Lumbrical muscle incursion into the carpal tunnel during finger flexion

Association Between Thenar Musculature and Carpal Tunnel Syndrome

Background: Dynamic forces acting on the transverse carpal ligament (TCL) may influence the mechanics of the carpal tunnel (CT), thus affecting the occurrence of CT syndrome (CTS). Previous studies demonstrated an association between muscle overlying the CT and the diagnosis of CTS. Understanding the location of insertion/origin of the thenar musculature will allow mechanical analysis of the forces applied to the TCL during performance of individual tasks. Our purpose was to determine the location of muscle overlying the CT on magnetic resonance imaging (MRI) in CTS and controls. Methods: Case-control study of 21 normal adult wrist MRI scans. MRI measurements were performed on an axial cut at the level of the hook-of-hamate. Median nerve cross-sectional area (CSA), median nerve shape and increased signal intensity within the CT were associated with CTS. The amount and length of muscle crossing the midline and the CT on the same cut was measured and the association with the occurrence of CTS was analysed. Results: We found an inverse relationship between the amount of muscle crossing the midline and the size of the CT, and a direct relationship with occurrence of CTS p less than 0.01, but no differences regarding length of muscle crossing the midline. Conclusions: This study supports an association between the thenar musculature location relative to the CT and the predictors of CTS on MRI. Since the location of muscle origin/insertion is variable, their effect may differ accordingly, therefore, further study is needed to describe the exact location of origin/insertion and its differential dynamic or static effect on the pathogenesis of CTS. Level of Evidence: Level IV (Diagnostic).

Carpal tunnel syndrome

Median neuropathy at the wrist, commonly referred to as carpal tunnel syndrome (CTS), is the most common entrapment neuropathy. It is caused by chronic compression of the median nerve at the wrist within the space-limited carpal tunnel. Risk factors that contribute to the etiology of compression include female gender, obesity, work-related factors, and underlying medical conditions, such as hypothyroidism, pregnancy, and amyloidosis. The diagnosis is made on clinical grounds, although these can be confounded by anatomical variations. Electrodiagnostic studies, which are specific and sensitive in diagnosing CTS, support the diagnosis; however, a subgroup may present with normal results. The advent of imaging techniques, including ultrasound and MRI, further assists the diagnostic process. The management of CTS is divided into the nonsurgical approaches that include hand therapy, splinting and corticosteroid injection, and surgical decompression of the carpal tunnel. Although several surgical techniques have been developed, no one method is more effective than the other. Each of these management approaches are effective at providing symptom relief and are utilized at different severities of the condition. There is, however, a lack of consensus on standardized diagnostic criteria, as well as when and to whom to refer patients for surgery.

Anatomical considerations of US-guided carpal tunnel release in daily clinical practice

Carpal tunnel syndrome is the most frequent compression neuropathy with an incidence of one to three subjects per thousand. As specific anatomical variations might lead to unintended damage during surgical interventions, we present a review to elucidate the anatomical variability of the carpal tunnel region with important considerations for daily clinical practice: several variants of the median nerve branches in and around the transverse carpal ligament are typical and must - similarly to the variant courses of the median artery, which may be found eccentric ulnar to the median nerve - be taken into account in any interventional therapy at the carpal tunnel. Unintended interference in these structures might lead to heavy arterial bleeding and, in consequence, even underperfusion of segments of the median nerve or, if neural structures such as variant nerve branches are impaired or even cut, severe pain-syndromes with a profound impact on the quality of life. This knowledge is thus crucial for outcome- and safety-optimization of different surgical procedures at the volar aspect of the wrist and surgical therapy of the carpal tunnel syndrome e.g., US-guided carpal tunnel release, as injury might result in dysfunction and/or pain on wrist motion or direct impact in the region concerned. For most variations, anatomical and surgical descriptions vary, as official classifications are still lacking.

Grip force makes wrist joint position sense worse

Background

The purpose of this study was to investigate how grip force affects wrist joint position sense.

Methods

Twenty-two healthy participants (11 men and 11 women) underwent an ipsilateral wrist joint reposition test at 2 distinct grip forces [0 and 15% of maximal voluntary isometric contraction (MVIC)] and 6 different wrist positions (pronation 24°, supination 24°, radial deviation 16°, ulnar deviation 16°, extension 32°, and flexion 32°).

Results

The findings demonstrated significantly elevated absolute error values at 15% MVIC (3.8 ± 0.3°) than at 0% MVIC grip force [3.1 ± 0.2°, t(20) = 2.303, P = 0.032].

Conclusion

These findings demonstrated that there was significantly worse proprioceptive accuracy at 15% MVIC than at 0% MVIC grip force. These results may contribute to a better comprehension of the mechanisms underlying wrist joint injuries, the development of preventative measures to lower the risk of injuries, and the best possible design of engineering or rehabilitation devices.

Carpal tunnel mechanics and its relevance to carpal tunnel syndrome

The carpal tunnel is an elaborate biomechanical structure whose pathomechanics plays an essential role in the development of carpal tunnel syndrome. The purpose of this article is to review the movement related biomechanics of the carpal tunnel together with its anatomical and morphological features, and to describe the pathomechanics and pathophysiology associated with carpal tunnel syndrome. Topics of discussion include biomechanics of the median nerve, flexor tendons, subsynovial tissue, transverse carpal ligament, carpal tunnel pressure, and morphological properties, as well as mechanisms for biomechanical improvement and physiological restoration. It is our hope that the biomechanical knowledge of the carpal tunnel will improve the understanding and management of carpal tunnel syndrome.

Coexistence of anomalous muscle, persistent median artery, bifid median nerve causing carpal tunnel syndrome: A case report and literature review

Carpal tunnel syndrome (CTS) is an upper extremity median nerve entrapment disorder that is rare in children and adolescents. Anatomical variations of the wrist, such as anomalous muscles, persistent median artery (PMA), and bifid median nerves (BMN), are rare etiology of CTS. Coexistence of all three variants combined with CTS in adolescents has been rarely reported. Case description: A 16-year-old right-hand dominant male presented to our clinic with several years of bilateral thenar muscle atrophy and weakness but no paresthesia or pain in his both hands. Ultrasonography showed that the right median nerve become significantly thinner, and the left median nerve was split into two branches by PMA. Magnetic resonance imaging (MRI) revealed that anomalous muscles in the bilateral wrist extending to the carpal tunnel, causing compression of the median nerve. Considering the possibility of CTS clinically, the patient underwent bilateral open carpal tunnel release without resection of anomalous muscles and PMA. The patient has no discomfort after 2 years. This suggests that anatomical variations of the carpal tunnel may contribute to CTS, which can be confirmed by preoperative ultrasonography and MRI, and the possibility of carpal tunnel anatomical variations should be considered when CTS occurs in adolescents. Open carpal tunnel release is an effective treatment for juvenile CTS without the need to resect abnormal muscle and PMA during the operation.

How to Differentiate Pronator Syndrome from Carpal Tunnel Syndrome: A Comprehensive Clinical Comparison

The diagnostic process that allows pronator syndrome to be differentiated reliably from carpal tunnel syndrome remains a challenge for clinicians, as evidenced by the most common cause of pronator syndrome misdiagnosis: carpal tunnel syndrome. Pronator syndrome can be caused by compression of the median nerve as it passes through the anatomical structures of the forearm, while carpal tunnel syndrome refers to one particular topographic area within which compression occurs, the carpal tunnel. The present narrative review is a complex clinical comparison of the two syndromes with their anatomical backgrounds involving topographical relationships, morphology, clinical picture, differential diagnosis, and therapeutic options. It discusses the most frequently used diagnostic techniques and their correct interpretations. Its main goal is to provide an up-to-date picture of the current understanding of the disease processes and their etiologies, to establish an appropriate diagnosis, and introduce relevant treatment benefiting the patient.

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.

The Pathological Links between Adiposity and the Carpal Tunnel Syndrome

An association between obesity and carpal tunnel syndrome is found in many epidemiological studies. Therefore, there is a need to evaluate the physiopathological links that could explain the association between these two entities. Ectopic adipose tissue is responsible for metabolic syndrome and inflammation, and is a major risk factor for diabetes and cardiovascular diseases. Taking these elements into consideration, we conducted an extensive literature revision of the subject, considering as ectopic fat-related mechanisms the following: (a) the direct compression and the association with the metabolic syndrome of the fat deposition around the wrist, (b) the insulin resistance, dyslipidemia, inflammatory, and oxidative mechanisms related to the central deposition of the fat, (c) the impaired muscle contraction and metabolism related to myosteatosis. Each section presents the cellular pathways which are modified by the ectopic deposition of the adipose tissue and the impact in the pathogeny of the carpal tunnel syndrome. In conclusion, the experimental and clinical data support the epidemiological findings. Efforts to reduce the obesity epidemics will improve not only cardio-metabolic health but will reduce the burden of the disability-free life expectancy due to the carpal tunnel syndrome.

Palmar Musculature: Does It Affect the Development of Carpal Tunnel Syndrome? A Pilot Study

Background  The etiology of carpal tunnel syndrome (CTS) is multifactorial. Static mechanical characteristics of CTS have been described, but dynamic (muscular) parameters remain obscure. We believe that musculature overlying the transverse carpal ligament may have an effect on carpal tunnel pressure and may explain the prevalence of CTS in manual workers. Questions/Purposes  To utilize magnetic resonance imaging (MRI) imaging to estimate the amount of muscle crossing the area of the carpal tunnel and to compare these MRI measurements in patients with and without documented CTS. Methods  A case-control study of wrist MRI scans between January 1, 2018, and December 1, 2019, was performed. Patients with a diagnosis of CTS were matched by age and gender with controls without a diagnosis of CTS. Axial MRI cuts at the level of the hook of the hamate were used to measure the thenar and hypothenar muscle depth overlying the carpal tunnel. Muscle depth was quantified in millimeters at three points: midcapitate, capitate-hamate border, capitate-trapezoid border. Average depth was calculated by dividing the cross-sectional area (CSA) by the transverse carpal ligament width. Statistical analysis included Student's t -test, chi-square test, and Pearson's correlation coefficient calculation. Results  A total of 21 cases and 21 controls met the inclusion criteria for the study. There were no significant differences in demographics between case and control groups. The location and depth of the musculature crossing the carpal tunnel were highly variable in all areas evaluated. A significantly positive correlation was found between proximal median nerve CSA and muscle depth in the capitate-hamate area (correlation coefficient = 0.375; p  = 0.014). CSA was not significantly associated with chart documented CTS. Conclusions  We found large variability in our measurements. This likely reflects true anatomical variation. The significance of our findings depends on the location of the muscles and the line of pull and their effect on the mechanics of the transverse carpal ligament. Future research will focus on refining measurement methodology and understanding the mechanical effect of the muscular structure and insertions on carpal tunnel pressure. Level of Evidence  This is a Level 3, case-control study.

Proximal Median Nerve Compression: Pronator Syndrome

Pronator syndrome (PS) is a compressive neuropathy of the median nerve in the proximal forearm, with symptoms that often overlap with carpal tunnel syndrome (CTS). Because electrodiagnostic studies are often negative in PS, making the correct diagnosis can be challenging. All patients should be initially managed with nonsurgical treatment, but surgical intervention has been shown to result in satisfactory outcomes. Several surgical techniques have been described, with most outcomes data based on retrospective case series. It is essential for clinicians to have a thorough understanding of median nerve anatomy, possible sites of compression, and characteristic clinical findings of PS to provide a reliable diagnosis and treat their patients.

Physical Therapy and Rehabilitation Approaches in Patients with Carpal Tunnel Syndrome

Physical therapy involves a set of factors and methods that affect the biological processes in the body. It is widely used, relatively inexpensive, non-invasive, and easy to apply. Physiotherapy is also used in the treatment of patients with carpal tunnel syndrome (CTS). This syndrome represents the most common compressive mononeuropathy of the upper limb and leads to significant disability. Hence, its successful treatment leads to significant benefits for both the patient and society. There is no established algorithm for the use of physical therapy in these patients. In this publication, we present the physiotherapeutic methods used for the treatment of CTS both before and after surgical treatment.

Lumbrical Tear in Major League Baseball Player Throwing 4-Seam Fastballs: A Case Report

CASE

We present the case of a major league pitcher with persistent finger pain, loss of pitch control, and loss of pitch velocity after an injury during a game. This pitcher only throws fastballs and prefers to only use a 4-seam technique. On examination of the affected hand, it is found that he had tenderness along the palmar iinterosseous near the base of the third metacarpal and no tenderness along the distribution of the flexor digitorum profundus (FDP) tendon. The patient had full range of motion of the third digit. Magnetic resonance imaging revealed partial thickness tears of the second and third lumbricals.

DISCUSSION

Proposed injury was secondary to the 4-seam fastball technique, which pulls apart the FDP of the second and third digit, as well as the FDP of third and fourth digit. This increases the distance between the origins of the second and third lumbricals, leading to strain and tearing. The increased pitch count of the player also may have contributed to the injury. After rest and gradual tossing program, the pitcher was able to return to a preinjury level of function at 6 weeks. One year out from injury, the patient continued to pitch and remained pain free.

Identification of Aberrant Muscle Bellies in the Carpal Tunnel using Sonography

Musculoskeletal sonography is being widely used for evaluation of structures within the carpal tunnel. While some anatomical variants, such as bifurcated median nerves and persistent median arteries, have been well documented, limited literature describes the sonographic appearance of aberrant muscle bellies within the carpal tunnel. Multiple examples of the sonographic appearance of flexor digitorum superficialis and lumbrical muscle bellies extending into the carpal tunnel are provided. Techniques for static image acquisition and analysis are discussed, and the use of dynamic imaging to confirm which specific muscle belly is involved is described. Knowledge of the potential presence of muscle bellies in these images and ability to identify these structures is vital to avoid misclassification or misdiagnosis as abnormal pathology. The case examples are situated among current published evidence regarding how such anomalies may be related to the development of pathologies, such as carpal tunnel syndrome.

Comprehensive Review of the Elbow Physical Examination

Physical examination of the elbow is a critical component in formulating an accurate diagnosis. Various special physical examinations have been described to improve the clinician's ability to establish an accurate diagnosis. A comprehensive approach to the physical examination of the elbow, including special tests, may facilitate improved diagnosis of elbow pathology.

Motor Examination in the Diagnosis of Carpal Tunnel Syndrome

The relative importance and use of motor evaluation to diagnose carpal tunnel syndrome (CTS) is not clear. Because the ulnar nerve is not affected in CTS, we evaluated comparing the strength of the median-nerve innervated muscles to the ulnar innervated muscles in the same patient, through manual muscle testing (MMT) and a handheld dynamometer. Our purpose was to evaluate whether this method, which takes into account patient-dependent factors that would affect both groups of muscles equally, can provide better assessment of CTS. A retrospective case-control review of MMT and dynamometer-measured strength for CTS was performed. The study was performed retrospectively but prior to surgery or other treatment. There were 28 cases (CTS) and 14 controls (without CTS). Positive nerve conduction tests defined cases. MMT of the thenar musculature was found to be unreliable as a test for CTS. Comparisons to ulnar nerve innervated muscle strength did not improve sensitivity or specificity of the MMT examination. Use of the dynamometer improved sensitivity and specificity of motor testing in CTS over MMT. Motor evaluation is important for the diagnosis of CTS, but further study is warranted, specifically to define the method of motor evaluation and delineate the subgroup of patients (predominantly thenar motor presentation) that would benefit most from motor testing and motor-focused treatment.

The Biomechanical Impact of Digital Loss and Fusion Following Trauma: Setting the Patient up for Success

Surgeons managing mutilating hand injures are faced with difficult decisions between attempting to salvage remaining or injured digits or proceeding to amputation and fusion. Through application of a basic understanding of hand biomechanics, the surgeon may more accurately predict what motion and function can best be salvaged. This article provides an explanation of how amputation, fusion, and tendon loss can affect postoperative hand motion. The surgeon can use these concepts in planning the reconstruction or preparing the foundation for secondary reconstructive procedures to achieve the highest functional outcome for the patient.

Comparison of the efficacy of a neutral wrist splint and a wrist splint incorporating a lumbrical unit for the treatment of patients with carpal tunnel syndrome

BACKGROUND

Different types of splints have been used as a conservative intervention to improve symptoms in patients with Carpal tunnel syndrome (CTS). Although a number of studies have been undertaken to compare different splints, information and understanding of the influence of these interventions are lacking.

OBJECTIVES

The purpose of this study was to compare the effect of a classic thermoplastic wrist splint or a wrist splint with an additional metacarpophalangeal unit on pain, function, grip strength, and pinch strength in patients with mild-to-moderate carpal tunnel syndrome.

STUDY DESIGN

Quasi experimental design.

METHODS

A total of 24 patients received conservative treatment using either the classic wrist splint or the wrist splint with the metacarpophalangeal unit for a period of 6 weeks. Primary outcome measures were pain, function, grip strength, and pinch strength. Data were collected immediately before and after using the two types of splints at baseline (0 weeks) and 6 weeks. Statistical analysis was performed using the paired t-test and an independent t-test.

RESULTS

Compared to baseline, both the classic thermoplastic wrist splint and the wrist splint with a metacarpophalangeal unit significantly decreased pain and increased function, pinch strength, and grip strength. Comparisons of the two types of splints for grip strength (P = 0.675) and pinch strength (P = 0.650) revealed that there were no significant differences between the two after 6 weeks of wear. However, there were significant differences in pain levels (P = 0.022) and the Disability of the Arm, Shoulder, and Hand score (P = 0.027) between the two types of splints from baseline to 6 weeks.

CONCLUSION

The wrist splint with a metacarpophalangeal unit was more effective than the classic thermoplastic wrist splint in pain reduction and improvement of function.

CLINICAL RELEVANCE

A wrist splint with a metacarpophalangeal unit may be an appropriate conservative treatment in the rehabilitation of patients with mild-to-moderate carpal tunnel syndrome.

Effects of grip force on median nerve deformation at different wrist angles

The present study investigated the effects of grip on changes in the median nerve cross-sectional area (MNCSA) and median nerve diameter in the radial-ulnar direction (D1) and dorsal-palmar direction (D2) at three wrist angles. Twenty-nine healthy participants (19 men [mean age, 24.2 ± 1.6 years]; 10 women [mean age, 24.0 ± 1.6 years]) were recruited. The median nerve was examined at the proximal carpal tunnel region in three grip conditions, namely finger relaxation, unclenched fist, and clenched fist. Ultrasound examinations were performed in the neutral wrist position (0°), at 30°wrist flexion, and at 30°wrist extension for both wrists. The grip condition and wrist angle showed significant main effects (p < 0.01) on the changes in the MNCSA, D1, and D2. Furthermore, significant interactions (p < 0.01) were found between the grip condition and wrist angle for the MNCSA, D1, and D2. In the neutral wrist position (0°), significant reductions in the MNCSA, D1, and D2 were observed when finger relaxation changed to unclenched fist and clenched fist conditions. Clenched fist condition caused the highest deformations in the median nerve measurements (MNCSA, approximately -25%; D1, -13%; D2, -12%). The MNCSA was significantly lower at 30°wrist flexion and 30°wrist extension than in the neutral wrist position (0°) at unclenched fist and clenched fist conditions. Notably, clenched fist condition at 30°wrist flexion showed the highest reduction of the MNCSA (-29%). In addition, 30°wrist flexion resulted in a lower D1 at clenched fist condition. In contrast, 30°wrist extension resulted in a lower D2 at both unclenched fist and clenched fist conditions. Our results suggest that unclenched fist and clenched fist conditions cause reductions in the MNCSA, D1, and D2. More importantly, unclenched fist and clenched fist conditions at 30°wrist flexion and 30°wrist extension can lead to further deformation of the median nerve.

Education, night splinting and exercise versus usual care on recovery and conversion to surgery for people awaiting carpal tunnel surgery: a protocol for a randomised controlled trial

INTRODUCTION

Carpal tunnel syndrome (CTS) is a prevalent upper limb condition that results in significant individual and socioeconomic costs. Large patient numbers, long outpatient waiting times and traditional referral pathways in public health systems create delays in accessing treatment for this condition. Alternative care pathways aimed at streamlining access to treatment and reducing the need for surgical intervention warrant further investigation.

METHODS

A randomised, single-blind controlled clinical trial will be conducted. 128 participants aged 18-75 years with CTS will be recruited from the carpal tunnel surgery waitlists of participating public hospitals. Suitable participants will be stratified for severity and randomly allocated to either receive therapy (education, provision of splints and a home exercise programme) or standard care (continuing on the waitlist without hand therapy intervention for the duration of the study). Outcomes will be measured at baseline and after 6 weeks and 6 months. Primary outcomes are conversion to surgery ratio and perceived effect via the Global Rating of Change Scale.Secondary measures include patient satisfaction, and monitoring of symptoms and function using outcome measures including the Boston CTS Questionnaire, Disability of Arm, Shoulder and Hand Questionnaire, Patient-Specific Functional Scale, patient completed diagram of symptoms and Self-reported Leeds Assessment of Neuropathic Symptoms and Signs pain scale.

DISCUSSION

This paper outlines the design and rationale for a randomised controlled trial that aims to assess the efficacy of an alternative care pathway for the management of patients with CTS while on the surgery waitlist. It is anticipated that the outcomes of this study will contribute to improved and expedited management of this common condition in a public hospital setting.

ETHICS AND DISSEMINATION

Ethics approval was granted by the Princess Alexandra Hospital Centres for Health Research (HREC/13/QPAH/434-SSA/13/QPAH/447) and the Medical Research Ethics Committee at the University of Queensland. Results will be disseminated via conferences and peer-reviewed publications.

TRIAL REGISTRATION NUMBER

ACTRN12613001095752.

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.

Muscle intrusion as a potential cause of carpal tunnel syndrome

INTRODUCTION

The aim of this study was to determine whether there is an association between flexor digitorum and lumbrical muscle intrusion into the carpal tunnel and carpal tunnel syndrome (CTS).

METHODS

Five hundred thirteen manual laborers (1026 wrists) were evaluated with ultrasound to determine whether those with CTS had more muscle intrusion into the carpal tunnel than those without CTS. One hundred ninety of the participants without CTS at baseline (363 wrists) were followed over 1 year to determine whether muscle intrusion at baseline predicted the development of CTS.

RESULTS

Participants with CTS had more muscle within the carpal tunnel with the wrist in the neutral (P=0.026) and flexed (P=0.018) positions than those without CTS. Baseline muscle intrusion did not predict development of CTS at 1 year.

CONCLUSIONS

Muscle intrusion into the carpal tunnel is associated with CTS, but muscle intrusion alone does not predict the development of CTS over the course of a year.

Longitudinal design for sonographic measurement of median nerve swelling with controlled exposure to physical work using an animal model

In the study described here, we examined the feasibility of a longitudinal design to measure sonographically swelling of the median nerve caused by controlled exposure to a work task and to evaluate the relationship of changes in morphology to diagnostic standards. Fifteen macaques, Macaca fascicularis, pinched a lever in various wrist positions at a self-regulated pace (8 h/d, 5 d/wk, 18-20 wk). Nerve conduction velocity (NCV) and cross-sectional area (CSA) were measured every 2 wk from baseline through working and a 6-wk recovery. Trending across all subjects revealed that NCV slowed and CSA at the carpal tunnel increased in the working arm, whereas no changes were observed in CSA either at the forearm or for any measure in the non-working arm. There was a small negative correlation between NCV and CSA in the working arm. This study provides validation that swelling can be observed using a longitudinal design. Longitudinal human studies are needed to describe the trajectory of nerve swelling for early identification of median nerve pathology.

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

Purpose

The purpose of this study was to compare the properties of the median nerve and the flexor retinaculum within the carpal tunnel with Magnetic Resonance Imaging (MRI) under two conditions: (a) fingers extended, and (b) fingers in an isometric squeeze grip.

Methods

Thirty-Four volunteers participated in this experimental study. The flexor retinaculum and median nerve characteristics were measured during both conditions using MRI.

Results

The isometric squeeze grip condition resulted in significant palmar bowing of the flexor retinaculum (t = 7.67, p<.001), a significant flattening-ratio of the median nerve (t = 4.308, p<.001), and no significant decrease in the cross-sectional area of the median nerve (t = 2.508, p = 0.017).

Conclusion

The isometric squeeze grip condition resulted in anatomical deformations within the carpal tunnel, possibly explained by the lumbrical muscles incursion into the carpal tunnel during finger flexion.

Changes in the carpal tunnel while wearing the Manu® soft hand brace: a sonographic study

We studied the effect of the Manu(®) soft hand brace, which has been designed to relieve median nerve entrapment in carpal tunnel syndrome. An observational, controlled study was conducted in 10 participants, five with bilateral carpal tunnel syndrome and five controls, using sonography to study changes in the dimensions of the carpal tunnel before and while wearing the brace. An increase in transverse diameter, thinning of the flexor retinaculum, and displacement of the proximal insertion of the lumbrical muscle to the middle finger from the edge of the carpal tunnel were observed in patients while wearing the brace. The changes in the morphology of the carpal tunnel while wearing the Manu(®) support its use as an alternative to a night wrist splint.

Anatomy and function of lumbrical muscles

The lumbrical muscles are unique in having their origin and insertion on tendons. The lumbricals assist in metacarpophalangeal joint flexion; they contribute to interphalangeal joint extension by acting as deflexors of the proximal interphalangeal joint. Anatomically, they are highly specialized in terms of their architectural properties, with a small physiologic cross-sectional area but long fiber length. Their unique properties indicate that they are probably important in fast, alternating movements and fine-tuning digit motion.

Effect of finger position on the median nerve area within the carpal tunnel: an ultrasound imaging study

Introduction

Finger flexion has been suggested to contribute to the aetiology of carpal tunnel syndrome (CTS). The purpose of this study was to measure the immediate effects of finger flexion on the cross-section area of the median nerve (MNA).

Methods

Thirty-one healthy volunteers participated in this experimental study. The MNA was measured at the level of hook of hamate using high-resolution ultrasonography during four different finger positions.

Results

A significant change in MNA during different finger positions was found ( F = 24.149, P < 0.001). The biggest difference in MNA was recorded between full finger extension and forceful finger flexion (mean difference = 1.29 mm2, P < 0.001). An inverse correlation between MNA and finger flexion was found (Pearson's r = −0.348, P = 0.002) where the MNA decreased as fingers moved toward flexion.

Conclusion

Finger flexion resulted in direct decrease in MNA, possibly contributing to median nerve compression.

Clinical implications

Hand therapists need to consider modifying their conservative treatment of CTS by limiting activities that require finger flexion and restricting the movement of the wrist and fingers to restrict finger flexion, thus limiting pressure increase on the median nerve.

Current options for nonsurgical management of carpal tunnel syndrome

Carpal tunnel syndrome (CTS) is the most common of the entrapment neuropathies. Surgical decompression is commonly performed and has traditionally been considered the defnitive treatment for CTS. Conservative treatment options include physical therapy, bracing, steroid injections and alternative medicine. While CTS is often progressive, patients may get better without formal treatment. The resolution of symptoms is not necessarily related to the severity of the clinical findings and self-limited activity is common. The current literature suggests that bracing and corticosteroid injections may be useful in the nonsurgical treatment of CTS, although the benefits may be short term. There is limited evidence regarding the efficacy of other treatments, such as therapy, exercise, yoga, acupuncture, lasers and magnets, and further studies are needed. Surgery is recommended for progressive functional deficits and significant pain.

Comparison of a targeted and general massage protocol on strength, function, and symptoms associated with carpal tunnel syndrome: a randomized pilot study

OBJECTIVE

Carpal tunnel syndrome (CTS) is a major, costly public health issue that could be dramatically affected by the identification of additional conservative care treatment options. Our study aimed to evaluate the effectiveness of two distinct massage therapy protocols on strength, function, and symptoms associated with CTS.

DESIGN

This was a randomized pilot study design with double pre-tests and subjects blinded to treatment group assignment.

SETTING/LOCATION

The setting for this study was a wellness clinic at a teaching institution in the United States.

SUBJECTS

Twenty-seven (27) subjects with a clinical diagnosis of CTS were included in the study.

INTERVENTIONS

Subjects were randomly assigned to receive 6 weeks of twice-weekly massage consisting of either a general (GM) or CTS-targeted (TM) massage treatment program.

OUTCOME MEASURES

Dependent variables included hand grip and key pinch dynamometers, Levine Symptom and Function evaluations, and the Grooved Pegboard test. Evaluations were conducted twice during baseline, 2 days after the 7th and 11th massages, and at a follow-up visit 4 weeks after the 12th massage treatment.

RESULTS

A main effect of time was noted on all outcome measures across the study time frame (p < 0.001); improvements persist at least 4 weeks post-treatment. Comparatively, TM resulted in greater gains in grip strength than GM (p = 0.04), with a 17.3% increase over baseline (p < 0.001), but only a 4.8% gain for the GM group (p = 0.21). Significant improvement in grip strength was observed following the 7th massage. No other comparisons between treatment groups attained statistical significance.

CONCLUSIONS

Both GM and TM treatments resulted in an improvement of subjective measures associated with CTS, but improvement in grip strength was only detected with the TM protocol. Massage therapy may be a practical conservative intervention for compression neuropathies, such as CTS, although additional research is needed.

Efficacy of a fabricated customized splint and tendon and nerve gliding exercises for the treatment of carpal tunnel syndrome: a randomized controlled trial

OBJECTIVE

To compare the effects of a neutral wrist and metacarpophalangeal (MCP) splint with a wrist cock-up splint, with and without exercises, for the treatment of carpal tunnel syndrome (CTS).

DESIGN

A 2x2x3 randomized factorial design with 3 main factors: splint (neutral wrist and MCP and wrist cock-up), exercise (exercises, no exercise), and time (baseline, 4wk, 8wk).

SETTING

Subjects were evaluated in an outpatient hand therapy clinic.

PARTICIPANTS

Sixty-one subjects with mild to moderate CTS; 51 subjects completed the study.

INTERVENTIONS

There were 4 groups: the neutral wrist and MCP group and the neutral wrist and MCP-exercise group received fabricated customized splints that supported the wrist and MCP joints; the wrist cock-up group and the wrist cock-up-exercise group received wrist cock-up splints. The neutral wrist and MCP-exercise and wrist cock-up-exercise groups also received tendon and nerve gliding exercises and were instructed to perform exercises 3 times a day. All subjects were instructed to wear the assigned splint every night for 4 weeks.

MAIN OUTCOME MEASURES

We used the CTS Symptom Severity Scale (SSS) and the Functional Status Scale (FSS) to assess CTS symptoms and functional status.

RESULTS

Analysis of variance showed a significant main effect for splint and time on the SSS (P<.001, P=.014) and FSS (P<.001, P=.029), respectively. There were no interaction effects.

CONCLUSIONS

Our results validate the use of wrist splints for the treatment of CTS, and suggest that a splint that supports the wrist and MCP joints in neutral may be more effective than a wrist cock-up splint.

An MRI evaluation of carpal tunnel dimensions in healthy wrists: Implications for carpal tunnel syndrome

BACKGROUND

Deviated wrist postures and pinch grip use have been linked to the development of carpal tunnel syndrome and are likely related to the size and shape of the carpal tunnel. The purpose of this study was to quantify carpal tunnel dimensions with changes in wrist posture and pinch grip.

METHODS

Eight healthy volunteers (4 male, 4 female) underwent magnetic resonance imaging of their dominant wrists under seven conditions which included: 30 degrees wrist extension, neutral and 30 degrees flexion (with and without a 10 N pinch force) and a fist with a neutral wrist. Cross-sectional area of the carpal tunnel and its contents were calculated at 3mm increments along the length of the tunnel and integrated to calculate volumes. Ratios were calculated between the contents of the tunnel to the tunnel itself for area and volume.

FINDINGS

The use of a correction factor significantly reduced volume and distal carpal tunnel area in flexed and extended wrists. Carpal tunnel areas were largest in neutral and smallest at the distal end with wrist flexion. An extended wrist resulted in the smallest carpal tunnel and content volumes as well as the smallest carpal tunnel content volume to carpal tunnel volume ratios. While men had significantly larger areas and volumes than women for both the carpal tunnel and it contents, there were no differences in ratios between the contents and tunnel size.

INTERPRETATION

A simple correction factor for non-perpendicular magnetic resonance images proved useful in relating volume changes to known pressure changes within the carpal tunnel. More inclusive and detailed evaluation of the carpal tunnel and its contents is required to fully understand mechanisms for median nerve compression in the carpal tunnel.

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.

Severe carpal tunnel syndrome in a patient with juvenile idiopathic arthritis due to proximal migration of hypertrophic lumbrical muscles

We report a new case of pediatric carpal tunnel syndrome in a patient with juvenile rheumatoid arthritis. Symptoms were mainly motor weakness and severe atrophy of the thenar.

Coexistence of multiple anomalies in the carpal tunnel

We determined the frequency of anomalous structures within the carpal tunnels of 89 cadaveric forearm-hand specimens. We also examined these same specimens for variations in the branching pattern of the median nerve, and analyzed the range in length and width of the lumbricals. Many of the hands contained extra tendinous slips from the long flexors within the tunnel, subligamentous thenar branches of the median nerve, or lumbricals with bipennate origins. Only one hand had an anomalous muscle belly within the tunnel, two had persistent median arteries, two had high division of the median nerve in the distal forearm, and eight had lumbricals with lengths or widths that were greater or less than 2 standard deviations (SD) from the mean. Twenty-nine percent of all hands examined had two to five anomalies/variations per tunnel, whereas another 27% had one anomaly or variation per tunnel. More right hands (17%) than left (11%) contained two to five anomalous/variant structures per carpal tunnel. More right hands (19%) than left (8%) contained only one variant/anomalous structure per carpal tunnel. Anticipation of the frequency and multiplicity of anomalous structures and variations within this region is of importance to clinicians, particularly surgeons.

Ergonomic Pain--Part 2: Differential Diagnosis and Management Considerations

Work-related musculoskeletal disorders (MSDs) can produce ergonomic pain in several different regions of the body, including the shoulder, elbow, wrist and hand, lumbar spine, knee, and ankle/foot. Each family of disorders is distinctive in presentation and requires diagnosis-specific interventions. Because of the complex nature of these disorders, management approaches may not always eliminate symptoms and or completely restore patient function to a level found prior to symptom onset. As a consequence, ergonomic measures should be implemented to reduce the overload on tissue and contribute to patient recovery. However, functional limits may persist and the clinician must make further decisions regarding a person's functional status in the chronic stages of the patient's care.

Value of some clinical provocative tests in carpal tunnel syndrome: do we need electrophysiology and can we predict the outcome?

Despite the high incidence of CTS, there are no precise diagnostic criteria. The history is useful, but the value of so-called provocative tests is questionable. Electrophysiology is required in the atypical cases; however, it has no prognostic value. There is no good correlation between electrophysiology and symptoms. The outcome seems to be favorable in patients without workmen's compensation, with a mild to moderate impairment preoperatively, and with a favorable response to carpal tunnel infiltration. Postoperatively the electrophysiologic parameters ameliorate symptoms, but this is not correlated to the patient's satisfaction.

Biochemical evaluation of serum and flexor tenosynovium in carpal tunnel syndrome

In total, 41 consecutive patients with "idiopathic carpal tunnel syndrome" and abnormal electrophysiologic findings who underwent carpal tunnel release were studied prospectively. The focus of this investigation was the evaluation of the levels of specific chemical mediators within the serum and flexor tenosynovium of these patients. Blood was collected from these patients within 1 week prior to carpal tunnel release, and flexor tenosynovium was obtained at time of surgery. Specimens were then analyzed to determine the levels of interleukins 1 and 6, prostaglandin E(2) (PGE(2)), and malondialdehyde bis diethyl acetal. These values were compared to those of controls who had no evidence of carpal tunnel syndrome. A significant increase was noted in the serum malondialdehyde and tenosynovial levels of malondialdehyde, interleukin 6, and prostaglandin PGE(2) compared to controls. The elevated levels of these biologic factors and the absence of interleukin 1 elevation support a noninflammatory ischemia-reperfusion etiology for so-called "idiopathic carpal tunnel syndrome" that causes progressive edema and fibrosis of the tissues within the carpal canal. These findings correlate with previous histopathology reports. We believe that "idiopathic carpal tunnel syndrome" is an "-osis" not an "-itis."

Biomechanics and hand trauma: what you need

Mutilating hand trauma presents the surgeon with many reconstructive challenges. This article establishes some biomechanical guidelines to help the surgeon evaluate the hand trauma patient. Through a basic understanding of hand biomechanics, the surgeon may access more accurately what motion and function can best be salvaged. By understanding how amputation, fusion, and tendon loss impact on postoperative hand motion, the surgeon can better focus his or her reconstructive efforts to achieve the highest functional outcome for the patient.

A clinical report of the effect of mechanical stress on functional results after fasciectomy for Dupuytren's contracture

Early postoperative treatment after Dupuytren's fasciectomy traditionally has included the application of mechanical stress to digital extension with splints and exercise. This study examines the effect of mechanical stress, which may compromise nutrient delivery to the tissues, on inflammation, flare, hypertrophic scar, digital range of motion (ROM), and therapy visits. The authors compared functional outcomes in operated digits treated postoperatively with tension applied (TA) and no tension applied (NTA), retrospectively from 1983 to 1993 (TA only) and prospectively from 1993 to 1999 (TA and NTA). The charts of 268 patients who underwent Dupuytren's fasciectomy were reviewed and divided into 2 groups (TA and NTA). Each case was analyzed with respect to age, sex, number of digits operated, postoperative management technique, therapy visits, metacarpophalangeal joint and proximal interphalangeal joint ROM, degree of flare, and scar. There were significant differences in ROM, scar formation, flare, and treatment time in favor of the NTA technique. The results indicate that postoperative management that prevents applied mechanical tension in the early phases of wound healing decreases complications after this surgery and that no digital motion is lost to extension with the NTA technique.

Surgical release of the carpal tunnel

A thorough understanding of the normal anatomy and possible anomalies that may exist is important for the surgeon managing median nerve compression at the wrist. Given the high incidence of anatomic variability occurring in and around the carpal canal, open decompression of the median nerve is the preferred surgical technique for treating carpal tunnel syndrome. This approach provides complete visualization of the region, enabling the surgeon to decompress the nerve thoroughly, identify and treat anatomic abnormalities, and protect important neurovascular structures. Open carpal tunnel release is a safe and reliable operation with a high rate of functional improvement and patient satisfaction.

Biomechanical models for the pathogenesis of specific distal upper extremity disorders

BACKGROUND

Knowledge of the pathogenesis of most disorders that occur in the distal upper extremity is generally lacking. The individual roles of postulated etiologic factors, such as biomechanical or psychosocial exposures, are poorly understood and their potential interactions even less so. This article proposes biomechanical or physiological models of pathogenesis for specific distal upper extremity disorders.

METHODS

Tendon entrapment of the dorsal wrist compartments (tenosynovitis), peritendinitis, lateral epicondylitis, and carpal tunnel syndrome are common specific neuromusculoskeletal disorders of the upper extremities observed among workers. The normal anatomy and function of the targeted structures is considered the initial state; their pathology is considered the final state. Using biomechanical or physiological principles combined with clinical observations and experimental studies, pathways leading from the initial state to the final state are proposed. Each model defined a critical biomechanical or physiological attribute that was considered to best characterize 'dose.' Two temporal patterns of exposure (duration vs. repetition) were used to characterize 'dosage.' The roles of long-term exposure vs. unaccustomed work were mentioned, but not incorporated into the models.

RESULTS

Compressive force transmitted to the extensor retinaculum was considered the critical factor in the model for tendon entrapment at the dorsal wrist compartments. Two models were proposed for lateral epicondylitis. One emphasized the role of eccentric exertions; the other emphasized contact pressure from the radial head. The model for peritendinitis relied on localized muscle fatigue. Seven plausible models were presented for carpal tunnel syndrome.

CONCLUSIONS

It is possible to propose biologically plausible models of pathogenesis that are both coherent with current knowledge of tissue responses and consistent with clinical observations; however, more than one model was plausible for some conditions. Additional research is needed to determine which, if any, of the proposed models might be correct. Such models may be useful to health care providers and ergonomists in the context of primary, secondary, or tertiary prevention.

An innovative hand brace for carpal tunnel syndrome: a randomized controlled trial

We developed a hand brace and studied its efficacy and tolerability in patients with carpal tunnel syndrome (CTS). We randomized 83 subjects into a treated group, which wore the hand brace at night for 4 weeks, and a control group, which received no treatment. The primary efficacy measure was change in the Boston Carpal Tunnel Questionnaire (BCTQ) score. Secondary measures were Subjects' Global Impression of Change Questionnaire (SGICQ), median distal motor latency, sensory conduction velocity and amplitude, and neurophysiological class of severity. The treated group showed a reduction in BCTQ symptomatic score (from 2.75 to 1.54 at 4 weeks; P < 0.001) and functional score (from 1.89 to 1.48; P < 0.001). There were no significant changes in the control subjects. SGICQ documented improvement in all treated subjects (P = 0.006). No significant difference was found in electrophysiological measurements, but overall neurophysiological classification shifted to less severe classes in the treated group (P < 0.05). Thus, the study demonstrates that this hand brace is highly efficient in relieving symptoms and functional loss in CTS.

Flexor muscle incursion into the carpal tunnel: a mechanism for increased carpal tunnel pressure?

PURPOSE

To explore the hypothesis that the extrinsic finger flexor muscles have the potential to move into the proximal end of the carpal tunnel with wrist extension.

METHODS

The most distal muscle fibres from the deep and superficial finger flexors were measured relative to the pisiform bone in 18 cadaveric specimens. Muscle excursions during wrist extension were calculated using regression equations previously reported in the literature.

RESULTS

The mean distances from the pisiform were 9.3 and 4.9 mm for the deep and superficial flexors, respectively. Ten flexor muscle bellies were at the level of or distal to the pisiform bone in the anatomical position, while 17 of 36 were within 5 mm.

DISCUSSION

The excursions expected with wrist extension indicate that many muscles have the potential to enter the carpal tunnel, especially those within 5 mm of the pisiform bone. Comparing the expected excursions to recent pressure data, corroborating support for the pressure increase is found.

CONCLUSION

Although not directly measured, the results of this study indicate incursion of the flexor muscles into the carpal tunnel space, particularly with wrist extension, is a plausible mechanism for increased carpal tunnel pressure.

RELEVANCE

Proposing a mechanism by which carpal tunnel pressure is elevated during wrist and finger extension is a stepping stone to determining the etiology of the disease itself. Finding that the flexor muscle bellies appear to enter the carpal tunnel with wrist extension indicates that use of the flexor muscles should be avoided when the wrist and fingers are extended.

Effects of finger posture on carpal tunnel pressure during wrist motion

Persistent elevations in carpal tunnel pressure may aggravate carpal tunnel syndrome. This study examined the effects of finger posture on carpal tunnel pressure during wrist motion. Carpal tunnel hydrostatic pressure was measured using a saline-filled catheter inserted into the nondominant wrists of 14 healthy individuals. Range of motion tasks of wrist flexion-extension and radioulnar deviation were repeated with metacarpophalangeal (MCP) joint angles of 0 degrees, 45 degrees, and 90 degrees flexion. Pressures were significantly greater with the fingers straight (MCP = 0 degrees) than when the MCP joints were flexed to 45 degrees for all radioulnar deviation angles and from 10 degrees of wrist flexion to all angles of wrist extension tested. Pressures were also significantly higher with MCP joints at 0 degrees than at 90 degrees for wrist extension angles from 10 degrees to 40 degrees. Pressures increased to over 30 mm Hg (4.0 kPa) in some wrist extension and ulnar and radially deviated postures. Finger and wrist postures should be considered when designing splints or evaluating tasks for patients with carpal tunnel syndrome.

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).