eMedicine Specialties > Orthopedic Surgery > Shoulder

Acromioclavicular Joint Separations

David Prybyla, MD, Staff Physician, Department of Orthopedic Surgery, University of Massachusetts Medical School
Brett D Owens, MD, Chief, Sports Medicine and Shoulder Service, William Beaumont Army Medical Center; Thomas P Goss, MD, Chief of Shoulder Surgery, Professor, Department of Orthopedic Surgery, University of Massachusetts Memorial Health Care

Updated: Sep 22, 2009

Introduction

The acromioclavicular (AC) joint is a diarthrodial articulation with an interposed fibrocartilaginous meniscal disk that links the hyaline cartilage articular surfaces of the acromial process and the clavicle. The joint is stabilized by a combination of dynamic muscular and static ligamentous structures, which allow a normal anatomic range of motion. Because of the transverse orientation of the articulation, direct downward forces may result in shear stresses that cause disruption of these stabilizing structures and create displacement beyond the normal limits. This is evidenced by abnormal positioning of the clavicle relative to the acromion, usually in the superior direction.

The severity of an AC separation is dependent upon the degree of ligamentous injury. The capsular AC ligaments and the extracapsular coracoclavicular (CC) ligament are the primary static stabilizers of the AC joint, as seen in the image below. The anterior and posterior AC ligaments are predominantly responsible for maintaining stability in the anteroposterior (AP) plane. The 2 components of the CC ligament, the trapezoid and conoid ligaments, provide restraint against compression and superior-inferior translation, respectively.^{[1 ]}The deltoid and trapezius muscles are especially important in providing dynamic stabilization when these ligamentous structures are damaged.

Acromioclavicular joint anatomy.

History of the Procedure

Treatment of acromioclavicular (AC) separations has been a subject of debate. Type I and type II injuries are generally accepted to be treated nonoperatively in the acute setting. However, reaching a consensus regarding the optimal management of acute type III injuries has been difficult.

The earliest writings on the subject were by Hippocrates, Galen, and Paul of Aegina, who recommended conservative management with compressive bandages to keep the clavicle in a normal position.^{[4 ]}However, subsequent medical history shows that nonoperative and operative treatments for acute type III AC separations have gained popularity in cyclical fashion.

Surgical management gained popularity with the advent of improved anesthesia and sterile surgical techniques. The first surgical repair of an acute AC dislocation is credited to Samuel Cooper, who used a loop of silver wire to approximate the clavicle and acromion process.^{[5 ]}Subsequently, numerous other techniques were reported, including suture repair of the AC ligaments and CC ligament,^{[5 ]}tendon graft for reconstruction,^{[5,6 ]}and fixation with nails, screws, or wires.^{[5,7,8,9,10 ]}

To understand contemporary opinion regarding nonoperative versus operative repair of acute type III AC separations, approved orthopedic residency program chairpersons have been polled twice. In 1974, Powers and Bach found that most chairpersons advocated open surgical repair of type III injuries and concluded that surgical repair was the most popular method of treatment.^{[11 ]}In 1992, Cox reported the results of a similar poll, which found that 72.2% of chairpersons who responded preferred nonoperative, symptomatic management.^{[12 ]}He concluded that this represented a shift toward conservative management of such injuries.

The management of acute type III AC separations is still somewhat controversial. In most patients with such injuries, nonoperative care achieves an excellent functional outcome. In younger, more active patients, surgical correction should at least be considered.^{[13,3,14 ]}

Problem

The degree of damage to the acromioclavicular (AC) ligaments and coracoclavicular (CC) ligament with resultant displacement of the clavicle relative to the acromion is the primary criterion for the classification of AC separations. Originally, Cadenat differentiated incomplete injuries, in which only the capsular AC ligaments were torn, from injuries that involved disruption of both the AC and CC ligamentous structures.^{[5 ]}Allman and Tossy later recognized 3 different types of AC separation based on similar criteria. Type I injuries were characterized by sprained but intact CC and AC ligaments. Type II injuries involved a complete disruption of the AC ligaments with a sprained but intact CC ligament. In the more severe type III injury, both the CC and AC structures were completely disrupted.^{[15,16 ]}

In more recent years, this system has been expanded to include 3 additional variants.^{[17 ]}Type IV injuries are defined by posterior displacement of the clavicle relative to the acromion with buttonholing through the trapezius muscle. In type V injuries, the clavicle is widely displaced superiorly relative to the acromion as a result of disruption of muscle attachments. The rare type VI injuries are characterized by inferior displacement of the distal clavicle below the acromial process or the coracoid process. See image below for classification.

Allman/Rockwood classification of acromioclavicular injuries.

Coracoid process fractures and CC ligament bony avulsions associated with AC joint separations represent variations on this theme. Recognition of these unique injury patterns helps guide treatment.

Frequency

Acromioclavicular joint injuries are seen especially in competitive athletes, such as rugby or hockey players, and occur most frequently in the second decade of life. Males are more commonly affected than females, with a male-to-female ratio of approximately 5:1.^{[13 ]}

Etiology

The most common mechanism of injury is a direct force applied to the superior aspect of the acromion, usually from a fall with the arm in an adducted position. This impact drives the acromion inferiorly, spraining the intra-articular acromioclavicular ligaments. If the force is great enough, the extra-articular coracoclavicular ligament may also be damaged.

Less commonly, an indirect force may be transmitted up the arm as a result of a fall on an outstretched hand. The force continues through the humeral head to the acromial process, displacing it superiorly and stressing the AC ligaments. The coracoacromial (CA) ligaments are not injured with this type of mechanism.

Presentation

Patients typically present with pain and restricted shoulder motion after a fall. Specifying the acuteness of the pain is important, as patients may experience similar pain and limitation of movement with chronic conditions affecting the shoulder. Age is also a helpful diagnostic clue. Incidence of acromioclavicular (AC) separations is highest in patients in the second decade of life; patients in this age group almost never present with degenerative rotator cuff tears or impingement.

Visual inspection of the patient may also provide a significant key to diagnosis. A prominent clavicle with loss of the normal contour of the shoulder caused by sagging of the acromion is highly suggestive of a ligamentous disruption of the AC joint. These findings may be clearer when the patient is asked to hold a 10- to 15-pound weight in the hand of the affected arm. Patients should undergo a standard shoulder examination, including evaluation of range of motion and assessment of neurovascular status. Pain with palpation over the AC joint and inhibited movement due to discomfort are generally noted.

Indications

Treatment for acute type III acromioclavicular (AC) injuries remains controversial despite randomized trials that indicate success with nonoperative treatment in most cases.^{[18,19,20 ]}Many surgeons believe that this degree of displacement leads to muscle-fatigue discomfort and difficulty manipulating heavy loads. As a result, operative intervention should be considered in heavy laborers and younger patients who are athletic or unsure of their future careers.

Type IV, V, and VI injuries generally require surgical repair. Because the clavicle is so far displaced from the acromial process in the posterior, superior, or inferior direction, respectively, conservative management is inadequate. The patient continues to experience pain and dysfunction if the articulation is not reduced and stabilized.

Type I, II, and III injuries that are managed conservatively may result in persistent shoulder pain, dysfunction, or both. Type I and II separations may progress to develop symptomatic degenerative disease. Type III separations may result in impingement symptoms, muscle-fatigue discomfort, and/or neurovascular symptomatology. Late surgical management may be required.

Relevant Anatomy

The acromioclavicular (AC) joint capsule is strengthened by the anterior and posterior AC ligaments. These ligaments are intracapsular and provide stability in the anterior and posterior directions. The fibers of the trapezius and the deltoid muscles provide additional stability.

The trapezoid and conoid components of the coracoclavicular (CC) ligament add vertical stability. They attach to the coracoid process and the inferior surface of the distal clavicle (see image below).^{[21 ]}

Acromioclavicular joint anatomy.

Although not an AC joint–stabilizing structure, the coracoacromial (CA) ligament is also relevant to the discussion of surgical treatment. This structure runs from the superior surface of the coracoid process to the inferior surface of the acromial process in a nearly horizontal direction. During operative repair of type III injuries, the CA ligament may be resected from its acromial insertion and used to reconstruct the torn CC ligament.

Type III, IV, V, and VI AC separations are, in fact, double disruptions of the superior shoulder suspensory complex (SSSC). The SSSC is a bony and soft-tissue ring composed of the glenoid process, the coracoid process, the CC ligament, the distal clavicle, the AC joint, and the acromial process at the end of a superior bony strut (the midshaft clavicle) and an inferior bony strut (the junction of the lateral scapular body and the medial glenoid neck). Type III through type VI separations are characterized by disruptions of both the CC and AC ligaments; therefore, they constitute unstable injuries that must be accounted for or require surgical reduction and stabilization.^{[22 ]}

Contraindications

The presence of infection is a contraindication to repair of an acromioclavicular separation. Additionally, an open wound with compromised soft tissues may necessitate delay of the surgery until the risk of infection is minimized by irrigation and antibiotic prophylaxis. Other considerations include the patient's overall health and ability to undergo anesthesia.

Workup

Imaging Studies

• Standard shoulder series radiographs: AP and axillary views of the shoulder, a lateral projection of the scapula (scapular Y), and a weight-bearing view of the shoulder (an AP projection of the shoulder obtained while the patient's affected arm is holding a 10- to 15-pound weight)
  • Standard radiographs are usually adequate to confirm the diagnosis.
  • Stress radiographs are taken to evaluate more accurately the integrity of the ligamentous structures by showing the degree of displacement of the acromion relative to the clavicle.
• Magnetic resonance imaging has been shown to be helpful in differentiating between type II and type III injuries.^{[23 ]}

Treatment

Medical Therapy

Acutely, acromioclavicular (AC) separations are generally quite painful. A brief course of narcotics followed by nonsteroidal anti-inflammatory drugs in combination with locally applied ice and activity modification is usually sufficient for type I and II injuries. For type I injuries, activity modification may include the use of a sling until symptoms subside and range of motion is reasonably comfortable. For type II separations, most orthopedic surgeons recommend use of a sling for 1-2 weeks or until symptoms subside, in combination with a rehabilitation program emphasizing maintaining or regaining range of motion. However, because the AC ligaments are disrupted, heavy lifting and contact sports should be avoided for 6-12 weeks to allow healing and prevent progression to a type III injury.^{[24,25 ]}

If nonoperative management is chosen after a type III separation, the treatment is similar to that for a type II injury.

Surgical Therapy

Many procedures have been described for the repair of acute and chronic type III through type VI injuries. These all include open reduction and stabilization of the dislocation with repair of the usually torn deltotrapezial fascia and debridement of the acromioclavicular (AC) articulation. Bosworth described the use of a screw placed from the clavicle into the coracoid base to stabilize the articulation,^{[26 ]}while others have used bioabsorbable or nonbioabsorbable devices passed through a drill hole in the clavicle and around the coracoid base. Pins placed through the acromion, across the AC joint, and down the clavicle have also been used. The AC ligaments and coracoclavicular (CC) ligament are repaired, if possible. Many authors have also advocated performing a distal clavicle excision at the time of the operative repair, especially in late reconstructive procedures.^{[25,27,28,29,30 ]}

Weaver and Dunn described a procedure designed to reconstruct the CC ligament by excising the distal end of the clavicle and transferring the acromial attachment of the coracoacromial (CA) ligament to the resection site.^{[31,32 ]}

Symptomatic AC joint arthrosis may occur after type I and type II injuries. When conservative measures fail, a distal clavicle resection provides predictable relief. This can be performed in both an open manner and an arthroscopic manner. The amount of bone resected has been debated; original descriptions suggested 1-2 cm, and the arthroscopic advocates suggest less (5-7 mm). Adequate bone should be resected to prevent AC contact during shoulder range of motion yet avoid violating the CC ligament.

Postoperative Details

Postoperatively, patients undergoing reconstructive procedures remain in a sling for 2 weeks. Thereafter, a progressive, passive, range-of-motion program is begun. The patient's arm remains in the sling between sessions. At 6 weeks, healing is sufficient to allow one to discontinue protection and encourage progressive functional use. Physiotherapy continues until range of motion and strength are maximized. Heavy physical use of the shoulder is prohibited for an additional 6 weeks. Patients undergoing a distal clavicle resection are simply protected in a sling for 2 weeks to allow soft-tissue healing to occur.

If a coracoclavicular screw or a trans-AC joint pin is used for stabilization, the device is removed 6 weeks postoperatively.

Follow-up

Postoperative follow-up is important. Patients are seen at 2-week intervals to monitor and update their rehabilitation program.

For excellent patient education resources, see eMedicine's Breaks, Fractures, and Dislocations Center. Also, see eMedicine's article on Shoulder Dislocation.

Complications

As with any injury, acromioclavicular (AC) separations may be accompanied by fractures and other disruptions, as well as by injuries to nonorthopedic systems. Most frequent are midclavicular, distal clavicular, acromial, and coracoid fractures.^{[33,34 ]}

Degenerative changes involving the AC joint are common late complications. Symptomatic traumatic arthritis may develop following nonoperative management of type I or II injuries. Surgery is often indicated to alleviate symptoms. Impingement symptoms, muscle-fatigue discomfort, and/or neurovascular symptomatology may occur in patients treated nonoperatively for type III separations and may require a surgical reconstruction.

Patients who undergo surgical repair of AC joint injuries are susceptible to the complications associated with any such procedure. These include wound infection, osteomyelitis, soft-tissue ossification, and failure of fixation with recurrent deformity. If pins or wires are used for fixation, migration may occur. Symptomatic AC joint arthritis may develop in patients who undergo surgical management acutely.

Outcome and Prognosis

For type I injuries, the prognosis following nonoperative care is excellent. Some studies have shown mild symptoms occurring in approximately 30% of heavy laborers, but significant symptoms are much less common.^{[35,36 ]}Most long-term studies have shown good-to-excellent outcomes following type II injuries managed nonoperatively as well. A small portion of this population will, however, report symptomatic AC degenerative disease that necessitates surgery.

Literature regarding long-term follow-up after surgical repair of type III injuries is scarce, and those treated nonoperatively generally do quite well.

Future and Controversies

Treatment for acute type III acromioclavicular injuries remains controversial (see Indications). Since those treated nonoperatively generally do quite well, surgical management should be offered acutely only to those who require high-level upper extremity function and late to those with significant shoulder pain and/or dysfunction refractory to nonoperative treatment. Given the proper choice of treatment, outcomes should be acceptable in more than 90% of patients.^{[13 ]}

Multimedia

Media file 1: Acromioclavicular joint anatomy.

Media file 2: Allman/Rockwood classification of acromioclavicular injuries.

Media file 3: Type V separation, characterized by wide displacement of the clavicle in a superior direction relative to the acromion. Radiographic findings denote disruption of the AC ligaments and coracoclavicular (CC) ligament, as well as the deltoid attachment to the distal clavicle.

References

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Keywords

acromioclavicular joint separation, AC separations, shoulder separation, acromioclavicular joint dislocation, AC dislocation, dislocated shoulder, shoulder pain

Contributor Information and Disclosures

Author

David Prybyla, MD, Staff Physician, Department of Orthopedic Surgery, University of Massachusetts Medical School
Disclosure: Nothing to disclose.

Coauthor(s)

Brett D Owens, MD, Chief, Sports Medicine and Shoulder Service, William Beaumont Army Medical Center
Brett D Owens, MD is a member of the following medical societies: American Academy of Orthopaedic Surgeons, American Orthopaedic Society for Sports Medicine, and Society of Military Orthopaedic Surgeons
Disclosure: Nothing to disclose.

Thomas P Goss, MD, Chief of Shoulder Surgery, Professor, Department of Orthopedic Surgery, University of Massachusetts Memorial Health Care
Thomas P Goss, MD is a member of the following medical societies: American Academy of Orthopaedic Surgeons, American Orthopaedic Association, Massachusetts Medical Society, and Orthopaedic Trauma Association
Disclosure: Nothing to disclose.

Medical Editor

Lynn A Crosby, MD, FACS, Chief of Shoulder Division, Professor, Department of Orthopedic Surgery, Wright State University School of Medicine
Lynn A Crosby, MD, FACS is a member of the following medical societies: Alpha Omega Alpha, American Academy of Orthopaedic Surgeons, American College of Sports Medicine, American College of Surgeons, American Fracture Association, American Medical Association, American Medical Tennis Association, American Orthopaedic Association, American Orthopaedic Foot and Ankle Society, Arthroscopy Association of North America, Mid-America Orthopaedic Association, and Orthopaedic Research Society
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment

Managing Editor

Pekka A Mooar, MD, Professor, Department of Orthopedic Surgery, Temple University School of Medicine
Pekka A Mooar, MD is a member of the following medical societies: American Academy of Orthopaedic Surgeons
Disclosure: Nothing to disclose.

CME Editor

Dinesh Patel, MD, FACS, Associate Clinical Professor of Orthopedic Surgery, Harvard Medical School; Chief of Arthroscopic Surgery, Department of Orthopedic Surgery, Massachusetts General Hospital
Dinesh Patel, MD, FACS is a member of the following medical societies: American Academy of Orthopaedic Surgeons, American Association of Physicians of Indian Origin, American College of International Physicians, and American College of Surgeons
Disclosure: Nothing to disclose.

Chief Editor

Mary Ann E Keenan, MD, Professor, Vice Chair for Graduate Medical Education, Department of Orthopedic Surgery, University of Pennsylvania School of Medicine; Chief of Neuro-Orthopedics Program, Department of Orthopedic Surgery, Hospital of the University of Pennsylvania
Mary Ann E Keenan, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Orthopaedic Surgeons, American Orthopaedic Association, American Orthopaedic Foot and Ankle Society, American Society for Surgery of the Hand, and Orthopaedic Rehabilitation Association
Disclosure: Nothing to disclose.

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Non-operative Versus Operative Treatment of Acute Acromioclavicular Joint Dislocation

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