Final answer:
The question inquires about SIJ tests for shear force that are not commonly performed. Two such tests are the SIJ compression test and the SIJ distraction test; however, they are not usually named based on shear forces like the shear modulus formula suggests.
Step-by-step explanation:
The student is asking about two special tests for the sacroiliac joint (SIJ), specifically assessing shear force, that are not typically performed. In the context of physical therapy or orthopedic assessments, these tests could be designed to apply or resist shear forces to the SIJ to evaluate its integrity or pain response. However, it's important to note that the shear modulus formula provided, where S is the shear modulus and F is the force applied perpendicular to Lo (initial length) and parallel to the cross-sectional area A, is related to materials science and physics, and does not directly correlate to the clinical SIJ tests which are not typically named based on mechanical properties like shear modulus.
Two SIJ tests that involve shear force but are not common might be the SIJ compression test and the SIJ distraction test (also known as the gapping test). These tests assess whether shear force across the joint provokes pain or reproduces symptoms, suggesting SIJ dysfunction. The SIJ compression test involves applying a downward force on the anterior superior iliac spine, compressing the SIJs, while the SIJ distraction test applies lateral pressure to the iliac crests, attempting to 'gap' the SIJs. Both could reflect shear forces acting on the SIJ but are less commonly referred to as shear tests in clinical practice.