Northwestern University Feinberg School of Medicine

Orthopedic Teaching

Shoulder Case 8 Diagnosis

AC Separation


Diagnosis

Standard radiographs of the shoulder should be obtained (AP, scapular Y view). The normal AC joint space is 3mm and the normal coracoclavicular distance is 13 mm. Anything larger than these are pathologic. There are six types of AC separations:

Type I:

  • AC sprain, tender over AC joint
  • X Ray: normal

Type II:

  • Torn AC ligament, stretched CC ligament
  • X Ray: slight increase AC distance

Type III:

  • Torn AC and CC ligaments
  • X Ray: clavicle elevated above the normal plane of AC joint (>5mm), increased CC distance (>13 mm)

Type IV:

  • Torn AC and CC ligaments, displaced clavicle into trapezius
  • X Ray: distal clavicle is displaced posteriorly

Type V:

  • Torn AC and CC ligaments, muscular disruption of attachments to distal clavicle
  • X Ray: elevated clavicle above acromion (up to 1-3 x width of clavicle), CC distance 3 times normal

Type VI:

  • Torn AC and CC ligmaments, complete muscular disruption
  • X Ray: complete disruption of joint (displacements beyond Type V parameters)