- Discussion:
- proximal humerus ossifies from four centers:
head, shaft, and both
tubercles, which unite at age 19 to 20;
- frx in adult life tend to occur along old epiphyseal lines;
- depression between tubercles, bicipital groove, contains long head of
biceps;
- tubercles also serve as points of insertion for
rotator cuff,
w/
subscapularis inserting on lesser tubercle &
supraspinatus,
infraspinatus, and
teres minor inserting from anterior to posterior on
three facets of the greater tubercle;
- Proximal Epiphyseal Plate:
- irregularly cone shaped with apex pointing superiorly, posteriorly and
medially in relationship to shaft;
- configuration interlocks physis and metaphysis at the plate;
- position of apex tends to resist axial and posterior forces;
- thickened periosteum anchors head and tuberosities to shaft
- anterior periosteum is thinner and weaker
- posterior periosteum is thicker
- ensures
blood supply to head by secure fixation to physis;
- fusion of upper humeral epiphysis with the shaft takes place between
20 and 22 years of age;
