Incidence of Hip Squeaking After Replacement is UnderreportedImagine you are late arriving at a very quiet function. You attempt to sneak into the back row but the only seats left are in the front. Every time you take a step, there is an audible pop, squeak, or grinding sound. The noise is coming from your new hip replacement. The results of this study show that 10 per cent of the adults who get a ceramic-on-ceramic implant will end up with a noise of this type.
Three surgeons from Lenox Hill Hospital in New York City pooled their patients together to study this problem. They compared a group of patients who got a ceramic-on-ceramic bearing implant with a control group who got a metal-on-plastic (chromium-cobalt-on-polyethylene) bearing. The control group was matched to the ceramic-on-ceramic group using a computer database. Matching criteria included age, sex, body mass index, and whether or not they had one or both hips replaced.
All patients (regardless of implant type) were tested before and after surgery using a variety of test measures. X-rays were used along with several surveys of questions about daily function, satisfaction, range-of-motion, pain, and walking ability. In addition, patients were asked directly, Does your hip make a noise? The questionnaires were filled out three months after surgery and again at six months, and 12 months. Patients included in the study had at least one full year of follow-up.
The authors were interested in finding out how often the noise occurred in their ceramic-on-ceramic patients and how that compared to patients getting a different kind of implant. They also wanted to see if they could figure out what was causing the noise. The hip X-rays were analyzed for angles and position of both sides of the implant (cup or socket and femoral head or ball that fits into the socket). Any changes in leg length from one side to the other were also recorded.
They found that although less than one per cent of the ceramic-on-ceramic patients ever complained of noises, when specifically asked about it, 10 per cent reported noises of some kind. The metal-on-plastic group was more likely to report a clicking noise rather than a squeak. The incidence was much less (four per cent) in the metal-on-polyethylene group. Squeaking was the most common noise for the ceramic group, but some patients described the noises as popping, snapping, or grinding.
There was no pain associated with the noises. Most of the time, the squeak or other noise occurred once a day or less. Sometimes it only occurred once a week. But for those who had daily squeaking, it had a negative effect on their quality of life. One person who had hip squeaking and chronic hip dislocations gave their results as completely unsatisfactory.
Activities linked with the noises included bending and walking (most common), but also climbing stairs, exercising, during sexual activity, and when putting on pants. Some of the patients could reproduce the noise by stepping up on a low stool. The authors called this the squeak test. Evidently, combining a flexion-to-extension movement of the hip with a weight-bearing load was enough to recreate the problem.
When trying to determine the cause of the squeaking, there were no differences in X-ray findings between those patients with noises and those without noises. They compared sizes of the replacement femoral head to see if that might be linked with noises -- it wasn't.
Since the patients didn't report noises until six months after getting the implant, it's possible some kind of wear is the cause of the squeak. In a previously published study, stripe wear was proposed as the possible source of the noise. Squeaking implants retrieved and inspected showed a broad stripe of wear on the femoral head with a matching wear pattern in the socket.
Other experts have also noticed this squeaking or other noises with implants of various materials. A variety of possible causes have been proposed including impingement, a mismatch of bearing surfaces, inefficient lubrication, or metal debris (flakes of metal from the implant get lodged inside the joint).
The authors make note of the fact that over the years, many changes have been made in the design of the ceramic liner that was used in this study. A metal backing with an elevated rim was added to protect from impingement, chipping, and fracture (previously observed complications). It's not likely that impingement is the cause of the current noises because impingement usually occurs at the end range of motion, not in the middle of a movement.
They will continue to use ceramic-on-ceramic implants for young, active patients. But until the source of the noises can be found and corrected, it will be necessary to inform patients ahead of time that this could be a potential complication of the ceramic implant. If the squeaking does develop, a revision surgery can be done. The implant can be removed and replaced with a metal-on-polyethylene or ceramic-on-polyethylene type of articulation.
Christopher A. Jarrett, MD, et al. The Squeaking Hip: A Phenomenon of Ceramic-on-Ceramic Total Hip Arthroplasty. In The Journal of Bone and Joint Surgery. June 2009. Vol. 91A. No. 6. Pp. 1344-1349.
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