PLoS One. 2018; 13(12): e0209317.

A proposed new rotating reference axis for the tibial component after proximal tibial resection in total knee arthroplasty

Takaaki Ohmori, Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Resources, Software, Validation, Visualization, Writing – original draft, Writing – review & editing, Tamon Kabata, Conceptualization, Data curation, Methodology, Project administration, Software, Supervision, Validation,* Yoshitomo Kajino, Conceptualization, Data curation, Software, Supervision, Validation, Daisuke Inoue, Conceptualization, Data curation, Methodology, Validation, Tadashi Taga, Conceptualization, Methodology, Project administration, Validation, Takashi Yamamoto, Conceptualization, Data curation, Methodology, Validation, Tomoharu Takagi, Conceptualization, Data curation, Methodology, Validation, Junya Yoshitani, Conceptualization, Methodology, Software, Validation, Takuro Ueno, Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Validation, Ken Ueoka, Conceptualization, Validation, and Hiroyuki Tsuchiya, Conceptualization, Data curation, Project administration, Supervision, Validation
Knee

Purpose

During total knee arthroplasty, few rotating reference axes can be reliably used after tibial resection. We speculated that a line that passes through the lateral edge of the posterior cruciate ligament (PCL) at its tibial attachment after resection and the most prominent point of the tibial tubercle [after-tibial resection (ATR) line] will provide a good reference axis. In this study, we aimed to evaluate the association between ATR and Akagi’s lines.

Materials and methods

In this case–control simulation study, we retrospectively evaluated 38 patients with varus knee and 28 patients with valgus knee. We defined the reference cutting plane as 10 mm distal from the lateral articular surface of the tibia in varus group and as 7 mm distal from the medial articular surface in the valgus group. We measured angles between Akagi’s line and the ATR line (ATR line angle) as well as between Akagi’s line and 1/3 Akagi’s line (1/3 Akagi’s line angle), which passes through the midpoint of PCL and the medial third of the patellar tendon. We used paired t-tests to determine the significance of differences between these angles, with p < 0.05 indicating statistical significance. Intra- and interclass correlation coefficients for the reproducibility of 1/3 Akagi’s line angle and ATR line angle were analyzed by two surgeons.

Results

We found that 1/3 Akagi’s line angle was 10.2° ± 1.3° in the varus group and 10.9° ± 1.3° in the valgus group (p = 0.017). The ATR line was positioned externally compared with Akagi’s line in all patients. Mean ATR line angles at 0°, 3° and 7° posterior slopes were 6.1° ± 1.9°, 5.8° ± 2.0° and 6.0° ± 1.7° in the varus group and 6.3° ± 2.3°, 6.2° ± 2.3° and 5.4° ± 2.1° in the valgus group, respectively. There were no significant differences in the ATR line angle between the varus and valgus groups. (p = 0.34–0.67) Intra- and interclass correlation coefficients for the reproducibility of 1/3 Akagi’s line angle were 0.936 and 0.986 and those for the reproducibility of ATR line angle were 0.811 and 0.839.

Conclusions

The ATR line was positioned between Akagi’s line and 1/3 Akagi’s line in all patients and was a valid option for evaluating rotational tibial alignment after tibial resection.


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