Experimental Observation of Amplitude-and Phase-Modulated Responses of Two Internally Coupled Oscillators to a Harmonic Excitation

An experiment is performed on a two degree-of

Computer-Aided Acoustical Simulation of Pathological Knee Joints, Part I: in vitro

Previous studies have shown that different pathological knee joints produce unique acoustical characteristics.In‐vitro simulation of acoustical signature was attempted using bovine knee joints placed in a “flexing” machine. Mechanical destruction was induced on the articular cartilage surface, and the noise produced during rubbing was picked up by a sensitive condensermicrophone, amplified, recorded, and converted into digital form. A computer program was written to perform various statistical analysis. Cartilage surface roughness was measured with a profilometer and a spatial waveform roughness distribution curve was plotted out. Preliminary results show that the unique acoustical characteristics of the various knee‐joint diseases can be simulated fairly well with this technique. This study therefore provides a rough diagnostic indication of the degree of roughness of the various types of knee‐joint diseases. [Work supported by NIH.] © 1976 Acoustical Society of Americ

Possible Clinical Application of a Noninvasive Monitoring Technique of Cartilage Damage in Pathological Knee Joints

Arthritis and other related joint disorders are, today, the most common nonfatal crippling diseases. In every case these joint diseases involve progressive destruction of the articular cartilage. At present, there is no available noninvasive clinical tool which will permit on-going objective evaluation of the relative degree of damage to the articular cartilage. The recently developed computer-aided, electro-acoustical technique, utilizing the acoustic energy emitted by the joint during active articulation, appears to be a promising noninvasive clinical tool. The recent addition of a three-dimensional spectral history plot graphically presents the extent and location of cartilage in a clinically related form

Computer-Aided Acoustical Simulation of Pathological Knee Joints, Part II: in vivo

Suitable models of pathological knee‐joint diseases were created on rabbits using biological‐surgical techniques. At regular intervals during the progress of the disease, acoustical signatures were retrieved during flexion and extension of the knee joints. The noise was recorded on tape and digitized using an A/D converter. With the use of an IBM computer various statistical analysis were performed. The rabbits were sacrificed at regular intervals during the experiment and the roughness measured with a profilometer. The spatial waveform was recorded and statistically analyzed. Preliminary results showed that close correlation exists between the degree of roughness of the “diseased” cartilage and the acoustical signature emitted. This study verifies the strong correlation between the knee‐joint cartilage pathological condition and the acoustical noise emitted during extension and flexion. [Work supported by NIH.] © 1976 Acoustical Society of Americ