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A N A T O M Y FOR DIAGNOSTIC I M A G I N G
and at the interphalangeal joint of the thumb in 73%. These are occasionally found at other metacarpal and distal interphalangeal joints. The incidence of sesamoid bones is increased in acromegaly. Tendons of the extensors of the fingers
Articular surfaces The sternal end of the clavicle, the clavicular notch of the manubrium and the upper surface of the first costal cartilage. Ligaments
These are inserted into the base of the dorsum of the phalanges. Avulsion fractures of this part of the phalanx are associated with proximal displacement of the fragment if the extensor tendon is attached to it, and may need internal fixation. Small fractures of the base of the distal phalanx without displacement do not need fixation.
The acromioclavicular joint
Ossification of the metacarpals and phalanges
Type
These ossify between the ninth and twelfth fetal weeks. Secondary ossification centres appear in the distal end of the metacarpals of the fingers at 2 years and fuse at 20 years of age. Secondary centres for the thumb metacarpal and for the phalanges are at their proximal end and appear between 2 and 3 years, and fuse between 18 and 20 years of age.
The acromioclavicular joint is a synovial joint.
THE JOINTS OF THE UPPER LIMB The sternoclavicular joint Type The sternoclavicular joint is a synovial joint divided into two parts by an articular disc.
These are the anterior and posterior sternoclavicular ligaments, the costoclavicular ligament and the interclavicular ligament.
Articular surfaces These are the outer end of the clavicle and the acromium. In health the undersurface of the acromion will align with the undersurface of the clavicle. Ligaments These are as follows: • Acromioclavicular ligament, which is a thickening of the fibrous capsule superiorly; and • Coracoclavicular ligament, which has conoid and trapezoid parts.
Fig. 7.9 (a) Coronal oblique section t h r o u g h the shoulder j o i n t as seen on coronal oblique MRI scan.
