PATHOLOGY OF INSTABILITY
- The primary pathologic entity for traumatic instability is
disruption of the anterior inferior labrum combined with
damage to the capsule. The primary pathology for mul-
tidirectional instability is a loose, redundant capsule.
DYNAMIC RESTRAINTS
- This is a term that refers to the stability provided by
contraction of the rotator cuff (supraspinatus, infra-
spinatus, subscapularis, and teres minor) and scapular
stabilizers (serratus anterior, trapezius, and levator
scapulae). The long head of the biceps can stabilize
when contracting as well as the acromial arch (cora-
coacromial ligament and conjoined tendon)
STATIC RESTRAINTS
- These restraints comprise bony, ligamentous, and
labral anatomy that restrain translation statically and
is independent of muscle contraction. It is important
to recognize that the shoulder capsule only stabilizes
at the end ranges of motion.
1.Labrum: Labrum provides stability to the humeral
head like a chock block for a tire. Fibrocartilagenous
structure attached to both the capsule as well as the
glenoid. Surrounds the entire glenoid and is gener-
ally tightly attached in the anterior inferior quadrant,
has a variable attachment in the superior quadrant,
and is generally less prominent posteriorly.
2. Ligaments: The glenohumeral ligaments represent
thickenings of the shoulder capsule. These are
checkreins for stability. They are visualized arthro-
scopically on the inside of the shoulder but are dif-
ficult to distinguish on the outside.
3. Physical pressure adhesions/cohesions
4. Finite joint volume
5. Joint conformity
CONGENITAL FACTORS
- Individual collagen laxity
- Bone configuration (small glenoid, retroverted glenoid)
- Age
CLINICAL PRESENTATION (PHYSICAL
EXAMINATION)
- Examination:A careful and complete vascular and
neurologic examination is essential. (The frequency
of axillary nerve injuries increases with age, incidence
5–35%) (Blom and Dahlback, 1970)
A. TRAUMATIC- Anterior:This patient is in acute distress. Arm held
in slight abduction and internal rotation. There is a
loss of deltoid contour and there will be a prominence
of the acromion. (Arciero, 1999) - Posterior:Associated either with a high energy event
with a posterior directed force or a subluxation. Arm
held in significant internal rotation. An anterior
dimple can be appreciated. A hallmark physical exam-
ination feature is inability to externally rotate the arm.
B. ATRAUMATICMULTIDIRECTIONAL- These patients present with complaints of pain and
multiple subluxation events. A hallmark physical
examination feature is generalized ligamentous laxity
and a sulcus sign. They may or may not have global
joint laxity and due to pain and spasm sometimes do
not have significant glenohumeral translation. (Neer
and Foster, 1980)
RADIOGRAPHIC EXAMINATION- It is essential to obtain three views of the shoulder to
determine direction of dislocation but also to ascertain
the involvement of other bony pathology. - AP:The arm is held in slight internal rotation. This
view will assist in identification of greater tuberosity
fractures. The glenoid in profile or an AP with the
beam angled perpendicular to the glenohumeral joint
will allow more accurate identification of glenoid rim
fractures. - West point:This is a special view taken with the
patient prone and the beam directed inferiorly. It is a
view which allows visualization of the anterior gle-
noid with no other overlying bone involvement. A tra-
ditional axillary view is also very useful for evaluating
direction of dislocation and fractures of the glenoid. - Supraspinatus outlet view, scapular lateral view,
or Y view:This is a lateral view of the shoulder which
can provide information on direction of dislocation as
well as angulation of proximal humerus fractures. - Stryker notch:This is a view taken to evaluate the
humeral head. A Hill Sachs lesion is an impression
fracture of the humeral head and if large enough can
impact on clinical outcome. The patient is supine with
the shoulder and elbow flexed and the beam directed
through the axilla.
IMAGING•Various imaging technology is used to quantify the
amount of capsular labral damage as well as evaluate
the articular surface, rotator cuff, and bony architecture.264 SECTION 4 • MUSCULOSKELETAL PROBLEMS IN THE ATHLETE