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