New trochlea - old patella. Do both fit together?

Abstract

Aims and Objectives: Trochlear dysplasia has been established as the most common and impactful predisposing factor of lateral patellar dislocation (LPD). In addition, a clear correlation between trochlear dysplasia and the development of cartilage defects and osteoarthritis in the patellofemoral joint has been established. Though current literature increasingly supports trochleoplasty procedures for the treatment of LPD only few data evaluated the actual improvements of the cartilaginous patella-trochlea congruence after deepening trochleoplasty procedure. The aim of this study was therefore to evaluate the patella-trochlea congruence before and after a deepening trochleaplasty and medial patellofemoral ligament (MPFL) reconstruction in severe trochlear dysplasia. The hypothesis was that the deepening trochleoplasty and MPFL reconstruction is able to correct patella-trochlea congruence to physiological parameters. Materials and Methods: The study group comprised 20 patients. All patients suffered recurrent LPD due to severe trochlear dysplasia and underwent a deepening ‘Bereiter’ trochleoplasty and MPFL reconstruction. Pre- and postoperative magnetic resonance imaging (MRI) investigations were used to assess the patella-trochlea contact ratio, the posterior patellar edge - trochlea groove ratio, and the lateral patellar inclination angle (patellar tilt). Measurements were obtained using open-source PACS workstation software (OsiriX v. 5.8.5, Pixmeo SARL, CH1233 Bernex, Switzerland). All parameters were compared to a control group of 20 at random selected patients without any medical history related to the patellofemoral joint. A paired two-tailed t-test was used to test for differences between the pre- and postoperative measurements within the study group. A one-way analysis of variance (ANOVA) with Bonferoni post-test adjustment was used to test for differences between all measurement series. The level of significance was set at 0.05. Results: Preoperatively, all parameters of the study group were significantly different when compared to the control group. This meant a reduced patella-trochlea contact ratio (0.38 ± 0.13 vs. 0.67 ± 0.09; p<0.001), an increased patellar lateralization (0.81 ± 0.10 vs. 0.98 ± 0.03; p<0.001), and increased patellar tilt (27.1° ± 7.7° vs. 9.4° ± 5.7°; p<0.001). Postoperatively, all parameters showed a significant improvement. The patella-trochlea contact ratio increased to a mean of 0.65 ± 0.11 (p<0.0001), patellar lateralization improved to a mean posterior patellar edge - trochlea groove ratio of 0.94 ± 0.06 (<0.0001), and patellar tilt reduced to a mean of 15.05° ± 4.2° (p< 0.0001). All parameters reached normal values when compared to the control group (all p >0.05). Conclusion: Findings of this study indicate that in severe trochlear dysplasia deepening trochleoplasty and MPFL reconstruction is able to correct patellar alignment und patellar-trochlear congruence to normal values.