Posterior tibial slope on preoperative CT scans of patients undergoing UKA

Abstract

<p>Introduction: This study measures the medial posterior tibial slope (MPTS) and lateral posterior tibial slope (LPTS) of patients who underwent UKA using their pre-operative CT scans. The differences between measurements using the tibia anatomical and mechanical axes as references are compared.<br>Methods: Preoperative CT scans of patients who underwent primary UKA were collected from the local hospital in Hong Kong. Standardised measurement approaches were developed to obtain the MPTS and LPTS of the tibia plateau through both the anatomical and mechanical axes. CT scans were viewed and measured using open-source imaging software (Medical Imaging Interaction Toolkit).<br>Results: 20 patients (Female: Mechanical axis le=13:7; Mean age: 70.3±7.2) were included. Mean MPTS and LPTS measured using anatomical axis are 7.8°±4.5 and 7.6°±4.2. Mean LPTS measured using the mechanical axis are 6.2°±3.1 and 6.2°±3.0. The value of the Pearson correlation coefficient between MPTS and LPTS using the tibia anatomical and mechanical axes are r= 0.925 (p<0.001) and r=0.838 (p<0.001), respectively. The mean difference between the anatomical and mechanical axes is (0.1°±1.68).<br>Discussion and Conclusion: Contrary to previous studies conducted using X-ray, this study found that anatomical and mechanical-measured PTS can be equally over or underestimated; whether this is unique to the Chinese population requires further investigation. The effect of standing versus supine positions on the measurement of PTS may also require further investigation. A larger sample size is needed to obtain reliable conclusions.</p>