Background

Although the prevalence and combined prevalence of pathoanatomic risk factors for lateral patellar dislocation (LPD) and their impact on postoperative outcome scores have been described, there is still limited evidence regarding their influence on patients’ disease-specific quality of life (QOL).

Purpose

The goal of this study was to determine whether and to what degree certain demographic, clinical, and pathoanatomic factors impact subjective disease-specific QOL in patients with LPD.

Methods

A total of 182 consecutive patients (male/female 70/112; mean age 23.6 ± 7.3 years) with a history of LPD were prospectively enrolled in this study. Patient age, body mass index (BMI), number of dislocations, reversed-dynamic patellar apprehension test (ReDPAT), and J-sign severity were assessed. In addition, evaluation of pathoanatomic risk factors included assessment of trochlear dysplasia, tibial tubercle–trochlear groove (TT-TG) distance, tibial tubercle-posterior cruciate ligament (TT-PCL) distance, Caton-Deschamps (CD) index, and valgus/valgus malalignment. The statistical analysis evaluated the relationships among those variables and determined their ability to predict the Banff Patellofemoral Instability Instrument 2.0 (BPII 2.0) as a disease-specific QOL measure. Using Spearman correlation, ANOVA and Fisher’s exact test, all variables with ANOVA p = 0.1 or Spearman's abs (rho) > 0.1 were entered into a multivariate linear model using backwards stepwise selection.

Results

Analysis of the individual variables’ ability to predict BPII 2.0 score values revealed ‘age’, ‘BMI’, ‘ReDPAT’, ‘high grade of trochlear dysplasia’ (Dejour B-D), and ‘high-grade J-Sign’ (Grade II and III) as possible relevant variables (one-way ANOVA (p = 0.1); Spearman’s correlation (abs(rho) > 0.1)). Backward-stepwise multivariate regression analysis yielded a final parsimonious model that included the factors ‘BMI’ and ‘J-Sign (Grade II and III)’ as the most relevant parameters influencing BPII 2.0 score values (adjusted R2 = 0.418; p < 0.001)), with a cutoff value for BMI found at 28 kg/m2 (Tukey test; p=0.01).

Conclusion

The main results of this study indicate that the presence of a high-grade J-sign and an increased BMI contribute significantly to inferior QOL score values in patients with recurrent LPD when evaluated with the BPII 2.0. Because BMI is a modifiable factor, this information might be helpful for the clinical decision-making process.