Page 40 - ISAKOS 2020 Newsletter Volume 2

CURRENT CONCEPTS
Calipered Kinematic Alignment for Total Knee Arthroplasty
Benefits from Performing Calipered Kinematic Alignment
One convincing test for learning the benefits of calipered kinematic alignment is to use the technique for patients who have had a previous mechanically aligned TKA in the contralateral limb. In a study of 78 patients with a previous mechanically aligned TKA in the contralateral limb, my colleagues and I reported a 15-point higher Forgotten Joint Score in the knee with the calipered kinematically aligned TKA and found that the favorite and fastest recovering knee was more often than not the one with kinematic alignment5. In my opinion, the calipered technique, which relies on millimeter measurements and verification checks for restoring the native or pre-arthritic joint lines, is more reproducible than the use of robotics, navigation, and patient-specific instrumentation for achieving a mechanical axis for the limb.
Commentary
David A. Parker, MBBS,
BMedSc, FRACS
Sydney Orthopaedic Research Institute, University of Sydney
Sydney, AUSTRALIA
I read with great interest the article by Dr. Stephen Howell regarding “Calipered Kinematic Alignment” in TKA. Dr. Howell has been a passionate advocate of this technique for many years, and his article very nicely outlines the theoretical basis for this technique and supporting basic-science evidence. More importantly, he has personally taken this theoretical concept and successfully studied its practical application in several studies over many years. There is no doubt that the increased interest and enthusiasm for this technique around the world has been in no small part due to Dr. Howell’s research, presentations, and publications in this area. The conclusion, as stated in the title, is that this technique is what you should use “when you want the best result.” The main question at this stage is whether, based on a critical review of all available evidence, this conclusion is the unequivocal message, or, alternatively, whether we need to continue good-quality research and debate around alignment strategies in TKR?
38 ISAKOS NEWSLETTER 2020: VOLUME II
REFERENCES
1. Nedopil AJ, Singh AK, Howell SM, Hull ML. Does Calipered Kinematically Aligned TKA Restore Native Left to Right Symmetry of the Lower Limb and Improve Function? J Arthroplasty. 2018;33: 398- 406. 2. Shelton TJ, Howell SM, Hull ML. Is There a Force Target That Predicts Early Patient-reported Outcomes After Kinematically Aligned TKA? Clin Orthop Relat Res. 2019;477: 1200-07. 3. Howell SM, Shelton TJ, Hull ML. Implant Survival and Function Ten Years After Kinematically Aligned Total Knee Arthroplasty. J Arthroplasty. 2018;33: 3678-84. 4. Nedopil AJ, Howell SM, Hull ML. What mechanisms are associated with tibial component failure after kinematically-aligned total knee arthroplasty? Int Orthop. 2017;41: 1561-69. 5. Shelton TJ, Gill M, Athwal G, Howell SM, Hull ML. Outcomes in Patients with a Calipered Kinematically Aligned TKA That Already Had a Contralateral Mechanically Aligned TKA. J Knee Surg. 2019.
Dr. Howell is a Consultant for Medacta and receives royalties for Intellectual Property.
All scientists understand the principle of skepticism toward new ideas, the fundamental principle being that the onus is on the proposer to provide good-quality evidence for the idea before the skepticism can be erased. The challenge is finding the right balance between (1) remaining skeptical in the face of overwhelming evidence and (2) letting one’s enthusiasm for an idea subtly remove the need for ongoing skepticism. In this case, I believe that a good deal of the original skepticism and concern around kinematic alignment (KA) has been reduced by good research, much of which has been done by Dr. Howell, but I do not personally believe that the level of evidence has reached the point of being unequivocal.
We all tend to selectively find and review literature in a way that supports our theories. Dr. Howell reports that 6 of 8 trials showed better results with KA and states that the 2 studies that did not demonstrate favorable results had “adulterated” the testing of KA. That assessment may seem a bit harsh to the relevant authors, whereas authors who reported favorable results seem to have been treated somewhat less harshly. A closer examination of the conclusions of the latter articles indicates that they certainly are not unequivocally in favor of KA. Callies et al. found better overall results in association with KA but also reported more outliers with poor outcomes in the KA group. Niki et al. found better functional scores in association with KA but did not report improved patient satisfaction. McEwen et al., in a bilateral study, found that more patients preferred the knee on the KA side but also found that half of the patients actually had no preference.