An artificial intelligence based on a convolutional neural network allows a precise analysis of the alignment of the lower limb

Int Orthop. 2023 Feb;47(2):511-518. doi: 10.1007/s00264-022-05634-4. Epub 2022 Nov 23.


Purpose: The objective of this study was to develop a numeric tool to automate the analysis of deformity from lower limb telemetry and assess its accuracy. Our hypothesis was that artificial intelligence (AI) algorithm would be able to determine mechanical and anatomical angles to within 1°.

Methods: After institutional review board approval, 1175 anonymized patient telemetries were extracted from a database of more than ten thousand telemetries. From this selection, 31 packs of telemetries were composed and sent to 11 orthopaedic surgeons for analysis. Each surgeon had to identify on the telemetries fourteen landmarks allowing determination of the following four angles: hip-knee-ankle angle (HKA), medial proximal tibial angle (MPTA), lateral distal femoral angle (LDFA), and joint line convergence angle (JLCA). An algorithm based on a machine learning process was trained on our database to automatically determine angles. The reliability of the algorithm was evaluated by calculating the difference of determination precision between the surgeons and the algorithm.

Results: The analysis time for obtaining 28 points and 8 angles per image was 48 ± 12 s for the algorithm. The average difference between the angles measured by the surgeons and the algorithm was around 1.9° for all the angles of interest: 1.3° for HKA, 1.6° for MPTA, 2.1° for LDFA, and 2.4° for JLCA. Intraclass correlation was greater than 95% for all angles.

Conclusion: The algorithm showed high accuracy for automated angle measurement, allowing the estimation of limb frontal alignment to the nearest degree.

Keywords: Artificial intelligence; Convolutional neural network; Lower limb.

MeSH terms

  • Artificial Intelligence
  • Humans
  • Knee Joint / diagnostic imaging
  • Knee Joint / surgery
  • Lower Extremity / surgery
  • Neural Networks, Computer
  • Osteoarthritis, Knee* / surgery
  • Reproducibility of Results
  • Retrospective Studies
  • Tibia* / surgery