The Three-Dimensional Morphology of the Patellofemoral Joint and the Normal Predicted Value of Tibial Tuberosity-Trochlear Groove Distance In Chinese Population

Abstract

Our objective was to obtain normal patellofemoral measurements so as to provide a reference for prosthetic design. Besides, the absolute values and indices of TT-TG distances are still controversial in clinical application. A better method to enable precise clinical applications is still needed.Methods:78 knees of 78 subjects without knee pathologies were included in this cross-sectional study. A CT scan was obtained from all subjects and three-dimensional knee models were constructed using Mimics and SolidWorks software. We measured and analyzed 19 parameters including TT-TG distance and dimensions and shapes of patella, femur, tibia, and trochlea. LASSO regression was used to predict the normal TT-TG distances.Results:The dimensional indexes, TT-TG distance, and femoral aspect ratio of the males were significantly larger than those of females (all P values <0.05). However, after controlling the bias from age, height, and weight, there were no significant differences in TT-TG distances, PAL, and anterior-posterior dimensions between genders (all P values >0.05). The Pearson correlation coefficients between the AFO and other indexes were consistently below 0.3, indicating a none or weak relationship. Similar results were observed for the SA and the Wiberg index. Using LASSO regression, we obtained four parameters to predict TT-TG distance (R2=0.5612, P<0.01) to achieve the optimal accuracy and convenience. Conclusion:The anterior-posterior dimensions of the females were thicker than those of males for the same medial-lateral dimensions. More attention should be paid to not only gender differences but individual differences, especially the anterior condyle and trochlea. Besides, this study provided a new method of predicting TT-TG distance to enable precise clinical diagnoses and guide the medial transfer of the tibial tuberosity.