CORR Insights®: Squeaking Is Common and Increases Over Time Among Patients With Long-term Follow-up After Ceramic-on-ceramic THA

Where Are We Now?

Taniguchi et al. [7] retrospectively studied a small series of young patients who were treated with ceramic-on-ceramic (CoC) THA implants. The implanted ceramic was a third-generation material known as Biolox® Forte (CeramTec, Plochingen, Germany). and the follow-up period was long (11-16 years) compared with the follow-up of many other reported series. The authors’ primary purposes were to analyze the frequency of squeaking noises arising from the prosthetic hip bearing and to determine whether it becomes more common over time. About one-third of their patients reported that squeaking developed more than 5 years after implantation, suggesting that squeaking increases with the service life of the implant. The authors also found that the femoral component’s design may play an important role in squeaking. They noted that squeaking was more common with the Accolade titanium-molybdenum-zirconium-iron (TMZF) stem (Stryker, Mahwah NJ, USA) than with the SecurFit (Stryker, Mahwah, NJ, USA).

As pointed out by the authors [7], interest in CoC implants primarily arises from the low wear rate and low biologic reactivity associated with this bearing surface. In fact, most reported series highlighted the excellent long-term survivorship and low incidence of osteolysis of CoC implants in young, active patients [1-3]. These studies also noted squeaking in 10% to 30% of patients and reported that squeaking is an important cause of revision. The source of squeaking of CoC THA implants is still being investigated, but it appears to be associated with issues unique to ceramic bearings, such as microseparation, edge loading, and stripe wear associated with the CoC bearing [4, 6]. Simulator studies and retrievals of explanted components indicate the problem of micro-separation between the head and acetabulum during gait, causing edge loading that induces wear [4, 6]. This is associated with stripe wear, but stripe wear is also associated with metal transfer to the femoral head [4]. Surface roughness is increased in places where there is stripe wear, and this increased roughness may result in vibrations that cause squeaking [6]. Much of our understanding of the CoC bearing comes from simulator studies, and long-term clinical follow-up is lacking to date.

Taniguchi et al.’s paper [7] is important because it provides long-term clinical data and highlights the possible influence of the femoral component in squeaking. In this series [7], the Accolade TMZF stem (Stryker) was associated with a higher incidence of squeaking than the SecurFit stem (Stryker) was. This titanium alloy is associated with substantial trunnion corrosion and has been recalled from clinical use, suggesting that corrosion plays a role in generating stripe wear and squeaking.

Where Do We Need To Go?

As pointed out by the authors [7], the phenomenon and cause of squeaking of CoC implants have been reported, but much of what is known comes from simulator studies, with little information derived from long-term clinical studies. Future long-term studies should seek to deliver more-precise information regarding the incidence of squeaking and how it affects the likelihood of revision as well as patient satisfaction. The influence of ceramic composition and the metallurgy and design of the femoral component are not fully understood and also need further investigation. The influence of femoral head size and the role of impingement between the femoral neck and acetabulum are also not well-known and need to be studied. In my opinion, simulator studies provide important insights into the tribiology of component design choices, but long-term clinical follow-up is mandatory to better understand the performance of implants.

How Do We Get There?

The limitations of Taniguchi et al.’s study [7] can help to inform future clinical studies regarding this topic. In this series, three femoral stem designs were used, adding to the number of variables to be analyzed. Future studies should attempt to limit difficult-to-control variability. This inherent weakness of retrospective studies could be avoided by well-designed prospective studies. Such studies can be designed and performed at centers that perform a high volume of CoC THAs. The advantage of a prospective study design is that the investigators can agree on important surgical variables such as the approach, prosthetic choice, and clinical pathways used for perioperative care before patients are recruited. Because all patients are entered into the study at the same stage of care, it is easier to avoid bias and control the collection of data that are critical to address the study aims and purposes. Large registries of countries that have high use of CoC implants, such as Australia [5], could also be a source of valuable data to address this issue. The Australian registry has recorded nearly 17,000 CoC THAs in its database, which can be mined to address specific variables associated with squeaking [5].

Perhaps most importantly, there must be a real effort to study explanted and retrieved components, whenever possible. Retrieval studies provide a detailed examination of the effects of wear and component impingement. When analyzed along with clinical data such as patient demographics, BMI, component positioning, activity level, and patient-reported outcome measurements, there is tremendous potential to gain the critical understanding needed to find solutions to the many open and unresolved questions regarding THA.