Which deformity is characterized by PIP hyperextension and DIP flexion?

The characterization of PIP hyperextension and DIP flexion is indeed indicative of Swan Neck deformity. This condition typically occurs due to an imbalance in the muscles and tendons surrounding the finger joints, often as a result of rheumatoid arthritis or other inflammatory conditions.

In Swan Neck deformity, the proximal interphalangeal (PIP) joint is hyperextended while the distal interphalangeal (DIP) joint is flexed. This position resembles the neck of a swan, hence the name. It results from the tightening of the intrinsic muscles and weakening of the volar plate or the palmar structures that normally stabilize the PIP joint.

Understanding the mechanics behind this deformity is crucial for treatment and management in orthotic and prosthetic practice, as it influences the type of immobilization or corrective devices that might be used to restore function or alleviate discomfort.