Rotator Cuff Muscles Lose
Responsiveness to Anabolic Steroids After Tendon Tear and Musculotendinous
Retraction: An Experimental Study in Sheep

Gerber C, Meyer DC, Von
Rechenberg B, Hoppeler H, Frigg R, Farshad M.
Am J Sports Med. 2012 Sep 28.
[Epub ahead of print]

Chronic rotator cuff tears have demonstrated several
adaptations that have detrimental effects on a successful repair.  Many of these adaptations have involved the
rotator cuff muscles, including atrophy, fatty infiltration, decreased
pennation angle, and work capacity. 
Previously, it has been demonstrated that anabolic steroid given at the
time of injury prevents muscle atrophy and fatty infiltration in a rabbit model
inducted with chronic rotator cuff tearing. 
However, it is not known if pharmaceutical stimulates (anabolic steroid or
insulin-like growth factor [IGF]) can restore muscle properties once atrophy
and fatty infiltration have occurred. 
Therefore, Gerber et al. examined effects of anabolic steroid and IGF
following a chronic rotator cuff tear in a sheep model.  They used 20 Swiss alpine sheep and performed
a surgical osteotomy of the infraspinatus tendon
(separating the boney attachment of the tendon from the rest of the bone).  During surgery they measured active and passive
tension of the musculotendinous unit as well as work capacity of the
muscle.  Computed tomography (CT) was
used to measure the amount of tendon retraction and fatty infiltration at 2
week intervals.  The tendon was left
detached for 4 months, which provided adequate time to allow for muscle atrophy
and fatty infiltration to develop.  In
addition, at the 4 month time point, a continuous traction device was
surgically implanted which slowly repositioned the tendon to its anatomic footprint,
minimizing tension on the repair.  At
this time, and every two weeks, a CT scan was taken and the muscle injected
with anabolic steroid for the steroid group (7 sheep).  For the IGF group (6 sheep), the muscle was
only injected following surgery but was continually released by microspheres
over the same time period as the anabolic steroid group.  The control group (7 sheep) didn’t receive
any injections.  After 6 weeks the
rotator cuff tendon was surgically repaired. 
Measurement of muscle work capacity was repeated during this
surgery.  The animals were then left to
heal for an additional 12 weeks, work capacity measured, and tissue harvested
bilaterally to examine fatty infiltration and percent of type I muscle fibers
They found that continuous traction increased musculotendinous unit
length for all groups.  Fatty
infiltration also increased, however, muscle cross-sectional area, fiber type,
and work capacity decreased in all groups compared to the contralateral
side.  Additionally, the anabolic steroid
group had significant increases in work capacity and muscle fiber area on the
contralateral side compared to the other group’s contralateral side. 

This is a very interesting study that helps clinicians
further understand the muscular adaptations caused by chronic rotator cuff
tears, as well as possible treatment options. 
Previous research demonstrated that anabolic steroid administered to an
acute rotator cuff tear prevented the development of fatty infiltration and
muscle atrophy.  Clinically, most rotator
cuff tears develop from chronic microtrauma prior to becoming symptomatic,
displaying signs of fatty infiltration and atrophy.  The results of this study suggest that the
administration of anabolic steroid or IGF cannot reverse the muscular atrophy
and fatty infiltration once present within the rotator cuff muscle.  To date, no surgical or pharmaceutical
options can reverse muscular alterations after they have progressed.  It is possible that the lack of results from
anabolic steroid or IGF is caused by an injury to the suprascapular nerve that
is not treated properly.  Future research
should focus on a variety of specific neuromuscular treatments that may allow a
prevention or reversal of the muscular alterations.  However, the current and best recommendation
is to surgically treat rotator cuff tears prior to muscular alterations to
improve the likelihood of successful functional outcomes.  What is your experience with treating
patients with chronic rotator cuff tears? 
What types of rehabilitation exercises work best for you? 
Written by: 
Stephen Thomas
Reviewed by: Laura McDonald

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Gerber C, Meyer DC, Von Rechenberg B, Hoppeler H, Frigg R, & Farshad M (2012). Rotator Cuff Muscles Lose Responsiveness to Anabolic Steroids After Tendon Tear and Musculotendinous Retraction: An Experimental Study in Sheep. The American Journal of Sports Medicine PMID: 23024152