High-resolution ultrasound analysis of subsynovial connective tissue in human cadaver carpal tunnel.

The carpal tunnel contains the median nerve, nine flexor tendons, two synovial bursae, and peritendinous subsynovial connective tissue (SSCT). Fibrosis of the SSCT is the most consistent pathological finding in patients with carpal tunnel syndrome. We investigated the anatomy and gliding characteristics of the flexor digitorum superficialis tendon and its adjacent SSCT with high-resolution ultrasound (15 MHz). Our hypotheses were that tendon and SSCT are distinguishable by ultrasound and that their velocities during tendon excursion are different. Qualitative ultrasound analysis of a flexor tendon and its SSCT was performed on five cadaver wrists and correlated to respective findings after anatomical study of the same cadavers. Quantitative Doppler velocity analysis of eight cadaver wrists was done to assess the sliding movement of the tendon and its SSCT within the carpal tunnel. No significant difference was found between the thickness of SSCT measured by ultrasound and that measured directly after dissection. The SSCT moved slower than its flexor tendon. The SSCT velocities were statistically different from the tendon velocities (t-test, p>0.001). High-resolution ultrasound is a very precise method to display the anatomy of the tendon and SSCT within the carpal tunnel, and their different velocities can be detected with Doppler. Noninvasive assessment of the thickness and velocity of the tenosynovium in carpal tunnel syndrome by high-resolution sonography might be a new diagnostic tool for disorders affecting the SSCT, especially carpal tunnel syndrome.     

The response of the rabbit subsynovial connective tissue to a stress-relaxation test

The subsynovial connective tissue (SSCT) in the carpal tunnel may play a role in the etiology of carpal tunnel syndrome (CTS), yet the material properties of the SSCT remain unclear. Thus, we investigated the mechanical response of the SSCT in a rabbit model. Twenty‐four rabbit cadaver paws were used for mechanical testing; two paws were used for scanning electron microscopy (SEM) imaging. After testing normal tendon excursion, the divided third digit flexor digitorum superficialis (FDS) tendon was pulled to displacements of 2, 3.5, 5, or 8 mm, maintained at that position until force decay, and then the process was repeated. Normal excursion of the FDS averaged 4.8 mm. The ratio of the second peak force to the first peak force in the 2 mm group was 0.98 (SD = 0.16), which was significantly higher than the other groups (3.5 mm: 0.74, 5 mm, 0.63, and 8 mm: 0.59; p < 0.05). SEM showed ruptured fibrils in the displaced specimen. The declining force ratio with displacements >2 mm suggests damage to the SSCT within the physiological tendon excursion. These data may be useful in understanding SSCT mechanics in CTS, which is associated with SSCT fibrosis. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 30:443–447, 2012     

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. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:62–66, 2011     

The effect of displacement on the mechanical properties of human cadaver subsynovial connective tissue

The subsynovial connective tissue (SSCT) in the carpal tunnel may participate in the origin of carpal tunnel syndrome (CTS), yet material properties of the SSCT have not been well‐characterized. We investigated the response of the SSCT to repeated ramp stretch tests. Eight human cadaver wrists were used. The physiological excursion of the flexor digitorum superficialis of the third digit (FDS 3) was measured, starting from a neutral position to maximal flexion of the metacarpophalangeal and proximal interphalangeal joints. The FDS 3 tendon was pulled to 40%, 60%, 90%, and 120% of the physiological excursion. Two “ramp stretch” cycles were performed at every excursion level, except for 120% of excursion, where three cycles were performed. The ratio of energy absorbed between the second (E2) and first (E1) ramp stretch was 0.94 (SD = 0.07) for 60%, 0.84 (SD = 0.11) for 90%, and 0.68 (SD = 0.11) for 120% of the physiological excursion. A significant decrease occurred in energy absorbed after the first ramp stretch cycle at 90% and 120% of the physiological excursion, which was not seen at 60%. Our data are consistent with a stepwise damage occurring in the SSCT. Furthermore, the damage seems to initiate within the physiological range of tendon excursion. This finding may be important in understanding the pathophysiology of conditions that are associated with SSCT pathology, such as carpal tunnel syndrome. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:1732–1737, 2012     

Multidimensional ultrasound imaging of the wrist: Changes of shape and displacement of the median nerve and tendons in carpal tunnel syndrome

Dynamics of structures within the carpal tunnel may alter in carpal tunnel syndrome (CTS) due to fibrotic changes and increased carpal tunnel pressure. Ultrasound can visualize these potential changes, making ultrasound potentially an accurate diagnostic tool. To study this, we imaged the carpal tunnel of 113 patients and 42 controls. CTS severity was classified according to validated clinical and nerve conduction study (NCS) classifications. Transversal and longitudinal displacement and shape (changes) were calculated for the median nerve, tendons and surrounding tissue. To predict diagnostic value binary logistic regression modeling was applied. Reduced longitudinal nerve displacement (p≤ 0.019), increased nerve cross‐sectional area (p≤ 0.006) and perimeter (p≤ 0.007), and a trend of relatively changed tendon displacements were seen in patients. Changes were more convincing when CTS was classified as more severe. Binary logistic modeling to diagnose CTS using ultrasound showed a sensitivity of 70–71% and specificity of 80–84%. In conclusion, CTS patients have altered dynamics of structures within the carpal tunnel. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1332–1340, 2015.     

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. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31:1533–1539, 2013.

     

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     

Median nerve deformation and displacement in the carpal tunnel during finger motion

The objective of this study was to evaluate the correlations between deformation and displacement of median nerve and flexor tendons during finger motion in the carpal tunnel for both carpal tunnel syndrome (CTS) patients and healthy controls. Sixty‐two wrists of 31 asymptomatic volunteers and fifty‐one wrists of 28 idiopathic CTS patients were evaluated by ultrasound. The displacement of the median nerve and the middle finger flexor digitorum superficialis (FDS) tendon, as well as area, perimeter, aspect ratio of a minimum enclosing rectangle, and circularity of the median nerve were measured in finger extension and flexion positions. Deformation indices were defined as the ratios of indices in finger extension and flexion positions. The correlations between displacement and deformation indices were evaluated. There were significant correlations between nerve palmar–dorsal displacement and deformation indices (p < 0.05). The aspect ratio deformation index showed the strongest correlation to palmar–dorsal displacement of the nerve (?0.572, p < 0.01). This study showed that there is a relationship between median nerve deformation indices and nerve palmar–dorsal displacement in the carpal tunnel. Since the highest correlations were between palmar–dorsal nerve displacement direction and aspect ratio deformation index, these parameters may be helpful to understand the pathophysiology of CTS. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31:1876–1880, 2013

     

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

We used the Verhoeff-van Gieson stain method to identify histopathology and to localize elastin in the subsynovial connective tissue of the tendon sheath (SSCT) of the middle finger flexor digitorum superficialis (FDS) within the carpal tunnel in 10 carpal tunnel syndrome (CTS) patients and 10 control cadaver specimens. Normal SSCT stained for elastin abundantly around blood vessels and within vessel walls. The typical pathologic findings of CTS patients SSCT included vascular proliferation, vascular hypertrophy, and vascular obstruction with wall thickening. There was a decreased amount of elastin in the blood vessel walls and around the vessels in the CTS patients as well. The changes in the carpal tunnel patients were particularly remarkable in that the patients were younger than the controls, yet showed findings more characteristic of chronic degeneration.     

Changes in digital flexor tendon mechanics after endoscopic and open carpal tunnel releases in cadaver wrists

Digital flexor tendon excursion due to isolated wrist motion was measured in 5 cadaver wrists. Five sequential experimental conditions were tested: (1) intact wrists, (2) after single-incision endoscopic carpal tunnel release, (3) after addition of a distal endoscopic portal, (4) after conversion to an open palm incision, and (5) after suturing of the palm incision. Combined tendon excursion increased 27.8% after 1-incision and 29.7% after 2-incision endoscopic release; both increases were significant. A further increase in combined excursion to 43.4% over the value in intact wrists was measured after conversion to an open palm incision. Combined flexor tendon excursion after open release was significantly greater than excursion after either type of endoscopic release. Increases in excursion were also significant when flexor digitorum superficialis and flexor digitorum profundus tendons were considered separately. Excursion did not change significantly after skin suturing. These findings suggest that digital flexor tendon mechanics are closer to normal after endoscopic carpal tunnel release than after open release. It remains to be shown whether the difference is an advantage of endoscopic release over open release in the clinical setting. (J Hand Surg 2000; 25A:112-119.     

Ultrasound assessment of the effectiveness of carpal tunnel release on median nerve deformation

To assess the biomechanical effect of carpal tunnel release (CTR), we evaluated the deformation and displacement patterns of the median nerve before and after CTR in carpal tunnel syndrome (CTS) patients. Sixteen wrists of 14 idiopathic CTS patients who had open CTR and 26 wrists of 13 asymptomatic volunteers were evaluated by ultrasound. Cross‐sectional images of the carpal tunnel during motion from full finger extension to flexion were recorded. The area, perimeter, aspect ratio of a minimum enclosing rectangle, and circularity of the median nerve were measured in finger extension and flexion positions. Deformation indices, determined by the flexion–extension ratio for each parameter, were compared before and after CTR. After CTR, the deformation indices of perimeter and circularity became significantly larger and the aspect ratio became significantly smaller than those before CTR (p < 0.05). Those differences were more obvious when comparing the values between the patients before CTR and the controls. Since the deformation indices after CTR are similar to the patterns of normal subjects, the surrounding structures and environment of the median nerve may be normalized upon CTR. This may be a way to tell how the median nerves recover after CTR. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:726–730, 2015.     

Subsynovial connective tissue is sensitive to surgical interventions in a rabbit model of carpal tunnel syndrome

The most common histological finding in carpal tunnel syndrome (CTS) is non-inflammatory fibrosis and thickening of the subsynovial connective tissue (SSCT) in the tunnel. While the cause of SSCT fibrosis and the relationship of SSCT fibrosis and CTS are unknown, one hypothesis is that SSCT injury causes fibrosis, and that the fibrosis then leads to CTS. We investigated the sensitivity of the SSCT to injuries. Two types of surgical interventions were performed in a rabbit model: A skin incision with tendon laceration and SSCT stretching sufficient to damage the SSCT, and skin incision alone. Twelve weeks after surgery, the rabbit carpal tunnel tissues were studied with immunochemistry for TGF-β receptors 1, 2, and 3, collagen III, and collagen VI. All TGF-β receptors were expressed. The percentages of the TGF-β receptors' expressions were less in the control SSCT fibroblasts than in the fibroblasts from rabbits with surgical interventions. The surgical interventions did not result in any alteration of collagen III expression. However, both surgical interventions resulted in a significant decrease in collagen VI expression compared to the control group. The two surgical interventions achieved similar expression of TGF-β receptors and collagens. Our results provide evidence that the SSCT is sensitive to surgical interventions, even when these are modest. Since SSCT fibrosis is a hallmark of CTS, these data also suggest that such fibrosis could result from relatively minor trauma.     

TGF‐β signaling regulates fibrotic expression and activity in carpal tunnel syndrome

Fibrosis of the subsynovial connective tissue (SSCT) is a predominant feature of carpal tunnel syndrome (CTS). While the nature of CTS has been extensively studied, little is known about the etiology of this disease. We investigated SSCT tissue from patients with CTS and control subjects using fibrosis arrays and cell culture analysis. Twofold changes in fibrotic gene expression were found in multiple genes from patient SSCT using fibrosis arrays. This data was confirmed via qRT‐PCR on a subset of genes; collagen I (Col1), collagen III (Col3), connective tissue growth factor (CTGF), transforming growth factor β (TGF‐β), and SMAD3 (P < 0.05) which significantly corroborate the fold changes found in the fibrosis arrays. To further explore the nature of SSCT fibrosis, cells were isolated from patient and control tissue. Col1, Col3, TGF‐β, and SMAD3 were highly expressed in patient SSCT fibroblasts as compared to control (P < 0.05). Further, fibrotic genes expression was decreased by inhibiting TGF‐β receptor I (TβRI) activity (P < 0.05). TGF‐β second messenger SMAD activity was significantly activated in SSCT fibroblasts from patients and this activation was abrogated by inhibiting TβRI signaling (P < 0.05). These findings suggest that blocking TGF‐β signaling may be an important therapeutic approach to treating the underlying fibrosis of SSCT in CTS patients. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:1444–1450, 2014.     

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.     

Gliding characteristics between flexor tendons and surrounding tissues in the carpal tunnel: a biomechanical cadaver study.

The purpose of this study was to investigate the gliding characteristics of flexor tendons within the carpal tunnel with varied wrist positions and tendon motion styles, which may help us to understand the relationship between carpal tunnel syndrome (CTS) and repetitive hand motion. Eight fresh human cadaveric wrists and hands were used. The peak (PGR) and mean (MGR) gliding resistance of the middle finger flexor digitorum superficialis tendon were measured with the wrist in 0, 30, and 60 degrees of flexion and extension. While moving all three fingers together, the PGR at 60 degrees flexion was significantly higher than that at 0, 30, or 60 degrees extension. While moving the middle finger alone, the PGR at 60 and 30 degrees flexion was significantly higher than the PGR at 60 degrees extension. The PGR moving the middle finger FDS alone was significantly greater than that for all three digits moving together in 0, 30, and 60 degrees flexion. Differential finger motion with wrist flexion elevated the tendon gliding resistance in the carpal tunnel, which may be relevant in considering the possible role of wrist position and activity in the etiology of CTS.     

Tendon injury produces changes in SSCT and nerve physiology similar to carpal tunnel syndrome in an in vivo rabbit model

Background  

The etiology of carpal tunnel syndrome (CTS) remains idiopathic in many cases. Noninflammatory fibrosis of the subsynovial connective tissue (SSCT) within the carpal tunnel is common in CTS, and some clinicians have hypothesized that this fibrosis might be a cause rather than an effect of CTS. An animal model in which to test this hypothesis would be useful. The principal objective of this study was to investigate the effect of a surgical injury on SSCT fibrosis and median nerve function within the carpal tunnel in an in vivo rabbit model.     

Comparative Anatomy of the Subsynovial Connective Tissue in the Carpal Tunnel of the Rat, Rabbit, Dog, Baboon, and Human

The tenosynovium in the human carpal tunnel is connected to the flexor tendons and the median nerve by the subsynovial connective tissue (SSCT). The most common histological finding in carpal tunnel syndrome (CTS), a compression neuropathy of the median nerve, is noninflammatory fibrosis of the SSCT. The relationship, if any, between the fibrosis and nerve pathology is unknown, although some have speculated that a change in the SSCT volume or stiffness might be the source of the compression. Yet, while animal models have been used to study the physiology of nerve compression, so far none have been used to study the relationship of the SSCT pathology to the neurophysiological abnormalities. The purpose of this study was to identify animal models that might be appropriate to study the interaction of SSCT and nerve function in the development of CTS. The front paws of a rat, rabbit, dog, and baboon were dissected. The carpal tunnel anatomy and SSCT of these animals were also examined by light and scanning microscopy and compared to the relevant human anatomy and ultrastructure. The carpal tunnel anatomy and contents of the baboon and rabbit are similar to humans. The canine carpal tunnel lacks the superficial flexor tendons and the rat carpal tunnel is very small. The human, baboon, and rabbit specimens had very similar organization of the SSCT, and content of the carpal canal. We conclude that, while both the baboon and rabbit would be good animal models to study the relationship of the SSCT to CTS, the rabbit is likely to be more practical, in terms of cost and animal care concerns.     

Median nerve deformation and displacement in the carpal tunnel during index finger and thumb motion

The purpose of this study was to investigate the deformation and displacement of the normal median nerve in the carpal tunnel during index finger and thumb motion, using ultrasound. Thirty wrists from 15 asymptomatic volunteers were evaluated. Cross‐sectional images during motion from full extension to flexion of the index finger and thumb were recorded. On the initial and final frames, the median nerve, flexor pollicis longus (FPL), and index finger flexor digitorum superficialis (FDS) tendons were outlined. Coordinate data were recorded and median nerve cross‐sectional area, perimeter, aspect ratio of the minimal‐enclosing rectangle, and circularity in extension and flexion positions were calculated. During index finger flexion, the tendon moves volarly while the nerve moves radially. With thumb flexion, the tendon moves volarly, but the median nerve moves toward the ulnar side. In both motions, the area and perimeter of the median nerve in flexion were smaller than in extension. Thus, during index finger or thumb flexion, the median nerve in a healthy human subject shifts away from the index finger FDS and FPL tendons while being compressed between the tendons and the flexor retinaculum in the carpal tunnel. We are planning to compare these data with measurements in patients with carpal tunnel syndrome (CTS) and believe that these parameters may be useful tools for the assessment of CTS and carpal tunnel mechanics with ultrasound in the future. Published by Wiley Periodicals, Inc. J Orthop Res 28:1387–1390, 2010     

The effect of wrist position on the relative motion of tendon,nerve, and subsynovial connective tissue within the carpal tunnel in a human cadaver model

The purpose of this study was to measure the effect of wrist position on the relative motion of the middle finger flexor digitorum superficialis (FDS) tendon, subsynovial connective tissue (SSCT), median nerve, and flexor retinaculum during simulated active finger motion. The relative motion of each tissue was measured by fluoroscopy in 10 human cadavers. Measurements were obtained for wrist positions of neutral (0 degree extension), 30 and 60 degrees of flexion, and 30 and 60 degrees of extension. The shear strain index (SSI) was defined as the difference in motion between two tissues (tendon, SSCT, or nerve) divided by tendon excursion, expressed as a percentage. The motion of the tendon, SSCT, and nerve in the 60 degree flexed position was significantly less than the motion in all other wrist positions (p < 0.001). The SSI at 60 degrees of flexion for tendon–SSCT and tendon–nerve were significantly increased compared with all other positions (p < 0.001). Because the SSCT and tendon are physically connected, a decrease in SSCT motion relative to the tendon would increase the shear strain on the SSCT with tendon motion. Thus, this result suggests that the SSCT may be predisposed to shear injury from activity done in 60 degrees of wrist flexion. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:1153–1158, 2008     

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

The purpose of this study was to investigate the effect of carpal tunnel pressure on the gliding characteristics of flexor tendons within the carpal tunnel. Eight fresh human cadaver wrists and hands were used. A balloon was inserted into the carpal tunnel to elevate the pressure. The mean gliding resistance of the middle finger flexor digitorum superficialis tendon was measured with the following six conditions: (1) as a baseline, before balloon insertion; (2) balloon with 0 mmHg pressure; (3) 30 mmHg; (4) 60 mmHg; (5) 90 mmHg; (6) 120 mmHg. The gliding resistance of flexor tendon gradually increased as the carpal tunnel pressure was elevated. At pressures above 60 mmHg, the increase in gliding resistance became significant compared to the baseline condition. This study helps us to understand the relationship between carpal tunnel pressure, which is elevated in the patient with carpal tunnel syndrome (CTS) and tendon gliding resistance, which is a component of the work of flexion. These findings suggest that patients with CTS may have to expend more energy to accomplish specific motions, which may in turn affect symptoms of hand pain, weakness and fatigue, seen commonly in such patients. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:58–61, 2011