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W. Ben Kibler, MD
John McMullen, ATC ABSTRACT Scapular dyskinesis is term used to
describe the loss of normal scapular motion as seen clinically.
Dysfunction in scapular position and mechanics is seen in 100% of
cases of glenohumeral instability, 68% of those with abnormalities to the
rotator cuff, and 94% with labral tears.
Understanding the proper mechanics of the scapula and its relation
to the trunk and the humerus is necessary to ensure proper rehab and
resolution of the patient’s problem. The primary role of the scapula is
to maintain the humeral head and its anatomical axis as the humerus
undergoes motion. Its
secondary function is to provide motion along with thoracic wall, either
as a movable platform, or as a stabilizing platform as seen with overhead
workers. A third role is to provide elevation of the acromion during
cocking and throwing motions to prevent impingement, and a last role is as
a final link in the proximal to distal sequencing of energy, force and
velocity as seen when throwing. The
arm musculature itself is not really enough to propel a ball, and the
body, legs, and scapula all assist in transferring energy into the arm in
order to throw. It also
serves to absorb some of the energy generated by the overextended or
elevated arm. Scapular dyskinesis can occur due
to multiple different situations. One
may be an abnormality in bony posture or injury. Excessive resting kyphosis creates a situation where there is
excessive scapular protraction and arcomial depression in all stages of
motion, increasing the risk for impingement.
AC joint injuries or instabilities can alter the center of rotation
of the scapula, leading to faulty mechanics. Muscle function alterations,
especially involving the serratus anterior and lower trapezius, are a
common source of dysfunction, especially in cases of secondary
impingement. Nerve damage is
a rare cause, and more common causes include trauma to the muscle itself,
microtrauma due to excessive strain in the muscles, fatigue, and
inhibition due to pain. The
serratus and low trapezius are the two muscles that are most susceptible
to inhibition, and weakness to these is seen more often in the early phase
of the problem. Contractures, especially of the
anterior musculature that attaches to the coracoid process (pectoralis
minor and short biceps head) can create an anterior tilt and forward lean
to the scapula, as can tightness to the posterior capsule and latissimus.
Forward head posture creates tightness to the anterior neck
musculature, which again in turn facilitates the abnormal scapula
position. There are 3 types of scapular
dyskinesis: Type I is
characterized by a prominence of the inferior medial scapular border, Type
II has the entire medial border protruding, and Type III has superior
translation of the entire scapula and prominence of the superior medial
border. When there is loss of scapular retraction, there is loss of a
stable cocking point in throwers, or a loss of the stable base for the
humerus in laborers. Lacking
full scapular protraction increases the deceleration forces during a
throw, especially at the shoulder. Too
much protraction due to tight anterior structures or a tight posterior
capsule leads to impingement as the scapula rotates down and forward. Evaluation of the patient should
include trunk segments, hip and lower extremity function, and scapular
position and movement analysis. There
may be pain at the coracoid process, and the entire medial border may be
tender with trigger points found in the upper trapezius.
There may even be painful scar tissue found in the musculature due
to long standing dyskinesis. Motion
about the scapulothoracic joint should be smooth with no catching or rapid
movements, which are more often seen during the lowering phase of the arm.
Strength testing can include
isometric scapular pinch, the scapular assistance test, the scapular
retraction test, and the lateral scapular slide test.
Once all the factors involved in the dysfunction of the shoulder
are identified, treatment can begin on restoring normal scapular position
and movement. More extensive
therapy, including strengthening, should not occur until this step is
accomplished, otherwise the shoulder is being worked in a faulty position,
which could lead to soreness. The acute phase, or weeks 0-3,
include modalities such as ultrasound and electrical stimulation, massage
to loosen up tight musculature, stretching of tight structures (including
the latissimus, upper trapezius, levator scapulae, pectoralis minor,
infraspinatus, and teres minor), and closed chain exercises to facilitate
stability. Active trunk
extension, lateral trunk rotation, and hip extension can be used to
facilitate scapular retraction. The
recovery phase, from 3-8 weeks, adds on more aggressive closed chain
exercises, along with tubing exercises incorporating trunk and hip motion
with scapular motion, and avoidance of scapular compensations such as
shrugging and winging are suppressed.
The maintenance phase, from 6-10 weeks, adds on plyometric
exercises and overhead dumbbell presses and punches. COMMENTS A very long article that is tough
to abstract without reproducing the entire article, or leaving too much
material out. The authors are
trying to point out that in many cases, the dysfunction of the scapula
leads to the problems seen with throwing athletes and overhead laborers.
If one does not address these factors, and just tackles the
glenohumeral joint, he/she may be doing the patient an injustice.
There are going to be cases where there are bony or anatomical
factors that the PT cannot control (AC joint separation, old clavicle
fracture, scarring to certain shoulder tissues from long-standing
problems, etc), but most of the cases are purely muscular in nature, and
can be treated. In some
instances, the muscle dysfunction caused the problem seen with the
patient, in others some type of injury set off a pain-inhibition chain of
events that caused the pain. A
combination of both is also quite likely. The authors do a great job of
photographing and describing the different tests for the scapula, but then
fail miserably when describing the rehabilitation.
Numerous exercises are mentioned, with no explanation given, so one
has to hunt elsewhere for definitions.
The exercises that include photos do not give good descriptions as
to exactly what the patient is doing in the photo, so that the program
could be reproduced in the clinic. Lastly,
the protocol printed is somewhat confusing, uses many terms for exercise I
have never heard, and is quite long for the typical HMO patient. Regardless, the article is one of
the must-reads for any PT/ATC that treats throwing athletes.
I will take photos myself in the near future to describe the 4
tests used to determine if there may be a dyskinesis during an evaluation.
I will also try to create photo images of some of the exercises as
they suggest.
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