Effect of wrist position on power grip and key pinch strength following carpal tunnel decompression

Power grip and thumb key pinch strength were measured pre- and immediately postoperatively in 30 patients with carpal tunnel syndrome while the wrist was in flexion and extension. The carpal tunnel decompression was performed under local infiltration with 1% lignocaine. Grip strength decreased more in wrist flexion than in wrist extension. No difference was found in thumb pinch strength. The authors conclude that some of the immediate postoperative loss of grip strength in wrist flexion can be attributed to prolapse of flexor tendons out of the carpal tunnel in this position.     

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.     

Effects of static fingertip loading on carpal tunnel pressure

The purpose of this study was to explore the relationship between carpal tunnel pressure and fingertip force during a simple pressing task. Carpal tunnel pressure was measured in 15 healthy volunteers by means of a saline-filled catheter inserted percutaneously into the carpal tunnel of the nondominant hand. The subjects pressed on a load cell with the tip of the index finger and with 0, 6, 9, and 12 N of force. The task was repeated in 10 wrist postures: neutral; 10 and 20° of ulnar deviation; 10° of radial deviation; and 15, 30, and 45° of both flexion and extension. Fingertip loading significantly increased carpal tunnel pressure for all wrist angles (p = 0.0001). Post hoc analyses identified significant increases (p <0.05) in carpal tunnel pressure between unloaded (0 N) and all loaded conditions, as well as between the 6 and 12 N load conditions. This study demonstrates that the process whereby fingertip loading elevates carpal tunnel pressure is independent of wrist posture and that relatively small fingertip loads have a large effect on carpal tunnel pressure. It also reveals the response characteristics of carpal tunnel pressure to fingertip loading, which is one step in understanding the relationship between sustained grip and pinch activities and the aggravation or development of median neuropathy at the wrist.     

Median nerve deformation in differential finger motions: ultrasonographic comparison of carpal tunnel syndrome patients and healthy controls

We investigated the median nerve deformation in the carpal tunnel in patients with carpal tunnel syndrome and controls during thumb, index finger, middle finger, and a four finger motion, using ultrasound. Both wrists of 29 asymptomatic volunteers and 29 patients with idiopathic carpal tunnel syndrome were evaluated by ultrasound. Cross‐sectional images during motion from full extension to flexion were recorded. Median nerve cross‐sectional area, perimeter, aspect ratio of the minimal enclosing rectangle, and circularity in extension and flexion positions were calculated. Additionally, a deformation index was calculated. We also calculated the intra‐rater reliability. In both controls and patients, the median nerve cross‐sectional area became significantly smaller from extension to flexion in all finger motions (p < 0.05). In flexion and extension, regardless of the specific finger motion, the median nerve deformation, circularity and the change in perimeter were all significantly greater in CTS patients than in controls (p < 0.05). We found excellent intra‐rater reliability for all measurements (ICC > 0.84). With this study we have shown that it is possible to assess the deformation of the median nerve in carpal tunnel syndrome with ultrasonography and that there is more deformation of the median nerve in carpal tunnel syndrome patients during active finger motion. These parameters might be useful in the evaluation of kinematics within the carpal tunnel, and in furthering our understanding of the biomechanics of carpal tunnel syndrome in the future. © 2011 Orthopaedic Research Society. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 30:643–648, 2012     

In vivo flexor tendon forces increase with finger and wrist flexion during active finger flexion and extension.

The effects of different hand motions and positions used during early protected motion rehabilitation on tendon forces are not well understood. The goal of this study was to determine in vivo forces in human flexor digitorum profundus (FDP) and flexor digitorum superficialis (FDS) tendons of the index finger during active unresisted finger flexion and extension. During open carpal tunnel surgery (n = 12), flexor tendon forces were acquired with buckle force transducers, and finger positions were recorded on video while subjects actively flexed and extended the fingers at two different wrist angles. Mean in vivo FDP tendon forces varied between 1.3N +/- 0.9 N and 4.0 N +/- 2.9 N while mean FDS tendon forces ranged from 1.3N +/- 0.5 N to 8.5 N +/- 10.7 N. FDP force increased with active finger flexion at both wrist angles of 0 degrees or 30 degrees flexion. FDS force increased with finger flexion when the wrist was in 30 degrees flexion, but was unchanged when the wrist was in 0 degrees of flexion. Tendon forces were similar regardless of whether the fingers were moving in the flexion or extension direction. Active finger flexion and extension with the wrist at 0 degrees and 30 degrees flexion may be used during early rehabilitation protocols with limited risk of repair rupture. This risk can be further decreased for a FDS tendon repair by reducing wrist flexion angle.     

Entire flexor carpi radialis tendon harvest for thumb carpometacarpal arthroplasty alters wrist kinetics

PURPOSE: To investigate the clinical outcome of thumb carpometacarpal arthroplasty with entire-thickness flexor carpi radialis (FCR) ligament reconstruction and tendon interposition and to investigate the isokinetic wrist flexion/extension torque and flexion fatigue strength of the surgically treated wrist compared with the nonsurgically treated wrist. METHODS: Thirty-nine patients with osteoarthritis who had unilateral thumb carpometacarpal arthroplasty with the entire FCR tendon were studied prospectively with a minimum follow-up period of 24 months. Preoperative Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire score, grip, pinch, and postoperative DASH score, grip, pinch, and Biodex (Shirley, NY) isokinetic wrist flexion/extension torques were recorded. The nonsurgically treated extremity served as the control for each patient with unilateral ligament reconstruction and tendon interposition. Peak torque ratios and fatigue were measured for the control and surgically treated extremities with the Biodex. RESULTS: Postoperative DASH scores were 12 +/- 4 and were improved significantly from preoperative scores of 43 +/- 4. The surgically treated extremity showed a significantly lower wrist flexion-to-extension peak torque ratio than the control extremity. The control extremity had 2.5 times greater wrist flexion fatigue resistance than the surgically treated side. After surgery the surgically treated extremity had significantly improved grip strength and thumb-index tip pinch compared with the preoperative status. CONCLUSIONS: Our data show conclusively that wrist flexion extension torque ratio decreases and wrist flexion fatigue resistance decreases when the entire FCR tendon is harvested even though the final outcome is favorable and uniformly based on traditional DASH, grip, and pinch scores.     

Measurement of pressure in the carpal canal before and after endoscopic management of carpal tunnel syndrome

In forty-six patients who had carpal tunnel syndrome, a technique of continuous infusion, given under local anesthesia and without a pneumatic tourniquet, was used to measure pressures in the carpal canal before and after endoscopic release of the transverse carpal ligament (retinaculum flexorum manus). Pressures were similarly measured in sixteen subjects in a control group. The mean preoperative pressures were significantly higher in the patients who had carpal tunnel syndrome than in the patients in the control group when the pressures were measured under four conditions: with the wrist in the resting position, with active grip, and with maximum passive extension and flexion of the wrist. The mean pressures improved significantly postoperatively and were in the range of values that were found under each condition for the control group. Measurement of pressure in the carpal canal before and after operation may be useful in diagnosing carpal tunnel syndrome and in determining the effectiveness of endoscopic management.     

Fingertip loading and carpal tunnel pressure: Differences between a pinching and a pressing task

Carpal tunnel syndrome may be caused by repeated or sustained elevated carpal tunnel pressure. This study examined the relationship between carpal tunnel pressure, posture, and fingertip load. In 20 healthy individuals, carpal tunnel pressure was measured with a catheter inserted into the carpal tunnel of the dominant hand and connected to a pressure transducer. With the wrist in a pressure-neutral position, the subjects pressed on a force transducer with the index finger to levels of 0, 5, 10, and 15 N. They then pinched the transducer at the same levels of force. For both fingertip-loading postures, the carpal tunnel pressure increased with increasing fingertip load. Carpal tunnel pressures were significantly greater (p < 0.015) for the pinching task (14.2, 29.9, 41.9, and 49.7 mm Hg [1.89, 3.99, 5.59, and 6.63 kPa] for 0, 5, 10, and 15 N force levels, respectively) than for simple finger pressing (7.8, 14.1, 20.0, and 33.8 mm Hg [1.04, 1.88, 2.67, and 4.51 kPa]). This study indicates that although the external load on the finger remained constant between the two tasks, the internal loading, as measured by carpal tunnel pressure, experienced a near 2-fold increase by using a pinch grip. These findings should be given consideration in designing work tasks and tools because relatively low fingertip forces, especially in a pinch grip, elevate carpal tunnel pressures to levels that, if prolonged, may lead to the development or exacerbation of carpal tunnel syndrome.     

Predicting Carpal Bone Kinematics Using an Expanded Digital Database of Wrist Carpal Bone Anatomy and Kinematics

The wrist can be considered a 2 degrees‐of‐freedom joint with all movements reflecting the combination of flexion–extension and radial–ulnar deviation. Wrist motions are accomplished by the kinematic reduction of the 42 degrees‐of‐freedom of the individual carpal bones. While previous studies have demonstrated the minimal motion of the scaphoid and lunate as the wrist moves along the dart‐thrower's path or small relative motion between hamate‐capitate‐trapezoid, an understanding of the kinematics of the complete carpus across all wrist motions remains lacking. To address this, we assembled an open‐source database of in vivo carpal motions and developed mathematical models of the carpal kinematics as a function of wrist motion. Quadratic surfaces were trained for each of the 42‐carpal bone degrees‐of‐freedom and the goodness of fits were evaluated. Using the models, paths of wrist motion that generated minimal carpal rotations or translations were determined. Model predictions were best for flexion–extension, radial–ulnar deviation, and volar–dorsal translations for all carpal bones with R ² > 0.8, while the estimates were least effective for supination‐pronation with R ² < 0.6. The wrist path of motion's analysis indicated that the distal row of carpal bones moves rigidly together (<3° motion), along the anatomical axis of wrist motion, while the bones in the proximal row undergo minimal motion when the wrist moves in a path oblique to the main axes. The open‐source dataset along with its graphical user interface and mathematical models should facilitate clinical visualization and enable new studies of carpal kinematics and function. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2661–2670, 2019     

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.

     

Stress carpal tunnel pressures in patients with carpal tunnel syndrome and normal patients

Twenty-two patients with carpal tunnel syndrome scheduled to have a carpal tunnel release, and six volunteer control subjects had carpal tunnel pressures measured with their wrist in neutral position, maximum flexion, and maximum extension. The wrist was then repetitively flexed and extended to maximum position at a rate of 30 full cycles per minute for 1 minute. Pressures were then continually monitored and recorded at 30-second intervals. The pressures were found to be significantly elevated in the immediate post-exercise period in the patients with carpal tunnel syndrome, and they demonstrated a prolonged recovery time to reach the resting pressure when compared with the normal control subjects. This property of prolonged recovery time in patients with carpal tunnel syndrome suggests a possible cause for carpal tunnel syndrome in the occupational setting.     

Flexor tendon forces: in vivo measurements.

S-shaped force transducers were developed for measurement of the forces along intact tendons. After calibration, the transducers were applied to the flexor pollicis longus and flexor digitorum superficialis and profundus tendons of the index finger in five patients operated on for treatment of carpal tunnel syndrome. The tendon forces generated during passive and active motion of the wrist and fingers were recorded. For pinch function, the amount of the applied load was measured with a special pinch meter. Tendon forces in the range of 0.1 to 0.6 kgf were measured during passive mobilization of the wrist. Tendon forces up to 0.9 kgf were present during passive mobilization of the fingers. Tendon forces up to 3.5 kgf were present during active unresisted finger motion. Tendon forces up to 12.0 kgf were recorded during tip pinch, with a mean applied pinch force of 3.5 kgf. These results have potential application in determining the amount of force that a tendon repair would have to resist during passive as well as active postsurgical mobilizations.     

The excursion of the median nerve during nerve gliding exercise: an observation with high-resolution ultrasonography

The purpose of this study was to assess the relationship between the positioning of upper extremity and gliding distance of the median nerve during passive and active motion of the wrist and fingers. The longitudinal gliding of the medial nerve in the forearm was measured in 34 healthy subjects by ultrasonographic dynamic images. Those images were analyzed in a cross-correlation algorithm advocated by Dilley et al. (2001). In this experiment, passive extension of the wrist and fingers was applied manually by an examiner in four positions (elbow flexion and extension with forearm pronation, and elbow flexion and extension with forearm supination), two types of active finger motions (Hook and Grasp) were performed by the subjects. The distally oriented median nerve gliding ranged from 1.9 (in elbow extension with forearm pronation) to 3.0mm (in elbow flexion with forearm supination) during passive extension of the wrist and fingers. There was a statistically significant difference in nerve gliding between the positions (p=0.001). During active digital movement, the proximally oriented nerve gliding was observed from 0.8 (in the hook) to 1.3mm (in the grasp). There was a significant difference in nerve gliding between the two ways of active finger motions (p=0.001). On the basis of the data obtained from this study, it is concluded that forearm supination is the preferred position for the passive median nerve gliding exercise because of large distally oriented nerve gliding. The active digital motion with full finger grip may be an effective procedure to produce proximally oriented median nerve gliding.     

In vivo scaphoid, lunate, and capitate kinematics in flexion and in extension

Carpal kinematics have been previously limited to in vitro models with cadaveric specimens. Using a newly developed markerless bone registration algorithm, we noninvasively studied the in vivo kinematics of the capitate, scaphoid, and lunate during wrist extension and flexion in both wrists of 5 men and 5 women. Computed tomography volume images were acquired in neutral and in 2 positions in both extension and flexion. The 3-dimensional kinematics of the capitate, scaphoid, and lunate relative to the radius were the determined. Scaphoid and lunate rotations differed for flexion and extension but were found to vary linearly with capitate rotation. In flexion the scaphoid contributed 73% of capitate motion and the lunate contributed 46%. In extension the scaphoid contributed 99% of capitate motion and the lunate contributed 68%. Contributions of the scaphoid and lunate to wrist extension were 15% greater than values reported in previous in vitro studies, while scaphoid and lunate contributions to wrist flexion were more similar to previous studies. The findings support a relative "engagement" of the scaphoid, capitate, and lunate during wrist extension. The only difference between male and female kinematics was a more distal location of the rotation axes; we believe this was due to a difference in carpal bone size, not gender. This study reports the 3-dimensional in vivo measurement of carpal motion using a noninvasive technology. This technique may prove useful in the study of more complex motions of the hand and wrist and of the abnormal kinematics that occur following ligamentous injury.     

Traumatic longitudinal disruption of the carpus

Traumatic longitudinal disruption of the carpus is a rare injury that usually occurs through a weak point between the third and fourth metacarpals and the capitate and hamate. Three cases are reported; all injuries were work related and occurred with a broad crushing injury to the hand and wrist. Two patients were treated by fasciotomies, a carpal tunnel release, and excision of a fractured hook of the hamate. The third patient was treated with carpal tunnel release and percutaneous pinning of a wide diastasis. Despite the return of wrist motion, pinch and grip strength remained below normal range in all three patients at follow-up examinations.     

Evaluation of Dynamic Carpal Arch Stability following Carpal Tunnel Release Using Four-Dimensional Computed Tomography

Introduction  This study aimed to assess the carpal arch dynamics during active finger and wrist motion following carpal tunnel release using four-dimensional computed tomography (4D-CT). Materials and Methods  Four patients who diagnosed with bilateral carpal tunnel syndrome and underwent unilateral carpal tunnel release were prospectively included. 4D-CT of the bilateral wrists during active finger and wrist motion was performed for 10 seconds at five frames per second. The distances between the tip of tuberosity of the scaphoid and the volar ridge of the pisiform (S–P distance) and volar ridge of trapezium and the tip of hook of hamate (T–H distance) were measured at each position and the values of S–P and T–H distances were compared between the postoperative and contralateral wrists. Results  During finger motion, the S–P and T–H distances were not different at any position between the postoperative side and contralateral side. Conversely, S–P and T–H distances gradually increased in the postoperative wrists. The differences between the sides of S–P distance were significant, with >0 degrees of wrist extension, and differences of T–H distance were significant with >15 degrees of wrist extension. Conclusion  This study demonstrated the carpal arch dynamics using 4D-CT and revealed that the carpal arch was widened with the wrist in extension after carpal tunnel release. This study suggests that the transverse carpal ligament plays an important role in maintaining carpal arch stability.     

The effects of wrist distraction on carpal kinematics

Changes in carpal kinematics under wrist distraction were studied in fresh cadaveric specimens. A magnetic tracking device measured kinematic motions of the scaphoid, lunate, and third metacarpal relative to the fixed radius in 3 planes of passive motion (coronal, sagittal, and "dart throwers") under progressive distraction loads. The change in percent contribution of the radiocarpal and midcarpal joints was calculated. Radiocarpal motion during extension was decreased as increasing traction was applied, but it increased with flexion. Motion of the scaphoid relative to the lunate was smaller in the oblique plane, resulting in less radiocarpal motion than in the sagittal plane. In the coronal plane, traction had little effect on radial deviation, but ulnar angulation of the scaphoid was greater with ulnar deviation of the wrist. These results suggest that different degrees of tension exist in the palmar and dorsal ligaments with the wrist under traction and during different planes of wrist motion. If wrist motion is desired during fixed traction, such as used clinically with external fixation, the dart-throwers motion (wrist extension with radial deviation and wrist flexion with ulnar deviation) appears to have the least impact on radiocarpal motion. If greater radiocarpal motion is desired, however, such as during postoperative mobilization, flexion-extension and radioulnar deviation will create more radiocarpal motion than the dart-thrower's motion.     

Carpal arch alteration after carpal tunnel release

A retrospective clinical study quantitated postoperative widening of the transverse carpal arch after carpal tunnel release in a group of 50 patients. The relationship of this widening with postoperative pain, forearm circumference, grip strength, and wrist range of motion was evaluated. Mean widening of the transverse carpal arch after carpal tunnel release is 10.4% or 2.7 mm. A direct relationship exists between widening of the transverse carpal arch and loss of grip strength. Residual pain, forearm circumference, and wrist range of motion are not related to widening of the transverse carpal arch.     

Effect of wrist posture on carpal tunnel pressure while typing

Long weekly hours of keyboard use may lead to or aggravate carpal tunnel syndrome. The effects of typing on fluid pressure in the carpal tunnel, a possible mediator of carpal tunnel syndrome, are unknown. Twenty healthy subjects participated in a laboratory study to investigate the effects of typing at different wrist postures on carpal tunnel pressure of the right hand. Changes in wrist flexion/extension angle (p = 0.01) and radial/ulnar deviation angle (p = 0.03) independently altered carpal tunnel pressure; wrist deviations in extension or radial deviation were associated with an increase in pressure. The activity of typing independently elevated carpal tunnel pressure (p = 0.001) relative to the static hand held in the same posture. This information can guide the design and use of keyboards and workstations in order to minimize carpal tunnel pressure while typing. The findings may also be useful to clinicians and ergonomists in the management of patients with carpal tunnel syndrome who use a keyboard. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:1269–1273, 2008     

Segmental motion of the proximal carpal row: their global effect on the wrist motion

The contribution of the scapho-lunate and luno-triquetral joints to global wrist motion was studied in 11 fresh-frozen cadaver specimens. The carpus were labeled with metallic markers and the joints were selectively transfixed with wires. The wrist was allowed to follow its natural radial and ulnar deviation during flexion and extension, extension and flexion during radial and ulnar deviation, respectively. The data was collected by means of radiography, goniometric measurement, and computer analysis. The proximal carpal row (the intercalated segment) although anatomically represented as a row, presented through its two intersegmental joints, a definite segmental behavior. Each intersegmental joint of the proximal carpal row influenced global wrist motion in all directions but to a different degree for each plane of motion. The segmental joints within the intercalated segment collectively govern 40% of the wrist flexion, 33% of extension, and 10% of ulnar deviation. The scaphoid through its scapho-lunate link exerts a governing effect on total intersegmental proximal carpal row contribution to the global wrist motion.