Measurement And Significance Of The Lateral Of The Lateral Declination Angle Of Patellar Tendon Based On Knee CT

Objective: To measure the lateral declination angle of the patellar tendon based on knee CT axial images,to verify the repeatability of the measurement,and to explore its significance in the diagnosis and treatment of recurrent patellar dislocation.Methods: A retrospective study was conducted on 508 knee patients hospitalized in our department from January 2017 to December 2021.After 377 patients were excluded by the exclusion criteria,a total of 131 patients participated in this study.Among them,72 patients with recurrent patellar dislocation were divided into group A according to TT-TG≥20mm,33 patients were divided into group B,and 39 patients with TT-TG<20mm were divided into group B;59 patients without patellar dislocation belonged to group C.The lateral declination angle of the patellar tendon,tibial tubercle-trochlea groove(TT-TG),tibial plateau width,and tibial tubercle-trochlea groove perpendicular distance(TT-TE)were measured.The differences of lateral declination angle of the patellar tendon and TT-TG values in groups A,B and C were analyzed.Comparing the measurement times of the two measurement methods.The correlation between the lateral declination angle of the patellar tendon and the TT-TG value was analyzed,and the correlation between the two with the width of the tibial plateau and TT-TE was analyzed.The intraclass correlation coefficient(ICC)was used to analyze the inter-and intra-observer consistency of the lateral declination angle of the patellar tendon and TT-TG values in groups A,B,and C,respectively;according to the Dejour femoral trochlear classification,to compare ICC of lateral declination angle of the patellar tendon and TT-TG value in different femoral trochlear deformities.The value of lateral declination angle of the patellar tendon and TT-TG value in diagnosing recurrent patellar dislocation was analyzed by receiver operating characteristic(ROC)and area under the curve(AUC),and the Youden index was used to calculate the cutoff value,sensitivity and specificity for diagnosis.Based on TT-TG ≥ 20 mm as the reference standard for tibial tuberosity medial displacement osteotomy,the value of patellar tendon lateral deviation as a reference index for tibial tuberosity medial displacement osteotomy was analyzed,and its cut-off value,sensitivity and specificity were calculated.Results: The lateral declination angle of the patellar tendon and TT-TG values were statistically significant between the groups A,B and C(P<0.05).The lateral declination angle of the patellar tendon and TT-TG value were strongly positively correlated(correlation coefficient r=0.720);and lateral declination angle of the patellar tendon was weakly or not correlated with tibial tubercle width and TT-TE(r<0.1),while TT-TG value was weakly correlated with tibial plateau width and TT-TE(0.1<r<0.3).The lateral declination angle of the patellar tendon had excellent interobserver and intraobserver agreement(ICC>0.90)in groups A,B and C;TT-TG values in group A were consistent between observers and intraobservers The mean difference(ICC<0.75)was good in group B(0.75<ICC<0.90),the intra-observer agreement in group C was excellent,and the inter-observer agreement was good.The lateral declination angle of the patellar tendon was excellent in repeatability(ICC > 0.90)in normal trochlear and Dejour types A,B,C,and D trochleas,while TT-TG values were measured in patients with type A and D dysplasia repeatability was good(ICC >0.75),Moderate reproducibility for type B dysplasia(ICC < 0.75).Lateral declination angle of the patellar tendon has a high diagnostic value for recurrent patellar dislocation(AUC=0.917),with a cutoff value of 13.67° and a sensitivity and specificity of 83.05% and 88.89%,respectively.The diagnostic value of TT-TG value was moderate(AUC=0.828),the cutoff value was 16.25 mm,and the sensitivity and specificity were 76.27% and 79.17%,respectively.The lateral declination angle of the patellar tendon was moderate value as a reference index for tibial tuberosity medial displacement osteotomy(AUC=0.754),the cutoff value was 19.96°,and the sensitivity and specificity were 87.18% and54.55%,respectively.Conclusion: The lateral declination angle of the patellar tendon has high repeatability and is simple to measure,and it can indirectly reflect the lateral deviation of the tibial tubercle.