The document provides a detailed overview of clavicle anatomy, including its structure, ossification, and the associated joints and ligaments. It outlines the functional importance of the clavicle in arm movement and the stability of the sternoclavicular and acromioclavicular joints. Additionally, the document discusses the neurovascular anatomy related to the clavicle and the implications for surgical approaches.

1. ORTHOFIXAR.COM

2. • Clavicle anatomy consists of medial end,
middle and lateral end. There are many
ligaments and muscles connecting to these
parts of clavicle.
• Clavicle bone is the First bone in the body to
ossify (at 5 weeks’ gestation) and last to fuse
(medial epiphysis at 25 years of age).

3. Clavicle Bone
Anatomy
• Serving as a strut between the sternum and scapula,
the clavicle bone elevates and rotates to maintain
the alignment of the scapula, allowing for additional
motion when the arm is raised and preventing
excessive anterior displacement of the scapula.
• The proximal two-thirds of the clavicle bone is
characterized by an anteriorly convex bend. The
distal one-third begins to flatten while curving
concavely to meet with the scapula. The point at
which the clavicle begins to transition from a convex
to a concave bend, approximately two-thirds of the
way along its shaft, is relatively weak and is a
common site for fractures.

4. Clavicle Bone
Anatomy
• Thin and triangular, the scapula’s anterior costal
surface is concave, forming the subscapular fossa.
The vertebral (medial) border is marked by the
inferior and superior angles. The posterior surface is
distinguished by the horizontal scapular spine, which
divides the scapula into the large infraspinous fossa
below and the smaller supraspinous fossa above.
• On the lateral end of the scapular spine is the
anteriorly projecting acromion process, which
articulates with the clavicle. Projecting inferiorly and
anteriorly to the acromion is the beak-shaped
coracoid process. The infraspinous, supraspinous,
and subscapular fossae merge on the axial border to
form the glenoid fossa. Located below the acromion,
this fossa articulates with the humeral head.

5. Clavicle Ligament
• Medial Clavicle articulates with sternal bone forming the
sternoclavicular joint, there is relatively little motion at the
sternoclavicular joint. Medially the clavicle is secured to the
sternum by the sternoclavicular capsule. The thickening of the
posterior capsule has been determined to be the single most
important soft tissue constraint to anterior or posterior
translation of the medial clavicle.
• There is also an interclavicular ligament which runs from the
medial end of one clavicle, gains purchase from the superior
aspect of the sternum at the sternal notch and attaches to the
medial end of the contralateral clavicle. Acting as a tension
wire at the base of the clavicle, this ligament helps prevent
inferior angulation or translation of the clavicle.
• There are extremely stout ligaments that originate on the first
rib and insert on the undersurface or the inferior aspect of the
clavicle.

6. Clavicle Ligament
• Laterally the clavicle articulates with the acromion bone.
• The coracoclavicular ligaments are stout ligaments that arise from
the base of the coracoid:
1. The trapezoid (more lateral): inserts onto the small osseous ridge of
the inferior clavicle.
2. Conoid (more medial): inserts onto the clavicular conoid tubercle.
• These ligaments are very strong and provide the primary resistance
to superior displacement of the clavicle. Their integrity, or lack
thereof, plays an important role in the decision making and fixation
selection in the treatment of displaced lateral third clavicle fractures.
• Clavicle fractures in this location will often have an avulsed inferior
fragment to which these ligaments are attached, especially in
younger individuals.
• The capsule of the AC joint is thickened superiorly and is primarily
responsible for resisting AP displacement of the joint.
• If one is inserting a hook plate for fixation of a very distal fracture, a
small defect can be made in the posterolateral aspect.

7. Muscle Attachments
• Medially: the pectoralis major muscle originates from the
clavicular shaft anteroinferiorly, and the sternocleidomastoid
originates superiorly.
• Laterally: the pectoralis origin merges with the origin of the
anterior deltoid, while the trapezius insertion blends superiorly
with the deltoid origin at the lateral margin.
• The medial clavicular fragment is elevated by the unopposed pull
of the sternocleidomastoid muscle, while the distal fragment is
held inferiorly by the deltoid and medially by the pectoralis
major.
• The platysma or “shaving muscle” is variable in terms of
thickness and extent, but usually envelopes the anterior and
superior aspects of the clavicle and runs in the subcutaneous
tissues, extending superiorly to the mandible and the deeper
facial muscles. It is divided during the surgical approach, and is
typically included in the closure of the superficial, or
skin/subcutaneous layer.

8. Neurovascular Anatomy
• The supraclavicular nerves originate from cervical roots
C3 and C4 and exit from a common trunk behind the
posterior border of the sternocleidomastoid muscle.
• There are typically three major branches (anterior,
middle, and posterior) that cross the clavicle superficially
from medial to lateral and are risk during surgical
approaches. If they are divided, an area of numbness is
typically felt inferior to the surgical incision, although
this tends to improve with time.

9. Neurovascular Anatomy
• The subclavian vein runs directly below the subclavius
muscle and above the first rib, where it is readily accessible
(for central venous access) and vulnerable (to inadvertent
injury).
• More posteriorly lie the subclavian artery and the brachial
plexus, separated from the vein and clavicle by the
additional layer of the scalenus anterior muscle medially.
subclavian vessels were closest at the medial end, with the
vein directly apposed to the posterior cortex of the medial
clavicle in some cases.
• In the middle third, the artery and vein were a mean of 17
and 13 mm from the clavicle, respectively, at an
approximate angle of 60 degrees to the horizontal (i.e., the
vessels were posterior-inferior to the clavicle).
• Laterally, the distances were greater, with the artery and
vein a mean of 63 and 76 mm, respectively form the clavicle.

10. Sternoclavicular joint
• The manubrium of the sternum serves as the site of
attachment for each clavicle. Projecting above the body
of the sternum, the superior surface of the manubrium
is indented by the jugular (suprasternal) notch.
Projecting off each side of the jugular notch is the
clavicular notch, which accepts the medial head of the
clavicle
• At the Sternoclavicular joint, the proximal portion of the
clavicle meets the manubrium of the sternum and a
portion of the first costal cartilage to form a gliding joint
that allows three degrees of freedom of motion:
• Elevation and depression,
• Protraction and retraction,
• Anterior and posterior rotation.

11. Sternoclavicular joint
• Although the overall stability of the joint is enhanced by the
presence of a fibrocartilaginous disc, the SC joint has the
poorest bony stability of any of the major joints. Its strong
ligamentous structure and protected location, however,
makes it one of the least frequently dislocated joints.
Surrounded by a synovial membrane, the SC joint is
supported by the anterior and posterior SC ligaments, the
costoclavicular ligament, and the interclavicular ligament.
• The sternoclavicular disc, which has qualities similar to the
menisci found in the knee, functions as a shock absorber.
The upper portion of the disc is attached to the clavicle, and
its lower portion is attached to the manubrium and first
costal cartilage. This disc divides the joint into two articular
cavities, one between the disc and the clavicle and a second
between the disc and the manubrium.

12. Sternoclavicular joint
• Although the overall stability of the joint is enhanced by the
presence of a fibrocartilaginous disc, the SC joint has the
poorest bony stability of any of the major joints. Its strong
ligamentous structure and protected location, however,
makes it one of the least frequently dislocated joints.
Surrounded by a synovial membrane, the SC joint is
supported by the anterior and posterior SC ligaments, the
costoclavicular ligament, and the interclavicular ligament.
• The sternoclavicular disc, which has qualities similar to the
menisci found in the knee, functions as a shock absorber.
The upper portion of the disc is attached to the clavicle, and
its lower portion is attached to the manubrium and first
costal cartilage. This disc divides the joint into two articular
cavities, one between the disc and the clavicle and a second
between the disc and the manubrium.

13. Acromioclavicular joint
• The distal end of the clavicle meets the acromion
process of the scapula to form the Acromioclavicular
joint. A plane synovial joint, the AC joint allows a gliding
articulation between the acromion and the clavicle,
capable of 3 degrees of freedom of movement, each
around an oblique axis:
• Internal and external rotation around a vertical axis,
• Upward and downward rotation around an axis
perpendicular to the plane of the scapula,
• Anterior and posterior scapular tilting around a horizontal
axis.
• This articulation allows for the motion necessary to
maintain the relationship between the scapula and the
clavicle in the early and late stages of the GH joint’s ROM

14. Acromioclavicular joint
• Surrounded by a synovial membrane, the AC joint is
supported by the AC ligament and the coracoclavicular
ligament, which suspend the scapula from the clavicle.
• A synovial disc is present between the clavicle and the
acromion that disappears by the fourth decade of life.
• Divided into two separate bands, the superior and
inferior portions of the AC ligament function to maintain
continuity between the articulating surfaces of the
acromion and clavicle.
• With much of its restraint in the horizontal plane, this
ligament maintains stability by preventing the clavicle
from riding up and over the acromion process.

15. Acromioclavicular joint
• Most of the AC joint’s intrinsic stability arises from the
coracoclavicular ligament, a structure extrinsic to the joint.
Because of its direct connection to the scapula, the
coracoclavicular ligament influences scapulohumeral motion.
• This ligament is divided into two distinct portions:
1. The lateral quadrilateral-shaped trapezoid ligament.
2. The medial triangular-shaped conoid ligament.
• Separated by a bursa, the trapezoid ligament limits lateral
movement of the clavicle over the acromion. The conoid
ligament restricts superior movement of the clavicle. Acting
jointly, these ligaments limit rotation of the scapula and
provide some degree of horizontal stability.
• The conoid portion of the ligament is critical for the passive
posterior rotation of the clavicle that occurs during shoulder
elevation. A horizontal dislocation of the AC joint can occur
with the coracoclavicular ligament remaining intact.

16. References:
1. Orthofixar | Orthopedic Surgery Learning
2.Millers Review of Orthopaedics -7th Edition Book.
3.Rockwood and Green's Fractures in Adults 8th Edition book.
4.Hyland S, Charlick M, Varacallo M. Anatomy, Shoulder and Upper
Limb, Clavicle. [Updated 2021 Jul 26]. In: StatPearls [Internet].
Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from:
NBK525990.