measure carpal tunnel pressure using inexpensive, disposable pressure sensors and reports the within and between session reliability of the pressure recordings in five different wrist positions and during typing and computer mouse operation. Intraclass correlation coefficients (ICC[3,1]) were calculated for recordings within one session for healthy participants (n = 7) and patients with CTS (n = 5), and for recordings between two sessions for patients with CTS (n = 5). Overall, the reliability was high. With the exception of two coefficients, the reliability of the recordings at different wrist angles varied from 0.63 to 0.99. Reliability for typing and mouse operation ranged from 0.86 to 0.99. The new method described in this report is inexpensive and reliable, and data collection can be applied more efficiently as off-site sterilisation of equipment is not required. These advances are likely to promote future research into carpal tunnel pressure, such as investigation of the therapeutic mechanisms of various conservative treatment modalities that are believed to reduce elevated carpal tunnel pressure.

Diurnal variation in clinical and electrophysiologic parameters associated with carpal tunnel syndrome

OBJECTIVE

Patients with carpal tunnel syndrome (CTS) often report aggravated symptoms in the early morning. In this study, we aimed to identify diurnal variations in clinical and electrophysiologic parameters of patients with CTS.

DESIGN

A cross-sectional clinical and electrophysiologic study was designed. First, electrophysiologic examinations were performed at 2 p.m. to confirm the diagnosis of patients who had been clinically labeled with CTS. Patients who were electrophysiologically and clinically diagnosed with CTS were included in the study, and electrophysiologic examinations were repeated at 7 p.m. and 7 a.m. A total of 64 hands with CTS (27 bilateral, 10 unilateral) and 40 control hands were studied. Grip and pinch strength of all the patients included in the study were measured using a hand dynamometer. Finally, a CTS clinical symptom severity scale and functional status scale were used to measure the symptoms and functional impairment, respectively.

RESULTS

The median motor nerve distal latency and median F-minimum latency were found to be prolonged in the CTS group in the morning, and the grip strength was also markedly reduced at this time. Similar results were obtained for the median palm mixed nerve conduction velocity and amplitude.

CONCLUSIONS

This study demonstrated that the clinical and electrophysiologic parameters of CTS patients were clearly different in the morning hours, with the symptoms of CTS manifesting at that time.

Changes in Tissue Substance P Levels in Patients With Carpal Tunnel Syndrome

BACKGROUND:

Although carpal tunnel syndrome (CTS) is the most common entrapment neuropathy in adults, its etiology is not completely known. Chronic inflammation, fibrosis of the transverse carpal ligament (TCL), and altered sensory response contribute to the symptoms.

OBJECTIVE:

Because substance P (SP) is known to be involved in neuropathic pain, chronic inflammation, and fibrosis, the present study evaluated changes in SP levels in patients with CTS.

METHODS:

TCL, median nerve adventitia, and synovial connective tissue of the middle flexor digitorum superficialis tendon samples from patients (n = 42) with CTS and healthy control subjects (n = 13) who were operated on for hand wounds were obtained at surgery. A group of these patients with CTS (n = 9) had received meloxicam treatment for 10 days before surgery. A 2-step acetic acid extraction was used to determine changes in SP levels in free nerve endings (neuronal) and in nonneuronal cells.

RESULTS:

Changes in SP levels were observed in both neuronal and nonneuronal tissues. SP levels increased in extracts of the TCL and synovial connective tissue of the middle flexor digitorum superficialis tendon but not in the median nerve adventitia of patients with CTS. Meloxicam pretreatment increased SP levels in nonneuronal components of the TCL.

CONCLUSION:

These findings suggest that SP contributes to the pain and inflammation associated with CTS. Further studies are required to evaluate the therapeutic potentials of SP receptor (NK1R) antagonists in CTS.

Carpal lock and the volar-supporting orthosis in mild and moderate carpal tunnel syndrome

OBJECTIVE

The carpal lock, which is a hand/wrist orthosis that supports the dorsal aspect of the hand, was used in patients with mild-moderate carpal tunnel syndrome, and its clinical and electrophysiological effectiveness was compared with that of a volar-supporting orthosis.

DESIGN

Nerve conduction study and clinical evaluation of 24 patients (41 hands) with mild or moderate carpal tunnel syndrome were performed before and 3 mos after the use of the carpal lock or the volar-supporting orthosis.

RESULTS

Significant improvement was observed in electrophysiological parameters and clinical outcomes after use of both orthoses. There was no statistically significant difference between the two groups. Patients in the carpal lock group used the orthosis 89.6% of the prescribed time, whereas those in the volar-supporting orthosis group used the orthosis 79.2% of the prescribed time (P < 0.05).

CONCLUSIONS

The carpal lock may be used as an alternative to the volar-supporting orthosis.

Carpal tunnel syndrome and the use of computer mouse and keyboard: a systematic review

Background

This review examines evidence for an association between computer work and carpal tunnel syndrome (CTS).

Methods

A systematic review of studies of computer work and CTS was performed. Supplementary, longitudinal studies of low force, repetitive work and CTS, and studies of possible pathophysiological mechanisms were evaluated.

Results

Eight epidemiological studies of the association between computer work and CTS were identified. All eight studies had one or more limitation including imprecise exposure and outcome assessment, low statistical power or potentially serious biases. In three of the studies an exposure-response association was observed but because of possible misclassification no firm conclusions could be drawn. Three of the studies found risks below 1. Also longitudinal studies of repetitive low-force non-computer work (n = 3) were reviewed but these studies did not add evidence to an association. Measurements of carpal tunnel pressure (CTP) under conditions typically observed among computer users showed pressure values below levels considered harmful. However, during actual mouse use one study showed an increase of CTP to potentially harmful levels. The long term effects of prolonged or repeatedly increased pressures at these levels are not known, however.

Conclusion

There is insufficient epidemiological evidence that computer work causes CTS.

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.

A fluid-immersed multi-body contact finite element formulation for median nerve stress in the carpal tunnel

Carpal tunnel syndrome (CTS) is among the most important of the family of musculoskeletal disorders caused by chronic peripheral nerve compression. Despite the large body of research in many disciplinary areas aimed at reducing CTS incidence and/or severity, means for objective characterization of the biomechanical insult directly responsible for the disorder have received little attention. In this research, anatomical image-based human carpal tunnel finite element (FE) models were constructed to enable study of median nerve mechanical insult. The formulation included large-deformation multi-body contact between the nerve, the nine digital flexor tendons, and the carpal tunnel boundary. These contact engagements were addressed simultaneously with nerve and tendon fluid-structural interaction (FSI) with the synovial fluid within the carpal tunnel. The effects of pertinent physical parameters on median nerve stress were explored. The results suggest that median nerve stresses due to direct structural contact are typically far higher than those from fluid pressure.

[Modern approach to carpal tunnel syndrome treatment]

<zakljucak> U lecenju SKT primenjuje se konzervativno i hirursko lecenje. Konzervativno lecenje obuhvata imobilizaciju rucnog zgloba, lokalnu transkutanu aplikaciju kortikosteroida i analgetsku terapiju antireumaticima i antikonvulzivima. U hirurskom lecenju primenjuje se veliki broj tehnika u cilju dekompresije nerva. U izboru nacina lecenja SKT pored klinickog nalaza rukovodimo se i neurofizioloskom dijagnostikom komprimovanog nerva. Konzervativno lecenje se primenjuje kod blazih oblika i intermitentnih smetnji. Kada, i pored konzervativnog lecenja perzistira bol, a neurofizioloska ispitivanja pokazuju pogorsanje, neophodno je razmisljati o hirurskom lecenju. Atrofija tenara uz prisustvo denervacionih potencijala pri neurofizioloskom ispitivanju, uz postojanje neuroloskog deficita, upucuje na potrebu hirurskog lecenja.

Diagnosing carpal tunnel syndrome—clinical criteria and ancillary tests

Damage to the median nerve within the carpal tunnel gives rise to carpal tunnel syndrome (CTS), which is associated with a wide spectrum of symptoms. The predominant classic symptoms are nocturnal pain of the hand, and sensory disturbances within the distribution of the median nerve, both of which are characteristically relieved by hand movements. Ancillary tests, including nerve conduction studies (NCS) and imaging techniques, are mainly indicated when the classic defining features are absent. NCS are less accurate in the early stages of CTS, and in younger patients. Imaging tests (ultrasound and MRI), while still having a lower diagnostic accuracy than NCS, are proving to be useful for explaining persistence of symptoms following surgical relief. Supplementary tests of small nerve fiber function and measurement of intracarpal pressure might, in the future, improve early recognition of CTS, especially in the absence of well-defined symptoms.

Effectiveness of hand therapy interventions in primary management of carpal tunnel syndrome: a systematic review

The purpose of this study was to determine the effectiveness of hand therapy interventions for carpal tunnel syndrome (CTS) based on the best available evidence. A qualitative systematic review was conducted. A literature search using 40 key terms was conducted from the earliest available date to January 2003 using seven databases. Articles were randomly assigned to two of five reviewers and evaluated according to predetermined criteria for inclusion at each of the title, abstract, and article levels. Included studies were independently scored by two reviewers using a structured effectiveness quality evaluation scale and also graded according to Sackett's Levels of Evidence. There were 2027 articles identified from the literature search, of which 345 met the inclusion criteria. Twenty-four studies were used to formulate 30 recommendations. Current evidence demonstrates a significant benefit (grade B recommendations) from splinting, ultrasound, nerve gliding exercises, carpal bone mobilization, magnetic therapy, and yoga for people with CTS.

Upper extremity work-related musculoskeletal disorders: a treatment perspective

Numerous terms, including repetitive-stress injuries and cumulative-trauma disorders, have been used to describe what is now commonly termed work-related musculoskeletal disorders. The etiology of work-related musculoskeletal disorders is multifactorial and includes physical, individual, and psychosocial factors that contribute to the presenting symptoms. Prolonged positioning away from the ideal posture will affect neural and other soft tissues in the upper extremity. Abnormal postures and positions may result in chronic nerve compression or may shorten muscles and, if the muscle crosses over a nerve, compression may occur. These postures may also contribute to muscle imbalance. A thorough clinical evaluation is necessary to identify all sites of nerve compression, muscle imbalance, and factors affecting patient symptoms so that appropriate intervention can be instituted. Management must include patient education, postural correction, and a specific physical therapy program to address the multiple levels of nerve compression and cervicoscapular muscle imbalance. In addition to physical therapy intervention, behavioral modification at home and at work may be necessary for successful management.

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.

Multilevel nerve compression and muscle imbalance in work-related neuromuscular disorders

BACKGROUND

Work-related upper limb disorders have come under increasing scrutiny and become a frustrating problem.

METHODS

A unifying hypothesis to explain the multiplicity of symptoms with work related neuromuscular disorders is outlined. This multifactorial problem includes physical, individual, and psychosocial factors. Abnormal postures and positions may compress nerves or may alter muscle length resulting in secondary compressive forces on nerves or in muscle imbalances. Evaluation should identify all nerve compression levels and muscle imbalance in the arm and cervicoscapular region. Management must include patient education, postural correction, and an exercise program to address the multiple nerve compression levels and muscle imbalance.

RESULTS AND CONCLUSIONS

The etiology of work related neuromusculoskeletal disorders is multifactorial and successful management must address all contributing factors. Appropriate conservative management will relieve symptoms in most patients. Surgery should be reserved for those few patients with evidence of a specific diagnosis who have failed conservative management.

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.

Sphygmomanometer-induced increases in forearm and hand volume

Swelling, or increased volume, secondary to venous congestion is thought to be a factor in some upper limb conditions. This study aimed to establish a safe, easily applied method of inducing a transitory increase in forearm and hand volume that could be used as a symptom provocation test for upper limb conditions. Using the principles of venous occlusion plethysmography, movement of blood volume into the forearm and hand of asymptomatic subjects was measured after occlusion with three different sphygmomanometer cuff pressures over four minutes. Increases of between 37 and 62 ml (2.5% and 4.1%) were achieved at pressures between diastolic pressure minus 30 mm Hg and diastolic pressure plus 5 mm Hg, with minimal reported side effects. These data demonstrate that a sphygmomanometer can be used to induce transitory fluid congestion of the forearm and hand.

Clinical management of carpal tunnel syndrome: a 12-year review of outcomes

Carpal tunnel syndrome (CTS) is a disorder frequently encountered by occupational health care specialists. The health care management of this disorder has involved a diverse set of clinical procedures. The present article is a review of the literature related to CTS with an emphasis on occupational-related CTS. MEDLINE, Cumulative Index to Nursing and Allied Health Literature, PsycLIT, and NIOSHTIC databases from 1985-1997 were searched for treatment outcome studies related to CTS. Treatments of interest included surgery, physical therapy, drug therapy, chiropractic treatment, biobehavioral interventions, and occupational rehabilitation. A systematic review of the effects of these interventions on symptoms, medical status, function, return to work, psychological well-being, and patient satisfaction was completed. Compared to other treatments, the majority of studies assessed the effects of surgical interventions. Endoscopic release was associated with higher levels of physical functioning and fewer days to return to work when compared to open release. Limited evidence indicated: 1) steroid injections and oral use of B6 were associated with pain reduction; 2) in comparison to splinting, range of motion exercises appeared to be associated with less pain and fewer days to return to work; 3) cognitive behavior therapy yielded reductions in pain, anxiety, and depression; and, 4) multidisciplinary occupational rehabilitation was associated with a higher percentage of chronic cases returning to work than usual care. Workers' compensation status was associated with increased time to return to work following surgery. Conclusions are preliminary due to the small number of well-controlled studies, variability in duration of symptoms and disability, and the broad range of reported outcome measures. While there are several opinions regarding effective treatment, there is very little scientific support for the range of options currently used in practice. Despite the emerging evidence of the multivariate nature of CTS, the majority of outcome studies have focused on single interventions directed at individual etiological factors or symptoms and functional limitations secondary to CTS.

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).

Occupational upper extremity disorders in the federal workforce. Prevalence, health care expenditures, and patterns of work disability

Upper extremity disorders (UEDs) account for a significant number of work-related illnesses in the US workforce. Little information exists on the distribution of UEDs, their associated health care and indemnity costs, or patterns of work disability. The study presented is an analysis of upper extremity claims within the federal workforce. In this study, the universe consisted of all claims accepted by the US Department of Labor, Office of Workers' Compensation Programs (OWCP), from October 1, 1993, through September 30, 1994. A total of 185,927 claims of notices of injury were processed during the study period, and of these, 8,147 or 4.4% had an UED diagnosis coded according to the International Classification of Diseases, Clinical Modification (ICD-9-CM). 5,844 claims involved a single UED diagnosis and were the only claims field by these employees between October 1, 1990, and September 30, 1994. These single claims with single diagnoses comprised the sample for further analysis. Mononeuritis and enthesopathies of the upper limb were the most common diagnoses, accounting for 43% and 31% of the claims, respectively. Women had a higher proportion of carpal tunnel syndrome, "unspecified" mononeuritis, and "unspecified" enthesopathies. The majority of claimants for both the mononeuritis- and enthesopathy-related diagnoses were between 31 and 50 years of age, received only health care benefits, and did not incur wage loss. Health care costs for mononeuritis and enthesopathy claims were $12,228,755 (M = $2,849). Carpal tunnel syndrome (CTS) and enthesopathy of the elbow were the most costly diagnoses, accounting for 57% and 16% of the total, respectively. Surgical services represented the highest expenditures in CTS claims. Physical therapy accounted for the majority of health care costs for enthesopathy cases. The mean number of workdays lost for CTS and enthesopathy claims were 84 and 79, and the average indemnity costs were $4,941 and $4,477, respectively. These findings indicate that while UEDs represent a relatively small percentage of all workers' compensation cases, the health care and indemnity costs are considerable. Also mean duration and pattern of work disability revealed that these disorders can result in chronic work disability similar to that observed in low back pain. The results highlight the need to determine whether interventions that account for the majority of costs significantly impact long-term outcomes. There is also a need to identify risk factors for prolonged disability in those who experience problems with delayed recovery.

Changes in carpal tunnel pressures following endoscopic carpal tunnel release: a cadaveric study

The purpose of this experiment was to determine the amount of tissue that must be sectioned to adequately decompress the median nerve during an endoscopic carpal tunnel release procedure. In 6 fresh cadaver forearms, 2 balloons were inserted into the carpal tunnel. The first balloon was filled with saline solution to cause an initial carpal intracanal pressure of 50 mmHg. Pressure measurements were recorded, using the second balloon, at various increments of the flexor retinaculum division at 3 wrist positions (neutral, 35 degrees ; flexion, 35 degrees extension). At all increments of sectioning, carpal tunnel pressures in the neutral wrist position were consistently lowest and the values in 35 degrees extension were greatest. At each wrist flexion/extension angle, the pressure statistically decreased during incremental division of the flexor retinaculum. Incomplete release of the transverse carpal ligament resulted in incomplete decompression in the canal. Sectioning the overlying aponeurosis caused a further significant decrease in intracanal 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.