Acromioclavicular Shear Test

The Acromioclavicular Shear Test, also known as the AC Joint Compression Test, is a valuable orthopedic examination technique used to evaluate the integrity of the acromioclavicular joint and diagnose potential pathologies. This diagnostic maneuver serves as an essential tool in the clinical assessment of shoulder injuries and conditions affecting the AC joint.

Clinical Significance

The AC joint represents a crucial articulation between the acromion process of the scapula and the lateral end of the clavicle. This synovial joint plays a vital role in shoulder biomechanics and upper extremity function. The AC Shear Test specifically targets this joint to identify various pathological conditions, including AC joint separations, osteoarthritis, osteolysis, and post-traumatic injuries.

How to Perform the AC shear test?

The examination begins with proper patient positioning. The patient should be seated comfortably, allowing full access to the shoulder complex. The examiner positions themselves behind or beside the patient to perform the test accurately.

The technique involves several precise steps: The examiner places both hands over the patient’s deltoid muscle region. One hand is positioned specifically on the clavicle, while the other hand rests on the spine of the scapula. The examiner then applies a compressive force by squeezing their hands together, creating a shearing stress across the AC joint.

See Also: AC Joint Separation

Interpretation of Results

A positive AC shear test is indicated by two primary findings: abnormal movement at the AC joint and pain reproduction. The presence of excessive translation or movement during compression suggests compromised joint stability. Pain localized to the AC joint during the maneuver further supports the diagnosis of AC joint pathology.

Clinical Correlation

The AC Shear Test should not be interpreted in isolation. Clinical correlation with patient history, mechanism of injury, and other physical examination findings is essential for accurate diagnosis. Medical professionals should consider incorporating additional tests such as the Cross-Body Adduction Test and O’Brien’s Test to establish a comprehensive clinical picture.

Diagnostic Accuracy

The Acromioclavicular Shear Test demonstrates good specificity for AC joint pathology, particularly when combined with other clinical tests. However, medical professionals should be aware that false positives can occur in cases of severe deltoid tenderness or concurrent shoulder pathologies.

Differential Diagnosis

When evaluating AC joint complaints, several conditions should be considered in the differential diagnosis: AC joint separation (Grades I-VI), degenerative joint disease, distal clavicular osteolysis, and post-traumatic arthritis. The AC Shear Test helps differentiate these conditions and guides appropriate management strategies.

Clinical Management Implications

Test results significantly influence treatment decisions. Positive findings may indicate the need for further imaging studies, such as radiographs or MRI, particularly in acute trauma cases. Treatment options range from conservative management with activity modification and physical therapy to surgical intervention in severe cases.

Resources and References

1. Journal of Shoulder and Elbow Surgery: https://www.jshoulderelbow.org
2. American Academy of Orthopaedic Surgeons: https://www.aaos.org
3. Orthopedic Physical Assessment by David J. Magee, 7th Edition.
4. Davies GJ, Gould JA, Larson RL. Functional examination of the shoulder girdle. Phys Sports Med. 1981;9:82–104.