An Observation of Posterior Tibial Slope and Metaphysio-diaphyseal Angle in Indian Population

Abstract

ABSTRACT Introduction The posterior inclination of the tibial plateau relative to the longitudinal axis of tibia is referred to as the posterior tibial slope (PTS). There is paucity of data regarding PTS in Indian population. Metaphysio-diaphyseal angle (MDA) is the angle between longitudinal axis of tibia and proximal tibial metaphysis, a new entity with a possible clinical significance. This study was performed to determine the mean PTS and mean MDA to study the correlation of PTS and MDA changes with osteoarthritic degeneration in Indian population and to assess the sensitivity and specificity of PTS and MDA in detecting osteoarthritis. A descriptive, cross-sectional study design was followed. Materials and methods A total of 173 X-rays with true PA and lateral views were examined from 121 individuals using standardized technique. Osteoarthritis was classified based on Ahlback grading system. Posterior tibial slope was defined as the angle formed by two lines in the lateral knee radiograph. Metaphysio-diaphyseal angle is a new entity defined in this study, formed between two lines—first line is the proximal anatomical axis of the tibia and the second is the axis of the proximal tibial metaphysis. All the observations and measurements of PTS and MDA were statistically analyzed using MedCalc software. Results There were 121 individuals in the study with 91 osteoarthritic knees and 82 normal knees. The mean PTS among normal group is 9.69° [range 5–13° with standard deviation (SD) 1.81] and among arthritic group is 14.05° (range 10–24° with SD 2.38). The mean MDA among normal group is 19.87° (range 15–30° with SD 2.70) and among arthritic group is 25.03° (range 19–34° with SD 3.05). There is a moderate correlation between PTS and MDA (r = 0.64). Sensitivity and specificity in detecting osteoarthritis with PTS is 96.7% and 85.4% and by MDA is 90.1% and 84.7%, respectively. Conclusion Our study finds that native PTS is similar to that of oriental population but higher than that of Caucasians. There is moderate linear correlation between PTS and MDA. They also serve as a marker in detecting osteoarthritis with good sensitivity and specificity. How to cite this article Thirunarayanan V, Ramprasath DR, Amarnath R, et al. An Observation of Posterior Tibial Slope and Metaphysio-diaphyseal Angle in Indian Population. J Orth Joint Surg 2020;2(2):52–56.