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Commentary on an article by Sebastien Parratte, MD, PhD, et al.: "Effect of postoperative mechanical axis alignment on the fifteen-year survival of modern, cemented total knee replacements".

It has been a long-held tenet of total knee replacement that the restoration of a neutral mechanical axis promotes improved durability and function following this surgery. Observational data from over ten series have led to this belief and have in fact been corroborated by in vitro testing, in which increased wear and premature failure of components can occur if the total knee replacements are mechanically aligned in a varus position1-14. This concept is further reinforced by the advances in computerized navigation and other imaging systems that aim for this “ideal” coronal plane alignment to enhance knee replacement survival rates.

The report by Parratte and associates entitled “Effect of Postoperative Mechanical Axis Alignment on the Fifteen-Year Survival of Modern, Cemented Total Knee Replacements” challenges these assertions by finding that total knee replacements placed outside of a few degrees from the mechanical axis in the coronal plane had equal survival rates when compared with knees placed within ±3° of the mechanical axis. The authors analyzed the fifteen-year survival for 398 primary total knee arthroplasties that had been performed with cement in 280 patients between 1985 and 1990. Patients were stratified into two groups: …