This retrospective study of 398 cemented TKAs tested whether achieving the traditional 0° ± 3° mechanical axis target actually improves 15-year implant survival. It directly examines the premise used to justify computer navigation in TKA.
The 0° ± 3° mechanical axis target has been taught as a cornerstone of TKA technique for decades, and the entire value proposition of computer navigation was built on reducing outliers beyond that threshold. This paper tests that premise directly — with full-length hip-knee-ankle radiographs, 15-year follow-up, and a sample large enough to detect a clinically meaningful difference if one existed.
In practice, this means your navigation decision should not hinge on chasing the 0° ± 3° target alone. When counseling patients or selecting instrumentation, the data support prioritizing BMI optimization and age-appropriate implant selection over expensive navigation solely to reduce alignment outliers.
This paper also set the stage for kinematic alignment as an alternative philosophy. If neutral mechanical alignment does not reliably improve survival, patient-specific alignment targets become a legitimate next question. The authors themselves note that the 0° ± 3° target remains a reasonable default until better individualized data exist, so do not abandon it. Just do not oversell it.
This retrospective study of 398 cemented TKAs tested whether achieving the traditional 0° ± 3° mechanical axis target actually improves 15-year implant survival. It directly examines the premise used to justify computer navigation in TKA.
The 0° ± 3° mechanical axis target has been taught as a cornerstone of TKA technique for decades, and the entire value proposition of computer navigation was built on reducing outliers beyond that threshold. This paper tests that premise directly — with full-length hip-knee-ankle radiographs, 15-year follow-up, and a sample large enough to detect a clinically meaningful difference if one existed.
In practice, this means your navigation decision should not hinge on chasing the 0° ± 3° target alone. When counseling patients or selecting instrumentation, the data support prioritizing BMI optimization and age-appropriate implant selection over expensive navigation solely to reduce alignment outliers.
This paper also set the stage for kinematic alignment as an alternative philosophy. If neutral mechanical alignment does not reliably improve survival, patient-specific alignment targets become a legitimate next question. The authors themselves note that the 0° ± 3° target remains a reasonable default until better individualized data exist, so do not abandon it. Just do not oversell it.