Medical imaging of knee kinematics after joint replacement

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The primary reason for someone to get a knee replacement is to reduce his or her pain due to arthritis. Unfortunately, some people still have considerable pain after the surgery, often in the region of the kneecap (called anterior knee pain). Frequently this pain is attributed to incorrect tracking of the kneecap (patella) on the thigh bone (femur) due to improper component design, incorrect placement of the components, excessively tight soft tissues or poor surgical technique. Currently, the only method most surgeons use to 'look inside' the knee is X-rays, which are two-dimensional images at a single angle of knee flexion. These provide inadequate information to study the movements of the bones. We are proposing to develop a new method to measure the three-dimensional positions of both the bones and components after knee replacement surgery at different flexion angles, using computed tomography (CT). CT produces a 3D image of the patient's knees. The metal components create streaks on the image, making it difficult to identify the bones and components accurately, however we are proposing several ways to address this. We will validate the protocol using reference arrays inserted into cadaveric knee specimens. We will then apply the protocol to patients in order to judge whether or not a recent implant design improves kneecap motion; subsequently, we will compare patients with and without pain. In addition, and in contrast, to CT, we will develop a protocol for two-dimensional fluoroscopic imaging, which is dynamic (i.e. captures a video of movement), inexpensive, widely available and could be applied in