CORR Insights®: Is Cemented or Cementless Femoral Stem Fixation More Durable in Patients Older Than 75 Years of Age? A Comparison of the Best-performing Stems

Where Are We Now?

The use of cement has been one of the longest-lasting and most contentious issues over the history of modern THA surgery. Initially advocated by Sir John Charnley, it was later condemned by eminent researchers, as it was thought to be the cause of fixation failures and osteolysis [4]. In the 1990s, a variety of cementless (mainly porous-coated) femoral components were introduced and embraced by the majority of US surgeons. At the same time, cemented femoral fixation continued to be favored outside the United States in places like Great Britain and the Nordic countries, leading to a “North Atlantic Divide”, which persisted until the mid-2000s [1].

A turning point emerged around the mid-2000s toward increasing use of cementless femoral fixation in Europe. A study on national registry data from seven countries revealed the greatest absolute increases were recorded in England, Wales, and Denmark [16]. Although historically advocated mainly for younger patients [4], cementless fixation had been increasing in the elderly, despite cemented THA being associated with lower revision rates [16].

The current work by Tanzer and colleagues [13] draws data from the Australian Joint Replacement Registry to further examine this “uncemented paradox” [16], focusing on the femoral side and on patients older than 75 years of age. In their study, the authors reduced residual confounding by comparing the survivorship of only the best three cementless and cemented stems and by limiting the bearing surface used to crosslinked polyethylene. They demonstrated that patients receiving a cementless implant were, overall, more likely to undergo a revision for fracture and loosening during the first 3 postoperative months. This difference was most pronounced in patients treated for femoral neck fracture, for whom dislocation was an additional cause of early revision. At final followup, however, the two types of stems performed equally well.

This work conveys an important message about the practice patterns employed in THA surgery, one of the most common procedures in orthopaedics [6]. By joining forces with voices of the recent past [1, 9, 15, 16], the current study shows that cementless femoral fixation in older patients may be less innocuous than generally thought. On the other hand, the authors correctly noted that their findings applied to only the first few months after implantation. This is in contrast to previous registry research demonstrating an inferior performance of cementless stems in the older age groups in the long-term [16]. Clearly, there is room for further investigation in this subject.

Where Do We Need To Go?

There is a learning curve in all surgical procedures and implantation of a cementless femoral component should be no exception, even in the hands of expert hip surgeons [7]. The increased rates of mechanical loosening of cementless femoral components within 1 month from surgery reported in the current study represents an interesting conundrum. Osseointegration of cementless stems normally takes 4 to 12 weeks [5] and it seems that for patients in the current study, the stems were inserted loose in the first place and osseointegration never actually occurred. This is consistent with the landmark work by Noble and colleagues [10], which identified 45 different “somatypes” (that is, unique canal shapes) in a group of 200 femurs sampled, and that the distal and proximal dimensions of the medullary canal correlated poorly. Combine this with the widened diaphyseal canal that is commonly present in older patients [10], particularly females [11], and it is easy to imagine that less-experienced or lower-volume surgeons might have difficulty inserting a cementless stem tightly, without fracturing the femur, in some older patients. Increased micromotion at the bone-implant interface leads to fibrous encapsulation of the implant rather than osseointegration, and such stems are more likely to be painful or to become loose [10]. Put in this context, I agree with the authors of the current study regarding the importance of surgical experience on the longevity of such implants, and it is an area we need to examine further.

In their study, Tanzer and colleagues [13] selected the best-performing stems on the basis of not only the lowest revision rates at 10 years, but also of volume of use. It is conceivable that some of the more modern implants have been excluded solely due to limited usage time. This applies mostly to the tapered, low-profile cementless stems, which are generally preferred. None of the components examined by the authors of the current study fit this improved design geometry, which will have to be evaluated in future registry-based studies.

The present work highlights dislocation as a cause for increased early revision rates in patients undergoing THA for fracture, but not for osteoarthritis. The anteversion of a cementless stem is predominantly confined by that of the native femoral neck, whereas the surgeon has a little more discretion in terms of anteversion when implanting a cemented stem; this may reduce the risk of dislocation, although to this point, no studies have proven this point. The authors do not report on the surgical approaches used in each patient group, and I wonder whether their findings are more related to the type of stem fixation itself or to the use of a posterior surgical approach?

We need to study whether the preferential use of cementless implants happens, as is often suggested [1, 15], because surgeons tend to embrace newly released technology all too easily. My everyday experience dictates that other factors (training, discouragement of cement use by some anaesthesiologists) may also influence such decisions. The purported advantages [9, 14] and reported lower revision risk in older patients [16] of cemented stem fixation should be weighed against the documented potential for cement-related complications [3].

How Do We Get There?

Registry-based surveillance of implant performance at nationwide levels is an increasingly recognized necessity [8]. In the future, registry data should be used to investigate the performance of newer implants that are currently in the market. It is also important to consider the raw data of individual registries, when possible. By doing so, one could perform analyses on confounders (such as surgical approach) that were excluded from the annual registry reports [16]. And we still need corresponding findings describing the US experience of long-held preferential use of cementless implants, derived from the relatively recently established American Joint Replacement Registry [2].

Large-scale cohort studies based on institutional or regional outcome databases may serve as an alternative to registries, enabling researchers to more easily control for different variables. For instance, the inverse relation between surgical volume and complication rates has been demonstrated for THA [12]. To my knowledge, we have not yet addressed the relationship between fixation type and complications with such a study design. Well-matched retrospective, comparative cohort studies of prospectively collected data among surgeons with similar surgical experiences, but different preferences as to the type of femoral fixation (cemented vs. cementless), might provide some of the answers that we seek. Alternatively, the design may be modified to investigate early revision rates of cementless stems while controlling for surgeon volume (surgeons with different surgical volume matched for, among other confounders, implants used). Inclusion of patient-reported outcome measures would also provide us with outcome perspectives different to those usually given by registries using revision surgery as an endpoint.

Although not definitive, the evidence so far is strong enough to prompt a deeper look into the growing use of cementless femoral components. Appropriately developed questionnaire-based surveys of surgeons may help elucidate the reasons behind this phenomenon and may indicate possible methods to reverse it, such as by refining our training methods.

In my view, cementless stems are tempting because they are quicker procedures. But sound research from the authors of the current study, as well as by others [16], suggest that cementless stems are not superior and, in fact, may be inferior, to their cemented counterparts. Until we know more, the concerns expressed by these investigators should be taken seriously.