Electromyographic activities of the biceps during arm elevation in shoulders with rotator cuff tears

Tadato Kido, Eiji Itoi, Norikazu Konno, Akihisa Sano, Masakazu Urayama, Kozo Sato

Research output: Contribution to journalArticlepeer-review

19 Citations (Scopus)

Abstract

We investigated electromyographic activities of the biceps in 40 shoulders with full-thickness tears of the rotator cuff and 40 asymptomatic shoulders, with a normal rotator cuff on MRI, to determine the role of the biceps in cuff-deficient shoulders. Using surface electrodes, biceps activities were recorded during arm elevation in the scapular plane with and without a 1-kg load. The percentages of integrated electromyograms to the maximum voluntary contraction (%MVC) were obtained at 30°, 60°, 90°, and 120°of elevation. In the normal shoulders, %MVC of the biceps was always less than 10% through the arc of elevation both with and without load. Among 40 shoulders with rotator cuff tears, 14 showed increased activities of the biceps more than 10% in %WVC (p < 0.0001), whereas the remaining 26 shoulders had activities similar to the normal shoulders. The biceps activities in these 14 shoulders increased with load application and at higher angles of elevation. The muscle strength tended to be weaker in shoulders with increased biceps activities than in those without. Our findings suggest a potential supplemental function of the biceps in shoulders with rotator cuff tears.

Original languageEnglish
Pages (from-to)575-579
Number of pages5
JournalActa Orthopaedica Scandinavica
Volume69
Issue number6
DOIs
Publication statusPublished - 1998
Externally publishedYes

ASJC Scopus subject areas

  • Surgery
  • Orthopedics and Sports Medicine

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