The original Akagi line is the most reliable: a systematic review of landmarks for rotational alignment of the tibial component in TKA

Knee Surg Sports Traumatol Arthrosc. 2019 Apr;27(4):1018-1027. doi: 10.1007/s00167-018-5131-z. Epub 2018 Sep 10.


Purpose: There is no present consensus on the most reliable anatomical landmarks or axes for tibial rotational alignment in total knee arthroplasty (TKA). The goal was therefore to review the literature and compare accuracy and repeatability of different axes for tibial baseplate rotation in TKA.

Methods: Medline and Embase were searched for articles that reported accuracy in terms of error or discrepancy from the trans-epicondylar axes (TEA), and/or repeatability in terms of intraclass correlation coefficient, of one or more axes used for tibial baseplate rotation in TKA. Twenty-one articles met criteria, and their data were extracted and tabulated.

Results: The selected articles evaluated 15 different axes, 13 for reliability, 12 for repeatability. The lowest errors or discrepancies from the projected TEA were reported for the original 'Akagi line' (posterior cruciate ligament posteriorly to medial border of tibial tuberosity), its variant using the sulcus of the tibial spines as anterior landmark, as well as the anterior tibial border and the curve-on-curve technique. The best inter-observer repeatabilities were reported for 'Akagi line' variants that use the geometric centre of the tibial plateau posteriorly and the medial border of the tibial tuberosity, or the medial sixth of the patellar tendon anteriorly. Considering accuracy and repeatability simultaneously, only two axes were found to satisfy both criteria consistently: the original 'Akagi line' and the anterior tibial border.

Conclusions: Because of the small number of studies found, the collected evidence remains insufficient to recommend reference axes for intra-operative rotational alignment of the tibial baseplate in TKA. A combination of two or more anatomical landmarks or projected axes could be used to ensure adequate tibial baseplate rotation, while considering individual patient morphology and implant design to optimize knee kinematics and prevent prosthetic overhang.

Level of evidence: Level IV, systematic review of level III and IV studies.

Keywords: Accuracy; Anatomic landmarks; Reference axes; Reliability; Repeatability; Tibial rotation; Total knee arthroplasty.

Publication types

  • Systematic Review

MeSH terms

  • Anatomic Landmarks / diagnostic imaging*
  • Arthroplasty, Replacement, Knee / methods*
  • Humans
  • Knee Joint / diagnostic imaging
  • Knee Joint / surgery*
  • Tibia / diagnostic imaging
  • Tibia / surgery