Article
In-vivo Function of Pronator Teres as a Dynamic Stabilizer of the Elbow Joint
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Authors
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Mineo Oyama
- Graduate School of Niigata University of Health and Welfare, Niigata, Japan
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Hiroaki Koizumi
- Graduate School of Niigata University of Health and Welfare, Niigata, Japan
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Masahiro Odagiri
- Graduate School of Niigata University of Health and Welfare, Niigata, Japan
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Shota Matsuzawa
- Graduate School of Niigata University of Health and Welfare, Niigata, Japan
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Chihiro Fujime
- Graduate School of Niigata University of Health and Welfare, Niigata, Japan
| Published: | February 6, 2020 |
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Outline
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Objective: The pronator teres locates on the medial side of the elbow, which has two heads, one is ulnar head (UH) and the other is humeral head (HH). It was not obvious how these heads work relate to the stability of the elbow in-vivo. The purpose of this study was to examine activities of the two heads during varus movement of the elbow and grounding using a hand during the falling down.
Materials and Methods: This experiment was carried out on six normal subjects. They all signed an informed consent form.
The experimental tasks were active varus movement of the right elbow during maximum effort and grounding using a right hand during the falling down. Intramuscular bipolar wire electrodes were used for recording muscle activity. The placements of the electrodes were confirmed by viewing displays of the ultrasonic image.
The integration was performed every 100 ms. The integrated EMG values were normalized by converting them to a percent of the maximum voluntary contraction recorded during manual muscle testing (NIEMG).
Results: The NIEMG of the HH was about 20 % and the UH about 45 % during varus movement. Regarding a comparison of NIEMG between the two heads, the UH was significantly higher than the HH (P<0.05).
The activity of the UH increased from 200 ms before to 400 ms after grounding in forearm pronation. The NIEMG of the UH increased with steep and reached about 30 % at 100 ms before grounding and sustained after grounding, which were significantly greater than the HH (P<0.05). In forearm supination, the activities of both heads weren't observed.
Conclusions: We observed significant increase in the activity of the UH comparing with the HH. The anatomical study showed that the UH transitioned directly into the joint capsule just anterior to the medial ulna collateral ligament. Therefore, the findings of this study suggested that the UH might be a strong part as dynamic stabilizer. The activities just before grounding might be induced by the control system to stabilize the elbow effectively from predicted instability.
