The shoulder joint is the articulation
between the held of the homers
and shallow glenoid fosse
of the scappppule. The glenoid fossse is only one third the size of the
humeral head, But it is depend
by a rim of cartilage
(glenoid labrum) attached to its periphery. The joint itself is surrounded by a
loose capsule is further strenghtened by the rotator cuff muscles which acts ass active
ligaments and blend with the lateral capsule. The 'roof' of the joint is formed by the
bony coracoid and acromion process and the coracoacromial ligamentswhich runs between
them; the three structures together forming an 'arch'.
Most joints have a high degree of passive
stability provided by their capsules and ligaments. The shoulder, however, depends more on
the active stability provided by its muscles to maintain joint integrity. In
the anatomical position the weight of the arm is largely supported by the coracohumeral
ligament and upper capsule. When the arm moves away from the side of the body, tension in
the superior capsule is immediately lost. Now joint stability is provided by only by the
rotator cuff muscles.
The'roof arch' protects the shoulders
joint proper from direct overhead trauma. It prevents upword displacement of the humerus
and it presents a mechanical obstruction to the humeral head ass the arm performs
obduction, forward and postrior flexion and overhead elevation. This limitation
constitutes the basis some of the pathologic processes that occur at this joint.
The suprra humeral joint space
contains subacromial bursa, the supraspppinatus muscle tension superior aspect of
glenohumeral capsule and portion of the bicaps tendon . This space gets reduced
by abduction of the arm which causes inpigment of these structures between
the head and acromion.
The muscular functions are static and
kinetic, the muscles most significant involved in the static support of shoulder
joint are deltoid and the suoraspinatus musclus. The supraspinatus muscle support the
weight of the upper extremity by sustained tonus. This is the principals muscles of static
support of the shoulder joint. It is also the principal kinetic muscle in
initiating movements and functionally moving the arm in abduction, forward and posterior
flexion, and external rotation with the glenoid fossa. It is the major component of
rotator cuff.
The other muscles forming the rotator cuff are
infraspinatus, teeries minor and sub-scaoularis. The first three are attached to greater
tuberosity and subscappppularis to lesser tuberosity.
Tears that occur within the rotator cuff
tendon are usually preceded by degenerative change as well as overwhelming traction and
compressive forces. These tears usually occur logitudinally in the anterior portion of
the cuff between the supraspinatus tendon and the coracuhumeral ligament at the 'critical
zone'.
This so called critical zone is the site within the
conjoined tendon where degenerative changes and tearing occur. It was called critical because it was
originally considered to be the region of vascular ischemia of the tendons.
The critical zone varies from ischemic when the anastomosis
is constricted and hypermic when it is allowed to flow freely. In the
dependent arm. which elongates and thus compresses the arterial flow, the area
is isocheim. In the elevated abducted, forward flexed arm when the rotator cuff
muscles contract, the anatomizes is compresses, hence the area is ishemic. Only when the
arm is passively supported and rotator cuff muscles are not contracted is the area
hypermic. The change from ischemic to hyperemic, depends
upon the nondependent rest or
passive support of dependent arm or active contraction during motion. Traction upon the
cuff from the dependent arm or from pull of the contraction cuff muscle elongates
the
tendon and renders the critical zone relatively ischemic.
TENDINITES TRAUMA, ATTRITION AND DEGENERATION:
The erect too-legged stance eliminates the weight bearing function
of upper limbs, but the need to place the hands in so many regions and positions demands
excessive range of motion of the shoulder, arm. forearm and wrists. Stability of the
shoulder girdle ahs been sacrificed for this mobility.
In a passive stage with the arm totally dependent, the
effect of gravity imposes its stress upon the supraspinatus tendon. The supraspinatus
muscles maintains its adequate tone through spindle activity, which must be constant
fatigue may well play a role here in ultimate degeneration, impairment and pain.
The mechanical effect of muscular contraction is medicated
through the tendon of the muscular
in its attachment to the corresponding bones. Traction
on the tendon causes a relative ischemia by mechanical compression
of the intrinsic blood
vessels during contraction. This tension is compounded by the direct pull of the muscle on
the tendon and the tethering impounded by its angulations within the area that becomes compressed within
the supraspinatus tendon is termed the critical zone.
This nutritional deprivation and mechanical stress cause
degeneration with formation of debris-containing calcium and breakdown of
fibrils-teninitis. Microyuptures of the fibrils result in debris and
inflammination. As
further degeneration
occurs, the tendon strands brae
free and get ground down,
resembling necrotic debris. Some calcium is deposited as microscopic crystal, causing
inflammatory reaction.
Repetitive
arm elevation at the shoulder at the shoulder joint (as in
bowlers, base ball pitchers) causes repeated tension within the tendon.
Circulation within a tendon is inversely proportional to the tension and actually
decreases with increased tension. Laboratory studies on humans and rabbits have revealed
that inflammation of the tendon can result from repetitive
contractions. This is due to
oedema and deposition of fibrin.
The kinetic aspect of the arm during abduction and overhead elevation is
probably more traumatic. When the arm is usually elevated, abducted, or held in the
overhead position for many hours a day, there is compression stress during these hours as
the greater tuberosity posses by, under
and behind the overhanging acromion and the
coracoacromial ligament.
Mechanical trauma causes release of chemical substances
which increase the damage, induce
pain and dysfunction.
Tendon tearing may be partial/total. As the pathology progress calcium
deposits in the debris leading to calcific tendimitis. This will present as a chronic
aching in shoulder agevated by abduction or external
rotation with or without overhead
elevation.
STAGES OF BOWLING AND
INJURIES
The bowling motion has been divided into 5 stages.
Stage- 1 Windup or Preparatory Phase
Stage- 2 Early Cocking
Stage-3 Late Cocking
Stage- 4 acceleration} Follow
through stages
Stage- 5 Decoration}
Preparatory phase beings with the run up. In stage-2 ball is in the bowling arm which goes
into abduction posterior flexion and external rotation. The weight of the body is on the
rear leg and the trunk is rotated away from the batter. During this phase there is early
deltoid contraction ahead of supraspinatus muscle weakness, the deltoid becomes even more
overwhelming and further degeneration results.
In stage three the entire body is shifted to the front foot, the trunk beings
denotation,
and the arm is now in maximum external rotation and posterior flexion. With these motions
there is great exposure of the rotator cuff tendon as it passes under the overhanging
acromion and coracoacromial ligament. In the bowling stages the deltoid become very
active in forceful abduction. This muscle by its anatomical alignment causes upward
displacement of the cuff tendon against the overhanging structures.
In the follow through stage(4,5) when the arm moves downward and across the
lower body the rotator cuff is undergoing eccentric contraction, which is most stressful to
cuff. When the
deltoid muscle acts unopposed as from a weakened or damages cuff
greater,inpingment results. Fatigue of scapulothorocic muscle also enhanced impingements.
During stage 4 the arm begins rerotation into internal rotation and
forward flexion down and across the chest. The body weight is now on the forwarded
foot, and the trunk insignificantly rerotated. The ball is released at this stage. In
stage 3 &4 with the arm is maximum external rotation andposteriorly flexed, the head
of the humerus iscontained exclusively by the anteroinferior capsule. The rotator cuff is
anatomically unable to prevent subluxation. Atthis stage anterior capsule and or glenoid
labrum can be torn. Entrapment of cuff tendon and bicyps tendon occur in abducted
posteriorly flexed position. During this phase the internal rotators exert powerful force
on humeral head by spinning mechanism.
As the arm declerates(stage-5) a powerful
stress is imposed on the posterior
structures which may be injured.
When a bowler is subjected to these forces, he presents with a painful
shoulder. Precise examination will determine which of the involved shoulder tissue is the
culprit.
Repeated efforts of this kind cause cumulative effect. Minor insults
with tissue changes may recur
without, sufficient
time for repair. The tissues, especially
tendons and capsule subjected to extreme strength
may become attenuated. Muscles can be
strengthening flexibility exercise
and avoidance of fatigue are mandatory.
DIAGNOSIS OF
IMPINGEMENT
SYNDROME
Pain
can result in any of three conditions.
1. Abnormal strain on a normal joint.
2. Normal strain on an abnormal joint or
3. Normal stress on a normal joint when the joint is unprepared or improperly executed for
the performance of that particular activity.
Abnormal stress from unreparedness or
improperly executed activity is the most common presenting condition. This implies that,
for whatever reason, the arm violates the normal rhythm, for example, abduction with
improper external rotation, faculty scapular motion in co-ordination of humeral
activities, faculty posture and improper training for a specific activity. Faulty
execution from fatigue, impatience, anger or anxiety can become trauma producing events.
Pain is the initial symptom and varies in intensity and
site. Intensity depends on the significance of the resultant inflammation or tissue damage
to the tendon of greater diagnostic
significance is the reproduction for aggravation
of
pain from specific motions. Patient abducted and internally rotated position. This
position reduced the tension (gravity) on the supraspinatus tendon, as does the internally
abducted position. Abduction is avoided either actively or passively because this
further entraps
the supraspinatus tendon against the over hanging acromium and coracoacromial
ligament. In the patient with a rotator cuff injury the attempt at abduction and overhead
elevation occur as a shrugging mechanism.
SHRUGGING MECHANISM
In attemptind abduction of the arm
the patient exhibits classical shrugging mechanism. This is significantly diagnostis as to
merit emphasis. Normally the humerus ebducts and rotates externally with concomitant
synchronous scapular rotation and elevation. When the glenohumeral motion is limited or
prohibited due to supraspinatus tendon engorgement, any motion attempting abduction
and arm elevation occur at the scapula. The scapula thus elevates
and rotates, whereas thee
humerus does not abduct or rotate externally. This shrugging
is an active motion requested
of the patient. If the arm can be passively elevated abducted) past the point of the
entrepment(by the examiner) further abduction elevation may be possible. Pain recurs upon
active descent of the arm toward the side position. This pain occurring
at a specific point
of abduction and again at the same point of descent is know as painful
arc.
X-Ray examination will not show any
change unless calcific deposits are present. Arthroscopy will reveal the pathology. Through
the "key hole" diagnosis can be established and cause treated; magnetic
resonance imaging(MRI) will be diagnostic.
TREATMENT
During acute
phase rest to
the part is desirable, local icepacks applied for 20 minutes period three to five times
daily is valuable. Ice is analgesic it decreases further inflammatory chemical
and
vascular changes, and it minimizes
protective spasm. Heat initially may be soothing but it
also change further engorgrmnet of these confined tissues. after 48 hours heat enhances
healing process, removes debris, and chemical toxins, and bring a new casecular supply to
the injured part.
A sling to elevate the arm with the elbow flexed and to
position the arm in internal rotation may be of considerable comfort, but a sling and thus
immobilization must never be prolonged. It may be used for 48-72 hours with gradual
removal with passive and acute physiotherapy. To prevent adhesive reaction, passive
rather than active motion must be initiated early.
The codman exercise
is essentially a pendular exercise. The person bends
forward at the waist with affected arm dangling vertically. This places the arm at 90
forward flexion without any delboid or rotaor cuff muscles contraction. Gravity on the
dependent arm causes slight separation
of the glenohumeral surfaces the body must be moved
forward backward and in a circumducting manner with the arm passively moving. The arm is a
passive pendulum, being moved in all directions of genohumeral motation with activity
shoulder muscles.
Active pendular exercise
in avoided initially. This is utilised later to regain muscles strengthened.
|This exercise
encourages active contraction of all shoulder muscles, defeating the
concept of passive, pendular exercise. At a later stage of rehabilitation
this active pendular excercise is effective and desirable but only after
pain has significantly subsided and motion is possible with less
discomfort. |
 |
