Article
The abduction system of the fifth finger. An anatomic and electromyographic study
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Authors
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Daniel Postan
- Buenos Aires Medical Scool, Buenos Aires, Argentina
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Luciano Poitevin
- Buenos Aires University Hospital, Buenos Aires, Argentina
| Published: | February 6, 2020 |
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Outline
Text
Objectives/Interrogation: The purpose of this research is to study the role of the EDQ and the hypothenar muscles in the abduction of the fifth finger in a cadaveric and electromyography study.
The abductor digiti quinti and flexor digiti quinti are both typically considered the prime abductors of the fifth finger. This movement can be impaired in clinical situations such as ulnar neuropathies and post-burn scars on the hypothenar region.
The extensor digiti quinti (EDQ) has been used as a tendon transfer and there is evidence that Its rerouting improves the abduction of the fifth finger.
However, the abduction ability of the EDQ compared to the hypothenar muscles, has not been studied so far, to our knowledge.
Does the EDQ have an abduction action?
Methods: 10 cadaveric fresh frozen hands were studied. A 1.5 Newton traction was sequentially exerted on the abductor digiti quinti, flexor digiti quinti and EDQQ. The resultant angle between the fourth and fifth finger was measured.
5 volunteer healthy patients were studied by means of an electromyography protocol. While performing abduction of the fifth finger, the electric activity on the hypothenar eminence and the extensor digiti quinti was recorded.
Results and Conclusions: The EDQ abducted the finger 32.4° in average (CI95% 28.62-35.38), the abductor digiti quinti 39.9° (CI95% 35.22-44.58), and the flexor digiti quinti 31.2° (CI95% 26.21-36.18). There are significative statistical differences (p>0.05) between the degrees abducted by the EDQ and the flexor and abductor digiti quinti. During abduction, the electromyography noted synergic activity between the hypothenar muscles and the EDQ
The fifth finger abduction system is constituted by two components: a) intrinsic - the hypothenar muscles, and b) extrinsic - the EDQ. Both elements act simulataneous and synergically. This fact may suggest that the extrinsic part may still be abducting the fifth finger even when the hypothenar component is absent. Even though the EDQ featured less abductor power than the abductor digiti quinti, the amount of angular variation in the cadaveric experiment suggest a significant abductor role of the EDQ in clinical situations.
