Acromioclavicular Joint Disorders

Disease/Disorder

Definition

Acromioclavicular (AC) joint injury is a common yet underdiagnosed cause of shoulder pain.¹ Joint damage can occur due to a range of acute and chronic conditions with varying levels of severity. Disorders of the AC joint primarily include acute ligamentous injuries, from minor sprains to complete dislocation,¹ and progressive degenerative disease.²

Etiology

Most acute AC joint injuries are caused by direct trauma or a sudden axial load to the superolateral aspect of an adducted shoulder, forcing the humeral head superiorly into the acromion.¹ Injuries are common from falls, motor vehicle accidents, and sports. Conversely, degenerative pathology may be due to age-related tissue change, repetitive microtrauma, inflammatory disease, or chronic instability.²

Epidemiology including risk factors and primary prevention

Shoulder girdle injuries involve the AC joint approximately 10% of the time.¹ AC joint injury is five times more common in males¹ and primarily occurs young adults between the ages of 20 and 40 years.³ Incomplete injuries occur twice as frequently as complete dislocations.¹ The incidence of AC joint dislocation in the general population is 3-4 per 100,000 and 25-52% occur during sports.⁴ The highest rates of joint sprains have been reported in contact sports including rugby, hockey, wrestling, football, and lacrosse.³

Patho-anatomy/physiology

The AC joint is formed by the articulation between the distal clavicle and the acromion. It is surrounded by a capsule and reinforced by muscles and ligaments. The deltoid, trapezius, and serratus anterior muscles serve as the main dynamic stabilizers. Static stability is reinforced by the coracoclavicular (CC) and quadrangular AC ligament– composed of the superior, inferior, anterior, and posterior ligaments.¹ The AC ligaments primarily resist anterior and posterior displacement, whereas the CC ligaments primarily resist superior and axial translation.² The AC ligament is typically injured first, followed by the CC ligament.⁴ Innervation is provided by branches of the suprascapular and lateral pectoral nerves.²

Disease progression including natural history, disease phases or stages, disease trajectory (clinical features and presentation over time)

The six-stage Rockwood Classification System is currently the most widely accepted system for grading AC joint injuries. The severity of AC joint injury is based on the sequential disruption of the AC and CC ligaments with higher stages correspond to varying radiographically determined  clavicular displacement from the acromion(Table 1).⁵ The degree of disruption leads to instability of the AC joint complex which may require surgical intervention.⁴ The International Society of Arthroscopy, Knee Surgery, and Orthopedic Sports Medicine (ISAKOS) developed a specific subclassification of Rockwood type III AC injuries differentiating stable from unstable injuries to guide operative management.⁶ In a clinical setting, this can present as significant shoulder pain directly over the AC joint with impaired range of motion.³

Table 1: Rockwood Classification System with ISAKOS subclassification of Rockwood type III AC

Specific secondary or associated conditions and complications

Although infrequent, fractures of the acromion or distal clavicle can occur in association with severe ligamentous damage or complete dislocation of the joint.¹ Chronic injury may also develop as repetitive microtrauma leads to degenerative changes over time.² Distal clavicular osteolysis and chronic AC joint instability may result in secondary osteoarthritis.⁷ 

Essentials of Assessment

History

Key historical information includes mechanism of injury, onset of pain – whether it is acute (sprain/separation) versus chronic (arthrosis/distal clavicular osteolysis), location and quality of pain, exacerbating and alleviating factors, and functional limitations. Details of prior shoulder injuries and surgeries should be elicited, cervical or radicular pain or upper extremity weakness, as should previous treatments or interventions. 

Physical examination

Examination should begin with inspection of the shoulder complex for warmth, swelling or asymmetry including any abnormal bony protuberances at the level of the AC joint, palpation of bony prominences, and assessment of strength and range of motion, followed by comparison to the contralateral side.

Special tests evaluating reproduction of pain over the AC joint include⁸ 

• Cross arm adduction: Sensitivity 77%, specificity 79%⁹
• Active Compression Test (O’Brien’s): sensitivity 41%, specificity 95%⁹
  • This test is commonly used when investigating labral pathology and carries a different sensitivity and specificity for that specific injury. 
• Paxinos test: manual compression of AC joint
• Resisted Arm Extension: sensitivity 72%, specificity 85%⁹

Clinical functional assessment: mobility, self-care, cognition/behavior/affective state

AC joint injury may cause significant pain and difficulty performing activities of daily living that require reaching across midline or overhead, poorly impacting an individual’s quality of life.²  

Laboratory studies

Laboratory studies are not commonly used in the diagnosis of AC joint injuries.

Imaging

Standard shoulder x-ray views are useful however, a Zanca view is the most accurate way of evaluating the AC joint. It is performed by angling the beam 10 degrees cephalad and reducing the penetration to half that of a standard shoulder x-ray  and also helps to achieve a better view of the clavicle by decreasing the amount of superimposition of the scapula and clavicle on one another.^1,3 Horizontal AC joint instability is better detected with dynamic x-rays compared to static views.¹⁰ When differentiating Type 3 vs Type 4 lesions, an axial view will show the scapula anterior to the clavicle indicating a type 4 injury. Complete AC joint dislocation may result in a coracoid fracture which is diagnosed with the Stryker view.¹ CT can offer more precise evaluation of bone – fractures and degenerative changes, while MRI is more valuable for the evaluation of capsuloligamentous structures and surrounding tissue.¹¹

Supplemental assessment tools

The utility of diagnostic musculoskeletal ultrasound (US) is rapidly growing. For the AC joint, US offers high resolution imaging of the AC joint capsule and ligamentous structure as well as the cortical edges of the acromion and clavicle. While performing exam maneuvers such as cross arm adduction, joint space widening can be examined in real time with dynamic visualization for possible AC separation. Cortical irregularity can be seen, which would suggest a degenerative process.¹¹

Early prediction of outcomes

Severity of injury plays a key role in outcome. For those requiring surgical stabilization, most patients with non-labor occupations typically return to work within 6 months, however 8.8% of manual laborers who required surgery did not return to work at two years follow up in a recent retrospective study.¹² Presence of horizontal AC joint instability is also a predictor of worse clinical outcomes due to underdiagnosis or neglect.¹⁰   

Environmental

AC joint separation is more common in contact sport athletes. Occupations and sports that require repetitive overhead lifting have a higher prevalence of AC joint arthritis.¹³ It is also more common in patients with spinal cord injury, given increased demands placed on the upper extremities for mobility and transfers, with a prevalence of 50-71%.¹⁴

Social role and social support system

Impairment in ADLs are common with AC joint injury, due to restricted shoulder ROM, with dominant hand sided injuries causing further limitation. Family support coupled with robust rehabilitation plans are extremely important. Physicians should communicate closely with the rehabilitation team, including physical therapists and athletic trainers, to improve patient outcomes.

Professional issues

Controversy surrounds the management of grade III injuries where there is disagreement between the effectiveness of surgical versus non-surgical treatment. First and foremost, using evidence-based counseling, joint decision making with the patient and collaboration with surgical colleagues are of the utmost most importance.

Rehabilitation Management and Treatments

Available or current treatment guidelines

The Rockwood Classification System with ISAKOS subclassification of Rockwood type III AC injuries can guide clinicians between non-operative and operative treatment (Table 1).^1,6 A four-phase rehabilitation program has been described for treatment of non-operative AC joint injuries as outlined below (Table 2).¹⁵

Clinicians have also suggested a more practical approach for AC joint rehabilitation following the “PASS” pneumonic – pain control, decreasing apprehension with movements, and addressing anterior chest wall stiffness to improve scapular control. The goal of PASS therapy is to provide less-rigid protocols to encourage a more personalized rehabilitation process. Further research is needed to validate this approach.¹⁶

At different disease stages

For non-operative acute or traumatic ACJ injuries, a four-phase rehabilitation program has been described (Table 2).¹⁵

Table 2: Step-wise Rehabilitation Recommendations for AC Joint Injuries

Goals of immobilization include pain relief, joint stability, and prevention of further injury by supporting the humerus, preventing downwards traction of the shoulder girdle and scapula. Distal and lateral clavicular bracing is favored to avoid direct pressure over the AC joint.¹⁵ Commonly used bracing includes the Kenny-Howard brace (worn for 6-8 weeks to allow ligaments to heal), RJ bandage,⁴ or the Lerman platform brace (lesser degree of AC joint reduction).¹⁵ Caution must be used with braces to avoid skin irritation or breakdown, nerve compression (including anterior interosseous nerve), or improper fit.¹⁵

In chronic degenerative ACJ disease, diagnostic and therapeutic corticosteroid joint injections are more widely accepted. Ultrasound guidance can improve the accuracy of these injections. Injections can provide short-term pain relief at rest and during activity, and improve baseline passive ROM and shoulder function. However, not all patients adequately respond after a single injection and may require reintervention in the form of repeat injection or surgical intervention.¹⁷ Once pain is adequately controlled with as needed NSAIDs and/or injections, a therapy program should be pursued with focus on improving ROM while strengthening periscapular and RTC structures and emphasizing postural and scapular control. Avoidance of repetitive aggravating movements such as overhead of cross-body movements should be advised to help with pain relief.²

Coordination of care

It is important to coordinate care between surgeons, radiologists, physiatrists, therapists, and the patient. Determination of management (operative versus non-operative) should include all team members to ensure successful outcomes. For athletes, it is important to include the coaching and athletic training staff.¹⁵  

Patient & family education

Patients should actively participate in the rehabilitation process to guide progression through the various phases of rehabilitation. In athletes, it is important to educate the patient and coaching/athletic trainer staff regarding the risks and benefits of any local anesthetic or steroid injections requested for earlier return to play.¹⁵ It is also important to consider that in young and athletic populations, operative management may delay return the time to return to work and sports.¹⁸

Measurement of treatment outcomes including those that are impairment-based, activity participation-based and environmentally-based

Outcome measures commonly used to assess ACJ injuries include

• Disabilities of the Arm, Shoulder, Hand (DASH) Score
• American Shoulder and Elbow Surgeons (ASES) Score
• Constant Score
• Simple Shoulder Test (SST) Score
• University of California Los Angeles (UCLA) Shoulder Score

Other general quality of life tools include the 36-Item or 12-Item Short Form Health Survey (SF-36 and SF-12, respectively).¹⁹  

Translation into Practice:  practice “pearls”/performance improvement in practice (PIPs)/changes in clinical practice behaviors and skills

While corticosteroid injections can be useful for pain relief following acute or traumatic AC joint injuries, there may be a deleterious effect on natural healing and inflammatory response, however, most believe they are reasonable when done sparingly.²⁰ Others suggest they may negatively alter perceptions of pain and worsen long-term outcomes.¹⁵ Careful consideration of risks and benefits is important prior to any procedure.

Cutting Edge/Emerging and Unique Concepts and Practice

• Arthroscopic CC ligament reconstruction using a semitendinosus graft is becoming a commonly employed surgical technique^3,4
• A single tendon, simultaneous reconstruction of the AC and CC ligaments may provide greater stability when compared to isolated CC reconstruction²¹
• Modifications to current surgical procedures including additional AC joint suture cord cerclage, combined AC and CC ligament reconstruction, and Twin Tail TightRope triple button technique aim to address horizontal AC instability and have been shown to improve patient outcomes¹⁰
• Prolotherapy (15% dextrose solution) may be an effective treatment option for ACJ arthropathy or moderate-to-severe acromial enthesopathy²²
• Platelet rich plasma (PRP) has been shown as an alternative treatment option for AC joint arthropathy with statistically significant improvements in function up to 6-months following injection²³
• Autologous adipose-derived mesenchymal stem cell therapy is a new treatment option for ACJ OA but requires further research to support its use and long term effects²⁴

Gaps in the Evidence-Based Knowledge

• There remains significant controversy regarding whether Grade III injuries are best treated with non-operative or operative management.^4,15 Studies have not identified a significant difference in functional outcome, however operative management may be considered in those with persistent pain.¹⁸ Recently the ISAKOS developed a specific subclassification of Rockwood type III AC injuries to help guide operative management⁶
• Conservative and surgical treatments are both effective for ACJ OA, and there is a lack of evidence illustrating the superiority of one technique over the other²⁵

References

1. Gilot G, Mutnal AB, Owens J. Ch. 15: Epidemiology, Clinical Evaluation, Imaging, and Classification of Acromioclavicular Joint Injuries.” Disorders of the Shoulder: Diagnosis and Management – Shoulder Trauma, Lippincott, Williams & Wilkins, 2014.
2. Mall NA, Foley E, Chalmers PN, Cole BJ, Romeo AA, Bach BR. Degenerative Joint Disease of the Acromioclavicular Joint: A Review. Am J Sports Med. 2013 Nov;41(11):2684–92.
3. Peebles LA, Akamefula RA, Kraeutler MJ, Mulcahey MK. Management of Acromioclavicular Joint Injuries: A Historic Account. Clin Sports Med. 2023 Oct;42(4):539–56.
4. Babhulkar A, Pawaskar A. Acromioclavicular joint dislocations. Curr Rev Musculoskelet Med. 2014 Mar;7(1):33–9.
5. Williams GR, Nguyen VD, Rockwood CA. Classification and radiographic analysis of acromioclavicular dislocations. Appl Radiol. 1989;18(2):29–34.
6. Velasquez Garcia A, Abdo G. Reliability of the ISAKOS Modification to Subclassify Rockwood Type III Acromioclavicular Joint Injuries. Orthop J Sports Med. 2022 Dec;10(12):23259671221133379.
7. Singh M, Soo Hoo J. A Sports Medicine Clinician’s Guide to the Diagnosis and Management of Distal Clavicular Osteolysis. Curr Sports Med Rep. 2023 Jun;22(6):230.
8. Chang KV, Wu WT, Hsu PC, Lew HL, Özçakar L. Clinical Tests of the Shoulder: Accuracy and Extension Using Dynamic Ultrasound. Am J Phys Med Rehabil. 2020 Feb;99(2):161–9.
9. Chronopoulos E, Kim TK, Park HB, Ashenbrenner D, McFarland EG. Diagnostic value of physical tests for isolated chronic acromioclavicular lesions. Am J Sports Med. 2004 May;32(3):655–61.
10. Aliberti GM, Kraeutler MJ, Trojan JD, Mulcahey MK. Horizontal Instability of the Acromioclavicular Joint: A Systematic Review. Am J Sports Med. 2020 Feb 1;48(2):504–10.
11. Precerutti M, Formica M, Bonardi M, Peroni C, Calciati F. Acromioclavicular osteoarthritis and shoulder pain: a review of the role of ultrasonography. J Ultrasound. 2020 Jul 15;23(3):317–25.
12. Porschke F, Schnetzke M, Studier-Fischer S, Gruetzner PA, Guehring T. Return to work after acromioclavicular joint stabilization: a retrospective case control study. J Orthop Surg. 2019 Feb 12;14:45.
13. Chaudhury S, Bavan L, Rupani N, Mouyis K, Kulkarni R, Rangan A, et al. Managing acromio-clavicular joint pain: a scoping review. Shoulder Elb. 2018 Jan;10(1):4–14.
14. Morgenroth DC, Gellhorn AC, Suri P. Osteoarthritis in the Disabled Population: A Mechanical Perspective. PM&R. 2012 May;4:S20–7.
15. Gilot G, Owens J. Mutnal AB. Ch. 16: Non-operative Management of Acromioclavicular Joint Injuries: Indications and Outcomes. Disorders of the Shoulder: Diagnosis and Management – Shoulder Trauma, Lippincott, Williams & Wilkins, 2014. In.
16. LeVasseur MR, Mancini MR, Berthold DP, Cusano A, McCann GP, Cote MP, et al. Acromioclavicular Joint Injuries: Effective Rehabilitation. Open Access J Sports Med. 2021 May;Volume 12:73–85.
17. Miedema N, Sierevelt I, Alta TDW, Vossen RJM, van Noort A. Mid- to long-term success rate and functional outcomes of acromioclavicular injections in patients with acromioclavicular osteoarthritis. Clin Shoulder Elb. 2023 Jun;26(2):175–81.
18. Saade F, Carminati F, Bouteille C, Lustig JP, El Rifaï S, Boyer E, et al. Acromioclavicular joint separation: Retrospective study of non-operative and surgical treatment in 38 patients with grade III or higher injuries and a minimum  follow-up of 1 year. Orthop Traumatol Surg Res OTSR. 2023 Jun;109(4):103405.
19. Reintgen C, Gerlach EB, Schoch BS, Mamelson K, Wright TW, Farmer KW, et al. What Outcome Measures Are Reported in the Management of Acromioclavicular Joint Injuries? Orthop J Sports Med. 2020;8(1):2325967119892322.
20. Nelson C. Anesthetic injections in football: an ethical dilemma. Sports Med Dig 2001; 23: 133.
21. Shin SJ, Campbell S, Scott J, McGarry MH, Lee TQ. Simultaneous anatomic reconstruction of the acromioclavicular and coracoclavicular ligaments using a single tendon graft. Knee Surg Sports Traumatol Arthrosc. 2014 Sep;22(9):2216–22.
22. Hsieh PC, Chiou HJ, Wang HK, Lai YC, Lin YH. Ultrasound-Guided Prolotherapy for Acromial Enthesopathy and Acromioclavicular Joint Arthropathy: A Single-Arm Prospective Study: Ultrasound-Guided Prolotherapy for a Painful AC Joint. J Ultrasound Med. 2019 Mar;38(3):605–12.
23. T S, Raja C R, Pst J, M U, Gowtham Manivannan A. PRP in acromio-clavicular joint arthritis – A prospective analysis. IP Int J Orthop Rheumatol. 2021 Jan 28;6(2):80–3.
24. Freitag J, Wickham J, Shah K, Tenen A. Effect of autologous adipose-derived mesenchymal stem cell therapy in the treatment of acromioclavicular joint osteoarthritis. BMJ Case Rep. 2019 Feb;12(2):e227865.
25. Soler F, Mocini F, Djemeto DT, Cattaneo S, Saccomanno MF, Milano G. No differences between conservative and surgical management of acromioclavicular joint osteoarthritis: a scoping review. Knee Surg Sports Traumatol Arthrosc. 2021 Jul;29(7):2194–201.

Original Version of the Topic

Kristian von Rickenbach, MD, MS, Mani Singh, MD, Nicholas Tsitsilianos, MD, Zainab Shirazi, MD. Acromioclavicular Joint Disorders. 5/11/2022

Author Disclosure

Ymi Ton, MD, MS
Nothing to Disclose

Jessica Ye, MD
Nothing to Disclose

Mani Singh, MD
Nothing to Disclose