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Wrist Position (wrist + position)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

Gliding resistance of the extensor pollicis brevis tendon and abductor pollicis longus tendon within the first dorsal compartment in fixed wrist positions

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 2 2005
Keiji Kutsumi
Abstract Purpose: While the etiology of de Quervain's disease is unknown, repetitive motion coupled with awkward wrist position and septation within the first dorsal compartment are considered causative factors. We hypothesize that these conditions might produce high gliding resistance, which could then induce micro-damage of the tendons and retinaculum. The purpose of this study was to measure the gliding resistance of the extensor pollicis brevis and abductor pollicis longus tendons within the first dorsal compartment in a human cadaver model. Methods: Fifteen human cadaver wrists, which included eight septation and seven non-septation wrists in the first dorsal compartment, were used. Gliding resistance of the extensor pollicis brevis and abductor pollicis longus tendons was measured in seven wrist positions: 60° extension, 30° extension, 0°, 30° flexion, 60° flexion in neutral deviation and 30° ulnar deviation, 15° radial deviation in neutral extension/flexion. Results: The overall gliding resistance was not different between septation and non-septation wrists (0.21 versus 0.19 N for abductor pollicis longus and 0.21 versus 0.15 N for extensor pollicis brevis, respectively), but there was a significant effect on gliding resistance due to wrist position (p < 0.05) in both tendons. Interaction between wrist position and septation status was observed in the extensor pollicis brevis tendon (p < 0.05). With septation, the gliding resistance of the extensor pollicis brevis was significantly higher in 60° wrist flexion (0.51 N) compared to all other wrist positions tested (all less than 0.26 N) (p < 0.05). In the non-septation group, gliding resistance was significantly higher in 60° flexion (0.20 N) and 60° extension (0.22 N) compared to the other five wrist positions (all less than 0.15 N) (p < 0.05). Although no significant difference was observed, the extensor pollicis brevis tendon with septation tended to have higher gliding resistance than that without septation in wrist flexion. In 60° of wrist flexion the abductor pollicis longus tendon had significantly higher gliding resistance (0.33 N) than the other wrist positions (all less than 0.26 N) (p < 0.05). Conclusions: A combination of septation and wrist position significantly affected extensor pollicis brevis tendon gliding resistance in this cadaver model. These factors may contribute to the development of de Quervain's disease. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source]

Effect of elbow position on canine flexor digitorum profundus tendon tension

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 2 2005
Tatsuro Tanaka
Abstract Tendon injury in the finger remains a clinical challenge to hand surgeons. A canine model is commonly used to study biological effects of tendon injuries and their treatment. There is an important anatomical difference between human and canine anatomy that may be overlooked, however, namely that most of the flexor digitorum profundus (FDP) muscle in dogs takes its origin from the medial epicondyle of the humerus, whereas in humans this muscle arises purely from the forearm. Therefore, elbow position can affect the tension of this muscle in dogs, while having no effect in humans. The purpose of this study was to measure the effect of elbow position on tendon tension in the canine digit in vitro. Elbow position had a significant effect on tendon tension. Digit motion with the elbow fully flexed resulted in significantly higher tendon tension compared to digit motion with the elbow flexed 90° or fully extended, regardless of digit or wrist position (p < 0.05). The tension with the elbow flexed 90° was also significantly higher than with the elbow fully extended (p < 0.05). The maximum tendon tension with the elbow fully flexed was more than eight times larger than that of the fully extended elbow (p < 0.05). We conclude that, in the canine model, elbow position is an important parameter that affects the passive tension applied to the flexor digitorum profundus, and, by implication, to any repair of that tendon. Dog flexor tendon rehabilitation protocols should therefore specify elbow position, in addition to wrist and digit position. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source]

Time-varying changes in corticospinal excitability accompanying the triphasic EMG pattern in humans

THE JOURNAL OF PHYSIOLOGY, Issue 3 2000
Colum D. MacKinnon
1Nine healthy subjects performed single rapid wrist movements from neutral to targets at 20 deg of flexion or extension in response to an auditory cue. Surface EMG was recorded from the wrist flexors and extensors together with wrist position. Movements in both directions were characterised by the usual triphasic pattern of EMG activity in agonist (AG1), antagonist (ANTAG) and again in agonist (AG2) muscles. 2Single pulses of transcranial magnetic stimulation (TMS) were applied over the motor cortex at an intensity of 80 % of resting threshold at random times between 80 and 380 ms after the cue. We measured the peak-to-peak amplitude of the evoked motor potential (MEP) and the integrated EMG (IEMG) activity that preceded the MEP. In a separate set of experiments H reflexes were elicited in the wrist flexors instead of MEPs. 3MEP amplitudes in the agonist muscle increased by an average of 10 ± 8 ms (range ,1 to 23 ms) prior to the onset of the AG1 burst and were associated with an increase of over sevenfold in the MEP:IEMG ratio, irrespective of movement direction. Agonist H reflex amplitudes were linearly related to, and increased at the same time as, changes in agonist IEMG. 4The principal ANTAG burst was not preceded by an increase in the antagonist muscle MEP:IEMG ratio. No relationship was found between the amplitude of the antagonist H reflexes and the preceding antagonist IEMG. 5Five subjects showed an increase in the MEP:IEMG ratio preceding and during the initial part of the AG2 burst. 6Our method of analysis shows that changes in motor cortical excitability mediating the initiation of movement occur much closer to the onset of EMG activity (less than 23 ms) than the 80,100 ms lead time previously reported. The lack of such changes before the onset of the ANTAG burst suggests that this may be initiated by a different, perhaps subcortical, mechanism. [source]

Gliding resistance of the extensor pollicis brevis tendon and abductor pollicis longus tendon within the first dorsal compartment in fixed wrist positions

The effects of partial and total interosseous membrane transection on load sharing in the cadaver forearm

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 4 2001
Michael F. Shepard
This study was performed to examine the effects of partial and total transection of the interosseous membrane (IOM) on load transfer in the forearm. Twenty fresh frozen forearms were instrumented with custom designed load cells placed in the proximal radius and distal ulna. Simultaneous measurements of load cell forces, radial head displacement relative to the capitellum, and local tension within the central band of the IOM were made as the wrist was loaded to 134 N with the forearm at 90° of elbow flexion and in neutral pronation supination. For valgus elbow alignment (radial head contacting the capitellum), mean force carried by the distal ulna was 7.1% of the applied wrist force and mean force transferred from radius to ulna through the IOM was 4.4%. For varus elbow alignment (mean 2.0 mm gap between the radial head and capitellum), mean distal ulna force was 28% and mean IOM force was 51%. Section of the proximal and distal one-thirds of the IOM had no significant effect upon mean distal ulnar force or mean IOM force. Total IOM section significantly increased mean distal ulnar force for varus elbow alignment in all wrist positions tested. The mean level of applied wrist force necessary to close the varus gap (89 N) decreased significantly after both partial IOM section (71 N) and total IOM section (25 N). The IOM became loaded only when the radius displaced proximally relative to the ulna, closing the gap between the radius and capitellum. As the radius displaced proximally, the wrist becomes increasingly ulnar positive, which in turn leads to direct loading of the distal ulna. This shift of force to the distal ulna could present clinically as ulnar sided wrist pain or as ulnar impaction after IOM injury. © 2001 Orthopaedic Research Society. Punlished by Elsevier Science Ltd. All rights reserved. [source]