Related Experiment Video
Updated: May 8, 2025
Four-Dimensional CT Analysis Using Sequential 3D-3D Registration
Published on: November 23, 2019
Comparing supine CT scanogram and standing long-leg radiograph for postoperative alignment in total knee
Vikram Arun Mhaskar1,2, Rachit Saggar3, Satyabrat Karan4
1Sitaram Bhartia Institute of Science and Research, New Delhi, India. drvikrammhaskar@gmail.com.
Purpose:
Achieving precise postoperative alignment is critical for the long-term success of total knee arthroplasty (TKA). Long-leg standing radiograph (LLR) at 6 weeks post-op is the gold standard for assessing alignment, but its reliance on weight-bearing and positioning makes it less practical in the early postoperative period. Supine computed tomography scanogram (CTS) offers a potential alternative. This study compares CTS and LLR in patients undergoing TKA with patient-specific valgus correction angles (VCA).
Methods:
A prospective study of 108 knees from 57 patients undergoing primary TKA was conducted. CTS was performed on postoperative day three in a supine non-weight-bearing position, and LLR at six weeks in an upright standing position. Coronal alignment was assessed using hip-knee-ankle angle (HKA) and compared using Bland-Altman plots, paired-samples t-tests, and Cohen's d.
Results:
CTS showed 57% of knees were within 3° of neutral alignment, while LLR showed 61%. The mean difference between modalities was 0.52° (SD, 3.56°; p = 0.07). Inter-observer reliability was excellent for both CTS and LLR (all ICCs > 0.9).
Conclusion:
While CTS provides a useful alternative for early postoperative alignment assessment-particularly in situations where a standing LLR is not feasible-the observed variability suggests that LLR remains the more reliable modality when precise alignment is critical. Surgeons should therefore consider CTS as an adjunct tool for early decision-making or non-ambulatory patients in the immediate postoperative setting.
Level Of Evidence:
Level II, Prospective Comparative Study.
