Comparison of two methods for computing abduction moment arms of the rotator cuff

Richard E. Hughes, Glen Niebur, Jain Liu, Kai Nan An

Research output: Contribution to journalArticlepeer-review

62 Scopus citations


Biomechanical models of the shoulder mechanism require estimates of muscle moment arm magnitude. Some shoulder models have estimated muscle moment arms by assuming an idealized minimum distance path from the origin to insertion that passes around the bony geometry. Alternatively, the principle of virtual work can be used to estimate moment arms from tendon excursion and joint-angle data. The purpose of this study was to determine if these two methods give different estimates of abduction moment arms for the supraspinatus, infraspinatus, and subscapularis muscles. Muscle moment arms were estimated for these muscles on ten fresh frozen cadaver specimens. The results showed a significant difference between the two estimation methods. Average differences were 3.1 mm (10.6%), 3.9 mm (43.9%), and 7.2 mm (70.3%) for the supraspinatus, subscapularis, and infraspinatus muscles, respectively. These results suggest that shoulder models based on the origin-insertion method may give higher rotator cuff muscle force estimates than methods using the slope of the tendon excursion vs joint angle relationship.

Original languageEnglish (US)
Pages (from-to)157-160
Number of pages4
JournalJournal of Biomechanics
Issue number2
StatePublished - May 12 1997


  • Abduction
  • Biomechanics
  • Moment arms
  • Rotator cuff

ASJC Scopus subject areas

  • Biophysics
  • Orthopedics and Sports Medicine
  • Biomedical Engineering
  • Rehabilitation


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