Acromioclavicular Joint Separations S43.109A 831.04

AC joint separation picture

Type I acromioclavicular separation

Type II AC joint separation

Type III AC separation

Type IV AC separation

Type V AC separation

Type VI AC separation































ICD-9 Classification / Treatment
Etiology / Natural History Associated Injuries / Differential Diagnosis
Anatomy Complications
Clinical Evaluation Follow-up Care
Xray / Diagnositc Tests Review Reference


AC Separation ICD-10

AC Separation ICD-9

  • 831.04 (Dislocation of shoulder, closed, acromioclavicular joint)
  • 831.14 (Dislocation of shoulder, open, acromioclavicular joint)

AC Separation Etiology / Epidemiology / Natural History

  • 9% of shoulder girdle injuries
  • Generally occurs in males age 20-30.
  • Relatively common in young male athletes. Generally from contact sports: rugby, wrestling, hockey. (Pallis M, Am J Sports Med. 2012;40(9):2072)

AC Separation Anatomy

  • Diathrodial joint with a fibrocartilaginous disk.  The disk has a great variation in size and shape and eventually undergoes rapid degeneration until it is essentially non-functional by the fourth decade. (DePalma AF,  CORR 1959;13:222).
  • AC joint capsule is a robust structure that contributes to AC stability especially A/P stability (Dawson P, JSES 2009;18:237). The capsule is reinforced by the acromioclavicular and coracoclavicular ligaments. 
  • AC ligaments stabilize the joint in the anteroposterior direction. (Urist MR, JBJS 1946;28:813), (Blazar PR, CORR 1998;348:114)
  • The superior AC ligament is the stongest of the AC ligaments.  Its fibers blend with the fibers of the deltoid and trapezius muscles. 
  • The posterior and superior AC ligaments should be preserved during distal clavicle resection to prevent posterior instability. (Klimkiewicz JJ, JSES 1999;8:119)
  • Coracoclavicular ligament is made up of the trapezoid and conoid ligament. It is the prime suspensory ligament of the upper extremity. (Fukuda K, JBJS 1986;68A:434)  
  • Trapezoid ligament in men has a mean length of 1.61 +/- 0.52 and a width of 1.58 +/-0.69 cm. (Urist MR, JBJS 1946;28:813)  Orgin = coracoid process, anterior and lateral to the attachment of the conoid ligament. Insertion = a rough line on the undersurface of the clavicle extending anteriorly and laterally from the conoid tubercle. 
  • Conoid ligament in men has a mean length of 1.225 +/- 0.658 cm and width of 0.737 +/-0.148 cm. (Urist MR, JBJS 1946;28:813)  Origin = the posteromedial side of the base of the coracoid process. Insertion = conoid tubercle on the posterior undersurface of the clavicle.  The conoid tubercle is located at the apex of the posterior clavicular curve, which is at the junction of the lateral third of the flattened clavicle with the medial two thirds of the triangular-shaped shaft.  
  • Based on available anatomic studies obvious oversimplifications can be made:  the AC ligaments control anteroposterior stability, the CC ligaments control superoinferior stability.

    (Lee KW, AJSM 1997;25:858), (Lizaur A, JBJS 1994;76B:602)

  • The deltoid and trapezius are also important in supplying dynamic stability to the AC joint.11
  • average space between coracoid and clavicle is 1.1 to 1.3cm
  • (Rioss CG, AJSM 2007;35:811)
  • AC joint innervation: lateral pectoral and suprascapular nerves.
  • See also Shoulder anatomy.

AC Separation Clinical Evaluation

  • Generally fall onto the adducted shoulder.
  • Pain over the AC joint.
  • Prominent distal clavicle. Inferior scapular displacement

AC Separation Xray / Diagnositc Tests

  • A/P and Lateral view in the plane of the scapula, and axillary view.
  • Zanca View
  • Consider stess views with patient holding 5-10lb weights or comparison veiws of the uninjured side. Determine coracoid-clavicular distance for comparison.

AC Separation Classification / Treatment

  • Acromioclavicular Joint Separation Classification
  • Allman31 and Tossy et al32 classified AC joint injuries into a 3 part system which was later expanded into the current 6 part system of Rockwood.27
  • Type I: strain of acromioclavicular ligaments, ligaments intact, AC joint stable, tenderness/swelling isolated to AC joint, no palpable displacement of joint, minimal pain with arm ROM. No xray changes. RX: sling/ice/nsaids prn; activity modifications until painfree, symptoms usually subside in 7-10 days.
  • Type II: acromioclavicular ligaments disrupted, A/P stability disrupted, superoinferior stability maintained by coracoclavicular ligaments; deltoid/trapezious insertions may be injured slightly. Pain/swelling in AC joint; clavicle may be elevated; arm motion causes pain; tenderness in coracoclavicular interspace. Xray-lateral clavicle may be elevated, AC joint widened, coracoclavicular interspace maintained. RX: sling 7-10 days or until symptoms subside; early gradual rehab; heavy lifting/contact sports avoided 8-12 wks
  • Type III: acromioclavicular and coracoclavicular ligaments disrupted, deltoid and trapezius insertions disrupted. Pain in AC joint and shoulder; clavicle likely visibly elevated, may tent skin; pain with any shoulder ROM; tenderness in coracoclavicular interspace. Lateral clavicle unstable in horizontal and vertical planes RX:controversial.  Non-operative management is generally recommended.  Surgery may be considered for young, athletic individuals, heavy laborers, and those who do overhead work with type III injuries. RX: AC joint reconstruction.
  • Type IV: rare; clavicle posteriorly displaced into  or through the trapezius; acromioclavicular and coracoclavicular ligaments disrupted, deltoid and trapezius insertions disrupted. Lateral clavicle palpable posteriorly, may tent skin, usually very painful, pain with any ROM. RX: AC joint reconstruction.
  • Type V: acromioclavicular and coracoclavicular ligaments disrupted, deltoid and trapezius insertions disrupted with >100% elevation of the distal clavicle. RX: AC joint reconstruction.
  • Type VI: acromioclavicular and coracoclavicular ligaments disrupted with inferior dislocation of the distal clavicle inferior to the coracoid process and posterior to the biceps and coracobrachialis tendons. RX: AC joint reconstruction.

AC Separation Associated Injuries / Differential Diagnosis

AC Separation Complications

  • Infection
  • Recurrenct AC instability
  • Shoulder Pain
  • Shoulder stiffness
  • Clavicle fracture
  • Coracoid process fracture
  • Hardware failure
  • Incisional scar (cosmesis)
  • CRPS
  • Numbness surrounding the incision
  • Risk of anesthesia including heart attack, stroke and death
  • DVT/PE

AC Separation Follow-up Care

  • The average time lost to sport due to AC joint injury = 18 days, with low-grade injuries averaging 10 days. High-grade injuries average 64 days lost to sport, with 71% electing surgical repair/reconstruction.  (Pallis M, Am J Sports Med. 2012;40(9):2072)
  • Post-op: sling, no overhead motion. Immediate pendelum ROM exercises.
  • 10-14 Days: Wound check, sutures removed. Gentle ROM home exercise program. No resistive exercises/activities. Continue sling.
  • 6 Weeks: Xrays, ensure reduction is maintained. Begin PT. No athletics.
  • 3 Months: Repeat xrays. If pt is painfree and reduction maintainted begin strengthening in PT. Progress to sport specific training.
  • 6 Months: return to sport.

AC Separation Review References