My sister had a total hip replacement and ended up with a squeaky joint that can’t be oiled to get rid of the sound. I’m going to have a hip replacement, too. Should I ask for a different kind of implant? Her’s is made of ceramic. I understand there are titanium implants available, too.

An investigation at the Thomas Jefferson University Hospital in Philadelphia, Pennsylvania might just have an answer to that question. They compared results for patients receiving two different designs of a ceramic-on-ceramic implant.

Group one got an implant that had a special coating on the stem made of a titanium-aluminum-vanadium alloy. The stem was shaped with a C-taper neck and had a wide, thick midsection. The stem portion of a hip replacement fits down inside the long shaft of the femur (thigh bone). Group two was given an implant with a stem made of a different combination of metals: titanium-molybdenum-zirconium-iron alloy. The design was a V-shape instead of a C-shape and the midsection wasn’t as thick as in group one.

Statistical analysis showed that patients with the thinner V-shaped neck and titanium-molybdenum-zirconium-iron stem were seven times more likely to develop a squeak. This stem is more flexible with a lower frequency of resonance. Vibrations created by the ceramic-on-ceramic movement are amplified (made louder) when there’s a lower frequency. And evidently, the oscillations can be amplified enough to generate a sound that can be heard.

The authors concluded by saying patients don’t have to give up the good quality of motion provided by ceramic-on-ceramic hip replacements. Surgeons just have to avoid using implants with the V-40 neck and choose the stiffer, C-taper stem instead. They should also make sure the materials are not made of the titanium-molybdenum-zirconium-iron alloy.