Comparing Personalization in Knee Replacement: Conventional Intramedullary Instruments Versus Technology-aided Techniques

Introduction: Conventional instruments rely on setting the valgus correction angle on the intramedullary guide to set the coronal plane alignment of the femoral component.Various studies have shown that using a fixed varus-valgus correction angle does not lead to perfect mechanical alignment.Despite that, the results with conventional instruments have not been inferior.Does the fixed valgus correction angle with conventional instrumentation lead to a less personalized correction and alignment than a technology-aided total knee replacement (TKR)?Material and methods: 1,054 computed tomography (CT) scans of 999 patients (944 unilateral and 55 bilateral) undergoing technology-assisted TKR surgery were studied.Anatomical-mechanical angle (AMA) was studied and deviations from the native mechanical lateral distal femoral angle (mLDFA) were simulated for five different situations: fixed 5, 6, and 7 with conventional instruments and perfectly executed mechanical and anatomical alignment.Results: Average AMA was 6.88 0.59 and the range was between 4 and 8.Height (p < 0.0001), gender (p < 0.001), and body mass index (BMI) (p <0.05) were found to be significant variables for AMA.Variables such as age, CPAK classification, and range of motion did not have any significance (p > 0.05).The average deviation from the native alignment was lower with fixed 5 and 6 with conventional instruments compared to others (fixed 7 with conventional instruments or technology-aided (perfectly executed) mechanical or anatomical alignment), but it did not reach statistical significance.Conclusion: Using a fixed angle for correction with conventional instruments has a lower deviation from the native alignment and is no less personalized than a technology-aided TKR.