I read with great interest this study regarding the effect of coronal alignment on tibial component migration after TKA.
As orthopedic surgeons, we know that obtaining neutral coronal limb alignment during TKA has traditionally been considered optimal for implant longevity, outcomes and function. Among other studies, we previously published results showing only 70% of individuals had neutral alignment; the obvious question that arises is whether aiming for neutral limb alignment or constitutional limb alignment should be the goal. Some studies show no difference in survivorship between neutrally aligned TKA compared with knees aligned in greater than 3° varus and valgus. Innovatively, this study uses radiostereometric analysis from three studies to evaluate implant migration comparing neutral mechanical limb alignment vs. constitutional alignment after TKA.
The authors conclude that out of range mechanical limb alignment leads to a higher rate of tibial component migration with the highest rate of migration occurring in mechanically varus TKA and no migration seen in mechanically neutral TKA. Although it is difficult to estimate premorbid constitutional alignment, when matching constitutional alignment, this study shows no difference in component migration if placed in mechanical neutral, varus or valgus. Further, although there are limitations to the study, including using only static coronal alignment measurements and lack of correlation between radiostereometric analysis (RSA)-evidenced tibial component migration and clinical symptomatology, previously published evidence has shown that RSA analysis demonstrating excessive tibial component migration is predictive of late aseptic loosening. Thus importantly, when considering preventing late aseptic loosening, this study helps guide surgeons to aim for neutral when using mechanical limb alignment and specifically avoid varus.
Ritesh R. Shah , MD
Chief, Orthopedic Surgery
Advocate Illinois Masonic Medical Center
Illinois Bone and Joint Institute
Des Plaines, Illinois
Disclosures: Shah reports he receives research support from and is a speaker for Microport Orthopedics.