B Masson (Toulouse)
The issue of noise generation by the components implanted in total hip replacements has recently received a great deal of attention. Articulation noises have been associated with all types of bearing combinations including metal or ceramic on polyethylene and metal-on-metal as well.
There are several types of noises or sounds that can be emanated from the operated hip area. These noises can be transient particularly in the early rehabilitation period as the muscles and tissues around the implants heal. In addition there are reports of longer lasting component generated noises such as squeaking. Noises are reported from all kinds of bearings (Huo (2006), Willert (2005), Simon (1998), Bono (1994)), even though they are more common in hard-on-hard bearings. The percentage of reported squeaking is varying greatly, from 0.6 % reported by Walter (2007) up to 21 % published by Keurentjes (2008). This is mainly due to the different definitions of the squeaking noise given by the authors. Restrepo (2008) describes it as a “high-pitched noise” whereas Keurentjes (2008) summarizes different types of noises, defined as a reproducible sound of squeaking, clicking, or grating, as squeaking. Toni (2006) described noises as being a grinding sounds likely due to third particle wear. In some publications this is referred to as squeaking (e. g. Ranawat 2007, Keurentjes 2008). Therefore, it is important to differentiate between the types of noises that emanate from a hip. The authors suggest that a classification of hip emanating noises should be developed in order to assess the main influencing factors of the different noise types which may facilitate prevention and/or treatment.
The results of the investigations conducted by the group of surgeons from Australia clearly suggest that the cause of Total Hip Replacement noise following hip surgery is multi-factorial. Patient related factors such as muscle laxity, height, weight and other factors can be contributing factors. Surgical related issues such as placement of the implants and bone or tissue impingement are also found to be important factors. Finally, component design features such as the femoral stem neck geometry and implant range of motion without mechanical impingement can also be the causative factors leading to articulation noise1.
The noise described as “squeaking” on ceramic on ceramic systems is actually a titanium metal noise emanating from the vibration of the system’s metal components.
Testing suggest that there must be a relative motion and contact between the stem and the acetabular components in order to create articulation noise. The two most common factors for this kind of motion are component or soft tissue impingement and laxity of the joint following surgery. This can create a source for metallic debris to find its way into the articulating surface increasing the coefficient of friction and generating vibrational energy.
There is no data available that indicates that one type of THR noise, such as squeaking, compromises the mechanical integrity and clinical longevity of the implanted system.
Several IDE studies from the US as well as studies from outside the US clearly demonstrate the high survivorship and patient satisfaction of Total Hip Replacement using the ceramic on ceramic articulation and most importantly for the young and active patients almost no osteolysis has been reported with follow ups nearing the 12 year mark in some controlled clinical studies.