Acromioclavicular Joint Separation

What is acromioclavicular joint separation?

Acromioclavicular (AC) joint separation refers to an injury involving the separation of the acromion (part of the shoulder blade) from the clavicle (collarbone). This type of injury commonly occurs due to a direct blow to the shoulder or a fall onto an outstretched arm, leading to damage of the ligaments that stabilize the AC joint. AC joint separations are graded based on the severity of ligament damage, with higher grades indicating more significant separation and instability.

What are the causes of AC joint separation?

AC joint separations typically result from traumatic events, such as falls onto the shoulder or direct impact to the area. Common causes include sports-related injuries, motor vehicle accidents, or falls during recreational activities. The injury occurs when the force applied to the shoulder exceeds the strength of the ligaments supporting the AC joint, leading to ligament sprains or tears and subsequent separation of the acromion and clavicle.

What are the symptoms of AC joint separation?

Symptoms of AC joint separation may vary depending on the severity of the injury but commonly include:

1. Pain and tenderness over the AC joint, particularly with movement or pressure applied to the area.
2. Swelling and bruising around the shoulder joint, extending to the collarbone and upper arm.
3. Limited range of motion in the shoulder, especially with overhead movements or reaching across the body.
4. Visible deformity or prominence of the AC joint, with a noticeable bump or step-off compared to the unaffected side.
5. Weakness or instability in the shoulder, making it difficult to perform everyday activities or participate in sports.

How is AC joint separation diagnosed?

Dr. Shane J. Nho diagnoses AC joint separation through a comprehensive evaluation, including a combination of medical history assessment, physical examination, and imaging studies. The diagnosis aims to determine the severity of the injury and guide appropriate treatment strategies. Diagnostic steps may include:

Medical History

Reviewing the patient’s history for any recent trauma, falls, or sports-related injuries affecting the shoulder.

Physical Examination

A thorough examination of the shoulder joint to assess range of motion, stability, and signs of AC joint tenderness or deformity.

Imaging Studies

Imaging studies play a crucial role in diagnosing AC joint separation and assessing the extent of ligament damage. Common imaging modalities used in the diagnosis of AC joint separation include:

• X-rays: X-rays provide detailed images of the acromioclavicular joint and surrounding structures, allowing clinicians to assess for signs of separation, displacement, or bony abnormalities. X-rays are particularly useful for grading the severity of AC joint separations based on the amount of space between the acromion and clavicle.
• Magnetic Resonance Imaging (MRI): MRI is highly effective for evaluating soft tissue structures such as ligaments, tendons, and cartilage. It can help identify the extent of ligamentous injury, detect associated injuries such as rotator cuff tears or labral tears, and guide treatment planning for AC joint separation.
• Ultrasound: Ultrasound imaging may be used to assess the integrity of the AC joint ligaments and surrounding soft tissues. It can provide real-time visualization of the joint and help clinicians determine the severity of the injury, particularly in cases where MRI is contraindicated or unavailable.