Distal clavicular osteolysis

1. Definition

Distal clavicular osteolysis (DCO) refers to a condition characterized by progressive resorption of the distal (lateral) end of the clavicle, typically resulting in pain and dysfunction at the acromioclavicular (AC) joint.

2. Cause and Etiology

Primary Cause

· Repetitive microtrauma to the acromioclavicular (AC) joint is the most common cause, especially in athletes and individuals involved in overhead or high-load upper limb activities.

Common Etiologic Factors

· Chronic mechanical stress: Frequently seen in weightlifters ("weightlifter's shoulder") due to repetitive stress from bench pressing, clean-and-jerk lifts, and other upper body workouts.

· Occupational causes: Manual laborers, carpenters, and construction workers.

· Trauma: A single episode of acute trauma to the AC joint may initiate osteolysis or accelerate progression in a joint already under repetitive stress.

· Iatrogenic: Post-surgical changes or complications (e.g., after distal clavicle resection or shoulder surgery).

· Infection, metabolic or inflammatory conditions (rare): Rheumatoid arthritis, hyperparathyroidism, or osteomyelitis may contribute, although these are less common.

3. Pathophysiology

Distal clavicular osteolysis is characterized by:

1. Repetitive subfailure microtrauma to the AC joint causes:

o Microfractures of subchondral bone.

o Disruption of normal bone remodeling.

o Vascular compromise and bone resorption.

2. Inflammatory response:

o Activation of osteoclasts in response to repeated injury.

o Increased bone turnover and resorption at the distal clavicle.

3. Histopathological changes:

o Replacement of bone with fibrovascular tissue.

o Infiltration by inflammatory cells.

o Cystic changes, necrosis, and trabecular disruption.

4. Chronic progression:

o Widening of the AC joint space.

o Cortical irregularity and fragmentation of the distal clavicle.

4. Epidemiology

· Age group: Most common in young to middle-aged adults (20–50 years old).

· Sex: Predominantly male due to higher participation in weightlifting and contact sports.

· Prevalence:

o High among athletes, especially weightlifters, bodybuilders, and contact sport players (football, wrestling, hockey).

o May be underdiagnosed in the general population due to subtle early symptoms.

5. Clinical Presentation

Symptoms

· Pain localized to the AC joint.

· Tenderness over the distal clavicle, aggravated by:

o Cross-body adduction.

o Overhead activities.

o Weightlifting.

· Decreased shoulder range of motion due to pain, especially with horizontal adduction.

· Weakness in overhead activities.

· Swelling or mild prominence at the AC joint (in some cases).

Physical Examination

· Point tenderness at the AC joint.

· Positive cross-body adduction test.

· Pain with resisted shoulder abduction or flexion.

· Possible crepitus or joint instability.

6. Imaging Features

A. Radiography (X-ray)

· Initial studies may appear normal.

· As DCO progresses:

o Resorption of the distal clavicle (loss of bone).

o Widened AC joint space.

o Subchondral cysts.

o Sclerosis and fragmentation of the distal clavicle.

o Best visualized on Zanca view (AP with cephalic tilt).

B. MRI

· Highly sensitive for early changes.

· Findings include:

o Bone marrow edema in the distal clavicle.

o Joint effusion in the AC joint.

o Soft tissue swelling or capsular thickening.

o Helps rule out other causes (e.g., tumor, infection).

C. CT Scan

· Provides detailed bone architecture.

· Useful in evaluating the degree of osteolysis and planning surgery.

D. Bone Scintigraphy

· Shows increased uptake at the distal clavicle, indicating active bone turnover.

7. Treatment

A. Conservative (First-line)

Most patients respond well to non-operative management:

1. Activity modification:

o Avoid aggravating activities (e.g., heavy lifting, overhead presses).

o Discontinue or reduce intensity of weight training.

2. NSAIDs:

o Reduce inflammation and pain (e.g., ibuprofen, naproxen).

3. Physical therapy:

o Focus on shoulder girdle stabilization and flexibility.

o Strengthening periscapular and rotator cuff muscles.

4. Ice and local modalities:

o Reduce inflammation post-activity.

5. Corticosteroid injection:

o Directly into the AC joint for temporary relief.

o Reserved for refractory cases.

B. Surgical (If conservative treatment fails >6 months)

1. Distal clavicle excision (Mumford procedure):

o Arthroscopic or open resection of 1–2 cm of the distal clavicle.

o Preserves the coracoclavicular ligaments to maintain stability.

o High success rate with return to full activity.

8. Prognosis

Good Prognosis with Early Diagnosis

· Conservative therapy is effective in the majority.

· Surgical outcomes are excellent when performed appropriately.

Return to Activity

· Conservative care: return within weeks to a few months.

· Post-surgery: full recovery in 3–6 months, depending on rehabilitation.

Potential Complications

· Persistent pain if untreated or misdiagnosed.

· Shoulder dysfunction due to chronic inflammation.

· Secondary AC joint arthritis.

· Recurrence if return to high-impact activity is premature.

Summary Table

Aspect	Details
Etiology	Repetitive microtrauma, weightlifting, overhead activity, trauma
Pathophysiology	Osteoclastic resorption of bone due to microtrauma and inflammation
Epidemiology	Young to middle-aged men, especially athletes and laborers
Symptoms	Shoulder pain, tenderness at AC joint, worse with cross-body movements
X-ray Findings	Distal clavicle resorption, joint space widening, cortical changes
MRI Findings	Marrow edema, joint effusion, soft tissue swelling
Treatment	Rest, NSAIDs, physical therapy, corticosteroids, distal clavicle excision
Prognosis	Excellent with appropriate treatment

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Case study: A 22-Year-Old Woman with Chronic Left Shoulder Pain

Early Osteoarthritis / Distal Clavicular Osteolysis Secondary to Trauma

History and Imaging

A 22-year-old woman presented with persistent left shoulder pain that began several months ago following a mechanical fall onto her left shoulder.
At the time of the fall, imaging showed no evidence of acute fracture, and she managed the pain with rest and acetaminophen.
However, her symptoms did not improve and the pain persisted, prompting further evaluation.
Physical examination revealed tenderness over the acromioclavicular (AC) joint, though range of motion was preserved and there were no signs suggestive of infection.
Radiographic imaging was subsequently performed.

Quiz 1:
Widening of the acromioclavicular (AC) joint space is indicative of a potential ligamentous injury.
(1) True
(2) False

Additional Imaging Findings:

No abnormalities were noted on standard radiographs.
Due to the chronicity of symptoms, magnetic resonance imaging (MRI) of the shoulder was subsequently performed.
Presented below is a proton density-weighted, fluid-sensitive sagittal image of the left shoulder.

Quiz 2

Fluid-sensitive signal within the acromioclavicular (AC) joint corresponds to red marrow, a common finding in young adults.
(1) True (2) False
A small amount of effusion is present within the AC joint.
(1) True (2) False
The majority of cases are attributed to a single, significant traumatic event.
(1) True (2) False

Findings and Diagnosis

Imaging Findings

Radiography:

No acute abnormalities were identified on standard radiographs. The acromioclavicular joint space was maintained, with no evidence of joint space narrowing, degenerative changes, or erosive lesions.

Magnetic Resonance Imaging (MRI):

MRI demonstrated more pronounced focal bone marrow edema within the distal clavicle compared to the acromion. Mild joint effusion and capsular edema were present. The articular surface of the AC joint was preserved, with no identifiable erosions.

Differential Diagnosis

In the Setting of Acute Trauma:

Distal clavicle fracture
Acromioclavicular ligament injury

In the Setting of Chronic Trauma:

Distal clavicular osteolysis
Early-onset osteoarthritis

In the Absence of Trauma:

Inflammatory arthropathy (e.g., rheumatoid arthritis or disorders of calcium metabolism)

Final Diagnosis

Early-stage osteoarthritis and/or distal clavicular osteolysis secondary to trauma

Discussion

Pathophysiology

Distal clavicular osteolysis (DCO) is an uncommon condition, and its exact pathogenesis is not fully understood. It is generally believed to result from repetitive microtrauma to the shoulder, particularly at the acromioclavicular joint, leading to a localized inflammatory response. Mechanical stress and repetitive traction forces contribute to osteopenia, subchondral erosion, and eventual bone resorption. This reparative process often leads to sclerosis and progressive degeneration of the joint. An alternative hypothesis proposes herniation of synovial tissue into subchondral bone as a trigger for an inflammatory cascade that promotes osteolysis. Both theories emphasize the role of chronic mechanical stress, although a single high-impact traumatic event may similarly initiate the process.

Epidemiology

DCO is most frequently reported in young, physically active individuals, particularly athletes. It exhibits a male predominance, likely due to higher participation in high-intensity activities such as weightlifting, which increase loading on the AC joint.

Clinical Presentation

Patients typically report localized, insidious-onset pain at the AC joint, exacerbated by activity. The pain is usually chronic but self-limiting. Physical examination findings are often non-specific, with preserved shoulder range of motion. Pain may be elicited with cross-body adduction testing.

Differential Considerations

In the context of acute trauma, differential diagnoses include distal clavicle fracture and acromioclavicular ligament injury. In chronic presentations, early osteoarthritis and DCO should be considered. In the absence of a clear traumatic history, findings of focal AC joint inflammation on MRI should prompt consideration of systemic inflammatory conditions such as rheumatoid arthritis or metabolic disorders affecting calcium homeostasis.

Imaging Characteristics

Early radiographs may appear normal. MRI typically demonstrates bone marrow edema predominantly within the distal clavicle, along with joint effusion and capsular thickening or enhancement. As the disease progresses, imaging may reveal distal clavicular erosions, joint space widening, and tapering or flattening of the distal clavicle. These findings—along with subchondral sclerosis and early degenerative changes—become increasingly evident on both MRI and plain radiography.

Management

Initial treatment is conservative, including nonsteroidal anti-inflammatory drugs (NSAIDs), physical therapy with emphasis on reducing repetitive AC joint loading, and corticosteroid injections. Surgical intervention, most commonly distal clavicle excision (Mumford procedure), is reserved for patients with persistent symptoms refractory to conservative measures.

References

Buss DD, Watts JD. Acromioclavicular injuries in the throwing athlete. Clin Sports Med. 2003;22(2):327–341.
Cahill BR. Osteolysis of the distal part of the clavicle in male athletes. J Bone Joint Surg Am. 1982;64(7):1053–1058.
DeFroda SF, Nacca C, Waryasz GR, Owens BD. Diagnosis and management of distal clavicle osteolysis. Orthopedics. 2017;40(2):119–124.
Hohmann E, Tetsworth K, Glatt V. Open versus arthroscopic acromioclavicular joint resection: a systematic review and meta-analysis. Arch Orthop Trauma Surg. 2019;139(5):685–694.