Comprehensive Osteopathic Medical Licensing Examination (COMLEX USA) Practice

Which test would most likely yield a positive result for unilateral sacral extension?

1. Seated flexion test

2. Spring test

3. Compression test

4. Visual observation

The correct answer is: Spring test

A positive result for unilateral sacral extension is typically assessed using specific tests that evaluate the motion and alignment of the sacrum. The spring test, in particular, is designed to assess the responsiveness of the sacrum to anterior-posterior pressure. When performing this test, if the sacrum is in an extended position, there will be decreased resistance to the force applied, resulting in a positive spring test. This occurs because the sacrum's position reduces its ability to spring back when pressure is applied. In contrast, other tests such as the seated flexion test focus on assessing asymmetries in the ilium and sacroiliac joint mechanics, while the compression test evaluates the stability of the sacroiliac joint. Visual observation provides only a qualitative assessment and may not reveal specific mechanical dysfunctions such as unilateral sacral extension. Therefore, the spring test is the most reliable method for identifying unilateral sacral extension among the options provided.