Efficacy Evaluation Of High Field Strength MRI On Biomechanical Indexes Of Patellofemoral Instability

ObjectiveThis study measured and compared the differences of various relevant indicators between patients with patellofemoral instability and healthy volunteers in response to abnormal biomechanical changes in the patellofemoral joint through high-field MRI,and compared the diagnostic efficacy of each individual index and the combination of indexes and evaluated them.Materials and MethodsThe MRI data of 93 patients with patellofemoral instability in the affected side of the knee treated by the surgery department of our hospital from October 2021 to September 2022 were analyzed and included in the case group,including patellofemoral instability caused by patellar dislocation,subluxation and medial patellar retinaculum injury.Cases with multiple ligament injuries of the knee joint,fractures around the knee joint,massive joint effusion and previous knee surgery were excluded.MRI data of 50 healthy volunteers(100 knees)in the same period were selected as the control group.Two senior imaging physicians a and b measured the values of the tibial tuberosity-trochlear groove(TTTG),patellar height(PH),sulcus lateral facet ratio(SLFR)and patellar translation(PT)in the two groups.The measurement consistency between two imaging physicians a and b was evaluated by the intraclass correlation coefficient(ICC),and 30 case group images were randomly selected to evaluate the measurement consistency between imaging physician a and imaging physician b.Conduct independent sample t test or Mann-Whitney U test for each index measured in the case group and the control group to observe whether the difference between the two groups is significant.The area under the curve(AUC)for the diagnosis of patellofemoral instability was observed by using the receiver operating characteristic curve(ROC),and the maximum Youden index was taken as the cut-off value to compare its sensitivity and specificity.The indexes with statistical significance between the two groups were analyzed by multi-factor binary logistic regression analysis,so as to establish the joint prediction equation of the relevant indexes.The ROC curve was used to observe the area under the curve of the joint index prediction equation to diagnose the patellofemoral joint instability,and the maximum Youden index was taken as the cut-off value to compare the sensitivity and specificity.Results1.The ICC between imaging physicians a and b was good.The ICC values of TTTG,ISR,SLFR and PT were 0.836,0.965,0.912 and 0.925,severally.2.TTTG,ISR,SLFR and PT in the case group were 15.98±2.78mm,1.39±0.14,0.45±0.11 and 4.08±0.76 mm severally,the TTTG,ISR,SLFR and PT of the control group were 13.54±2.28 mm,1.35±0.15,0.63±0.13 and 3.03±0.74 mm severally.There were significant differences between the case group and the control group in TTTG,ISR,SLFR and PT,p<0.05.3.In single-factor analysis,the AUC,sensitivity,specificity and cut-off values of TTTG were 0.752,63.4%,79.0%and 15.200 mm severally,the AUC,sensitivity,specificity and cut-off values of ISR were 0.586,79.6%,36.0%and 1.280 severally,the AUC,sensitivity,specificity and cut-off values of SLFR were 0.870,82.0%,80.6%and 0.530 severally,and the AUC,sensitivity,specificity and cut-off values of PT were 0.831,76.3%,74.0%and 3.490 mm severally.4.Multivariate binary logistic regression analysis showed that TTTG,ISR,SLFR and PT were statistically correlated with patellofemoral instability(P<0.05).When TTTG+SLFR+PT were combined,their regression coefficients were 0.356,-12.226 and 1.754 severally.The joint index regression equation established by this method was Y=-5.031+0.356 X TTTG-12.226 X SLFR+1.754×PT,where TTTG was in mm and PT was in mm.When TTTG+ISR+SLFR+PT were combined,their regression coefficients were 0.416,4.365,-12.591 and 1.951 severally.The joint index regression equation established was Y=-12.349+0.416×TTTG+4.365×ISR-12.591×SLFR+1.951×PT,where TTTG was in mm and PT was in mm.5.The AUC of the joint prediction equation of TTTG+SLFR+PT was 0.944,the sensitivity was 88.2%,the specificity was 91.0%,and the cut-off value was 0.533.The AUC of the joint prediction equation of TTTG+ISR+SLFR+PT was 0.950,the sensitivity was 90.3%,the specificity was 88.0%,and the cut-off value was 0.449.Conclusions1.Compared with healthy people,TTTG,ISR,SLFR and PT of patients with patellofemoral instability have statistical differences.2.Patients with patellofemoral instability showed TTTG increase,ISR increase,SLFR decrease and PT increase.3.The diagnostic efficacy of the TTTG+SLFR+PT joint prediction equation and the TTTG+ISR+SLFR+PT joint prediction equation are better than that of each index alone,and the diagnostic efficacy of the TTTG+ISR+SLFR+PT joint prediction equation is better.