Does Palmaris Brevis Structure Allow for Protection Against Prolonged Overlying Compression? An Ultrasound and Immunohistochemical Investigation
Notice bibliographique
Résumé
Introduction The palmaris brevis (PB) is small hand muscle located superficial to the hypothenar eminence in the medial palm. Although this muscle may have variant morphology, its complete absence is considered rare (<3%) compared to its counterpart, the palmaris longus, whose absence is more frequent (14%). From cadaveric studies, PB function has been postulated to protect the neurovasculature of the ulnar tunnel from prolonged overlying compression; however, it is unknown whether the PB has the gross histological structure and fatigue resistance necessary for prolonged contraction. Therefore, the initial objective was to determine the fiber‐type composition of the PB by staining for myosin heavy chain (MHC) type I (slow‐twitch) and type II (fast‐twitch) isoforms in cadaveric specimens. When the PB contracts, it has the potential to create a muscular barrier to protect the neurovasculature of the ulnar tunnel; however, the extent of change in PB dimensions from rest to maximal contraction remains unknown. Previous PB electromyographic investigations recorded the greatest muscle activity during maximal abduction of the 5 th digit, but it is unknown whether significant changes in muscle architecture (length and thickness) occur during this contraction. Thus, the second objective was to investigate and quantify the dynamic changes in PB morphology using ultrasound imaging in young participants. Methods To date, fiber‐type proportions have been quantified from 5μm cross‐sections of 4 PB muscles (3 left and 1 right) from 3 cadaveric specimens (2 Females, 1 Male; age: 80 ± 1 y) using immunohistochemistry by staining for MHC type I and MHC type II. Type I and type II fibers were manually counted using ImageJ software from 3 sites per slide from each specimen. Architectural changes in PB muscle length and thickness were investigated in the left and right hands of 8 male participants (age: 27 ± 4 y). Ultrasound images were taken at rest and during maximal abduction of the 5 th digit. Results The cadaveric PB specimens displayed a homogenous fiber‐type distribution with a mean fiber ratio of 71% slow‐type (range: 62–82%) to 29% fast‐type (range: 18–38%). Upon PB muscle contraction, a 26% and 28% decrease in mean muscle length was observed in the left and right hands, respectively. A concomitant increase in mean PB muscle thickness of 40% and 48% was also observed in the left and right hands respectively. Conclusion The preponderance of MHC slow‐type isoform relative to fast‐type in the PB render the whole muscle with fatigue resistant contractile properties that would allow the muscle to remain contracted during prolonged grasping tasks. Considering the muscle fiber type proportions along with the significant changes in muscle length and thickness observed with ultrasound imaging supports the supposition that the PB is capable of acting as a thick muscular barrier to the contents of the ulnar tunnel during a movement known to elicit the greatest EMG activity. Support or Funding Information Supported by NSERC
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,001 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».