Referencing Tibial Plateau with Probe Improves Accuracy of Posterior Slope in Medial Unicompartmental Knee Arthroplasty

There is currently no consensus on intraoperative references for determining the posterior tibial slope (PTS) in medial unicompartmental knee arthroplasty (UKA). The medial tibial plateau could serve as a direct reference for determining the native PTS through the placement of a hook probe in the anteroposterior direction of the medial tibial plateau.

Masao Akagi et al conducted a study to examine the accuracy of this new referencing method. The study has been published in ‘Arthroplasty Today’ journal.

In the study group, a special hook probe was placed in the AP direction on the medial second quarter of the Medial Tibial Plateau (MTP). PTS was determined by setting a gauge inserted into the cutting slot parallel to the probe placed on the MTP.

The authors consecutively performed 55 medial UKAs using the new method (study group), and the preoperative and postoperative PTS on lateral knee radiographs were examined. These outcomes were then compared with those of consecutive 50 medial UKAs performed using the conventional method (control group), which immediately preceded the start of the use of the new method.

Key findings of the study were:

• The correlation coefficient between the preoperative and postoperative PTS of the study group was larger than that of the control group (0.887 and 0.482, respectively).

• The mean implantation error of the PTS in the study group was smaller than that of the control group (-1.10 ± 1.30 and -3.00 ± 3.20, respectively; P < .0001).

• The percentages of knees within 20 of implantation error were 73% and 34% in the study and control groups, respectively (P < .0001).

• The root mean square errors in the study and control groups were 1.70 and 4.30, respectively.

The authors concluded that – “This study indicates that the new referencing method with a hook probe placed on the medial second quarter of the MTP could reduce outliers and improve the accuracy of the PTS of the tibial implant, even for a minimally invasive approach. The accuracy of the postoperative PTS with this method may be comparable to that of the robot-assisted surgery and the conventional method in experienced high-volume surgeons. The hook probe could serve as a direct anatomical reference, indicating the native PTS in medial UKAs. Future midterm and long-term follow-up studies on the clinical results with this new method are needed.”

Further reading:

Referencing the Tibial Plateau With a Probe Improves the Accuracy of the Posterior Slope in Medial Unicompartmental Knee Arthroplasty Masao Akagi, Akihiro Moritake et al Arthroplasty Today 18 (2022) 89-94 https://doi.org/10.1016/j.artd.2022.08.017