eMedicine Specialties > Emergency Medicine > Trauma & Orthopedics
Acromioclavicular Injury
Updated: Apr 1, 2008
Introduction
Background
Acromioclavicular (AC) joint injuries most commonly occur in active or athletic young adults. Although uncommon, pediatric AC injuries are increasing because of the rising popularity of dangerous summer and winter sporting activities.
For a related CME/CE activity, see CME/CE - Management of Chronic Shoulder Disorders Reviewed.
Pathophysiology
The AC joint is composed of the articular surfaces of the clavicle and the acromion, a surrounding capsule, and 2 sets of ligaments (AC and coracoclavicular [CC] ligaments). The AC ligament is composed of stronger superior and inferior ligaments as well as weaker anterior and posterior ligaments. The AC ligament is the principle restraint to anteroposterior translation between the clavicle and the acromion. The CC ligament is composed of the conoid and trapezoid ligaments, which together form a strong, heavy band that provides vertical stability. The AC joint has minimal mobility.
Classification of injury
The degree of clavicular displacement depends on the severity of injury to the AC and CC ligaments, the AC joint capsule, and the supporting muscles of the shoulder (trapezius and deltoid) that attach to the clavicle.
Allman and Tossy initially proposed a 3-grade classification that Rockwood expanded to 6 types of injury. Grades I and II are the same in both classification schemes with grade III injuries in the Tossy classification subdivided into grades III, IV, V, and VI in the Rockwood classification.
The Rockwood classification is as follows:
- Type I - Minor sprain of AC ligament, intact joint capsule, intact CC ligament, intact deltoid and trapezius
- Type II - Rupture of AC ligament and joint capsule, sprain of CC ligament but CC interspace intact, minimal detachment of deltoid and trapezius
- Type III - Rupture of AC ligament, joint capsule, and CC ligament; clavicle elevated (as much as 100% displacement); detachment of deltoid and trapezius
- Type IV - Rupture of AC ligament, joint capsule, and CC ligament; clavicle displaced posteriorly into the trapezius; detachment of deltoid and trapezius
- Type V - Rupture of AC ligament, joint capsule, and CC ligament; clavicle elevated (more than 100% displacement); detachment of deltoid and trapezius
- Type VI (rare) - Rupture of AC ligament, joint capsule, and CC ligament; clavicle displaced behind the tendons of the biceps and coracobrachialis
Pediatric AC injury
AC joint injuries in children are uncommon, and they differ anatomically from such injuries in adults. The immature clavicle is encased in a periosteal tube. The CC ligament is within this tissue, while the AC ligament is exterior to it. This anatomic relationship explains why the AC ligament is frequently injured with direct trauma, while the CC ligament remains intact. When evaluating a pediatric radiography, remember that incomplete closure of or failure of an ossification center may appear to be a fracture.
The pediatric Rockwood classification is as follows:
- Type I - Clavicle stable; joint radiographically normal
- Type II - Partial tear of the periosteal tube, allowing for some mobility of the distal clavicle; AC ligament disrupted
- Types III-VI - Larger tear through the periosteal tube, allowing for greater clavicle mobility and gross instability with clavicle positioning; CC ligament remains attached to the clavicle periosteal tube
Frequency
United States
The true incidence of AC injury is not known, as many affected do not seek treatment. Approximately 12% of all dislocations involving the shoulder affect the AC joint.
Mortality/Morbidity
Mortality is not commonly associated with AC injuries. Significant morbidity is negligible with type I and II injuries. Types IV, V, and VI do well with surgical repair. Morbidity is highest with type III injuries due to the controversy surrounding management.
Race
No difference in injury patterns exists among various racial or ethnic backgrounds.
Sex
Males sustain significantly more AC injuries due to larger participation in high-risk activities.
Age
Younger patients (<35 y) sustain more AC injuries due to higher participation in risky activities.
Clinical
History
AC injury often involves a fall onto the apex of the shoulder, usually with the arm in adduction. Severe forces resulting from significant falls are often associated with type III-VI injuries. Patients usually present with pain at the top of the shoulder at the acromioclavicular joint and can often be seen carrying the affected arm close to the side of their bodies. Alternatively, patients use the unaffected arm to splint the injured extremity. Abrasions and ecchymoses are common at the site of impact.
Physical
While examining the stability of the affected shoulder, the midshaft of the clavicle should be manipulated rather than the AC joint itself. The patient should be asked to place the hand of the affected side on the opposite shoulder while the examiner applies downward force on the affected elbow, trying to elicit pain at the AC joint. Patients may also experience pain upon direct palpation of the AC joint. Several techniques to directly assess the AC joint are discussed in the orthopaedic literature, although none of these maneuvers has been shown to have a high sensitivity or specificity.
Palpating the bony structures of the shoulder for any stepoff that might suggest occult fracture as well as noting any displacement of the clavicle are important. A thorough neurovascular examination to rule out brachial plexus injury is also essential, although concomitant neurovascular injury is relatively rare in AC joint injuries.
Causes
Downward blunt force on the acromion results in variable injury to the AC and CC ligaments. Other injuries, depending on the force of injury, may include tears of the deltoid and trapezius attachments at the clavicle and fractures of the acromion, clavicle, and coracoid (or of their cartilaginous attachments).
Athletes participating in contact sports, such as football and martial arts, are at increased risk of AC joint injuries. Patients involved in motor vehicle collisions with direct trauma to the apex of the shoulder are also at risk for AC injuries.
More on Acromioclavicular Injury |
 Overview: Acromioclavicular Injury |
| Differential Diagnoses & Workup: Acromioclavicular Injury |
| Treatment & Medication: Acromioclavicular Injury |
| Follow-up: Acromioclavicular Injury |
| Multimedia: Acromioclavicular Injury |
| References |
| Next Page » |
References
Heers G, Hedtmann A. Correlation of ultrasonographic findings to Tossy's and Rockwood's classification of acromioclavicular joint injuries. Ultrasound Med Biol. Jun 2005;31(6):725-32. [Medline].
Nissen CW, Chatterjee A. Type III acromioclavicular separation: results of a recent survey on its management. Am J Orthop. Feb 2007;36(2):89-93. [Medline].
Phillips AM, Smart C, Groom AF. Acromioclavicular dislocation. Conservative or surgical therapy. Clin Orthop Relat Res. Aug 1998;10-7. [Medline].
Basamania CJ, Higgins LD, Witkowski EG. Medial instability of the shoulder: A new concept of the pathomechanics of acromioclavicular separations. Program and Abstracts of the American Shoulder and Elbow Surgeons 18th Annual Meeting. 2001;Abstract 49.
Bradley JP, Elkousy H. Decision making: operative versus nonoperative treatment of acromioclavicular joint injuries. Clin Sports Med. Apr 2003;22(2):277-90. [Medline].
Clarke HD, McCann PD. Acromioclavicular joint injuries. Orthop Clin North Am. Apr 2000;31(2):177-87. [Medline].
Codsi MJ. The painful shoulder: when to inject and when to refer. Cleve Clin J Med. Jul 2007;74(7):473-4, 477-8, 480-2 passim. [Medline].
Crenshaw AH, Daugherty K, Campbell WC. Campbell's Operative Orthopaedics. 8th ed. Mosby-Year Book; 1992:1358.
Donovan PJ. Shoulder injuries. In: Hart RG, Rittenberry TJ, Uehara DT, eds. Handbook of Orthopaedic Emergencies. Lippincott Williams & Wilkins Publishers; 1999:166-168.
Dumonski M, Mazzocca AD, Rios C, et al. Evaluation and management of acromioclavicular joint injuries. Am J Orthop. Oct 2004;33(10):526-32. [Medline].
Gordon BH, Chew FS. Isolated acromioclavicular joint pathology in the symptomatic shoulder on magnetic resonance imaging: a pictorial essay. J Comput Assist Tomogr. Mar-Apr 2004;28(2):215-22. [Medline].
Kaplan LD, Flanigan DC, Norwig J, et al. Prevalence and variance of shoulder injuries in elite collegiate football players. Am J Sports Med. Aug 2005;33(8):1142-6. [Medline].
McMahon P, Skinner H. Acromioclavicular injury. In: Current Diagnosis and Treatment in Orthopedics [online]. 3rd ed. 2005.
Montellese P, Dancy T. The acromioclavicular joint. Prim Care. Dec 2004;31(4):857-66. [Medline].
Mouhsine E, Garofalo R, Crevoisier X, Farron A. Grade I and II acromioclavicular dislocations: results of conservative treatment. J Shoulder Elbow Surg. Nov-Dec 2003;12(6):599-602. [Medline].
Peetrons P, Bédard JP. Acromioclavicular joint injury: enhanced technique of examination with dynamic maneuver. J Clin Ultrasound. Jun 2007;35(5):262-7. [Medline].
Petron DJ, Hanson RW Jr. Acromioclavicular joint disorders. Curr Sports Med Rep. Oct 2007;6(5):300-6. [Medline].
Rockwood CA, Green DP. Fractures in Adults. Lippincott-Raven; 1984:860.
Rockwood CA, Wilkins KE, King RE. Fractures in Children. Vol 3. Lippincott Williams & Wilkins Publishers; 1984:631.
Schlegel TF, Burks RT, Marcus RL, Dunn HK. A prospective evaluation of untreated acute grade III acromioclavicular separations. Am J Sports Med. Nov-Dec 2001;29(6):699-703. [Medline].
Further Reading
Keywords
acromioclavicular injury, acromioclavicular joint separation, acromioclavicular joint, AC, ACJ, acromioclavicular joint injuries, AC joint injuries, ACJ injuries, clavicular displacement, pediatric AC joint injury, shoulder injury, shoulder dislocation, clavicle dislocation, clavicular injury
