Navigated total knee arthroplasty: Retrospective study of 600 continuous cases.

INTRODUCTION

Computer-assisted navigation in total knee arthroplasty (TKA) has existed for more than 20 years, although its use has been marginal. Its benefits are still largely debated, especially its efficacy for achieving the desired postoperative alignment.

HYPOTHESIS: A neutral hip-knee-ankle (HKA) angle (180°±3°) will be achieved in at least 85% of cases and there will be no difference between the different types of navigation systems used.

MATERIAL AND

METHODS

In this retrospective, single-center, single-surgeon study, all the TKAs completed between September 2003 and December 2017 were included, giving a total of 753 navigated TKAs: Navitrack group: 196 Natural Knee II implants (Zimmer) with the Navitrack-OS Knee system (Zimmer CAS); Brainlab group: 557 implants (196 Profix, Smith & Nephew and 361 LCS, DePuy) with the Brainlab Vector Vision system. The aim of navigation was independent of the preoperative alignment and was always to achieve a neutral HKA mechanical axis (180°±3°). The primary endpoint was the postoperative HKA angle. This parameter was used to determine whether the navigation objective was achieved, to define how many patients were outliers and to compare navigation systems to each other. The potential influence of sex, body mass index (BMI) and preoperative deformity were secondary aims. Lastly, the final navigation values were compared to radiological data to detect any potential deviations.

RESULTS

We analyzed 600 of the cases, 160 in the Navitrack group and 440 in the Brainlab group (152 Profix and 288 LCS). A neutral HKA angle was found in 91% patients: 93% for the Navitrack group and 90% in the Brainlab group (90.8% Profix and 89.6% LCS). There was no significant difference between groups (p=0.68), nor between subgroups (p=0.85). An elevated BMI negatively influenced the ability to achieve a neutral HKA (p=0.015), regardless of the system used.

CONCLUSION

In our study of 600 TKA cases done with navigation, the postoperative alignment goal (HKA 180°±3°) was achieved in 91% of cases. There was no difference between navigation systems. Patients with a high BMI were more likely to be outliers (p=0.015).

LEVEL OF EVIDENCE: IV.