This randomized controlled trial compared functional alignment (FA) versus mechanical alignment (MA) in robotic-assisted total knee arthroplasty. Both groups used the same implant and robotic platform, differing only in alignment philosophy and balancing method. The primary outcome was the 2-year Forgotten Joint Score.
The practical lesson is that phenotype, not dogma, should guide alignment strategy. For the average patient, FA and MA deliver equivalent 2-year function, so neither is clearly superior across the board. This mirrors prior KA-versus-MA trials that failed to show a consistent winner.
The payoff appears in constitutionally varus (CPAK Type I) knees, where forcing a neutral mechanical axis deviates most from native anatomy. Here FA produced a clinically meaningful FJS advantage above the 14-point MCID. FA also nearly eliminated the need for MCL and PCL releases, which is mechanistically attractive: you adjust component position rather than destabilize ligaments.
Keep the unresolved question in mind. FA deliberately accepts residual varus (tibia averaged 2.7° more varus), and varus tibial alignment increases implant-bone interface load. With only 2-year follow-up, the long-term survivorship implications of these alignment boundaries remain debated.
This randomized controlled trial compared functional alignment (FA) versus mechanical alignment (MA) in robotic-assisted total knee arthroplasty. Both groups used the same implant and robotic platform, differing only in alignment philosophy and balancing method. The primary outcome was the 2-year Forgotten Joint Score.
The practical lesson is that phenotype, not dogma, should guide alignment strategy. For the average patient, FA and MA deliver equivalent 2-year function, so neither is clearly superior across the board. This mirrors prior KA-versus-MA trials that failed to show a consistent winner.
The payoff appears in constitutionally varus (CPAK Type I) knees, where forcing a neutral mechanical axis deviates most from native anatomy. Here FA produced a clinically meaningful FJS advantage above the 14-point MCID. FA also nearly eliminated the need for MCL and PCL releases, which is mechanistically attractive: you adjust component position rather than destabilize ligaments.
Keep the unresolved question in mind. FA deliberately accepts residual varus (tibia averaged 2.7° more varus), and varus tibial alignment increases implant-bone interface load. With only 2-year follow-up, the long-term survivorship implications of these alignment boundaries remain debated.