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Views: 0 Author: Site Editor Publish Time: 2026-07-08 Origin: Site
Introduction
Acromioclavicular (AC) joint dislocation is one of the most common injuries involving the shoulder girdle and usually occurs after direct trauma to the lateral aspect of the shoulder.
High-energy impacts, sports injuries, and falls are the most frequent causes. The injury results from damage to the acromioclavicular ligament complex and coracoclavicular (CC) ligaments, leading to loss of stability between the distal clavicle and acromion.
The treatment strategy depends mainly on injury severity, displacement, soft tissue condition, patient activity level, and functional requirements.
Although several surgical techniques have been developed, including suture button fixation (TightRope), loop plate fixation, ligament reconstruction, and distal clavicle hook plate fixation, there is still ongoing debate regarding the optimal fixation method.
Currently, both hook plate fixation and coracoclavicular suspension techniques are widely used. Understanding their advantages, limitations, and indications is essential for selecting the most appropriate surgical approach.
The acromioclavicular joint is a small but important articulation between the distal clavicle and acromion.
Its stability depends on several structures:
Acromioclavicular ligament
Coracoclavicular ligament complex
Conoid ligament
Trapezoid ligament
Deltoid and trapezius fascia
When external force exceeds the strength of these stabilizing structures, the distal clavicle may displace superiorly or posteriorly, resulting in AC joint separation.
The injury is commonly classified according to the Rockwood classification system, which guides treatment decisions.
The Rockwood classification is the most widely used system for evaluating AC joint injuries.
It categorizes injuries based on:
Degree of ligament disruption
Direction and amount of clavicle displacement
Integrity of surrounding soft tissues
Type I injuries involve mild stretching or partial injury of the AC ligament.
Characteristics:
AC ligament sprain
No significant displacement
Normal coracoclavicular ligament
Most patients can be treated conservatively:
Ice application
Analgesics
Shoulder sling
Activity modification
Progressive rehabilitation exercises
Type II injuries involve complete disruption of the AC ligament with partial injury to the CC ligament.
Clinical findings include:
Mild clavicle elevation
AC joint instability
Local tenderness
Conservative treatment remains the preferred option:
Short-term immobilization
Pain control
Early range-of-motion exercises
Most patients achieve satisfactory shoulder function without surgery.
Type III injuries represent complete disruption of both:
Acromioclavicular ligament
Coracoclavicular ligament
The distal clavicle is displaced superiorly, resulting in obvious deformity.
The treatment of Type III injuries remains controversial.
Many surgeons recommend:
Sling immobilization
Pain control
Early rehabilitation
Surgery may be considered when:
Persistent pain remains after conservative treatment
Significant instability affects function
High-demand athletes require maximum shoulder stability
Cosmetic deformity is unacceptable
However, delayed surgery after failed conservative treatment may increase recovery time and influence functional outcomes.
Higher-grade injuries usually involve severe ligament disruption and significant displacement.
The distal clavicle is displaced posteriorly into the trapezius muscle.
A more severe form of Type III injury with:
Marked superior displacement
Extensive CC ligament disruption
Rare injury pattern with inferior displacement of the distal clavicle.
Type IV, V, and VI injuries generally require surgical stabilization due to:
Severe instability
Loss of shoulder biomechanics
Risk of chronic dysfunction
Currently, the two most commonly used surgical techniques include:
Distal clavicle hook plate fixation
Coracoclavicular suspension fixation (TightRope / suture button system)
Each technique has different biomechanical characteristics.
The TightRope technique reconstructs the function of the coracoclavicular ligament by creating a stable suspension between the clavicle and coracoid process.
A commonly used modified double-bundle suspension technique involves:
Three bone tunnels are prepared:
Two tunnels in the clavicle
One tunnel through the coracoid process
One set of high-strength sutures is passed through:
Medial clavicle tunnel
Coracoid tunnel
Another set is passed through:
Lateral clavicle tunnel
Around the base of the coracoid
This configuration recreates the stabilizing function of the native CC ligament complex.
Both suture loops are inserted into the same titanium button groove.
After reduction of the AC joint:
Sutures are tightened
The clavicle is reduced
Stable CC suspension is achieved
Unlike hook plates, TightRope systems usually do not require secondary surgery for implant removal.
Because there is no subacromial hook, normal scapulohumeral movement is less restricted.
The technique avoids:
Subacromial impingement
Acromial erosion
Hook-related pain
However, TightRope fixation also has disadvantages:
Without additional ligament reconstruction, some patients may experience:
Vertical instability
Loss of clavicle reduction
Potential problems include:
Clavicle fracture
Coracoid fracture
Tunnel enlargement
Accurate tunnel positioning is essential to reproduce normal CC ligament anatomy.
The distal clavicle hook plate is one of the most established fixation methods for Rockwood type III and above acromioclavicular (AC) joint dislocations.
Unlike TightRope fixation, which reconstructs the coracoclavicular ligament mechanically, the hook plate stabilizes the AC joint through a mechanical support principle.
The implant consists of:
A clavicular plate fixed to the distal clavicle
A curved subacromial hook inserted beneath the acromion
After reduction of the AC joint, the plate maintains the position of the distal clavicle by using the acromion as a stable fulcrum.
A superior approach is commonly used.
The surgical steps include:
Exposure of the distal clavicle
Identification of the AC joint
Removal of interposed soft tissue if necessary
Preparation of the clavicle surface for plate placement
Care should be taken to preserve:
Deltoid fascia
Trapezius attachment
Remaining ligament structures
because these tissues contribute to postoperative shoulder stability.
Before implant placement:
The distal clavicle is reduced to the anatomical position
The AC joint alignment is restored
The coracoclavicular distance is corrected
Temporary fixation may be achieved with:
Kirschner wires
Reduction clamps
Fluoroscopy can be used to confirm:
Clavicle height restoration
AC joint congruity
Coracoclavicular distance
The hook portion of the plate is inserted underneath the acromion.
The plate is then fixed onto the superior surface of the clavicle using screws.
The final position should ensure:
Stable contact between hook and acromion
No excessive pressure on the subacromial space
Restoration of normal clavicle position
One of the main advantages of hook plates is their excellent immediate mechanical stability.
The implant provides:
Vertical stability
Resistance against superior clavicle displacement
Reliable reduction maintenance
This makes it suitable for:
High-grade AC joint dislocations
Severe ligament disruption
Acute traumatic injuries
Compared with ligament reconstruction techniques, hook plate fixation has several technical advantages:
Shorter operation time
Less demanding surgical technique
No requirement for coracoid drilling
Lower dependence on ligament reconstruction accuracy
Therefore, it remains widely used in many trauma centers.
Because the hook mechanically supports the acromion, the surgeon can achieve relatively consistent restoration of:
Clavicle height
AC alignment
Coracoclavicular distance
Although hook plates provide reliable fixation, their disadvantages are mainly related to the subacromial hook design.
The hook plate maintains reduction by transferring force between:
Distal clavicle
Plate hook
Acromion
However, continuous contact and pressure between the hook and acromion may cause:
Local stress concentration
Bone resorption
Acromial erosion
Studies have reported that subacromial osteolysis may occur in approximately 42–45% of patients after hook plate fixation.
The risk increases with:
Poor hook-acromion matching
Type II or III acromion morphology
Excessive hook pressure
Incorrect plate positioning
Delayed implant removal
Patients may develop:
Persistent pain is one of the most common complaints after hook plate fixation.
Pain is usually associated with:
Subacromial irritation
Rotator cuff impingement
Hook-acromion conflict
Mechanical irritation beneath the acromion may restrict:
Forward elevation
Shoulder abduction
Overhead activities
Because of these complications, many surgeons recommend:
Routine removal of the hook plate after ligament healing, usually around 3–6 months after surgery.
The optimal position of the hook plate has become an important research topic because implant placement directly affects:
Hook-acromion contact area
Pressure distribution
Risk of osteolysis
Two main factors determine hook plate position:
The hook can be placed:
More medially
More laterally
depending on the width of the acromion.
The hook orientation relative to the acromion also influences implant matching.
Biomechanical studies have evaluated different hook positions.
Researchers defined the hook angle as:
The angle between the longitudinal axis of the clavicle hook and a line perpendicular to the acromial width plane.
Different positions were compared:
Medial placement group
Lateral placement group
with different hook angles:
−10°
0°
+10°
+20°
+30°
Contact length:
Minimum: approximately 4.38 mm (+10°)
Maximum: approximately 5.71 mm (0°)
Contact length:
Minimum: approximately 5.42 mm (+30°)
Maximum: approximately 8.85 mm (0°)
The lateral position generally provided a larger contact length.
Contact width:
2.97 mm to 3.17 mm
Contact width:
3.14 mm to 3.91 mm
The lateral position demonstrated improved hook-acromion matching.
Matching rate:
Approximately 10%–70%
The best matching occurred at:
0°
The poorest matching occurred at:
−10°
Matching rate:
Approximately 55%–100%
Optimal positions:
0°
+10°
Both achieved nearly complete contact matching.
Based on biomechanical analysis:
The hook plate tends to achieve better acromial conformity when:
Positioned relatively laterally
Maintained at approximately 0° to +10° orientation
This configuration provides:
Larger contact area
Better pressure distribution
Reduced stress concentration
Potentially decreasing the risk of:
Subacromial osteolysis
Implant-related pain
The hook should provide support, not compression.
Excessive downward pressure may increase:
Acromial erosion
Shoulder impingement
Intraoperative imaging should evaluate:
Hook depth
Acromion contact
Clavicle reduction
Because the hook remains beneath the acromion, planned removal should be considered after sufficient ligament healing.
The choice between TightRope fixation and distal clavicle hook plate fixation remains controversial in the surgical treatment of acromioclavicular (AC) joint dislocation.
Both techniques can restore AC joint stability, but they rely on completely different biomechanical concepts.
Hook plate fixation provides temporary mechanical stabilization through acromial support.
TightRope fixation reconstructs the function of the coracoclavicular ligament through dynamic suspension.
Therefore, the optimal fixation method should be selected according to:
Injury type
Ligament damage pattern
Patient activity requirements
Surgeon experience
Soft tissue condition
The hook plate works by creating a fixed connection between:
Distal clavicle
Subacromial space
Acromion
The implant directly prevents superior displacement of the clavicle.
Strong initial fixation
Immediate postoperative stability
Simple surgical technique
Suitable for severe acute instability
Restricts physiological AC joint movement
Requires secondary implant removal
Risk of subacromial irritation
The TightRope system aims to reproduce the function of the native coracoclavicular ligament.
The fixation relies on:
High-strength sutures
Titanium buttons
Clavicle-coracoid suspension
Unlike hook plates, it allows more physiological movement between:
Clavicle
Scapula
Acromion
Feature | Hook Plate Fixation | TightRope Fixation |
|---|---|---|
Fixation principle | Mechanical support under acromion | Coracoclavicular ligament reconstruction |
Initial stability | Excellent | Excellent |
Surgical difficulty | Relatively simple | More technically demanding |
Implant removal | Usually required | Usually not required |
Subacromial irritation | Higher risk | Minimal |
Shoulder motion | May be temporarily restricted | More physiological |
Coracoid drilling | Not required | Required |
Risk of fracture | Lower | Possible clavicle/coracoid fracture |
Suitable for acute injuries | Yes | Yes |
Suitable for chronic instability | Limited | Often preferred with ligament reconstruction |
Hook plate fixation remains a reliable choice in patients with:
Especially:
Rockwood type V injuries
Severe clavicle displacement
Complete CC ligament disruption
The strong mechanical support helps maintain reduction during early healing.
Because the surgical technique is straightforward, hook plates are still widely used in:
Trauma centers
Emergency fixation situations
For athletes and high-demand patients, preserving normal shoulder biomechanics is important.
Advantages include:
No subacromial implant
No routine implant removal
Better restoration of dynamic stability
TightRope may be preferred in patients with:
Small acromion
Type II or III acromion morphology
High risk of subacromial impingement
For chronic injuries, TightRope is often combined with:
Tendon graft reconstruction
Coracoclavicular ligament reconstruction
to restore long-term stability.
Modern surgical concepts have gradually shifted from pure mechanical fixation toward anatomical reconstruction.
The current trend is:
Suitable when:
Immediate stability is required
Severe displacement exists
Simple reliable fixation is preferred
Suitable when:
Anatomical ligament restoration is prioritized
Long-term shoulder function is important
A practical decision-making approach:
According to Rockwood classification:
Type I–II → Conservative treatment
Type III → Individualized decision
Type IV–VI → Usually surgical treatment
Consider:
Ligament damage
Deltoid-trapezius fascia injury
Chronic instability
Prefer:
→ TightRope or anatomical reconstruction
Prefer:
→ Reliable fixation method according to surgeon experience
Both techniques can achieve good outcomes when performed correctly.
The key factors affecting success include:
Accurate reduction
Restoration of coracoclavicular distance
Protection of soft tissues
Appropriate rehabilitation
Short Answer:
TightRope and hook plate fixation are both effective surgical treatments for acromioclavicular joint dislocation. TightRope provides more physiological coracoclavicular stabilization without subacromial irritation or routine implant removal, while hook plates offer stronger immediate mechanical fixation but may cause subacromial osteolysis and usually require later removal. The optimal choice depends on injury severity, patient demands, and surgical experience.
Yes. Despite the development of newer fixation techniques, hook plates remain widely used because they provide strong initial stability and predictable reduction, especially in high-grade acute AC joint dislocations.
In most cases, yes.
Because the hook remains beneath the acromion, delayed removal is commonly recommended after ligament healing to reduce complications such as:
Subacromial impingement
Osteolysis
Shoulder pain
The main disadvantages include:
Technical difficulty
Risk of clavicle or coracoid fracture
Possible loss of reduction
Dependence on accurate tunnel placement
Many studies suggest that both techniques can achieve satisfactory functional outcomes.
However:
TightRope may provide better long-term comfort due to absence of subacromial hardware.
Hook plates may provide stronger early mechanical stability.
There is no universally accepted single gold standard.
Current evidence supports both:
Hook plate fixation
Coracoclavicular suspension techniques
The choice should be individualized based on patient factors and surgeon preference.
Acromioclavicular joint dislocation is a common shoulder injury with highly variable clinical presentations. Although conservative treatment is effective for low-grade injuries, unstable injuries such as Rockwood type IV, V, and VI often require surgical stabilization.
Currently, distal clavicle hook plate fixation and coracoclavicular suspension fixation (TightRope) remain two of the most widely used surgical techniques.
The hook plate provides:
Strong initial mechanical stability
Reliable reduction
Simple surgical operation
However, surgeons should be aware of potential complications including:
Subacromial irritation
Acromial osteolysis
Shoulder impingement
Need for implant removal
TightRope fixation focuses on restoring the anatomical function of the coracoclavicular ligament complex.
Its advantages include:
More physiological shoulder biomechanics
No subacromial implant
Reduced risk of hook-related complications
However, it requires:
Accurate anatomical positioning
Greater surgical experience
Careful management of bone tunnels
The current trend in AC joint reconstruction has shifted from simple mechanical stabilization toward anatomical and functional restoration of the coracoclavicular ligament complex.
Rather than considering one technique universally superior, the optimal fixation method should be selected based on:
Rockwood injury classification
Acute versus chronic injury
Soft tissue condition
Patient activity requirements
Surgeon expertise
A well-planned surgical strategy and accurate restoration of AC joint anatomy remain the most important factors determining clinical outcomes.
