POSTER ABSTRACTS - ISAKOS

the glenoid cavity were 26.9±0.7 mm, 15.1±1.4
mm, 3.9±1.8 mm.
The rotator cuff geometrical measurements was
measured interpolating the bone surface with
polygonal facets. The infra-spinatus insertion area
was 170±23 mm, and his distance from the
humeral head was 38.4±0.3 mm. The supraspinatus
insertion area was 170.2±19 mm and his
distance from humeral head was 33.8±0.7 mm.
A second group of results concerned the rotator
cuff behavior during passive motion.
The rotator cuff behavior was analyzed through
the distance between muscle insertion on the
humeral head and reference points on the
scapula.
The distance of center of supra and infra- spinatus
insertion from coracoids, acromion and ligaments
coraco-acromial was similar and the standard
deviation due to repeated motions overcomes the
difference between the two tendons.
The distance of infra and supra-spinatus from
these points decreased during abduction up to
35% and during elevation up to 25%, even if
absolute value depended on the specimen.
During internal-external stress tests both infra
and supra-spinatus showed the minimal distance
from acromion, coracoid and coraco-ligament
ligament at extreme internal rotation in almost all
cases. The internal rotation of the shoulder
ranged between 30 and 40 and the minimal
distance of infra and supra-spinatus from the
scapular was similar (but in a few cases infraspinatus
had a smaller minimum with respect to
supra-spinatus).
We also examinated 4 different fibers of the same
muscle. Fibers of the same specimen had different
length at neutral position (up to 60 mm) , ranging
from 120 to 140 mm for infra-spinatus fibers and
125 to 140 mm for supra-spinatus fibers. All the
fibers showed the same elongation pattern during
passive elongation and abduction and extreme
positions: they decreased their length in a
variable way from 5% to 25%. During IE test, the
minimum distance from acromion and coracoid
was achieved at internal rotation except for single
fibers or case.
Discussion
This study showed no significant differences
between the supraspinatus and infraspinatus
behaviour with respect to the acromion , coracoid
and the coraco-acromial ligament. This confirm
that both muscles have similar function in the
joint, generating the torque and compression for
humerus rotation on the glenoid cavity [6].
Examining the distance of their humeral insertion
areas from the scapula, we concluded that the
most critical positions are near the maximum
passive abduction, maximum elevation and
maximum internal rotation. These data confirm
that during overhead sports the higher degree of
motion are the one at the most risk for cuff lesion.
The fact that in several specimens the minimal
distance between infra-spinatus and supraspinatus
and scapula was achieved with the
coraco-acromial ligament confirmed the
importance of this structure in the impingements
mechanism and rotator cuff disease [4,7]. These
data could also be important for surgical release
of this ligament especially in athletes thrower.
These can suggest indications for explaining the
patho-physiology of impingements, as it provides
numerical distances of infraspinatus and
sovraspinatus from the coracoid and acromion.
Further planned elaborations on a more extensive
number of specimen will help in increasing
knowledge of functional behavior of shoulder
structures.
References
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Mow, Bigliani Excursion of the rotator cuff iunder
the acromion The American Journal of Sport
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2. Halder, Zobitz, Schultz Mechanical proprierties
of the posterior rotator cuff Clinical Biomechanics
(2002) vol.15, 456-462.
3. Martelli S., New method for simultaneous
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Comp & Method in Biomed 70 (2003), 223-240.
4. Volk, Vangsness An anatomic study of the
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Orthopaedics and Related Research 384 (2001),
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Anatomy and study of rotator cuff insertion
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Biomechanics of the rotator cuff Orthopaedic
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