ABSTRACT
Objective To identify related anatomical parameters and the strongest risk predictor leading to patients with recurrent patellar instability.Methods 52 young patients with recurrent patellar instability that failed of conservative treatment were retrospec-tively evaluated by MRI.Measurements included parameters of patellar tracking,which was characterized by bisect offset index (BSO),trochlear congruence angle (CA)and patellar lateral tilt (PTA),and anatomical parameters of patellofemoral joint,which were characterized by the sulcus angle (SA),lateral trochlear inclination (LTI),trochlear facet asymmetry,trochlear depth,Insall-Salvati Ratio (ISR),Caton-Deschamps index (C-D)and tibial tuberosity-trochlear groove (TT-TG)distance.The collection data were analyzed including the Pearson's correlation and multiple stepwise regression analysis.Results The patellofemoral joint ma-lalignment was significantly correlated with LTI,TT-TG distance and ISR,but not or partly with the trochlear depth,SA,trochlear facet asymmetry and C-D.Linear regression models including LTI,TT-TG distance and ISR explained 0.58,0.47 and 0.43 of the va-riance in BSO,CA and PTA,respectively (P<0.001).And the standardized beta coefficient was largest for LTI,then were TT-TG distance and ISR.Conclusion At full extension of the knee,anatomical related factors measured on MRI explain some degree of re-current lateral patella shift and tilt,the strongest predictor among anatomical related factors that could lead to maltracking is LTI, and then are TT-TG distance and ISR.