tears of the shoulder have been a particular focus of attention since
the advent of the arthroscope, a small instrument that
allows the orthopaedic surgeon to clearly see inside the shoulder
joint and view the labrum, its environment, and any injuries that
may have occurred. The arthroscope, in conjunction with anatomic dissections,
history, physical examination, and symptoms has allowed orthopaedic
surgeons to better understand and treat a variety of injuries to the
The shoulder is the most mobile joint in the human body. It consists
of a complex arrangement of structures working together to provide
the movement necessary for daily life. Unfortunately, this great mobility
comes at the expense of stability. Four bones and a network of soft
tissue structures (ligaments, tendons, and muscles) work together
to produce shoulder movement. They interact to keep the joint in place
while it moves through extreme ranges of motion. Each of these structures
makes an important contribution to shoulder movement and stability.
Certain work or sports activities can put great demands upon the shoulder,
and injury can occur when the limits of movement are exceeded and/or
the individual structures are overloaded.
What is the labrum and what does it do?
The labrum is a disk of cartilage on the glenoid,
or "socket" side of the shoulder joint. The labrum helps stabilize
the joint and acts as a "bumper" to limit excessive motion of the
humerus, the "ball" side of the shoulder joint. More
importantly, it holds the humerus securely to the glenoid, almost
as if suction were involved. Although the glenoid itself is a relatively
flat surface, the labrum's cuff-like contour gives the glenoid a more
concave shape. The secure but flexible fit of the humerus within
the glenoid permits the great range motion of the healthy shoulder.
How is the labrum injured?
Tears of the labrum can be the result of:
A very common labral injury is a tear that occurs on the top of the
labrum, extending from the front to the back of the cartilage. This
is known as a SLAP tear ("SLAP" is an acronym for superior
labral anterior to posterior tear). This injury affects the
attachment of the biceps tendon to the glenoid. An
injury in this area can be extremely painful, and can cause the biceps
tendon to rupture.
- a direct fall or blow to the arm resulting in abnormal movement
of the humerus.
- repetitive trauma of the greater tuberosity and
rotator cuff on the posterior (back
of) labrum. This is termed internal impingement
(pinching of the soft tissues) and is most commonly seen in baseball
and tennis athletes whose arms are frequently in overhead positions.
At least five types of SLAP tears have been identified. Treatment
depends on the stability of the biceps anchor and the type of tear
that has occurred. These injuries are commonly the result of:
It is very important for the surgeon to determine whether or not the
labral tear is associated with instability of the shoulder. A tear
of the labrum not associated with instability can be treated surgically
by itself, but the treatment of a labral tear in an unstable shoulder
will only be successful if the shoulder is surgically stabilized at
the same time.
- a fall on an outstretched arm.
- a forceful lifting maneuver.
- repetitive throwing.
© 2001 by LeadingMD, Inc. All rights reserved