The Archives of Bone and Joint Surgery

The Archives of Bone and Joint Surgery

Predicting Femoral Component Rotation in Mechanically Aligned Total Knee Arthroplasty: Can Preoperative Three-Joint Alignment Radiograph Help?

Document Type : RESEARCH PAPER

Authors
Mohammad Ayati Firoozabadi
Omid Salkhori
Mohammadreza Razzaghof
Mohammed Kirmasha
SM Javad Mortazavi
Joint Reconstruction Research Center, Tehran University of Medical Sciences, Tehran, Iran -Department of Orthopedic Surgery, Imam Khomeini Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran
10.22038/abjs.2025.83023.3781
Abstract
Objectives: Achieving precise femoral component external rotation (FCER) is crucial in Total Knee Arthroplasty (TKA) to prevent patellofemoral maltracking, implant loosening, pain, and wear. While CT scans and MRIs help determine the rotational profile of the distal femur, their use is limited by concerns about radiation exposure and cost. This study aims to explore the potential role of a preoperative three-joint alignment radiograph in predicting the necessary FCER for mechanically aligned TKA.
Methods: This retrospective cohort study was conducted on 922 patients (1,208 knees) with varus deformity who underwent primary TKA performed by a single knee surgeon between 2018 and 2020. The angular parameters from the three-joint alignment radiograph and FCER were extracted from the JRRC Knee Registry. These angular parameters included the lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), joint line congruency angle (JLCA), and varus angle (VA). FCER was determined intraoperatively based on standard anatomical criteria, including Whiteside’s line, the trans-epicondylar line, posterior condylar axis, anteroposterior axis, and the assessment of the proximal tibial cut. Data analysis was performed using SPSS 26.
Results: A total of 922 patients (57.9% female, 42.1% male) with a mean age of 65.39 ± 8.03 years (range: 43-90) were included in the study. The FCER was 0° in 0.33%, 3° in 83.6%, 5° in 15.23%, and 7° in 0.82% of patients. FCER showed no correlation with MPTA, LDFA, or VA, but it was significantly correlated with JLCA/LDFA, JLCA/MPTA, and JLCA/VA, with cut-offs at 0.11, 0.12, and 0.62, respectively. JLCA/MPTA emerged as the best predictor for FCER in TKA (sensitivity = 48%, specificity = 81%, and accuracy = 0.67).
Conclusion: Preoperative three-joint alignment radiographs can guide the surgeon in determining the required FCER during TKA. If the ratios exceed the established cut-offs, an FCER greater than 3° may be necessary.
        Level of evidence: III
Keywords
Alignment view
Femoral component external rotation
Mechanical strategy
Total knee arthroplasty
Subjects
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The Archives of Bone and Joint Surgery
Volume 13, Issue 12
December 2025
Pages 831-838

  • Receive Date 13 October 2024
  • Revise Date 14 January 2025
  • Accept Date 22 January 2025