Injury patterns of medial patellofemoral ligament and correlation analysis with articular cartilage lesions of the lateral femoral condyle after acute lateral patellar dislocation in children and adolescents: An MRI evaluation.

Objectives: The purpose of this study was to investigate the injury characteristics of medial patellofemoral ligament (MPFL), and to analyse the correlations between the injury patterns of MPFL and articular cartilage lesions of the lateral femoral condyle in children and adolescents with acute lateral patellar dislocation (LPD).
Methods: Magnetic resonance (MR) images were prospectively obtained in 127 consecutive children and adolescents with acute LPD. Images were acquired using standardised protocols and these were independently evaluated by two radiologists.
Results: Fifty-four cases of partial MPFL tear and 69 cases of complete MPFL tear were identified. Injuries occurred at an isolated patellar insertion (PAT) in 47 cases, an isolated femoral attachment (FEM) in 41 cases and an isolated mid-substance (MID) in four cases. More than one site of injury to the MPFL (COM) was identified in 31 cases. The prevalence rate of chondral and osteochondral lesions of the lateral femoral condyle were 23.4% (11/47) and 29.8% (14/47) in the PAT subgroup, 7.3% (3/41) and 9.8% (4/41) in the FEM subgroup and 25.8% (8/31) and 32.3% (10/31) in the COM subgroup, respectively. The PAT and COM subgroups showed significantly higher prevalence rate of chondral and osteochondral lesions in the lateral femoral condyle when compared with the FEM subgroup. The prevalence rate of chondral and osteochondral lesions of the lateral femoral condyle were 17.4% (12/69) and 30.4% (21/69) in the complete MPFL tear subgroup and 20.4% (11/54) and 13% (7/54) in the partial MPFL tear subgroup, respectively. The subgroup of the complete MPFL tear showed significantly higher prevalence rate of osteochondral lesions in the lateral femoral condyle when compared with the subgroup of the partial MPFL tear.
Conclusions: Firstly, the MPFL is most easily injured at the PAT, and secondly at the FEM in children and adolescents after acute LPD. The complete MPFL tear is more often concomitant with osteochondral lesions of the lateral femoral condyle than the partial MPFL tear. The isolated patellar-sided MPFL tear and the combined MPFL tear are more easily concomitant with chondral lesions and osteochondral lesions of the lateral femoral condyle than the isolated femoral-sided MPFL tear.
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