Degeneration of patellar cartilage in patients with recurrent patellar dislocation following conservative treatment: evaluation with delayed gadolinium-enhanced magnetic resonance imaging of cartilage

Objective: To examine the characteristics of cartilage degeneration in patients with recurrent patellar dislocation (RPD) following conservative treatment using delayed gadolinium-enhanced magnetic resonance imaging (MRI) of cartilage (dGEMRIC). Design: This study evaluated three groups of knees: group I, 35 knees from both knees of patients with bilateral RPD and dislocated side knees of patients with unilateral RPD; group II, 15 non-dislocated side knees of patients with unilateral RPD; and group III, 20 knees from both knees of healthy volunteers. Differences in post-contrast T1 [T1(Gd)] of cartilage at both medial and lateral facets between groups I, II and III were analyzed. For group I, possible relationships were evaluated between T1(Gd) of cartilage and patient age, length of time between the initial dislocation and MRI and the total number of dislocations between the initial dislocation and MRI for both medial and lateral facets. Results: The mean T1(Gd) of cartilage at medial facets for groups I, II and III were 411 ± 46 ms, 465 ± 38 ms and 490 ± 29 ms, respectively; there were significant differences between these means (P < 0.05). The mean T1(Gd) of cartilage at lateral facets for groups I, II and III were 426 ± 53 ms, 466 ± 45 ms and 510 ± 36 ms, respectively; there were also significant differences between these means (P < 0.05). Significant correlations were observed between T1(Gd) of cartilage for both medial and lateral facets and length of time between the initial dislocation and MRI (P < 0.05). No other correlations were significant. Conclusion: dGEMRIC may be a useful method to monitor glycosaminoglycan concentration in patients with RPD following conservative treatment.