The analysis of hip joint vibrations (phonoarthrography, vibration arthrometry, vibroarthrography, hip auscultation) has been explored as a means to assess joint pathologies, disease status and recently, incipient prosthesis failure. Frequencies < 100Hz have been used to diagnose gross pathology and wear in knee prostheses, frequencies from 1k to 10k Hz for progression of osteoarthritis, and frequencies > 10k Hz for loosening of cemented hip prostheses. It is possible that detailed analysis of higher frequencies could detect and quantify the smaller geometric changes (asperities) that develop in articular prosthetic wear.

We examined the ultrasound emission generated by various types of hip prostheses and native hips of 98 patients. The ultrasonic transducer was attached to the skin over the greater trochanter with a hypoallergenic, transparent dressing using a standard acoustic coupling gel layer on the microphone face to improve skin contact. The transducer was attached by a 2m cord to a battery operated, data recorder/logger. The patients were asked to sit in a chair, rise, sit again and then rise and take 5 steps while recording the acoustic data from these two movements of sitting and walking. This procedure was repeated for the opposite hip in each patient as well. Acoustic emission analysis examined frequency distributions and power spectrums of the recorded signals and their relations to prosthesis type and implantation time. Review of x-rays of prosthetic and native hips was carried out with OA grading and prosthetic wear quantification.

We have obtained data on 79 metal-polyethylene (average duration of 8.5 years; 0.1–28), 20 ceramic-ceramic (average duration of 8.5 years; 0.5–10), 17 metal-metal (average duration of 1.2 years; 0.1–5.5) and 15 ceramic-polyethylene (average duration of 0.6 years; 0.1–1) hip arthroplasties as well as 75 native hips.

Analysis of the data enabled us to tell the difference between patients whose native hips did not cause them any discomfort and those patients with painful osteoarthritis (initial findings indicate that OA severity can be quantified as well). The measurements of wear of the metal-polyethylene prostheses obtained from patients’ x-rays were compared to an analysis of the ultrasonic emissions, a homogeneity showed no significant differences (all p’s > 0.24) between the curve type and amount of wear of the prosthesis polyethylene.

Our data suggests that we are capable of assessing the status of OA by acoustic emission. Further analysis of wear data coupled to ultrasonic emission is needed for accurate quantification of THA wear.