• An, Kai-Nan (PI)
  • Morasso, Maria (PI)

Project: Research project

Project Details


In sports and certain occupational activities, persons use their bodies and
large muscles to generate momentum and energy which are then guided through
their shoulder to achieve the task. Injuries occur when the muscle and
soft tissue of the shoulder are requested to generate or dissipate such
load and energy beyond their capacities, either as a single event or on a
repetitive basis. It has been recognized in principle, based on clinical
experiences and limited laboratory studies, that the rotator cuff muscle
complex is functionally important to provide the power and maintain the
stability of the glenohumeral joint of the shoulder. Consequently, the
rotator cuff tendon will encounter relatively high stress, subjecting it to
potential injury. The three hypotheses regarding the rotator cuff are: a)
the integrated action of the rotator cuff muscle complex and deltoid muscle
exceeds the sum of their isolated contribution to shoulder strength; b)
rotator cuff muscles are either primary or secondary contributors to
glenohumeral constraint according to direction of displacement; and c) the
rotator cuff tendon is inadequate to withstand the load placed on it by
some activities; that is, the tendon encounters relatively high load in
reference to its failure strength. To test these three hypotheses, we
propose to accomplish the following six specific aims: 1) to measure the
moment arms of cuff muscles and the muscles crossing the glenohumeral joint
under selected functions and joint positions in vitro; 2) to measure the
shoulder strength of normal subjects and patients with defined cuff
pathology in selected functions; 3) to measure the displacement of the
humeral head under selected loadings: a) with and without cuff muscle
force, b) with and without capsuloligamentous constraints; 4) to develop
and verify an analytic model to predict the displacement tendencies of the
humeral head that must be constrained during joint and muscle loading; 5)
to calculate, analytically, the rotator cuff force under selected loading
and especially during overhead activities; 6) to measure the mechanical
properties of the cuff tendon and document the mode of failure.
Effective start/end date1/1/927/31/00


  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health: $134,882.00
  • National Institutes of Health
  • National Institutes of Health: $200,788.00
  • National Institutes of Health: $164,132.00
  • National Institutes of Health: $230,424.00


  • Medicine(all)


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