STERNOCLAVICULAR ANATOMY
- The medial physis of the clavicle is the last to form
and the last to stop growing. The medial physis of the
clavicle does not close until around 24 years of age. - Many injuries seen in young patients are actually phy-
seal injuries rather than true dislocations. - The sternoclavicular joint is a saddle joint that articu-
lates with the clavicular notch of the sternum
(Rockwood and Young, 1990). Less than half of the
medial clavicle actually articulates with the sternum. - The sternoclavicular joint capsule and the intra-articular
disk, in addition to the very strong costoclavicular and
interclavicular ligaments, stabilize the sternoclavicular
joint. The two parts of the costoclavicular ligament
cross in a V-type fashion and provide stability during
rotation and elevation.
STERNOCLAVICULAR JOINT
FUNCTION
- The sternoclavicular joint acts as the stabilizing base
of the clavicle and, therefore, the upper extremity. - Studies have shown that there is quite a bit of motion
at the sternoclavicular(SC) joint, especially com-
pared to the acromioclavicular(AC) joint. In a study
by Rockwood, he found that there approximately 40°
of rotation between the clavicle and the sternum as
compared to 6°of rotation between the clavicle and
the acromion (Rowe, 1968).
STERNOCLAVICULAR PATHOLOGIC
CONDITIONS
- The three primary pathologic conditions of the SC
joint are dislocations, instabilities, and degenerative
arthritis. The SC joint can also become septic. - It takes a considerable amount of force, applied either
directly or indirectly to the shoulder and clavicle to
disrupt the SC joint. - The most common mechanism of injury to the SC
joint is indirect force, typically an axial load from
falling directly on the lateral aspect of the shoulder.
The direction of the force and the position of the
shoulder, either flexed or extended, determine if the
dislocation is anterior or posterior. - The SC joint is often disrupted by a direct force to the
clavicle, which results in a posterior dislocation of the
joint. This is seen in motor vehicle accidents where
the patient is driven forward against a shoulder har-
ness or a direct blow from the steering wheel against
the clavicle.- SC joint dislocations are typically the result of a
single traumatic event. Instability can result either
from a single event or from repeated microtrauma,
much like the glenohumeral joint. Instabilities are
often seen in individuals with ligamentous laxity and
can be seen in skeletally immature individuals.
•Degenerative arthritis can be seen in patients who had
previously experienced a traumatic injury to the
shoulder with one notable exception: postmenopausal
women can develop spontaneous arthritis of the stern-
oclavicular joint, particularly on the right side. This is
often seen in the 6th and 7th decade.
- SC joint dislocations are typically the result of a
STERNOCLAVICULAR JOINT
PATHOLOGY DIAGNOSIS- Since it usually takes a significant force to injure the
SC joint, the mechanism of injury is usually trau-
matic, but often missed. This is due to the soft tissue
swelling over the region and the fact that patients
often have other life-threatening injuries. SC injuries
should be suspected in any high-energy injury such as
a high impact motor vehicle accident. They can also
be seen after a hard fall on to the lateral aspect of the
shoulder such as that seen with a football tackle. - Anterior dislocations are typically associated with
significant pain and swelling at the SC joint. Almost
any arm motion will exacerbate the discomfort. There
is a firm palpable mass from the prominence of the
medial clavicle. - Posterior dislocations can often be mistaken clinically
for an anterior dislocation because of the soft tissue
swelling in the region. Patients may also complain of
difficulty swallowing and breathing and shortness of
breath. Occasionally, there may also be venous dis-
tention of the affected arm due to compression of the
underlying vessels. - Plain radiographs, including anteroposteior(AP) and
lateral views of the chest, may be of limited useful-
ness in the acute setting. The most helpful plain radi-
ograph of the SC joint is the serendipity view
described by Rockwood, which is a 40–45°cephalic
tilt AP of the chest centered on the SC joint
(Rockwood and Young, 1990). An anterior dislocation
will appear to be higher on the affected side; whereas,
a posterior dislocation will appear lower. Computed
tomography(CT) scan is the ideal imaging technique
in both acute and chronic conditions. Magnetic reso-
nance imaging(MRI) can be useful in evaluation of
the soft tissues. More specialized tests, such as a CT
arteriogram, are dictated by the situation, e.g., to rule
out compression of the great vessels in a chronic pos-
terior dislocation.
274 SECTION 4 • MUSCULOSKELETAL PROBLEMS IN THE ATHLETE