Surface variation analysis of proximal interphalangeal joint of osteoarthritis with fringe projection profilometry

The proximal interphalangeal joint (PIP) is the most important joint of the finger and is one of the most common joints to be affected by hand osteoarthritis (OA) due to excessive usage of the hand. PIP injury which may lead to osteoarthritis occurs when the protective cartilage on the boundaries of the joint begins to wear off or simply by a hyperextension of the joint. Currently, in order to diagnose joint deformity of the hand OA, particular imaging modalities namely the X-ray scanning and magnetic resonance imaging (MRI) is used but has its limitations such as radiation concerns and can be quite expensive. In this work, a fringe projection profilometry system which comprises of an LCD projector, CCD camera, and a personal computer has been developed to analyze surface changes of the PIP joint. The central concept of this optical metrology system is to apply structured light as imaging source for surface change detection. The imaging source utilizes fringe patterns generated by C++ programming and is shifted using the 3 steps 2 shift method for obtaining the phase map image. Grayscale analysis and pixel tracing were applied to detect the deformation of the PIP joint on a live individual. The result has demonstrated a successful method of PIP joint deformation detection based on the pixel tracking differences of a static and deformed state of the PIP joint.