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Anatomy of Proximal Humeral Physis


- 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