T Mapping of Patellar Cartilage After a Single First-Time Episode of Traumatic Lateral Patellar Dislocation.

Background: In most cases, lateral patellar dislocation (LPD) is accompanied by chondral injury and may initiate gradual degeneration of patellar cartilage, which might be detected with a T mapping, a well-established method for cartilage lesions assessment.

Purpose: To examine short-term consequences of single first-time LPD in teenagers by T mapping of the patellar-cartilage state.

Study Type: Prospective.

Population: 95 patients (mean age: 15.1 ± 2.3; male/female: 46/49) with first-time, complete, traumatic LPD and 51 healthy controls (mean age: 14.7 ± 2.2, male/female: 29/22).

Field Strength/sequence: 3.0 T; axial T mapping acquired using a 2D turbo spin-echo sequence.

Assessment: MRI examination was conducted 2-4 months after first LPD. T values were calculated in manually segmented cartilage area via averaging over three middle level slices in six cartilage regions: deep, intermediate, superficial layers, and medial lateral parts.

Statistical Tests: ANOVA analysis with Tukey's multiple comparison test, one-vs.-rest logistic regression analysis. The threshold of significance was set at P < 0.05.

Results: In lateral patellar cartilage, a significant increase in T values was found in deep and intermediate layers in both patient groups with mild (deep: 34.7 vs. 31.3 msec, intermediate: 38.7 vs. 34.6 msec, effect size = 0.55) and severe (34.8 vs. 31.3 msec, 39.1 vs. 34.6 msec, 0.55) LPD consequences as compared to controls. In the medial facet, only severe cartilage damage showed significant prolongation of T times in the deep layer (34.3 vs. 30.7 msec, 0.55). No significant changes in T values were found in the lateral superficial layer (P = 0.99), whereas mild chondromalacia resulted in a significant decrease of T in the medial superficial layer (41.0 vs. 43.8 msec, 0.55).

Data Conclusion: The study revealed substantial difference in T changes after LPD between medial and lateral areas of patellar cartilage.

Evidence Level: 2 TECHNICAL EFFICACY STAGE: 2.