Schulterinfo.ch - Acromioclavicular AC Joint - Dislocation / Trauma
Schulterinfo.ch
Abstract
Acromioclavicular dislocation, or also called acromioclavicular syndrome, is a non-physiological translation of the clavicula, which causes structural damage to the ligaments of the acromioclavicular joint.
These injuries are a result of direct impact to the superior or lateral aspect of the shoulder. Often, patients report on falling on the ab-/adducted shoulder or the outstretched arm or on having participated in contact sports such as rugby, American football, or ice hockey.
Acromioclavicular dislocation accounts for 4-12% of all shoulder injuries.
Patients present with pain over the acromion and, depending on the severity of the injury, may show up with the pathognomonic ‘’piano-key-sign’’. An elevation of the clavicula that rebounds after applying downward pressure.
Diagnosis can be made clinically. However, to confirm the diagnosis and to rule out other structural damage an ultrasound and x-ray is performed. To assess all ligaments around the coracoid and the clavicle, MRI should be considered.
Depending on classification type, immobilisation in a sling or surgical reduction and reconstruction of the ligamentous apparatus is required.
Acromioclavicular dislocation (ACD) is a non-physiological translation of the clavicula resulting in minor or major damage of the ligamentous apparatus of the acromioclavicular joint capsule.
Dislocations of the acromioclavicular joint stem from injuries with direct impact to the superior or lateral aspect of the shoulder with the arm adducted or falling on the outstretched arm [1]. Often contact sports such as rugby, American football and ice hockey are associated with these types of injuries [1]. The degree of force correlates with the damage caused in the process, as low force may only lead to a sprain and as force increases, ligaments may rupture [1, 2].
According to the Rockwood Classification, the pathologies can be divided into six different types. For a precise radiological description of each Rockwood type please visit Radiopedia.
AC-dislocations are very common and affect around 3-4/100’000 inhabitants [1]. 25% to 52% occur while participating in some sort of sport activity [1], as these type of injuries account for 4-12% of all shoulder girdle injuries [3].
Right after trauma, patients present with severe pain over the acromion, especially when trying to move the shoulder [1]. Hence, patients usually present with their affected arm in adducted position in order to relieve pain [3]. The range of motion may be affected as around 20% of patients present with a stiff shoulder, most likely due to concomitant rotator cuff injuries. [1] Not rarely, patients with type I or even type II injury postpone their visit to the doctor, since they associate the pain with a simple bruise. Depending on the type of injury, deformity can range from slight to blatant asymmetries (e.g. placement of clavicula under the coracoid in type VI). It should be noted that a superior displaced clavicula is a major indicator for damage of the structures of the acromioclavicular joint [1].
The medical history should contain:
- Traumatic event?
- The most common cause is a fall onto the acromion with the arm in adducted position
- When was the traumatic event?
- How many traumatic events?
- Degree of force
- Previous shoulder pathologies?
Diagnosis can be made clinically as a blatant elevation of the distal end of the clavicula compared to the healthy shoulder is pathognomic for a dislocation of the AC-joint [3]. Additional signs such as tenderness on palpation, bruises and patients' history may substantiate suspicion [3].
Specialized testing includes (videos at the end of the page):
- Paxino’s sign
- Patient is sitting upright with the affected arm hanging loosely to his side. The examiner places his/her thumb on the posterolateral side of the acromion, while his/her middle and index finger are placed superior to the mid-segment of the clavicula. With the examiners thumb pressing anterosuperior and the index and middle finger applying inferior directed force, pain is increased in positive finding.
- O’Brien’s test
- With the patient in either sitting or standing position, the examiner brings the shoulder in 90° flexion and 10-15° adduction. The patient is instructed to fully internally rotate the shoulder and pronate in the elbow. The examiner subsequently applies downward force on the patient’s forearm as he/she presses against it. This is recreated, although this time the patient fully externally rotates the shoulder and supinates in the elbow. The test is positive if pain can be felt, especially if pain is alleviated in supination. Since O’Brien’s test was originally created to diagnose SLAP-lesions, the positive findings can further be distinguished. If pain ‘sits deep in the shoulder’ it usually indicates a SLAP-lesion. If pain however is situated above or in the AC-joint and the pain is noty full alleviated by supination, one should lean towards pathologies of the AC-joint.
Specialized tests for the acromioclavicular joint should not be used as a singular diagnostic tool as sensitivity and specificity are comparably low. However, a combination of both the Paxino’s sign and the O’Brien’s test has shown to have the highest likelihood ratio (2.71) and the highest specificity, when performed in series [4]. If pre-test probability is already indubitable due to the patient’s history and rough examination, specialized physical examination is of no importance [4].
To classify injuries into Rockwood types and rule out any collateral damage to the clavicula, two x-ray images, one in ap and the other in weight-bearing Alexander/Zanca view should be performed [3]. Instructions on how to interpret x-ray images can be found on Radiopedia. In addition, ultrasound and MR imaging might be used to further assess damage to ligaments or the rotator cuff [5].
- Fracture of clavicula
- AC joint osteoarthritis
- AC joint synovitis with all its possible causes
- Type I Injury
- This type is always treated conservative. The treatment consists of immobilization with a sling up to 10 days and nonsteroidal medication against pain. The usage of the sling can gradually be reduced until after two weeks activities may be done unrestrictedly [2].
- Type II Injury
- Only in exceptional cases conservative treatment does not come into effect. A sling should be worn up to two weeks during which physiotherapy with active and passive mobilization should be done according to the pain of the patient. Heavy lifting, pushing, pulling and contact sports should be avoided for at least three weeks [2].
- Type III Injury
- There has been much ambiguity in treatment guidelines surrounding Rockwood type III injuries. At present, guidelines suggest that treatment options should be evaluated individually for each patient. Indications for invasive treatment are therefore patients with persisting symptoms or limited function after conservative treatment for the course of 6-12 weeks [2]. This suggests that young, active athletes or patients, who work overhead lean towards the surgical approach [2].
- Type IV-VI Injuries
- These types of injuries are altogether managed surgically with joint reduction or reconstruction of ligamentous structures [2].
Prognosis and progressive course of disease
There is a lack of data surrounding long term outcome of acromioclavicular dislocations. This is most certainly due to the different treatment options of each Rockwood type injury. However, prognosis seems to be satisfactory, although arthrosis has been reported after both conservative and surgical treatment.
- Babhulkar, Ashish, and Aditya Pawaskar. 2014. "Acromioclavicular Joint Dislocations". Current Reviews In Musculoskeletal Medicine 7 (1): 33-39. doi:10.1007/s12178-013-9199-2.
- Stucken, Charlton, and Steven B. Cohen. 2015. "Management Of Acromioclavicular Joint Injuries". Orthopedic Clinics Of North America 46 (1): 57-66. doi:10.1016/j.ocl.2014.09.003.
- Martetschläger, Frank, Natascha Kraus, Markus Scheibel, Jörg Streich, Arne Venjakob, and Dirk Maier. 2019. "The Diagnosis And Treatment Of Acute Dislocation Of The Acromioclavicular Joint". Deutsches Aerzteblatt Online. doi:10.3238/arztebl.2019.0089.
- Krill, Michael K., Samuel Rosas, KiHyun Kwon, Andrew Dakkak, Benedict U. Nwachukwu, and Frank McCormick. 2018. "A Concise Evidence-Based Physical Examination For Diagnosis Of Acromioclavicular Joint Pathology: A Systematic Review". The Physician And Sportsmedicine 46 (1): 98-104. doi:10.1080/00913847.2018.1413920.
- Aliberti, Gianna M., Matthew J. Kraeutler, Jeffrey D. Trojan, and Mary K. Mulcahey. 2019. "Horizontal Instability Of The Acromioclavicular Joint: A Systematic Review". The American Journal Of Sports Medicine 48 (2): 504-510. doi:10.1177/0363546519831013.
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