Elucidate the quantitative early diagnostic indicators of mild chondromalacia patella: ratios of trochlear sulcus angle to patellar and trochlear widths.

Background: Chondromalacia patella (CMP) is often exacerbated by anatomical variations in patellofemoral engagement, and there are currently no sensitivity early diagnostic indicators for mild CMP. This study focused on the relationship between normal patellofemoral joint parameters and mild CMP, aiming to provide a more accurate scientific basis for the early diagnosis and treatment of CMP by studying new quantitative ratios as early diagnostic indicators. Methods: The study involved 100 patients with mild CMP (modified Noyes grade 1 and 2A) and 100 healthy volunteers (controls) who underwent imaging from 1/4/2023 to 1/4/2024. Magnetic resonance imaging and T2 mapping were performed to measure the trochlear sulcus angle (TSA), lateral trochlear inclination (LTI), trochlear depth (TD), trochlear width (TW), patellar width (PW), trochlear length(TL), patellar length(PL), patella-patellar tendon angle(P-PTA), and quadriceps-patellar tendon angle(Q-PA). Differences in demographics and all measurements between the mild CMP group and the control group were detected. Novel composite ratios integrating trochlear morphology and patellofemoral engagement were established for mild CMP diagnosis. Univariate and multivariate logistic regression (adjusted for sex, age, side, height, weight, BMI) identified significant predictors. Receiver operating characteristic (ROC) curve of the participants was analyzed to describe the accuracy of each diagnostic test using the area under the curve (AUC). The ability of TSA, LTI, TD, and six different ratios to predict mild CMP was evaluated by calculating the odds ratio (OR), sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for each measurement. Results: There was no significant difference in demographic characteristics between the two groups. Patients with mild CMP exhibited notable alterations in trochlear morphology and patellofemoral engagement parameters compared with controls. Among the evaluated imaging indicators, the composite ratios integrating trochlear sulcus angle with patellar and trochlear morphology demonstrated superior performance for the early identification of mild CMP. After adjustment for demographic variables, the ratio of trochlear sulcus angle to trochlear width (TSA/TW) remained the most robust independent diagnostic factor. Furthermore, ROC analysis demonstrated that TSA/TW provided the highest diagnostic accuracy and outperformed traditional imaging thresholds and other composite ratios in distinguishing mild CMP. Conclusion: The composite ratio TSA/TW is a potent independent early diagnostic factor of mild CMP, demonstrating superior diagnostic accuracy over traditional methods This ratio-based approach shows significant potential to improve early diagnosis of patellofemoral degeneration.