A customized approach for accurate rotational positioning of the femoral component in total knee arthroplasty

Introduction Rotational alignment of the femoral component is important for a good functional outcome and the long-term success of total knee arthroplasty (TKA).

The objective was to evaluate the effectiveness of a customized approach for accurate rotational positioning of the femoral component in total knee arthroplasty.

Material and methods Outcomes of TKA were comprehensively evaluated in 94 patients with Kellgren – Lawrence grade III–IV osteoarthritis. Femoral component rotation was determined in the first group (n = 46) using visual-manual techniques based on the posterior condylar and surgical supracondylar lines. A goniometer was used in the second group (n = 48) to determine the surgical supracondylar line along the anterior tangent line at the angle measured with computed tomography. Statistical analysis of the data was performed using IBM SPSS 20 Statistics and Statistica 13.3 software packages.

Results Analysis of postoperative data on the angle between the surgical supracondylar and posterior condylar lines in the first group revealed a deviation from the normal values with a median of 3.45° (1.9°; 3.8°), indicating significant external rotation of the femoral component. Internal rotation of the femoral component of the implant was observed in two clinical cases reaching 3.5°, indicating mild to moderate malrotation. The anterior tangent line served as a landmark in the second group, and the mean arithmetic value of the angle between the surgical supracondylar and posterior condylar lines measured 0.9° (0.6°; 1.2°) postoperatively. The measurement suggested the significant line to be used as a promising landmark in primary TKA.

Discussion Ji et al. explored the angle between the surgical supracondylar and anterior tangent lines and performed a comparative analysis of methods based on supracondylar, anterior tangent, and anterior patellar lines. The approach facilitated an objective assessment of the applicability for solving clinical problems and confirmed our analytical data. The authors emphasized the anterior patellar line and suggested its potential for correcting varus deformity of the knee joint. In our series, the knee alignment was not considered and the focus was on the anterior tangent line, which has not been reported in Russian studies.

Conclusion The customized approach for accurate rotational positioning of the femoral component using the FAT line demonstrated its high efficacy in TKA. The approach facilitated accurate component positioning minimizing the risk of errors. The findings suggested that customized navigation techniques can be used in routine clinical practice.

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