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CORR Insights®: Are There Differences in Micromotion on Radiostereometric Analysis Between Bicruciate- and Cruciate-retaining Designs in TKA? A Randomized Controlled Trial

Nizard, Rémy S. MD, PhD

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Clinical Orthopaedics and Related Research: September 2020 - Volume 478 - Issue 9 - p 2054-2056
doi: 10.1097/CORR.0000000000001173

Where Are We Now?

While the modern TKA is a common procedure, poor functional results and high rates of residual symptoms [8] have encouraged surgeons to explore alternate surgical techniques. In my observation, some surgeons are more open to preserving both cruciate ligaments as a possible solution for several nagging issues surrounding knee kinematics, such as excessive posterior translation during flexion, paradoxical anterior translation during flexion, or excessive laxity. But from a technical standpoint, several aspects of the bicruciate TKA should be refined, including the fixation of the tibial component, which cannot rely on a central peg, and the reliability of the central bridge between the two tibial plateaus.

Our current knowledge on the clinical performance of bicruciate TKA needs to be improved, but we only have a limited number of patients and short-term follow-up. Indeed, a main theme from the several papers [1, 3, 7, 10, 12] that have examined modern bicruciate-retaining TKA is that the follow-up is extremely short, even though patients who have this procedure will need reliable long-term results. One short-term follow-up study of 146 TKAs using bicruciate-retaining implants showed promising patient-reported outcome findings, with 91% reporting that their knee always or sometimes felt normal [1]. These results support the idea that bicruciate-retaining implants are superior to traditional alternatives. However, two recent randomized trials found no clinically important differences between bicruciate-retaining TKAs and posterior cruciate ligament-substituting designs in ROM or knee scores [7, 12].

The goal of an arthroplasty is having the joint function like the original one. While THA can often accomplish this goal, we see this less frequently for TKA due, perhaps in part, to our patients’ knee kinematics. Keeping both cruciate ligaments intact during the arthroplasty may be a way to mimic the original knee’s kinematics. However, in the current study, Troelsen and colleagues [13] found no difference in Forgotten Joint Score between bicruciate- and posterior cruciate-retaining TKA. The authors emphasized that bicruciate-retaining TKA may be associated with new types of complications (such as tibial island fracture) and the uncertainties associated with new treatments, but this approach did not appear to be associated with any offsetting benefits to patients. For that reason, they recommended against widespread use of bicruciate-retaining TKA.

Where Do We Need To Go?

Different aspects of knee function like ACL function, knee kinematics, or knee laxity have been previously researched, but we still do not know which functions are the most important for patient success after TKA. While research has suggested that overtensioning the ACL during bicruciate-retaining TKA can result in limited ROM [9], other studies have differed about whether this procedure restores normal knee kinematics [2, 5]. We need to improve the methodology and results of these models before we can generalize bicruciate-retaining TKA for widespread clinical use. Considering the complications and high risk of early reoperation [13], as well the trial data showing no superiority in terms of ROM or patient-reported outcomes scores in patients treated with bicruciate-retaining TKA [7, 12], I believe we should not use these devices outside of IRB-approved clinical trials.

We still need to develop a consensus on the parameters that could define a successful implantation of bicruciate-retaining TKA. How should we define a successful implantation? Considering the complexity of the procedure, mechanical alignment guides and the ways in which we currently measure ligament balance should be more precise. Additionally, our implant devices likely need more-sophisticated instruments. Unfortunately, this will add to the cost of what may be an already-expensive implant (as new devices so often are). For this reason, once again, I don’t believe widespread use of bicruciate-retaining TKA is appropriate until or unless clinical research demonstrates important benefits that patients can perceive.

How Do We Get There?

Investigators should first determine the type of kinematics data to include in their future study on bicruciate-retaining TKA. Among the different methods of fluoroscopy, both two- and three-dimensional images have been used extensively. These images may be used as a reference since fluoroscopy is performed in vivo. Additionally, we could obtain a large amount of data on both normal knees and those who underwent TKAs, which could be used for comparison purposes. Another approach could be developing a preoperative kinematic analysis with navigation instruments with the goal of refining our surgical techniques and correlating the data with postoperative clinical data. In this case, the preoperative evaluation would be done passively in nonweight-bearing conditions.

If a future comparative kinematic study that is independent of commercial interests shows good results for bicruciate-retaining TKA, the next step would be developing high-quality randomized clinical trials. While normally these are prohibitively expensive, this may not be the case here; we may not need hundreds of patients per trial to get the answers we seek. If bicruciate-retaining TKA doesn’t offer improvements in patient-reported outcomes that are detectable in studies of modest size—such as that of Troelsen and colleagues [13], or perhaps slightly larger—it’s likely not to be an important enough innovation to justify our attention. To my knowledge, no study has suggested that bicruciate-retaining TKA is likely to improve survivorship (the question is mainly whether the opposite will occur). Therefore, we may not need long-term follow-up, which makes getting the evidence we seek that much easier. If bicruciate-retaining TKA doesn’t show important benefits early, we will have the answers we need.


1. Alnachoukati OK, Emerson RH, Diaz E, Ruchaud E, Ennin KA. Modern day bicruciate-retaining total knee arthroplasty: A short-term review of 146 knees. J Arthroplasty. 2018;33:2485-2490.
2. Arnout N, Victor J, Vermue H, Pringels L, Bellemans J, Verstraete M. Knee joint laxity is restored in a bi-cruciate retaining TKA-design. Knee Surg Sports Traumatology Arthrosc Official J Esska. 2019:1-9.
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        12. Scarvell JM, Perriman DM, Smith PN, Campbell DG, Bruce W, Nivbrant B. Total knee arthroplasty using bicruciate-stabilized or posterior-stabilized knee implants provided comparable outcomes at 2 years: A prospective, multicenter, randomized, controlled, clinical trial of patient outcomes. J Arthroplasty. 2017;32:3356-3363.
        13. Troelsen A, Ingelsrud LH, Thomsen MG, Muharemovic O, Otte KS, Husted H. Are there differences in micromotion on radiostereometric analysis between bicruciate and cruciate-retaining designs in TKA? A randomized controlled trial. Clin Orthop Relat Res. [Published online ahead of print December 3, 2019]. DOI: 10.1097/CORR.0000000000001077.
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