SciCombinator

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Concept: Extensor pollicis brevis muscle

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A previous ultrasound study showed inflammation around the extensor pollicis longus tendon and surrounding structures at 6 weeks after manipulation, with or without pin fixation, and immobilization for distal radius fracture. Ultrasound examination after plating of distal radius fracture followed by early active mobilization of the wrist showed a short-lived inflammatory response, evident at 2 weeks but not at 6 weeks, around the extensor pollicis longus tendon (26 wrists examined) and flexor pollicis longus tendon (18 wrists examined). Early active mobilization of the wrist appears to limit the duration of inflammation around these tendons.

Concepts: Flexor digitorum profundus muscle, Wrist, Distal radius fracture, Flexor pollicis longus muscle, Extensor pollicis brevis muscle, Carpal tunnel, Flexor pollicis brevis muscle, Extensor pollicis longus muscle

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Strong evidence indicates that highly repetitive manual work is associated with the development of upper extremity musculoskeletal disorders (MSDs). One of the occupational activities that involves highly repetitive and forceful hand work is manual pipetting in chemical or biological laboratories. In the current study, we quantified tendon displacement as a parameter to assess the cumulative loading exposure of the musculoskeletal system in the thumb during pipetting. The maximal tendon displacement was found in the flexor pollicis longus (FPL) tendon. Assuming that subjects' pipetting rates were maintained constant during a period of 1h, the average accumulated tendon displacement in the FPL reached 29m, which is in the lower range of those observed in other occupational activities, such as typing and nail gun operations. Our results showed that tendon displacement data contain relatively small standard deviations, despite high variances in thumb kinematics, suggesting that the tendon displacements may be useful in evaluating the musculoskeletal loading profile.

Concepts: Variance, Standard deviation, Flexor pollicis longus muscle, Extensor pollicis brevis muscle, Michigan, Musculoskeletal system

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We investigated the flexor pollicis longus (FPL) tendon and median nerve in smartphone users by ultrasonography to assess the effects of smartphone addiction on the clinical and functional status of the hands.

Concepts: Ulnar nerve, Flexor pollicis longus muscle, Extensor pollicis brevis muscle, Carpal tunnel, Hand strength

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Background  We evaluated the detection for screw penetration on the dorsal cortex of the radius in serial oblique, dorsal tangential, and radial groove radiographic views in volar plating fixation. Materials and Methods  Eight screw positions were set in each of the four cadaveric radii. Screw 1 was placed in the styloid subregion, whereas screws 2 and 3 were placed just proximal to the styloid and were defined for the radial region of the radius. Screws 4 (distal to the extensor pollicis longus [EPL] groove), 5 (the distal half of the groove), and 6 (the proximal half of the groove) were placed in the central region of the radius. Screws 7 (just medial to the groove) and 8 (sigmoid notch subregion) were positioned in the ulnar region of the radius. The screws were overlengthened by 1 and 2 mm and were evaluated in three radiographic views. Results  Penetrations in the radial region were fully visible in supinated oblique views with 1- and 2-mm overlengthened screws. The penetration of screw 4 was clearly observable over a considerable range of views. However, the 1-mm penetration of screw 5 was not detectable at any angle of projection. Detection of the ulnar region screw was the most difficult among the three regions with oblique views. In the dorsal tangential view, the 1-mm penetration of screw 4 was not observed in any of the four radii, but the penetration of screw 5 was detectable in all the radii. The screws 2, 3, 5, 7, and 8 were readily detectable. The screw 4 was barely seen in the radial groove view, while the screws 5 and 6 were readily detectable. Conclusion/Clinical Relevance  Appropriate combinations of these well-known radiological views are essential for the overall detection of penetrated screws during plating in distal radius fractures.

Concepts: Ulna, Circle, Wrist, Distal radius fracture, Extensor pollicis brevis muscle, Region, Radial nerve, Oblique projection

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According to the anatomical literature, the extensor pollicis brevis (EPB) tendon passes through the first compartment and enters the base of the proximal phalanx of the thumb. There have been a few reports on the different types of supernumerary EPB tendons; however, an unusual course of the EPB tendon is extremely rare.

Concepts: Tendon, Extensor pollicis brevis muscle, Muscles of the upper limb, Thumb, Tendons

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Pediatric trigger thumb is regarded as an acquired condition characterized by flexion deformity of the interphalangeal joint of the thumb. However, the exact etiology and pathoanatomy of this condition remain unknown. The purpose of this study was to evaluate cross-sectional configurations of the flexor pollicis longus (FPL) tendon and the area under the A1 pulley quantitatively using ultrasonography.

Concepts: Knee, Flexor pollicis longus muscle, Extensor pollicis brevis muscle, Fingers

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Volar plates positioned at, or distal to, the watershed line have been shown to have a higher incidence of attritional rupture of the flexor pollicis longus (FPL). In this study, we aimed to evaluate the effect of wrist extension and volar tilt on the contact between the plate and the FPL tendon in a cadaver model. We hypothesized that, following volar plate application, loss of native volar tilt increases the contact between the FPL and the plate at lower degrees of wrist extension.

Concepts: Effect, Model theory, Flexor digitorum profundus muscle, Tendon, Flexor pollicis longus muscle, Extensor pollicis brevis muscle, Carpal tunnel, Extensor pollicis longus muscle

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The short-term joint immobilization induces a decrease of corticospinal excitability; however, detailed time course of the immobilization-induced central nervous system changes and their extent have not yet been clarified. To evaluate the time course of changes in corticospinal excitability during forearm/hand immobilization for 24 h and investigate the effect on muscle strength, adhesive casting tape was used to immobilize the nondominant forearm/hand. The amplitude of the motor-evoked potential of the flexor pollicis brevis muscle induced by transcranial magnetic stimulation was measured during immobilization and after cast removal. The muscle strength was evaluated after the termination of immobilization. The resting motor-evoked potential recorded from flexor pollicis brevis muscle showed a significant decrease 3 h after initiation of immobilization and gradually declined further until the end of immobilization. It then increased over 2 h after cast removal, but was still significantly below baseline. However, no significant difference from baseline was observed at 3 h. Both pinch power and integrated electromyogram were significantly reduced by immobilization, and then gradually returned to baseline after the cast was removed. These results indicate that short-term forearm/hand immobilization rapidly reduces corticospinal excitability, and this change is rapidly reversed after resumption of movement.

Concepts: Central nervous system, Nervous system, Spinal cord, Brain, Transcranial magnetic stimulation, Nerve, Flexor pollicis longus muscle, Extensor pollicis brevis muscle

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Isolated dorsoradial capsule injuries of the thumb metacarpophalangeal joint are different from those associated with collateral ligament disruption. Early suspicion of this rare injury is important because, if overlooked, ulnarward subluxation of extensor pollicis longus tendon can develop. Functionally, active thumb extension becomes impaired, and over the long term, a thumb Boutonniere’s deformity becomes established. Joint hypermobility/instability may predispose to this injury. The 2 cases presented illustrate this through anatomic differences. At the time of acute injury, 3 presenting clinical features should raise suspicion of dorsoradial capsular rupture: a history of isolated hyperflexion injury to the thumb, stable collateral ligaments on examination, and x-ray evidence of palmar subluxation of the proximal phalanx on the metacarpal. Ulnarward subluxation of the extensor pollicis longus is a delayed sign. Diagnostic imaging, beyond x-ray studies, may not be helpful in defining the injury. Early exploration and repair of this injury give the best long-term outcome. Postrepair, metacarpophalangeal joint range of motion may not be fully restored, but stability and a preinjury level of hand function can usually be reestablished.

Concepts: Osteoarthritis, Joint, Ligament, Tendon, Extensor pollicis brevis muscle, Metacarpophalangeal joint, Lumbricals of the hand, Flexor pollicis brevis muscle