Coracoclavicular joints

The coracoclavicular joint (CCJ) is an anomalous anatomical variant rather than a true pathological condition. It represents an accessory or supernumerary joint between the coracoid process of the scapula and the clavicle, typically in the region where the coracoclavicular ligament (conoid and trapezoid parts) would normally be present.

1. Cause and Etiology

The coracoclavicular joint is considered a developmental variant rather than a pathological lesion. It is thought to arise from:

Ossification of the coracoclavicular ligament, particularly in regions where repetitive mechanical stress may stimulate osteogenesis.
Congenital anomaly, representing a persistent phylogenetic remnant; in some primates and lower vertebrates, such a joint is physiologic.

Proposed etiological factors include:

Evolutionary remnants from quadrupeds.
Mechanical stress or repetitive microtrauma occurs in individuals with heavy overhead arm use.
Genetic predisposition or developmental ossification anomaly during embryogenesis.

2. Pathophysiology

The pathophysiological implications depend on whether the joint is asymptomatic or symptomatic:

In asymptomatic individuals:

The coracoclavicular joint is a non-functional or vestigial joint.
It may consist of fibrocartilage or hyaline cartilage-lined surfaces, sometimes with a small synovial cavity and a joint capsule.

In symptomatic individuals:

The joint may exhibit degenerative arthritic changes, including osteophyte formation, joint space narrowing, and subchondral sclerosis.
These changes may lead to localized pain or impingement of surrounding neurovascular structures (e.g., brachial plexus, subclavian vessels).
Chronic inflammation may also stimulate periarticular ossification and fibrosis.

3. Epidemiology

The coracoclavicular joint is rare in the general population. Key statistics:

Incidence:

Approximately 0.55–1.7% in anatomical and radiological studies.
Higher prevalence in males and in individuals with repetitive upper extremity activity (e.g., laborers, athletes).

Laterality:

May be unilateral or bilateral.
Bilateral presence is less common than unilateral.

Ethnic and geographic differences:

Some studies report higher prevalence in specific populations (e.g., Indian, Middle Eastern), although data is limited.

4. Clinical Presentation

Most cases are asymptomatic and discovered incidentally during imaging.

However, in symptomatic cases, patients may report:

Shoulder pain in the anterolateral or supraclavicular region.
Localized tenderness over the distal clavicle or coracoid.
Shoulder stiffness or pain with overhead activity.
Referred pain to the neck, trapezius, or arm.
Occasionally, thoracic outlet syndrome-like symptoms are due to mechanical compression.

Physical examination findings may include:

Tenderness on palpation.
Pain on resisted arm abduction.
No swelling or visible deformity in most cases.

5. Imaging Features

Plain Radiography (X-ray):

Best seen on axial or oblique projections.
May show a pseudoarticulation or synostosis between the coracoid process and clavicle.
Sclerosis, osteophyte formation, or joint space narrowing may be seen in symptomatic cases.

CT (Computed Tomography):

Gold standard for detailed osseous anatomy.
Provides clear evidence of joint surface congruency and articulation.
Demonstrates the true bony continuity or pseudarthrosis.

MRI (Magnetic Resonance Imaging):

Useful for evaluating associated soft tissue inflammation, degenerative changes, and possible impingement of nearby structures.
Shows cartilage lining, synovial changes, or joint effusion if present.

Ultrasound:

May reveal dynamic impingement or localized bursitis.
Less sensitive than CT/MRI for bony anomalies.

6. Treatment

Asymptomatic Patients:

No treatment required.
Educate the patient about the benign nature.

Symptomatic Patients:

Initial management is conservative:

Activity modification to reduce overhead movement.
NSAIDs (e.g., ibuprofen) for pain and inflammation.
Physical therapy to strengthen the rotator cuff and scapular stabilizers.
Corticosteroid injection into the joint under ultrasound or fluoroscopic guidance.

Surgical Management (rare):

Indicated for refractory cases or severe neurovascular impingement.
Options include:

Excision of the coracoclavicular joint (resection arthroplasty).
Coracoid or clavicle osteotomy if resection is incomplete.
Decompression procedures in cases of thoracic outlet syndrome.

7. Prognosis

Excellent prognosis in asymptomatic individuals; lifelong monitoring is usually unnecessary.
In symptomatic patients, conservative treatment is successful in the majority.
Surgical outcomes are favorable with symptom resolution in most patients, though it's rarely needed.
Recurrence of symptoms after resection is uncommon.

Summary Table

Aspect	Description
Cause	Developmental anomaly or ossified ligament
Etiology	Congenital variant, mechanical stress, phylogenetic remnant
Pathophysiology	Vestigial articulation may develop arthritic or compressive symptoms
Epidemiology	0.55–1.7% prevalence; more common in males and overhead workers
Clinical Presentation	Often asymptomatic; may cause shoulder pain or thoracic outlet symptoms
Imaging	CT is best for bone; MRI for soft tissue; X-ray may show joint/sclerosis
Treatment	Conservative (NSAIDs, PT); surgical resection if refractory
Prognosis	Excellent; most cases managed non-operatively with symptom resolution

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Case study: A 58-Year-Old Male Presenting with Dyspnea
Coracoclavicular Joints

History and Imaging

A 58-year-old male presented to the emergency department with complaints of dyspnea (shortness of breath).
Laboratory tests, including a complete blood count (CBC) and a comprehensive metabolic panel (CMP), were within normal limits and showed no remarkable findings.
The findings of the chest radiograph are as follows:

Quiz:

Which acute chest process is observed on the chest radiograph?
(1) Right upper lobe collapse with a hilar mass
(2) Bilateral patchy opacities concerning for multifocal pneumonia
(3) Right-sided pneumothorax
(4) Anterior mediastinal mass
(5) Acute left rib fracture
(6) No acute chest process is observed on the chest radiograph
Which chronic musculoskeletal process or anatomical variant is observed on the chest radiograph?
(1) Bilateral coracoclavicular joints
(2) Bilateral duplicated clavicles
(3) Chronic left rib fracture
(4) Both (1) and (2)
(5) Both (1) and (3)
(6) All of the above: (1), (2), and (3)
(G) None of the above
Explanation: The apparent double density of the clavicle is most likely due to a skin fold artifact.
The coracoclavicular joint can undergo osteoarthritic changes and may be a source of shoulder pain.
(1) True
(2) False
Which device is projected over the left mediastinum?
(1) Loop recorder
(2) Pacemaker
(3) Implantable cardioverter-defibrillator (ICD)
(4) None of the above
The device is located within the patient's thoracic cavity.
(1) True
(2) False

Findings and Diagnosis

Findings:
Chest radiographs (AP and lateral views) demonstrate no evidence of an acute chest process. There is a chronic left rib fracture. Normal variant bilateral coracoclavicular joints are observed (indicated by red arrows). The apparent double density of the clavicle is most likely due to a skin fold artifact.

Differential Diagnosis

Coracoclavicular joints
Healed clavicular fractures
Retained foreign bodies

Diagnosis: Coracoclavicular joints

Discussion

Coracoclavicular Joints

Pathophysiology and Epidemiology
A normal anatomical variant consisting of a true synovial joint between the conoid tubercle of the clavicle and the superior surface of the coracoid process.
More commonly observed in individuals of Asian descent, with a reported prevalence ranging from 0.5% to 20%. No significant sex predilection has been reported.

Clinical Presentation
Typically discovered incidentally on chest imaging.
It can develop osteoarthritic changes within the joint, which may lead to shoulder pain.

Imaging Findings
On chest or shoulder radiographs, the conoid tubercle of the clavicle appears enlarged and flattened on its inferior surface, forming a joint with the superior aspect of the coracoid process.

Management

No treatment is required for the anatomical variant itself.
Conservative or symptomatic management may be considered for patients with associated osteoarthritis.

References

Yammine K. The coracoclavicular joint: A systematic review of its anatomical, clinical and radiological aspects. Clin Anat. 2015;28(4):431-438. doi:10.1002/ca.22404
Prescher A, Klümpen T. The coracoclavicular joint: frequency, morphology, and clinical relevance. Acta Anat (Basel). 1997;158(3):220-225. doi:10.1159/000147971
Taneja AK, Hill JA, Rooney RJ. Coracoclavicular joint: a cause of shoulder pain. J Shoulder Elbow Surg. 1993;2(4):228-230. doi:10.1016/S1058-2746(09)80060-6
Allen JL, House JR, Fernandez JJ. Coracoclavicular joint: a rare cause of shoulder pain. Am J Orthop (Belle Mead, NJ). 2009;38(4):E64-E66.
Ogawa K, Naniwa T. Symptomatic coracoclavicular joint. Report of a case and review of the literature. J Bone Joint Surg Br. 1997;79(4):643-644. doi:10.1302/0301-620X.79B4.0790643

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