Definition
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Acromioclavicular joint separations are disruptions of the acromioclavicular joint complex.
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Injuries often involve both:
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Acromioclavicular ligaments
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Coracoclavicular ligaments
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Epidemiology
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Common in young and active adults.
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Frequently seen in athletes.
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High incidence in individuals exposed to direct shoulder trauma such as cyclists and football players.
Mechanism of Injury
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Most commonly caused by:
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Direct blow to the lateral aspect of the shoulder
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Fall onto an adducted arm
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Results in superior displacement of the clavicle relative to the acromion.
Classification
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Rockwood classification (Types I to VI)
- Type I: Sprain of the AC ligament. Normal radiograph
- Type II: AC ligament tear, coracoclavicular ligaments sprained. Radiograph demonstrates AC joint widening (normal AC joint distance is 1 to 3mm). Stress views show identical coracoclavicular distance compared to uninvolved side
- Type III: AC and coracoclavicular ligament torn. Radiograph demonstrates loss of AC joint relationship and increased coracoclavicular distance in stress view (25% to 100% greater than the normal side.).
- Type IV: Type III with distal clavicle displaced posteriorly into or through the trapezius
- Type V: Type III with the distal clavicle grossly displaced superiorly.
- Type VI: AC dislocated with the clavicle displaced inferior to the acromion or the coracoid.
Surgical Options Overview
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Coracoclavicular screw fixation
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Kirschner wire fixation
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Hook plate fixation
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Suspensory fixation systems
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Graft-based reconstructions using autograft, allograft, or synthetic materials
Coracoclavicular Screw Fixation
Concept
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Restores joint stability by reducing the coracoclavicular interval using a screw between the clavicle and coracoid.
Biomechanics
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Provides rigid fixation by transmitting load through the screw, indirectly stabilizing the conoid and trapezoid ligaments.
Technique
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A 4.5 millimeter cortical or lag screw is placed between the coracoid base and inferior clavicle.
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Fixation is maintained until ligament healing occurs.
Advantages
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Technically simple and reproducible
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Cost-effective
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Provides immediate stability
Limitations
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Excessive rigidity limits physiologic micromotion required for ligament healing
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Requires routine implant removal
Complications
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Screw loosening, breakage, or pull-out
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Loss of reduction due to implant failure or early loading
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Soft tissue irritation from prominent screw head
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Recurrent dislocation rates higher than suspensory fixation
Prevention Strategies
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Use partially threaded 4.5 millimeter screws with washers
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Avoid over-compression
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Plan implant removal at 8 to 12 weeks
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Avoid use in overhead athletes
Kirschner Wire Fixation
Concept
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Transarticular wires stabilize the acromioclavicular joint temporarily.
Technique
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Two wires placed across the joint under imaging guidance.
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Often combined with coracoclavicular ligament repair.
Advantages
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Simple and cost-efficient
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Provides short-term stability in acute injuries
Complications
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Wire migration into thorax or mediastinum
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Wire breakage or loosening
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Loss of reduction
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Pin tract infection
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Recurrent instability after wire removal
Prevention Strategies
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Use thick wires of at least 2 millimeters
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Bend wire ends externally
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Remove wires at 6 weeks
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Always combine with soft tissue or ligament augmentation
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Avoid in osteoporotic bone
Hook Plate Fixation
Concept
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A contoured plate with a hook placed beneath the acromion to restore alignment.
Biomechanics
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Acts as a lever to maintain reduction and allow early motion.
Technique
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Plate fixed to lateral clavicle with the hook engaging beneath the acromion.
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Implant removed after ligament healing, usually at 3 to 4 months.
Advantages
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Strong fixation
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Allows early postoperative range of motion
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Provides reliable vertical stability
Complications
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Loss of reduction
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Subacromial impingement and acromial erosion
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Rotator cuff irritation
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Mandatory second surgery for implant removal
Risk Factors for Failure
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Female sex
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Surgery delayed beyond 7 days
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Coracoclavicular displacement ratio greater than 1.5
Prevention Strategies
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Ensure proper hook depth and plate contouring
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Use hook angles between 0 and 40 degrees
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Timely implant removal
Suspensory Fixation Systems
Concept
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Uses cortical buttons and high-strength sutures to recreate coracoclavicular ligament function while allowing controlled micromotion.
Biomechanics
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Semi-rigid fixation resists superior translation while permitting physiologic movement.
Key Surgical Steps
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Achieve anatomic reduction
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Protect neurovascular structures
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Drill clavicular tunnel and deploy button beneath coracoid
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Restore coracoclavicular distance
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Augment with graft when required
Technical Variations
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Single clavicular tunnel
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Double clavicular tunnels for anatomic reconstruction
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Tunnel-free loop-around techniques
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Hybrid constructs combining suspensory fixation and graft
Complications
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Coracoid fracture, especially with multiple or large tunnels
Prevention Strategies
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Use central tunnels and dual-button constructs
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Avoid multiple coracoid tunnels
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Use tunnel-free techniques in fragile bone
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Follow protected rehabilitation for 6 weeks
Graft-Based Reconstructions
Concept
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Biological reconstruction of coracoclavicular ligaments using tendon grafts.
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Ideal for chronic injuries or failed previous fixation.
Types
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Weaver–Dunn procedure
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Modified Weaver–Dunn procedure
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Anatomic coracoclavicular ligament reconstruction
Graft Options
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Autograft: semitendinosus or gracilis
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Allograft: Achilles or tibialis tendon
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Synthetic grafts
Advantages
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Restores vertical and horizontal stability
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Promotes biological healing
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No routine implant removal
Complications
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Loss of reduction due to graft stretching
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Clavicle or coracoid fracture
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Tunnel widening
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Graft rupture or elongation
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Foreign body reaction with synthetic grafts
Prevention Strategies
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Prefer autograft for biological incorporation
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Restore native coracoclavicular distance of approximately 11 to 13 millimeters
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Combine with suspensory fixation for early stability
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Use tunnel-free techniques in small coracoids
Persistent Horizontal Instability
Definition
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Residual anteroposterior instability despite restoration of vertical alignment.
Cause
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Inadequate repair of acromioclavicular capsule and deltotrapezial fascia.
Incidence
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Reported in up to 40 percent after isolated coracoclavicular fixation.
Clinical Features
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Pain with cross-body adduction
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Mechanical clicking
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Prominent distal clavicle
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Functional limitation
Prevention
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Repair acromioclavicular capsule
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Add horizontal stabilization techniques
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Ensure proper clavicle positioning
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Meticulous deltotrapezial fascia closure
Peri-Implant Fractures
Common Sites
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Clavicle
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Coracoid
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Acromion
Risk Factors
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Multiple tunnels
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Large drill diameters
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Eccentric tunnel placement
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Early aggressive rehabilitation
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Poor bone quality
Common Causes of Failure
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Implant failure or migration
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Graft elongation or rupture
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Malpositioned tunnels
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Excessive or insufficient tension
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Premature return to activity
Prevention
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Achieve anatomic reduction
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Maintain physiologic tension
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Use combined fixation strategies
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Delay return to contact sports until healing confirmed
Nonsurgical Management
Indications
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Rockwood Type I injuries
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Rockwood Type II injuries
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Selected Rockwood Type III injuries in low-demand patients
Treatment Phases
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Immobilization phase: 0 to 3 weeks
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Rehabilitation phase: 3 to 6 weeks
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Return-to-activity phase: 6 to 12 weeks
Limitations
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Possible persistent pain or weakness
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Cosmetic deformity
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Risk of chronic instability or degenerative changes
Summary
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Acromioclavicular joint separations require treatment tailored to injury severity and patient demands.
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Numerous fixation techniques exist, each with specific advantages and complications.
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Loss of reduction and peri-implant fractures are the most common complications.
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Suspensory fixation and anatomic graft reconstructions provide superior biomechanical stability.
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Rigid fixation methods have higher complication rates and often require implant removal.
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Addressing horizontal instability and meticulous surgical technique are essential for optimal outcomes.
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Nonsurgical management remains effective for selected low-grade injuries when combined with structured rehabilitation.
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