Joints and ligaments · Upper limb
Trapezoid ligament !
The trapezoid ligament is a flat band from the coracoid process to the collarbone; with the conoid it keeps the collarbone and acromion level.
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What it is
The outer, flat coracoclavicular ligament; torn with the conoid in higher-grade shoulder separations.
What it does
Works with the conoid to keep the collarbone and the acromion level.
Key facts
- Attaches
- Upper coracoid to the trapezoid line of the clavicle
- Function
- Resists medial displacement of the scapula / AC compression
- Tight in
- Horizontal (medial) loading of the shoulder
Relations
- Above
- Trapezoid line on the underside of the lateral clavicle
- Below
- Upper surface of the coracoid process
- Medial
- Conoid ligament, behind and medial to it
- Lateral
- AC joint and the AC ligament
- In front
- Front deltoid, which covers it
How to find it
Not palpable. It runs from the upper surface of the coracoid to the trapezoid line on the underside of the clavicle, in front of and lateral to the conoid ligament; at arthroscopy it comes into view from below once the coracoid base is cleared.
Examination
- Piano-key sign: when both CC ligaments are torn, the raised outer end of the clavicle can be pushed down and springs back up on release
On imaging
It cannot be seen on X-ray: its failure is inferred from a widened coracoclavicular distance on bilateral AP or Zanca views. MRI or ultrasound shows the two CC ligaments directly when the grade is unclear (type III versus V).
Common problems
- Shoulder separation: a fall on the point of the shoulder sprains or tears the AC ligament, then the coracoclavicular ligaments.
- In severe cases the collarbone end sticks up as a visible bump.
- Later wear and arthritis of the AC joint.
How it is diagnosed
Tenderness and a step at the top of the shoulder. X-rays (sometimes comparing both sides) grade the separation.
Treatment
- Sling, ice and early motion for mild and moderate separations.
- Surgery to reconstruct the coracoclavicular ligaments for severe separations or ongoing pain.
Clinical notes
- A coracoclavicular screw, a hook plate or suture-button fixation holds the clavicle down while the CC ligaments heal or a graft incorporates
- Distal clavicle excision must stay lateral to its footprint on the clavicle, or the clavicle becomes unstable
Related conditions
Test yourself
Think of the answer, then tap the question to see it.
How does the trapezoid ligament's role differ from the conoid ligament's?
The trapezoid mainly resists compression; the conoid mainly resists upward displacement of the clavicle.
In which Rockwood grades of AC injury is the trapezoid ligament sprained or torn?
Sprained in type II; torn with the conoid in type III and higher.
Why must distal clavicle excision stay lateral to the trapezoid ligament footprint?
Cutting medial to it leaves the clavicle unstable.
Educational information, not medical advice. For any symptom, see a health professional.
Its names
- Official Latin (TA2)
- ligamentum trapezoideum TA2 1748
- Official Spanish (DeCS)
- Ligamento trapezoideo
- English (TA2)
- Trapezoid ligament
- Also called
- coracoclavicular ligament (trapezoid part)
Related
Sources: Terminologia Anatomica (TA2); Anatomy, Shoulder and Upper Limb, Acromioclavicular Joint.
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Representative model, for educational purposes only.
