Engineers at the University of Bath in the United Kingdom have developed a new diagnostic test that detects loosened artificial hip implants. The test measures the frequency of sound produced when the femur bone in the leg is vibrated. The method is more sensitive than the conventional method of using x-rays, and can diagnose much smaller gaps around the hip joint.
The method places a piece of vibrating equipment on the patient's knee, and vibrates the femur and the hip joint. An ultrasound device is attached to the hip to pick up sound vibrations from the joint. If the sound's frequencies are pure, or regular, the joint is firmly fastened to the bone. If the sound waves are irregular, the joint has come loose.
It is estimated that within 10 years of having a hip implant, almost one quarter of patients will suffer pain from a loosening joint. The new test could save patients from undergoing unnecessary surgery.