Vascular pathologic changes in the flexor tenosynovium (subsynovial connective tissue) in idiopathic carpal tunnel syndrome

Time-varying changes in median nerve deformation and position in response to quantified pinch and grip forces

The ability of the median nerve (MN) to adapt in response to altered carpal tunnel conditions is important to mitigate compressive stress on the nerve. We assessed changes in MN deformation and position throughout the entire time course of hand force exertions. Fourteen right-handed participants ramped up force from 0% to 50% of maximal voluntary force (MVF) before ramping force back down in three different hand force exertion tasks (pulp pinch, chuck pinch, power grip). Pinch and grip forces were measured with a digital dynamometer, which were time synchronized with transverse carpal tunnel images obtained via ultrasound. Ultrasound images were extracted in 10% increments between 0% and 50% MVF while ramping force up (loading phase) and down (unloading phase). MN deformation and position relative to the flexor digitorum superficialis tendon of the long finger were assessed in concert. During loading, the nerve became more circular while displacing dorsally and ulnarly. These changes primarily occurred at the beginning of the hand force exertions while ramping force up from 0% to 20%, with very little change between 20% and 50% MVF. Interestingly, deformation and position changes during loading were not completely reversed during unloading while ramping force down. These findings indicate an initial reorganization of carpal tunnel structures. Mirrored changes in nerve deformation and position may also reflect strain-related characteristics of adjoining subsynovial connective tissue. Regardless, time-varying changes in nerve deformation and position appear to be an important accommodative mechanism in the healthy carpal tunnel in response to gripping and pinching tasks.

Higher densities of T-lymphocytes in the subsynovial connective tissue of people with carpal tunnel syndrome

Symptoms in people with carpal tunnel syndrome (CTS) are traditionally attributed to neural tissue, but recent studies suggest that the subsynovial connective tissue (SSCT) may also play a role in CTS. The SSCT undergoes fibrotic thickening which is generally described as "non-inflammatory" based on basic histology. This study uses immunohistochemistry to determine the presence of macrophages and T-cells within SSCT and their relationship with symptoms in people with CTS. SSCT was collected from twenty people with CTS and eight controls undergoing wrist fracture surgery. Immunohistochemical quantification of CD3+ T-cells and CD68+ macrophage densities as well as CD4+/CD8+ T-cell subpopulations were compared between groups using independent t-tests. Spearman correlations were used to identify associations between immune cell densities and CTS symptom scores. The density of CD3+ T-cells was significantly higher in SSCT of people with CTS compared to controls (CTS mean 26.7 (SD 13.7); controls 6.78 (6.3), p = 0.0005) while the density of CD68+ macrophages was lower (CTS mean 9.5 (SD 6.0); controls 17.7 (8.2), p = 0.0058). Neither CD68+ nor CD3+ cell densities correlated with symptom scores. In contrast to previous assumptions, our data show that the SSCT in the carpal tunnel in both people with CTS and controls is not devoid of immune cells. Whereas the higher density of CD68+ macrophages in control participants may be associated with their early recruitment after acute fracture, CD3+ cells within the SSCT may play a role in chronic CTS.

Cardiovascular Disease Risk Factors Predict the Development and Numbers of Common Musculoskeletal Disorders in a Prospective Cohort

OBJECTIVE

The aim of the study is to assess risk of common musculoskeletal disorders (MSDs) based on cardiovascular disease (CVD) risk scores.

METHODS

Data from a 9-year prospective cohort of 1224 workers in three states were analyzed. Baseline data included questionnaires, structured interviews, physical examinations, anthropometric measurements, nerve conduction studies, and individualized measurement of job physical factors. Monthly follow-ups were conducted. Framingham risk scores were calculated. A priori case definitions were constructed for carpal tunnel syndrome, lateral epicondylopathy, medial epicondylopathy, and rotator cuff tendinopathy.

RESULTS

Adjusted RRs for one or more MSDs increased to 3.90 (95% confidence interval, 2.20-6.90) among those with 10-year cardiovascular disease risk scores greater than 15% and 17.4 (95% confidence interval, 3.85-78.62) among those with more than 4 disorders.

CONCLUSIONS

Cardiovascular disease factors are strongly associated with the subsequent development of common MSDs. Risks among those with multiple MSDs are considerably stronger.

Relative motion between the flexor digitorum superficialis tendon and subsynovial connective tissue is time dependent

The subsynovial connective tissue is an integral component of flexor tendon gliding in the carpal tunnel, which is strained during longitudinal tendon displacement. We tested the effects of repetition frequency and finger load on flexor tendon function throughout active finger movement. Eleven participants performed metacarpophalangeal joint flexion/extension of the long finger cyclically at three repetition frequencies (0.75, 1.00, 1.25 Hz) and two finger loads (3.5, 7 N). Relative displacement between the flexor digitorum superficialis tendon and subsynovial connective tissue was assessed as the shear-strain index with color ultrasound throughout the entire time history of finger flexion and extension. In addition, long finger joint angles were measured with electrogoniometry while flexor digitorum superficialis and extensor digitorum muscle activities were measured with fine-wire electromyography to characterize the finger movements. The shear-strain index increased with greater finger flexion (p = 0.001), representing higher relative displacement between tendon and subsynovial connective tissue; however, no changes were observed throughout finger extension. The shear-strain index also increased with higher repetition frequencies (p = 0.013) and finger loads (p = 0.029), further modulating time-dependent effects during finger flexion versus extension. Using ultrasound, we characterized the time-dependent response of the shear-strain index, in vivo, providing valuable data on flexor tendon function during active finger movement. Our results infer greater subsynovial connective tissue strain and shear during repetitive and forceful finger movements. Future research characterizing time-dependent effects in carpal tunnel syndrome patients may further elucidate the relations between subsynovial connective tissue function, damage, and carpal tunnel syndrome.

Carpal tunnel tendon and sub-synovial connective tissue mechanics are affected by reduced venous return

BACKGROUND

The effects of blood flow occlusion and sex-specific differences in tendon-subsynovial connective tissue relative strain are not well understood. Thus, the purpose of this study was to investigate the influence of blood flow, biological sex, and finger movement speed on carpal tunnel tendon mechanics to further develop our understanding of carpal tunnel syndrome.

METHODS

Colour Doppler ultrasound imaging quantified relative motion between flexor digitorum superficialis tendon and subsynovial connective tissue in 20 healthy male and female participants during repetitive finger flexion-extension under brachial occlusion of blood flow and two movement speeds (0.75 & 1.25 Hz).

FINDINGS

Flexor digitorum superficialis and subsynovial connective tissue displacement decreased with occlusion (small effect) and fast speed (large effect). Speed × Condition interactions were found for mean FDS displacement and peak FDS velocity, where slow speed with occlusion reduced both outcomes. Movement speed had a small but significant effect on tendon-subsynovial connective tissue shear outcomes, where MVR decreased with fast finger motion.

INTERPRETATION

These results suggest the influence of localized edema through venous occlusion on tendon-subsynovial connective tissue gliding within the carpal tunnel. This insight further develops our understanding of carpal tunnel syndrome pathophysiology and suggests ramifications on carpal tunnel tissue motion when the local fluid environment of the carpal tunnel is disturbed.

Potential Relationships between the Median Nerve Cross-Sectional Area and Physical Characteristics in Unilateral Symptomatic Carpal Tunnel Syndrome Patients

Background: The present study investigated the relationships between the median nerve cross-sectional area (CSA) and physical characteristics in patients with unilateral symptomatic carpal tunnel syndrome (CTS). Methods: Height, weight, body mass index (BMI), disease duration, results of electrodiagnostic testing (EDX), and median nerve CSA at the level of the wrist crease were recorded in 81 patients with CTS who presented with symptoms on only one side. Correlation coefficients between median nerve CSA and physical characteristics, disease duration, and results of EDX were analyzed. Results: Median nerve CSA at the wrist crease (mm2) was significantly larger on the symptomatic side (14.1 ± 3.8) than on the asymptomatic side (11.5 ± 2.9). Median nerve CSA correlated with body weight (correlation coefficient = 0.39) and BMI (correlation coefficient = 0.44) on the asymptomatic side, but not on the symptomatic side. These correlations were slightly stronger in females (correlation coefficient = 0.46) than in males (correlation coefficient = 0.40). No correlations between median nerve CSA and disease duration and the results of EDX were observed in both sides. Conclusions: In patients with unilateral symptomatic CTS, median nerve CSA correlated with BMI only on the asymptomatic side. The present results suggest that the relationship between median nerve CSA and BMI in CTS is significant until symptom onset but may be masked by edema and pseudoneuroma after its onset. A higher BMI is associated with a larger CSA of the median nerve, which may be a risk factor for the development of CTS.

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.

Thirty Minutes of Sub-diastolic Blood Flow Occlusion Alters Carpal Tunnel Tissue Function and Mechanics

There is evidence that carpal tunnel syndrome (CTS) development is driven by vascular factors, specifically those resulting from ischemia and edema. The purpose of this study was to investigate the vascular hypothesis of CTS development by quantifying the temporal effects of 30 min of sub-diastolic brachial blood flow occlusion on median nerve edema, intraneural blood flow velocity, nerve function as measured through nerve conduction study (NCS), tendon-connective tissue mechanics and carpal tunnel tissue stiffness. Forty healthy volunteers underwent 30 min of sub-diastolic brachial occlusion while an NCS and ultrasound examination were performed consecutively every 5 min. Motor latency (p < 0.001), sensory conduction velocity (p < 0.001), sensory amplitude (p = 0.04), nerve blood flow (p < 0.001), peak relative flexor digitorum superficialis tendon-sub-synovial connective tissue displacement (p = 0.02) and shear strain (p = 0.04) were significantly affected by partial ischemia. Our results highlight the dependency of carpal tunnel tissue function on adequate blood flow.

Differences in characteristics of carpal tunnel syndrome between male and female patients

BACKGROUND

Sex difference is known to be a risk factor of carpal tunnel syndrome. However, sex differences with regard to the clinical presentation of carpal tunnel syndrome have not received much attention. Thus, this study aimed to detect any difference in the characteristics of carpal tunnel syndrome between male and female and thereby add new insights into disease prevention.

METHODS

A total of 647 patients (male 193 hands and female 454 hands) with carpal tunnel syndrome who underwent endoscopic or open carpal tunnel release were retrospectively reviewed. The average age at time of surgery was 66 years. Clinical and electrophysiological data of all patients were collected. Six medical conditions, including trigger finger, diabetes mellitus, hemodialysis, hyperlipidemia, hypertension, and obesity were also investigated.

RESULTS

A significant difference was found in the distribution of comorbidities between the male and female groups. Particularly, the prevalence of diabetes mellitus, hemodialysis, and hypertension were significantly higher in the male group than in the female group. Meanwhile, the presence of thenar muscle atrophy was significantly higher in the female group than in the male group.

CONCLUSIONS

Women are more likely to experience carpal tunnel syndrome even though they have no comorbidities. We suggest that carpal tunnel syndrome especially in male patients may be reduced by early intervention for diabetes mellitus. Prospective studies are needed to validate the causal relationship between diabetes mellitus and carpal tunnel syndrome.

Mutations in COMP cause familial carpal tunnel syndrome

Carpal tunnel syndrome (CTS) is the most common peripheral nerve entrapment syndrome, affecting a large proportion of the general population. Genetic susceptibility has been implicated in CTS, but the causative genes remain elusive. Here, we report the identification of two mutations in cartilage oligomeric matrix protein (COMP) that segregate with CTS in two large families with or without multiple epiphyseal dysplasia (MED). Both mutations impair the secretion of COMP by tenocytes, but the mutation associated with MED also perturbs its secretion in chondrocytes. Further functional characterization of the CTS-specific mutation reveals similar histological and molecular changes of tendons/ligaments in patients’ biopsies and the mouse models. The mutant COMP fails to oligomerize properly and is trapped in the ER, resulting in ER stress-induced unfolded protein response and cell death, leading to inflammation, progressive fibrosis and cell composition change in tendons/ligaments. The extracellular matrix (ECM) organization is also altered. Our studies uncover a previously unrecognized mechanism in CTS pathogenesis.

Familial carpal tunnel syndrome (CTS) is common, but causal genes are not characterized. Here the authors report two CTS-related mutations in two large families that impair secretion of COMP in tenocytes, leading to ER stress-induced unfolded protein response, inflammation and fibrosis in patients and mouse models.

Location-dependent change of median nerve mobility in the carpal tunnel of patients with carpal tunnel syndrome

INTRODUCTION

The purpose of this study was to investigate in vivo median nerve longitudinal mobility in different segments of the carpal tunnel associated with active finger motion in carpal tunnel syndrome (CTS) patients in a comparison with healthy controls.

METHODS

Eleven healthy volunteers and 11 CTS patients participated in this study. Dynamic ultrasound images captured location-dependent longitudinal median nerve mobility within the carpal tunnel during finger flexion at the metacarpophalangeal joints using a speckle cross-correlation algorithm.

RESULTS

Median nerve longitudinal mobility in the carpal tunnel was significantly smaller in CTS patients (0.0037 ± 0.0011 mm/degree) compared with controls (0.0082 ± 0.0026 mm/degree) (P < .05), especially in the proximal (0.0064 vs 0.0132 mm/degree on average) and middle (0.0033 vs 0.0074 mm/degree on average) carpal tunnel sections.

DISCUSSION

Median nerve mobility can potentially serve as a biomechanical marker when diagnosing CTS, or when assessing the effectiveness of surgical and conservative treatments.

External Compression and Partial Ischemia Decrease Human Finger Flexor Tendon and Subsynovial Connective Tissue Relative Motion

Cumulative shear strain of the subsynovial connective tissue (SSCT) surrounding finger flexor tendons plays a significant role in the development and progression of carpal tunnel syndrome. Biomechanical risk factors can alter tendon-SSCT shear strain but the effects of external mechanical compression and localized ischemia have yet to be investigated. In a laboratory study with 19 healthy participants, color Doppler ultrasound imaging was used to quantify relative motion between the flexor digitorum superficialis tendon and SSCT during repetitive finger flexion-extension under various conditions of external mechanical compression (palmar and forearm compression), ischemia and different movement speeds (0.75 and 1.25 Hz). Forearm compression reduced tendon displacement (baseline = 28.5 ± 4.1 mm vs. forearm = 27.0 ± 4.6 mm; p = 0.043) and showed a trend for reduced SSCT displacement, while palmar compression had no significant effects on tendon-SSCT motion. Compared with baseline, partial ischemia decreased SSCT displacement (baseline = 22.9 ± 3.3 mm vs. ischemia = 22.0 ± 3.3 mm; p = 0.015), while tendon displacement remained unchanged. In all experimental conditions, faster movements elicited greater tendon-SSCT relative motion. Our findings suggest that palmar compression may not negatively impact tendon-SSCT relative motion, but forearm compression may require further investigation. Localized ischemia in the forearm may alter the gliding conditions within the carpal tunnel and affect tendon-SSCT relative motion, which bridges an important gap between blood flow in the carpal tunnel and shear injury risk. These findings contribute to the growing body of literature, supporting the role that cumulative tendon-SSCT shear injury may have on the pathomechanics of carpal tunnel syndrome. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:1038-1044, 2020.

Blood flow velocity but not tendon mechanics relates to nerve function in carpal tunnel syndrome patients

Carpal tunnel syndrome (CTS) develops from chronic compression of the median nerve. Chronic compression results in a number of vascular, structural and functional changes to the carpal tunnel tissues which ultimately manifest in the characteristic symptoms of CTS. The purpose of this study was to investigate the interplay of median nerve function, median nerve hemodynamics, and finger flexor tendon and subsynovial connective tissue (SSCT) mechanics in CTS patients. Thirty-five patients were recruited following nerve conduction study for this double-blinded imaging study. Ultrasound B-mode, pulse-wave Doppler, and colour Doppler images and videos were collected at the proximal carpal tunnel to quantify: (1) median nerve cross-sectional area, (2) intraneural blood flow velocity in 3 wrist postures (neutral (0°), flexion (15°), extension (30°)), and (3) flexor digitorum superficialis and SSCT displacement. Results demonstrate that intraneural blood flow velocity is dependent on median nerve function and wrist posture such that patients with mild CTS are more susceptible to the effects of non-neutral wrist postures. Tendon-SSCT mechanics do not appear to differ based on severity. This study stresses the importance of limiting exposure to non-neutral wrist postures in patients with early signs of the condition.

Role of fasciae around the median nerve in pathogenesis of carpal tunnel syndrome: microscopic and ultrasound study

This study investigated the connections between the median nerve paraneural sheath and myofascial structures near it, from both macroscopic and microscopic points of view. Four samples of median nerve and surrounding tissues were excised from nine non-embalmed upper limbs for microscopic analysis. Ultrasound images were analysed in 21 healthy subjects and 16 carpal tunnel syndrome patients to evaluate median nerve transversal displacement during finger motion at carpal tunnel and forearm levels. An anatomical continuity between epimysium and paraneural sheath and a reduction of paraneural fat tissue from proximal to distal was found in all samples. Median nerve displacements at both levels were significantly reduced in carpal tunnel syndrome subjects (P < 0.001). It was observed that the median nerve is not an isolated structure but is entirely connected to myofascial structures. Therefore, unbalanced tension of epimysial fasciae can affect the paraneural sheath, limiting nerve displacement, and consequently this must be included in carpal tunnel syndrome pathogenesis.

Timing of extracorporeal shock wave therapy in rabbits with carpal tunnel syndrome

The purpose of this study is to evaluate the effect of extracorporeal shock wave therapy (ESWT) according to treatment timing in rabbits with 10% dextrose-induced carpal tunnel syndrome (CTS); 0.1-ml 10% dextrose solution was injected under ultrasound guidance twice weekly to the left forepaw subsynovial connective tissue (SSCT) within the carpal tunnel of 36 New Zealand white rabbits to induce CTS. The rabbits were randomly allocated into four groups: G1-S (sham ESWT), G2-E4 (ESWT at 4 weeks), G3-E8 (at 8 weeks), and G4-E16 (at 16 weeks). Radial ESWT (500 pulses, 0.08 mJ/mm² , 2 Hz) was repeated thrice weekly. Median nerve distal motor latency (DML) was measured before injection and at 4, 8, 12, 16, and 20 weeks after the first injection. All rabbits were sacrificed 20 weeks after injection. The median nerve cross-sectional area (CSA) and SSCT thickness were measured with light microscopy. The mean median nerve DML at 4 weeks after the first dextrose injection did not differ from that at preinjection in all groups. The mean median nerve DML significantly increased before ESWT in all groups (p < .05); however, it did not increase in G2-E4 and G3-E8 for 12 weeks after ESWT and in G4-E16 for 4 weeks (p > .05). Mean CSA of the median nerve and mean SSCT thickness in G2-E4 were significantly lower than those in the other groups (p < .05). ESWT may prevent the progression of CTS for 12 weeks in rabbits with dextrose-induced CTS regardless of treatment timing, and early application results in superior outcomes.

Carpal Tunnel Syndrome: Evaluation of the Effects of Low-Level Laser Therapy With Ultrasound Strain Imaging

OBJECTIVES

To evaluate the efficacy of low-level laser therapy on median nerve stiffness by using strain elastography in carpal tunnel syndrome (CTS).

METHODS

This study included 37 wrists of 34 patients with mild or moderate CTS between January 2016 and August 2016. The control group comprised 17 patients (18 wrists) with CTS who were treated with wrist splinting for 3 weeks. The low-level laser therapy group included 17 patients (19 wrists) with CTS who were treated with a combination of splinting and low-level laser therapy, which was applied 5 times per week for 3 weeks. Clinical assessment scales, including the Symptom Severity Scale (SSS) and Functional Status Score (FSS), were obtained from our database. The cross-sectional area by ultrasound and strain ratio by elastography were studied. The differences in the strain ratio, cross-sectional area, SSS, and FSS between pretreatment and posttreatment periods in the groups were compared by the paired-sample t test. The correlations between changes in the strain ratio and the cross-sectional area, SSS, and FSS were analyzed by Pearson correlation coefficients.

RESULTS

The control group included 13 women and 4 men, and the therapy group included 14 women and 3 men. In the therapy group, the mean values of the strain ratio, cross-sectional area, SSS, and FSS decreased significantly after laser therapy (P < .001) in contrast to the control group. No significant correlation was observed between the decreasing degree of the strain ratio and the cross-sectional area, SSS, and FSS after laser therapy.

CONCLUSIONS

The strain ratio and cross-sectional area of the median nerve decrease after low-level laser therapy. These changes may be related to the therapeutic effects of low-level laser therapy, such as nerve regeneration and improvement of the vascular supply.

The effectiveness of ultrasonography and ultrasonographic elastography in the diagnosis of carpal tunnel syndrome and evaluation of treatment response after steroid injection

PURPOSE

To evaluate if there is a place for ultrasonography (US) and ultrasonographic elastography (UE) in the diagnosis and follow up of carpal tunnel syndrome treatment.

MATERIALS AND METHODS

The study was performed on 25 patients (study group) and 17 healthy volunteers (control group). Measured US and UE criteria were median nerve area (MNA), proximal median nerve area (pMNA), difference between MNA and pMNA (dMNA) and strain values of carpal tunnel content (CTC) and median nerve (MN). Patients in the study group were also evaluated using the Boston questionnaire, Visual Analogue Scale (VAS) and nerve conduction studies. Thirty-three wrists in 23 patients received steroid injections on the same day. Patients were re-evaluated 6 weeks after steroid injection. To establish a cut off value for MNA, ROC Curve analysis was used.

RESULTS

Mean MNA and dMNA values in the control group were significantly lower than in the study group (7.33 ± 1.31 vs. 15.44 ± 5.10; p=<0.05 and 1.58 ± 0.75 vs. 8.91 ± 4.93; p = 0.00 respectively). Median nerve and CTC strain indices were significantly higher in the control group (p = 0.00 and p = 0.036). Decrease in MNA and dMNA values after treatment was meaningful (p = 0.00). While there was no significant change in MN elasticity, mean CTC strain index of the study group (4.680 ± 1.664) decreased significantly after treatment (3.621 ± 1.054 p = 0.002). This decrease in the CTC index was more pronounced in patients who benefited from treatment (p = 0.001).

CONCLUSION

US and UE can be useful in the diagnosis of CTS and its response to treatment, if used together with clinical and electroneurophysiological tests.

Blood Flow Changes in Subsynovial Connective Tissue on Contrast-Enhanced Ultrasonography in Patients With Carpal Tunnel Syndrome Before and After Surgical Decompression

OBJECTIVES

Although qualitative alteration of the subsynovial connective tissue in the carpal tunnel is considered to be one of the most important factors in the pathophysiologic mechanisms of carpal tunnel syndrome (CTS), little information is available about the microcirculation in the subsynovial connective tissue in patients with CTS. The aims of this study were to use contrast-enhanced ultrasonography (US) to evaluate blood flow in the subsynovial connective tissue proximal to the carpal tunnel in patients with CTS before and after carpal tunnel release.

METHODS

The study included 15 volunteers and 12 patients with CTS. The blood flow in the subsynovial connective tissue and the median nerve was evaluated preoperatively and at 1, 2, and 3 months postoperatively using contrast-enhanced US.

RESULTS

The blood flow in the subsynovial connective tissue was higher in the patients with CTS than in the volunteers. In the patients with CTS, there was a significant correlation between the blood flow in the subsynovial connective tissue and the median nerve (P = .01). The blood flow in both the subsynovial connective tissue and the median nerve increased markedly after carpal tunnel release.

CONCLUSIONS

Our results suggest that increased blood flow in the subsynovial connective tissue may play a role in the alteration of the microcirculation within the median nerve related to the pathophysiologic mechanisms of CTS. The increase in the blood flow in the subsynovial connective tissue during the early postoperative period may contribute to the changes in intraneural circulation, and these changes may lead to neural recovery.

Expression of vitamin D receptor in the subsynovial connective tissue in women with carpal tunnel syndrome

Studies suggest that low vitamin D levels are associated with carpal tunnel syndrome. We aimed to evaluate whether level of vitamin D receptor expression in the endothelial cells of the subsynovial connective tissue is associated with clinical features of carpal tunnel syndrome. We obtained the subsynovial connective tissue from 52 women with carpal tunnel syndrome during surgery and performed immunohistochemical analysis of vitamin D receptors in the endothelial cells of the subsynovial connective tissue. We explored correlation of vitamin D receptor expression with clinical features of carpal tunnel syndrome, such as age, symptom duration, symptom severity and electrophysiological severity. Diverse range of vitamin D receptor expression was observed. Vitamin D receptor expression was independently associated with distal motor latency. This suggests that vitamin D receptor expression may be associated with disease progression, as prolonged distal motor latency reflects severity of the disease. Further studies are necessary to explore the role of vitamin D and vitamin D receptors in patients with carpal tunnel syndrome.

LEVEL OF EVIDENCE

IV.

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.

Relaxin Modulates the Expression of MMPs and TIMPs in Fibroblasts of Patients with Carpal Tunnel Syndrome

PURPOSE

The aim of this study was to investigate the anti-fibrotic effect of relaxin in subsynovial fibroblasts activated by transforming growth factor beta (TGF-β).

MATERIALS AND METHODS

To test the anti-fibrotic effect of an adenovirus-relaxin construct (Ad-RLN) on subsynovial fibroblasts in vitro, cells from subsynovial connective tissue of patients with carpal tunnel syndrome were activated with TGF-β1 and exposed to Ad-RLN (as a therapeutic gene) or adenovirus-lacZ construct (as a marker gene) for four hours. Subsynovial fibroblast cultures without adenoviral exposure served as controls.

RESULTS

We observed induction of gene expressions of collagen I, III and IV, as well as the abatement of alpha-smooth muscle actin (a-SMA) synthesis, Smad2 phosphorylation, and fibronectin at the protein level, in comparison to controls. In addition, protein expressions of matrix metalloproteinase (MMP) I was significantly induced, whereas the protein expressions of tissue inhibitor of metalloproteinases (TIMP) I and IV were reduced due to relaxin expression.

CONCLUSION

RLN prevents excessive synthesis of extracellular matrix by reducing the expressions of its components, such as fibronectin, a-SMA, and phosphorylated Smad2, by increasing the expression of MMPs; and by decreasing the expression of TIMPs.

Elevated basal cytosolic calcium of endothelial cells influences the post-surgical outcome in diabetic CTS

Background Type 2 diabetes mellitus (T2DM)-induced neuropathy and ischemia-reperfusion post-surgery prolong carpal tunnel syndrome (CTS) pathology, but the effect of T2DM on the prognostic outcome of carpal tunnel (CT) release surgery needs to be investigated. Materials and methods A total of 64 individuals with CTS underwent CT release surgery. HbA1c levels identified their diabetic status. The individual prognostic outcomes were measured by nerve conduction velocity (NCV), amplitude, and latency. Measurement of [Ca²⁺]_c and reactive oxygen species (ROS) from isolated endothelial cells (ECs) revealed the oxidative burden of the normal and diabetic CTS phenotypes. Results CTS individuals with HbA1c > 7 showed decreased NCV (≈22 m/s) and amplitude (≈4.2 mV) with increased latency (≈6 ms), compared to groups with HbA1c ≤ 7. Further to CT release surgery, the reversal of the nerve conduction to normalcy was greatly influenced by the diabetic profile of the individuals. Our results showed elevated basal [Ca²⁺]_c and corresponding high cytosolic ROS in the ECs isolated from individuals with HbA1c > 7 compared to the diabetic and healthy control groups. Conclusion The individuals with diabetic index showed suboptimal neuronal performance pre- and post-CT release surgery. Oxidative stress mediated by high [Ca²⁺]_c and ROS of ECs dissipates to adjoining cells worsening the pathology of the untreated CTS.

Relative motion between the flexor digitorum superficialis tendon and paratenon in zone V increases with wrist flexion angle

Carpal tunnel syndrome is characterized by non-inflammatory fibrosis of the subsynovial connective tissue (SSCT), a paratenon-like structure inside the carpal tunnel. This pathology suggests repetitive and/or excessive shear forces are involved in injury development. We assessed relative motion between the flexor digitorum superficialis (FDS) tendon and adjacent paratenon in Zone V using colour Doppler imaging as 16 healthy participants completed three long finger movements (metacarpophalangeal joint flexion, proximal and distal interphalangeal joint flexion, full finger flexion) in three wrist postures (30° extension, 0°, 30° flexion). While the type of finger movement did not affect tendon-paratenon relative motion, we found a significant main effect of wrist posture (p < 0.001). Relative displacement between the FDS tendon and paratenon (as a percentage of tendon displacement) increased from 27.2% (95%CI = 24.8-29.5%) in 30° wrist extension to 39.9% (95%CI = 37.3-42.4%) in 30° wrist flexion. Optical motion capture confirmed that wrist posture did not affect metacarpophalangeal joint range of motion (p = 0.265) or proximal interphalangeal joint range of motion (p = 0.582). These results indicate that relative motion increased due to paratenon strain when the wrist was flexed. While our findings agree with previous cadaveric research in wrist flexion, we found that relative displacement decreased in 30° wrist extension (compared to 0°). These results differ from cadaveric research, possibly due to challenges maintaining anatomic fidelity of the viscoelastic paratenon tissue in vitro. Overall, our study suggests a greater susceptibility to shear injury during repetitive finger movements, particularly when the wrist is flexed. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1248-1255, 2016.

Enhanced expression of Wnt9a in the flexor tenosynovium in idiopathic carpal tunnel syndrome

This study aimed to clarify the association between abnormal Wnt signaling and the cause of idiopathic carpal tunnel syndrome (ICTS) and whether an association exists between Wnt signaling and cell proliferation in the flexor tenosynovium. The subjects included nine patients with ICTS; the controls were nine patients with distal radius fractures without any symptoms of carpal tunnel syndrome. We extracted mRNA from the flexor tenosynovium and compared the expression levels of genes encoding 17 types of Wnt in both subjects and controls via quantitative real-time polymerase chain reaction (PCR). Expression levels of factors involved in cell proliferation, such as estrogen-responsive finger protein, epidermal growth factor receptor, heparin binding-epidermal growth factor-like growth factor, insulin-like growth factor-1, and vascular endothelial growth factor (VEGF) were also measured using quantitative real-time PCR. In addition, we compared the Wnt and MIB-1 protein expression levels to clarify the effect of Wnt on cell proliferation. Quantitative real-time PCR revealed significantly greater expression of the gene encoding Wnt9a in subjects with ICTS than in controls and also revealed a positive correlation between the expression of genes encoding Wnt9a and VEGF in subjects with ICTS. Quantitative evaluation using immunohistochemical staining also indicated more marked Wnt9a expression in subjects than in controls. However, there was no relationship between the expression of Wnt9a and the cell proliferation index MIB-1. These results indicate that Wnt9a expression is enhanced in ICTS and that Wnt9a may be involved in VEGF expression in ICTS.

MR Imaging of the Nerves of the Upper Extremity: Elbow to Wrist

The peripheral nervous system is susceptible to a diverse array of pathologic insults, broadly categorizable into those entities intrinsic to the nerves themselves, either primarily arising within the nerve(s) or direct involvement of the nerve(s) secondary to a systemic process, and those processes external to the nerve(s) proper but affecting them extrinsically via mass effect, such as entrapment neuropathies. The soft tissue contrast inherent to high-quality MR imaging allows for outstanding visualization of the peripheral nervous system and surrounding structures. This review focuses on the use of MR imaging in the diagnosis and management of peripheral nerve disorders of the upper extremity.

Comparison of the histopathological findings of patients with diabetic and idiopathic carpal tunnel syndrome

PURPOSE

This study is aimed to investigate whether there are any histopathological differences between diabetic and idiopathic carpal tunnel syndromes.

METHODS

The biopsy specimens were taken from transverse carpal ligament (TCL), tenosynovium adjacent to median nerve and epineurium of median nerve and evaluated in 47 patients (21 diabetic and 26 idiopathic) who were diagnosed with carpal tunnel syndrome (CTS) and treated surgically with open carpal tunnel release. Fibroblast proliferation, fibrosis, perivascular inflammation, oedema, vascular proliferation and vascular wall thickness were determined and scored in all specimens.

RESULTS

There weren't any histopathological abnormalities in TCL specimens of both groups. Synovial hyperplasia, fibrosis and perivascular inflammation were not observed in tenosynovial analysis of both groups. Diabetic CTS patients, when compared with idiopathic CTS patients, had higher rates of synovial edema (idiopathic CTS 57 %, diabetic CTS 87 %), vascular proliferation (idiopathic CTS 30.8 %, diabetic CTS 90.5 %) and increased vascular wall thickness (idiopathic CTS 11.5 %, diabetic CTS 90.5 %). There was no oedema, fibrosis and perivascular inflammation of the epineurium in specimens of either group. But increases in vascular proliferation (idiopathic CTS 7.7 %, diabetic CTS 71.4 %) and vascular wall thickness (idiopathic CTS 3.8 %, diabetic CTS 71.4 %) was seen in the epineurium of diabetic patients and these differences were statistically significant (p < 0.05).

CONCLUSION

Because of the severe synovial and epineurial histopathological abnormalities and inadequate neural regeneration capacity, surgical open carpal tunnel decompression should be planned earlier in diabetic CTS patients. Further studies should be considered to evaluate the histopathological features of diabetic CTS patients early in the course of the disease.

Carpal tunnel syndrome pathophysiology: role of subsynovial connective tissue

Carpal tunnel syndrome (CTS) is a very common pathology. Its most common diagnosis is idiopathic. Although it is accepted that chronic increase in pressure within the carpal tunnel is responsible for median nerve neuropathy, the exact pathophysiology leading to this pressure increase remains unknown. All the histological studies of the carpal tunnel in the CTS find a noninflammatory thickening of the subsynovial connective tissue (SSCT), which seems to be a characteristic of this pathology. Numerous animal models have been developed to recreate CTS in vivo to develop and improve preventive strategies and effective conservative treatments by a better understanding of its pathophysiology. The creation of a shear injury of the SSCT in a rabbit model induced similar modifications to what is observed in CTS, suggesting that this could be a pathway leading to idiopathic CTS.

The role of ultrasound in the diagnosis and management of carpal tunnel syndrome: a new paradigm

Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy, affecting 9% of women, and it is responsible for significant morbidity and occupational absence. Clinical assessment is used for initial diagnosis and nerve conduction (NC) studies are currently the principal test used to confirm the diagnosis. Sensitivity of NC studies is >85% and specificity is >95%. There is now good evidence that US can be used as an alternative to NC studies to diagnose CTS. US can assess the anatomy of the median nerve and also identify pathology of the surrounding structures that may compress the nerve. Median nerve enlargement (cross-sectional area ≥10 mm(2) at the level of the pisiform bone or tunnel inlet) is the most commonly used parameter to diagnose CTS on US, and sensitivity has been reported to be as high as 97.9% using this parameter. US may also be used to guide therapeutic corticosteroid injection into the carpal tunnel--thus avoiding median nerve injury--and to objectively monitor the response to treatment. There is now sufficient evidence to propose a new paradigm for the diagnosis of CTS that incorporates US. US is proposed as the initial diagnostic test in CTS based on similar sensitivity and specificity to NC studies but higher patient acceptability, lower cost and additional capability to assess carpal tunnel anatomy and guide injection.

A handy review of carpal tunnel syndrome: From anatomy to diagnosis and treatment

Carpal tunnel syndrome (CTS) is the most commonly diagnosed disabling condition of the upper extremities. It is the most commonly known and prevalent type of peripheral entrapment neuropathy that accounts for about 90% of all entrapment neuropathies. This review aims to provide an outline of CTS by considering anatomy, pathophysiology, clinical manifestation, diagnostic modalities and management of this common condition, with an emphasis on the diagnostic imaging evaluation.

Intracarpal tunnel contents: evaluation of the effects of corticosteroid injection with sonoelastography

PURPOSE

To define the stiffness of the intracarpal tunnel contents and to evaluate the effect of corticosteroid injection on the intracarpal tunnel contents by using sonoelastography.

MATERIALS AND METHODS

This study was conducted with the approval of the institutional review boards, and all participants provided written, informed consent. Both hands were studied in 20 healthy volunteers, including eight men (mean age, 59.6 years; range, 50-76 years) and 12 women (mean age, 61.0 years; range, 39-79 years) and 22 hands were studied in 20 patients with carpal tunnel syndrome (CTS) (five men [mean age, 49.0 years] and 15 women [mean age, 61.1 years]; range, 39-89 years) between April 2012 and August 2012. The stiffness of the intracarpal tunnel contents was estimated as the standardized acoustic coupler (AC)-to-intracarpal tunnel contents surrounding the nerve (AC/C) strain ratio, analyzed with the Mann-Whitney U test. The patients were treated with corticosteroid injections, and the strain ratio was reexamined 6 weeks later, analyzed with the Wilcoxon t test.

RESULTS

The mean AC/C strain ratio in the CTS patients was 12.6 ± 4.7 (standard deviation), which was higher (stiffer) than that in the healthy volunteers with a mean strain ratio of 8.2 ± 3.5 (P = .0013). Six weeks after the injection, the mean AC/C strain ratio had decreased to 8.5 ± 4.1 (P = .00069, compared with the preinjection value) in the CTS patients.

CONCLUSION

The stiffness of the intracarpal tunnel contents in untreated CTS patients is higher than that of healthy volunteers but decreases 6 weeks after corticosteroid injection.

Repetitive differential finger motion increases shear strain between the flexor tendon and subsynovial connective tissue

Non-inflammatory fibrosis and thickening of the subsynovial connective tissue (SSCT) are characteristic in carpal tunnel syndrome (CTS) patients. These pathological changes have been linked to repetitive hand tasks that create shear forces between the flexor tendons and SSCT. We measured the relative motion of the flexor digitorum superficialis tendon and SSCT during two repetitive finger tasks using color Doppler ultrasound. Twelve participants performed flexion-extension cycles for 30 min with the long finger alone (differential movement) and with all four fingers together (concurrent movement). Shear strain index (SSI, a relative measure of excursion in flexion and extension) and maximum velocity ratio (MVR, the ratio of SSCT versus tendon during flexion and extension) were used to represent shear. A linear effect of exertion time was significant and corresponded with larger tendon shear in differential motion. The flexion SSI increased 20.4% from the first to the 30th minute, while MVR decreased 8.9% in flexion and 8.7% in extension. No significant changes were found during concurrent motion. These results suggest that exposure to repetitive differential finger tasks may increase the risk of shear injury in the carpal tunnel.

Sonographic measurements of subsynovial connective tissue thickness in patients with carpal tunnel syndrome

OBJECTIVES

A major pathologic finding in patients with idiopathic carpal tunnel syndrome is noninflammatory fibrosis and thickening of the subsynovial connective tissue. The objective of this study was to determine the ability of sonography to depict this thickening by comparing subsynovial connective tissue thickness in patients with carpal tunnel syndrome and healthy control participants.

METHODS

Longitudinal sonograms of the middle finger superficial flexor tendon and subsynovial connective tissue were obtained at 3 levels: at the wrist crease (proximal tunnel), at the hook of the hamate (mid tunnel), and at the distal edge of the transverse carpal ligament (distal tunnel). The thickness of the subsynovial connective tissue perpendicular to the direction of the tendon and the diameter of the flexor digitorum superficialis tendon at the same level were measured. Then, a thickness ratio was created.

RESULTS

At all 3 levels, the subsynovial connective tissue was thicker in patients than in controls (P < .0001) with a thickness ranging from 0.60 to 0.63 mm in patients and 0.46 to 0.50 mm in controls. The thickness ratio was significantly greater in patients at the hamate and distal levels (P = .018 and .013, respectively).

CONCLUSIONS

With this study, we have shown that it is possible to measure subsynovial connective tissue thickness with sonography, and the tissue is thicker in patients with carpal tunnel syndrome than in healthy controls.

Histopathological, clinical, and electrophysiological features influencing postoperative outcomes in carpal tunnel syndrome

Data on the outcome predictors of surgical result of carpal tunnel syndrome (CTS) is sparse and often conflicting. The purpose of this prospective comparative study was to evaluate the neurophysiologic findings and histological characteristics of the flexor tenosynovium in patients with CTS, assessing possible associations between these findings and preoperative patient status or surgical outcome. We evaluated 30 consecutive patients with a diagnosis of idiopathic CTS who were referred for surgery. Demographic data, subjective and objective data, and responses on an expanded assessment set, were collected before and 6 months after surgery. All patients underwent diagnostic neurophysiological testing prior to surgery, and histological analysis of tenosynovium specimens that were removed during surgery. Ten fresh-frozen cadavers served as controls. There was significant improvement in most of the disease specific (Boston questionnaire and Hi-Ob scale) and health generic (SF-36 questionnaire) evaluation tools used in the study at the 6-month follow-up. Vascular changes were noted in the tenosynovium of the flexor tendon of patients with CTS when compared with controls. Greater synovial vascularization was negative predictor of the SF-36's physical summary score before surgery. Bilateral presentation of symptoms and low nerve conduction velocity were negative predictors of the quality of life of patients after surgery for CTS. These findings have to be considered when discussing with patients as for the expected and desired outcomes of CTS surgery. The increased vascularization of flexor tenosynovium is associated with patients' functional status.

Combined Doppler and B-mode sonography in carpal tunnel syndrome

An intraoperatively enlarged engorged median nerve has been described as typical of patients with carpal tunnel syndrome (CTS). Although many studies of CTS have addressed median nerve enlargement, little is known about the usefulness of Doppler methods in detecting median nerve engorgement combined with nerve cross-sectional area (CSA). In a retrospective study of hands referred for evaluation of possible CTS, patients were clinically graded into Highly-likely or Indeterminate CTS. Nerve conduction studies (NCS), CSA, and Doppler analysis were compared. Median nerve blood flow was detected in 29 of 30 Highly-likely CTS hands (mean 13.3m/s (8.2) SD) and in 25 of 30 with Indeterminate CTS (mean 8.5m/s (4.5) SD). These were significantly higher than our laboratory normal values (mean 1.9 m/s (2.8) SD). Raised intraneural blood flow showed the highest test sensitivity in diagnosing Highly-likely carpal tunnel syndrome (83%) and combined with CSA reached 90%. NCS sensitivity was 83%. In the group of Indeterminate CTS, combined blood flow and CSA showed abnormality in 77% and NCS 47%. All nerve conduction parameters and median nerve cross sectional area showed linear correlation to intraneural blood flow velocity (P<0.05; Spearman's r=0.362 to 0.264). This study suggests that adding measures of intraneural blood flow to CSA further improves the sonographic evaluation of CTS and may be of particular use in patients with negative NCS.

Velocity-dependent changes in the relative motion of the subsynovial connective tissue in the human carpal tunnel

The purpose of this study was to measure the rate-dependent changes in the relative motion of subsynovial connective tissue (SSCT) and median nerve in the human carpal tunnel. Using fluoroscopy, we measured the relative motion of middle finger flexor digitorum superficialis tendon, SSCT, and median nerve in eight human cadavers during simulated active finger flexion motions at 2.0, 5.0, 7.5, and 10.0 mm/s. The shear index was defined as the difference in motion between tendon and SSCT or tendon and nerve, expressed as a percentage of tendon excursion. The motion patterns of the SSCT and median nerve relative to tendon excursion were measured at each 10% increment (decile) of maximum tendon excursion. The tendon-SSCT shear index was significantly higher at 10.0 mm/s than at 2.0 mm/s in the single-digit motion. There were corresponding significant decreases in SSCT and median nerve motion for the 10.0 mm/s velocity compared to the 2.0 mm/s velocity. This study demonstrates that the relative motion of the tissues in the carpal tunnel appears to be dependent on tendon velocity, specifically with less nerve and SSCT motion at higher velocity tendon motion. This suggests that SSCT may be predisposed to shear injury from high-velocity tendon motion.

Oxidative stress in subsynovial connective tissue of idiopathic carpal tunnel syndrome

Ischemic-reperfusion injury is thought to be a cause of idiopathic carpal tunnel syndrome (CTS). The purpose of this study was to determine whether oxidative stress caused by ischemia-reperfusion injury in subsynovial connective tissue is associated with idiopathic CTS and its symptoms. Bioptic samples of tenosynovial tissue were collected from 20 idiopathic CTS patients during surgery. Control specimens of tenosynovial tissue were collected from eight non-CTS patients. Analysis included histological and immunohistochemical examination for the distribution of endothelial nitric oxide synthase (eNOS), nuclear factor (NF)-κβ, and transforming growth factor (TGF)-β RI in subsynovial connective tissues. Histological examinations showed a marked increase in fibroblast density and vascular proliferation in specimens from CTS patients. The expressions of eNOS, NF-κβ, and TGF-β RI in fibroblasts and vascular endothelial cells of subsynovial connective tissues of patients were significantly higher than in those of controls. A significant positive correlation was found between the subjective symptom severity of CTS, and the immunoreactivities of eNOS and NF-κβ. This study suggests that oxidative stress in subsynovial connective tissue is related to CTS and its symptoms.

The expression of estrogen receptors in the tenosynovium of postmenopausal women with idiopathic carpal tunnel syndrome

The purpose of this study was to investigate estrogen receptor (ER) expression in tenosynovial tissues of postmenopausal woman with idiopathic carpal tunnel syndrome (CTS) to determine whether estrogen contributes to the pathogenesis of this condition. Biopsy samples of tenosynovial tissues were collected from 14 postmenopausal women (mean age; 57, range; 46-69 years) undergoing surgery for idiopathic CTS, and control specimens of tenosynovial tissue were collected from 6 postmenopausal women (mean age; 59, range; 48-68 years) without CTS. Histological and immunohistochemical examinations were performed to determine the distributions of ER-α and ER-β in tenosynovial tissues. Histological examinations showed a significant increase in fibroblast cell densities in the specimens from the carpal tunnel syndrome patients. ER-α and ER-β immunoreactivities were observed in fibroblasts and in the synovial lining cells of tenosynovial tissues, and these were significantly greater in patients than in controls. This study suggests that the up-regulations of ERs in the tenosynovial tissue are associated with idiopathic CTS in postmenopausal women.

Comparative study of carpal tunnel compliance in the human, dog, rabbit, and rat

The purpose of this study was to measure the compliance of the carpal tunnel in candidate animal models of carpal tunnel syndrome (CTS), by measuring the resistance when passing a tapered metal rod through the carpal tunnel. Forepaws from 10 dogs, 10 rabbits, and 10 rats with intact carpal tunnels, and 10 fresh frozen human wrist cadavers were used. The slopes of the linear part of the force-displacement curve (a measure of stiffness), normal force, and increasing area ratio (InAR) were significantly different among the four species (p<0.05). Post hoc analysis indicated that the mean slopes for the human carpal tunnel were the largest, indicating the least compliance, whereas those of the rat were the least (p<0.05). The features of the compliance for the dog carpal tunnel were closest to the human. The development of animal models of CTS should consider the compliance of the carpal tunnel, as it will be more difficult to increase pressure in a more compliant tunnel.

Embolization of a common carotid aneurysm with rhVEGF coupled to a pH-responsive chitosan in a rat model

Object

Treatment of cerebral aneurysms by endovascular deployment of liquid embolic agents has been proposed as an alternative strategy to conventional coiling, and new materials are being developed for embolization. In this study, the authors used a single-injection, biocompatible, biodegradable and pH-responsive acrylated chitosan (aCHN) with conjugated vascular endothelial growth factor (rhVEGF) in a rat aneurysm model.

Methods

The efficacy of the aCHN formulation with rhVEGF was tested using a common carotid artery occlusion model in rats, and the extent of embolization was evaluated using quantitative, qualitative, and histopathological techniques after 14 days of implantation.

Results

The mean occlusion was significantly greater for the rhVEGF/aCHN-treated group (96.8 ± 3.0%) than for the group receiving aCHN (74.7 ± 5.6%) (p < 0.01). Through qualitative evaluation, intimal and medial proliferation were significantly greater with rhVEGF/aCHN than with aCHN and controls (p < 0.001). Degradation of the aCHN filler was monitored in concert with the production of extracellular matrix components. Macrophages migrated in and proliferated inside the occluded carotid artery lumens were identified by histological and immunostainings. Results showed resorption of chitosan with concurrent development of collagen and elastin into the vessel lumen, suggesting clot maturation into fibrosis.

Conclusions

Chitosan with a bioactive agent such as rhVEGF showed excellent results in occluding aneurysms in a rat model.

Histopathology in horses with chronic palmar foot pain and age-matched controls. Part 2: The deep digital flexor tendon

REASONS FOR PERFORMING STUDY

Causes of palmar foot pain and the aetiopathogenesis of navicular disease remain poorly understood, despite the high incidence of foot-related lameness.

HYPOTHESES

Abnormalities of the deep digital flexor tendon (DDFT) may contribute to palmar foot pain; ageing degenerative changes may be seen in horses free from lameness; and horses with lameness are likely to have a greater severity of abnormalities than age-matched horses with no history of foot pain.

METHODS

Feet were selected from horses with a history of uni- or bilateral forelimb lameness of at least 2 months' duration. Histology of the DDFT from the level of the proximal interphalangeal joint to its insertion were examined and the severity of lesions for each site graded. Associations between lesions of the navicular bone, collateral sesamoidean ligaments (CSL), distal sesamoidean impar ligament, navicular bursa, distal interphalangeal (DIP) joint synovium and collateral ligaments of the DIP joint and DDFT were assessed.

RESULTS

There was no relationship between age and grade of histological abnormality of the DDFT. There were significant histological differences between groups for lesions of the dorsal layers of the DDFT, but not for lesions of the palmar aspect. There were significant associations between histological grades for the superficial dorsal layer of the DDFT and flexor aspect of the navicular bone; and between the deep dorsal layer of the DDFT and the proximal border and medulla of the navicular bone. The navicular bursa grade was correlated with grades for the superficial dorsal, deep dorsal and deep palmar layers of the DDFT. The histological grades for the CSL and the superficial dorsal layer of the DDFT were also associated.

CONCLUSIONS

Pathological abnormalities in lame horses often involved the DDFT in addition to the navicular bone. Vascular and matrix changes may precede changes in the fibrocartilage of the navicular bone.

POTENTIAL RELEVANCE

Identification of factors leading to vascular changes within the interstitium of the DDFT and changes in matrix composition, may help in future management of palmar foot pain.

Current concepts of carpal tunnel syndrome: pathophysiology, treatment, and evaluation

The current concepts of carpal tunnel syndrome (CTS) with respect to its pathophysiology, treatment, and evaluation are discussed. With regard to the pathophysiology of idiopathic CTS, biomechanical studies to determine the kinematics of the flexor tendon, and the median nerve inside the carpal tunnel may provide valuable insights. Different degrees of excursion between the flexor tendons and the median nerve could cause strain and microdamage to the synovial tissue; this has been microscopically observed. A biomechanical approach for elucidating the events that trigger the development of CTS seems interesting; however, there are limitations to its applications. Endoscopic carpal tunnel release (ECTR) is a useful technique for achieving median nerve decompression. However, it is not considered superior to conventional open carpal tunnel release in terms of fast recovery of hand function. Unless the effect of inserting a cannula into the diseased carpal tunnel on the median nerve function is quantitatively elucidated, ECTR will not be regarded as a standard procedure for relieving the median nerve from chronic compression. The treatment of CTS should be evaluated on the basis of patient-oriented questionnaires as well as conventional instruments because these questionnaires have been validated and found to be highly responsive to the treatment. It should be noted that nerve conduction studies exclusively evaluate the function of the median nerve, whereas patient-oriented questionnaires take into account not only the symptoms of CTS but other accompanying pathologies as well, such as flexor tenosynovitis. In Japan, the number of CTS patients is expected to rise; this may be attributed to a general increase in the life-span of the Japanese and increase in the number of diabetic patients. Thus, more efforts should be directed toward elucidating the pathophysiology of so-called idiopathic CTS, so that new treatment strategies can be established for CTS of different pathologies.

The effects of hypertonic dextrose injection on connective tissue and nerve conduction through the rabbit carpal tunnel

OBJECTIVE

To investigate the effects of hypertonic dextrose injection on the subsynovial connective tissue (SSCT) in a rabbit model. We hypothesized that dextrose injection would induce proliferation of the SSCT, hinder median nerve conduction, and alter SSCT mechanical properties, similar to what is observed in patients with carpal tunnel syndrome (CTS).

DESIGN

Randomized, controlled prospective study.

SETTING

Not applicable.

PARTICIPANTS

New Zealand white rabbits (N=28) weighing 4.0 to 4.5kg.

INTERVENTION

One forepaw was randomly injected with 0.1mL 10% dextrose solution. The contralateral paw was injected with a similar amount of 0.9% saline solution as a control. Animals were killed at 12 weeks after injection.

MAIN OUTCOME MEASURES

Animals were evaluated by electrophysiology (EP), mechanical testing, and histology. EP was evaluated by distal motor latency and amplitude. Shear force was evaluated when the middle digit flexor digitorum superficialis tendon was pulled out from the carpal tunnel. The ultimate tensile load and the energy absorption were also measured. Tissue for histology was evaluated qualitatively.

RESULTS

EP demonstrated significant prolongation of distal motor latency. The energy absorption and stiffness were also significantly increased in the dextrose group. Histologically, the dextrose group showed thickening of the collagen bundles and vascular proliferation within the SSCT compared with the saline group.

CONCLUSIONS

These results are consistent with the findings in patients with CTS and suggest that hypertonic dextrose injection has the potential to create a novel animal model in which to study the evolution of CTS.

Idiopathic carpal tunnel syndrome and trigger finger: is there an association?

Carpal tunnel syndrome (CTS) and trigger finger are known to occur together in association with conditions such as diabetes mellitus, rheumatoid arthritis and hypothyroidism. Although most cases that present to a hand clinic have no obvious predisposing cause, the two conditions often appear together in the same patient. We performed a prospective study of the prevalence of CTS in hospital outpatients presenting with trigger finger. Six hundred and eighty-one patients with CTS, trigger finger or both conditions were recruited prospectively. Diagnosis of both disorders was made on clinical grounds. The study group comprised 551 patients with no obvious predisposing cause. Of 211 patients with trigger finger, 91 (43%) also had CTS. This prevalence is substantially higher than the population prevalence of CTS of approximately 4%. Our data support an association between idiopathic CTS and idiopathic trigger finger and lend support to common pathophysiological factors.

Disparity between popular (Internet) and scientific illness concepts of carpal tunnel syndrome causation

PURPOSE

To determine whether there are notable disparities between popular (Internet) and scientific (Index Medicus) theories of carpal tunnel syndrome (CTS) causation.

METHODS

Reports from 3 sources were evaluated with regard to support for etiological theories of CTS: 1) patient-oriented information on CTS from the Internet, 2) recent physician-oriented information on CTS from medical journals indexed on Index Medicus, and 3) articles addressing the etiology of CTS from the 1997 National Institute for Occupational Safety and Health report. Multiple logistic regression analyses evaluated differences in etiological theories from the 3 sources.

RESULTS

Internet sites implicated vitamin B(6) deficiency, tenosynovitis, and typing or computer use as causes for idiopathic CTS considerably more often and genetic predisposition considerably less often than recent Index Medicus scientific reports and reports reviewed by the National Institute for Occupational Safety and Health.

CONCLUSIONS

There are notable disparities between popular (Internet) and scientific (Index Medicus) theories of CTS causation.

The quality and strength of evidence for etiology: example of carpal tunnel syndrome

PURPOSE

The purpose of this investigation was to evaluate the quality and strength of scientific evidence supporting an etiologic relationship between a disease and a proposed risk factor using a scoring system based on the Bradford Hill criteria for causal association.

METHODS

A quantitative score based on the Bradford Hill criteria (qBHs) was used to evaluate 117 articles presenting original data regarding the etiology of carpal tunnel syndrome: 33 (28%) that evaluated biological (structural or genetic) risk factors, 51 (44%) that evaluated occupational (environment or activity-related) risk factors, and 33 (28%) that evaluated both types of risk factors.

RESULTS

The quantitative Bradford Hill scores of 2 independent observers showed very good agreement, supporting the reliability of the instrument. The average qBHs was 12.2 points (moderate association) among biological risk factors compared with 5.2 points (poor association) for occupational risk factors. The highest average qBHs was observed for genetic factors (14.2), race (11.7), and anthropometric measures of the wrist (11.3 points) with all studies finding a moderate causal association. The highest average qBHs among occupational risk factors was observed for activities requiring repetitive hand use (6.5 points among the 30 of 45 articles that reported a causal association), substantial exposure to vibration (6.3 points; 14 of 20 articles), and type of occupation (5.6 points; 38 of 53 articles), with the findings being much less consistent.

CONCLUSIONS

According to a quantitative analysis of published scientific evidence, the etiology of carpal tunnel syndrome is largely structural, genetic, and biological, with environmental and occupational factors such as repetitive hand use playing a minor and more debatable role. Speculative causal theories should be analyzed through a rigorous approach prior to wide adoption.