Clinical Application Of Rotational Malalignment And Dislocation Sign In The Evaluation Of Patients With Patellar Dislocation

PART ONE: CLINICAL APPLICATION OF DISLOCATION SIGN ON KNEE MAGNETIC RESONANCE IMAGING: A NEW PREDICTOR FOR EXCESSIVE FEMORAL ANTEVERSION IN PATIENTS WITH PATELLAR DISLOCATIONObjective: To evaluate the clinical relevance of the newly identified dislocation sign in predicting excessive femoral anteversion in patients with patellar dislocations.Methods: A total of 55 patients with patellar dislocation who underwent surgical treatment between 2016 and 2019 were included in this study.Femoral anteversion,tibial torsion,and the femorotibial index were measured via a CT scan.The dislocation sign on the knee MRI was defined as malalignment between the lateral side of the intercondylar fossa of the femur and the lateral intercondylar eminence of the tibial plateau.Results: A positive dislocation sign was observed in 36 of the 55 patients.Increased femoral anteversion was significantly correlated with the number of frames with a positive dislocation sign(r=0.511,P<0.001).The value of femoral anteversion was significantly greater in the group with a positive dislocation sign(P=0.02).Conclusion: Increased femoral anteversion correlated significantly with a positive dislocation sign on knee MRI.However,tibial torsion did not affect the dislocation sign.A positive dislocation sign is evidence for femoral derotation osteotomy.PART TWO: FEMORALANTEVERSION IS RELATED TO TIBIAL TUBERCLE-TROCHLEAR GROOVE DISTANCE IN PATIENTS WITH PATELLAR DISLOCATIONPurpose: To evaluate the potential relationship between the tubercle-trochlear groove(TT-TG)distance and the femoral anteversion of different segments of the femur in patients with patellar dislocation.Methods: A total of 60 patients with a diagnosis of patellar dislocation were included in our study.Patients with previous knee surgeries,previous fractures or lack of necessary radiological examinations were excluded from our study.The data of CT scan within a week before the surgery was used to measure the TT-TG distance,total anteversion,proximal anteversion,diaphyseal anteversion,distal anteversion,and tibial torsion.All the data were obtained from the PACS workstation.The Pearson correlation analysis was used to confirm the potential relationship between TT-TG distance and femoral anteversion of different segments.The intraclass correlation coefficient(ICC)was performed to evaluate the interobserver reliability of measurements.Results: The TT-TG distance was significantly correlated with the diaphyseal anteversion(r=-0.305,p=0.008)and distal anteversion(r=0.365,p=0.004).The total anteversion was associated with proximal anteversion(r=0.392,p=0.02)and diaphyseal anteversion(r=0.631,p<0.001).The intraclass correlation coefficient showed the measurements of included parameters were presented with excellent agreement.Conclusion: Our study showed that patients with high diaphyseal anteversion and distal anteversion tend to had a higher TT-TG distance but the value of total and proximal femoral anteversion were independent of the value of TT-TG distance.PART THREE: VALIDATING THE ROLE OF TIBIAL TUBERCLE-POSTERIOR CRUCIATE LIGAMENT DISTANCE AND TIBIAL TUBERCLE-TROCHLEAR GROOVE DISTANCE MEASURED BY MRI IN PATIENTS WITH PATELLAR DISLOCATION: A DIAGNOSTIC STUDYPurpose: To(1)compare these parameters between patients with patellar dislocation and healthy individuals on MRI measurements,(2)validate the diagnostic capacity of the tibial tubercle-posterior cruciate ligament(TT-PCL)distance and TT-TG distance,(3)define the pathological threshold values of these parameters for tibial tubercle osteotomy(TTO)indication and(4)compare these values with those of previous studies.Methods: Seventy patients with patellar dislocation and seventy healthy volunteers were identified.The inter-and intraobserver reliability values were determined using Bland-Altman analysis and the ICC.The diagnostic capacity of the parameters was evaluated using receiver operating characteristic(ROC)curves and the area under the ROC curve(AUC).The data of the control group were used to determine the pathological threshold values of the measurements.Logistic regression analysis was performed with these pathological threshold values.Results: Significant differences in the TT-PCL distance(P=0.01)and TT-TG distance(P<0.001)were found between the study group(21.48±3.18 and 12.91±3.80,respectively)and the control group(20.07±2.99 and 8.46±3.16,respectively).Both the TT-PCL distance and TT-TG distance had excellent inter-and intraobserver agreement,with inter-ICCs>0.915 and intra-ICCs>0.932,respectively.However,the TT-TG distance had a higher AUC than did the TT-PCL distance(0.820 vs 0.627).The pathological threshold value of the TT-PCL distance was 24.76 mm.The pathological threshold value of the TT-TG distance was 13.64 mm.Subjects with a TT-TG distance of >13.64 mm had a higher risk for patellar dislocation,with an OR of 14.02(95% CI,4.00-49.08,P<0.001).Conclusion: Both the TT-PCL distance and TT-TG distance can be measured reliably by MRI;however,the TT-TG distance has a better diagnostic capacity than does the TT-PCL distance.TT-TG distance still the gold standard for tibial tubercle position evaluation and TTO procedure indication.