Alignment is one of the most important factors affecting the longevity of total knee arthroplasty (TKA) prostheses. Among the many available tools for attaining good alignment are new palm-sized, accelerometer-based navigation systems. In the November 18, 2020 issue of The Journal of Bone & Joint Surgery, Minoda et al. deliver robust evidence from a multicenter randomized controlled trial comparing post-TKA coronal alignment with such a “mini-navigation” system versus results using conventional navigation.
The 90 TKAs analyzed (45 in each group) were performed by 8 different surgeons across 5 hospitals in Japan. The primary outcome was the number of tibial-prosthesis alignment outliers, defined as alignment error of >2° relative to neutral, based on weight-bearing radiographs 6 months after surgery. Researchers also compared absolute differences from neutral alignment for both tibial and femoral components, operative time, and complications.
Relative to conventional navigation, the mini-navigation system reduced the number of outliers in tibial alignment and hip-knee-ankle (HKA) angle. In addition, the absolute differences in the coronal alignment of the femoral and tibial prostheses were less in the mini-navigation group. Researchers found no increase in operative time with the portable navigation system, nor was there any observed increase in perioperative complications compared with conventional navigation.
Conversely, there were no significant between-group differences in postoperative Knee Society scores, but the authors note that “another study design with a longer follow-up period” is needed to evaluate the patient-centered clinical effects of prosthetic alignment using portable navigation. Both the authors and Andrew P. Kurmis, FRACS(Ortho), who commented on the study, assert that the true value of navigation systems (mini and full-sized alike) probably lies in higher reproducibility of tibial-component alignment relative to conventional navigation, regardless of the skill and experience of the surgeon.
