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Updated: Jun 13 2024

Acromioclavicular Joint Injury

Images
https://upload.orthobullets.com/topic/3047/images/Xray - AP - AC separation_moved.jpg
https://upload.orthobullets.com/topic/3047/images/ac separation type 3_moved.jpg
https://upload.orthobullets.com/topic/3047/images/14a_moved.jpg
https://upload.orthobullets.com/topic/3047/images/14b_moved.jpg
https://upload.orthobullets.com/topic/3047/images/cc screw pic.jpg
https://upload.orthobullets.com/topic/3047/images/hook plate.jpg
  • summary
    • An acromioclavicular joint injury, otherwise known as a shoulder separation, is a traumatic injury to the acromioclavicular (AC) joint with disruption of the acromioclavicular ligaments and/or coracoclavicular (CC) ligaments.
    • Diagnosis is made with bilateral focused shoulder radiographs to assess for AC and CC interval widening.
    • Treatment is immobilzation or surgical reconstruction depending on patient activity levels, degree of separation and degree of ligament injury.
  • Epidemiology
    • Incidence
      • common injury making up 9% of shoulder girdle injuries
    • Demographics
      • more common in males and athletes
  • Etiology
    • Pathophysiology
      • mechanism
        • direct blow to the shoulder
        • often sustained while falling onto the shoulder
  • Anatomy
    • Osteology
      • diarthrodial joint
        • articulation of the scapula (medial acromion) and the lateral clavicle
        • oblique orientation of joint surface
      • contains a fibrocartilaginous intraarticular disc between the osseous elements
        • analogous to the meniscus of the knee
        • involutes with age, disintegrates by age 40
    • Motion
      • primarily gliding motion
      • rotational motion is minimal
        • clavicle rotates 40-50° posteriorly with shoulder elevation
        • only ~8° rotation through the AC joint, due to synchronous scapuloclavicular motion
    • Ligaments
      • stability
        • static stability
          • joint capsule
          • acromioclavicular (AC) ligaments
            • controls horizontal motion and anterior-posterior stability
            • has superior, inferior, anterior and posterior components
              • posterior and superior AC ligaments are most important for stability
          • coracoclavicular (CC) ligaments
            • controls vertical motion and superior-inferior stability
            • two ligaments
              • conoid
                • attaches to the conoid tubercle, which is posteromedial to the trapezoid tubercle
                • inserts on clavicle 4.5cm medial to lateral edge
                • most important for vertical stability
              • trapezoid
                • attaches to the trapezoid tubercle, which is anterolateral to the conoid tubercle
                • inserts on clavicle 3cm medial to lateral edge
        • dynamic stability
          • anterior deltoid
          • trapezius
  • Presentation
    • Symptoms
      • pain
        • usually over AC joint
        • can also be referred to the trapezius
    • Physical exam
      • lateral clavicle or AC joint tenderness
      • abnormal contour of the shoulder compared to contralateral side
      • stability assessment
        • horizontal (anterior-posterior) stability evaluates AC ligaments
          • cross-body adduction
          • horizontal instability (ISAKOS type 3B) may indicate need for more aggressive treatment
        • vertical (superior-inferior) stability evaluates CC ligaments
      • AC joint exacerbation tests
        • O'Brien's test
          • superficial pain localized to AC joint is suggestive of AC joint pathology
            • deep pain is suggestive of a SLAP lesion
        • crossbody adduction 
  • Imaging
    • Radiographs
      • required views
        • bilateral anteroposterior (AP) view of AC joints
          • compare displacement to contralateral side
            • measured as distance from top of coracoid to bottom of clavicle
          • use 1/3 penetration on AP to visualize AC joint
        • axillary lateral view
          • required to diagnose Type IV (posterior)
        • zanca view
          • performed by tilting the x-ray beam 10-15° cephalad and using only 50% of the standard shoulder AP penetrance
      • additional veiws
        • cross-body adduction view (Basmania)
          • scapular Y performed with cross-body adduction stress
        • weighted stress views
          • usually no longer used
          • may help differentiate Type II from Type III
      • findings
        • fractures can mimic AC separations
          • base of coracoid fracture
          • Neer type 2A distal clavicle fracture
            • ligaments remain attached to distal fragment as proximal (medial) fragment displaces
  • Classification
      • Rockwood Classification
      • Type
      • AC ligament
      • CC ligament
      • Exam
      • Radiographs
      • Reducibility
      • Treatment
      • Illus.
      • XR
      • Type I
      • Sprain
      • Normal
      • AC tenderness
      • No AC instability
      • Normal
      • Reducible
      • Sling
      • Type II
      • Torn
      • Sprain
      • AC horizontal instability
      • AC joint disrupted
      • Increased CC distance < 25% of contralateral
      • Reducible
      • Sling
      • Torn
      • Torn
      • AC joint disrupted
      • Increased CC distance 25-100% of contralateral
      • Reducible
      • Controversial
      •  IIIA
      • AC vertical instability
      • No horizontal stability
      •  IIIB
      • AC vertical instability
      • Horizontal instability
      • Torn
      • Torn
      • Skin tenting
      • Posterior fullness 
      • Lateral clavicle displaced posterior through trapezius on the axillary lateral XR
      • Not reducible
      • Surgery
      • Type V
      • Torn
      • Torn
      • Severe shoulder droop, does not improve with shrug
      • Increased CC distance > 100% of contralateral
      • Not reducible
      • Surgery
      • Type VI
      • Torn
      • Torn
      • Rare; Associated injuries; paresthesias
      • Inferior dislocation of lateral clavicle, lying either in subacromial or subcoracoid position
      • Not reducible
      • Surgery
  • Differential
    • Coracoid fracture
      • base of coracoid fracture can mimic a CC ligament disruption
      • has superiorly displaced distal clavicle, but normal CC distance (normal is 11-13mm)
    • Distal Clavicle Fracture (Neer 2A)
      • can mimic AC separations as well, as ligaments remain attached to distal component
    • Pediatric medial clavicle physeal injury
    • Pediatric distal clavicle physeal injury
  • Treatment
    • Nonoperative
      • brief immobilization with early motion
        • indications
          • type I and II
          • type III in most individuals
            • good results when clavicle displaced < 2cm
        • techniques
          • brief sling immobilization, ice, activity modification, and physical therapy 
        • rehab
          • early shoulder range of motion
          • regain functional motion by 6 weeks
          • return to normal activity at 12 weeks
          • consider corticosteroid injections
        • outcomes
          • type III treated non-op had higher DASH scores at 6 weeks and 3 months, and equal function at 1 year with lower rate of secondary surgery (removal of hardware) compared to those treated operatively
        • complications
          • AC joint arthritis
          • chronic subluxation and instability
    • Operative
      • open reduction and internal fixation (ORIF) 
        • indications
          • acute type IV, V or VI injuries
            • recent studies suggest no difference in functional outcomes between operative and nonoperative interventions for high grade injuries
          • acute type III injuries in laborers, elite athletes, patients with cosmetic concerns
          • chronic type III injuries that failed non-op treatment
            • historically it was thought acute injuries were treated with ORIF and chronic injuries were treated with CC ligment reconstruction
              • however, new studies have shown no difference in outcomes in types III injuries treated surgically after 6 weeks non-op treatment versus immediate surgery
        • contraindications
          • patient unlikely to comply with postoperative rehabilitation
          • skin problems over fixation approach site
        • techniques
          • reduction
            • the goal is to reduce AC and CC interval
          • fixation
            • ligament reconstruction and/or soft tissue graft
              • Modified Weaver-Dunn
                • distal clavicle excision with transfer of coracoacromial ligament to the distal clavicle to recreate CC ligament
              • autograft
              • allograft
            • fixation with implants
              • suture
              • hook plate
              • CC screw (Bosworth)
              • cortical flip button (e.g Dog Bone)(+/- arthroscopic assistance)
              • K-wire
        • rehabilitation
          • sling immobilization for 6 weeks, no shoulder range of motion
          • return to full activity after 6 months
  • Techniques
    • ORIF with CC screw fixation (Bosworth screw)
      • has fallen out of favor
      • approach
      • technique
        • screw placement from distal clavicle to coracoid, superior to inferior
      • pros
        • rigid internal fixation
      • cons
        • danger of screw being too long and damage to critical structure below coracoid
        • routine screw removal at 8-12 weeks is advised to prevent screw breakage
          • due to normal motion between clavicle and scapula
      • complications
        • hardware irritation at level of screw purchase in coracoid
        • hardware failure at level of screw purchase in coracoid
    • ORIF with CC suture fixation
      • approach
        • proximal aspect of anterolateral approach to the shoulder
      • technique
        • suture placed either around or through clavicle and around the base of the coracoid
        • can also use suture anchors for coracoid fixation
      • pros
        • no risk of hardware failure or migration
      • cons
        • suture not as strong as screw fixation
        • requires careful suture passage inferior to coracoid due to proximity of crucial neurovascular structures
      • complications
        • suture erosion causing distal third clavicle fracture
        • hardware irritation
    • ORIF with AC pin fixation (Phemister Technique)
      • approach
        • can be done percutaneously
      • technique
        • smooth wire or pin fixation directly across AC joint
      • cons
        • hardware irritation
      • complications
        • high incidence of pin migration
        • generally not performed due to high complication rates
    • ORIF with AC hook plate fixation
      • approach
        • exposure of distal and middle clavicle
      • technique
        • use of standard hook plate over superior distal clavicle
      • pros
        • rigid fixation
      • cons
        • may require second surgery for plate removal if symptomatic
      • complications
        • acromial erosion
        • hook pullout
    • CC ligament reconstruction with coracoacromial (CA) ligament (Modified Weaver-Dunn)
      • approach
        • arthroscopic technique also described
      • technique
        • distal clavicle excision
        • transfer of coracoacromial ligament to the distal clavicle to recreate CC ligament
        • reinforce with internal fixation
      • cons
        • coracoacromial ligament only 20% as strong as normal CC ligament
        • lack of internal fixation risks failure of soft tissue repair
    • CC ligament reconstruction with free tendon graft
      • approach
        • can be performed arthroscopically-assisted
      • graft
        • autograft
          • palmaris longus
          • semitendinosus
        • allograft
          • tibialis anterior
      • technique
        • figure-of-eight passage of graft, looping around coracoid and fixation through clavicular tunnels
        • reinforce with internal fixation
      • pros
        • graft reconstruction more closely recreates strength of native CC ligament
      • cons
        • standard risks of allograft use or autograft harvest
        • lack of internal fixation risks failure of soft tissue repair
  • Complications
    • Residual pain at AC joint
      • 30-50%
    • AC arthritis
      • more common with surgical management than with nonoperative treatment
    • Hardware failure
      • CC screw breakage/pullout
    • Coracoid fracture
      • can occur with coracoid tunnel drilling
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